In 1984, Casscells stated "Diagnostic arthroscopy and, perhapseven more important, arthroscopic surgery constitute what isprobably the outstanding achievement in orthopedic surgeryin the past decade" (Casscells 1984). While the author of thisstatement would probably admit to being biased, it is afair reflection on the success and acceptance of the role ofarthroscopy in human orthopedics. Although generallyconsidered a modern surgical procedure, the technique tookconsiderable time to develop. The first endoscopic examin-ation of a knee joint was performed in 1918 by Professor Takagiat the University of Tokyo (Takagi 1933). Later the techniquewas pioneered in the United States by Burman and colleagues(Burman 1930, Burmanet aI1934). The first practical arthro-scope was developed by Watanabe (a pupil of Takagi) in 1960(Watanabe 1960), and he also developed some basic principlesfor arthroscopy of the knee. In 1965, his techniques werebrought to North American by Robert Jackson of Toronto(Jackson 1987).

In the early 1970s, the arthroscope began to achieve realclinical use (Casscells 1971, Jackson & Dandy 1972), and thefirst course in arthroscopy of the human knee in the UnitedStates was given in 1973. The procedure of diagnosticarthroscopy initially met with considerable skepticism withincircles of human orthopedic specialists until its value wasdemonstrated in the total evaluation of the knee (Dandy &Jackson 1975, Watanabe et a11978, Casscells 1980). There-after, arthroscopy became firmly established as a diagnostictool in human orthopedic practice, and these early days havebeen the subject of reviews by Casscells (1987) and Jackson(1987); the interested reader is referred to these sources formore information.

In the middle of the 1970s, arthroscopy moved into thesecond phase of its development, with the realization of thepotential to perform surgery under arthroscopic visualization(O'Connor 1974, 1977, Dandy 1981, Jackson 1983). Thedevelopment of appropriate techniques and suitable instru-mentation followed (Johnson 1977, O'Connor 1977, Dandy1981). It also became apparent that the therapeutic advan-tages of arthroscopy included not only the surgical proceduresper se (which can be grouped under the heading of surgicalarthroscopy or arthroscopic surgery) but also the benefitsfrom joint lavage and lysis of adhesions (Jackson 1974,O'Connor 1974). The advantages were low morbidity, earlypostoperative movement and reduced hospitalization times.

Impressive advances then occurred in both technologyand technique. The first arthroscopic surgery was meniscectomyin humans, followed by procedures such as patellofemoralmalalignment, abrasion arthroplasty, shaving for chondro-malacia, and synovectomy. The advantages of arthroscopicmeniscectomy have been well documented and arthrotomy isnow a rarity (Pettrone 1982, McGinty 1987). The manage-ment of conditions involving the meniscus is also a goodexample of how new concepts have evolved from the increaseddiagnostic accuracy afforded by arthroscopy and the potentialto re-examine a knee with minimal morbidity Gackson 1986).The most important of these new concepts was probably thepreservation of meniscal tissue, which led to the technique ofpartial meniscectomy and then to initial arthroscopic repair(Keene et al 1987). The development of more complexprocedures followed and cruciate repairs are now performedarthroscopically (Shrock & Jackson 1996). The use ofarthroscopy in man now encompasses the shoulder, elbow,wrist, digital, ankle, hip, and temporomandibular jointsG ohnson 1986). It is the most common orthopedic procedureperformed today; current estimates cite approximately 9000orthopedic surgeons performing arthroscopy in the UnitedStates alone (McGinty 1987).

Arthroscopy in the horse has gone through a similarevolution. In 1949, the human pioneer Watanabe reportedarthroscopy of the equine hock. Large animal arthroscopywas first presented in the German literature in 1973(Knezevic pers com 1984) and appeared in the Englishlanguage in 1975 and 1977 (Smith 1975, Knezevic& Wruhs1977). Diagnostic arthroscopy of the equine carpus was firstreported in 1974 (Hall & Keeran 1975), but was describedmore extensively by McIlwraith & Fessler in 1978. Reports ofits use in other joints followed and diagnostic arthroscopy ofthe equine stifle joint was reported in 1982 (Nickels & Sande

1982).As in human orthopedics, use of the arthroscope in horses

extended into surgical practice as technology and techniquesof triangulation developed. Some surgical manipulationsunder arthroscopic visualization in the horse were mentionedby Knezevic & Wruhs in 1977, but arthrotomy remained theaccepted means of completing surgery. The first description ofequine arthroscopic surgery involved the carpus (Ommert1981, Valdez et al1983) and further descriptions involvedthe carpal, fetlock, tarsocrural, and femoropatellar joints

198J). Uescriptions of diagnostic and surgical arthroscopicprocedures in the carpal, fetlock. tarsocrural and femoro-patellar joints were detailed in textbook form in 1984(McIlwraith 1984b). At that time, the first author usedarthroscopic surgery as the routine method of joint surgeryfor virtually all conditions, with the exception of subchondralcystic lesions of the medial condyle of the femur. some carpalslab fractures. and fractures of the proximal sesamoid bones.Arthroscopic techniques were subsequently developed anddescribed in the second edition of the book in 1990(McIlwraith 1990a). The use of arthroscopic surgery in thetreatment of third carpal slab fractures was reported byRichardson in 1986; its use in the treatment of subchondralcystic lesions in the medial condyle of the femur was docu-mented originally by Lewis in 1987. Techniques for diagnosticand surgical arthroscopy of the shoulder were described in1987 (Bertone & McIlwraith 1987. Bertone et al 1987.Nixon 1987). At the time of the second edition, arthroscopyhad also been performed in the distal interphalangeal.proximal interphalangeal, and elbow joints. Arthroscopeshad also been used in the sinuses and tendon sheaths(McIlwraith 1990a).

By 1990, arthroscopy in the horse had gone from being adiagnostic technique used by a few veterinarians to theaccepted way of performing joint surgery. Prospective andretrospective data substantiated the value of the technique inthe treatment of carpal chip fractures (McIlwraith et al19 8 7).fragmentation of the dorsal margin of the proximal phalanx(Yovich & McIlwraith 1986). carpal slab fractures (Richardson1986), osteochondritis dissecans of the femoropatellar joint(Martin & McIlwraith 1985a, McIlwraith & Martin 1985),osteochondritis dissecans of the shoulder (Bertone et alI987).and subchondral cystic lesions of the femur (Lewis 1987).During this period. the use of diagnostic arthroscopy led tothe recognition of previously undescribed articular lesions,many of which are now also treated using arthroscopictechniques.

Since 1990. there has been further sophistication oftechniques: new ones have been developed and treatmentprinciples have been changed based on new pathobiologicknowledge and further prospective and retrospective studiesdefining the success of various procedures. Many of theserecent advances have been recorded in a recent publication(McIlwraith 2002a). For example. there has been furtherdocumentation of success rates following arthroscopicremoval of fragments from the dorsoproximal margin of theproximal phalanx (Kawcak & McIlwraith 1994, Colon et al2000). Advances in understanding the pathogenesis ofosteochondral disease and fragmentation in the carpus andfetlock have also been reported (Kawcak et al 2000. 2001).which naturally led to progress in diagnosis and treatment.Parameters for the surgical treatment of joint injury havebeen carefully defined (McIlwraith & Bramlage 1996).Arthroscopic treatment of fractures in the previously con-sidered inaccessible palmar aspect of the carpus has beendescribed (Wilke et al 2001) together with arthroscopy ofthe palmar aspect of the distal interphalangeal joint

also led to understanding of the contribution of soft tissuelesions to joint disease. In the carpus, tearing of the medialpalmar intercarpal ligament was first reported by Mcllwraithin 1992 and its implications discussed by Phillips & Wright(1994) and Whitton et al (1997a,b,c).

In the fetlock joints, success rates following arthroscopicremoval of osteochondral fragments of the palmar/plantaraspect of the proximal phalanx have now been documented(Foerner et al 1987, Fortier et al 1995), and results forarthroscopic treatment of osteochondritis dissecans of thedistal dorsal aspect of the third metacarpal/metatarsal boneshave been reported (Mcllwraith & Vorhees 1990). Results ofarthroscopic surgery to treat apical (Southwood & Mcllwraithunpublished data), abaxial (Southwood et al 1998a), andbasilar (Southwood & Mcllwraith 2000) fragments of thesesamoid bones are also available in the literature.

Since the last edition, the results of arthroscopic surgeryfor the treatment of osteochondritis dissecans in the tarso-crural joint have been documented (Mcllwraith et al1991)and the arthroscopic approach and intra-articular anatomyof the plantar pouch of the joint have also been described(Zamos et aI1994).

Considerable advances have been made in arthroscopicsurgery of the stille joints. The results of arthroscopic surgeryfor the treatment of osteochondritis dissecans of the femoro-patellar joint have been reported by Foland et al (1992). Thesyndrome of fragmentation of the distal apex of the patellawas recognized and its treatment reported (Mcllwraith1992). The use of arthroscopic surgery for treating certainpatellar fractures was discussed in the previous editionand has since been reported in the literature (Marble &Sullins 2000).

In the femorotibial joints, the use of arthroscopic surgeryto treat subchondral cystic lesions of the medial condyle ofthe femur (Howard et al19 9 5) and proximal tibia (Textor et al2001) have been reported. Cartilage lesions of the medialfemoral condyle have also been described (Schneider et al1997). Arthroscopy has allowed great advances in the recog-nition and treatment of meniscal tears and cruciate injuries(Walmsley 1995, 2002; Walmsleyet al2003). It has also beenused to remove fragments from the intercondylar eminence ofthe tibia (Mueller et al1994) and allow internal fixation ofanother case of intercondylar eminence fracture (Walmsley1997). Techniques have also been developed for diagnostic andsurgical arthroscopy of the caudal pouches of the femorotibialjoints (Stick et al 1992, Hance et al 1993, Trumble et al1994). In addition, a single cranial arthroscopic approach toall three joint compartments has been developed by Boening(1995) and further reported by Peroni & Stick (2002).

Diagnostic and surgical arthroscopy of the coxofemoraljoint has been described (Nixon 1994, Honnas et al1993),lesions identified and surgical treatments performed. The useof the arthroscope is also no longer confined to the limbs, andthe anatomy of the temporomandibular joint has beendescribed recently (Weller et aI2002).

The use of arthroscopy in assisting repair with internalfixation of articular fractures has become routine. This

previously possible. With the availability of such an atraumatic technique. numerous lesions and "new" con-ditions that are not detected radiographically can be

recognized.2. All types of surgical manipulations can be performed

through stab incisions under arthroscopic visualization.The use of this form of surgery is less traumatic, lesspainful, and provides immense cosmetic and functionaladvantages. Surgical intervention is now possible insituations where it would not have been attemptedpreviously. The decreased convalescence time with earlierreturn to work and improved performance is a significantadvance in the management of equine joint problems. Theneed for palliative therapies is decreased, as is the numberof permanently compromised joints.

The initial optimism and advantages of arthroscopy inequine orthopedic practice suggested in the first two editionsof this book have been substantiated. It is now accepted thatequine arthroscopic surgery has revolutionized equine ortho-pedics. Problems have and will continue to be encountered,but we know now that many are avoidable. Although thetechnique appears uncomplicated and attractive to theinexperienced surgeon, some natural dexterity, good three-dimensional anatomical knowledge, and considerable practiceare required for the technique to be performed optimally.Experience and good case selection are of paramountimportance and reiterating a passage from the first edition ofthis book remains as pertinent today:

In 19 75. arthroscopy was underused and needless arthrotomieswere performed. The pendulum is now swinging rapidly in theother direction. The current tendency in arthroscopy is towardoveruse. Some surgeons seems to be unable to distinguishbetween patients who are good candidates for arthroscopy andthose who are not. and the trend is toward arthroscopy in patientsin whom little likelihood exists of finding any treatable disorder.

(Casscells 1984).

Three years later, another author stated that

of those 9,000 North American surgeons and the other surgeonsof the world performing arthroscopy, many are ill-prepared andare therefore, not treating their patients fairly, Overuse and abuseby a few is hurting the many surgeons who are contributing toorthopedic surgery by lowering patient's morbidity, decreasingthe cost of health care, shortening the necessary time of patientsreturning to gainful employment, and adding to the developmentof a skill that has made a profound change in the surgical care ofthe musculoskeletal system. (McGinty 1987).

Arthroscopy remains the most sensitive and specific diagnosticmodality for intrasynovial evaluation in the horse. Thisis somewhat in contrast to human orthopedics, wherearthroscopy predominately is used for surgical interferenceand much of its diagnostic function has or is being replacedby magnetic resonance imaging (MRI). Arthroscopy hascontinued to be of great benefit in the horse, with increasedrecognition of soft tissue lesions in joints, tendons, sheaths,and bursa. However, as stated above, while there are manybenefits gained from arthroscopy, it is technically demandingand the need for training remains.

includes fractures of the metacarpal/metatarsal condyles andcarpal slab fractures (Richardson 2002, Bassage & Richardson1998, Zekas et aI1999), Techniques have been described forevaluation and treatment of so-called small joints, such as thedistal and proximal interphalangeal joints (Boening 2002,Boening et a11990, Vail & McIlwraith 1992, Schneider et al1994), In addition, joints in which lameness is less commonlyencountered. such as the elbow can also be examinedand treated arthroscopically (Nixon 1990),

Arthroscopic techniques for cartilage repair have beendeveloped and recently reviewed (McIlwraith & Nixon 1996,Nixon 2002b), In general, we have tried to develop techniquesthat enhance both the quantity and hyaline characteristics ofcartilage repair tissue while using the well-documentedadvantages of arthroscopic surgery. Techniques includecartilage debridement, cartilage reattachment. chondroplastyand subchondral microfracture (micropicking) (McIlwraith &Nixon 1996, Frisbie et al1999, Nixon 2002b).

The use of the arthroscope for evaluation and treatment oftendon sheath problems has been another area of majoradvancement. The arthroscope has been used to assess andtreat tenosynovitis of the digital flexor tendon sheath, andtechniques for endoscopically assisted annular ligamentrelease have been described (Nixon 1990b. 2002a. Nixon et al1993. Fortier et aI1999). Intrathecal longitudinal tears ofthe digital flexor tendons have also been described by Wright& McMahon (1999) and by Wilderjans et al (2003). Thearthroscope has also been increasingly useful for carpal sheathconditions (McIlwraith 2002a. Nixon et a12003, Textor et al2003); arthroscopic approaches have been described byCauvin et al (1997) and Southwood et al (1998b). Removalof radial osteochondromas using arthroscopic visualizationis a significantly improved technique to open approaches(Squire et al 1992) and has produced excellent results(Southwood et al1999, Nixon et al2003, McIlwraith 2002b).The use of tenoscopic division of the carpal retinaculum toopen the carpal canal has been recently described (Textor et al2003) and superior check ligament desmotomy is now donearthroscopically (Southwood et al 1997, Kretz 2001. Tech-niques for tenoscopy of the tarsal sheath have been describedby Cauvin et al (1999) and methods of treatment reported byNixon (2002a).

Synovial bursae have also been examined with thearthroscope. Techniques have been described for arthroscopyfor the intertubercular bursa (Adams & Turner 1999), thecalcaneal bursa (Ingle-Fehr & Baxter 1998). and the navicularbursa (Wright et aI1999). To date, reports in the literaturehave been dominated by cases of contamination and infection.but lesions which explain previously undiagnosed lamenessreferable to these sites have now been identified and treated

endoscopically.Specific advantages of arthroscopy as a diagnostic

and surgical tool are mentioned throughout this book.General advantages of the technique previously recognizedinclude:

1. An individual joint can be examined accurately through asmall (stab) incision and with greater accuracy than was

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Nixon AJ. Arthroscopic surgery of the carpal and digital tendonsheaths. Clin Tech in Equine Pract 2002a; 1(4): 245-256.

Nixon AJ. Arthroscopic techniques for cartilage repair. Clin TechEquine Pract 2002b; 1(4): 257-269.

Nixon AJ. Sams AE. Duchame NG. Endoscopically assisted annularligment release in horses. Vet Surg 1993; 22: 501-507.

dorsomedial intercarpal ligaments of the mid-carpal joint. VetSurg 1997a; 26: 359-366.

Whitton RC. Rose RJ. The intercarpal ligaments of the equine mid-carpal joint. Part II: the role of the palmar intercarpal ligamentsin the restraint of dorsal displacement of the proximal row ofcarpal bones. Vet Surg 1997b; 26: 367-373.

Whitton RC. Kannegieter NJ. Rose RJ. The intercarpal ligaments ofthe equine mid-carpal joint. Part III: clinical observations in 32racing horses with mid-carpal joint disease. Vet Surg 1997c; 26:374-381.

Wilderjans H. Boussaw B, Madder K. Simon O. Tenosynovitis of the--~ "-"" -

l'extor JA. Nixon AJ. Fortier LA. Tenoscopic release of the equinecarpal canal. Vet Surg 2003; 32: 278-284.

Trumble TN. Stick AJ. Arnoczky SF. et al. Consideration of anatomicand radiographic features of the caudal pouches of thefemorotibial joints of horses for the purpose of arthroscopy. Am JVet Res 1994; 55: 1682-1689.

Vacek JR. Welch RD. Honnas CM. Arthroscopic approach and intra-articular anatomy of the palmaroproximal and plantaroproximalaspect of distal interphalangeal joints. Vet Surg 1992; 4:257-260.

Vail TB. Mcllwraith CWo Arthroscopic removal of an osteochondralfragment from the middle phalanx of a horse. Vet Surg 1992; 4:269-272.

Valdez H. Richmond J. Wain L. Fackelman G. Operative arthroscopyin the horse. Equine Pract 1983; 5: 39-42.

Walmsley JP. Vertical tears in the cranial horn of the meniscus andits cranial ligament in the equine femorotibial joint: 7 cases andtheir treatment by arthroscopic surgery. Equine Vet J 1995; 27:20-25.

Walmsley Jp. Fracture of the intercondylar eminence of the tibiatreated by arthroscopic internal fixation. Equine Vet J 1997; 29:148-150.

Walmsley JP. Arthroscopic surgery of the femorotibial joint. ClinTech Equine Pract 2002; 1: 226-233.

cases. Equine Vet J 2003; 35: 402-406.Watanabe M. Takeda S. The 21

Tokyo: Igaku Shoin. 1978.Weller RR, Maieler 1}. Bowen

Whitton RC. McCarthy Rose RJ. The intercarpal ligaments of equinemid-carpal joint. Part 1: the anatomy of the palmar and

~

with 300 or 700 lens angles; and a 1.9 mm diameter arthro-scope with 300 lens angle. Generally. surgeons should choosethe largest diameter arthroscope that can safely be insertedand maneuvered without causing damage. Small diameterarthroscopes with appropriate operating instrumentationhave been developed for use in human carpal. metatarso-phalangeal. and temporomandibular joints (Poehling 1988).However. these are fragile. allow less illumination. and providea much smaller field of view (900 for 2.7-mm scope and 750for 1.9-mm scope). Small diameter arthroscopes usually alsohave a shorter working length (50-60 mm) because theexcessive flexibility of a longer instrument increases the riskof breakage (Poehling 1988). More recently. a complete rangeof sizes has also become available in video arthroscopes.which are coupled directly to the video camera. This obviatesthe need for a coupler and eliminates the potential for foggingbetween the arthroscope eyepiece and camera Gackson &Ovadia 1985). Flexible arthroscopes have also had a period oflimited use. but generally failed to provide true flexibility andoptical clarity (Takahashi & Yamamoto 1997). Combinedapproaches. using a rigid arthroscope for most of the procedureand a flexible arthroscope to access difficult areas of the hip.ankle. or knee in people. have added to the more thoroughevaluation of these joints (Takahashi & Yamamoto 1997).

A 4 mm diameter arthroscope with a 25 or 300 lens anglefulfills most needs of the equine surgeon (Fig. 2.1). A 4 mm700 arthroscope can occasionally provide improved visualiz-ation of specific areas of some joints such as the tarsocrural.shoulder. and palmar/plantar aspect of the metacarpo/

of instrumentation is available for humanarthroscopic surgery, but much of it is unsuitable andunnecessary for equine arthroscopy. Many of the operatinginstruments are expensive and fragile; for equine use alimited amount of equipment is generally essential orappropriate. The descriptions and recommendations in thistext are based on the authors' experiences and personalchoices and numerous substitutions can be made. Obviously,the potential for variation is extreme, and it is necessary tocontinue to evaluate new instrumentation as it becomesavailable or as new arthroscopic procedures are developed.This chapter represents the authors' current views oninstrumentation.

The available arthroscopes vary in outer diameter, workinglength, and in lens angle, which may be straight (0°) orangled from 5° to 110°. Many manufacturers market 4 mmdiameter arthroscopes with 0°, 30°, or 70° lens angles andworking lengths of 160-175 mm. The field of view is often115° or more, leading to their classification as "wide field ofview" arthroscopes. Most manufacturers produce smallarthroscopes, usually 2.7 mm diameter arthroscopes with30° or 70° lens angles; a short 2.7 mm diameter arthroscope

Nephew -Dyonics8 (Fig. 2.3), the 300 Hopkins rod lenstelescope made by Karl Storzb, and the 300 direct view andvideo arthroscopes made by Strykerc. Comparable-sizedarthroscopes are also available from Linvatecd, Richard WoW,Zimmerl, Olympus8, Arthrexh, and other companies. Theadvantages of the 25-300 angled lens are: (1) it provides anincreased field of vision; (2) rotating the arthroscopeincreases the visual field without moving the arthroscope;and (3) the end of the arthroscope can be placed at somedistance from the lesions, allowing easier access to the areawith instruments and minimizing the risk of damaging the

arthroscope.All arthroscopes are used within a protective stainless steel

sleeve or cannula (Fig. 2.4). For a 4-mm arthroscope thesleeve has a 5 mm or 6 mm diameter, and is connected to thearthroscope through a self-locking system that varies betweenmanufacturers. The sleeve has one or two stopcocks for ingressand/or egress fluid systems. The second stopcock is useful ifthe surgeon uses gas and fluid distention interchangeablyduring arthroscopy; otherwise, a sleeve with one stopcockoffers greater freedom of movement. A rotating stopcock iscritical to allow the ingress fluid line to be positioned awayfrom the limb and/or instruments as required. The spacebetween the sleeve and arthroscope allows flow of ingress

tarsophalangeal joints. Figure 2.2 illustrates the differentfields of view of a 250 arthroscope and a 700 arthroscope inthe same position in a tarsocrural joint. Popular choices in anarthroscope for routine equine arthroscopy include the 300videoarthroscope and direct view arthroscopes from Smith &

..Smlth&Nephew-Dyonlcs.150MlnutemanRoad. Andover. MA01810.Tel: (978) 749-1000. www.smith-nephew.com

.~arIStonVeterlnaryEndoscopy.175 CremonaDrive. Goleta. CA 93117.Tel: (800) 955-7832. www.ksvea.com

.'Stryker. 5900 Optical Court. San Jose. CA 95138. Tel: (800) 624-4422.www.strykerendo.com

.dLlnvatec-Conmed Co. 11311 Concept Blvd.. Largo. FL 33773.Tel: (800) 237-0169. www.linvatec.com

.'RIchard Wolf. 353 Corporate Woods Parkway. Vernon Hills. IL 60061.Tel: (847) 913-1113. www.richardwolfusa.com

.rZlmmer. PO Box 708. 1800 West Center St.. Warsaw. IN 46581.Tel: (800) 613-6131. www.zimmer.com

.SOlympus America Inc.. 2 Corporate Center Drive. Melville. NY 11747.Tel: (800) 848-9024. www.olympusamerica.com

.hArthrex. 2885 South Horseshoe Drive. Naples. FL 34104.Tel: (800) 933-7001. www.arthrex.com

~

sleeves have a wider diameter (5.8-6.0 mm

These so-called high-flow sheaths are very

for insertion of the sleeve inIn joints with a thick fibrous capsule

used to penetrate thesharp trocars for insertion and blunt

in the sleeve are now largely redundant.the arthroscope is provided by a fiberoptic

from a light source. The cable should be a

use of extremely light-sensitive video

by Richard Wolf Medical Instru-

with these light sources using video printers;careful control of the white balance of the

A light source with a flash unit is largely-

capture. The sources may be high-intensityillumination, xenon arc lamps (100-500 W), orvapor lamps (McGinty 1984). The xenon light

-the replacement

Dyonics 300XL xenon 300 W source, a Baxter-Edwards!Reliant 300 W xenon source, and a Stryker X-6000 500 Wxenon source (Fig. 2.7). The bulbs last from 350 to 500 hours,which represents a recurring cost for busy practices.

Light sources that automatically adjust the light intensityare useful to minimize the need for manual adjustment of

cold light fountain with 175 or 300-W lamp-,--,- 2.7), .'Baxter-Edwards, Baxter Healthcare Corp, One Baxter Parkway, Deemeld.

IL 60015. Tel: (847) 948-2000. www.baxter.com

light intensity. Most have a feedback electrical signal from thecamera control to light source for intensity adjustment. TheDyonics AutoBrite IITM Illuminator, the Stryker X-6000TMlight source, the Baxter-Edwards ReliantTM xenon lightsource, and the Karl Storz light source all employ usefulintensity feedback control. Most have the option to use this inan automatic mode or to switch to manual to override the iriscontrol. Additionally, many video camera control systemsnow also compensate for variation in light intensity, whichreduces the need for light source intensity changes.

Video cameras

Diagnostic and surgical arthroscopy can be performed bydirect visualization through the arthroscope; however, this isnow rarely practical and is no longer recommended. The risksof contaminating the surgical field and instruments areobvious. In addition, depth perception and ability to performfine movements are severely compromised with the monocularvision of a small image. Projection of images through a videoscreen corrects these deficiencies and allows simultaneousobservation of the procedure by several participants Gackson& Ovadia 1985). Additionally, video documentation throughstill image capture, video recorders, and digital video capturesystems (described later) provide sound surgical training,client satisfaction, and legal sense. Lightweight video camerasare attached directly to the eyepiece of the arthroscope(Fig. 2.8), eliminating the need for the eye to go to the arthro-scope. This also provides a more comfortable operatingposition since the surgeon can stand up straight, and thehands can be placed at any level. It is also possible for anassistant to hold the camera, which allows the surgeon use ofboth hands to manipulate instruments for fine control oraccess to difficult sites.

Solid-state video cameras are now conveniently small andlight and can be attached directly to videoarthroscopes,eliminating the coupler and any chance of fogging (Fig. 2.9).The united arthroscope and camera can be cold soaked,and/or gas sterilized. The solid-state cameras currentlyavailable produce an image from either one or three chips, ormore accurately, closed coupled device (CCD) chips (Whelan&Jackson 1992, Johnson 2002). These chips produce excellentimage quality. Most modern cameras use digital enhancementof the image, including motion correction algorithms, butstill output as an analog signal Gohnson 2002). Fully digitalcameras such as the Stryker 988TM video camera can writedirectly to a CD without capture devices, and provide a dense950 lines per inch image that requires an upgraded monitorto derive the most benefit from its circuitry. Durable and highimage-quality video cameras used by the authors areavailable from Karl Storz (Telecom SL camera), Smith &Nephew -Dyonics (ED-3 and D3 three-chip cameras; HD900single-chip camera), Stryker Endoscopy (888 and 988 three-chip cameras), and Arthrex. Several manufacturers produceautoclavable cameras: for example, the Smith & Nephew -

Dyonics 337 three-chip camera, which can be sterilized using

the flash autoclave cycle. in addition to more routine methods.These cameras are well sealed. making them durable. buthave previously been available only as single-chip devices.reducing the image quality. The authors' preferred method ofsterilization is with ethylene oxide gas (see Sterilization ofEquipment). This requires a minimal exposure/ventilationtime of 12 hours and. therefore. is usually suitable only forthe first surgery each day: Cameras for subsequent surgeries

sleeve. In countries where ethylene oxide is not

moisture between the arthroscope and camera

largely eliminated with cameras which have large,

vents is employed. the problem can be

and also by using warm irrigating fluid. Anti-

irrigation system

polyionic fluid is used for joint distention and~ during surgical arthroscopic procedures. The

an intravenous set connected to

used in human small joint surgery are also frequentlyinadequate (Oretorp & Elmersson 1986). The hand pumpallows the surgeon to broadly control the degree of distentionas well as the irrigation flow rate. A relationship betweenfluid pressure and fluid extravasation into the soft tissues hasbeen recognized in man (Morgan 1987); extravasationoccurs at approximately 50 mmHg (Noyes et al 1987).Control of fluid pressure is therefore desirable.

The most popular system for fluid delivery is now amotorized pump. Such pumps can provide both high flowrates and high intra-articular pressures. rThe simplest andfavored pump for two of the authors (C.WM. and I.M.W) isan infusion pumpk, such as the one illustrated in Fig. 2.11.Such pumps are relatively inexpensive (Table 2.1) and providehigh flow rates on demand, which is particularly useful fordistention of large synovial spaces (see also Chapter 3), butautomatic control of the pressure is lacking (Bergstrom &Gillquist 1986, Dolk & Augustini 1989). If an outflow portalis not open, excessive intra-articular pressures may causejoint capsule rupture (Morgan 1987). Extravasation of fluidis also a complication whenever excessive pressures aregenerated, and compartment syndrome has occurred usingmechanical pressure delivery systems in man.

The ideal pressure and flow automated pump should becapable of delivering necessary flow rates on demand, keeppressure at adequate yet safe levels, and include safetyfeatures such as intra-articular pressure-sensitive shutdownsand alarms (Ogilvie-Harris & Weisleder 1995). Many newpumps meet these criteria, including pumps made by Arthrex,Stryker Endoscopy, Smith & Nephew -Dyonics, Karl Storz,

to apply pressure (Fig. 2.10). This method is satis-

is economical and provides distention superior tofeed developed by suspending the fluids above the

Inc., Baxter Health Care Corp, One Baxter

gravity flow through sleeves

and Linvatec (see Table 2.1; Figs 2.12-2.14). Most providepressures from 0 to 150 mmHg and fluid flows as high as2 L/min. All but the 3M! and Linvatec pumps sense jointpressures through the single delivery fluid line. These featuresfacilitate visualization when large joints or motorizedequipment result in a demand for high fluid flows. From areliability perspective, the roller pump design of the Arthrex,Stryker, and Karl Storz pumps provide advantages over th(centrifugal and piston pump design of other manufacturersThe significant cost of these sophisticated fluid deliver)systems can be reduced by tubing lines that do not requirtcomplete replacement of the entire pump assembly durin{multiple case schedules. An example is the Arthrex pumIassembly (see Fig. 2.12) which replaces only the sterile line t<the patient between cases, providing new fluid delivery foJless than one-third the cost of a complete roller pump an<patient line set-up. Pressure and flow automated pumps arlmore expensive (see Table 2.1) and involve a more comple;set-up procedure during preparation for surgery. Howevelequipment prices are often reduced or rolled into a minimunpurchase of tubing, so the actual equipment cost can bpassed on to each case. Set-up and calibration are simpler 0]some pumps than others (see Table 2.1). A nitrogen drivelflutter valve pump with no electrical parts (Davolm) is a cos1effective intermediate-style pump that bridges betweelgravity feed and pressure-driven pumps (Fig. 2.15). Thisystem has been used by one author (A.J.N.) for many yearand is economical, simple to set up, pressure sensing, and cadeliver high flow rates (Smith & Trauner 1999). The di:advantages are the relatively slow recognition of pressUldrops in the joint and the noise of the flutter valve pum

assembly.The use of a balanced electrolyte solution, such as lactat(

Ringer's or Hartmann's solutions, rather than saline for joildistention has been recommended based on studies that sho

.'3M Orthopedics Pro1000. Tel: (888) 364.

:ts Division, 3M Cent.77. www.mmm.comrIossett Crossroad, PO.275.

www.davol.com

MN

31Nous

120 NoN/A Fair

N/A

1.0 No 69 Good

reservoir gas tank, including the Karl Storz and Richard WoUunits (Fig. 2.16). Others, such as those from Unvatec, Stryker,and Directed Energy, use a direct step-down valve systemfrom a commercial tank (Fig. 2.17). Arguments have beenadvanced for the use of gas insufflation of the joint ratherthan fluid distention during arthroscopy (Eriksson & Sebik1982); the gaseous medium (carbon dioxide, helium, or nitrousoxide) results in a sharper image with higher contrast. Aswell as being useful for photographs, some evidence existsthat it may offer an increased degree of accuracy in assessingcartilage damage in some situations (Eriksson & Sebik 1982).In addition, it can prevent synovial villi from interfering withthe visual field. However, a pressure-regulating device and aspecial system are necessary for gas insufflation. In addition,gas escapes easily after removal of any appreciable mass

saline is not physiologic and inhibits normal synthesis ofproteoglycans by the chondrocytes of the articular cartilage(Reagan et al1983). Any matrix depletion of the cartilageduring normal arthroscopic procedures would be minor andcertainly not permanent Gohnson et aI1983), but when thecost of each fluid is similar, the use of the most physiologicsolution is logical. The results of another study evaluatingthe acute effects of saline and lactated Ringer's solution oncellular metabolism demonstrated an acute stress to bothchondrocytes and synoviocytes immediately after irrigationwith both fluids, although this was greater with saline. Thesestress patterns (monitored by evaluating relative ATPregeneration) are apparent after 24 hours, appear tobe returning toward normal by 48 hours, and are notsignificantly different from control values 1 week later. Basedon these results, protection from full activity during this timeperiod was considered advisable (Straehley 1985).

Gas insufflation has been used routinely in equine arthro-scopy by two of the authors G.B. and A.J.N.). Several typesof gas insufflators are available. Most have a small internal

portal. Gas emphysema, pneumo-have been identified as

arthroscopy Gager 1980), and

better visualization when synovial

bone graft and fibrin-based

but many procedures start with liquid distention and only usegas for short periods of defined activity, which limits emphysema.Removal of small particles by suction obviously requires a fluidmedium, and fluid irrigation will also be necessary at the end ofany procedure for lavage and removal of debris.

At this stage, the authors consider the use of fluid irrigationmore convenient and experience with the use of fluid caneliminate many of the problems associated with synovial villiobstructing visualization. No additional equipment is necessary;and although the images obtained have somewhat less contrastcompared with images from gas-filled joints, superficial dalhageto the articular cartilage and other lesions are seen morereadily in the form of floating strands. Nonetheless, the additionof gas may be a necessary and convenient step in the future ifbone grafting, laser surgery, or fibrin-based cell grafting becomean important feature of arthroscopic surgery.

Egress cannula

An egress cannula (Fig. 2.18) is a necessary item for mostarthroscopic procedures. It has an accompanying locking

trocar with either a sharp stylet or conical obturator. Thecannula is used to flush fluid through the joint in order toclear blood and debris and optimize visibility. The outer endhas a luer attachment through which fluid can be aspiratedor to which a long, flexible egress tube can be attached totransmit fluid to a bucket on the floor rather than having itspillover the surgical site or equipment. The authors use a 2-or 3-mmegress cannula (Fig. 2.18a) routinely at the beginningof the arthroscopic procedure to flush the joint and to probeand manipulate lesions. A larger diameter (4. 5-mm) cannula(Fig. 2 .18c) can be used at the end of the procedure forclearing debris. The 3-mm cannula usually is inserted withoutthe use of the stylet, because a portal has been made with ablade. A conical obturator (Fig. 2.18d), however, is useful tofacilitate placement of the larger 4.5-mm cannula at the endof the procedure.

are available from all arthroscopic instrument manufacturers.Probes from different manufacturers vary in length and endconfiguration. The probe end can be round, square orrectangular and can vary from 3 to 6 mm in length. Longertips on the probe can hamper entry to the joint by tangling inthe capsule, while smaller probes are easy to insert but aremore prone to bending. A 3-mm rectangular end probe withtapered shaft is convenient and durable (see Fig. 2.19). Thehandle on probes can vary from a round smooth shaft. to arectangular shaft, which is easier to grasp, and to theaddition of a thumb bar for directed application of pressure.

Hand instruments forarthroscopic surgery

As mentioned previously, a myriad of instruments are avail-able from arthroscopic equipment manufacturers (Caspari1987, Gross 1993, Ekman & Poehling 1994), most of whichare neither suitable nor necessary for equine arthroscopicsurgery. The instruments presented in this section are thoseused by the authors to perform the procedures described inthis book. It is accepted that there are alternative, andpossibly better, ways to perform any given task and tech-niques certainly will change. The current list is written withthe philosophy of keeping arthroscopy simple and practicalwithout compromising standards. A combination ofspecialized arthroscopic instruments and instruments notdesigned specifically for arthroscopic surgery is used.

ForcepsCurrently. the authors use seven different forceps forretrieving fragments and trimming lesions (Figs 2.20-2.24).

1. Routine use. The workhorse in most arthroscopy packs isthe Ferris-Smith intervertebral disc rongeur. For removalof large fracture fragments and osteochondritis dissecansflaps. a pair of Ferris-Smith cup rongeurs with a 7 -inchshaft and a straight 4 x 10-rom bite (Scanlan Instruments)is used. These forceps are better than other types for thispurpose. Variation exists with regard to the shape of thejaws on different 4 x 10-rom Ferris-Smith rongeurs. Anarrow-nosed pair made by Sontec (Scanlan) is useful forcarpal and proximal phalangeal fragments. They passthrough the instrument portal easily and are appropriatefor small and medium-sized fragments (Fig. 2.20). Anotherpair of Ferris-Smith rongeurs with a 6 x l2-rom cup isused for larger fragments (Fig. 2.20). A set with the jawangled up and with a 4 x 10-rom cup are also useful insome tight situations. Some surgeons use a pituitaryrongeur for longer fragments.

2. Small fragments. Also recommended is a pair of straightethmoid rongeurs with a 5-rom bite (Richard Wolf orScanlan Instruments). These instruments have a pointednose and are useful for procedures involving chip fracturesoff the proximal aspects of the first phalanx (see Chapter 5).

Blunt Probe

This standard arthroscopic instrument (Fig. 2.19) is necessaryfor diagnostic as well as surgical arthroscopy. Suitable probes

Fig. 2.19(A) Variety of arthroscopic probes, fromlarge to small format, and with round.rectangular and thumb plate handles.(B) Probe ends vary in shape and size.

~

3. Long-handled forceps. A more verSatIle and longeralternative to the Ferris-Smith rongeur is the Mcilwraitharthroscopy rongeur (Fig. 2.21), made by SontecInstruments? Pituitary rongeurs are also used by otherarthroscopic surgeons for the same purpose.

4. Tight spaces. A small angled rongeur with slightlJlpointed tip (Fig. 2.22), often referred to as a patellarongeur (Sontec or Richard Wolf), is especially useful foIretrieving small fragments from difficult places, including

.nSontec (formerly Scanlan) Instruments Inc., 7248 Tucson Wa~Englewood, CO 80112. Tel: (800) 821-7496. www.Sonte.Instruments.com

Elevators and osteotomes

The instruments primarily used for separating fragmentsfrom parent bone include a small round-end curved periostealelevator or a straight narrow osteotome. Examples includethe small (6-mm) round-end SynthesO elevator, the 5-mmMcllwraith-Scanlan elevato~, and the 4-mm cottle osteotome(Scanlan) (Fig. 2.25). An extra small (3-mm) curved Syntheselevator is also occasionally useful (Fig. 2.25). A markedlycurved sharp-end periosteal elevator (Fig. 2.26) is useful forremoving apical sesamoid fragments (Foerner elevator;Scanlan Instruments; see Chapter 5).

Cutting instruments

Numerous cutting instruments are available. Their use islimited to certain situations. If sharp severance of structuresis required. special arthroscopic cutting instruments shouldbe used. The authors have used both reusable blades anddisposable blade systems (Fig. 2.27), made by Karl StOrzb,

the palmar surface of the metacarpal condyle or proximalphalanx, the palmar recesses of the midcarpal joint, andthe underside of the patella. The use of sharp-edgedrongeur-type instruments is preferred in most situationswhen pieces to be removed are still attached by soft tissue.

5. Loose bodies. Loose bodies can be retrieved with customequine loose body forceps, since most loose body forcepsavailable in catalogs of arthroscopic instruments are notstrong enough. For instance, Zimmer has taken the basicFerris-Smith design and changed the ends of the jaws forspecific purposes.

6. Cutting forceps. Basket forceps are used occasionally(Fig. 2.23) for removal of cartilaginous flaps of osteo-chondritis dissecans in the femoropatellar joint. A narrow,modified basket forceps (see Cutting Instruments section)is useful for severing soft tissue structures such asvillonodular pads.

7. Broken instrument retrieval. A fragment forceps with amalleable shaft is also occasionally useful, but notessential. These forceps are illustrated in Figure 2.24 andare made by Scanlan Instruments (Sontec).

."Synthes (USA), PO Box 1766, 1690 Russell Road, Paoli, PA 19301. Tel:(800) 523-0322. www.synthes-chur.ch

.nSontec (formerly Scanlan) Instruments Inc., 7248 Tucson Way,Englewood. CO 80112. Tel: (800) 821-7496. www.Sontec Instruments.com

.~arl Stol"l Veterinary Endoscopy. 175 Cremona Drive. Goleta, CA 93117.Tel: (800) 955-7832. www.ksvea.com

.

Wolfe, BeaverP, Dyonics, Acufex-Smith & Nephe~, Concept-Linvatec-Zimmer, and Bard-Parker. Sheathed blades arealso available and eliminate the risk of inadvertentdamage to other structures when introducing the blade(Fig. 2.28).

.nSontec (formerly Scanlan) Instruments Inc.. 7248 Tucson Way.Englewood. CO 80112. Tel: (800) 821-7496. www.Sontec Instruments.com

."Richard Wolf. 353 Corporate Woods Parkway. Vernon Hills. IL 60061.Tel: (847) 913-1113. www.richardwolfusa.com

."Beaver Surgical Products. Becton-Dickinson. BD Medical Systems. 1 BectonDrive. Franklin Lakes. NJ 07417. Tel: (800) 237-2762. www.bd.com

.qAcufex Microsurgical Inc.. Smith & Nephew. 150 Minuteman Road.Andover. MA 01810. Tel: (978) 749-1000. www.smith-nephew.com

Acquisition of the commonly marketed hook scissors isnot recommended for equine arthroscopy. The best scissor-type cutting instrument available currently is the verynarrow basket forceps (Scanlan-Mcllwraith scissor actionrongeur) (Fig. 2.29).

The authors have found little indication for the retrogradeor hook knives. other than those available for arthroscopicannular ligament transection (see Chapter 13). A menisco-tome can be useful for breaking down fibrous capsuleattachments when freeing a chip as it makes a cleaner cutthan a periosteal elevator.

Curettes

Curettes are used for debridement of most osteochondraldefects, including those remaining following removal oftraumatic or developmental fragmentation, evacuation ofsubchondral bone cysts, and debridement of foci of infection.Closed spoon curettes are suitable for most purposes, butopen ring curettes may be preferable for the center of lesions(Figure 2.30). Straight and angled spoon curettes, either 0 or00 in size, are generally preferred for routine applications(Fig. 2.30). A rasp is rarely necessary for smoothing debridedbone regions in joints, but may be useful for smoothing largerareas such as after radial osteochondroma removal. Theseinstruments are available in straight, offset convex andconcave designs from various manufacturers, includingStainless Manufacturing Incr.

Self-sealing cannulas

.'Stainless Manufacturing InCO 91773.

The use of self-sealing sleeves or cannulae is a logical answelto the loss of fluid through instrument portals. Either devictcan be used by screw insertion into the tarsocrural, shoulderor femoropatellar joints, but they are not useful in the carpu!

and fetlock because of the close proximity of joint capsuleand lesion. Disposable self-sealing 4.5-10-mm operatingcannulae are available through several manufacturers(Arthrex, Dyonics, Richard Wolf, or Acufe~). They are usefulfor repeatedly introducing small forceps, hand tools, andshavers, but in the horse, removal of osteochondral fragmentsis the most common procedure, and this can only rarely bedone through such cannulae. A 10-mm (I.D.) threaded self-sealing disposable cannula with insertion obturator (Clear-trac; Dyonics -Smith & Nephew) has been useful in shoulderarthroscopy (Fig. 2.31), otherwise operating cannulae arestill rarely used in equine arthroscopic surgery.

Vacuum attachments

While motorized equipment should be used only with dueconsideration to the synovial environment and tissues. theseinstruments are extremely efficient and some surgicalprocedures can only be done effectively with such equipment.Synovial resection. whether performed locally to improvevisualization of lesions or therapeutically on a subtotal basis.can only effectively be performed with motorized apparatus.Similarly, some large areas of osseous debridement. such asin shoulder or stifle osteochondrosis, become impossible tocomplete reasonably without such equipment. The basicconcept of motorized instruments is a rotating blade within asheath to which suction can be applied. This pulls soft tissueinto the mouth of the blade and removes debris (Graf andClancy 1987). Most currently available systems are poweredelectrically and consist of a control unit attached by anelectrical cord to a motorized handpiece. The latter may beoperated by buttons on the handpiece or via a foot pedal tothe control unit (Fig. 2.33).

Various instruments, including forceps and curettes, areavailable with attachments so that suction can be applied asthey are used. The S.2-mm DyoVac (Fig. 2.32) suction punchrongeur (Smith & Nephew -Dyonics) is used by one of theauthors (A.J.N.) for minor synovial resection, cartilage andsoft bone removal, or larger soft tissue pad or meniscustrimming. As such, this versatile rongeur gets more use thanmost instruments in routine arthroscopy. Further, it oftenprevents having to set up motorized equipment. Use ofsuction enables instant removal of debris as it forms duringdebridement within the joint. However, with the high fluidpressures used in equine arthroscopy, suction is often un-necessary as free material is often spontaneously flushed outthrough the suction channel. The use of suction during anyprocedure requires an increased rate of ingress fluid delivery.In general, the authors prefer to perform hand debridementwithout suction, reserving it for use with motorized instru-ments or to remove debris at the end of surgical procedures.

Motorized instrumentation

A large assortment of motorized arthroscopic instrumentsare available from most of the equipment manufacturers.

h & Nephew. 15049-1000. www.sm

Cutting heads or blades for the motorized units can bedivided into three broad groups: (1) blades designed toremove soft tissues such as synovium, plicae, and ligamentremnants; (2) blades to trim denser soft tissues such asmenisci; and (3) burrs for debriding bone. These blades aremostly available in disposable forms, although renewedinterest in reusable blades has resulted from the economicdownturn in medical practice. However, even disposableblades can be cleaned, sterilized and reused for a limitednumber of procedures (not recommended by manufacturer).In the authors' experience, this has been a safe practice.Generally, "fatigue" damage to the blades occurs at the plasticattachment to the handpiece or in the drive shaft of curvedsynovial resectors.

The authors have experience with the Smith & Nephew -

Dyonics Arthroplasty SystemTM, the Richard Wolf SurgicalArthro Power System, The Baxter-Edwards system, theStryker System, and the Karl Storz meniscotome. Dyonicsdeveloped the original shaver, and the third- and fourth-generation Dyonics systems (PS3500 and EP-1 shavers), arestill very popular. However, blade availability for these modelsis becoming increasingly limited, and many surgeons areupgrading to the Dyonics Power Mac system, or seeking adifferent manufacturer. Current shavers have integratedsuction with hand control of suction intensity. Somemanufacturers such Smith & Nephew -Dyonics and Strykeralso have speed and rotation direction controls on thehandpiece. Rotation speeds up to 8000 rpm and bidirectionalcapabilities are useful. The hand units of the Dyonics andStryker shavers are relatively heavy compared to Storz, Wolf,and Baxter shavers, but the heavier units are generally morepowerful. All modern shaver motors can be autoclaved andmost can be flash-autoclaved or cold-sterilized as necessary.Most shaver motors recognize the blade type that the user hasinserted and controls the motor speed range accordingly. Footcontrol of shaver speed and direction, including oscillationmode, is standard.

Each manufacturer provides a broad range of disposableblades, which often come with 6-8 cutting tip designs and withshaft diameter sizes of 5.5,4.5, or 3.5 mm. Some of these havea curved shaft 2 cm from the tip to allow greater maneuver-ability around joints. Additionally, a miniblade range of 2.0and 2.9-mm cutters with a variety of tip ends also areavailable. Three broad types of disposable blades (which canbe subjected to multiple uses) are available (Fig. 2.34):

1. smooth edged resectors, e.g. Dyonics Synovator and fullradius blades (in 3.5, 4.5, and 5.5 mm diameter sizes)

2. toothed edged resectors, e.g. Dyonics Orbit Incisor, IncisorPlus, RazorCut, Turbotrimmer, and Turbowhisker blades(in 3.5, 4.5, and 5.5 mm diameter sizes)

3. burrs, round or oval, e.g. Dyonics Abrader and Notch-Blaster in round burrs, and Dyonics Acromionizer,Acromioblaster, and StoneCutter in oval elongated burrs(in 2.5, 3.5,4.0, and 5.5 mm sizes).

The smooth-edged resector blades are appropriate forsynovectomy. The toothed-edged resector (for trimmingdenser soft tissue) can be used for articular cartilage debride-

ment, villonodular pad removal, and meniscus and soft bonedebridement, The round or oval burrs are occasionally usedin chronic degenerate joints, although other blades havesome value in similar situations.

Modern synovial resector units are much more useful thanprevious types. Design changes including larger apertures,higher speeds, narrower diameter drive shafts (easier debrisclearance), spiral flutes down the length of the drive shaft,and application of suction, have all contributed to better softtissue resection and less clogging. The oscillating modecapability of the motor (the unit switches automaticallybetween forward and reverse) facilitates cutting of fibroustissues and decreases clogging between the blade andhousing. The speed control is computerized, with a variablespeed capacity from 0 to 8000 rpm. High speeds are necessarywhen using the burr, whereas slower speeds are used with thesoft tissue blades.

Stocking of all the blade types is unnecessary; mostsurgeons develop a preference for 1 or 2 soft tissue blades, and

a burr. In the Dyonics range, the authors prefer the 5.5-mmfull radius blade (#7205307) for villonodular pads andmenisci, the 4.5-mm rotatable curved orbit incisor(#7205320) or Incisor Plus (#7205687) for most other softtissue resection, and the 4.0-mm Acromionizer (oval burr;#7205326) or 4.0-mm Abrader (round burr; #7205324) forbone debridement (see Fig. 2.34). Recently, a range of dual-use combination tips (Dyonics BoneCutter) have been intro-duced, which resect both soft tissue and bone. These areavailable in synovator and full-radius styles, and minimizeboth inventory and the need to switch blades in surgery.

Use of suction on shavers generally improves cuttingperformance. However, attention to the degree of filling ofthe suction bottle is required to prevent the automatic suctionshut-off engaging, which can then allow fluid to flow backfrom non-sterile tubing and couplers at the bottle throughthe sterile patient line and out the shaver into the joint oronto the sterile field. It has been recognized as a potential riskin the use of shavers for some time (Bacarese-Hamilton et al1991), and it is particularly likely to happen when the fluidingress runs out at that same moment, removing the positivepressure forcing joint fluid into the suction line. Preventionrequires suction to be maintained on the tubing at all times,or at the very least ensuring the joint is pressurized duringsuction bottle exchange.

the subject of ongoing debate. investigation. and litigation(Lee et al 2002). Given these issues. RF for chondroplastyshould be avoided until further studies define safe settings.and the use of RF probes in cutting modes for capsule. checkligament. or annular ligament transection should use theminimal power settings that still achieve the desired effect.and should absolutely avoid cartilage and underlying bone.

Lasers

Electrosurgical andradiofrequency devices

Considerable interest and concurrent concern surrounds theuse of radiofrequency (electrosurgical) devices for cartilageand synovial soft tissue procedures (Polousky et al 2000,Medvecky et al2001, Lu et al2001, Lee et al2002; Sherk et al2002). Radiofrequency (RF) devices utilize extremely high-frequency alternating current (e.g. 330 kHz compared to the60 Hz of regular alternating current), which passes to thetissue at the applicator tip and then through the body to exitat a wide grounding plate, essentially as for all electrosurgicalunits. The cutting and vaporizing capability depends on thepower and waveform settings. High power settings and lowvoltage tends to cut, while low power settings at relativelyhigh voltage denatures and coagulates tissues (Sherk et al2002). Used in the liquid environment of the joint, both ofthese modes have found a place for excision of tissue (plica,adhesions, villonodular masses), or denaturation of cartilage(cartilage sculpting or chondroplasty). Radiofrequencydevices used in a cutting mode, at the lowest settings that willstill cut plica, ligament, menisci, or masses, seem to be safe ifthe probe is directed away from cartilage and does not dwellon bone (Polousky et al 2000, Lee et al 2002). Similarly,thermal capsular shrinkage using low power settings hasmany proponents and seems relatively low risk (Medvecky etal 2001). However, RF devices used for thermal chondro-plasty at recommended settings penetrate to the subchondralbone and cause chondrocyte death (Lu et al 2000, 2001).Despite the apparent smoothness of cartilage after RFchondroplasty, the later necrosis can be devastating, and is

Lasers have been used in arthroscopic procedures for removalof fibrillated cartilage. synovial proliferation and masses. andfor transection of plical and other adhesive syndromes(Lubbers & Siebert 1997. Janecki et al 1998. Smith &Trauner 1999). They have declined in popularity in recentyears due to the continued high cost of the units and concernover thermal damage to the cartilage and underlying bone(Atik&Tali 1999. Sclamberg & Vangsness 2002). Laser typesinclude COp Nd:YAG. Ho:YAG. and excimer wavelengths. Theuse of CO2 lasers has diminished. while Ho:YAG and excimerlasers have persisted (Roth & Nixon 1991. Smith & Trauner1999. Doyle-Jones et al 2002). Laser capsule shrinkage forshoulder and knee disorders and laser-assisted partialmeniscectomy remain the primary use in man (Lubbers &Siebert 1997. Smith & Trauner 1999). Laser chondroplastyhas been controversial and. despite an excellent appearancefollowing laser sculpting. later cartilage necrosis and mountingresearch evidence suggest the use of laser for cartilage debride-ment is dangerous unless extreme care in power settings andmethods of application are employed Ganecki et al 1998.Sclamberg & Vangsness 2002; Atik et al2003).

Laser-assisted arthrodesis of the distal tarsal jointsprovides a minimally invasive method for cartilage debride-ment and articular desensitization (Hague & Guccione2000). Eventual distal intertarsal and tarsometatarsal jointarthrodesis can develop; however. resolution of the symptomsof bone spavin do not necessarily require radiographicallydefined obliteration of these joints.

Still photography

Historically, still photographic images have been recorded on35-mm film using a camera with a quick mount adaptor tothe arthroscope. However, this is time consuming, riskscontaminating the surgical field, and is extremely lightsensitive. A practical alternative is to use a digital camerasuch as a Nikon Coolpix 4500 fitted with an endoscopeadaptor, e.g. Karl Storz rapid coupling adaptor (Fig. 2.35).Images are viewed on a screen on the back of the camera,stored on a memory card, and may be downloaded later to acomputer for image adjustment and archiving.

Video documentation-

Capture of video clips as analog video on a ~-inch VCR i:simple and cost-effective for case documentation. It does not

however, provide duplicate copies to provide the owner ortrainer with surgical documentation, nor does it provide easyaccess to an individual case buried in the middle of a 120-minvideo tape. Review of a video and subsequent image capturefor still printing is also very time consuming and does notlend itself well to the flow of information to the client. How-ever, video and s-video formatted VCRs have become verycheap, and are better than no documentation. Further, simplevideo digitizing programs, such as Windows MoviemakerTM(Microsoft), iMovieTM (Apple), VideoStudio 6TM (ULeadSystems), or Pinnacle Studio Version 7TM (Pinnacle SystemsInc), all provide a means to capture video from !-inch tapes asdigital video (e.g. MPEG format) or as digital still images (e.g.JPEG format) that can then be stored electronically or printedout for several cents an image on a color ink-jet printer.Additionally, digital video clips can be edited, trimmed,spliced, and assembled into an annotated presentationusing these programs. Other capture systems using Hi8video capture have been described and for a complete reviewof arthroscopic image documentation, the reader isdirected to a recent review which provides an in-depthcomparison of systems, cabling, connectors, and outputdevices (Frisbie 2002).

capture the image (often by clicking a button on the videocamera), and store and arrange the images during thesurgery. A 3.5 x 5 or 6 x 8-inch print is produced when apreset number of images have been accumulated to memory.The print quality (300 dpi) from a high end, digitallyenhanced, 3-chip camera can be photographic quality(Brown 1989). The authors have used the Sony MavigraphUP-5600MD, Mavigraph UP-5200MD and the MavigraphUP2900 color video printers. The UP-5600MD providesexcellent image quality at approximately $1 per page. Theseunits sell for $4,000-$6,000. More economical storage canbe provided from small devices such as the Sony MavicapTMelectronic capture and storage device. This stores images onfloppy disks, which can then be printed on an office computerand inexpensive color ink-jet printer.

Complete digital capture and storage devices for arthro-scopic use are manufactured by Karl Storz, Stryker, andDyonics. All three units are expensive, but store both digitalstill images (TIFF format-with Storz AIDA and JPEG formatswith others) and digital video clips (MPEGI or 2), with thetouch of a button on the camera head. The Stryker SDC Pro2TM and the Storz AIDA are the more sophisticated units inthe field of digital storage devices (Figs 2.37 and 2.38). Theunits have touch screen patient input, and image editing forstill image output. Image printing can be done in the surgeryby attaching an inexpensive HP deskjet printer, while still andvideo images are also saved on the system's hard drive. At thecompletion of each case, the files are saved on CD or DVD. Thesoftware in the unit provides versatile settings that allowextensive customization of image capture and compression,image editing, output styles, text addition, and internetaccess. Retail prices range from $12,000 to $16,000. TheSmith & Nephew -Dyonics Vision 625 Digital Capture

Digital ima~e capture andstorage devices

Arthroscopic image printing and storage has undergonesignificant improvement along with the electronic revolutionof the previous decade. The simplest technique for imagedocumentation is electronic capture and printing on a dyesublimation printer (Brown 1989. Johnson 2002). Self-contained units such as the Sony MavigraphS (Fig. 2.36).

.'Sony Electronics, 1 Sony Drive, Park Ridge, NJ 07656. Tel:(201) 930-1000. www.sonystyle.com

materials may deteriorate from thermal shock; variousmaterials expand and contract at different rates in responseto the rapid temperature changes in a steam autoclave. Somemanufacturers sell autoclavable arthroscopes, which providea more durable arthroscope for steam sterilization. Gassterilization with ethylene oxide is effective and safe, but it isnot always available, is time consuming and does not allowmultiple procedures in a day using a single set ofinstruments.

Consequently, the use of a 2% solution of activateddialdehyde (Cidex@, Surgikos Inc:) was developed as an agentfor cold sterilization procedures. Cidex Plus@ has a 30-dayshelf life after reconstitution, compared to the 14-day span ofCidex@, which provides cost savings for frequent users. Thesafety and effectiveness of Cidex has been documented in12,505 human arthroscopic procedures (Johnson et al1982). A 0.4% infection rate was noted in this series. Thearthroscope and surgical instruments are soaked for aminimum of 10 minutes. It has been stated that more than30 minutes of soaking can be damaging to the lens system ofthe arthroscope (Minkoff 1977). Glutaraldehyde polymerizeson standing. When this occurs, crystals can form and causeclouding of arthroscope lenses.

The surgeon or assistant should be double gloved andremoves the instruments from the Cidex and places them in asterile tray. The instruments are washed with sterile water orsaline (Fig. 2.40) and transferred to the surgery table wherethey are dried after the surgeon's outer gloves are removed.Ancillary instruments (towel clamps, scalpel handle, needleholder, and thumb forceps) can be previously autoclavedwithin the tray, which is then used for washing the soakedinstruments. Rinsing of the equipment must be done withcare to avoid damage to the camera and arthroscope fromsharp-edged hand tools.

(Fig. 2.39) provides many similar features to the

be via zip disk or CD drive. and the$9,700 to $12,000.

of equipment

steam autoclaving shortens the useful life of anby causing deterioration of the adhesives

the major lenses. Seals and bonding between .'SurgikosInc.. POBox 90130, Arlington, TX 76004. Tel: (817)465-3141

accumulates, stopcocks and other moving parts cease tofunction smoothly. Surfactant-containing solutions can alsoerode epoxy and other thermal plastics. From personalexperience, severe damage resulted when soaking a camerain such a solution. Another recommendation is that plasticbasins be used to soak instruments (McDonald 1984). Thesebasins reduce electrolytic corrosion, which can occur whenmetal instruments are soaked in metal pans.

The question of the potential for Cidex to cause a chemicalreaction in joints was addressed in the literature (Harner1988). Results of studies in rabbits showed that Cidexinduced a diffuse synovial inflammation when present intra-articularly at concentrations of 10 ppm or greater. Thedegree of synovial inflammation is proportional to theconcentration of Cidex. At 1000 ppm, chondrolysis occurs.When using a single-rinse basin, the concentration of Cidexin the rinse basin is 100-300 ppm; if the same rinse solutionis used, the concentration can be 1000 ppm by the fifthprocedure. Clearly, fresh-rinse solutions should be used foreach procedure. A double rinse reduces the Cidex concen-tration in the second rinse to the order of 1 ppm. Mterirrigation of the joint with 1 liter of saline, however, theintra-articular concentration of Cidex is less than 1 ppm,regardless of the rinse technique (Harner 1988).

Toxicity and safety issues have reduced the use of Cidex inmany practices. An effective and less toxic alternative is theperacetic acid SterisTM systemU, which uses a liquid peraceticacid (35%), acetic acid (40%), hydrogen peroxide (6.5%), andsulfuric acid (1 %) soak, followed by a water rinse, for a total of4 cycles in a closed system, to provide sterile and virtually dryequipment for arthroscopy (Fig. 2.41). Each sterilizing runhas a chemical indicator strip (min 1500 ppm) included toverify the sterility of the instruments. The disadvantages arethe cost of the unit, and the process requires 30 minutesrather than 10 minutes to complete, so emergency sterilizationfor a dropped instrument still requires Cidex.

In many parts of Europe, the use of Cidex is no longerpermitted. A safe alternative is MedDisTM instrumentdisinfectantV, which relies on halogenated tertiary amines,hexamethylene biquanide hydrochloride, ethyl alcohol,dodecyclamine, and sulfonic acid to sterilize instruments.This solution is diluted to 5%, and is then bactericidal,fungicidal, and virucidal after a 10-minute exposure, andtuberculocidal and sporicidal within 30 minutes. Shelf lifeafter activation is 14 days. It also has safety advantages inthat it is non-irritant, non-fuming, non-corrosive, and has noreported effects on metal or glass endoscope components.

The 2% dialdehyde solution is properly classified as adisinfectant. The chemical is considered bactericidal in10 minutes, destroying all bacteria, including Myobacterium,tuberculosis, Pseudomonas aeruginosa, and viruses. It issporicidal in 10 hours and therefore is considered a sterilizingagent after use for 10 hours Uohnson et al1982).

A number of glutaraldehyde-based disinfecting solutionsare available. Use of a solution that does not contain asurfactant is recommended (Cidex-activated dialdehydesolution does not contain a surfactant). Surfactants may leavea residue, causing stiffening of moving parts and potentialelectrosurgical malfunction. Because surfactants lower thesurface tension of the disinfection solution, the disinfectantcan penetrate small cracks and crevices. This penetrationcreates a rinsing problem, because high surface tensionprevents water from entering the cracks and crevices andremoving the disinfectant. As this disinfectant residue

Surgical assistants

Because of the unique instrument requirements and the needto have a smooth sequential system during the operation,scrub nurses or technicians participating in operativearthroscopy must be especially trained. It cannot be

.USteris 20. Steris Corp, 5960 Reisley Road. Mentor. OR 44060. Tel: (800]548-4873. www.steris.com

."Medichemlnternational. POBox 237, Seven Oaks. Kent TNI 5 02J. UK

minimal or extensive draping byvary from simple reuseable cloth

the horse, several small drapes for

The sticky drapes (loban, 3M!) is a very

of liquid used in arthroscopy. Application of an adhesivedrape followed by one or two surrounding impervious drapes,and finally a large disposable drape is standard (Fig. 2.42).For simplicity, a large sticky drape provides a good sterile fieldto which an experienced user can then apply a largedisposable drape directly, to complete the sterile set-up. It iscritical that the surgeon and his assistants not drag thedisposable drape across the prepared joint (double shuffling)or the inner surface of the disposable drape that has con-tacted the animal will then rest over the joint to be operated.Inexperienced users should add a quadrant of additionaldraping between the adhesive drape and the large arthro-scopy drape, to increase the margin of safety. Large drapesystems are manufactured by Gepcow and Veterinary SurgicalResourcesX. Some arthroscopy packs also contain disposablegowns. In general, most manufacturers offer a range of packcontents, so individual preferences can be accommodated.Clearly, the complete systems lack nothing, but can be ex-pensive (up to $82). The arthroscopy drape pack can beordered for unilateral or bilateral arthroscopy, the latter pro-viding two rubber dammed areas, one per joint, with 30-38inches between them. These can be cumbersome to apply, butprovide exceptional large sterile fields without the need forother body sheets. The authors also vary the type of drapingto the situation; numerous drapes around the foot will limitaccess for coffin joint arthroscopy or digital sheath tenoscopy,whereas full draping systems are easy to apply around thestifle or hock, and provide ready access to all the jointscomprising these articulations.

Care and maintenance of equipment

Most care and maintenance issues should be covered byinstructions with individual equipment items. However.repair of arthroscopes is a costly and all too frequent concernin equine arthroscopy. All arthroscope vendors repair theirown telescopes. However. the cost can vary (depending on theextent of damage) from $1.000 to $2.200 (almost the cost ofa new arthroscope). Third-party vendors repair arthroscopesfrom most manufacturers. One of the larger repair companiesthat an assistant totally familiar with the

.13M Orthopedics Products Division. 3M Center. St. Paul. MN 55144-1000. Tel: (888) 364-3577. www.mmm.com

.wGepco. General Econopak Inc.. 1725 North 6th Street. Philadelphia. PA19122. Tel: (888) 871-8568. www.generaleconopak.com

.'Veterinary Surgical Resources. Inc. PO Box 71. Darllngion. MD 21034.Tel: (800) 354-8501. www.vetsurgicalresources.com

and draping systems tend to be determined by thepreference, cost of drapes, and the safety and

is Instrument Makarr. The cost of repair generally ranges from$350 to $600. However, the repair vendor should alwaysprovide a free assessment of damage and a quote for repair. Amore informed decision for repair or replacement can thenbe made.

Pressure and cold bandaging

Preoperative and postoperative pressure bandaging is commonpractice in equine arthroscopy. but use of combination coldand pressure devices has been underutilized. The value of cryo-bandaging following acute injury is well known to horsetrainers and owners but largely ignored in the immediate post-operative phase by surgeons. The use of wet ice and ice slushesshould obviously be avoided. given the recent incisions intothe joints. However. dry cold products have a role in reducingthe postoperative pain and swelling that is recognized inhuman arthroscopy and in the rehabilitation of athletes(Barber et al1998. Martin et al2001). Some cryo-cuff devicescombine both cold and pressure massage systems (Fig. 2.43)

.'Instrument Makar. Division of Smith & Nephew Inc. Endoscopy Division.150 Minuteman Road. Andover. MA 01810. Tel: (800) 343-5717.

www.endoscopy1.com

Motorized arthroscopic instruments: a--

setup and equipment. Orthop Clin

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al 1995). These devices' have been used fol-

and the resolu-particularly periarticular swelling, has

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IA. Bhamra M. Jackson AM. Arthroscopic, 'sepsis. Ann R Coil Surg

McGuire DA. Click S. Continuous-flow cold therapy, anterior cruciate ligament reconstruction.

130-135.an infusion pump in arthroscopy.

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Augustini B-G. Three irrigation systems for motorized.surgery: a comparative experimental and clinical

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carpus after arthroscopic mechanical or carbon.Vet Surg 2002; 31; 331-343.

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Johnson DH. Basic science in digital imaging: storage and retrieval.Arthroscopy 2002; 18: 648-653.

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Johnson RG. Herbert MA. Wright S. et al. The response of articularcartilage to the in vivo replacement of synovial fluid with saline.Clin Orthop 1983; 285-292.

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McGinty JR. Photography and arthroscopy. In: Casscells SW (ed.).Arthroscopy: diagnostic and surgical practice. Philadelphia: Lea& Febiger; 1984.

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.'Equine Cryo-Cuff, Game Ready CoolSystems Inc., 929 Camelia St, Berkeley,CA 94710. Tel: (866) 266-5797. www.gameready.com

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Sclamberg SG. Vangsness. CT Jr. Laser-assisted chondroplasty. ClinSports Med 2002: 21: 687-691. ix.

Sherk HH. Vangsness CT. Thabit G ill. Jackson RW Electromagneticsurgical devices in orthopaedics. Lasers and ramofrequency.J Bone Joint Surg Am 2002: 84-A: 675-681.

principles can be applied to the other joints. The

maneuvers in the different joints are

evaluation of the patient

undergoing an arthroscopic procedure for aor suspected intra-articular problem must first be

These principles may be taken for granted by,. The hazard of avoid-

has also been noted in association with

1983).the lack thereof) are discussed

preparation

and surgical scrub for the surgeon is routinely done witheither povidine iodine or chlorhexidine gluconate. Theauthors have switched to the latter. The iodophors haveseveral disadvantages, including diminished effectiveness inthe presence of organic matter, a high incidence of dermalirritation, potentially unreliable residual activity, and toxicity(Phillips et al 1991, Rosenberg et al1976). CWorhexidineclosely fulfills all the criteria of an ideal preoperative patientskin preparation: having a broad spectrum of antimicrobialactivity, it reduces bacterial numbers quickly by disruptingthe bacterial cell membrane and precipitating cellularcontents, has excellent residual activity (even in the presenceof organic material), and causes minimal skin irritation(Stubbs et al1996). However, it should be noted that in astudy evaluating the effectiveness of a 5-minute surgical scrubusing either a one-brush or two-brush technique in clean anddirty surgical procedures, and also comparing the efficacy ofpovidone iodine with cWorhexidine as surgical scrub solutions,both povidone iodine and cWorhexidine were equally effectivein decreasing bacterial numbers on the skin, given a varietyof contamination levels present before the scrub procedure(Wan et al1997).

The authors perform all arthroscopic surgical proceduresin the carpus, dorsal fetlock, tarsus, and stifle joints, with thehorse in dorsal recumbency, except in isolated instanceswhen the facilities do not allow this positioning. Arthroscopicsurgery on carpal, fetlock, and tarsocrural joints is quitefeasible with the horse in lateral recumbency, but if entrysites for the arthroscope need to be switched (when chips arein both sides of the joint or in the same location bilaterally),rolling the horse during surgery often is necessary. Dorsalrecumbency is mandatory for arthroscopic surgery in thefemoropatellar joint.

The method of draping is the choice of the individualsurgeon. Because of the fluid involved, an impervious drapingsystem is needed (Fig. 3.1). The use of adhesive barrier drapesis also recommended. Some problems have occurred withsome of these products in regard to adhering to the skinsatisfactorily. In this regard, Iobana drapes are superior.

-

skin incisions so that a hair or portion of hair is notinto the joint on insertion of the arthroscope or

arthrocentesis sites. it has been concludedthe skin over the midcarpal and

joints can be accomplished without

.8Ioban. 3M Orthopedics Products Division. 3M Center. St. Paul. MN55144-1000.

Arthroscope insertion and positioning

A 6- to la-mm skin incision is made at the site of insertion ofthe arthroscope (Fig. 3.2). The various sites of insertion ofthe arthroscope and instruments for each joint are detailed inlater chapters. In the carpal joints. the incision is madebetween the extensor carpi radialis and common digitalextensor tendons for a lateral approach and medial to theextensor carpi radialis tendon for a medial approach. Also.these incisions are made before distention of the joint withfluid so that the puncture site position in relationship to thesetendons and their sheaths is carefully placed. The position ofthe tendon sheath can be obscured once the joint isdistended. If the arthroscope is not introduced in the propersite, the maneuverability can become limited and undesirablepenetration of certain structures (such as bursae or tendonsheaths) may occur.

In joints other than the carpus, distention is performedprior to making portals. as avoidance of tendon sheaths isnot an issue and the distended joint aids in portal location(Fig. 3.3). This distention prevents damage to the articularcartilage when the trocar or conical obturator penetrates the

joint capsule.

A No. 11 or No. 15 scalpel blade is then used to make aportal in the joint capsule. A conical obturator is placedwithin the arthroscopic sheath and this combination is usedto insert the sheath through the fibrous joint capsule with a

entry of the latter into the joint. Direct arthroscopic visualiz-ation of the joint can then be performed (extremely rarenowadays) (Fig. 3.6), or the video camera (see Chapter 2) canbe attached. depending on the method used by the surgeon.

If the camera has not been soaked. the use of a sterilesleeve is necessary. If using a sleeve. it is important to ensurea watertight seal of the cover over the head of the

arthroscope.After insertion of the arthroscope. in the case of the

carpus, the instrument portal through the joint capsule ismade with a direct perpendicular stab with a No. 15 orNo. 11 blade (Fig. 3.6). In other joints, the instrument portalis made in the same fashion. but often a needle is placedin the proposed position and visualized. and, if appropriatelylocated, the instrument portal through skin and jointcapsule is then made. The authors' prefer to create the portaland then insert the small egress cannula without usinga trocar or obturator (Fig. 3.7).

gentle twisting motion (Fig. 3.4). The sheath is initiallyinserted perpendicularly to the skin surface. avoiding anytendency to angle toward the ultimate position of the scope.This position is to obviate opening a subcutaneous dissectionplane. Advancement of the sheath within the joint isachieved most safely by use of the blunt or conical obturator,because the articular cartilage is at risk for damage when thesheath containing the arthroscope is advanced. This risk hasbeen decreased by improved congruity between the ends ofthe sheath in relationship to the end of the arthroscope incurrently available instruments. The authors no longer usethe sharp trocar for insertion of the arthroscopic sleeve in

any joint.Once the arthroscopic sheath is in place, the blunt

obturator is replaced with the arthroscope, and the fiberopticlight cable and the ingress fluid system are attached to thearthroscope and the sleeve, respectively (Fig. 3.5). Theingress fluid line has been cleared of air bubbles to avoid

Any cloudiness or hemorrhage within the joint can becleared by opening the egress cannula and pumping fluidthrough the ingress system. Regarding the use of the egresscannula in the carpal and fetlock joints, the holes in thecannula must not extend more than 6- 7 mm from the end ofthe cannula. If they do, the cannula should be shortenedappropriately. Otherwise, some holes will not be within thejoint but will be within the subcutaneous tissues, promotingrapid extracapsular extravasation of fluid.

Once the view is clear, the stopcock on the egress cannulais closed during visualization; otherwise, villi waving withinthe flowing fluid obstruct the view (Fig. 3.8). This point needsemphasizing because other authors in equine arthroscopymention the difficulties with synovial villi obstructing thevisual field, and advocate the use of adjunctive synovialmembrane resection. This procedure necessitates the use ofmotorized equipment. Alternatively, gas distention ratherthan liquid distention prevents this problem. In diagnosticarthroscopy of the human knee, the use of both a suspendedfluid source and constant flow of fluid through the knee have

been recommended (Crane 1984). In the authors' opinion,this technique is unsatisfactory in the carpus and fetlock ofthe horse because of the smaller size of the joint and theincreased amount of synovial villi. As referred tosubsequently, villi interposition is not a problem inarthroscopic procedures in the human knee, but it is often amajor one in the horse, necessitating the use of differenttechniques to handle this situation. The use of closeddistention obviates the problem of villi interposition ratherwell in most instances.

Any fluid system capable of exerting pressure within thejoint has the potential to cause its own complications (Noyes& Spievack 1982). Joint capsule rupture in the human kneeat about 200 mmHg pressure has been recorded, and thisrupture in turn causes severe extracapsular extravasation offluid. Flexion of the joint markedly elevates the pressure in agiven joint. Severe flexion changes during equine arthroscopyare rare, but a situation of high intra-articular pressure candevelop easily. The choices of fluid systems were discussed inChapter 2. The requirements for joint distention in equinearthroscopy are quite high; at the same time, however, it isimportant to be aware that excessive pressure can exacerbatethe degree of fluid extravasation with or without jointcapsule rupture. For these reasons, the authors do notrecommend the use of constant pressure fluid administrationsystems, including fluid bags with pressure cuffs or bulbsyringe pressure cuffs or direct gas insufflators. Two of theauthors use a Cole-Parmer system where variable flow ratescan be changed quickly. In this way a slow flow rate is usedunder the closed examination and then this flow rate can beincreased as necessary when there is an open instrumentportal. Pumps used in human arthroscopy have improved(see Chapter 2) and are generally now available free ifsufficient delivery tubing is purchased. The system recentlydeveloped by Arthrex@ has been used in the horse and is

effective.During arthroscopic surgery, once a larger instrument or

fragment passes through a portal in the joint capsule, somedegree of constant fluid egress through this portal is unavoid-able. Consequently, some villi interposition occurs. For thisreason, the diagnostic examination must be completed beforesurgical removal of large fragments from the joint. For thesame reason, a small (2.7-3.0 mm) egress cannula is used foran initial flush. This avoids a large instrument portal and thecontinuous fluid flow during the initial examination.

The arthroscopist should be continually reminded thatvisualization could be enhanced greatly by rotating thearthroscope. Simply by rotating the arthroscope (withoutchanging the position of the arthroscope), the visual field ofview is greatly increased. This generally obviates the need for

a 700 arthroscope.

Arthroscopic surgery and the principleof triangulation

Although the details of arthroscopic surgery for each jointare presented in later chapters. the principle of arthroscopic

here because the use of both the Use of the probe indiagnostic arthroscopy

For effective diagnostic arthroscopy, the use of a probethrough an instrument portal is important, both to evaluatedefects that cannot be discerned with vision alone and toprovide an index of size by comparison of the lesions with theprobe (see Fig. 3.9). In the carpus, the egress cannula is oftenused as a probe to palpate lesions. This technique is a "shortcut", often eliminating the need for another instrumentinsertion. On the other hand, the blunt, hooked probe isimportant in assessing suspect articular cartilage in cases ofosteochondritis dissecans, and its use is a routine part of theprocedure. Elsworth et al (1986) noted, "arthroscopy with-out the use of the probe is an incomplete investigation," andthat routine use of the probe is essential in training for

arthroscopic surgery.

and they are used according to

Two basic techniques have been developed for arthroscopic-

Although it

orthopedic practice (Carson 1984), the techniquenot been used in equine surgery and therefore is not

The second technique is triangulation. which involvesone or more operating instruments through

-~

the instrument and the arthroscope forming

3.9, (and also in Figs. 4.21 to 4.23) and it isto handle all of the various surgical requirements in

-- Post-arthroscopic irrigation and closure

as well as surgical arthroscopy. To be able to usetechnique effectively, the surgeon must develop the

confined space while using monocular vision, which

.,

For arthroscopic surgery, instrument portals are made in, .on the joint and the site of the

Cannulas or sleeves are rarely used at instrumentfor reasons mentioned in Chapter 2. To create an

a skin incision is made followed by a stabthe joint capsule with the use of a No. 11 or 15

blade. These techniques have been noted previously3.6). In the carpus, the first author (C.WM.) makes

for the instrument portal before placement

whereas, in other joints, it is made afterplacement and the position is then dictated by

When the arthroscopic procedure is completed, using anopen egress cannula and pumping fluid through the jointseffectively flushes debris from the joint. Typically, the larger,4.5 mm cannula is used so that all debris is removed (in thefemoropatellar joint a larger 6 rom cannula is used).

No sutures are required to close the joint capsule portals.One or two sutures are placed in the skin incisions. Onesuture is usually sufficient. The authors prefer a simpleinterrupted pattern to a cruciate pattern, to avoid invertingthe skin edge. In human arthroscopy, some authors havemade a case for not suturing skin incisions (Williamson andCopeland 1988). Cosmetic advantages have been proposedand some individuals believe hematoma or stitch abscessesare less likely to occur. Suturing is considered the saferalternative in the horse. Specific postoperative managementis discussed in the individual joint chapters.

The publicity associated with surgical arthroscopy hasovershadowed the use of the arthroscope in diagnosticevaluation of the joint. It is well recognized that traditionaldiagnostic methods used in the evaluation of joint disease(clinical examination, plain and contrast radiography, andsynovial fluid analysis) have definite limitations, particularlyin evaluating articular cartilage changes. The diagnostic use-fulness of arthroscopy in the evaluation of equine joint diseasewas documented in 1978 (Mcllwraith & Fessler 1978). Theuse of the arthroscope as a surgical decision maker in humanorthopedics is well established (Hots & Hoerbooms 1979). Asmentioned previously, however, arthroscopy is an adjunctivediagnostic technique and should not replace traditionaldiagnostic methods. The hazards of not evaluating a jointradiographically prior to arthroscopy are documented inman Goyce & Mankin 1983). As discussed in later chapters,

The tautness of the joint capsule and ligaments limits theability to examine certain joints or areas of certain joints.including the medial aspect of the antebrachiocarpal joint.the medial aspect of the patellofemoral articulation. andmuch of the femorotibial joint. Pitfalls of examining articularcartilage include over-interpretation. owing to magnmcation.and failure to recognize normal variations in morphology inthe joint.

obtaining both pre-and postoperative radiographs should bemandatory in equine arthroscopy.

Arthroscopy is valuable in assessing synovial membrane.articular cartilage. intra-articular ligaments. and menisci (inthe stifle). The ability to perform diagnostic arthroscopy ofparts of the equine femorotibial joints has furnished con-siderable amounts of new information and much progresshas been made in this area since the last edition of this text.

The usefulness of diagnostic arthroscopy in enabling theclinician to make a diagnosis when no other technique can doso is worthy of emphasis. These conditions include tears inthe cruciate ligaments as well as the medial palmarintercarpal ligament. meniscal injuries. and radiographically"silent" osteochondral fragmentation. subchondral bonedisease. and various articular cartilage lesions.

Observation of debris in thesynovial fluid

Before discussing specific examination of the synovialmembrane and cartilage, we should acknowledge thepresence of debris that is often noted on initial observation ofa joint before flushing. Usually, this debris is flushed out andis not further defined; however, some potentially valuableinformation may be lost. In a series of human kneearthroscopic cases reviewed by Mori (1979), debris wasfound in 46 of 732 joints examined. The author classified thedebris into four groups: precipitation of fibrin (14 cases);degeneration and necrosis of villi (20 cases); desquamation ofarticular cartilage (9 cases); and metaplasia of villi (3 cases).Necrosis of villi was considered to result from a cycle ofremission and recurrence of acute inflammation, such asrheumatoid arthritis. When remission of acute inflammationbegan at the root of villi as a result of steroid use, it inducedischemic necrosis at the periphery. Thinner and longer villihave a greater tendency to become necrotic. These ideasappear to be subjective and were not supported by histologicdata, but they may well provide an explanation for somefindings in the evaluation of horses.

Knowledge of normal anatomy

Before valid interpretations of changes in the joint can bemade, the surgeon must know the arthroscopic anatomy.This prerequisite, in turn, means relearning joint anatomy,which constitutes the first learning step in arthroscopy, be itdiagnostic or surgical. Knowledge of dynamic as well as staticanatomy is necessary. The surgeon needs to know thechanges that occur with variations in joint position.

Since embarking in arthroscopy, the authors have gaineda considerable amount of knowledge regarding jointanatomy, particularly with regard to the synovial membraneand other soft tissue structures (Fig. 3.10). In addition to thesmooth and villous areas, specific to certain sites in the joint,a number of normal plicae (folds) are present that have notbeen documented in equine anatomy texts. The positions ofthese folds are noted in later chapters.

Evaluation of synovial membraneand synovitis

The morphologic features of the synovial membrane and itsvilli can be visualized better with arthroscopy than byexamination of a gross specimen or during arthrotomy (Bass1984). When arthrotomy is performed, villi tend to cling tothe synovial membrane and cannot therefore be seendistinctly. In arthroscopy, because the observation isperformed in a fluid medium, the shape of the villi stands outdistinctly, and transillumination allows improved visual-ization of the villous vascularity. The magnification of thearthroscope also facilitates definition. The degree of magnifi-cation varies, however, depending on the distance of the objectfrom the end of arthroscope. If the end of the arthroscope is1 mm from the object, the magnification is 10 times; at a1 cm distance, no magnification is noted (Crane 1984).

The morphologic features of synovial villi in the horsehave been classified (McIlwraith & Fessler 1978). Thisclassification does not cover all possibilities, but some degreeof nomenclature is required to document various changeswith synovitis. Rather than use a simple classification system,

Inpathologic changes in the synovial mem-

carpal chip fractures are associatedwith Hemosiderosis may also be seen in thesynovial membrane.

Synovial membrane biopsy can be performed convenientlyby using the arthroscope. Although there are limitations inthe histologic evaluation of synovial membrane (McIlwraith1983), it is useful in the diagnosis of septic arthritis. Diagnosticarthroscopy and a biopsy sampling constitute a standardprotocol before lavage of infected joints. The degree ofsynovial proliferation and pannus formation and the presenceof articular cartilage compromise can also be assessed duringthis procedure. With biopsy of synovial membrane in anytype of diseased joint, it is important to realize that normalareas of synovium appear alongside areas of inflammation.For this reason, blind biopsy is considered to have limitedvalue and a biopsy under arthroscopic visualization is theonly worthwhile procedure. This opinion is supported byfindings of a recent study in man in which macroscopic signsof inflammatory activity in the synovial membrane variedconsiderably within a single joint (Lindblad & Hedfors 1985).In addition, a higWy significant correlation was found betweenthe local macroscopic (arthroscopic) signs of inflammatoryactivity and microscopic findings.

Although specific vasculature changes are considered tooccur in association with various arthritic entities and bloodvessels can be seen easily in normal villi, the conventionalarthroscope lacks the magnification for detailed observationof fine vascular structures. A magnifying arthroscope hasbeen developed and used in Japan (Inoue et al1979). Thedetails of the capillary network of the capsule and synoviumhave been better defined in this fashion (see Fig. 3.12B). Thevisual angle of the lens system is small and the visual fieldwith good focus is narrow. A preliminary investigation wasreported in which researchers used another microendoscopewith the ability to pass from panoramic vision to contact viewat four different magnifications, including microscopicobservation of vitally stained cells (Fizziero et al1986). Onthe basis of these preliminary findings, the authors thoughtthe capabilities of the device went some way toward bridgingthe gap between the conventional arthroscope, the lightmicroscope, and the scanning electron microscope.

The changes observed in experimentally induced synovitisare good examples of the sequential changes that occur insynovitis (McIlwraith & Fessler 1978). They highlight notonly the changes that can be observed but also the fact thatrepeated examinations provide a good dynamic under-standing of the synovial membrane. In this study, in whichsynovitis was induced by using filipin, hyperemia wassignificant initially. Petechiation of the villi and abnormaldevelopment of small hyperemic villi in the medial aspect ofthe carpal joint were frequent findings. Membranous fan-likeand cauliflower-like villi were seen in these joints, whereasthey do not appear in normal joints. In more severely in-flamed joints, fusion of villi across the joint and the presenceof fibrinoid strands and adhesion formation were evident.Chronic fibrotic changes were noted in the later stages, with

the arthroscopic surgeon needs to be able to recognize thesynovial pattern for specific areas of each joint. Definition ofabnormalities depends on a sound knowledge of the normaldistribution and characteristics of the villi. For example, inthe normal i.e. middle carpal joint, polyp-like filamentous villiare typical of the dorsomedial and dorsolateral areas of thejoint (see Fig. 3.10). In the far medial portion of the joint,the synovial membrane is smooth, white, and without villi.The presence and morphology of normal synovial plicae andthe normal intra-articular ligaments need to be known

(Fig. 3.11).The surgeon needs to recognize the many variations of

normal synovium that exist and the degree of change thatcan occur with minimal clinical compromise.

Synovitis manifests in a number of forms that have yet tobe completely characterized:

1. Hyperemia is typical of acute synovitis (Fig. 3.12). It maybe accompanied by some degree of edema and fibrin

deposition.2. Petechiation can be observed.3. Development of small, hyperemic villi in abnormal

locations.4. Thickening of villi and an increase in density of villi

(Figs 3.13 and 3.14).S. Formation of new types of villi (e.g. cauliflower-like villi).6. Atrophy of villi and total flattening of villous areas with

fibrin band deposition and adhesion formation.7. Formation of plump polypoid villi with detachment of

these masses to form "rice bodies".

Note also that some areas or pieces of light-colored avascularsynovium can often be mistaken for a loose body.

In a number of instances of traumatic joint disease, suchas cases involving carpal chips, chronic fibrotic changesdevelop in the synovial membrane. In these cases, however,the clinical signs may not differ from those noted in instances

Fig. 3.12(A) Hyperemic synovial villi in a case ofacute synovitis of the carpus. (8) View of

same area using magnifying arthroscope.

~.

villi becoming thicker and denser as the disease

the use of arthroscopy, new conditions can beStructures that are normal but have not

dorsomedial intercarpal ligament in the midcarpal

.This

often overlies a communication between the femoro-

joint and the medial femorotibial joint. In man." (contributing to symptomatology of the

a new clinical entity with the

of arthroscopy. This condition is not common and

assessment must be made to exclude other causes of

Levesque 1984). The most commonly

clinical situation is that of medial patellar plica

plica (Richmond &

1983, Nottage et al1983). A direct blow, repeated

or nonspecific synovitis may be the inciting event

to fibrosis and hypertrophy of the synovial plica.

occur as the plica bowstrings over the medial

the femur. Secondary chondromalacia may also

The authors still consider acquired plica-associated

a normal

structure is best exemplified in the horse by

and fibrosis of the dorsal synovial pad of the

3.15).

text, is that of synovectomy; its use in man was described byHighgenboten in 1982. It is frequently used in the horse tofacilitate the diagnostic process by allowing examinationof an otherwise obscure region. Synovectomy is greatlyfacilitated by improved soft tissue blades for motorized units(see Chapter 2).

Arthroscopic synovectomy has been performed in humanhemophiliac patients (Casscells 1987, Limbird & Dennis 1987).It reduced the frequency of bleeds and, with continuouspassive motion, arthroscopic synovectomy resulted in goodpostoperative motion (Limbird & Dennis 1987), and has beenshown more recently to be cost-effective in treating hemo-philiac patients (Tamurian et al 2002). Results of anotherstudy in man suggest intra-articular release of adhesions isefficacious in the management of arthrofibrosis of the knee(chronic stiffness of the knee) subsequent to previous operativeprocedures (Parisien 1988). Local synovectomy has beenused in human knees where hypertrophy of the synovium inthe anteromedial aspect of the joint following trauma hascaused mild chondromalacic change on the medial femoralcondyle and knee pain. Arthroscopic debridement of thispathologic tissue significantly improves symptoms (Chow etal2002). Equivalent indications may be found in the horse.Figure 3.16 illustrates hemarthrosis and the biopsy of a pieceof synovial membrane.

Potentially, clinicians could use synovectomy to treatequine conditions involving chronic synovitis. However,experimental work in the horse has questioned the beneficialeffects of synovectomy: Studies by Jones et al (1993, 1994)and Theoret et al (1994) have reported that arthroscopicsynovectomy in equine joint tissues has short-lived reversiblechanges on standard synovial fluid characteristics andclinical lameness. Both team of investigators reported thatregeneration of the synovial membrane was not apparent by30 days after arthroscopic synovectomy Gones et al1994)and incomplete by 120 days (Theoret et al 1994). These

Arthroscopic synovectomy

The remainder of this book deals in large part witharthroscopic surgery to correct various conditions of thejoint. One procedure that has been performed relatively littlein any equine joint. and is not addressed elsewhere in this

the mechanical and laser techniques were performed. Horseswere evaluated at 1. 3. and 6 months. Villous regenerationdid not occur in any horses after surgical synovectomy. Allsynovial membranes healed with a fibrous subintima and lesspopulated intima. The CO2 laser was capable of performing amore superficial synovectomy than that achieved withmechanical synovectomy using a motorized arthroscopicsynovial resector. The authors also cQncluded thatmechanical or CO2 laser synovectomy could be performed inthe horse. but additional evaluation was needed before thephysiologic significance of the lack of villous regenerationis known.

The authors of this textbook are concerned about capsulardefects and fibrosis following synovectomy. We recommendlocalized synovial resection to improve visualization. butcaution against using more generalized synovial resection asa therapeutic measure. at least in traumatic joint disease. Theuse of the resector for eliminating fibrin in infected joints isanother issue and is discussed in Chapter 14. Hemarthrosis ofthe synovial membrane is seen commonly in the carpal canalin association with radial osteochondroma and may beoccasionally seen in joints. Acute hemarthrosis is commonlyseen in the early stage of severe joint injury as also occurs inman (Butler & Andrews 1988).

Evaluation of intra-articular ligamentsand menisci

Arthroscopy has enabled veterinarians to diagnose otherwiseunrecognized lesions of the medial palmar intercarpal(Mcllwraith 1992) (Fig. 3.17; see also Chapter 4) and cranialcruciate (Walmsley 2002), meniscal (Walmsley 2002)ligaments and femorotibial menisci (Walmsley et aI2003).

studies were performed in normal equine joints whereas,obviously, many clinical applications of synovectomy occurin inflamed or infected joints,

Another study was performed to determine if arthroscopicsynovectomy had a beneficial or deleterious effect onarticular cartilage in equine joints with an induced synovitis(Paliner et al1998). The authors concluded that synovectomyin inflamed joints could be more deleterious to the articularcartilage integrity than inflammation alone and thatsynoveGtomy in normal joints has later effects (between 2 and6 weeks), which may be a response to the remodeling of thesynovial membrane after resection (Palmer et aI1998).

Another study compared synovial regeneration in theequine carpus after mechanical or CO2 laser synovectomy(Doyle-Jones et al2002). Twelve horses were randomly dividedinto three groups. The antebrachiocarpal and midcarpaljoints were randomly assigned to treatment so that eachhorse had one joint as a control (arthroscopic lavage), one inwhich a mechanical or CO2 laser partial dorsal carpal syno-vectomy was performed, and one in which a combination of

of articular cartilage despite normal radiographs. All the

of diagnostic arthroscopy is the evalu-

cartilage (Casscells 1984). Evidence ofchanges in the cartilage can be recognized

only when lesions extend into the sub-or over sufficient area to cause loss of joint

Many situations of cartilage compromise are lessthan this, but they may still represent significant

A recent study in people recorded chondral

lesions in 1000 consecutive knee

2002). The lesions were classifiedrecognized by the International Cartilage

Society (ICRS). Chondral or osteochondral lesions61 % of patients. Focal defects were found in

the patients and, in these individuals, 61 % related

.knee problem to a previous trauma. A con-

anterior cruciate injury was found in26% of patients, respectively. Mean osteochondral

2.1 cm2 and the main defect was found

58%, patella in 11 %,lateral

condyle 9%, trochlear in 6%, andtibia in 5% of patients. This study showed the pre-

horsesand,

wrinkled. and enfolded cartilage,probe could be inserted into the

addition to focal lesions, 4 of the 11horses had generalized damage to cartilage on the medialfemoral condyle. These focal cartilage lesions on the femoralcondyle were debrided. In 2 of 4 cases, debridement was notpossible; 6 of 7 horses with focal cartilage lesions treated bydebridement recovered completely and resumed previousactivities.

The arthroscope allows better detection of articularcartilage damage than gross visual inspection at post-mortem. Even superficial fibrillation can be recognized with

of various parameters rather

cartilage loss is also very common in the horse,associated with osteochondral chip fragments

carpus (Figs 3.18 and 3.19). Less severe changes-in the fetlock in association with chip fracture

3.20-3-22) and in most instances of osteoarthritisto osteochondritis dissecans. In most joints, the

reported as a cause of lameness in eleven horseset al 1997). Cartilage change was revealed at

the arthroscope because of the combined effects of fluidsuspension of the fibrillated collagen fibers. magnification.and transillumination (see Figs 3.18 and 3.20). Partialthickness and full thickness erosions represent more severechanges in the articular cartilage (Fig. 3.20-3.27). Diseaseinvolving the subchondral bone can also be recognized(Fig. 3.27 and 3.28). Other entities of cartilage damage. suchas wear lines. are also recognized with the use of diagnosticarthroscopy (Fig& 3.29 and 3.30). The significance of thesechanges is discussed in later chapters. The use of instrumentsto define the size of the lesion is also important. Methods ofdebriding cartilage defects are dealt with in Chapter 17.

Before the advent of arthroscopic S\lfgery. the first author(C. W.M.) performed diagnostic arthroscopy on joints toascertain further the potential value of surgery (such as

instrumentation, care must be made to avoid contact withthe cartilage.

Thermal chondroplasty with radiofrequency energy (RFE)has garnered widespread interest over recent years. There aretwo systems available for clinical application: monopolar RFEand bipolar RFE (Lu et al 2002). Evaluation of both types ofinstrument on fresh osteochondral sections derived frompatients undergoing partial or total knee replacementrevealed that the depth of chondrocyte death in the mono-polar RFE treatment group was significantly less than in thebipolar group. The authors pointed out that there could besignificant chondrocyte death. The study also showed that ittook at least 15 seconds for both bipolar and monopolarRFE to contour a 1 cm2 chondromalacic cartilage defect to arelatively smooth surface as shown by scanning electronmicroscopy (Lu et al2002). The investigators concluded thatwhen thermal chondroplasty was applied clinically, it couldresult in various degrees of cartilage smoothness andpotentially significant chondrocyte death.

The case for the use of lasers has also been made in joints(Palmer 1996). However, evaluation in clinical cases hasrevealed unwanted subchondral bone necrosis when anarticular cartilage lesion is debrided.

Arthroscopic lavageand debridementThe usefulness of lavage in traumatic arthritis had beenclaimed prior to arthroscopic surgery becoming routine(Norrie 1975). The adjunctive lavage that goes witharthroscopic surgery has always been considered beneficial.although there is no clear documentation of this effect. How-ever, the benefit of partial thickness chondrectomy wherethere is cartilage fibrillation or minor exfoliation is more

Electrosurgery using high-frequency (HF) equipment(described in Chapter 2) has been used in both human andequine arthroscopy. One of the authors G.B.) has used it quiteextensively in the horse. In humans. in addition to surgery onthe synovial membrane and joint capsules, most arthroscopicmeniscal surgeries are routinely done with the electroknife byat least one group (Kramer et al1992). When using such

3.31). The use of such debridement along, C C but controlled

of the rabbit patella with no evidence ofin either the superficially or deeply shaved areas--& Shephard 1987). Ultrastructural studies after

cartilage shavings question knee regenerationSchmid 1987). A

trial of arthroscopic surgery for osteoarthritisknee in humans caused considerable controversy

2002). The authors concluded that the out-

books, attending seminars, and viewing video recordings."Hands on" training and practice, however, is essential.Instruction and practice on cadavers is the most commonway veterinary clinicians have improved their skills beforeembarking on clinical cases. Animal cadavers have also beenused in the training for arthroscopy in humans (Voto et al1986); however, artificial models have also been usedsuccessfully. More recently, there has been some developmentof equine artificial bones with joint capsules, but at present,cadaver material is inexpensive and readily available.

An interesting prospect for the future is the developmentof computer-based simulations of arthroscopic surgeryfor training and testing of arthroscopic skills (MedicalSimulations. Inc.. Williamstown. MA). Use of simulators willincrease particularly in learning human arthroscopictechniques. There will probably be less use in the horse wherecadaver material is still more available.lavage and debridement of osteoarthritic

based on the severity of degeneration, continues to

horse. the authors feel that lavage is an importantpart of arthroscopic procedures by reducing

References

cartilage. A useful rule is that if articularis attached to subchondral bone it should be left

Second look arthroscopies provide an opportunity tothe amount of healing that has occurred in

3.32).

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middle carpal (intercarpal) or ante-surgical procedures and initially served

portal for each joint. Using two dorsal

1983. 1984. Mcilwraith et al

surgery and the earlier return to exercise,

rather than continuing trainingmedication to the detriment of joints and

was the

arthroscopy in the carpal joints as well as aof case selection, adjunctive management, and

can be anticipated. In most instances, theare common to all joints, but they are

of arthroscopic surgery. The key to successfulis attention to detail and authors will

throughout the small features that are

of movement because of reduced soft tissue tension aroundthe arthroscope and a reduced tendency to slip out of thejoint when examining areas close to the arthroscopic portal(Martin & McIlwraith 1985). Two portals are also useful ifsurgery is going to be performed on both sides of a joint. Inaddition, villi in the area of arthroscopic entry willsometimes compromise visualization in that area of the joint.Examination through one portal has been greatly facilitatedby the development of the angled-view arthroscope. It isimportant always to evaluate the whole joint beforecommencing surgical manipulation. For example, if the pre-surgical diagnosis is that there is fragmentation of the distalradial carpal bone, the arthroscope is placed dorsolaterallyand once a clear view is obtained, a quick examination of allthe potential areas for injury can be made. If the onlyarthroscopic finding is the chip on the distal radial carpalbone, then this is removed through a dorsomedial instrumentportal. On the other hand, if the examination also reveals afragment on the distal intermediate carpal bone, then afterremoval of the radial carpal chip, the arthroscope andinstrument are swapped as the fragment on the intermediatecarpal bone can be more conveniently visualized andremoved using a dorsomedial arthroscope portal and adorsolateral instrument portal.

It is also possible to insert the arthroscope into the lateralpalmar outpouchings of both middle carpal and antebrachio-carpal joints as well as medial outpouching of the ante-brachiocarpal joint. The most common indication for surgeryis removal of fragments from the palmar aspect of the joints,but this approach has been used to retrieve a broken pieceof instrument (McIlwraith 1990, Dabareiner et al 1993,

Wilke et aI2001).Due to the anatomic differences, examination and surgery

of the middle carpal joint is easier than the antebrachio-carpal joint: whereas the middle carpal joint tends to open asa hinge, the antebrachiocarpal joint is shaped so that itsmovement is both rotational and gliding. The glidingmovement of the joint tends to tuck the dorsal edge of theradius beneath the joint capsule and the joint capsuleattaches closely to the proximal marginal edge of the inter-

and prognostic procedure (Mcllwraith &~.. Mcllwraith 1991) as well as for the surgicalof articular injuries. The general role of the

arthroscopic anatomy of the carpal joints is

mediate and radial carpal bones. In addition, the convexcurvature of the distal medial and lateral aspects of the radiusmake access to the medial and lateral joint angles slightlymore difficult. The narrow angle between the radius and theproximal radial carpal bone in the medial aspect of the jointcan also make instrument manipulation more difficult inthis area.

The general technique for introducing the arthroscopeinto the joint was described in Chapter 3. Two arthroscopicportals are useful for either the middle carpal or antebrachio-carpal joint: dorsolateral and dorsomedial. The lateralapproach is better for visualizing the medial aspect of thejoint and the medial entry is better for seeing the lateralaspect. For example, when the operation involves a lesion onthe medial half of the joint, the instrument is introducedthrough the medial portal and the arthroscope entersthrough the lateral portal and vice versa. Thoroughexploration of the carpal joints is therefore possible by usingboth lateral and medial entries.

Although arthroscopy in the carpal joints can beperformed with the animal in lateral or dorsal recumbency,the latter has greater versatility. When switching sides withthe arthroscope (as is usually necessary if lesions are on bothsides of the joint), rolling of the horse or doing surgery"upside down" is necessary if it has been placed in lateralrecumbency. Some surgeons have suggested that the dorsalrecumbency position causes tightening of the joint capsuleover the dorsal face of the carpus, and that a loose fragmentcan be located more predictably in the lateral or medialcul-de-sac of the joint when the animal is in lateralrecumbency. However, the authors have not found these to belimiting factors and in reviewing arthroscopic surgicalprocedures performed on 1000 carpal joints in 591 horses bythe first author (C.W.M.) 45% were operated bilaterally. Forthis reason, all descriptions of both diagnostic and surgicalarthroscopy in the carpal joints are presented as in dorsalrecumbency, i.e. proximal is below and distal is above. Thisposition is also taught in the authors' laboratory classes.Learning arthroscopic anatomy in this manner is an importantprerequisite to performing arthroscopic surgery. Positioningand preparation of the carpus are illustrated in Chapter 3.

Initially, the most important aspect is to learn the specificlandmarks that allow orientation within the carpal joints andthese are described in the examination techniques below.

sheaths. By contrast, the periarticular anatomy offetlock, tarsocrural, and femoropatellar joints allows rliberties with placement of the portals, and prior jdistention is an asset to localization of the correct portal

After joint distention, the arthroscope is inserted int(joint as described in Chapter 3. Examination witharthroscope inserted through the lateral portal commewith the visual field in the medial aspect of the middle c~joint (Fig. 4.1). The dorsomedial intercarpal ligaIJextending from the dorsal medial aspect of the radial c~bone to the medial joint capsule is commonly obse(Fig. 4.1C). This dorsomedialligament has been previcdescribed as a synovial plica (Mcllwraith 1990). Withdralthe arthroscope and angling the lens proximad aUinspection of the articular surface and dorsal margin ojradial carpal bone (Fig. 4.2). Continued withdrawal ofarthroscope allows visualization of the junction betweerradial and intermediate carpal bones (Fig. 4.3). Rotati(the arthroscope allows inspection of the palmar aspect 0joint and the articulation between the radial, intermedand third carpal bones (Fig. 4.3C). Also in this view i!synovial fossa in the medial palmar aspect of the third c~bone and the medial palmar intercarpal ligament (MPThis fossa is normal; it is a site of communication wittpalmar pouch of the middle carpal joint, and may be a sitlodgment of small particles that break free during artscopic surgery. During examination of the articular millof the radial and intermediate carpal bones, the joint caIattachment is some distance from the articular rim, all01excellent visualization of the dorsal margins of these bol

The arthroscope is advanced slightly and the arthros(lens is angled distad to visualize the second carpal bonethe medial portion of the third carpal bone (Fig. 4.4). Swithdrawal allows additional visualization of the remaidorsal margin and body of the radial facets of the third c~bone (Fig. 4.5). If the arthroscope is then moved so thatip sweeps laterad and the eyepiece mediad, the intermelfacet of the third carpal bone and the more central aspe(the joint can be visualized (Fig. 4.6). By continuingmotion, the lateral aspect of the intercarpal joint cavisualized. (These areas are illustrated here, using the m

arthroscopic approach.)When the arthroscope is inserted through the d(

medial portal the tip is passed to the most lateral aspect 0joint where the angle formed by the ulnar and fourth c~bones is visualized (Fig. 4.7). Withdrawal of the arthrospermits evaluation of the articular surfaces of the ulnarintermediate carpal bones as far as the junction of the Iwith the radial carpal bone (Fig. 4.8). A similar manewith the lens directed distad and palmad allows examin.of the fourth carpal bone (Fig. 4.9) and the lateral half 0third carpal bone (Fig. 4.10). There is also a synovial plicathe transverse dorsal intercarpal ligament at the juncti(the third and fourth carpal bones (Fig. 4.10C).

Additional maneuvers may be necessary to augmenexamination. For example, for detailed examination ojdorsal synovial recesses beyond the articular surfaces, ttof the arthroscope may be placed between the dorsal sur

Arthroscopic examination of themiddle carpal (intercarpal) joint

The choice of arthroscopic portal depends on the primaryarea the surgeon wishes to examine. The lateral portal ishalfway between the extensor carpi radialis tendon and thecommon digital extensor tendon and midway between thetwo rows of carpal bones with the joint flexed at approxi-mately 70°. The medial arthroscopic portal is made sufficientlymedial to the extensor carpi radialis tendon to avoid itstendon sheath. The skin incision for these portals is madebefore distention of the joint to avoid damage to the tendon

Diagnostic Arthroscopy of the Carpal joir

,/./

,/

/''"

R

Fig. 4.2Distal radial carpal bone (R). (A) Diagram of arthroscopeposition and visual field. (8) Arthroscopic view; 2. Second carp,bone; 3, Third carpal bone L, medial palmar intercarpal ligamer4, fourth carpal bone. I, Intermediate carpal bone; U, ulnar

carpal bone; CD, common digital extensor tendon; ECR,extensor carpi radialis tendon.

of the carpal bones and the capsular reflections. Synovial 1in the dorsomedial and dorsolateral aspects of the joint nobscure the view of some parts of the dorsal rims of the boldespite joint distention. In these cases, use of an instrum,to push them out of the way is appropriate.

Arthroscopic examination of theantebrachlocarpal (radiocarpal) joint

~

Arthroscopic examination of the antebrachiocarpal jointconducted in the same fashion as for the middle carpal jobexcept that the flexion angle in the carpus is decreased (legextended to 120-130°). The leg is straightened to facilitcmaximal visualization of the dorsal aspects of the radial aJ

Fig. 4.1Medial aspect of the middle carpal joint. (A) Diagram of

arthroscope position. (B) Arthroscopic view. R, radial carpalbone; 2, second carpal bone; 3, third carpal bone; CD,common digital extensor tendon; ECR, extensor carpi radialistendon. (C) Closer view of field in B. P, Normal synovial plica

(dorsomedial intercarpal ligament).

,,19 Diagnostic and Surgical Arthroscopy of the Carpal joints

Fig. 4.4Second carpal bone (2) and the medial aspect of the third car~bone (3). (A) Diagram of arthroscope position and visual fie(B) Arthroscopic view. (C) A more palmar view of the thirdcarpal bone. including the fossa at the medial palmar aspect I

the junction of the second (2) and third (3) carpal bones aswell as the medial palmar intercarpal ligament (L). Also notethe median ridge of the third carpal bone dividing radial andintPrmprJi"tP f"rpt.

Fig.4.3Junction of the radial and intermediate carpal bones.(A) Diagram of arthroscope position and visual field. Dorsal(B) and palmar (C) arthroscopic views. R, radial carpal bone;I, intermediate carpal bone; medial palmar intercarpal ligament.

1111_i,

joints

R

--

A'-

Fig.4.TUlnar (U) and intermediate (I) carpal bones. (A) Diagram of a~roscope position and visual field. (8) Arthroscopic view.Intermediate facet of the third (3) carpal bone.

Fig. 4.8Distal articular surface of the intermediate carpal bone (I). (A)Diagram of arthroscope position and visual field. (B and C)Arthroscopic views. Note the edge of the radial carpal bone(R) and synovial plica (P) between intermediate and radial

carpal bones. $, synovial membrane.

A

carpal bones and distal radius (and this is

As in the middle carpal joint. the dorsolateral arthroscopicC is halfway between the common digital extensor and

extensor carpal radialis tendons. and the dorsomedialportal is medial to the extensor carpi radialis tendon. Thechoice of portal depends on the area of primary interest withrespect to visualization and (usually) surgical intervention.The site of the medial portal is at the center of a triangleformed by the extensor carpi radialis. the distal rim of theradius. and the dorsal rim of the radial carpal bone. Thisportal area is in the smallest space in either of the carpaljoints and because of marked narrowing of the joint. thetight nature of the capsular attachments. and the convexnature of the articulation. the surgeon has to be careful wheninserting the arthroscope to avoid excoriation of the articular

cartilage.

Arthroscopic examination of the antebrachiocarpal jointwill be described, beginning with the arthroscope insertedthrough the lateral portal and visualization of the medial sideof the joint. The distal radius and the proximal radial carpalbone form the medial joint angle. Rotation of the lens distadallows close inspection of the medial portion of the proximalarticular surface of the articular surface of the radial carpalbone (Fig. 4.11). Withdrawing the arthroscopic slightlyallows examination of the entire proximal radial carpal boneto the level of its junction with the intermediate carpal bone(Fig. 4.12).

The arthroscope is then rotated so that the lens is angledproximad to examine the medial aspect of the distal articularsurface of the radius (Figs 4.13 and 4.14}. As in the middlecarpal joint. the lateral aspect of the joint can be examinedthrough the same lateral arthroscopic portal by moving the

eyepiece mediad and the tip laterad and then rotating tscope appropriately. For purposes of palpation and surgehowever, examination of the lateral aspect of the joint is bperformed through a medial arthroscope portal.

By switching to a medial portal, the most lateral aspectthe antebrachiocarpal joint is examined. The arthroscoP(rotated wit!1 the lens pointed distad to visualize the proxinarticular surface of the ulnar carpal bone and the lateaspect of the proximal articular surface of the intermedi:carpal bone (Fig. 4.15). Withdrawing the arthroscope alloexamination of the entire proximal surface of the intmediate carpal bone (Fig. 4.16), and tilting of the arthroscotip distad allows inspection of the junction of the intermediand radial carpal bones (Fig. 4.17).

By returning the tip of the arthroscope to the lateaspect of the joint and rotating the arthroscope so that 1

lens is directed proximad, the lateral aspect of theradius can be examined (Figs 4.18 and 4.19). On alateral view, the articular groove between the lateral sprocess and the distal epiphysis of the radius (fused iadult) can be seen; in a young horse, it can be seencompletely separated fissure. With withdrawal and rotithe entire lateral half of the joint can be scanned. inCllthe midsagittal ridge of the distal radius (Fig. 4.19C). Grin the central portion of the radius are commonly obsand are considered normal.

As mentioned with the middle carpal joint. addilmaneuvers may be necessary in some joints to faccomplete examination of the dorsal articular surincluding use of instruments to retract the villi and chaJthe flexion angle of the joint.

examination of the palmarmiddle carpal and

joints

the antebrachiocarpal joint, the swelling is proximalthe perceived joint line. A No. 11 blade is then used to crea portal and the arthroscope can be inserted. Figures 4.2and D show arthroscopic views of the lateral aspect intopalmar aspect of the middle carpal and antebrachiocarjoint. respectively.both middle carpal and antebrachiocarpal

.

surgery is removal of frag-

Maintenance of joint distentionbeen used to retrieve a broken piece of instrument

1990. 1996, Dabareiner et al1993, Wilke et al The arthroscopist must direct the operation to ensure 1maintenance of joint distention. This is not usually a problat the time of initial examination when the only patent pOIis that for the arthroscope. If an egress cannula is placedthe other side, varying the closure of the cannula still ea~controls distention. However, once there is a patent instl

The position for placing the arthroscope in the lateral

front. swelling will be revealed. In the case of

ment portal and instrument manipulations have bperformed. some flow of fluid from the joint is inevitablethis requires an increased rate of fluid input to main!distention. Once an instrument portal is losing flui(number of aspects are important to avoid the developmersubcutaneous fluid accumulation. Placing a finger overskin incision to stop fluid flow will only promote filling insubcutaneous plane. Similarly. pumping fluid when a chbeing pulled through the subcutaneous tissue and skinmay block the skin outlet and cause fluid to collect 1cutaneously. Fluid ingress should also be minimized dillinstrument manipulations because these can facilitateopening up of the subcutaneous tissue planes. again allO\lfluid extravasation.

Another problem. once an instrument portal is mad,that if the joint must be re-entered with the arthroscope; Ijoint distention is present to facilitate re-entry. This is Dcommonly encountered with biaxial fragmentation. mechips requiring a lateral arthroscope and medial instrunportals and lateral chips requiring medial arthroscopelateral instrument portals. The reinsertion of the arthros(requires experience and care to avoid iatrogenic damagthe cartilage. The arthroscopic sheath and conical obturare manipulated carefully back into the joint. the arthros(is inserted. and the joint is redistended. The use of "switclsticks" in human arthroscopy to facilitate these maneuhas been described Gohnson 1986). but the authors be!these are not necessary in the equine carpus. Removingarthroscope from one portal and placing it in another 1consequent escape of fluid is usually associated with Slbleeding and the joint will need to be flushed bevisualization is satisfactory.

Arthroscopic Surgery forRemoval of Osteochondral

Chip Fragments

Current status and advantages ofarthroscopic surgery

The feasibility of returning horses to racing more qujafter arthroscopic removal of carpal fragments brolarthroscopic surgery into strong demand. Some ofadvantages of arthroscopic surgery have been simplifiedoverstated. but it is now universally adopted for treatmelcarpal fragmentation.

On the basis of a review of 1000 arthroscopic procedfor removal of carpal chip fragments (Mcllwraith et al19and continued experience since then. a number ofadvantcan be listed. Many of these are applicable also to other jo

1. Visualization is superior to that with arthrotomimproves diagnostic accuracy and. consequently. r.definite treatment.

to periarticular tissues and the joint 6. Horses return to training earlier and thus less fitness amusculoskeletal adaptation are lost. These factors contriblto an earlier return to racing.

only is the cosmetic result excellent but also, to overall joint function is minimized.

trauma to the soft tissues is also significant tothe articular cartilage, which may undergodeterioration secondary to soft tissue

Problems and poor results have been encountered, and ;addressed at appropriate points throughout the chap1Many small problems can be avoided by technique changand one of the main purposes of this textbook is to stlthe beginning arthroscopist past some of these pitfaUnfortunately, poor results can often be related to inadequ;ability, experience, or practice. To be able to operate effectivon any carpal chip lesion using arthroscopic surgery i~reality, but it requires skill and practice. Above all, it arequires a disciplined systematic approach. The techniqlpresented in this chapter are not the sole meansperforming surgery; however, whatever changes the surgemakes, he or she should still use a systematic approach

the joint (with elimination of

on multiple joints can occur in the same

race successfully in the same or a higher class. Alowering in class. however. is more typical for

racehorses after arthrotomy.

every case. The approaches described have worked for theauthors and also for the veterinarians who have undertakenthe arthroscopic training courses that the authors have con-ducted worldwide (Mcllwraith 2002). Modification andrefinement of techniques continue and it is the authors'philosophy to disseminate this information through trainingcourses and publications.

Presurgical information

As with any surgical candidate, as complete a history aspossible is obtained. This history is often difficult withracehorses, and duration or time that the chip fracture hasbeen present is often not clear. Treatment history frequentlyis uncertain, particularly with reference to intra-articularcorticosteroid medication, but the authors feel less concernedwith operating on horses soon after corticosteroid adminis-tration than was the case with arthrotomy.

In most cases, the horses exhibit mild to moderatelameness. Severe lameness is usually associated with majorarticular damage. Radiographs should always be taken ofboth legs; bilateral and/or clinically silent lesions arecommon and these frequently are in the same location inboth limbs. There is also a lack of correlation between radio-graphic and arthroscopic findings, which is usually reflectedin arthroscopic findings that are more severe than thosesuggested by radiographic examination (Mcllwraith et al1987). The same disparity was noted in human osteo-arthritic knees (Lysholm et al198 7). Specific problems in thisregard with chip fractures at various sites in the carpal jointare addressed in the appropriate section.

"fragment" rather than "fracture" for the osteocholpieces that are created. Such fragments almost invaroccur as a consequence of microdamage and thus couclassified as pathologic fractures. In some instances the IIappears as a "fresh" fracture line through an artilsurface with no visible subchondral change, but ininstances subchondral disease is seen arthroscopicallycertainly exists at the microscopic level.

Osteochondral fragmentation has direct physical effecthe joint because of the loss of the smooth articular suand indirect effects due to the release of articular car1and bone debris, which leads in turn to synovitis. S,compromise of the articular surfaces leads to instabilidoes tearing of fibrous joint capsule and ligaments.synovial membrane responds directly to mechanical tr.and indirectly to injury elsewhere in the joint. High iarticular pressures generated by synovial effusionpromises the microstability, and the normal, slightly ne~atmospheric pressure in joints is lost. Damage to synovioalso liberates matrix metalloproteinases, aggrecalprostaglandins, free radicals and cytokines (princiinterleukin 1 or 11-1), which could lead to articular carldegeneration (McIlwraith 1982). Chronic articular iresults in fibrosis of the joint capsule and consequent IImotion. Arthrofibrosis is recognized as an important prcin humans. The cause is still unknown, but the use of sarthroscopic techniques is considered critical inminimization of arthrofibrosis in man (Finerman & ~

1992).The primary indication for surgical treatment of c

chondral fragments in the carpus is to minimize artiinsult and to prevent development of osteoarthritis(McIlwraith & Bramlage 1996). It should be recognizeca joint is rarely returned to "normal" and that signiJdefects can potentially lead to some degree of microinstaand progression to osteoarthritis. Nonetheless, relative jamount of damage, the athletic horse can come back t(level performance despite some damage.

Relevant pathobiology

Location of intra-articular fragmentsTable 4.1 illustrates the incidence and location of (chondral fragments in the dorsal carpal joints as reportthe first author (C. WM.) in a series of 1000 carpal"(Mcllwraith et al 1987). The affected joints were inhorses, of which 220 were racing Thoroughbreds. 349racing Quarter Horses. 5 were racing Appaloosas, and 6racing Standardbreds. The others included 2 barrel-rQuarter Horses, 3 roping Quarter Horses, and 6 other Ihorses.

Of the 591 horses. 278 horses were 2 years old, 1963 years old, 52 (55%) were 4 years old, 47 were 5 ye,older, and 18 did not have their age documented. Inhorses, osteochondral fragments were noted in one cawhereas 265 (45%) horses had bilateral lesions. Arthro~surgery was performed on a significantly greater numljoints per horse in Quarter Horses compared with Thor(breds. Specifically, in the Thoroughbreds, operations inv

The carpal and fetlock joints are the most common instanceswhere traumatically induced osteochondral chip fragmentationoccurs. Although chip fragments have been frequently con-sidered as acute injuries and present with acute clinical signs,it is now recognized that many of these fragments come frompathologic joint margins, previously altered by subchondralbone disease (Pool & Meagher 1990), and more recent workin the first author's (C. W.M.) laboratory has documented thedevelopment of microdamage in association with exercise.The microdamage manifested as a combination of microcracks,diffuse microdamage, cell death, and subchondral bonesclerosis (Kawcak et al 2000, 2001) and it is suggested thatsuch changes lead to the clinical osteochondral fragmentationseen in the carpal and the fetlock joints.

It has been proposed that chip fractures of the jointmargins in the carpus can arise from either fragmentation ofthe original tissue of the joint margin (previously altered bydisease as mentioned above), or within the base of peri-articular osteophytes forming in joints as part of the osteo-arthritis syndrome. Experience with arthroscopic surgery ofcarpal fragmentation suggests that both mechanisms occurand for this reason, the authors now prefer using the term

Arthroscopic Surgery for Removal of Osteochondral Chip Fragmem

1 joint in 142 horses. 2 joint in 70 horses, 3 joints in 14horses, and 4 joints in 1 horse. In the Quarter Horses, 1 jointin 144 horses. 2 joints in 130 horses, 3 joints in 46 horses.and 4 joints in 30 horses were affected (Mcllwraith et al

1987).Unpublished data from a European author (I.M. \1\7:) suggests

a similar distribution of lesions, although the relativefrequency of fragments from the proximal third carpal boneand distal intermediate carpal bone are reversed. Readers arealso cautioned that lesion distribution may vary in otherpractices in which breed/use manipulation is different.

General technique for carpal chip removal

As discussed briefly in Chapter 3, surgery is performed byusing the technique of triangulation (see Figs 4.21-4.23).Specific details on the arthroscopic and instrument approachesfor operations involving chip fractures in different locations

Distribution of carpal chip fragments.

47510660

641

540 intercarpal (midcarpal) jointsDistal radial carpal boneDistal intermediate carpal boneProximal third carpal boneTotal

460 Radiocarpal (antebrachiocarpal) jointsDistal lateral radiusDistal medial radiusProximal radial carpal boneProximal intermediate carpal boneProximal ulnar carpal boneTotal

16796

168273

1705

Fig. 4.22Removal of a carpal chip fragment from the intercarpal joint

using Ferris-Smith cup rongeurs: (A) grasping of the fragment(B) removal of fragment through the skin.

Source: Mcllwraith et al1987

with a closed egress needle (A) and a probe (B) to evaluate the mobility of a carpal chip fragment

are included in subsequent sections, but the general rule isthat for a fragment on the medial side of the joint, thearthroscope passes through the lateral portal and theinstruments enter through a medial portal. For lesions on thelateral side of the joint, the arthroscope is placed through amedial portal and instruments through a lateral portal.

The basic protocol for surgery of all carpal fragmentationis similar. A diagnostic arthroscopic examination is alwaysperformed first. The egress is opened to flush the joint ifvisualization is less than optimal. When the view is clear, theegress is closed and can then be used to palpate areas offragmentation (see Fig. 4.21A). Alternatively, a probe can beused (see Fig. 4.21B), but the egress works well for pre-liminary palpation and saves an extra instrument passage.

The egress cannula is then removed and the instrumentportal through the joint capsule usually closes, at least untilthe time that a larger instrument (which increases thediameter of the portal) is used. If the fragment is fresh andmobile on palpation, immediate insertion of grasping forcepsis appropriate. The fragment is grasped, and the forceps arerotated to free the chip of soft tissue attachments (if these are

sIgnmCarn) , oelore II IS removea ~see ng, ':I:.L.L.). l'ems-~arthroscopic rongeurs are most commonly employed. jsize is chosen to enclose the fragment as completepossible to minimize loss, as this is brought through thecapsule, subcutis, or skin (see Fig. 4.22). Rongeurs wjaw size of 4 x 10 mm are suitable for most fragmen1locations. Tearing a fragment loose from its soft tattachment by twisting the forceps may not see Iaesthetically pleasing or relate well to basic surprinciples, as sharp severance of the attachments, I:minimizes the risk of creating a free-floating fragment.

If attachments at the fracture line are strong all(fragment cannot be displaced with initial probing, a :Synthes or Mcllwraith-Scanlan elevator is used to septhe chip from the parent bone (see Fig. 4.23). Also, whechip has considerable fibrous capsular insertions, as typoccurs with fragmentation of the distal lateral radiuselevator or a fixed blade arthroscopy knife can also be usseparate these attachments before removal of the fragwith forceps.

Although rarely necessary, when a chip is long-starand bony reattachment is developing or has developelosteotome may be used to free the fragment from the p,bone. The osteotome is positioned through the instruportal and is placed in the old fracture line by the surusing arthroscopic visualization. An assistant strike:osteotome according to the surgeon's direction. A Iosteotome or an elevator and hammering is preferredsharp osteotome by some surgeons as it is thought to blikely to make a new fracture line through normal bonFoerner pers comm 1984).

In many cases of chronic fragmentation, Ferris-5rongeurs are used to remove the fragments directly wi1prior separation. This usually works well, but attemrremove normal bone in this fashion may break the pin lirof the forcep blades. If there is extensive bone prolifer.the use of a motorized burr for debridement of lesions c:considered, but such indications are rare, and the valsurgery in such cases is always questionable.

Once fragments are removed, the defect is debrided.step is discussed in detail later and is usually performedrongeurs and curettes (Fig. 4.24). Other osseous defect:may be debrided at this time. Kissing lesions are evalubut when they are of partial thickness, they usually ardebrided.

The joint is then flushed by opening the egress carand manipulating the tip in the area of the lesion (Fig. 4The egress can also be used to rub off small tags of carland bone. Placement of the larger, 4.5-mm egress carshould follow, to remove larger fragments (Fig. 4.25). Sumay be applied to this cannula, but it is not routinely perfoin the carpus. Lavage should continue until the joimacroscopically cleared of debris. Occasionally, a fragmigrates away from the fracture site and is either free floor attached to synovial membrane (Fig. 4.26). In such (it is removed with forceps.

At the completion of irrigation of the joint, the portaclosed by using skin sutures only (Fig. 4.27). The incisior

Arthroscopic Surgery for Removal of Osteochondral Chip Fragmel

(A) external view. (8) arthroscopic view.

Fig. 4.25Arthroscopic view of flushing debris from central area of middle carpal joint. (A) External view. (8) Arthroscopic view.

Fig. 4.26Free fragment in the joint (A) and adhered to synovial membrane (8).

grasped. Any soft tissue attachments to the fragment illsevered while the fragment is held with forceps or a tOWIclamp. Occasionally, insertion of the arthroscope intsubcutaneous pockets. with either no or little fluid flow, caassist in location of fragments.

Specific sites of carpal chipfragmentation and their treatment

Dorsodistal radial carpal bone

The dorsodistal aspect of the radial carpal bone is the mocommon site for carpal fragmentation. It is the easieoperative site in the carpus, but has the greatest range Ipathologic change seen at arthroscopy relative to whatseen on radiographs. The arthroscope is placed through tllateral portal with the lens-angled proximad and the instrlments are brought through the medial portal (Fig. 4.29Fragmentation can occur anywhere along the distal dorsmargin of the radial carpal bone.

covered with a sterile nonadhesive dressing and adhesivegauze, before an elastic or padded bandage is applied(Fig, 4.28).

The size of fragments that can be removed arthro-scopically has no limit. The skin incision has to be extended insome instances but additional incising of the joint capsule isnot usually required. Failure to lengthen the skin incision canresult in the fragment being lost or trapped in the subcutis. Inexceptional cases, a single absorbable suture may be placedin the joint capsule after removal of a particularly large

fragment.Postoperative or intraoperative radiographs to ensure

removal of all fragments are recommended. Although it isimportant that no loose fragments remain in the joint, someosseous densities in the radiographs may not be candidatesfor removal. In addition, osteophytes away from the articularmargin and within the joint capsule (or enthesophytes) are ofless concern. For any fragment or spur completely buriedwithin the joint capsule, dissection out of the capsule isunnecessary and is excessively traumatic. The surgeonshould be certain that such fragments are indeed outside thejoint cavity and it is important to recognize that one shouldtreat the patient rather than the radiograph. Veterinariansinvolved in obtaining follow-up radiographs of arthroscopicsurgery patients should also be aware of this principle beforeproclaiming to the client or the trainer that "a chip has beenleft in the joint."

If radiographs reveal evidence of a fragment remaining inthe joint, further arthroscopic examination is performed.When a fragment has lodged subcutaneously, the area ispalpated and swept with a pair of hemostats. When thefragment is located, it is brought to the skin incision, and

and flexed lateromedial views and dorsolateral-

lateromedial radiographic view has been used tobone loss. it is

at this site is particularly poor. In addition. chiphave been found on the distal radial carpal bonenot visualized on any of the radiographic views.these fragments are on the dorsolateral corner of

projected in

As with any chip fractures, the size of distal radial carpallesion varies widely. The smallest lesions manifest

in the distal dorsal margin (Figs 4.31 and 4.32),examined arthroscopically, such lesions usually

.-,,- .'. '.31Band

loss vary considerably. Loss of bone is typically related t<finding soft defective bone at surgery. which requires debridement. Such changes in the distal radial carpal bone can btsevere when the radiographic changes appear rather mildOften the degree of clinical compromise (lameness an,synovial effusion) is a better indicator of the state of the join1than are the radiographs. The presence of bloody or brownsynovial fluid on initial entry into the joint is also usually a

Larger osteochondral fragments are easily identified."(Figs 4.33 and 4.34). At arthroscopy, the

33). There is also

particularlypalmar to the fragmentation (Fig. 4.33). Grading degree ofarticular cartilage damage is discussed more fully in asubsequent section.

Radiographs also do not often predict accurately the extentof bone fragmentation in the distal radial carpal bone. Boththe amount of cartilage degeneration that extends back fromthe edge of the defect and the amount of subchondral bone

(Fig. 4.37). After removal of fragmentation, detac]cartilage is removed and exposed subchondral bone debrito healthy margins (Fig. 4.38).

The prognosis is related to the amount of cartilage anibone loss and decreases with loss of bone along the endorsal margin of the bone. The relationship between progn.and articular cartilage loss is more difficult to predparticularly in racing Quarter Horses where the first aut.(C. WM.) has had horses with complete loss of articlcartilage from the distal radial carpal bone that have ccback and won at Stakes level (see Fig. 4.37). Actual figubased on follow-up with these cases are presented in a ssequent section.

Fragmentation frequently will be found adjacent tomedial plica, which has also been described as the medial dolintercarpal ligament (MDIC) (Wright 1995). This origin~on the distal dorsal medial aspect of the radial carpal bcand has an oblique course to insert on the medial joint caps(Selway 1991). On arthroscopic examination, its degretconfluence with the joint capsule is quite varied andligament cannot always be identified. The MDIC ligammay function as part of the medial collateral ligament, recarpal bone displacement during weight bearing, or assislproduction of "closed-pact" position in preparationloading (Wright 1995). It has been theorized that the ligamcan act like a "leather hinge" on a box, becoming entrap]between the second and third carpal and radial carpal bolwhen the joint is extended. This can lead to "rocking" ofcarpal bones and, thus, osteochondral degeneration wit]the middle carpal joint (Selway 1991). Using this ratioruSelway (1991) recommended removal of the protruding MIligament to a level of confluence with the joint capsule. 1authors believe that current evidence does not supporlprimary etiological role for the MDIC ligament in fragm(tation and therefore do not practice or recommend prop}lactic desmotomy. There is no doubt that the origin of tligament is commonly involved in degeneration and fragmttation of the dorsodistal medial aspect of the radial car)bone, but all evidence suggests that this is not causatiRemoval of fragments attached to the DMIC ligament ~result in tearing and frayed tissue that can be debrided wbasket forceps or a motorized synovial resector (Fig. 4.39).

strong indicator of severe damage within the joint. In someinstances, radiographs provide an indication of marked boneloss in association with chip fractures (Fig. 4.35), but usuallythe bone loss is more than is anticipated (Fig. 4.36). In eithercase, when loss of bone is marked, there is loss of jointcongruity and, potentially, instability. In instances wherebone remains but there is Grade 3 articular cartilage loss,radiographs do not predict the amount of damage at all

Dorsodistal intermediate carpal boneChip fractures of the dorsodistal aspect of the intermedi,carpal bone occur most commonly on the medial facet. Lcommonly. fragments are located lateral to the medidivisional ridge on the distal articular surface where they cbe radiographically "silent". Osteophytosis may also be Sfat this site. The pre-surgical radiographs that most frequendemonstrate fragmentation are the flexed lateromedial (Land the dorsomedial-palmarolateral (DMPLO) projectic

(Fig. 4.40).The approach for operating on the distal intermedi.

carpal bone lesions is illustrated in Figure 4.41. Tarthroscope is placed through the medial portal and tinstrument enters through the lateral portal. Visualizatior

usually good (Fig. 4.42), but the instrument angle is noconvenient for these lesions as for those on the distal racarpal bone. Because the distance from the instrument poto the lesion is often small, opening forceps inside the jobsometimes difficult. This can be aided (if fragmentation atsite is predicted preoperatively) by making the lateral pocloser to the distal row of carpal bones. Lesions on the nmedial portion of the intermediate carpal bone can be ndifficult to visualize completely because differeIJmovement between radial and intermediate carpal b(when the carpus is flexed produces a "step" in the mil

carpal joint.Lesions of the distal intermediate carpal bone vary in :

but most are small and have relatively little associ;degeneration. In these cases, the prognosis is good. Extenloss of cartilage and bone can occur but this is farcommon than on the distal radial carpal bone and is usumore predictable on radiographs.

During operations involving an intermediate carpal tlesion, even if it is the only fragment demonstrated ragraphically, the surgeon should evaluate the distal r.

Fig. 4.38Arthroscopic views before (A) and after (8 and C)debridement of bone loss from distal radial carpal bone.There is bone loss along the entire width of the radial carpal

bone.

in other locations in the middle carpal jointfrequently in the center of the joint and are 10the extensor carpi radialis tendon. In additiolcapsule is closer to the articular margin than is tIthe radial and intermediate carpal bones. Becalfactors, joint distention may not be as effectiveclear visualization of the fragment. Also, the cbat this site may extend beyond the attachmentcapsule.

In a paper published on the incidence, lo(classification of 371 third carpal bone fractures inincomplete fractures of the radial facet occurred ilarge proximal chip fractures of the radial facet (140 cases, small proximal chip fractures of the]occurred in 18 cases, medial corner fractures 013 cases, frontal plane slab fractures of the rad39 cases, large frontal plane fractures involving 1and intermediate facets occurred in 35 cases, fractintermediate facet occurred in 13 cases, and s~fractures of the third carpal bone occurred i:(Schneider et alI988).

The most useful preoperative radiographs i

(DLPMO) projections (Fig. 4.44A). '

DDiO) is also useful in further(Fig. 4.44B). Thin slab fracturesarthroscopic removal. but mostwith screw fixation using,

subsequent sections). Figure

reversed position could be

third carpal bone than is themanipulation of

fractures may be typical chip-type

bone, because radiographically silent lesions on theaspect of the radial carpal bone have been en-

When these occur, surgery can be performed inusing the same lateral instrument portal as

Partial slab fracture that extenddistad and exit dorsad -.-,-

medial side of the intermediate carpal bone should be-during procedures involving distal radial carpal

.fragments(Fig. 4.43). In this case we use

medial instrument portal that is used for distal radial

to arthroscopic surgery. Thin slab jthickness of the third carpal bone can also be renusing the arthroscopic technique although cut1carpometacarpal joint capsule attachments withdifficult. however.

The prognosis for third carpal chip fractures an(slab fractures is variable. As in other sites in the middJjoint, the prognosis is excellent with small, wellfragments accompanied by minimal degenerativePostoperatively, new bone proliferation is a potential]when the fracture line extends deep into the cattachments. Multiple fragments off the thirdbone may occur. When these fragments are large antbone from the joint is significant. instability is a p

problem.

of arthroscope and instruments is often required to performthe removal.

Dorsoproximal third carpal bone

Fragments from the proximal third carpal bone cansometimes be more difficult to operate than chip fragments

Arthroscopic Surgery for Removal of Osteochondral Chip Fragment

Fig. 4.41Diagram of positioning of arthroscope and instrument during

operations involving a distal intermediate carpal bone chip

fragment.

R

Fig. 4.42

Arthroscopic views of fragments of distal intermediate carpal bone (radiographs of these fragments are in Fig. 4.40). (A-B) Smallfragment in left carpus (C-F) Large fragment in right carpus. continued

Fig. 4.43Fragment on distal intermediate carpal bone found duringdiagnostic arthroscopy for removal of a fragment on distal rad

carpal bone. The fragment is on the most-medial margin of thEdistal intermediate carpal bone and in this case was removed I

a medial instrument portal.

Dorsoproximal radial carpal bone The amount of cartilaginous damage associatthese chips is variable. and the prognosis varies aCC4Although marked erosion of the proximal surfacIradial carpal bone can occur there, it is a suimpression that the antebrachiocarpal joint appeamore forgiving than the middle carpal joint in horsimilar degrees of loss from the proximal versus 11articular surfaces of the radial carpal bone.

The technique for operating on fragmentation at this site isillustrated in Figure 4.49. These fractures are usually identifiedpreoperatively with standing and flexed lateromedial anddorsolateral-palmaromedial oblique DLPMO radiographs. Aswith other sites, the size of lesions can vary widely (Figs 4.50and 4.51). The arthroscope is placed through a lateral portaland the instrument enters through a medial portal. Thefragments can usually be well visualized and often arerelatively small (see Fig. 4.50), although significant loss ofbone occurs occasionally (see Fig 4.51).

With the standard medial portal, instruments mustapproach the lesion almost end-on, and manipulation can bemore difficult than on the distal aspect of the radial carpalbone. Repeated manipulation tends to cause subcutaneousextravasation and the medial aspect of the antebrachiocarpaljoint is also narrower than other locations. Occasionally, alateral arthroscopic portal can be used (Fig. 4.52).

Proximal intermediate carpal boneThe technique for operating on chip fractures at thillustrated in Figure 4.53. Standing and flexed later(LM) and/or dorsomedial-palmarolateral oblique (:radiographs (Fig. 4.54) are most useful in idefragmentation of the proximal intermediate carp;These fragments can be small, distinct and easily](Fig. 4.54), but. often. they are large and extend a c

QO Diagnostic and Surgical Arthroscopy of the Carpal joints

Fig. 4.48Arthroscopic views of a partial slab fragment of the third carpal bone. (A and B) Surface defect at proximal-distal length of thefragment respectively. (C) At removal of the fragment. (D) At debridement.

Fig. 4.49(A) Diagram of positioning of arthroscope and instrument during operations involving a chip fracture off the proximal aspect of\the radial carpal bone. (B) Making instrument portal.

§;7 Diagnostic and Surgical Arthroscopy of the Carpal Joints

Fig. 4.51Radiograph (A) and arthroscopic views (8 and C) of large displaced chronic fragment from the dorsoproximal margin of the radcarpal bone.

Fig. 4.52(A and B) Fragmentation of the proximal radial carpal bone encountered during removal of a proximal intermediate carpal bonfragment and being removed using a lateral instrument portal.

able distance into the joint capsule attachments (Fig. 4.55). Insuch cases. prior separation of capsular attachments inaddition to separation at the fracture line is recommended.Occasionally, a chronic chip or the spur associated with itmight have an intracapsular portion. In these cases, theintra-articular portion is removed with rongeurs or a burr asfar as the capsular reflection only. Postoperative radiographsoften do not appear as satisfactory as following fragmentremoval. Nonetheless, this is considered preferable to thecapsular trauma necessary to remove intracapsular fragmentsand/or new bone. As with fragments in other locations, arelatively small fragment may be associated with considerableloss of articular cartilage.

Proximal ulnar carpal bone

Fragments at this site are rare. To perform arthroscopicsurgery for this lesion, the arthroscope is placed medially andinstruments enter through the lateral portal.

in the carpal joints. Often the fragmentsradiodensity, loss of infrastructure,new bone formation. Occasionally, theradiographic views do not demonstrate aevent, a skyline (DPrDDiO) view of therecommended (Fig. 4.56B).

The technique for operating on chip fractures of the dorso-lateral margin of the distal radius is illustrated in Figure 4.57.The arthroscope is inserted through the medial portal andinstruments are passed through the lateral portal. Theposition of the fragments necessitates that instruments aredirected distad so that their shafts lie at an angle close to thedorsal aspect of the carpus. The fragments are usually large(;?; 1 cm wide), with the most proximal portion attached to thefibrous joint capsule. These fractures are also commonlycomminuted with a wedge-shaped osteochondral fragmentpalmar to the largest dorsal fragment.

The size of the fragment can be assessed reasonablyaccurately from preoperative radiographs. Damage is usuallylimited to the defect created by the fragments. only andcartilage loss does not usually extend peripheral to the defect(Figs 4.58 and 4.59). The arthroscopic appearance dependson the age of the fragments. In many such cases the dorsalfragment appears to be acute and the palmar wedge shapedfragment appears to be longer standing. In acute fragmen-tation there is usually hemorrhage within the fracture. When

Lateral aspect of the distal radiusThese fragments are usually best demonstrated on adorsomedial-palmarolateral (DMPW) radiographic projection(Fig. 4.56A). They can be displaced, non-displaced, single ormultiple, and frequently are larger than fragments elsewhere

8§ Diagnostic and Surgical Arthroscopy of the Carpal joints

Fig. 4.57Diagram (A) and external view (B) of arthroscope and instrument during operations involving a chip fracture off the distal lateral

radius.

Fig. 4.58Arthroscopic view of relatively small distal lateral radius fragment of a right carpus prior to removal (A), at elevation (8), atremoval with Ferris-Smith rongeurs (C), and after removal and debridement (D).

: fragments, the larger fragment is usuallysuperficial fragments, and a deep search is

in these cases. With fractures of long-standing,,

bony proliferation proximal to the defects within the fibroljoint capsule is common, and should be left alone. Debridlment follows the basic principles outlined previously, but mcinclude areas of capsular tearing. This should be perform(carefully and in a conservative manner in order to limit tl:potential for traumatizing the adjacent tendon sheath and 1avoid further capsulitis.

When these fractures are of long duration, the fractulline may be obscured and the fragment is usually recognizeby the presence of articular erosions and irregularities.

Despite their size, the prognosis for chip fractures of thdistal lateral radius is good. This is generally considered to bthe result of different biomechanical influences and becausthe remaining articular surface is usually not damaged to angreat degree compared to other sites of carpal fragmentatior

Medial aspect of the distal radius

Fragmentation at this site is best demonstrated in

dorsolateral-palmaromedial oblique (DLPMO) radiograpl(Fig. 4.61). The technique for removing fracture fragmentfrom the medial aspect of the distal radius is illustrated ilFigure 4.62. The arthroscope is placed through the latera

Before retrieval, large fragments are elevated (Fig. 4.59)attachments severed with a periosteal elevator.cup rongeurs are used to remove fragments.

usually necessary to twist the rongeurs after graspingfragment to ensure that the fragment is free of attach-

ments before making an attempt to pull it through the jointcapsule. Enlargement of the skin incision is commonlynecessary to bring these fragments out through the skin.Figure 4.60 depicts a chronic distal lateral radius fragmentthat was associated with osteochondral disease peripheral tothe fracture. Damage is rarely more extensive that that notedhere, unless the lesion is chronic and mobile. Removal oflarge fragments that extend proximally into the capsularreflection can result in penetration of the synovial sheathof the extensor carpi radialis or common digital extensortendon.

Mter removal of the fragment, the depths of the defect arecarefully explored to find any remaining fragments. Some

portal and the instruments through the medial portal. Awith distal lateral radius fragments, the instruments arangled rather flatly against the knee and directed proximacThese fragments are similar to their lateral counterparts ilthat the surface damage is usually localized to the area of thfragment. However. smaller fragments are more commolmedially but large ones can occur (Fig. 4.63). Methods (surgical removal are the same as those described for later~radius fragments. but sometimes on the most medial portio]of the bone. access with forceps is more difficult than laterall:The surface manifestation of these fragments varies like dist~lateral chips. and the use of the curette may be necessary fochronic lesions (Fig. 4.64). Removal of very large dist~medial radius fragments can potentially cause trauma to thextensor carpi radialis tendon shealth with consequeIJsynovial herniation (Fig. 4.65).

Diagnostic and Surgical Arthroscopy of the

Removal of osteophytes or spurs

it is

on first, as subcutaneous fluid extravasation is more likely tooccur in the antebrachiocarpal joint. The loss of irrigatingfluid after creation of a large instrument portal means thatthe surgeon will need to switch to the opposite side of thejoint to operate on a chip on the other side, and insert thearthroscope into a relatively non-distended joint. If time has

, between the two entries, some blood may be in the

which can be cleared by irrigation. The bleeding isfrom a previously debrided subchondral bone

and occurs after loss of joint distention. With jointand irrigation, subchondral bleeding is usually

The removal of spurs or osteophytes is appropriate ifhave fractured off or if their interposition into the joint]them likely candidates for later fracture. Figuredemonstrates spurs that were removed. These spurs nremoved with Ferris-Smith rongeurs. curettage, an ostecor burr.

Most spurs that are visible radiographically arcandidates for removal. In many instances the experisurgeon can predict whether an attempt at removing (is appropriate by examining the radiographs. As a gtrule. however, the surgeon should maintain an openand examine the spur at the time of arthroscopic suThis statement is not to say that every carpus with a Splcandidate for arthroscopic surgery. As experienced cliniknow, many small spurs noted in 2-year-old horses are Ievidence of previous synovitis and capsulitis. and arecurrent clinical importance.

Articular cartilage and bonedeBeneration in association with carpalchip fractures

The amount of articular surface loss should be documenteon surgical notes and may be recorded by way of a drawin(Fig. 4.68). Significant bone loss causes loss of cubodi~congruency (Fig. 4.67F and G).

More subtle degrees of cartilage damage have been defineand graded in man (Pritsch et al 1986) and the recent~defined ICRS grading system (Cartilage Injury EvaluatioJSystem 2002) is gaining acceptance. These classificationshould not be confused with the system just describedAlthough a more detailed breakdown of damage may b,appropriate for guiding treatment. it may have limited ValUIin defining prognosis.

Debridement of defects after chipfracture removal

A discussion of the rationale for debridement after fragmeniremoval necessitates a brief review of current knowledg(regarding healing of tissues. particularly articular cartilageThese considerations are also important with regard tcpostoperative management and convalescent time. Tradition.

The presence of articular cartilage degeneration associatedwith carpal chip fragments and the debridement of degeneratecartilage were mentioned previously, although this problemdeserves specific attention. For convenience, four grades ofarticular surface damage, as evaluated arthroscopic ally, havebeen made (Mcllwraith et al 1987) and are illustrated inFigure 4.67:

1. Minimal fibrillation or fragmentation at the edge of thedefect left by the fragment, extending no more than 5 mmfrom the fracture line (Fig. 4.67 A and B).

2. Articular cartilage degeneration extending more than5 mm back from the defect and including up to 30% of thearticular surface of that bone (Fig. 4.67C and D).

3. Loss of 50% or more of the articular cartilage from theaffected carpal bone (Fig. 4.67E).

4. Significant loss of subchondral bone (usually distal radialcarpal bone lesions) (Fig. 4.67F and G).

Erosion and Chips

Proximalcarpal row

Right

Distalcarpal row

.

rPartial thicknesskissing lession

and debridement.

--thickness

defects curetted experimentally were covered withgranulation tissue 1 month later. This tissue underwentmetaplastic

change to form fibrocartilage by 2 months andimperfect hyaline cartilage by 6 months. In another carpalstudy, Grant (1975) noted that the defects filled with a deeperlayer of immature hyaline cartilage and a more superficiallayer of fibrocartilage. Synovial adhesions were also present.The repair most closely resembled the adjacent normalhyaline cartilage when there were few synovial adhesions. Ifsynovial adhesions were significant. the defects filled with amore primitive fibrocartilage and fibrous tissue. The authorstherefore concluded that proximity of the lesion to thesynovial membrane was potentially an advantage to healing.

Hurtig et al (1988) created large (15 mm square) andsmall (5 mm square) full-thickness lesions in weightbearingand nonweightbearing areas of the antebrachiocarpal,middle carpal, and femoropatellar joints. Repair had occurredin most small defects at the end of 9 months by a combination

ally, repair of articular cartilage has been considered in twosituations: (1) superficial defects that do not penetrate the fullthickness of the articular cartilage, and (2) full-thicknessdefects, which extend to subchondral bone. Superficialdefects in equine articular cartilage do not heal, whereas full-thickness defects heal through formation of granulationtissue and its subsequent metaplasia (Riddle 1970).

In studies involving the horse, the nature of the replace-ment tissue in the full-thickness defect varied betweeninvestigators. In one study, the authors noted that whereas3 mm, full-thickness defects were repaired satisfactorily at 3months, defects of 9 mm in diameter were not completelyreplaced at 9 months (Convery et aI1972). The repair tissuewas a variable mixture of fibrous tissue, fibrocartilage, hyper-cellular cartilage, and (occasionally) bone, whereas anotherinvestigator reported complete healing of both 4 mm and 8mmdiameter, full-thickness defects (Grant 1975). In a classicstudy on the carpus, Riddle (1970) demonstrated that full-

or fragmented cartilage is removed. This protocol is baselthe belief that loose cartilage is irritating and may detachits prospects of healing onto bone are virtually nil. Parthickness erosion adjacent to a full-thickness defect issubjected to curettage if the cartilage that remarnattached solidly to the bone. Full-thickness defectsdebrided to the level of subchondral bone. Any soft defelbone is also removed.

In summary, based on both research evidence and ~we have observed, the authors feel that a conser Viapproach when it comes to debridement of fibrillatiolthinning of articular cartilage should be taken. In 0instances, when cartilage is separated and may appearthickness, the calcified cartilage layer may still be pre~Failure to remove the calcified cartilage layer will causehealing response. With experience, one can recognizedifference between the calcified cartilage and the:chondral bone (Frisbie et al 2001, unpublished data). ,debridement of subchondral bone, in an adult animal,relatively straightforward to recognize defective, gran(and often necrotic) bone and distinguish it from Slhealthy subchondral bone. The distinction is more difficuthe young animal, where the subchondral bone is quiteIn contrast, when the subchondral bone of a carpal defehard and sclerotic, the use of subchondral microfractureaid access to stem cells and growth factors in the cancelbone and has been used in clinical cases (Frisbie et al 2(unpublished data).

Deep or extensive debridement using motorized equipnis unnecessary in most cases. If debridement extends be}the level of attachment of the joint capsule, it can resuincreased capsulitis and bone proliferation. In relating Slof these ideas to follow-up management, if the actual matcthat fills fresh, localized chip fragments is not of mconcern and the area of the defect is small, then, if 0sources of irritation have been removed, atWetic funcshould be limited only by soft tissue healing. For this reahorses with acute fragmentation and with minimal evid(of long-standing adaptive failure can return to training i6-8 weeks.

When the lesions are more severe, the limitationcartilage healing are more significant. If the area ofcartierosion is larger, then some form of healing is required,the importance of intact subchondral bone supporteffective articular cartilage healing is relevant. Demination of the conditions that are necessary or optirhealing requires further investigation. At present, the aut!assume that extra time is required when subchondral heais necessary to restore a weightbearing surface. However,time requirements and physical factors for bone healinJGrade 4 lesions have yet to be determined. In chronic, concated cases, a minimum of 4-6 months rest is currerecommended.

With the possible exception of infected joints IChapter 14), therapeutic synovial resection with theof motorized equipment is not recommended. Localisynovectomy is only performed occasionally to facili'visualization.

of matrix flow and extrinsic repair mechanisms, althoughelaboration of matrix proteoglycans was not complete at thistime. Better healing occurred in small weightbearing lesionswhen compared to large or nonweightbearing lesions.Synovial and perichondrial pannus interfered with healingof osteochondral defects that were adjacent to the cranialrim of the third carpal bone. Large lesions had good repair at2.5 months postoperatively; however, by 5 months, cleftsbetween the reparative tissue and subchondral bone werecommon. Later, the clefts became undermined flaps of fibroustissue that were disrupted by normal biomechanical forces,resulting in exposed subchondral bone.

Grant (1975) also found no correlation between increasedhealing time and improved tissue quality in full-thicknessdefects; defects at 54 and 67 weeks contained more fibro-cartilage and less hyaline cartilage than defects at 42 and47 weeks. Work in other species also has revealed hyalinecartilage at early stages of healing. There is therefore indirectevidence that, at 4 months. defects in the articular cartilagehave reached the limit of healing capacity and. by 12 months.the replacement tissue has begun to degenerate.

More recent work in the first author's (C.W.M.) laboratorycomparing normal healing in full-thickness defects at 4 and12 months has demonstrated that the percentage of Type IIcollagen will progressively increase from 0% at 4 months to80% at 12 months. The hexosamine level is about half theamount in normal cartilage at 4 months. and slightly lessthan the 4 month level at 12 months (Vachon et al 1992,Howard et aI1994). The current state of articular cartilagehealing has been reviewed (Mcllwraith & Nixon 1996) and isnow the subject of a separate chapter in this textbook.

The authors have also had the opportunity to operate bn anumber of carpal joints for the second time after the animalshave raced and have observed that the healing of defectsvaries (Fig. 4.69). In repair areas subjected to histologicanalysis, fibrous tissue predominated. For all experimentalstudies in which cartilage healing in some form was demon-strated, these joints were never subjected to the continualexercise and trauma of a racehorse. Since the authorsquestion how much functional healing occurs, debridementof partial-thickness defects is not performed. Cartilage isaneural and how much trouble many partial-thickness defectscause is questionable. Commonly, these defects are kissinglesions in association with fragments, and the best treatmentis to remove the initiating cause, i.e. the fragment. Whethermore than fibrous tissue will fill the defects is unclear, and oneshould therefore be conservative in creating further defects orenlarging ones already present. The results of a study in maninvolving follow-up arthroscopy of patients treated forchondromalacia of the knee with or without cartilaginousshaving supports a conservative approach to management ofpartial-thickness defects. The conclusions were that onlyloosely hanging articular cartilage should be shaved, andthat softened, non-loose, fissured articular cartilage shouldbe spared (Friedman et aI1987).

The authors also adopt a relatively conservative approachwith regard to debridement of deeper defects that remainafter fragment removal. Rough edges or adjacent undermined

management

5 days to decrease pain. reduce synovitis. and facilitate.Results of a double-blind. randomized

less(;'synovitis. and less effusion postope~atively (6gilvie~Harris etr

al1985). They also had more rapid return of movement andquadriceps function, and their return to work and sport wassignificantly faster. The administration of antimicrobialdrugs is a matter of individual surgeon preference.

Based on current knowledge of cartilage healing. it issubjectively recommended that exercise be avoided for thefirst week after surgery to enable the blood clot to organizeand to allow granulation tissue to commence formation. Passiveflexion and hand walking begin after 7 days and the level ofexercise is then progressively increased in line with the severityof articular compromise. In horses with simple. fresh frag-ments (Grade 1 lesions), training may begin at 6 weeks. Asthe damage in the joint increases. the convalescent timeshould be appropriately increased. Horses with Grade 2cartilage loss should have a minimum of 3-months rest; withGrade 3 and 4 lesions the horses should have 4-6-monthsrest. Rehabilitation protocols including underwater treadmillor swimming may be recommended if available.

Postoperative use of hyaluronan (HA) and polysulfatedglycosaminoglycans (PSGAGs) is variably favored by differentclinicians. The authors do not consider HA a necessary orconsistent part of the postoperative routine. In most cases.the synovial HA levels are expected to return to normal in theconvalescent period. If the articular damage at the time ofsurgery is of relatively low grade. then most cases resolveafter a single treatment. PSGAG (Adequan@) is administeredwhen there is significant articular cartilage degeneration andexposure of subchondral bone. Although there may be littleeffect on defect healing. ongoing cartilage degeneration maybe inhibited (McIlwraith 1982. Yovich et al1987). Clinically.a good response to PSGAG treatment is seen in the caseswith severe articular cartilage damage. An initial intra-articular injection of Adequan@ (250 mg with 0.5 mlAmikacin sulfate) is recommended followed by weeklyintramuscular injections of 500 mg. Corticosteroid therapyafter arthroscopic surgery is only recommended when thereis severe. persistent synovitis. Overall, arthroscopic surgeryas a therapeutic procedure is best followed by rest and

physical therapy (controlled exercise).

Case selection, prognosis, and results

Although fragments of all ages and size are amenable toarthroscopic surgery, not all horses are good surgicalcandidates. Here, accurate communication with owners andtrainers is important to preserve the reputation of thetechnique before embarking on chronic cases with less

certain prognoses. The first author (C. W.M.) has had pleasiJresults with horses that have had multiple chip fragmentsas many as four carpal joints along with chronic chan~However, selection should be applied with regard to bohorses and clients. In general. a better result can be expectwith a horse that has proven racing ability and an owner thunderstands the prognosis.

Follow-up information on the first 1000 carpal joiroperated on by the first author (C. WM.) has provided objectiinformation to give clients regarding prognosis (McDwraith et1987). Arthroscopic surgery was effective in removing'osteochondral fragments as well as treating other lesiorThere were no cases of intra-articular infection and fewothcomplications. The overall functional ability and cosmelappearance of the limbs were excellent.

Post-surgical follow-up information was obtained for 44racehorses. After surgery, 303 (68.1 %) raced at a level equto or better than the pre-injury level, 49 (11.0%) hcdecreased performance or still had problems referable to tlcarpus. 23 (5.2%) were retired without returning to trainin28 (6.3%) sustained another chip fracture. 32 (7.2%) develop<other problems. and 10 (2.2%) sustained collapsing sIcfractures while racing. When horses were separated into fOlcategories of articular damage. the performance in the t\\most severely affected groups was significantly inferior. Orhundred thirty-three of 187 horses with Grade 1 dama~(71.1 %),108 of 144 with Grade 2 damage (75.0%), 41 of 7with Grade 3 damage (53.2%). and 20 of 37 horses wilGrade 4 damage (54.1 %) returned to racing at a level equ,to or better than the pre-injury level. The success rate in caslwith Grade 1 and Grade 2 lesions was significantly greatcthan that in cases with Grade 3 and Grade 4 lesions. The dalfrom racing Quarter Horses and racing Thoroughbreds we)divided. In 277 Quarter Horses, 81 of 112 (72.3%) witGrade 1 lesions, 72 of 96 (75.0%) with Grade 2 lesions. 26 c46 (56.5%) with Grade 3 lesions. and 13 of 23 (56.5%) witGrade 4 lesions returned to racing successfully. In 16Thoroughbreds. 51 of 73 (69.9%) with Grade-1 lesions. 3of 47 (76.6%) with Grade 2 lesions, 14 of 30 (46.7%) witGrade 3 lesions. and 7 of 14 (50%) with Grade 4 lesiorreturned to racing successfully. These data demonstrate a leIfavorable prognosis for horses with severe damage but alsthat many horses can still come back and race successfully.has been observed subjectively that. in more severe cases.shorter racing career can be anticipated due to recurrercarpal problems, including refragmentation.

In five Quarter Horses used for roping, barrel racing. (rodeo, all but one with a Grade 3 lesion returned to successflperformance. The pleasure and hunter horses had successflresults in all six cases (one Grade 1, two Grade 2, threGrade 3. and one Grade 4 lesions). The results of surgerwere also assessed in relation to the location of lesions. anIhorses with a single site (or the same site bilaterally) involvewere included (Table 4.2).

In racing Quarter Horses. the prognosis associated wit]involvement of the third carpal bone was significantly worsthan lesions in other sites. In Thoroughbreds, third Carpcand radial carpal bone lesions had the poorest prognoses. ]

I relative to the joint involved, 63.3% ofHorses and 66.2% of Thoroughbreds with middle

carpal joint involvement returned to racing. For theantebrachiocarpal joint. 82.7% of Quarter Horses and65.5% of Thoroughbreds returned to racing successfully. Ifboth middle carpal and antebrachiocarpal joints wereinvolved. 64.7% of Quarter Horses and 64.7% of Thorough-breds returned to racing.

Since the publication of these data 15 years ago. therhave been a number of changes in clinical practices that maJinfluence future results. These include:

1. Earlier intervention and therefore a higher percentage ojGrades 1 and 2 lesions being presented for surgery.

2. Attempts to enhance osteochondral healing (Chapter 16),including subchondral microfracture.

3. More aggressive postoperative protocols, includingmedication and physiotherapy.

Osteochondral fragments from the palmar aspects of thecarpal bones have been recognized and removed (Mcllwraith1990, Wilke et al 2001, Dabareiner et al 1993). In someinstances these fragments are not surgical candidates, andwhen they are traumatic avulsions associated with otherproblems. the prognosis is typically poor (Wilke et al 2001).Small discrete osteochondral fragmentation can involveany of the palmar surfaces of the carpal bones. with the

remainder of the carpus, and generally requiring removal(Fig. 4.71). The proximodorsal aspect of the accessory carpalbone can be examined using a palmarolateral approach tothe antebrachiocarpal joint. A voluminous proximal palmaro-lateral joint pouch can be palpated after distension of thejoint. The arthroscope portal is made in the proximal portionof this outpouching, leaving the region over the proximalperimeter available for instrument access (see Fig. 4.71). Thefracture fragment is then identified, the soft tissue attach-ments and synovial proliferation debrided, and the fragmentremoved using rongeurs. Fractures of the distal portion ofthe accessory carpal bone are less frequent, and access to thisoutpouching of the antebrachiocarpal joint is limited.

The palmarolateral aspect of the midcarpal joint can beentered for removal of fractures of the ulnar and fourthcarpal bone. The arthroscope portal can be made withoutdifficulty; however, synovial tissue removal will be required tocompletely identify the fracture fragment during removal.There are no case series available to provide a basis forprognosis; however, the authors' limited experience suggeststhese fractures are a source of lameness, which can besubstantially improved by removal.

Fractures of the palmar surface of the intermediate carpalbone can involve a small wedge-shaped articular portiondetached from the proximal perimeter of the intermediatecarpal bone or a larger palmar slab fracture of the palmarsurface, extending from the antebrachiocarpal joint to themidcarpal joint. Removal of smaller fragments through thecarpal tunnel has been reported; however. arthroscopicremoval has not been described. Palmaromedial andpalmarolateral approaches to the antebrachiocarpal jointreveal only the medial aspect of the intermediate carpal bone.The lateral portion of the intermediate carpal bone. wherethe fractures have been described. is obscured by theaccessory carpal bone attachments.

Arthroscopic Surgery forSubchondral Bone DiseaseThese lesions were initially described in the proximal aspect ofthe third carpal bone. A number of radiographic changesmay be evident on tangential "skyline" views of the thirdcarpal bone including sclerosis, lytic lesions. or linear defectsvariously interpreted as incomplete fractures or "pre-slab"lesions. Sclerosis of the radial facet is a well-recognizedchange and some authors suggest that it is a primary lesion,often preceding more serious change, such as cartilagedamage or gross fracture (DeHaan et al198 7). These authorsalso suggest that early recognition of sclerosis of the thirdcarpal bone may help to prevent the occurrence of moreserious changes (DeHaan, et aI1987). Sclerosis is consideredto arise with training and racing. However, whether thesclerosis leads to articular cartilage lesions or the same forcesthat can cause sclerosis also cause articular cartilage lesionsdirectly has yet to be ascertained. Arthroscopy of a smallnumber of joints that had sclerosis as the only radiographic

radial carpal bone being most frequently involved. The dorsalarticular surface of the accessory carpal bone. and thepalmar surfaces of the ulnar and fourth carpal bones areinvolved less frequently. Large partial slab fractures of thepalmarolateral surface of the intermediate carpal bone alsooccur, and are largely inaccessible for arthroscopic removalor reattachment (Dabareiner et al19 9 3).

Fractures of the palmaromedial perimeter of the radialcarpal bone (Fig. 4.70A) have been described in 10 horses(Wilke et al2001). These fractures are thought to result fromcompression injury, with the palmar perimeter of the radialcarpal bone impacting on the surface of the radius, duringfalls onto the flexed knee. Arthroscopic removal can be donethrough a palmaromedial approach to the antebrachiocarpaljoint (Fig. 4.70B-D), which gives ready access to the palmarperimeter of the radial carpal bone and caudal aspect of theradius. The dorsal regions of the antebrachiocarpal joint areusually examined first, and concurrent damage to thearticular surface of the radius and proximal row of carpalbones is debrided. The arthroscope portal is then made in thedistended palmaromedial outpouching of the antebrachio-carpal joint. Examination of the palmar surfaces of thecarpal bones commences medially, and the arthroscope canbe redirected and introduced further to view the medialperimeter of the intermediate carpal bone and accessorycarpal bone articulations. Most fractures are not radio-graphically confirmed for weeks to months after injury, andthe chip fragment can initially be obscured at surgery by softtissue proliferation (Wilke et aI2001). An instrument portalis developed adjacent to the arthroscope entity and motorizedequipment used to remove synovial proliferation. Thefracture of the palmar surface of the radial carpal bone canthen be removed. Results in 10 horses with palmar fracture ofthe radial carpal bone suggested that simple fractures of thepalmar perimeter should be removed as soon as they areidentified (Wilke et al 2001). Salvage for riding was pre-dominantly defined by the extent of osteoarthritis evident atthe time of surgery. Cases where the damage was confined toonly the area of the chip and where the fracture was removedsoon after injury tended to have less osteoarthritis and didbetter after arthroscopic surgery. Concurrent injury to themedial collateral ligament or avulsion of portions of the radiussubstantially diminished the prognosis.

Palmar fractures of the other carpal bones are lessfrequently encountered. These include fractures of the fourthand ulnar carpal bone, the accessory carpal bone, and theintermediate carpal bone. The accessory carpal bone can befractured during compression injury to the flexed knee(nutcracker effect). The most common accessory carpal bonefractures are longitudinal frontal plane fractures that dividethe accessory carpal bone into a dorsal and palmar portion.These fractures do not involve the articular cartilage of thedorsal facets of the accessory carpal bone and are notconsidered candidates for an arthroscopic repair. Most ofthese fractures spontaneously develop a functional fibrousunion. Smaller fractures of the proximal or distal articularsurfaces of the accessory carpal bone can occur, disruptingthe articulation of the accessory carpal bone with the

sign, revealed wide variability in the gross appearance of theoverlying cartilage (Richardson 1988) and this author agrees.

So-called third carpal bone disease presents as a persistentcarpal problem that does not respond to medication and ischaracterized by lytic change evident on skyline radiographsof the third carpal bone (Fig. 4. 72A). Frequently, some degreeof surrounding sclerosis accompanies the lytic changes. Mostlesions occur on the radial facet; they may be single ormultiple and range from linear to circular in outline onskyline radiographs (Richardson 1988). The proximal sub-chondral bone is particularly thick and dense so that damageand lysis in this area results in dramatic radiolucency in

tangential projections.Arthroscopically, these lesions manifest as an area of

defective subchondral bone, with the overlying cartilageabsent, a depression in the articular cartilage, an underminedcartilage flap, or fragmented cartilage (Fig. 4.72B and C). Insome cases there is overt fragmentation of the subchondralbone, which, since it is non-displaced and cannot be imagedin profile, is not recognized radiographically. Loose tissue isremoved and the lesion is debrided with a curette. Thedefective bone is often granular in nature. A rim of intacttissue on the dorsal margin of the third carpal bone usually

remains, although in some cases the defective tissue exteruout through this margin. Also. if the remaining rimnarrow. it is removed to the level of the defect.

It is now recognized that subchondral bone disease c~occur at other locations and may be the precursorexercise/work-induced osteochondral fragmentation. Clinicsigns associated with subchondral bone diseases are similto animals with osteochondral fragmentation. However. pIsurgical diagnosis (at locations other than the third carpbone) is difficult; the disease is rarely demonstrable radigraphically. The best example is the distal radial carpal bolJwhere lesions can consistently be found arthroscopicaJ

(Fig. 4.73).Subchondral bone disease has also been seen on the dist

radial, proximal third, proximal radial. intermediate carpbones. and on the distal radius (lateral and medial) (Fig. 4.7:Figure 4. 73H illustrates subchondral bone disease on the mopalmar areas of the second and radial carpal bone.

The post-surgical protocol is determined by the degreearticular compromise. using criteria similar to other carparthroscopic procedures. In one report of 13 Standardbr,cases involving the third carpal bone. 8 returned to racing,of these in their original class (Ross et al1989).

More recent work has investigated the relationshipbetween increased bone density in the third carpal bone andracing (Young et al1991). Regional variations in trabecularbone density and stiffness have been implicated in thepathogenesis of third carpal bone fractures (Young et al1991). In addition. subchondral lucency. commonly incombination with sclerosis of the third carpal bone radialfossa. has been associated with acute. moderate to severelameness referable to the middle carpal joint in Standardbredracehorses (Ross et al1989). Investigators in Sweden havelooked at subchondral sclerosis and subchondral lucency inthe third carpal bone in Standardbred horses diagnosed withtraumatic carpitis and related it to clinical appearance andprognosis for racing. Subchondral lucency was foundsignificantly to influence the degree of lameness and the timeto start. but did not significantly affect the chance of racing

within 30 months post-examination (Uhlhorn & C1999). However, it was also recognized that there wanumber of third carpal bones with severe sclerosis;course, no arthroscopic intervention, and this limitcan be concluded from this study.

Twenty-four cases of tearing of the medial palmarcarpal ligament (unpublished data) were reportedprevious edition of this text. Since then there ha

Arthroscopic Surgery forTreatment of CarpalSlab Fracturescystic lesions are commonly noted in the

clinically significant lesions will occur and areto intra-articular analgesia. A

the proximal radial carpal bone that was sympto-illustrated in Figure 4.77. The cystic lesion was

arthroscopically and the opening found, theand the joint flushed (Fig. 4.77).

Current status of surgery

Various forms of frontal and sagittal slab fractures occurthe carpal bones. of which the most common is a fronplane slab fracture of the third carpal bone. The advanta~offered by arthroscopy are such that repair of carpal slfractures under arthroscopic visualization is now t

technique of choice. Arthroscopic evaluation of the entirejoint and fracture reduction are superior to those obtained byradiography, fluoroscopy, or of direct observation, andsurgical trauma is minimized (Richardson 2002). Thesefeatures comply entirely with the AD goals of atraumaticoperative technique, accurate anatomic reduction, rigidinternal fixation, and early postoperative ambulation.Recognizing concomitant damage that will detract from asuccessful outcome also enhances clinical success. Caseselection is important and animals with poor conformation,evidence of asymmetric limb loading, or failure of osseousadaptation, and horses with poor athletic histories areunlikely to produce rewarding results.

Removal of slab fractures of the thirdcarpal bone

The authors' general philosophy is that whenever articularsurfaces can accurately and safely be reconstructed, thisshould be the primary treatment goal. Thin displaced andirreducible slab fractures of the third bone can be removedarthroscopically (Fig. 4.78). Standard dorsolateral arthroscopicand dorsomedial instrument portals are employed. Removalof the fragment necessitates sharp dissection from the dorsaljoint capsule and associated transverse dorsal intercarpalligaments. This is most effectively achieved with a fixed bladeknife and use of straight and curved elevators. A motorizedsynovial resector is useful during dissection in order tomaximize visibility. Once the fragment is loose, it is mani-pulated proximally in order that it may be grasped with largearthroscopic rongeurs. These then are twisted in order to freethe last remaining soft tissue attachments before thefragment is removed. Enlargement of the skin incision isfrequently necessary at this point. Debridement of the fracturebed follows and, in addition, limited debridement of the jointcapsule and dorsal intercarpal ligaments is appropriate.

Lag screw fixation of slab fracturesof the third carpal bone

and dorsolateral palmaromedial oblique radiograplprojections. Comminution occurs most commonly at tproximal margin of the fracture and may be seendorsolateral-palmaromedial oblique and flexed lateromedprojections. Detection of comminution is importantsurgical planning and prognostication. Flexed dorsoproximdorsodistal (skyline) projections define the dimensions a

The most common slab fracture of the third carpal boneoccurs in the frontal plane and involves the radial (medial)facet. Less commonly, there may be sagittal or parasagittalfractures in the medial one-third of the radial facet and insome animals there may be slab fractures of the radial facet inboth frontal and sagittal planes. Frontal plane slab fracturescan also run the full mediolateral width of the third carpalbone, including radial and intermediate facets. Occasionally,frontal plane slab fractures will involve the intermediate(lateral) facet only.

The degree of lameness varies from mild to severe.Fractures in a frontal plane are usually accompanied bymarked distention of the middle carpal joint and frequentlyalso by pain on palpation of the third carpal bone. Fracturesin the sagittal plane usually produce less severe clinical signs.Frontal plane fractures are usually apparent on lateromedial

the fracture (Fig. 4.79). Comminution or the

osseous infrastructure in the fracture

but may also be identified in dorsomedial-"

,-

some non-displaced fractures may heal with

articular insult; consequently, the risks of

fractures has also been shown to enhancehealing (Mitchell & Shephard 1980). Internal

of unstable or displaced slab fractures is usuallyto control pain and rapid development of prog-

.some cases, thin frontal plane stab fractures

third carpal slab

recognized advantages ofsurgery, there was no disruption of the

but all are based on that originally developed

planning is important and the surgeon

oblique radiographic projections (see Fig. 4.79).: can be repaired with AD/ ASIF cortex screws of

3.5 mm or 4.5 mm diameter. This is determined

I recumbency. The former offers greater versatility ofpositioning and also permits bilateral surgical

movement between the standard position for

The middle carpal joint initially is evaluated utilizing the1 arthroscopic portal. In acute injuries there is

permit visibility. This is usually performed through a-'" : portal. The dorsal compartment of

and any additional lesion noted. Non-displaced fractureshave variable amounts of cartilage disruption (Fig. 4.8IC).Some fractures. which on radiographic examination appearnon-displaced. are found to be unstable at arthroscopicevaluation. Displaced fractures frequently are accompaniedby additional cartilage loss and there may also be commin-ution, which most commonly occurs as a wedge in theproximal palmar margin of the fracture. Reduction (whennecessary) is effected most effectively by flexion and thisshould be performed progressively. Defects are debrided prior

to repair (Fig. 4.80) and any comminuted fragments tlpreclude complete reduction should be removed. Surgicopinion is divided on the fate of large palmar fragments.these can be retained and stabilized in the repair, SOl.surgeons prefer this option to removal and consequecreation of a large proximal articular deficit.

The medial and lateral margins of the fracture are mark,by percutaneous insertion of 22- or 23- gauge needl(Fig. 4.81). A spinal needle is then placed midway betwe4these two needles. close and parallel to the proximal articulsurface. and directed across the midpoint of the fractureclose to 900 as possible (Fig. 4.81). This needle is the mcimportant directional guide for implant placement. Contiuration of most slab fractures of the radial facet of the thicarpal bone is such that the tip of this needle usually lodgin the palmar fossa of the bone. It is important that medand lateral marker needles are used to determine the positilof this needle; the eccentric position of the arthroscope aJits inclined lens angle mean that accurate determinationthe midpoint of the fracture from the arthroscopic imaalone is not possible. Once the spinal needle has been placfa further 20- or 23- gauge needle is inserted into t]carpometacarpal joint directly distal to its point of entry.required, a radiograph is made to ascertain proximal-dislpositioning of the screw (Fig. 4.82).

At this stage some surgeons remove the arthroscope bthe authors' preference is for this to be held by a surgicassistant. A short (stab) incision is made midway between t]spinal needle and the marker needle in the carpometacarp

a No. 10 or 11 scalpel blade. This incision shouldwhich at

A glideis drilled in the fragment using the spinal needle as a

guide (Fig. 4.83). Once this has reached theinsert sleeve is positioned in the glide hole.

some displaced fractures in which a small amount ofarticular incongruity persists. limited fragment manipulationcan be performed at this time. Leaving the arthroscope in situpermits direct visualization of the process and continuousmonitoring of reduction and repair. The thread hole is thendrilled to the palmar surface of the bone (Fig. 4.84). Thisdepth is checked against the preoperative measurements.before a countersink is used to create an appropriately sizedbed for the screw head. The strongly convex dorsal face of thethird carpal bone means that this is important for all screwsizes to avoid point contact and maximize efficiency of com-pression and to avoid protrusion of the screw head into thejoint capsule. dorsal intercarpal ligaments. and tendon ofinsertion of the extensor carpi radialis. The reduction can be

assessed arthroscopic ally and radiographs should also Itaken at this point to ensure optimal implant placeme(Figs. 4.85 and 4.86).

Unstable comminuted fragments and detached cartilaare removed at this time and the joint is lavaged. Skin portconly are closed in a routine manner and a padded dressiIapplied for the immediate postoperative period. Follow-\radiographs of a repaired frontal slab fracture are present!in Figure 4.87. Displaced fractures of the radial facet of tIthird carpal bone are managed in the same fashion wiregard to fixation. However, one is frequently left wi'significant defects at the articular surface. There is usuallydefective subchondral bone wedge or multiple pieces and aftremoval a large size defect remains (Fig. 4.88). In othsituations, there can be a number of comminuted fragmenthat require removal, leaving a major defect on the lateraspect of the fracture (Fig. 4.88D and E).

Frontal fractures also occur, involving both the radial arintermediate facets, and are generally repaired with tvscrews (Fig. 4.89). Individual fractures of the intermediafacet of the third carpal bone also occur and are wcidentified on dorsomedial-palmarolateral radiographs; thlare usually repaired with a single 3.5 mm screw (Fig. 4.90

Sagittal and parasagittal fractures of the radial facet of tIthird carpal bone are inherently more stable than fracturesa frontal plane. They are best identified on skyline radioraphs and sometimes are also seen on dorsopalmiprojections (Fig. 4.91). Arthroscopic evaluation usually reveca fracture line commencing in the dorsal margin of the bOIat the junction of its middle and medial one-thirds. TIfracture may then curve to exit the articulation between 11second and third carpal bones or may extend in a straight IiItoward the palmar fossa of the third carpal bone (Fig. 4.9]Conservative management has been discussed for sagittfractures in the third carpal bone (Fischer and Stover 1987Half of the cases managed conservatively healed. Commnution is rare and cartilage loss uncommon. The principlesrepair are similar to those described above for fractures infrontal plane. However, there is a small window for safe areffective internal fixation, which necessitates implalplacement close to the dorsal margin of the articulaticbetween the second and third carpal bones (Fig. 4.9]Fortunately, fragment size is such that large implants are nlrequired and the head of a 3.5 mm AO/ASIF cortex screcan be safely placed at this site (Fig. 4.92).

Fractures which occur in both frontal and sagittal planlcan involve a number of configurations, and these will detemine the sites for appropriate implant placement. Nontheless, the principles applied individually to fractures ifrontal and sagittal planes apply. In some instances it may Inecessary, in order to avoid impingement of implants, 1place these at differing proximodistallevels within the bonFrontal plane fractures that involve the radial and intemediate facets of the third carpal bone can occur in a numb!of configurations. The basic arthroscopic approach is cdescribed for frontal plane slab fractures involving the radi,facet only. However, it will usually be necessary to insert t\\screws in order to produce effective compression and stab

Diagnostic and Surgical Arthroscopy of the Carpal Joints

Fig. 4.83Diagram (A) and external views (B and C) of drilling 4.5 mm diameter hole in a frontal plane slab fracture of the third carpal bonE

Arthroscopic for Treatment of Carpal

,

R

,

of frontal plane slab fracture of the third carpal

fixation. These may involve pairs of 4.5 mm or 3.5 mm or acombination of screw sizes (Fig. 4.89). Slab fracturesinvolving only the intermediate facet of the third carpal boneshould be approached using dorsomedial arthroscopy anddorsolateral instrument portals. These usually are repairedwith a single 3.5 mm screw (Fig. 4.90).

also be beneficial at this point. The total convalescent pertis usually approximately 6 months.

With appropriate screw placement, complications auncommon. A further fracture extending to the screw and/the

creation of a chip fracture at this site has been recogniz(Unless there is good clinical or radiological evidenceimplicate

implants in lameness localizing to the middle carrjoint, screws are not removed.

Postoperative management

Results

In the series of 23 horses with third carpal slab fractulreported by Richardson (1986),17 had a 6-month or lon~follow-up interval. Ten of the 17 horses returned successfuto

racing; 1 horse was training soundly, and trained well bwas retired because of other injuries. One horse was unalto

return to training because of injury that had occurrsimultaneously with the slab fracture, 2 did not recover wenough to train, and 1 was lost to follow-up. At the timewriting, 6 horses had less than a 6-month follow-up periodwere

progressing well and 1 developed radiographic signsosteoarthritis. In uncomplicated cases, the cosmetic appec

Routinely padded dressings are used in the immediatepostoperative period but in horses with large unstablefractures use of a sleeve cast in recovery from generalanesthesia and in the immediate postoperative periodis appropriate. Most animals are confined to a stall for2-4 weeks and this is followed by a 6-8 week period ofincreasing amounts of walking exercise. Flexion exercise isencouraged immediately after surgery and should continueuntil a full and unrestricted range of flexion consistently isobtained. At the end of the walking period. progressiveincrease in exercise is permitted and this may involvecontinued controlled exercise. such as ridden trottingexercise or free exercise in a small paddock. Swimming may

111_lli~

Diagnostic and Surgical Arthroscopy of the Carpal Joints

Fig. 4.85Diagram (A), external view of screw placement (B) and radiograph confirming appropriate screw placement (C) in repair of frontaplane slab fracture of the third carpal bone.

Fig. 4.91Radiographs (A and B) and arthroscopic view (C) of sagittalfracture of the third carpal bone. A needle has been insertedto ascertain position of implant placement.

ance of each carpus was reported as good. with only a smallswelling over the screw (Richardson 1986). Horses withdisplaced slab fractures have a poorer prognosis for return toracing than do those animals with undisplaced slab fractures.because the latter are associated with more severe damage tothe joint surfaces (Bramlage 1983). This situation remainsthe same whether treatment involves arthroscopy orarthrotomy. Similarly. the prognosis worsens when loss of thewedge of cartilage and bone at the proximal articular surfaceleaves a large defect after fixation (Bramlage 1983).

There have been two other retrospective studies publishedon third carpal slab fractures and their repair. However, thesedid not generally involve arthroscopic surgery and careshould be taken in extrapolating results. In one paper, thecase records and radiographs of 155 horses with third carpalbone slab fractures were reviewed (72 Thoroughbreds and 61Standardbreds) (Stephens et al 1988). Of 73 fractures inStandardbreds, 37 were repaired by screw fixation. 18 were

surgically removed. and 18 were treated conservatively.the 82 Thoroughbreds with a third carpal fractures. 46 wrepaired with screws. 21 had the fragment removed. andreceived rest only. The effect of treatment on outcome was ]significantly different. Fracture characteristics did]significantly affect outcome. but did influence treatm,selection. In Standardbreds. 77% if the horses raced aJinjury: in Thoroughbreds. 65% raced. Earnings per stdeclined in each breed. but the decline was more pronounin Thoroughbreds (Stephens et alI988).

In a second study of 31 cases of racing Thoroughbrwith third carpal slab fractures. all cases were treasurgically. Twenty-one (67.6%) horses raced at Ieonce after recovery from the surgery: In 11 claiming hor:the claiming value decreased from a mean of $13.900 tmean of $6.500, the mean finish position was 5.8 :t 3before injury and 5.6 :t 3.30 after surgery (Martin e1

1988).

Treatment of Other CarpalSlab FracturesSlab fractures of other carpal bones are uncommon but alsocan be assessed. reduced, and repaired under arthroscopicguidance. Frontal plane slab fractures of the radial carpalbone are assessed arthroscopically through dorsolateralportals in both middle carpal and antebrachiocarpal joints.Fracture margins are marked with percutaneous needles andthe trajectory of implants is determined with a spinal needlein a manner similar to that employed in correspondingfractures of the third carpal bone. The fracture configurationwill determine the size and number of implants necessary.Figure 4.93 illustrates a slab fracture of the radial carpalbone which was repaired arthroscopically. Sagittal slabfractures of the intermediate radial of third carpal bone havebeen found at arthroscopy; the fractures have been generallytreated by removing the slab fragment. but in a recent casewith internal fixation with a 2.7 -mm screw. Arthroscopy alsois the technique of choice for the repair of reconstructablefractures of multiple carpal bones. These involve mostcommonly the radial and third carpal bones and thetechnique is varied to accommodate the variations of eachindividual fracture (Fig. 4.94). Such cases should be fittedwith a sleeve cast for recovery from general anaesthesia andfor the immediate post-operative period. Slab fractures of thefourth and intermediate carpal bones have been reported(Auer et al 1986). Poor results were achieved after screwfixation with arthrotomy.

Arthroscopic repair of large chip fractures can, in SOlinstances be an alternative to removal. This is based on tlpremise that reconstruction of articular surfaces is preferalto creation of a large osseous defect (Grade 4 lesion). TInecessary caveats are that fragments should be of sufficiesize and have adequate osseous infrastructure for placemeof a screw and that the process of reconstruction shouldless traumatic than removal. Most chip fractures are repairwith 2.7 mm AO/ASIF cortex screws although on occasiothese may be sufficiently large for use of 3.5 mm diame1screws. The latter may be employed in repair of frontal pIafractures of the third carpal bone that extend from its proxinarticular surface (usually the radial facet), to exit with tdorsal surface of the bone proximal to the carpometacarljoint.

Chip fractures of the dorsodistal margin of the radcarpal bone (Fig. 4.95), dorsoproximal margin of the tillcarpal bone and dorsoproximal margin of the radial carlbone have been repaired using 2.7 mm diameter screvDelineation of the fracture is performed in a manner simi]to that described for the repair of slab fractures. Most fragmeIwhich are amenable to repair will exit the bone within t.capsular reflection and/or associated intercarpalligamenThis point can be determined, if necessary by radiographicaguided needle placement. The position for screw placemelin most instances is within the synovial cavity and therefcthe drilling process and insertion of implants canperformed under direct arthroscopic visualisation. Healingrepaired carpal chip fractures has been documented but,date there have been no published results.

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Mcllwraith CW Experiences in diagnostic and surgical arthroscopyin the horse. EquineVetJ1984; 16: 11-19.

Mcllwraith CWo Diagnostic and surgical arthroscopy in the horse.2nd edn. Philadelphia: Lea & Febiger; 1990: 33-84.

Mcllwraith CWo Radiographically silent injuries in joints: An over-view and discussion. In Proceedings of 37th Annual ConventionAmerican Association of Equine Practitioners. San Francisco. CA1991. pp. 785-792.

Mcllwraith CWo Tearing of the medial palmar intercarpal ligamentin the equine midcarpal joint. Equine VetJ 1992; 24: 367-371.

Mcllwraith, CWo Arthroscopic surgery for osteochondral chipfragments and other lesions not requiring internal fixation in thecarpal and fetlock joints in the equine athlete: What have welearned in 20 years? Clin Techn Equine Pract 2002; 1: 200-210.

Mcllwraith CWo Bramlage LR. Surgical treatment of joint disease. In:Mcllwraith CW, Trotter GW (eds). joint disease of the horse WESaunders; Philadelphia 1996: 292-317.

Mcllwraith CW, Fessler ]F. Arthroscopy in the diagnosis of equinejointdisease.JAm Vet Med Assoc 1978; 172: 263-268.

Mcllwraith CWo Nixon AJ. Joint resurfacing: attempts at repairingarticular cartilage defects. In: Mcllwraith, CW, Trotter GW, (eds),Joint disease in the horse. Philadelphia: WB Saunders; 1996:317-334.

Mcllwraith CW, Yovich ]v; Martin GS. Arthroscopic surgery for thetreatment of osteochondral chip fractures in the equine carpus. ]Am VetMed Assoc 1987; 191: 531-540.

Martin GS. Haynes PF, McClure JR. Effect of third carpal slab fractureand repair on racing performance in thoroughbred horses: 31cases (1977-1984). J Am Vet Med Assoc 1988; 193: 107-110.

Martin GS. Mcllwraith CW Arthroscopic anatomy of the intercarpaland radiocarpal joints of the horse. Equine Vet 1985; J17:373-376.

Mitchell N. Shepard N. Healing of articular cartilage in intra-articular fractures in rabbits. J Bone Joint Surg [Am] 1980; 62:628-634.

Ogilvie-Harris DJ. Bauer M.. Corey P. Prostaglandin inhibition and thErate of recovery after arthroscopic meniscectomy. A randomizeddouble blind prospective study. J Bone Joint Surg (Br) 1985; 67:567-571.

Phillips TJ. Wright IM. Observations on the anatomy and pathologyof the palmar intercarpal ligaments in the middle carpal joints 01Thoroughbred racehorses. Equine Vet J 1994; 26: 486-491.

Pool RR. Meagher DM. Pathologic findings and pathogenesis of race.track injuries. Vet. Clin North Am Equine Pract 1990; 6: 1-30.

Pritsch M. Horoshovski H. Rarine I. Arthroscopic treatment 01osteochondral lesions of the talus. J. Bone Joint Surg [Am] 198668: 862-865.

Richardson DW. Technique for arthroscopic repair of third carpabone slab fractures in the horse. Am Vet Med Assoc 1986; 188288-291.

Richardson DW Proximal surface lesions of the third carpal boneProceedings of the 1st Advanced Arthroscopy Course. ColoradcState University. 1988.

Richardson DW. Arthroscopically assisted repair of articulalfractures. Clin Techn Equine Pract 2002; 1: 211-217.

Riddle WE. Healing of articular cartilage in the horse. J Am Vet MecAssoc 1970; 157: 1471-1479.

Ross MW. Richardson DW. Beroza GA. Subchondral lucency of thtthird carpal bone in Standardbreds racehorses: 13 case!(1982-1988),J Am Vet Med Assoc 1989; 195: 789-794.

Schneider RK. Bramlage LR. Gabel AA. Barone LM. Kantrowitz BMIncidence. location and classification of 371 third carpal bontfractures in 313 horses. Equine Vet J Supp11988; 6: 33-42.

Auer JA. Watkins JP. White NA. et al. Slab fractures of the fourth andintermediate carpal bones in 5 horses. J Am Vet Med Assoc 1986;188: 595-601.

Bramlage LR. Surgical diseases of the carpus. Vet Clin North Am(Large Anim Pract) 1983; 5: 261-274.

Convery FR. Akeson WHo Keown GH. The repair of largeosteochondral defects -an experimental study in horses. ClinOrthop 1972; 82: 253-262.

Dabareiner RM. Sullins KE. Bradley W. Removal of a fracturefragment from the palmar aspect of the intermediate carpal bonein a horse. J Am Vet Med Assoc 1993; 203: 553-555.

DeHaan CEo O'Brien TR. Koblik PD. A radiographic investigation ofthird carpal bone injury in 40 racing Thoroughbreds. Vet Radiol1987; 28: 88-92.

Finerman GAM. Noyce FR (eds): Biology and biomechanics of thetraumatized synovial joint: The knee as a model. Rosemount 11:American Academy of Orthopedic Surgeons. 1992.

Firth EC. Deane. Gibson K. et al. Current studies in carpal disease andfunction in the horse. Vet Cond Educ. Massey University. NewZealand 1999; 135: 81-89.

Fischer AT. Stover SM. Sagittal fractures in the third carpal bone inhorses: 12 cases (1977-1985). J Am Vet Med Assoc 1987; 191:106-108.

Friedman MI. Gallick GS. Brna JA. et al. Chondromalacia of the knee:a comparison between those treated with and without intra-articular shaving. Arthroscopy 1987; 3: 131.

Frisbie DD. Trotter GW. Powers BE. et al. Arthroscopic subchondralplate microfracture technique augments healing of largechondral defects in the radial carpal bone and medial femoralcondyle of horses. Vet Surg 1999; 28: 242-255.

Grant BD. Repair mechanisms of osteochondral defects in equidae: acomparative study of untreated and X-irradiated defects.Proceedings of the 21st Annual Meeting of the America~Association of Equine Practitioners. 1975. pp. 95-114.

Howard RD. McIlwraith CWo Powers BE. et al. Long-term fate andeffects of atWetic exercise on sternal cartilage autografts used forrepair of large osteochondral defects in horses. Am J Vet Res1994; 55: 1158-1167.

Hurtig ME. Fretz PB. Arthroscopic landmarks of the equine carpus.JAmVetMedAssoc 1986; 189: 1314-1321.

Hurtig ME. Fretz PB. Doige CE. Schnurr DL. Effects of lesion size andlocation on equine articular cartilage repair. Can J Vet Res 1988;52: 137-146.

Johnson 11. Arthroscopic surgery principles and practice. St Louis:Mosby; 1986.

Kannegieter NJ. Burbidge HM. Correlation between radiographicand arthroscopic findings in the equine carpus. Aust Vet J 1990;67: 132-133.

Kannegieter NJ. Colgan SA. The incidence and severity of intercarpalligament damage in the equine carpus. Aust Vet J 1993; 70:89-91.

Kawcak CEo McIlwraith CWo Norrdin RW. Park RD. Steyn PS. Clinicaleffects of exercise on subchondral bone of carpal andmetacarpophalangeal joints in horses. Am J Vet Res 2000; 61:1252-1258.

Kawcak CE. McIlwraith CWo Norrdin RW. Park RD. James SP. The roleof subchondral bone in joint disease: a review. Equine VetJ 2001;33: 120-126.

Lysholm J. Hamberg P. Gillquist J. The correlation betweenosteoarthrosis as seen on radiographs and on arthroscopy.Arthroscopy 1987; 3: 161-165.

Mcilwraith CWo Current concepts in equine degenerative jointdisease. J Am Vet Med Assoc 1982; 180: 239-250.

SJ: Arthroscopic surgery: the carpal and fetlock joints.-of the 29th Annual Meeting of the American

Association of Equine Practitioners. 1983.SJ: Intercarpal ligament impingement: a primary cause ofpathology in the intercarpal joint. In Proceedings of the

dorsomedial intercarpal ligaments in the midcarpal joint.Surg 1997; 26: 359-366.

Whitton RC. Rose RI. The intercarpal ligaments of the equmidcarpal joint. Part II: The role of the palmar intercarligaments in the restraint of dorsal displacement of the proxilrow of carpal bones. Vet Surg 1997; 26: 367-373.

Wilke M. Nixon AI. Malark I. Myhre. G. Fractures of the pairaspect of the carpal bones in horses: 10 cases (1984-2000Am Vet Med Assoc 2001; 219: 801-804.

Wright IM. Ligaments associated with joints. Vet Clin N Am 1911: 249-291.

Young DR. Richardson DW. Markel MD. Numamaker [Mechanical and morphometric analysis of the third carpal bcof Thoroughbreds. AmI Vet Res 1991; 52: 402-409.

Yovich IV. Trotter GW. McIlwraith CWo Norrdin RW. Effectspolysulfated glycosaminoglycans on chemical and physidefects in equine articular cartilage. Am I Vet Res 1987; .1414.

carpal bone in Standardbreds and Thoroughbreds: 155 cases(1977-1084). I Am Vet Med Assoc 1988; 193: 353-358.

H, Carlsten I. Retrospective study of subchondral sclerosisand lucency in the third carpal bone in Standardbred trotters.Equine Vet I 1999; 31: 500-505.

AM, McIlwraith CW, Powers BE, et al: Morphologic andbiochemical study of sternal cartilage autografts for resurfacinginduced osteochondral defects in horses. AmI Vet Res 1992; 53:1038-1047.

, , McCarthy PH, Rose RI. The intercarpal ligaments of the

equine midcarpal joint, Part I: The anatomy of the palmar and

Arthroscopic examination of the fetlock joint may beindicated specifically as a diagnostic procedure or as part ofan arthroscopic surgical procedure (McIlwraith 198'4).The latter situation is more common, although diagnosticarthroscopy is indicated in cases involving a lamenessproblem that has been localized to the fetlock but for whichthe radiographic signs are equivocal. The procedure is mostvaluable if synovial effusion is present or if the area oflameness has been identified as intra-articular on the basis ofa response to intra-articular analgesia and when there hasnot been a response to conservative treatment.

A complete arthroscopic examination of the metacarpo-phalangeal or metatarsophalangeal joint is not possible. Twoarthroscopic approaches are required to achieve as effectivean examination as possible of both the dorsal and palmar

(plantar) components.Each diagnostic examination will be described. Because

the dorsal approach most commonly is performed on themetacarpophalangeal joint, it is described for that joint. Theonly difference in examination of the metatarsophalangealjoint is that it may be more difficult because of the decreasedability to maintain extension of the joint. The plantar (palmar)examination is facilitated by flexion and this is especiallyconvenient in the hilid limb.

Arthroscopic examination of the dorsalmetacarpophalangeal joint

This arthroscopic examination ~an be performed with thehorse in dorsal or lateral recumbency. If lateral recumbencyis used. the horse should be positioned so that the site forarthroscopic entry is up. For the same reason of versatilitymentioned in Chapter 4 with regard to the carpal joint. theuse of dorsal recumbency is preferred. While the leg is beingsurgically prepared and draped. it is held by an assistant or issuspended in a mechanical device (Fig. 5.1). Draping can be

Arthroscopy has proven to be a most valuable technique inthe metacarpophalangeal and metatarsophalangeal (fetlock)joints. Its original use was principally, in arthroscopic surgeryin the dorsal aspect of the joint but then extended into thepalmar/plantar aspect. Arthroscopic surgery in the dorsalaspect of the fetlock joint is probably the best equine exampleof what can be achieved with joint distention.

The same advantages that have been discussed in thecarpus hold for arthroscopic surgery in the fetlock. Theindications for arthroscopic surgery in the metacarpo-phalangeal and metatarsophalangeal joints include thefollowing conditions:

1. Osteochondral fragments of the proximal dorsal aspect ofthe proximal (first) phalanx.

2. Erosions of articular cartilage and subchondral bonedisease on the dorsal proximal aspect of the firstphalanx.

3. Synovial pad fibrotic proliferation (villonodular synovitis)of the metacarpophalangeal joint.

4. Other forms of proliferative synovitis.5. Osteochondritis dissecans of the sagittal ridge of the

third metacarpal or metatarsal bones (McIIl/MtIIl).6. Osteochondral fragments associated with the proximal

palmar or proximal plantar aspect of the proximal

phalanx.7. Removal of apical fragments of the proximal sesamoid

bone.8. Removal of abaxial fragments of the proximal sesamoid

bones.9. Removal of basilar fragments of the proximal sesamoid

bones.10. Lesions of the intersesamoidean ligament.11. Axial osteitis of the proximal sesamoid bones.12. Avulsions of the suspensory ligament insertions.13. Subchondral cystic lesions of McIIl.14. Lesions of the dorsal plicae.15. Chondral fractures.16. Fibrous joint capsule tears.17. Assistance in repair of condylar fractures of the

McIIl/MtIIl and fractures of the proximal phalanx.18. Other selected proximal sesamoid fractures.

completed with the fetlock resting back on the elbow orappropriately suspended so the joint remains extended.

common digital extensor tendon. The outpouching of thedistended joint is more prominent lateral to the commondigital extensor than it is medial to it, despite the insertion ofthe lateral digital extensor tendon, which ramifies over thejoint capsule lateral to the common digital extensor tendon;this is penetrated when the lateral portal is created.

The site for the laterally placed arthroscopic portal is in theproximolateral quadrant created by distending the jointmaximally (Fig. 5.2). A No. 11 blade is used to incise the skinand stab through the joint capsule (see Fig. 5.3). The arthro-scopic sleeve containing a conical obturator is then insertedthrough the joint capsule, initially perpendicular to the skinand then parallel to the articular surface of Mclll to avoidiatrogenic damage to this area (Fig 5.4). Entry is completedby advancing the sheath proximad to avoid iatrogenicdamage to the midsagittal ridge of the distal metacarpus (seeFig. 5.4). The sheath can then be directed distad once over the

sagittal ridge.

Insertion of the arthroscope

The metacarpophalangeal joint is distended with fluid(Fig. 5.2) before making the arthroscopic portal. In this joint,distention facilitates the recognition of the correct place forthe arthroscopic portal and minimizes the risk of iatrogenictrauma to the joint on entry of the arthroscopic sleeve. Thereare no tendon sheaths to avoid as in the carpus, and thesurgeon does not have to be concerned with exact local-ization of structures before distention.

Distention is performed by using approximately 35 ml offluid and inserting a needle across the dorsal aspect of theproximal sesamoid bone into the palmar pouch of the fetlock(see Fig. 5.2). Adequate distention can be recognized easilywith bulging of the joint capsule on either side of the

1984), in that by taking the portal more proximad, it waspossible to better visualize the proximal lateral aspect of the

proximal phalanx.When the arthroscopic sleeve is inserted so that its tip

touches the medial capsule, the arthroscope is inserted andthe examination can begin. It is easy to enter the sub-cutaneous tissue plane when inserting the arthroscopicsleeve in the dorsal aspect of the fetlock, and care iswarranted during both the joint distention step as well aswith insertion of the arthroscopic sleeve to avoid thisproblem. The authors prefer to use this proximal arthroscopicportal in the metacarpophalangeal joint to avoid iatrogenicdamage to the midsagittal ridge of the metacarpus and toprovide the best overall view of the dorsal aspect of this joint.A more distal portal along the dorsal margin of the metacar-pophalangeal joint immediately proximal to the proximalphalanx, however, can provide convenient visualization of theproximal border of the first phalanx.

As in the carpus, creation of an instrument portal andinsertion of an egress cannula or probe are the next steps. Auseful measure is to insert a needle at the proposed instru-ment portal location to check if such a site is appropriate(Figs 5.5 & 5.6). The use of a needle to ascertain ideal

I

positioning for the instrument portal represents a departurefrom what was previously described in the carpus. However,the carpus is unique and the skin incisions for the instrumentportal are made prior to joint distention and insertion of thearthroscope merely to avoid entering an extensor tendonsheath. There are no such issues in the fetlock joint, or mostother joints for that matter. The practice of inserting a needleto ascertain the ideal position for instrument insertion and

If the arthroscopic portal is made in the more proximaldorsal pouch, the sheath can be advanced across the joint ina transverse direction without causing damage to themidsagittal ridge of the metacarpus. The position describedhere for the arthroscopic portal is different than in theprevious edition of this text (McIlwraith 1990a). It representsa modification initially suggested by Foerner (pers comm

surgical maneuverability is common to all joints other thanthe carpus. By making a skin incision with a scalpel and No.11 blade. the surgeon creates the instrument portal throughthe joint capsule (Fig. 5.7). The small egress cannula canthen be inserted through this portal without the trocar. Anarthroscopic examination can then commence. At thecompletion of arthroscopy, the skin incisions only are closed(Fig. 5.8).

Withdrawing the tip of the arthroscope further and moving iacross the sagittal ridge laterally (eyepiece moving mediallypermits inspection of the lateral condyle of the distal metacarpus as well as the proximal lateral aspect of the proxim~

phalanx (Fig. 5.12).The examination just described enables recognitiol

and characterization of synovial pad fibrotic proliferatiol(villonodular synovitis), other forms of synovitis, fragmentoff the proximal dorsal aspect of the proximal phalanx, wealines and erosions on the distal articular surface of Mcllosteochondritis dissecans of the midsagittal ridge ancondyles of Mclll, tears of plicae and joint capsule. articulacomponents of fractures of Mclll and proximal phalanx. ansubchondral cystic lesions of Mclll.

Diagnostic arthroscopy of the dorsalpouch of the fetlock Joint

With slight retraction of the arthroscope and looking acrossthe joint. the first area visualized is the proximal portion ofthe dorsal joint proximal to the articular cartilage of thedistal metacarpus, where the synovial membrane forms areflection (Fig. 5.9). At this transition zone, the synovium hasa flap, or pad. that varies in size, and the surgeon must befamiliar with the normal range (see Fig. 5.9). Synovial padfibrotic proliferation (villonodular synovitis) manifests as anenlargement of this flap. Apart from the flap, the synovialmembrane in the remainder of this dorsal area is non-villous.

The articular surface of the medial condyle and mid-sagittal ridge of McIIl can then be examined by rotatingthe arthroscope so that the lens is angled distad(Fig. 5.10). The tip of the arthroscope is then moved distad(eyepiece moving proximad) to inspect the dorsal articularedge of the proximal medial eminence of the proximalphalanx (Fig. 5.11). The synovial membrane of the dorsaljoint capsule is also evaluated during these maneuvers. Thesynovial membrane is notably more villous as one progressesdistad and villi can sometimes obscure the view of theproximal dorsal rim of the first phalanx. The synovial mem-brane attaches immediately adjacent to this rim, and use ofinstruments (including the egress needle) to allow improvedinspection of the first phalanx is common practice duringboth diagnostic and surgical arthroscopy in this area.

Arthroscopic examination of thepalmar or plantar fetlock joint

This examination can be performed with the horse in dorsIor lateral recumbency, the position varying with thcondition being operated. The authors preferred later!recumbency when operating on fragments associated witthe palmar/plantar aspect of the proximal phalanx in tbpast, but now use dorsal recumbency for all evaluation~conditions in the palmar/plantar compartment. While flexiofrom an assistant is sometimes needed, advantages includless hemorrhage, convenient operating position for plant~(palmar) chip fragments, as well as sesamoid fragmen1and the ability to put instrument portals in either medial (lateral pouch.

Insertion of the arthroscope

The joint is prepared for surgery and distended by placing thneedle in the palmar pouch using the approach described bMisheff & Stover (1991). With the joint distended, a skiincision is made with a No. 11 blade in the proximal part (

the bulging capsule (Fig. 5.13). The arthroscopic sheath andconical obturator are inserted perpendicular to the skininitially, and then are directed distad (Fig. 5.14). The fetlock isin 30-450 flexion at this time to facilitate passage betweenthe distal metacarpus/metatarsus and the proximal sesamoidbones. The degree of flexion is controlled by an assistant andthe flexion angle varies depending on the area beingexamined (for instance, increased flexion is used to bring theproximal palmar aspect of the proximal phalanx into view).

Diagnostic arthroscopy of palmar(plantar) pouch of the fetlock joint

Examination of the metacarpo- or metatarsophalangeal jointcommences with the arthroscope perpendicular to the skinand the lens oriented proximad (Fig. 5.15). The unusualsynovial membrane of the proximal recess of the joint can bevisualized. Rotation of the arthroscopic lens palmad allows

inspection of the apices of the sesamoid bones and theintersesamoidean ligament (Figs 5.16 and 5.17).

The tip of the arthroscope is then advanced distad (thiscan be done safely if the joint is flexed and distention ismaintained) to examine the articular surfaces of the sesamoidbones and the intersesamoidian ligament palmad and thearticular surface of the distal palmar Mclll dorsad (Fig. 5.18).Advancement of the arthroscope continues until the base ofthe sesamoids is visualized (Fig. 5.19) and. with increasedflexion. the proximal palmar rim of the proximal phalanx canbe noted (Fig. 5.20).

Diagnostic arthroscopy of the palmar or plantar pouch ofthe fetlock joint is now a commonly used procedure. Indi-cations for arthroscopic surgery in the palmar or plantarpouch include palmar/plantar proximal fragments off theproximal phalanx. apical. abaxial and basilar osteochondralfractures of the proximal sesamoid bone, osteitis of the axialportion of the sesamoid bones and tearing of the inter-sesamoidian ligament. diagnostic arthroscopy for synovitisand capsulitis as well as adjunctive visualization for reductionof lateral condylar fracture of Mclll/MtlII and assessment ofassociated damage. For diagnostic examination of a capsulitisor a suspected osteoarthritis problem. inspection of the dorsalcompartment is performed initially. followed by palmar orplantar examination in most situations.

Removal of osteochondral fragmentsfrom the proximal dorsal aspectof the proximal phalanx

Before the advent of arthroscopy, surgical removal of thesefragments was not routine, because some surgeons questionedthe benefits of surgical invasion of this area with arthrotomy(Raker 1973, 1985, Meagher 1974). Now, a horse withproblems referable to the fetlock joint and radiographicallyevident fragments associated with the proximal dorsal aspectof the first phalanx is a candidate for arthroscopic surgery.Arthroscopic surgery can provide a faster return to fullfunction and help minimize the degenerative changes thatcould possibly develop. All the advantages of arthroscopicsurgery discussed in Chapter 4 relative to the carpus areequally applicable when discussing arthroscopic surgery in

The indications for arthroscopic surgery have been previouslylisted.

Of probably increased importance is the needatraumatic surgery. The dorsal joint capsule

proximal first phalanx tend to be less forgiving to

radiographic and arthroscopic manifestations ofproximal dorsal chip fractures vary (Figs 5.21-5.27). Theremay be fresh fracture fragments or more chronic roundedfragments. The typical fragment involves the proximaleminence, but in some situations (more typical in the racingQuarter Horse), the fragments extend distad into fibrous jointcapsule attachments (see Fig 5.24). Frontal fracturesappropriate for internal fixation are considered separatelybelow.

Most importantly, all fragments, if accompanied byclinical signs, are indications for surgery. The damage evident

arthroscopically will always be more extensive than what isseen on radiographs. Consequently, many referred cases areoften

ones with persistent evidence of synovitis and capsulitisdespite medical therapy and relatively minor fragmentation

or with only a radiographic defect off the proximal phalanx(Fig. 5.25). Occasionally the fragment will be free withinthe

joint (Fig. 5.26). Uncommonly, the fragment is embedded

in

the dorsal joint capsule. and this may be difficult toascertain from the radiographs. The neophyte arthroscopistshould

try initially to limit his cases to those involvingfresh acute chips that are both loosely attached to the boneand accessible.

The location of these fragments, as represented by one ofthe author's (C.WM.) publications reporting on 439 fetlockjoints

in 336 horses, is given in Tables 5.1 and 5.2.

TechniqueFor all cases of proximal dorsal fragments of the proximalphalanx, the arthroscope is inserted through a proximallateral

portal as previously described. The instrument andarthroscopic approach for operating on chip fragments offthe

lateral and medial eminences respectively, are representeddiagrammatically in Figures 5.28 and 5.29. We recommendperforming

all arthroscopic surgery in the dorsal pouch of thefetlock joint with the same arthroscopic portal in theproximal lateral aspect of the dorsal pouch. After a completediagnostic

arthroscopy, the osteochondral fragments are

Metacarpophalangeal and Metatarsophalangeal joints

Fig. 5.21Removal of a small chip fragment (arrow) off the proximaldorsal medial eminence of the proximal phalanx. (A and B)Lateral-medial and DLPMO radiographs. C, Arthroscopicviews before (C), during elevation (D), during removal withFerris-Smith rongeurs (E), curetting defect. continued

If a fragment is present on the proximal lateral, it is removed first. A lateral instrument portal is

M5.5). The needle placement is lateral and midway down

incision, and the instruments are then placed. If afragment is present, a medial instrument portal is

--

5.25).

If a synovial pad fibrotic

.it can usually be removed through the same

the instrument portal is created, the tip of themust be located sufficiently proximad to avoid

damage to the arthroscope. By using the proximal

.The lesion is initially evaluated with(or the egress cannula), as in the carpal joints. The

.manifestations of the fragments vary con-and cannot usually be predicted from the radio-a fresh chip, the fracture line may be evident, the

lesion Overall (%)

96 (28.6)140 (41.7)63 (18.7)37 (11.0)

336

RH (%)

87 (28.0)124 (39.9)63 (20.3)37(11.8)

311

TB RH (%)

62 (33.0)93 (22.7)19 (10.1)14 (7.4)

188

QH RH (%)

25 (21.0)27 (22.7)44 (37.0)23 (19.3)

119

Others (%)

9 (36.0)16 (64.0)

25

Fragments onlyFragments + other fetlock lesionsFragment + carpal arthroscopyFragment + carpal arthroscopy + other fetlock lesions

Total

TB, Thoroughbred; QH, Quarter Horse, RH, racehorse.

Source: from Kawcak & Mcllwraith 1994.

fragment can be moved easily and is attached only at thesynovial membrane reflection. Displacement of the fragmentfacilitates identification and removal. Figure 5.21 illustratesthe sequence of events in removing a fresh fragment,including elevation. removal with Ferris-Smith rongeurs,curetting of the defect. removal of small pieces with ethmoidforceps, and lavage. In other cases the cartilage over thefragment is intact and elevation is required to definethe fragment. With larger fragments, the attachments of thefragment at the joint capsule may well be more extensive(Fig. 5.22). With mor~ chronic chips. the fragments tend tobe more rounded (Fig. 5.23). Some fragments have deepattachments in the joint capsule and require more separation(proximal Fig. 5.24). In some cases. the dorsoproximal rim ofthe first phalanx may only show a defect on lateromedialradiographs. but an oblique radiograph will show a small

fragment.

Sometimes the fragment can be recognized only asa roughening of the proximal phalanx. Occasionally, the chipis

embedded in the joint capsule, and this situation can berecognized if the fragment projects into the joint; otherwise,

such a density will probably not be found, and the finaldiagnosis of a capsular mass is based on the absence of afragment on arthroscopic examination despite its presenceon radiographs. Finally, fragments may already be totally freewithin the joint (Fig 5.26).

The grasping forceps commonly used to remove thefragments are Ferris-Smith intervertebral cup rongeurs(Fig. 5.21E). Low-profile 4 x 10 mm Ferris-Smith rongeurshave the ideal combination of strength and ability to accessthe fragment. As in the carpus, the use of forceps that canenclose the fragment minimizes the risk of leaving fragmentsin the joint. Twisting of the instrument to ensure breakdownof soft tissue attachments is carried out before withdrawal ofthe fragment.

The surgical manipulations to remove the fragmentwill depend on the arthroscopic features described above. A10 x 4 mm Ferris-Smith low-profile rongeur forceps is used toremove a totally free chip. If a fragment is small, fresh, andhas minor soft tissue attachments as ascertained by palpationwith the egress cannula direct removal with forceps is alsoappropriate. For all chips with significant attachments, thefragment is initially freed by using a periosteal elevator. Forchips that have a strong fibrous union, the elevator is used topry the fragment off the bone. The elevator can also be usedto break down capsular attachments to the dorsal aspect ofthe fragment. A curette is useful for more strongly attachedfragments. Because of suspected sensitivity of the dorso-proximal area of the fetlock joint, the surgeon should limitremoval when it has fibrous joint capsule attached to it(Fig. 5.30 and 5.31).

If a fracture line extends distad deep into the capsularattachment area and it is not displaced, surgical removal isnot indicated. Fixation with a small fragment screw issometimes indicated (see below).

After removal of the fragment, the defect remaining isinspected (see Figs 5.21, 5.22 and 5.30), as is the nearbyarea of dorsal capsule, to ensure that no fragments remain.This latter inspection must involve palpation as well asvisualization, as the fragments can merge into the capsule.The defect commonly has some tags or raised edges ofcartilage that can be removed with a pair of ethmoid or2 x 10 mm Ferris-Smith rongeurs (the pointed nose enablesthese forceps to enter the narrow areas where the fragmentwas removed). Alternatively, a curette may be used. Debride-ment of the bone is done carefully with a small (2-0) curettewith care taken not to cause damage to the fibrous joint

capsule (Figs 5.31).Variable degrees of articular cartilage damage on the

distal metacarpal or metatarsal condylar surface may benoted. In many cases, no damage is apparent, but varyingdegrees of wearline formation are apparent in some cases(Fig. 5.31C) and full-thickness erosion may be seen in othercases (Fig. 5.3ID). When these lesions are more severe, theprognosis is not as favorable (Kawcak & McIlwraith 1994).

Unless a capsular mass projects into the joint. it is notAlso. it is not considered necessary or beneficial to

arthroscopy in such a case has been to ascertain.' -of the radiographically apparent mass. If the

of the joint is in satisfactory condition. the prog-is still good with an osseous mass remaining in the

the size or number of fragments that can

undergo surgery. The surgeon must considerbone being removed. the amount of exposed

bone being left in the joint. and the amount of

created by the arthroscope or instrument portals.rather to the amount of capsular attachment to the

the joint is flushed with fluid byopen egress cannula over the site of the defect.

portals are sutured and the leg is bandaged. Theis maintained for at least 2 weeks after surgery.

walking commences after 1 week. With simple freshthe horses can be put into training after 6-8 weeks.

horses with more extensive involvement, the con-time is increased for a variable period up to

after surgery, but some veterinar-.As discussed in the section concerning the

.-to the patient's recovery is

results with arthroscopic surgery for uncomplicated

fractures are associated with severe capsulitis. wear lines.osteoarthritis. or extensive fragmentation of the proximal firstphalanx. the progn!;)sis decreases accordingly. As with thecarpus. surgical intervention can still improve the status ofthese patients. but communication to owner and trainer isimportant to ensure that no one is disappointed. Even withsuch precautions. however. some people have short memories.

The results of arthroscopic surgery in 74 fetlock joints of63 horses (35 Thoroughbreds and 28 Quarter Horses) over a2-year period were initially reported by Yovich & Mcllwraith(1986). Larger numbers have replaced these data. The resultsof arthroscopic surgery were reported in 1994 in 336 horseswith 572 osteochondral fragments removed from 439 fetlockjoints (Kawcak & Mcllwraith 1994). Of these horses. 311were racehorses. including 188 Thoroughbreds. 119 QuarterHorses. 2 Standardbreds. 1 Racing Arabian and 1 racingAppaloosa. There were 25 non-racehorses. A single meta-carpophalangeal joint was operated on in 220 horses. andboth metacarpophalangeal joints were operated on in 97horses. a single metacarpophalangeal joint in 17 horses. bothmetatarsophalangeal joints in one horse and all 4 fetlockjoints in one horse. Fragmentation of the proximal phalanxwas the only lesion in the fetlock joints of 96 horses. Along

with fragmentation, 140 horses had other lesions in thefetlock, comprising 64 with wear lines. 11 with articularcartilage erosion. 15 with chronic proliferative synovitis. 4with osteochondritis dissecans, and 45 with a combinationof the above lesions. Carpal arthroscopy for the removal ofosteochondral chips was performed concomitantly in 100 ofthese horses (Table 2).

Follow-up was available for 286 horses (85.1%): 208(73%) returned to their previous use. of which 153 horses(73.6%) returned to the same level of performance and55 (26.4%) returned to performance, but at a lower class; 18horses (6.3%) developed another fragment and 60 (21 %) ofhorses did not return to their previous use. Of the 270racehorses with follow-up. 196 (72%) returned to racing and141 (51.7%) of these raced at the same or a higher level.18 (6.6%) of the racehorses developed another fragment and56 (21.0%) were in the failure category. Of the non-racehorse group, 12 of 16 (75%) returned and 4 (25%) didnot return to their previous use at the same level ofperformance. The difference of return to previous use betweenracehorses and non-racehorses was not significant. Theoverall success rate in horses with fragments only returningto use was 85.9%; with fragments and other fetlock lesions. itwas 75%; with fetlock fragments and carpal arthroscopy con-comitantly. it was 68.6%; and with fragments plus carpalarthroscopy and other fetlock lesions, it was 80.6%.

In a third study done to examine the longevity ofpostoperative careers and quality of performance of 461Thoroughbred racehorses after arthroscopic removal ofdorsoproximal osteochondral fragments from the proximalphalanx. 659 chip fragments were removed arthroscopicallyfrom 574 joints and 461 horses presented for lameness ordecreased performance attributable to the chip fractures(Colon et al 2000). It was found that 89% of the horses(411/461) raced after surgery and 82% (377/461) did so atthe same or a higher class; 68% of the horses raced in astakes or allowance race postoperatively. This paper con-firmed that the quantity and quality of performance was notdiminished after arthroscopic treatment of dorsoproximalfragments, and that surgical removal of a chip fragmentpreserved the economic value of a racing Thoroughbred.allowing a rapid and successive return to racing at theprevious level of racing performance (Colon et al 2000).Horses that raced before and after surgery (258) had anaverage of 8.4 starts (median = 6) before surgery and 13(median = 11) after surgery. The average time between surgeryand first postoperative start was 189 days (median = 169);

87% of the horses racing before surgery (224/258) returnedto race at the same or higher class. The average earnings perstart after surgery was less than the average earnings beforesurgery in 61 % of these horses and greater in 32%.

Colon et al (2000) considered the 11 % postoperativefailure rate to be pessimistic due to various factors. It wasnoted that horses that did not race after surgery tended to beolder at the time of surgery and had raced more times pre-operatively. They concluded that the lack of return to racingwas not related to chip incidence. location or size, as these didnot differ between the raced and unraced group. They

carefully measured fragment size and concluded that it didnot affect post-surgical racing prognosis: 48% of the surveyedhorses had at least one fragment larger than the mean and87% of these raced after surgery. They concluded that thehypothesis that "the smaller the chip fragment, the better theprognosis" was rejected by these findings. However, theynoted that it was not possible in their study to compare post-operative racing performance to arthroscopic visualization ofarticular cartilage health or associated intra-articularcartilage lesions. They did point out, appropriately, thatusually the articular cartilage damage is not severe and canbe managed medically.

osteochondral fragments on the proximal dorsal rim, anradiographs are used to make the definitive diagnosis. VIhave encountered cases in the hind limbs bilaterally an.because of the consistent location of these fracturtinvolving both the proximal medial eminence and sagittgroove, a developmental predisposition may be present.

In the previous edition of this book, the use of rest w~advocated, as these fractures can heal (McIlwraith 1990aHowever, since that time, cases have been encountered that illnot heal and continued to cause clinical signs. The reconmendation now is to provide compression of these fractur!with 2.7 mm AD/ ASIF cortical screws.

Arthroscopic surgery is performed with the norm.arthroscopic approach to the dorsal pouch and with tblimbs in extension. Examination of the joint will confirm tbpresence of the fracture (Fig. 5.33). Needles are placed tascertain ideal positioning of the screw and, after a staincision is made in the appropriate location, a 2.7 mm holedrilled obliquely down through the fracture fragment. Tbhole is generally perpendicular to the fracture line. Radiograplare made to confirm appropriate positioning and that tbglide hole is beyond the fracture line. A 2.0 mm hole is cortinued beyond this. After counter-sinking, a 2.7 mm diamete36 mm long cortical bone screw is then placed to comprelthe fracture. Debridement is then performed in the fracturline, if appropriate. The manifestations at the fracture linwill vary and sometimes no bone is required to be remove(see Fig. 5.33); other times, debridement in a comparablfashion to a slab fracture is required.

Arthroscopic removal of dorsoproximalchip fractures of the proximal phalanxin standing horses

This technique has been described and reported in 104horses (Elce & Richardson 2002). Given skilled technique, itis feasible to perform arthroscopic surgery in the dorsalaspect of the fetlock in this fashion. However, we would onlyrecommend it if, for some reason, general anesthesia is some-how not possible or inconvenient. Throughout this textbook,the authors recommend surgery under general anesthesia.

Erosions of articular cartilage andsubchondral bone disease on proximaldorsal eminences of proximal phalanx

Treatment of slnovial Rad fibroticproliferation (vilionodular synovitis)

As seen in the carpus, there is a spectrum of disease on theproximal dorsal aspect of the proximal phalanx ranging fromseparation of articular cartilage and loss of articular cartilageto degenerative disease of the subchondral bone. Previouslydiscussed osteochondral fragments are considered to bepathologic fractures and are the end result of a gradation ofmicrodam~ge, microfractures, and cellular death (Kawcak et al2000). This range of lesions occur in the same locations aspreviously described for osteochondral fragments and thesurgical management is the same.

The referring clinical signs are also similar, but radio-graphically there may only be a suspicion of disease. However,on arthroscopic examination, the various manifestations ofarticular cartilage separation (Fig. 5.32A), articular cartilageerosion (Fig 5.32B), and subchondral bone disease (Fig 5.32Cand D) are encountered. Separated cartilage and bone isremoved. Defective bone is debrided (larger pieces removed),and the area lavaged. The prognosis is comparable tocompletely separated osteochondral fragments in this area.

The condition initially designated as villonodular synoviti(Nickels et al19 76) and later described as chronic proliferativsynovitis (van Veenendaal & Moffatt 1980, Kannegieter, 199Cis seen in the metacarpophalangeal joint. It involvesproliferative response from the synovial pad in the proximcdorsal aspect of the joint and, therefore, the term synovicpad fibrotic proliferation (Dabereiner et al19 9 6) is preferre(

The term pigmented villonodular synovitis was originallused to describe pedunculated growths forming in thsynovial linings of tendon sheaths and joint in man Gaffe et c1941). These fibrous masses were polyp-like formations th.originated from the synovial membrane and were often pi~mented with hemosiderin. Villonodular synovitis in human:therefore, should not be confused with enlargement of thsynovial pads of the equine metacarpophalangeal joint.

Classically, the condition was initially demonstrated wit:contrast arthrography, and it has been treated successfullwith arthrotomy (Nickels et al1976, Haynes 1980). Neithecontrast arthrography nor arthrotomy is used anymorcbecause of the development of ultrasound examination idiagnosis (Steyn et al1989) and arthroscopic surgery as thtreatment technique. The synovial pad of the metacarp(phalangeal joint is a fold (plica) of fibrous connective tissulocated in the proximal recess of the dorsal compartment (

Treatment of frontal fractures ofproximal dorsal aspect of the proximalphalanx using lag screw fixation

Frontal fractures of the dorsal aspect of the proximal phalanxoccur regularly. The clinical signs are very similar to other

(Dabareiner et aI1996). All the horses had lameness. jointeffusion. or both of these clinical signs. associated with one orboth metacarpophalangeal joints. Bony remodeling andconcavity of the distal dorsal aspect of McIII immediatelyproximal to the metacarpal condyles was identified by radio-graphy in 71 joints (93%) (Fig. 5.34); 24 joints (32%) hadradiographic evidence of a chip fragment located at theproximal dorsal aspect of the proximal phalanx. Fifty-fourjoints (71%) were examined by ultrasound. The mean:t SDsagittal thickness of the synovial pad was 11.3 :t 2.8 mm.(The authors also reported that the synovial pad wasconsidered abnormal if the thickness was greater than 4 mmon the sagittal view. the distal margin was rounded. or hypo-echoic regions were observed within the pad.) Seventy-ninepercent of the horses had single joint involvement. with equaldistribution between the right and left forelimb. In addition topre-surgical diagnosis of this condition. it is also quitecommon to encounter thickened and enlarged synovial padsat arthroscopic surgery (usually when doing the surgery forremoval of a proximal dorsal fragment from the proximal

phalanx) (Mcllwraith 2002).The surgical approach used when operating on horses

with this condition arthroscopically is illustrated in Figure5.35. The authors in most cases use a single instrumentapproach. A two-instrument approach has also been described

the metacarpophalangeal joint at the joint capsule attach-ment to Mcill. The synovial pad is normally 2-4 mm inthickness and tapers to a thin edge at its distal border (White1990). Its function is unknown, but its structure and locationsuggest that the pad acts as a contact interface or cushionbetween the proximal dorsal rim of the proximal phalanx andthe dorsal surface of distal third metacarpal bone (Mcill)during full extension of the fetlock joint (White 1990).Repetitive trauma during fast exercise can result in irritationand enlargement of the synovial pad and development ofclinical signs of lameness and chronic joint effusion thatoften resolves temporarily with rest and intra-articularmedication. There is commonly radiographic evidence ofbone remodeling, with a concavity at the distal dorsal aspectof Mcill, and this is suggestive of synovial pad proliferation(Fig. 5.34A). Ultrasound is now the method of choice tofurther define this proliferation (Fig. 5.34B). Although thiscondition is commonly seen in the racehorse, it has been seenin other horses not subjected to fast athletic exercise (loSasso& Honnas 1994), and in the previous edition of this text, acontrast-enhanced view of the disease in a mule waspresented.

The medical records, radiographs, and ultrasoundexaminations have been reported in 63 horses with

metacarpophalangeal joint synovial pad proliferation

sometimes be noted when the indication for arthroscopicsurgery was originally the removal of fragments. Conversely.fragments may be encountered off the proximal dorsal aspectof the proximal phalanx at the time of arthroscopic surgeryfor removal of a proliferated pad when the fragmentswere not visible with pre-surgical radiographs. Obviously,a complete examination of the dorsal pouch is done with anyof these arthroscopic procedures and lesions appropriatelydealt with.

In a report of 68 joints in 55 horses treated by arthroscopicsurgery, 60 joints (88%) had debridement of chondral orosteochondral fragmentation from the dorsal surface of thedistal metacarpus beneath the synovial pad (more frequentlydone than by us) and 30 joints (44%) had a bone fragmentremoved from the medial or lateral proximal dorsal eminenceof the proximal phalanx (Dabareiner et alI996).

Arthroscopic laser extirpation of metacarpophalangealsynovial pad proliferation has been described in 11 horses(Murphy and Nixon 2001). Eleven clinical cases were operatedon in this fashion and followed up. All were treated by intra-articular laser extirpation using either CO2 or an Nd:YAGlaser with arthroscopic guidance. Mean synovial padthickness, measured ultrasonographically, was 9 Inm, and 7(64%) of the horses had radiographic evidence of remodelingof the dorsal cortex of distal McIIl; 3 horses (27%) had con-current dorsal proximal fractures of the proximal phalanx.All 11 horses returned to training within 90 days of surgerywithout recurrence of the lesion. Nine horses (82%) sustainedrace training and apparently improved their performancefollowing surgery based on follow-up conversation with theowners. The use of the CO laser requires gas distention of

2the joint. The authors cited advantages with the laser tech-nique that included their ability to be used arthroscopically,better visualization of the joint, better access to lesions onboth sides of the sagittal ridge, reduced convalescence time,and better cosmetic and functional results. However, with ourcurrent abilities at conventional arthroscopic surgery, it isquestionable if these advantages exist anymore.

Postoperative management in cases involving proliferativesynovitis treated arthroscopically is the same as for thoseinvolving chip fragments of the proximal phalanx. Horsesthat have synovial pad proliferation without articularcartilage loss or proximal phalangeal fragments can return toracing in 8 weeks, whereas horses with more extensivecartilage damage or more significant proximal dorsal frag-mentation of the proximal phalanx should get 3-4 monthsbefore training is resumed.

Follow-up on 50/55 horses was obtained for the previouslycited study of Dabareiner et al (1996): 43 (86%) horses thathad surgery returned to racing, with 34 (68%) racing at anequivalent or better level than before surgery. Horses thatreturned to racing, at a similar or equal level of performancewere significantly younger than horses returning at a lowerlevel or not racing. In contrast, the same authors reported8 horses (8 joints) with synovial pad proliferation andremodeling of the distal dorsal aspect of McIIl being treatedmedically at the owner's request. Intra-articular sodiumhyaluronate was administered intermittently in these

(Mcllwraith 1990a. 2002). With the arthroscope in the lateralportal. the instrument portal is made medially. Dabareiner et al(1996) considered excision of a portion of the synovial pad tobe necessary if it was enlarged and inelastic when probedduring surgery or if hard nodules could be felt within the pad.The mass can sometimes be torn off by using grasping forcepsthat have a cutting edge (Fig. 5.36A and B). Alternatively, themass can be severed at its base by using a flat knife (Fig.5.36C and D) (see Chapter 2). Disposable scalpel bladesshould not be used because they may break within the joint.After severing the base. the proliferated pad is removed withFerris-Smith rongeurs (Fig. 5.36E) and the base trimmedwith basket forceps or a motorized resector. Proliferation ofthe synovial pad is more common medially than laterallyand. consequently. surgery often involves removal of themedial portion alone. However, examination should be madeto ensure that there is not similar proliferation in the lateralportion. If there is. the arthroscope is placed medially and theinstrument laterally to remove the lateral portion. In onereport in the literature. complete or partial excision of bothmedial and lateral synovial pads was achieved in 42/68 joints(Dabareiner et al1996). The medial synovial pad only wasexcised or trimmed in 21 joints and 5 joints had removallimited to the lateral pad.

Once the pad is removed, there may be some full-thicknesserosion with minor debris where debridement is indicated(Fig. 5.36F). More commonly. the bone is left alone. but ifthere are any elevated cartilage tags. these are trimmed. Ashas been previously noted. enlarged. thickened pads will

Arthroscopic Surgery of the Fetlock Joints

8 horses and systemic nonsteroidal anti-inflammatory medi-cations were also administered for variable periods. Three(38%) of the medically treated horses returned to racing andonly 1 horse raced better than the pre-injury level.

Treatment of other forms ofproliferative synovitis

Occasionally, forms of proliferative synovitis that are notlocalized to the dorsoproximal aspect of the joint are seen (seeChapter 3). Typically, these cases present as chronic synovitisand capsulitis that is non-responsive to symptomatic intra-articular or systemic anti-inflammatory treatments. In somecases, diagnostic arthroscopy has revealed proliferated,thickened, and enlarged synovial villi in the dorsalcompartment of the metacarpophalangeal joint (Fig. 5.37).The treatment has been resection of these villi, and theoverall results have been good.

Treatment of osteochondritis dissecansof the distal dorsal aspect of Mc111/Mt111in the metacarpopharangeal andmetatarsophalangeal joints

There is a divergence of opinion as to what is consideredosteochondritis dissecans (OCD) within the fetlock joint andalso those entities that might be considered to be appropriateto include in the term developmental orthopedic disease(Mcllwraith 1993). It is undisputed that OCD of the dorsalaspect of the distal McIII and MtIII is a manifestation of OCDand this is the condition described below. The condition wasinitially described as OCD of the sagittal ridge of the thirdmetacarpal and metatarsal bones (McIII/MtIII) (Yovich et al1985). but this term has been modified after recognition that

the disease process commonly extends onto the condyles ofMclII and MtlII (Mcilwraith & Vorhees 1990). These caseswere evaluated and treated on the basis of having clinicalsigns; the problem was assessed in 65 horses (Mcilwraith &Vorhees 1990). In one radiographic study, OCD changes onthe dorsal aspect of the sagittal ridge of MclII or MtIII wasseen in 118/753 yearling Standardbred trotters with 61forelimbs and 147 hind limbs affected (GroendahI1992).

Fragments from the proximal palmar/plantar margin ofthe proximal phalanx have also been reported as osteochon-drosis (Foerner 1987, Nixon 1990), but it is not now generallyaccepted that osteochondrosis is the pathogenesis. Thetreatment of this condition is described later in this chapter.The third condition described as OCD are proximal dorsalfragments of the proximal phalanx in young horses. Whilethese fragments, at least in racehorses, have long beenconsidered to be traumatic in origin, there is evidence some ofthese fragments having an osteochondrosis basis, at leastwhen they present in yearlings. The treatment of these con-ditions is also described in this chapter. Dorsal bonyfragments in the metacarpo- and metatarsophalangeal jointswere diagnosed in 36 (4.8%) of 753 yearling Standardbredtrotters on a radiographic survey (Groendahl19 92) and wereseen in 34 forelimbs and 14 hind limbs. A fourth conditioninitially described as OCD of the palmar metacarpus (Hornoffet a11981) is now accepted to be a traumatic entity and nota syndrome of osteochondrosis. It will not be consideredfurther here, as it is not an arthroscopic surgical condition.

Osteochondritis dissecans of the distal dorsal aspect of theMclII/MtlII can occur in both metacarpo- and metatarso- !phalangeal joints, but it is more common in the latter. The.'lesions vary in their radiographic manifestations, from a Isubchondral defect to defects associated with fragments;(Fig. 5.38). In some cases, fragments break away completelyfrom the primary lesion and become loose bodies. Thepresenting clinical signs include synovial effusion of thefetlock joint with or without lameness. The horses are usuallyyearlings (Yovich et al1986). In most instances, the patientsare weanlings to yearlings and quite often are presented fortreatment prior to sale. In some instances, training andracing may have occurred before the symptoms develop.Although the degree of lameness varies, a positive responseto a fetlock flexion test is usually elicited, and radiographs iconfirm the presence of lesions associated primarily with thesagittal ridge of MclII/MtIlI. ;

For purposes of treatment decision and prognosis, the jlesions have been divided into three types:

.Type I is that in which a defect or flattening is theonly visible radiographic lesion

.Type II is that in which fragmentation is associatedwith the defect

.Type III is that in which there is a defect or flatteningwith or without fragmentation plus one or moreloose bodies.

Oblique radiographs should be taken as well as dorsopalmar(plantar) and lateral/medial radiographs for the purposeof discerning the medial or lateral condyles of MclII/MtlIl(Mcilwraith & Vorhees 1990). Based on an initial study

Fig. 5.38Examples of the radiographic appearance of osteochondritisdissecans (OCD) of the fetlock joint (A) Type I OCD of themidsagittal ridge of the metatarsophalangeal joint. (B) Type IIOCD. (C) Type III OCD.

Yovich et al19 85), it was felt that Type II and Type III OCDesions should be treated surgically and many Type I lesionsrvould resolve, In a second study of 15 cases with Type Iesions that were treated conservatively, 12 resolved clinicallymd

8 of these showed remodeling of the lesions withmprovement on radiographic examination (Mcilwraith &torhees

1990), In 3 cases the clinical signs persisted: in 2 ofhese, the radiographs showed no ch~nge and the horses:ventually underwent surgery, whereas, in the other case, the:linical and radiographic signs progressed and the horse waslot operated on,

In 8 cases of Type II lesions where owners requested:onservative management, 2 eventually underwent surgery)ecause

of the persistent clinical signs, Clinical signs)ersisted in 5 others, but surgery was not performed, The

:linical signs improved in only 1 horse, In most of these casesrvhere clinical signs persisted, the fragmentation also)rogressed

radiographically. It was also clear in this study:hat clinical signs of effusion may appear before definitive:adiographic

changes. Progression of some Type I lesions wasloted: such cases do not develop osseous fragmentation, but:he

lesions progress to become larger defects, particularly on:he condyles (seen on oblique view radiographs). Some cases

Jf Type II lesions improved radiographically. These were~enerally cases with small fragments that fused to the parent-Jone

such that a spur resulted.Based on the above knowledge, arthroscopic surgery is;onsidered

the appropriate treatment if fragments are~resent (Type II and III lesions). In other cases in which alefect only is detectable radiographically, the decision for;urgery is based on the degree of clinical signs, the size andocation of the defect, and the planned use of the horse.

The arthroscopic approach is the same as that forragments off the proximodorsal aspect of the proximal

Jhalanx or synovial pad proliferation, using a proximally orlistally placed instrument portal, depending on the locationJf the fragment or loose body (see Fig. 5.39). When operatingIn metatarsophalangeal joints, an effort must be made tolchieve

complete extension. In some cases, the OCD lesionllanifests as a defect within the sagittal ridge (Fig. 5. 40A and

B), and curettage is performed. More commonly, osteochondralragments may be within the defect or have loose attach-llents

to the area (Fig. 5.40C-E). In these cases, the fragments removed and any defective articular cartilage is debrided:Fig.

5.40F). Loose fragments are located and removed (usuallywith Ferris-Smith rongeurs). As mentioned previously,Ilndermined

cartilage may extend medial and lateral from the,agittal ridge of McIlI and MtlII, and it must also be debrided.JCD

can also occur on the metacarpal or metatarsal condyles:Fig. 5.41). Type III lesions are treated with fragment removalmd debridement (Fig. 5.42).

Disease and fragmentation of the proximal dorsal aspect ofthe proximal phalanx typical of OCD is seen quite commonlyIn

young horses. The radiographic manifestations are of a,mall fragment on the proximal dorsal aspect of the proximalphalanx (Fig. 5.43). The arthroscopic manifestations canvary, as illustrated in Figure 5.43. In some instances, therewill be a flap with diseased bone underneath, typical of OCD

(Fig. 5.43B). But in most instances. there will be a roundedfragment (Fig. 5.43C and D). Rarely, extensive fragmentationmay be present (Fig. 5.43E-G).

Aftercare in these cases is the same as for a chip fragmentoff the proximal dorsal aspect of the proximal phalanx. Manyof these horses are young and therefore have long periods forconvalescence before being put into training.

The prognosis is based on the appearance of the jointduring surgery as well as on the age of the horse. If there isno other damage or only a minimally sized defect in thesagittal ridge, the prognosis is good. Follow-up data revealthat when extensive lesions extend medial or laterad from thesagittal ridge or distad to involve the loaded area of the

was unavailable. Surgery was successful in 16 (57.1 %) of the28 cases and 12 were unsuccessful (42.8%). Of the 12unsuccessful cases. 7 were still considered to have a problemin the fetlock joint (25%): 3 were unsuccessful for otherreasons; 1 was unsuccessful for unidentified reasons but wasconsidered to be normal in the fetlock joint; and 1 horse died.The success rate was also found to be related to other factors.There was a trend for the success rate to be higher for surgeryin hind limbs compared to forelimbs. On the one hand. in theforelimbs only 2 cases were successful and 6 were un-successful. whereas in the hind limb 7 were successful and 3were unsuccessful. When both fore and hind limbs wereinvolved. there were 7 successes and 3 failures. Type IIIlesions had 4 successes and 4 failures. whereas Type II lesionshad 10 successes and 4 failures (difference not statisticallysignificant). Only 3/12 cases with erosions or wear linespresent at arthroscopy were successful. whereas 13/16 withno erosions were successful (p = 0.0029). Probably related tothat. there was a significantly inferior result when a defectwas visible on the condyle on oblique radiographs. When adefect was visible. 6/13 were successful. whereas if a defectwas not visible. 10/15 were successful (p = 0.0274). Osteo-phytes were also negative prognosticators (3/9 with osteo-phytes on the proximal phalanx were successful. whereas

I13/19 with no osteophytes were successful).It was concluded that surgical management of Type II and '

Type III lesions will allow athletic activity in a fair number ofcases. but clinical signs will persist in 25%. Whether thesurgery will be successful or not will be affected by the extentof the lesions. as evident arthroscopically (and in someinstances. radiographically). as well as by the presence ofosteophytes. erosions. and wear lines. Since the Mcllwraith &Vorhees (1990) paper was published. the first author feels thesuccess rate has improved further because of earlierintervention and. particularly with radiographing horses at ayoung age to ensure clean joints at yearling sale.

articulation. clinical problems may arise when the horseengages in athletic activity.

In a series of 42 horses that were operated on witharthroscopic surgery. there were a few Type I lesions (usuallyoperated on as they had not responded to conservativetreatment or if an individual joint in a horse being treated fora Type II or Type ill lesion happened to have a Type I lesion).Forty-two horses in this series reported included 20Thoroughbreds. 8 Quarter Horses. 7 Arabians. 4 Warmbloods.1 Standard bred. 1 Percheron. and 1 Appaloosa (McIlwraith& Vorhees 1990). Forelimbs were involved in 10 horses. hindlimbs were involved in 15 and both fore and hind limbs wereinvolved in 17 horses. One fetlock joint was operated in 10horses. 2 fetlocks in 17 horses. 3 fetlocks in 1 horse. and4 fetlocks in 14 horses. Forty-eight cases involved theproximal 2 cm of the sagittal ridge. where 11 extended distalto this point. In 44 instances. lesions involved the lateraland/or medial condyles of the metacarpus or metatarsus.with or without lesions of the sagittal ridge.

Of the 42 horses operated on. follow-up was obtained in28. eight horses were convalescing and in 6 the follow-up

Debridement of subchondral cysticlesions of the third metacarpal bone

regularity (Nixon 1990, Mcllwraith 1990b). Most horses areaged 2 years old or less when clinical signs become apparentand they usually have a history of recently increased physicalactivity (such as entering athletic training). The diagnosis isconfirmed with radiographs (Fig. 5.44A and B). As with most

The distal Mclll is one of the less common locations forsubchondral cystic lesions. but they do occur with relative

subchondral cystic lesions. they occur in a location subject tomaximal weightbearing during the support phase of thestride. Once a cystic lesion becomes clinically apparent. theprognosis for athletic soundness is variable and appears tobe dependent on several factors. including the anatomiclocation of the lesion. the presence of any associateddegenerative changes in the joint and the treatment regime(surgical or conservative) chosen (Bramlage 1993).

Prior to the use of arthroscopic surgery. most cases weremanaged conservatively and empirically and with limitedsuccess (Mcllwraith 1982). If conservative therapy was notsuccessful. a dorsal arthrotomy was recommended surgicallyto debride the lesion and this technique has been morerecently replaced by arthroscopic surgery. The technique isless invasive and provides the advantage of clear visualassessment of the articular surfaces of the joint.

The arthroscopic approach depends on the location of thecystic lesion. The majority of lesions are on the medialcondyle of the distal metacarpus. in which case the arthro-scope and the instrument are both placed medially (Fig. 5.45).In order to expose the opening of the subchondral cysticlesion. flexion is required. and so having the arthroscope onthe same side obviates the potential problem that flexioncreates (sagittal ridge interfering with the arthroscopicposition). The arthroscope is placed laterally for a cystic lesionon the lateral condyle or the sagittal ridge. With flexion. theopening of the cystic lesion can be visualized (Fig. 5.44). Aneedle is used to ascertain the ideal position for debridement;this tends to be distal and axial over the cystic lesion. Thecystic lesion is then debrided with a curette and piecesremoved with forceps. The cartilaginous edges are trimmedand debris removed by flushing. Drilling of the cystic lesion isno longer performed.

A 4-6-month lay-up period is recommended with thesecases. The initial 2 months involve stall confinement with aprogram of hand walking. A series of cases have been reported(Hogan et al1997) and serve as a basis for prognosis. Sub-chondral cystic lesions (SCLs) in the distal McIIl weresurgically treated in 15 horses. The median age at presen-tation was 18 months (range 10 months to 12 years) withlOllS horses less than 2 years old. The SCLs were confined tothe front limbs in all cases. with two horses having bilaterallesions. Lesions were isolated to the medial condyle of McIIlin 13 I 15 horses; a cystic lesion occurred in the lateral condylein 1 horse and in the sagittal ridge in another. One horse withbilateral lesions had an additional cystic lesion located in theright medial femoral condyle. Fourteen of 15 horses had ahistory of moderate lameness attributable to the metacarpo-phalangeal joint; the lesion was an incidental finding in1 horse. Duration of lameness ranged from 4 weeks to8 months and was either acute in onset or occurred inter-mittently and was associated with exercise. Fetlock flexionsignificantly exacerbated the lameness in all cases. Synovialeffusion was absent in 8 (53 %) of cases.

Cystic lesions were curetted arthroscopic ally in 12 horses.and through a dorsal pouch arthrotomy in 3 horses.Concurrent osteostixis of the cystic cavity was performed in 7of the horses. 12/15 horses (80%) were sound for intended

use following surgery. 2 horses did not regain soundness andfollow-up information was unavailable in 1 horse. The totalperiod of follow-up was 1-6 years. Follow-up radiographexaminations were available for 9 horses. Mild periarticularosteophyte formation and enthesophyte formation at thedorsal joint capsular attachments was present in 5 of the9 horses. Bony infIlling of the cystic lesion was detectable in8 horses and enlargement of the cystic cavity was observed in1 horse. Based on this study, it would appear that surgicaltreatment of SCLs in the distal McIlI should result in afavorable outcome for athletic use (Hogan et al1997).

Removal of axial osteochondralfragments of the proximalpalmar or plantar aspect of theproximal phalanx

result of fracture rather than a manifestation of osteo-chondrosis.

The principal radiological sign is that of a fragmentlocated between the base of the sesamoid bone and theproximal aspect of the proximal phalanx; it is usually halfwaybetween the sagittal groove and the lateral or medialeminence of the first phalanx and is not always associatedwith a defined defect on the first phalanx. Although initiallythe condition was considered peculiar to the Standardbred(Pettersson & Ryden 1982), cases occur in Thoroughbredsand the condition is reasonably common in Warmbloodbreeds.

Typically, the horses will be admitted with a history oflameness. Lameness at examination will be mild and.commonly, the history is that of subtle lameness reported bythe trainer and manifested at high speed as a rough gait orbreak in stride (Fortier et al199 5). In one series of cases of 82horses receiving lameness examination at admission. 17(21 %) horses had slight to moderate positive results on hindlimb flexion. Synovial effusion of the metatarsophalangeal ormetacarpophalangeal joint was reported in 19/119 (16%) ofhorses; 155/164 (95%) fragments were in the metatarso-phalangeal and 9/164 (5%) involved the metacarpophalangealjoints. The medial plantar eminence of the proximal phalanxwas the location of 114/164 (70%) fragments. Bilateral frag-ments were observed in 21 (18%) horses. whereas 15 (13%)horses had concurrent medial and lateral lesions within thesame joint. Standardbred racehorses represented 109 (92%)of those affected (Fortier et al 1995). In another series of26 cases. 23 of the horses were racing Standard breds and 3were racing Thoroughbreds (Whitton & Kannegieter 1994).The most common reason for presentation in this series wasan inability to run straight at high speeds. Only 8 horsespresented for lameness. although on examination, 19 werelame. A positive flexion test was recorded in 90% of affectedfetlock joints and effusion was present in 48%.

To be considered a surgical candidate, the patient musthave demonstrable lameness referable to the fetlock, inaddition to a radiographically demonstrable fragment(Fig. 5.46). The fragment can be identified on the lateral andflexed lateral views. Dorsoplantar radiographs taken with thefetlock flexed have also been recommended (Birkeland 1972),but the authors have not used this technique. For optimaldefinition of the location of the lesion. however, a specialoblique view with the tube at a 300 angle distad is useful(Fig. 5.46B). Both oblique views are essential as lesions canbe biaxial.

Non-surgical treatment usually lowers the horse'sperformance (Barclay et al 198 7). Arthroscopic surgery isnow the standard technique. Dorsal or lateral recumbencycan be used. The authors prefer dorsal recumbency as theinstrument portal can conveniently be made laterally ormedially. However. some flexion of the joint from an assistantmay be required. If the surgery is done in lateral recumbency,the side where the fragment is located should be up and thearthroscope and instrument approaches will be made fromthe same side. The arthroscope is placed in the plantar orpalmar

joint pouch. as previously described. after distending

These fragments, described as Type 1 osteochondral frag-ments of the palmar-plantar aspect of the fetlock joint(Foerner 1987), were initially reported as chip fractures(Birkeland 1987) and avulsion fractures (Pettersson & Ryden1982). Since that time, Foerner (1987) suggested that thiscondition is another manifestation of osteochondrosis basedon its incidence and age of occurrence of the fragments.However, more recent publications have argued for a traumaticetiology. Hind limb fetlock joints with plantar osteochondralfragments were collected from 21 horses (17 Standardbredtrotters, 4 Swedish Warmblood riding horses) and themorphology of the osteochondral fragments in adjacenttissues studied by dissection, high-resolution radiography,and histology (DaIin et al 1993). The fragments were attachedto

the short s~samoidian ligaments and had a smoothcartilage coverin'g on the surface facing the joint cavity.

Histology did not show any evidence of osteochondrosis. Theauthors suggested that plantar osteochondral fragments arethe

result of an outwardly rotated hind limb axis and sub-sequent point loading in the medial fetlock area. Repeatedhigh tension loads in the short sesamoidean ligaments maycause

fragments of tissue with osteogenic properties to avulsefrom the proximal phalanx into the ligament, later formingosteochondral fragments. This pathogenesis does not accountror

lateral fragments, which also occur occasionally. Otherwork by the same authors had shown that plantar osteo-chondral

fragments most often occur in the hind limbs andare more frequently in the medial part of the joint (Sandgren

~t al 1993). It has also been demonstrated that thesefragments develop early in life and are often possible to detect

~y radiography before 3 months (Carlsten et aI1993).A second study had been done on osteochondral fragmentsrom

the axial proximoplantar/proximopalmar region of the?roximal phalanx in 38 joints in 30 horses: 28/30% of thelorses

were Standardbreds and 28/30 had a low-gradeameness. All but one of the horses had hind limb involve-Dent.

Of 143 fragments removed, 71% involved the mediallspect of the joint and had to be dissected from a covering of:ynovial

tissue (Nixon & Pool 1995). The histologic appear-Lnce in these cases suggested that these fragments were a

\

The arthroscope is positioned to visualize the distalthe joint; an assistant may facilitate this step byflexion on the joint. After assuring the correct

portal is made distal to the arthroscopic, .5.47). The portal is made so that the

comes across transversely. Often, the fragment

can aid visualization. The fragmentseparated from the soft tissue with a knife and is

by using a Ferris-Smith cup rongeur (Fig 5.48).of this fragment leaves a defect within the joint

and short-digital sesamoidean ligaments, and any--

plantar defect in the normal phalanx isappropriate but is not usually necessary. Figure

and Figure 5.50 illustrates medial and lateral

condition is one of the few in equine arthroscopicfor which the use of sharp dissection is essential.

used, including a tenotomy

knife. a banana knife. a narrow bistoury. and an Arthro-LokTM retractable blade. We prefer a broad. flat blade. Thedisposable No. 11 blade should not be used because of therisk of breakage. Electrocautery probes have been used morerecently for this dissection (Boure et al1999).

The immediate postoperative care is the same as for otherarthroscopic procedures in the fetlock joint. A period of2-3 months rest before training resumes is recommended.

There have been two reports of treatment of these osteo-chondral fragments with follow-up. Whitton & Kannegieter(1994) reported on 21 horses. in which 16 horses had returnedto racing: 12 horses had improved their performance. while 3horses showed no improvement. and 1 horse was retired forother reasons. Degenerative changes within the fetlock jointwere detected at surgery in 8 horses. Four horses were treatedconservatively: 1 horse returned to its previous level ofperformance temporarily after intra-articular medication.1 horse showed no improvement. and 2 horses were restingat the time of the report.

A larger case series of 119 horses (109 Standardbredhorses) had follow-up in 87 racehorses and 9 non-racehorses(96). In 55/87 (63%) racehorses and 100% of 9 non-

racehorses, performance returned to preoperative levels aftsurgery. Fragment numbers or distribution and concurreOCD of the distal intermediate ridge of the tibia or tarsosteoarthritis were not significantly associated with outcomAbnormal surgical findings, consisting of articular cartila:fibrillation or synovial proliferation, were significant(p <0.001) associated with adverse outcome: these findinwere documented in 31 % of the 32 horses without successfoutcome and only 2% of the 55 horses with successful oucome (Fortier et al1995).

Arthroscopic excision of these fragments has beldescribed in 23 Standardbred racehorses using electrocautelprobes (Simon et al 2000). A 1.5% glycine solution in iArthropump was used to maintain joint dissectioTransection was performed using loop probes alone (alternatively, with hook electrocautery probes to dissect tIfragment free prior to Ferris-Smith rongeur removal. Thirtfive fragments in 28 joints were removed from either the 11or the right hind limb in 23 Standardbred racehorses. Six hibiaxial fragmentation. An ipsilateral (n = 9) or contralater(n = 26) triangulation approach was used. The autho

concluded that the loops and probes can be safely usedexcise osteochondral fragments of the plantar proximphalanx. They considered dissection using electrocautelprobes to be more precise and easier to perform than tIpreviously described sharp dissection technique. No folIo,up was given. It has since been recognized that glycine is nnecessary for this procedure.

Removal of fragments of the proximalsesamoid bones

Osteochondral fractures amenable to removal occur at tlapical, abaxial, and basal margins of the proximal sesamobones. Arthroscopic techniques for the removal of thefragments have been developed. Previous dogma had prposed limitations of fragment removal based on the sizethe fragment and the degree of attachment to the suspenso]and distal sesamoidian ligaments. However, current folio,up on the first author's cases that have been treated arthrscopically suggest that limitations should be redefined. ia generalization, the hypothesis that the prognosis wdecrease with greater involvement of both bone and s(tissue attachments is still valid. but the actual proportions ahigher than previously thought.

The diagnosis of sesamoid fractures is made radiographicaJ(Fig. 5.51) and special views are used to clearly delineate tlabaxial involvement. Arthroscopic surgery for the removalsesamoid fragments is performed with the horse in eithlateral or dorsal recumbency (the authors prefer the latteJThe technique for an apical sesamoid fragment is illustratlin Fig. 5.52. The arthroscope is placed in the most proximportion of the palmar or plantar pouch of the fetlock jointall cases. With partial flexion of the joint, a needle is usedascertain the ideal placement for the instrument portal. T]instrument portal can be ipsilateral or contralateral, aJboth techniques are illustrated in Figures 5.53 and 5.5

Sharp dissection is used to separate the apicalfrom the suspensory ligament using a flat blade.

.blade (Foerner-Scanlan elevator) is used to

the abaxial attachment (see Fig. 5.53).of the fragment, it is removed with Ferris-(see Fig. 5.53). Soft tissue attachments are

with basket forceps or a motorized resector. Thedebrided with a curette. Fragmentation of apical

-more than 1/3 of the articular surfaceconsidered ideal candidates for surgery. Apicalfragments in foals can be treated in the same

5.55).arthroscopic approach is used for surgery on

fragments. Case selection can sometimes be a

dissection with the flat blade is limited to severing thesuspensory ligament attachments (see Fig. 5.56C). It isimportant that the instrument portal is made appropriatelydistad so that the knife can sever the suspensory ligamentattachments from the abaxial fragment. After removal. thebone and cartilage are debrided with a curette. A motorizedresector is used to debride the suspensory ligament tags.

Fragmentation of both the apex and abaxial region of thesesamoid bone can occur concomitantly (Fig. 5.58). Thearthroscopic technique for these fragments is the same as forremoving them independently. Generally. the abaxialfragment is removed first. followed by the apical fragments(Fig. 5.58B-D).

Basal sesamoid fragments are candidates for arthroscopicremoval when no other pathologic changes are presentin the fetlock joint (at least on radiographs) (Fig. 5.59). Areasonable number of fragments are of sufficiently smallsize that their removal does not compromise the distalsesamoidian ligament attachments. The exact size limitationshave recently been defined (Southwood et al 1998).

-~ radiographs (Fig. 5.56) do not clearlyan abaxial fracture as articular. then a "skyline"

'. view should be taken (Palmar 1982).

approach is illustrated in Fig. 5.57. Sharp

'he technique is illustrated in Figure 5.60. Both ipsilateralnd contralateral arthroscope and instrument positions areossible.

The arthroscope is placed in the same fashion as forllrgery on apical and abaxial fragments. The instrument isrought in below the base of the sesamoid bone. Sharpissection is used to sever the fragments from the capsularnd

distal sesamodian ligament attachments. The defects arelen debrided (bone and soft tissue) and the joints lavaged~ig.

5.59 and 5.61).The results of apical, abaxial, and basal sesamoid fragments,

~spectively, have been documented recently. On reviewingle results of 82 cases of apical fractures of the proximal~samoid

bone of horses, follow-up data were obtained for 54~cehorses: 36/54 (67%) horses returned to racing, 28

52%) in the same class and 8 (15%) in a lower class; 14/1878%) horses with small apical fractures returned to racing,1

in the same class and 3 in a lower class. 11/19 (58%) withIrge apical fractures returned to racing and all raced in thewe class; 11/17 (65%) horses with apical-abaxial fractures~turned

to racing, 6 in the same class and 5 in a lower class.ic the horses that had raced before surgery, 33/40 (83%)

horses raced after surgery. Small fragments were classifiedwith a proximodistal length less than 10 mm or less than25% of the sesamoid bone, and large fragments had aproximodistallength more than 10 mm or more than 25% ofthe sesamoid bone (Southwood et al2000).

In a series of 47 cases of arthroscopic removal of abaxialfragments from the proximal sesamoid bone. follow-upinformation was obtained for 41 horses (35 racehorses. 6non-racehorses). Twenty-five of 35 (71%) racehorses wereable to return to racing (16 in the same class, 9 in a lowerclass); all 6 non-racehorses were able to return to performanceat the same level. Horses with small fracture fragments orfractures involving the abaxial surface of the proximalsesamoid bone only had a more favorable outcome comparedwith horses with large apical-abaxial fractures (Southwoodet aI1998).

There were 10 (21 %) Grade 1 fractures, 23 (49%) Grade 2fractures and 14 (30%) Grade 3 fractures. All 5 horses withGrade 1 fractures returned to racing (4 in the same class and1 in a lower class). Twelve of 18 horses with Grade 2 fracturesreturned to racing (9 in the same class and 3 in a lower class).

There has also been a report of the use of electrocauteryprobes in arthroscopic removal of apical sesamoid fracturefragments in 18 Standardbred horses (Boure et al 1999). Thefracture fragments were approached through an ipsilateral(3) or contralateral (15) arthroscopic triangulation technique.Distention of the joints was achieved using a 1.5% glycinesolution and the suspensory and intersesamoidian ligamentattachments to the abaxial and axial margins of the apicalfragment were transected using a hook electrocautery probe.Subsequently. the palmar (plantar) soft tissue attachmentswere transected with a loop electrocautery probe. After beingfreed of soft tissue attachments, the apical fragment wasremoved with Ferris-Smith intervertebral disc rongeurs.Eighteen apical sesamoid fragments were removed from theleft (8) and right (8) hind limbs and the left (1) and right (1)forelimb. Apical fragments occurred in 15 lateral and 3medial proximal sesamoid bones. It was proposed that theelectrocautery probe made an easy and precise dissection ofall soft tissue attachments; 10/14 horses returned to racing(7/9 horses that raced before surgery raced again and 3/5horses that had not raced before surgery raced afterwards).Figure 5.61G illustrates the use of an ArthrexTM electro-cautery probe to remove a basal sesamoid bone fragment.

Eight horses with Grade 3 fractures returned to racing (3 inthe same class and 5 in a lower class). Four racehorses had

not raced prior to surgery; 2 of these horses raced aftersurgery. and 2 did not race before or after surgery. Comparedwith horses with large fragments. horses with smallfragments

returned to racing in the same class more often;however. the differences were not significant.

The results of arthroscopic removal of fracture fragmentsinvolving a portion of the base of the proximal sesamoid bonehave also been reported (Southwood & Mcilwraith 2000).There were 24 racehorses and 2 non-racehorses. Twelve(50%) of the racehorses returned to racing and started in atleast 2 races; 8/14 of horses with Grade I fractures (~ 25% ofthe base involved) and 4/10 with Grade n fractures (>25%.but < 100% of the base involved) had a successful outcome;10/16 without associated articular disease had successfuloutcomes compared with 2/8 with associated articulardisease. However. fragment size and presence of associatedarticular disease were not significantly associated withoutcomes (probably related to the relatively low numbers). Itwas concluded that horses with a fracture fragment involvinga portion of the base of the bone removed arthroscopicallyhave a fair prognosis for return to racing.

Axial osteitis of the proximal sesamoidbones and fraying ofintersesamoideanligaments with detachment fromproximal sesamoid bone

Cases of this have been recognized and treated arthroscopically.Arthroscopic surgery in 5 cases (out of 8 seen) has beenreported (Dabareiner et al2001). Typically. the horses presentbecause of lameness and they mayor may not have synovialeffusion (6/8 in the cases reported by Dabareiner et al2001).Two cases had diffuse cellulitis and effusion of the digitalflexor tendon synovial sheath. All horses had osteolysis of theaxial border of the proximal sesamoid bone on radiographs.In 5 horses. arthroscopy of the palmar or plantar pouch of allthe metacarpophalangeal or metatarsophalangeal joint andof the digital sheath was performed. In the remaining 3 horses.only the palmar or plantar pouch of the metacarpophalangealor metatarsophalangeal joint was examined. Damage to theintersesamoidian ligament was seen in all horses andconsisted of discoloration. fraying. and detachment from theassociated proximal sesamoid bone. Osteochondral fragmen-tation and osteomalacia involving the axial borders of theproximal sesamoid bone was also seen in all joints. Afterdebridement, the palmar or plantar pouch of the affectedjoint communicated with the distal synovial sheath throughthe disrupted ligament. Figure 5.62 illustrates the radiographicand arthroscopic manifestations of such a case.

Follow-up information was obtained for all horses. All5 horses without evidence of sepsis returned to their previoususe with the median recovery time of 9 months. However,one of these horses remained Grade 1/5 lame and radiographsobtained 1 year after surgery revealed secondary osteoarthritisof the affected metacarpophalangeal joint. Two horses wereradiographed 12 months after surgery revealing remodelingof the sesamoid bones with a smooth contour to the axialmargins of the sesamoid bone.

Instances of focal bone disease involving the sesamoidbones have been encountered elsewhere. The pathogenesis isunknown, but areas of focal subchondral bone disease occurand have been treated with debridement of defective tissue

(Fig. 5.63).

Arthroscopically assisted repair oflateral condylar fractures of the distalMclll and Mtlll

Arthroscopy allows an optimal means of assessing andIrepairing lateral condylar fractures. The use of the arthroscope

allows verification of articular alignment as well as ,compression of the fracture and a complete diagnostic examin- iation of the joint. With correct technique. even displacedfractures can be accurately reduced and repaired without a ':

large surgical exposure (Richardson 2002).

Arthroscopic Surgery of the Fetlock joints j§Z

cif!!D

evaluation of the horse to detect axial

Fig. 5.64). A complete set of radiographsdorsopalmar/dorsoplantar projections to

(CWM & IMW) perform surgery with therecumbency while one (AJN) uses lateral

!\ tourniquet is not used. After surgical pre-:lraping. needles are placed and a radiograph

,0 ascertain the ideal positioning of the screws(Fig. 5.65). The fracture is inspected arthroscopically(Fig. 5.66). An alternative technique for ascertaining theposition of the distal screw on the radiograph by bisecting animaginary line extending from the palmar/plantar wing ojthe proximal phalanx to the palmar dorsal edge of thecondyle has been described by Richardson (2002). A No. 10scalpel blade is used to make a 1 cm incision over the latera]condylar fossa for the initial glide hole. A 4.5 mm glide hole isdrilled to the fracture plane (Fig. 5.67). A 3.2 mm hole isdrilled beyond this (Fig. 5.68) and. after light countersinking,a 52 or 54 mm4.5 mm diameter cortical bone screw is placedto compress the fracture (Fig. 5.69A). Additional screwsare placed proximally as appropriate for fracture length(Fig. 5.69B & C). One author (AJN) prefers 5.5 mm diametelscrews for all condylar fracture repair. with 4.5 mm screwsoccasionally used for the most proximal screw in a lon~condylar fracture.

With displaced fractures it is important to not drill thfglide hole into the parent bone. Large AO/ ASIF reductiolJforceps are used to reduce the fracture (Fig. 5.70). Thfarthroscope is then placed in the dorsal pouch and used t(monitor the reduction of the fracture. The forceps are place,at or above the level of the physeal scar. Usually a combi.nation of varus/valgus stress. dorsal flexion and sligh!internal rotation reduces the fracture (Richardson 2002)When reduction is perfect. the fracture is clamped againIt is important to ensure reduction of the fracture using ~palmar arthroscopic examination as well. The palmar/plantaJapproach is very useful in reducing displaced fractures. Th(arthroscope can be advanced into the fracture gap to visualis(and remove fragments inhibiting reduction. After reductionscrews are placed in the same fashion as described for ~nondisplaced fracture. Figure 5.70 shows a displaced condylaJfracture before and after reduction.

A second reason for the examination of the palmar 0]plantar aspect of the joint is that varying degrees of concomitant injury to the proximal sesamoid bones can OCCUIDebridement of cartilage erosion on the sesamoid followed bJmicrofracture may be necessary. Severe damage is considerela negative prognosticator. It is not possible to obtain a goOIexamination of the distal palmar aspect of the metacarpusFragments and debris that result from distal palma]comminution of the fracture are removed following elevatioIwith a probe or small curette. Prior to reduction. ever~attempt should be made to remove comminuted fragmentfrom the fracture line in displaced fractures since this wi!reduce the possibility of ideal fracture apposition.

Horses with non-displaced fractures typically have a4-month lay-up period. Screw removal varies betweendifferent surgeons but in general. only screws that crosstubular cortices need to be removed. There have been tworecent studies on the prognosis for lateral condylar fractures(Bassage & Richardson 1998. Zekas et aI1999). Horses withnon-displaced condylar fractures have an excellent prognosisfor returning to athletic function. The prognosis for thosewith displaced fractures is poorer.

The study by Zekas et al (1999) correlated condylarfracture characteristics and type of treatment with subsequentcapacity for athletic activity, as well as determining thechacteristics of healing that affect prognosis after repair offractures of the third metacarpal/tarsal condyles; overall,65% of horses started in a race post-injury, in a mean time of9.7 months with a mean of 13.7 races post-injury. Havingraced pre-injury did not convert to an advantage to startingpost-injury, but non-starters, pre-injury tended to take longerto return to racing. In horses starting pre- and post-injury,66% improved or maintained their race class level aftersurgery, whereas 64.2% decreased their race earnings post-injury; 85% of the fractures received internal fixation, ofwhich 70% were complete fractures; 87% of horses withincomplete-nondisplaced fractures treated conservativelyraced post-injury. The percentage of horses starting in a racepost-injury for incomplete nondisplaced, complete nondis-placed, and complete displaced fractures treated withinternal fixation were 74%, 58%, and 50%, respectively. Colts(72%) raced post-injury more frequently than fillies (53%)and it was suggested that this may represent a truerprobability of starting in a race post-injury: 52% of horseswith articular fragments within the condylar fracture wereable to race post-injury.

Horses were more likely to start if radiographs at2-4 months revealed no evidence of the fracture except thepresence of lag screws. Based on this series of studies, themajority of horses with proper treatment were able to returnto racing regardless of the fracture characteristic. Prognosisappeared to be affected by the severity of the injury to thejoint, the presence of articular comminution, and the qualityof surgical repair. There were 14/16 horses (87%) treatedwithout surgery that raced after a lay-up period.

This study was particularly interesting in that 58% ofcomplete nondisplaced fractures and 60% of horses withcomplete displaced fractures were able to race post-surgery.The authors concluded that the similar number of horsesracing in these two groups may indicate that a fracture being

complete is more of a factor in prognosis than the non-displacement. if care is taken to reduce and fix the fracture

accurately.

ReferencesBarclay VP. Foerner JJ. Phillips TN. Lameness attributable to

osteochondral fragmentation of the plantar aspect of theproximal phalanx in horses: 19 cases (1981-1985). J Am VetMedAssoc 1987: 191: 855-857.

Bassage LH. Richardson DW. Longitudinal fractures of the condylesof the third metacarpal and metatarsal bones in racehorses: 224cases (1986-1995).J Am Vet Med Assoc 1998: 212: 1757-1764.,

Birkeland R. Chip fractures of the first phalanx in the metatarso-,. phalangeal joint of the horse. Acta Radiol (Suppl) 1972; 29:

; 73-77.r Boure L. Marcoux M. Laverty S. Lepage OM. Use of electrocautery

probes in arthroscopic removal of apical sesamoid fracturer. fragments in 18 Standardbred horses. Vet Surg 1999; 28:, 226-232.

Bramlage LR. Osteochondrosis -related bone cysts. Proc MEP1993; 39: 83-85.

Carlsten J. Sandgren B. Dalin G. Development of osteochondrosis inthe tarsocrural joint and osteochondral fragments in the fetlockjoints of Standard bred Trotters. 1. A radiological survey. EquineVetJ Supp11993; 16: 42-47.

Colon JL, Bramlage LR, Hance SR, Embertson RM. Qualitative andquantative documentation of the racing performance of 461Thoroughbred racehorses after arthroscopic removal of dorso-proximal first phalanx osteochondral fractures (1986-1995).Equine Vet J 2000; 32:475-481.

Dabareiner RM, Watkins JP, Carter GK, et al. Osteitis of the axialborder of the proximal sesamoid bones in horses: eight case(1993-1999). J Am Vet Med Assoc 2001; 219: 82-86.

Dabareiner RM, White NA, Sullins KE. Metacarpophalangeal jointsynovial pad fibrotic proliferation in 63 horses. Vet Surg 1996;25: 199-206.

Dalin G, Sandgren B, Carlsten J. Plantar osteochondral fragments inthe metatarsophalangeal joints in Standardbred trotters; result ofosteochondrosis or trauma? Equine Vet J 1993; 16 (Suppl):62-65.

Elce y, Richardson DW. Arthroscopic removal of dorsoproximal chipfractures of the proximal phalanx in standing horses. Vet Surg2002; 31: 195-200.

Foerner JJ. Osteochondral fragments of the palmar and plantaraspects of the fetlock joint. Proceedings of the 33rd AnnualMeeting of the American Association of Equine Practitioners,1987: 739-744.

Fortier LA, Foerner JJ, Nixon AJ. Arthroscopic removal of axialosteochondral fragments of the plantar/palmar proximal aspectof the proximal phalanx in horses: 119 cases (1988-1992). J AmVet MedAssoc 1995; 206: 71-74.

Groendahl AM. The incidence of bony fragments in osteochondrosisof the metacarpo- and metatarsophalangeal joints of Standardbred Trotters. A radiographic study. J Equine Vet Sci 1992; 12:81-85.

Haynes PF. Diseases of the metacarpophalangeal joint. Vet ClinNorth Am (Large Anim Pract) 1980; 2: 37-49.

Hogan PM, McIlwraith CW, Honnas CM, Watkins JP, Bramlage LR.Surgical treatment of subchondral cystic lesions of the thirdmetacarpal bone: results in 15 horses (1986-1994). Equine VetJ1997; 29: 477-482.

Hornof WH, O'Brien TR, Poole RR. Osteochondritis dissecans of thedistal metacarpus in the adult racing Thoroughbred horse. VetRadio11981; 22: 98-106.Jaffe

HL, Lichtenstein 1, Sutro CS. Pigmented villonodular synovitis,bursitis, and tenosynovitis. Arch Patho11941: 31: 731-765.

Kannegieter NJ. Chronic proliferative synovitis of the equinemetacarpophalangeal joint. Vet Rec 1990; 127: 8-10.

Kawcak CE, McIlwraith CWo Proximodorsal first phalanx osteo-chondral chip fragmentation in 336 horses. Equine Vet J 1994;26: 392-396.

Kawcak CE, McIlwraith CW, Norrdin RW, Park RD, Steyn PS.Clinical effects of exercise on subchondral bone of carpal andmetacarpophalangeal joints in horses. Am J Vet Res 2000; 61:1252-1258.

LoSasso MB, Honnas CM. Chronic proliferated synovitis in a horse.Equine Pract 1994; 16: 29-32.

McIlwraith CWo Subchondral cystic lesions (osteochondrosis) in thehorse. Comp Cont Educ Pract Vet 1982; 4: 2828-291S.

McIlwraith CWo Experience in diagnostic and surgical arthroscoppyin the horse. Equine Vet J 1984; 16: 11-19.

McIlwraith CWo Diagnostic and surgical arthroscopy in the horse,2nd edn. Philadelphia: Lea & Febiger; 1990a.

McIlwraith CWo Subchondral cystic lesions in the horse -theindications, methods, and results of surgery. Equine Vet Educ1990b: 2: 75-80.

McIlwraith CW Osteochondritis dissecans of the metacarpophalangealand metatarsophalangeal (fetlock) joints. Proceedings 39thAAEP Convention, 1993: 63-67.

McIlwraith CWo Arthroscopic surgery for osteochondral chipfragments and other lesions not requiring internal fixation in the

Standardbred Trotters. 1. Epidemiology. Equine Vet J Suppl199 3;16: 31-37.

Simon O. Laverty S. Boure L. Marcoux M, Scoke M. Arthroscopicexcision of osteochondral fragments of the proximoplantar aspectof the proximal phalanx using electrocautery probes in 23Standardbred horses. Vet Surg 2000: 29: 285.

Southwood 11. McIlwraith CWo Arthroscopic removal of fracturefragments involving a portion of the base of the proximalsesamoid bone in horses: 26 cases (1984-1997). J Am Vet MedAssoc 2000; 217: 236-240.

Southwood 11. McIlwraith CW. Trotter GW et al. Arthroscopicremoval of apical fractures of the proximal sesamoid bone inhorses: 98 cases (1989-1999). Proc AAEP 2000; 46: 100-101.

Southwood 11. Trotter GW. McIlwraith CWo Arthroscopic removal ofabaxial fracture fragments of the proximal sesamoid bones inhorses: 47 cases (1989-1997). J Am Vet Med Assoc 1998; 213:1016-1021.

Steyn PF. Schmidt D, Watkins J et al. The sonographic diagnosis ofchronic proliferative synovitis in the metacarpophalangeal jointof a horse. Vet Radio11989; 3: 125-138.

van Veenendaal JC. Moffatt RE. Soft tissue masses in the fetlock jointof horses. Aust Vet J 1980; 56: 533-536.

White NA. Synovial pad proliferation in the metacarpophalangealjoint. In: White NA. Moore IN (eds). Current practice of equinesurgery. Philadelphia: Lippincott; 1990: 550-558.

Whitton RC, Kannegieter J. Osteochondral fragmentation of theplantar/palmar aspect of the proximal phalanx in racing horses.AustVetJ 1994; 71: 318-321.

Yovich JA. McIlwraith CWo Arthroscopic surgery for osteochondralfractures of the proximal phalanx of the metacarpophalangealand metatarsophalangeal (fetlock) joints in horses. J Am Vet MedAssoc 1986; 188: 273-279.

Yovich Jv; McIlwraith CW. Stashak TS. Osteochondritis dissecans ofthe sagittal ridge of the third metacarpal and metatarsal bones inhorses.JAmVetMedAssoc 1985; 186: 1186-1191.

Zekas LJ, Bramlage LR. Embertson RM. et al. Results of treatment of145 fractures of the third metacarpal/metatarsal condyles in135 horses (1986-1994). Equine Vet J 1999; 31: 309-313.

carpal and fetlock joints of the equine athlete: What have welearned in 20 years? Clin Tech Equine Pract 2002; 1: 200-210.

Mcllwraith CWo Vorhees M. Management of osteochondritis dissecansof the dorsal aspect of the distal metacarpus and metatarsus.Proceedings 35th AAEP Annual Convention 1990; 547-550.

Meagher DM. Joint sugery in the horse: the selection of surgicalcases and consideration of the alternatives. Proceedings of the20th Annual Meeting of the American Association of EquinePractitioners. 1974.

Misheff MM. Stover SM. A comparison of two techniques forarthrocentesis of the equine metacarpophalangeal joint. EquineVetJ 1991; 23: 273-276.

Murphy DJ. Nixon AJ. Arthroscopic laser extirpation of metacarpo-phalangeal synovial pad proliferation in 11 horses. Equine Vet J2001; 33: 296~301.

Nickels FK. Grant BD. Lincoln SD. Villonodular synovitis of theequine metacarpophalangeal joint. J Am Vet Med Assoc 1976;168:1043-1046.

Nixon AJ. Osteochondrosis and osteochondritis dissecans of theequine fetlock. Compend Cont Educ Pract Vet 1990; 12:1463-1475.

Nixon AJ. Pool RR. Histologic appearance of axial osteochondralfragments from the proximoplantar/proximopalmar aspect of theproximal phalanx in horses. J Am Vet Med Assoc 1995; 207:1076-1080.

Palmer SE. Radiography of the abaxial surface of the proximalsesamoid bones of the horse. J Am Vet Med Assoc 1982; 181:264-266

Pettersson H. Ryden G. Avulsion fractures of the caudoproximalextremity of the first phalanx. Equine Vet 1982; 14: 333-335.

Raker CWo Orthopedic surgery: errors in surgical evaluation andmanagement. Proceedings of the 19th Annual Meeting of theAmerican Association of Equine Practitioners. 1973.

Raker CW: Calcification of the equine metacarpophalangeal jointfollowing removal of chip fractures. Arch Am Coli Vet Surg 1985;4: 66-68.

Richardson DW. Arthroscopically assisted repair of articularfractures. Cl~n Tech Equine Pract 2002; 1: 211-217.

Sandgren B. Dalin G. Carlsten J. Osteochondrosis in the tarsocruraljoint and osteochondral fragments in the fetlock joints in

.has become a most important techniquediagnosis as well as for surgery in the femoropatellar

femorotibial joints (Martin & McIlwraith 1985,.c 1984,Folandetal1992.Nickels&Sande

, Moustafa et a11987, Lewis 1987, Walmsley 2002,al 2003). Diagnostic and surgical arthroscopy

trochlear ridge of the femur. At this location. the patella canbe displaced further from the trochlear ridge. which allowsthe sleeve to slide proximally more easily.

When the sleeve is positioned to the hilt. the obturator isremoved and is replaced with the arthroscope. The light cableand ingress fluid line are attached and the joint is distended.Figure

6.3 demonstrates the position of the arthroscopic sheathat the completion of insertion and the diagrams in Figure 6.4show the position of the arthroscope at the beginning of thediagnostic examination.

Normal arthroscopic anatomy

of the arthroscope intofemoropatellar joint

If both legs are involved, each leg should remain

postoperative femoral nerve paresis or quadricepsAlternatively, the legs may be elevated and tied

that tension is not concentrated on the quadriceps

The skin portal for the arthroscope is located between themiddle and lateral patellar ligament, and halfway betweenthe tibial crest and the distal aspect of the patella (Fig. 6.1).This arthroscopic portal allows a complete diagnosticexamination of the femoropatellar joint as well as fulfilling allneeds for observation during surgical manipulations. An8-mm stab incision is made through the skin, superficial fascia,and deep fascia into the femoropatellar fat pad (Fig. 6.1B).The sleeve and conical obturator are manipulated throughthe stab incision in the skin and fascia and then angled 450 tothe skin in a proximal direction (Fig. 6.2). The femoropatellarjoint space is entered by gently manipulating the obturatorand arthroscope sleeve under the patella and over the femoraltrocWea. This maneuver may be facilitated by elevation of thedistal limb. If resistance is encountered, the sleeve andobturator are not forced but are directed more laterally to lieunder the lateral part of the patella facet and over the lateral

The suprapatellar pouch is the first area of the joint visiblewhen the arthroscopic sleeve is situated beneath the patellaand rests in the intertrochlear groove (see Fig. 6.4). This areais large. but the synovial membrane lining the pouch can bevisualized on all surfaces of the pouch. The proximal extent ofthe suprapatellar pouch may be poorly illuminated with lowoutput light sources.

The articular surface of the patella and intertrochleargroove can be visualized by withdrawing the arthroscopefrom this position (Fig. 6.5). Specific examination of each areacan be achieved by rotating the arthroscope. The suprapatellarpouch disappears from view as the arthroscope is withdrawnand eventually the tension of the patellar ligaments abruptlyforces the arthroscope out from beneath the patella. At thisstage. the distal apex of the patella is visualized resting in theintertrochlear groove (Fig. 6.6). A fringe of villous synoviumusually overhangs the distal margin of the patella.Longitudinal defects are often observed in the central part ofthe intertrochlear groove and apparently are normal.particularly in the more distal regions of the groove.

The medial trochlear ridge and the medial aspect of thedistal patella can be visualized by rotating the arthroscopeand directing the angled field of view toward the medialaspect of the joint (Fig. 6.7). Despite joint distention, thepatella

and medial trochlear ridge remain in close appositionin this case, in contrast to the same area on the lateraltrochlear

ridge. The medial trochlear ridge is then examinedby moving the distal end of the arthroscope carefully along

the length of the ridge (the eyepiece of the arthroscope ismoving proximally during this maneuver) (Figs 6.8 and 6.9).This will visualize also the medial patellar fibrocartilage andconjoined medial patellar ligament. Advancing the arthro-scope over the medial trochlear ridge and viewing caudally,one can view the synovial recess beyond the medial trochlearridge. In some cases, a fold of synovial membrane overlies thedistal extremity of the medial trochlear ridge (Fig. 6.10B). Ifthis fold is elevated, a communication into the medial femoro-tibial joint may be apparent: this communication can permitthe passage of the arthroscope and visualization of the cranialaspect of the medial condyle.

The arthroscope is returned to the proximal aspect of themedial trocWear ridge and is rotated laterally and across theintertrochlear groove to the lateral trochlear ridge (Fig. 6.11).With fluid distention, the patella is separated from the lateraltrocWear ridge in this aspect of the joint. This separationfacilitates examination of the proximal aspect of the lateraltrochlear ridge as well as the undersurface of the patella, andalso allows advancement of the arthroscope proximally into

Diagnostic arthroscopy ofclinical conditions

The

primary indication for arthroscopy of the femoropatellarjoint has been in cases of osteochondritis dissecans. Surgicalintervention for this condition is discussed in a separatesection.

Arthroscopic surgery also has value in cases of distalpatellar fragmentation and patellar fractures. Diagnosticarthroscopy of the femoropatellar joint is also performed incases

of persistent femoropatellar effusion in which theradiographic changes are equivocal or absent. In some ofthese

animals, articular cartilage lesions may be seen on thearticular surface of the patella. Some appear to be cases ofOCD but in others the changes are consistent with what isdescribed

as chondromalacia in the human knee. Thepathogenesis and significance of such an entity in the horseis

still uncertain. If such changes in the articular cartilageare visualized, the pathologic area is debrided (chondro-plasty) and clinical improvement has occurred after suchtreatment in equine patients.

The use of the probe in evaluating all cartilage lesions.particularly those of osteochondritis dissecans. cannot beoveremphasized.

The portal for a probe can be made virtuallyanywhere in the femoropatellar joint as there are noadjacent tendon sheaths and bursae. The usual locationsfor instrument portals when operating on lesions atvarious

positions within the femoropatellar joint arepresented subsequently. These portals are also sites forprobe

entry. Surgeons can ascertain optimal sites for probepenetration by inserting an l8-gauge 1.S-inch needleinto

the joint to determine if the site and angle are

satisfactory.

the suprapatellar pouch without risk of damage to thearticular surfaces (as mentioned previously, this is the reasonwhy moving the arthroscope sleeve laterally facilitates initialentry of the arthroscope into the joint). The synovial mem-brane in the lateral aspect of the joint adjacent to the area ofarticulation of the lateral trochlear ridge and distal patella issmooth and non-villous (see Fig. 6.11), but if becomes quitevillous distal to this point. The entire length of the lateraltrochlear ridge is then explored by moving the distal end ofthe arthroscope distad and advancing the arthroscopefurther into the joint as necessary (Figs 6.12 and 6.13). Thismaneuver involves moving the eyepiece of the arthroscopemediad and proximad. The synovial membrane is villousadjacent to the distal one-half of the lateral trochlear ridge(Fig 6.12B) and fluid distention is often critical to allow aclear view of this area. The trochlear ridge is examined untilthe synovial reflection of the distal extremity is encountered(see Fig. 6.13). In the event of the view being obscured byhypertrophied synovial villi, viewing of a specific area of thetrochlear ridges can be improved with gradual flexion. As thearthroscope is moved axially from the lateral trochlear ridge.the distal aspect of the intertrochlear groove can beexamined. Irregular cartilagenous protuberances and creasesare commonly seen and are considered normal (Fig. 6.14).

Insertion of the arthroscope into thecranial pouch of the medialfemorotibial joint

The

horse is positioned in dorsal recumbency with the leg inflexion (approximately 900 at hock and stifle). The leg issurgically prepared and draped. Three approaches have beenused for diagnostic arthroscopy of the medial femorotibialjoint:

cranial (Moustafa et al198 7), lateral (Lewis 1987), andcraniolateral (Nickels & Sande 1982). All approaches providean effective examination of the cranial part of the medialfemorotibial joint. The authors use the first two approaches.and they are described. The cranial approach allows moreconsistent examination of the intercondylar (cruciate) area.On the other hand. the lateral approach leaves a clear areacranially for instrument placement when operating onmedial condylar lesions.

Cranial approach. The medial femorotibial joint maybe distended with sterile fluid through an 18-gauge needle

Diagnostic Arthroscopy of the Femorotibial joints

Femoropatellar and Femorotibial joints

Fig. 6.5Patella (P) and trochlear groove (T), with arthroscope underthe patella, at the level of the proximal trochlear groove. (A)Diagram of visual field (circle). (B) Arthroscopic view.

.,

Femoropatellar and Femorotibial Joints

inserted cranially, but the first author (C. W.M.) generally findsthis unnecessary. For the cranial approach, a skin incision ismade and continued through the fascia between the middleand medial patellar ligament about 2 cm proximal to the tibialcrest. The arthroscopic sleeve containing the conical obturatoris then inserted through the fat pad in a slightly proximad,caudad, and axial direction until it penetrates the medialfemorotibial joint capsule (Fig. 6.15). Entry into the joint isconfirmed by observation of the joint features or egress of fluidon removal of the conical obturator (if joint is predistended).The arthroscope is then inserted and the examination canbegin (Fig. 6.16).

Lateral approach. The site of the arthroscopic portalis caudal to the lateral patellar ligament, cranial to the longdigital extensor tendon, and 2 cm proximal to the tibial spine(Lewis 1987) (Fig. 6.17). The arthroscopic cannula withconical obturator in place is then directed medially andslightly caudad to penetrate the synovial membrane in thelateral aspect of the medial femorotibial joint (Fig. 6.18A).The obturator is removed and the arthroscope is inserted.After checking that the arthroscope is in the cranialcompartment (Fig. 6.18B), the joint is distended, and theexamination begins (Fig. 6.19).

Approach to the cranial pouch ofthe medial femorotibial Jointfrom femoropatellar joint

This technique was originally described by Boening (1995)and subsequently reported in the United States by Peroni &Stick (2002). A longer arthroscope is preferred for thistechnique. The femoropatellar joint is entered through thenormally described portal between the lateral and middlepatellar ligaments. mid-way between the patellar and tibialcrests. The slit-like openings communicating with the medial

of the axial aspect of the femorotibial joints. but examinationfurther laterally and medially is limited.

Normal arthroscopic anatomy ofthe cranial compartment of themedial femorotibial joint

The medial intercondylar eminence of the tibia and axial sideof the medial condyle of the femur can be easily located in thedistal medial aspect of the joint and used as a reference point(Fig. 6.20). The cranial ligament of the medial meniscus andcranial cruciate ligament are also observed. The cranialligament of the medial meniscus and the cranial portion ofthe medial meniscus are visible by moving the arthroscopemedially along the distal aspect of the medial condyleof the femur (Fig. 6.21).

.in some cases the lateral femorotibial joints

a window between the respective femorotibial joint

and Femorotibial joints

The tip of the arthroscope is retracted to the center of thejoint and the arthroscope is rotated upward to visualize thecentral weightbearing area of the medial condyle of thefemur (Fig. 6.22). Visualization of the medial and cranialaspects of the medial condyle of the femur may be facilitatedby some extension of the joint (Fig. 6.23). Visualization of themedial collateral ligament. however. requires a more medialarthroscopic approach. Further retraction of the arthroscopereveals the proximal axial portion of the medial condyleand the caudal cruciate ligament running proximodistalbeneath the synovial membrane (Fig. 6.24). A better viewof the cruciate ligaments can be obtained with the cranialapproach. but a complete examination can be done witheither approach.

Insertion of the arthroscope intothe cranial compartment of the

lateral femorotibial joint

Medial

approaches to this joint have been described by bothNickels & Sande (1982) and Moustafa et al (1987), and arefavored over a cranial or a lateral approach. Attempts to createa

direct lateral portal are inhibited by the lateral collateralligament and the lateral patellar ligament. and by the tendonof origin of the long digital extensor. A portal between themiddle

and lateral patellar ligaments can be used, butarthroscopic manipulation is limited.

For the medial approach to the lateral femorotibial joint asoriginally described by Moustafa et al (1987), the arthroscope(after approaching the medial femorotibial joint using thecranial approach) is returned to the intercondylar referencepoint in the medial femorotibial joint. The lateral femorotibialjoint may be pre-distended with fluid through an 18-gauge

and Femorotibial joints

needle inserted between the lateral patellar ligament and thelateral collateral ligament, but this is not necessary. Thearthroscope then views the synovial septum cranial to the inter-condylar eminence of the tibia. In this position, the arthroscopeis replaced with the conical obturator, and the sleeve is in-serted caudolaterally behind the long digital extensor tendon,to the far side of the joint. The arthroscope is then placed inthe sleeve and the arthroscopic examination commences.

Alternatively, the lateral femorotibial joint may beapproached directly without prior arthroscopic examinationof the medial femorotibial joint. The lateral femorotibial jointis distended as described previously, and an 8-10-mm skinincision is made medial to the middle patellar ligament. Thearthroscopic sheath and trocar is then advanced caudolaterallyto penetrate the joint capsule on the cranial side and advancedto the lateral side of the joint.

A

Normal arthroscopic anatomy ofthe cranial compartment of thelateral femorotibial joint

cranial cruciate ligament can be seen axially undermedian septum (Fig. 6.28). A small area of 1 -,

visible axial to these structures.

After entry, the initial view should include the lateral aspectof the lateral femoral condyle, as well as the popliteal tendonwithin its synovial diverticulum (Fig. 6.25). Withdrawal ofthe arthroscope reveals the lateral femoral condyle and thelateral meniscus (Fig. 6.26). Further medial, the cranialligament of the lateral meniscus and the lateral tibial condylemay be visualized, as well as the long digital extensor tendonunder the synovial membrane and within the sulcusmuscularis of the tibia (Fig. 6.27). With further withdrawaland rotation of the arthroscope, the lateral aspect of the

Insertion of the arthroscoJ?e into thecaudal pouch of the medialfemorotibial joint

joints are small. The stifle is positioned in 90-1200 of flexion.The joint is distended with a spinal needle placed

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Lateralcondyle

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Medial

condyle

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Medial I

approach if/! P

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i

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Poplitealtendon

2002).

The arthroscopic portal can be made in the iplane as the needle. but 3 cm caudally; In consideration

described the level of the portal as 2.5 cm proximal to ..distal level of the medial meniscus and 3 cm caudalthe medial collateral ligament. This approach providesadequate view of the axial aspect of the joint (Fig. r -

Making the portal 3 cm more proximad to allow for ainstrument portal has been described by other(Hance et al ~

prior use of the spinal needle. More caudal entry ofarthroscope, 6 cm caudal to the medial collateral ]

better examination of the caudal horn of the

Additionally, it leaves more room for instrument entry.

Normal arthroscopic anatomy of thecaudal pouch of the medialfemorotibial joint

are initially visualized (Fig. 6.30).'medial meniscus may be ';". .

of the pouch and the outline of the caudal cruciate ligamentmay sometimes (rarely) be noted axially beneath the jointcapsule. coursing in a proximodistal direction.

femoral condyle and the proximal border of the poplitealtendon. To view the pouch distal to the popliteal tendon. theportal is located at the level of the tibial plateau. 1.5 cmcaudal to the lateral collateral ligament. and the arthroscopeis placed through the popliteal tendon to allow examinationof the more caudal articulation of the joint. It was noted byTrumble et al (1994) that the tendon of the popliteal tendonbeing contiguous with the joint capsule of the caudal pouchof the lateral femorotibial joint makes arthroscopic explo-ration of this pouch particularly dillicult.

Insertion of the arthroscope into thecaudal compartment of the lateralfemorotibial joint

These approaches are based on the descriptions of Trumble et al(1994), Hance et al (1993), and Stick et al (1992). It isimportant to be aware that the peroneal nerve lies 7 cm caudalto the lateral collateral ligament and so no portal should bemade this far caudally. The popliteal tendon divides thecaudal lateral femorotibial joint. Distention is performed witha spinal needle placed caudal to the collateral ligament. Forexamination proximal to the popliteal tendon, the portal isplaced 2.5 cm proximal to the tibial plateau and 3 cm caudalto the collateral ligament (Fig. 6.29) (Walmsley 2001).Structures seen through this portal are limited to the lateral

Normal arthroscopic anatomy of thecaudal compartment of the lateralfemorotibial joint

With the proximal arthroscopic portal. it is possible to viewthe proximal border of the popliteal tendon and the lateralfemoral condyle (Fig. 6.31). Using the distal portal throughthe popliteal tendon it is possible to examine the caudal

meniscus, part of the caudal aspect of the lateral, the intra-articular portion of the popliteal

but this examination is

arthroscopy of clinicalin the femorotibial

cases of cystic lesions of the medial condyle of the.1987). Surgical intervention for this condition

medial femoral condyle, and a complete tear of the cranialcruciate ligament in 1 case.

More recently, the use of arthroscopy to both diagnose andtreat vertical tears of the cranial horn of the meniscus andthe cranial ligament of the meniscus has been described(Walmsley 1995). The most recent use of arthroscopic surgeryin 80 cases of meniscal tears in the horse has been describedby Walmsley et al (2 00 3). Schneider et al (199 7) also describedthe use of medial femorotibial arthroscopy to evaluate cartilagelesions on the medial femoral condyle as a cause of equinelameness in 11 cases. These conditions will be discussed inmore detail separately.

As noted previously, the septum separating the lateral andmedial femorotibial joint compartments is commonlydisrupted in association with cruciate ligament injury; acranial approach to the medial femorotibial joint will alsoallow examination of the lateral femorotibial joint in thesecases. If both cranial and cruciate (and medial collateral)ligaments are disrupted, the resulting laxity will allow greatervisualization of the femorotibial articulations and menisci.

1987; Turner et a11988. McIlwraith 19951995. 2002). Lewis described the arthroscopic

in 20 cases of unilateral lameness. with a positivethe medial femoro-

but without major radiographic abnormalities. A.was abnormality of the articular surface of

distal weightbearing portion of the medial femoralabnormalities included fibrillation of the articularpartial- to full-thickness erosion, sometimes

and, in some cases,cartilage flaps. Abnormalities of the medial

were evident in 9 cases, including mild to markedand degeneration of the proximal surface. A

3 cases and a partial avulsion/of the cranial ligament of the medial meniscus was

1 case. Examination of the menisci was difficult in alland Lewis (1987) noted a lack of ability to adequately

the caudal segments of the meniscus. Lewis alsothe use of surgical arthroscopy in 2 cases of tibial

fractures. One of the 2 horses was completely soundcould resume full function; the other was periodically

mild degree when heavily used. Of the 20 cases inrevealed articular cartilage

Osteochondritis dissecans

Arthroscopic surgery has emerged as the only surgical tech-nique to treat osteochondritis dissecans (OCD) in the femoro-patellar joint. It has replaced arthrotomy eliminating localproblems with wound healing and reducing the need for rigidpostoperative management. The techniques presented sub-sequently are based on the experience of the authors withclinical cases of OCD in the femoropatellar joint and thefollow-up data that have been generated from these cases(Mcllwraith 1984, Mcllwraith & Martin 1984,1985; Martin& Mcllwraith 1985. Foland et al1992). Although successfulresults can be obtained by using arthrotomy, potential com-plications include seroma formation. local cellulitis andfasciitis, and wound dehiscence (Pascoe et al 1980, 1984;Trotter et aI1983).

nonsteroidal anti-inflammatory agent therapy,

Turner et al (1988) reported the confirmation of cranial, .injury in 5 cases by the use of femorotibial

A cranial approach with the arthroscopeused. Arthroscopic examination revealed the following

disruption of the septum surrounding theligaments and separating the medial and lateral

joint compartments; increase in the joint spacewith ligamentous laxity; synovitis; and areas of

Preoperative considerationsPreoperative diagnosis of OCD is based on clinical andradiographic signs. The clinical signs that initially prompt theattention of owners are lameness and/or synovial effusion ofthe femoropatellar joint. The disease is not breed-specific, butit is a disease of young horses. In some instances. however. noclinical problems are apparent until the horse is in training orhas raced (Mcllwraith & Martin 1985). Lesions that manifestat this stage are generally less severe. Clinical examinationgenerally reveals some degree of synovial effusion as aconsistent finding. Lameness ranges from nondiscerniblethrough subtle gait changes (shortened anterior phase ofstride, low arc of flight. and unusual flight path with the stifle

included

a partial longitudinal tear of the cranialligament in 1 case (the horse also had a cranial

ligament at its insertion adjacent to the tibialtearing of the cranial attachment of the lateral

the

rotated outward and the hock inward) to obvious lamenesswith a stiff gait and difficulty in getting up. Animals may havedifficulty in trotting with a preference to canter or "bunny-hop" is common.

The radiographic manifestations of the disease vary.Lesions most commonly occur on the lateral trochlear ridgebut are also seen on the medial trochlear ridge of the femurand/or on the patella (Table 6.1). The lesions in turn may belocalized to a small area or be distributed along the entirelength of the trochlear ridge. The most common radiographicmanifestation of OCD is a defect (with or without discerniblefragments) on the lateral trochlear ridge of the femur(Fig. 6.32). Defects can be described as concave (see Fig. 6.32),flattened (Fig. 6.33), cystic, or undetermined. Lesions on themedial trochlear ridge usually manifest as a concave defect(when evident radiographically), but often are not visible onradiographs (due to a normal subchondral bone contour)(Fig. 6.34). Lesions can also be observed (less frequently) invarious parts of the patella and manifest as some form ofsubchondral defect (Fig. 6.35).

For many years the authors recommended arthroscopicsurgery for all cases of osteochondritis dissecans, particularlyif an athletic career is planned. However, the study byMcIntosh & Mcllwraith (1993) shows that, with conservative

management (stall or pen confinement for 60 days). then anumber of femoropatellar OCD cases can heal. Based on thisstudy. if defects are less than 2 cm long and less than 5 mmdeep and there is no obvious mineralization or fragmentationof the flap on radiographs. conservative therapy is a viableoption. It has also been pointed out by Dik et al (1999) thatup to age 8 months it is possible for radiographic lesions onthe femoral trochlear ridges to resolve. In a longitudinal studyof Dutch Warmblood foals, radiographed at 1 month old andsubsequently at 4-week intervals, the mid-region of the lateralfemoral trocWear ridge became radiographically abnormal from3 to 4 months old. Subsequent progression of radiographicabnormalities was usually followed by regression andresolution. with the appearance returning to normal at8 months old in most cases. At 5 months old. 20% of thestifles were abnormal radiographically, but at 11 months oldthis percentage had decreased to 3%. Normal and abnormalappearances were permanent from 8 months old (Dik 1999).

The authors currently recommend that all lesions greaterthan 2 cm in length or 5 mm in depth. or any lesion thatcontains osseous densities in the presence of synovialeffusion. be treated with arthroscopic surgery. In some of thecases that can potentially heal conservatively. owner or

trainer request for the problem to be assured of correctionalso leads to early surgical treatment. Persistence of synovialeffusion is always an indication for surgery. When theseverity of the changes is too severe, surgery is not recom-mended. A direct comparative study was done comparingradiographic and arthroscopic findings in the femoropatellarjoint (Steinheimer et al 1995). It is rare to find an arthro-scopic lesion less severe than the radiographic insinuation.On the other hand, it is common to find more pathologicchange at arthroscopic surgery than predicted by radio-

graphs.

TechniqueA number of different instrument portals are used to perform

surgery at various locations in the femoropatellar joint.

Previously, six different triangulation approaches were used

to operate on the various lesions of osteochondritis dissecans

in the femoropatellar joint and were discussed in the second

edition of this text. However, exact sites for instrument entry

do not need to be rigidly fixed. Rather, the use of an I8-gauge

disposable spinal needle is now recommended to ascertain

the ideal location for an instrument portal (Fig. 6.36). In all

To effectively operate the underside of the patella. aninstrument portal must be level with or distal to the arthro-scopic portal and usually 2 cm lateral to the arthroscopicportal (see Fig. 6.40). If this portal is more proximal than thearthroscopic portal. the end of the instrument cannot makecontact with the undersurface of the patella. The portal ismade lateral to the middle patellar ligament. depending onthe position of the lesion on the patella. To operate on lesionson the distal aspect of the lateral trochlear ridge. the samearthroscopic portal is used as that chosen for the proximaltrochlear ridge. although the arthroscope is directed distad.The instrument portal is made low over the distendedfemoropatellar joint through or immediately adjacent to thelateral patellar ligament (Fig. 6.41). For lesions on the distalaspect of the medial trochlear ridge. a distal portal is usuallymade between the middle and medial patellar ligaments(Fig. 6.42). If the lesion on the medial trochlear ridge islocated on the trocWear groove (axial) side of the distal medialtrochlear ridge. however. a medial portal does not alwaysallow the instrument to reach this location. In this instance.a lateral instrument portal. allowing the instrument to passunder the middle patellar ligament. is necessary (Fig. 6.43).

cases, a l-cm incision is made through the skin and super-ficial and deep fascia, and using a stab incision with a No. 11blade completes entry into the joint. The various instrumentsare then inserted through the portal as required (Fig. 6.37).The various surgical approaches are illustrated in Figures6.38-6.43. In all instances, we are using the same arthro-scopic portal between the lateral and middle patellar ligamentalthough it is noted that an arthroscopic portal between themiddle and medial patellar ligaments has also been used foroperations involving lateral trochlear ridge lesions (Bramlageperscomm 1987).

Lesions on the proximal one-half of the lateral trochlearridge are reached through a portal proximolateral to thearthroscopic portal (see Fig. 6.38). The instrument may passeither lateral to or (usually) through the lateral patellarligament when using this portal. If the entry is too far lateral,the instrument cannot be manipulated up and over thelateral trochlear ridge. Passing the instrument through thelateral patellar ligament does not seem to be of anyconsequence. Lesions of the proximal portion of the medialtrochlear ridge are reached by using a portal between themedial and middle patellar ligaments. entering the skin distalto the lesion (Fig. 6.39).

fragmentation within the articular cartilage and sub-

chondral bone (Figs 6.44 and 6.45). This situation is

common when ossified flaps or fragments have been observed

on preoperative radiographs. When the lesions manifest

radiographically as subchondral defects in the trochlear

ridge. chondral or osteochondral flaps are also commonly

found. Gross and histopathologic examinations frequently

confirm osseous tissue in the cartilage fragments and flaps,

even when they are not discernible on radiographs.

In either situation, the flaps are manipulated and elevated,

usually by using a periosteal elevator or rongeurs (see

Fig 6.45). The flaps are then removed by using Ferris-Smith

intervertebral disk rongeurs or an equivalent instrument (see

Fig 6.37 and Figs 6.44-6.48). The flap is removed in

successive bites with the rongeurs. leaving it attached at its

proximal edge. This technique reduces the chance of the flap

slipping from the grasp of the forceps and becoming a loose

body. In joints in which the subchondral defect does not

contain a distinct flap, the nature of the lesion varies from a

dimple to an openly eroded lesion. Fragments of cartilage

within a matrix of granulation or fibrous tissue may be noted a

within the defect. After removal of the flap or fragments,

undermined articular c?ftilage unattached to subchondral

bone is removed by using Ferris-Smith rongeurs or basket

forceps (see Figs 6.46 and 6.47).

Debridement of the remaining subchondral defect is then

performed. Hand curettage is used in most cases. A motorized

burr can be effective in debriding the defects to healthy

subchondral bone (Fig 6.50) but can easily result in excessive

loss of tissue. A hand curette is used in most cases (see

Figs 6.45-Fig. 6.47). Curettage allows better between normal and pathologic bone.

At the completion of subchondral debridement, tags---

mined, unattached articular cartilage remains.

commonly occur as raised areas of articular

trochlear ridge lesions, with the use ofportal (Figs 6.39, 6.42, 6.45, and 6.47).

and on the axial sides of the trochlear ridges. It iscommon to see OCD lesions on the ~ ~c ,-- ~

is gauged by inserting a spinal needle. but generally

ridge will not allow access to the lesion.arthroscope and instrument is depicted in Figure

Manipulations of the surgical instruments vary, but asequential protocol is generally followed. A number of casesare used to demonstrate the manipulations (Figs 6.44-6.48).In all cases, the lesions are initially evaluated with a probe.The probe is useful in defining the limits of an osteochondralor chondral flap as well as for assessing its mobility. The probeis also used to evaluate any cracking, wrinkling, or fibrillationin the articular cartilage. If the cartilage is cracked but firmlyattached to subchondral bone, it is not removed. Normal-appearing articular cartilage is also probed, particularly ifradiographs have revealed lesions in the subchondral bone inthat area. If intact cartilage overlies a subchondral defect, theprobe breaking through the articular cartilage into the defectlocates the lesions and the undermined articular cartilage isthen removed.

The most common form of pathologic change encounteredon arthroscopic examination of osteochondritis dissecans ofthe lateral trochlear ridge of the femur is flap formation or

graphs indicate severe intraarticular disease and surgerycontraindicated (Fig. 6.49)

Primary OCD lesions of the patella are uncommon, "--

they do occur (Fig. 6.51).-

.,

",' Femoropatellar and Femorotibial jointsWi

,~

for lesions on the trochlear ridges, with removal of feature of osteochondritis dissecans of the femoropatellarjoint. This lack of correlation takes a number of forms: (1)cartilaginous change more severe than expected. based onthe subchondral lesions seen on the radiographs; (2)cartilaginous lesions on the trochlear ridge or patella whereno subchondral bone changes were radiographicallydetectable; or (3) less severe cartilaginous change thanexpected (usually taking the form of intact articular cartilageover radiographically lucent subchondral change). Thevarious radiographic defects observed manifest in a numberof ways during arthroscopic examination. Usually some formof cartilaginous flap or islands of cartilage and a fibrous tissuestroma are present within a concave defect (see Figs 6.44 and6.45); other cases involve a dimple-type defect or an area ofcartilage fibrillation or loss with or without undermined ordetached articular cartilage. In some instances. intactcartilage is separated from the bone (see Figs 6.45 and 6.47).

.In addition to primary osteochondritisof the patella. degenerative erosive lesions that

of cartilage (with bone sometimes) are seen on thein association with lateral trochlear ridge OCD

6.51B). The usual site for these patellar lesions is the-it articulates

the area of osteochondritis dissecans on the lateralridge. Histological examination of these buds ofin one of the author's (A.J.N.) laboratory suggest

Lack of correlation between radiographic lesions andpathologic changes found intraoperatively are a

deep fascia. as occurs with the conventional lateral or medialinstrument portals. As in other joints, the skin alone issutured and no healing problems have been observed.

It is difficult to make specific recommendations withregard to how to manage osteochondral masses embedded inthe synovial membrane or in the fibrous joint capsule. Forcases in which the loose body is attached to synovialmembrane but is clearly visible within the joint, removal isindicated and can be performed arthroscopically withoutproblems. For a less-visible or less-accessible lesion, arthrotomycan be performed and the first author (C. W.M.) has used thistechnique in one instance of such a lesion (Mcllwraith &Martin 1985). It is questionable if removal of this mass wasnecessary and the authors favor leaving it alone when it isembedded within the joint capsule. Formation of osseousbodies in the soft tissue has occurred postoperatively, andsimilar lesions have been noted on radiographs obtained afterarthrotomy (Pascoe et aI1984). Horses with these osseousmasses can race, leading to the interpretation that theseanimals do not need surgery.

Osteochondral bodies that have detached from theprimary trochlear ridge lesions can be a challenging surgicalproblem. They may be free within the joint or embeddedwithin the synovial membrane and joint capsule. If thesebodies are totally free within the joint. the surgeon mustgrasp the fragment carefully without pushing it away andcausing it to float up into the suprapatellar pouch (Fig. 6.52).Switching off the ingress fluids at this stage can decrease thefluid flow and minimize movement of the loose body. Priorfixation of the loose body with a needle is also of help in thissituation.

In instances of large fragments. the skin incision isenlarged to facilitate removal and occasionally the deep fascialincision is also enlarged. However. a proximal instrument portalabove the patella into the suprapatellar pouch can be used toremove large fragments with satisfactory results. A spinalneedle is used to confirm the correct position before incising aportal through the quadriceps muscle into the suprapatellarpouch. Large fragments are removed more easily through thisportal because they do not have to come through the inelastic

such fragments have a rigid bony component, which is rarelypresent in the equine case. Recently, a technique for usingPDS Orthosorb@ pins has been described by Nixon et al (2004)for fixing large OCD flaps (see Chapter 16). A very selectgroup of OCD lesions are suitable for reattachment. Thecartilage of the flap must be relatively smooth, not calcified,and have at least some residual attachment to the sur-rounding cartilage. The arthroscopic PDS pin kit can then beused to secure the flap in multiple locations. Reattachment,revitalization, and most, importantly, filling of the sub-chondral bone defect occurs within 8-12 weeks of :

the rapid return of ,follow-up radiographs (Fig. 6.54). This compareswith the trochlear ridge defect remaining afterment, particularly for the discerning buyer ofyearlings. It should be stressed, however, thatOCD flaps of the femoral trochlear ridges do not fit :guidelines established for reattachment and need todebrided.

Contraindications for surgery include lateral luxation ofthe patella owing to excessive loss of the lateral trochlearridge, and secondary remodeling changes of the patellaridentified radiographically (see Fig. 6.49).

At the completion of the surgical procedures for osteo-chondritis dissecans, the joint is liberally lavaged andvacuumed to ensure removal of small debris released at thetime of surgical debridement. A special, larger egress cannulahas been developed for this purpose. It is 8 mm in diameterand is 20 cm in length. It is inserted until its tip lies within thesuprapatellar pouch (Fig. 6.53A). The suction tubing can beapplied directly to the end. A motorized fluid system is criticalin flushing this joint. Use of this special egress cannula at theend of the procedure is most appropriate, because the debriscollects in the suprapatellar pouch and an instrument oflarge diameter is necessary to allow its removal. An alter-native is to insert a large diameter cannula into the supra-patellar pouch through a portal proximal to the patella.

After completion of the procedure and suturing of theincisions, a sterile loban@ drape is placed over the surgerysite in lieu of a bandage (Fig. 6.53B).

Pin fixation of large osteochondritis dissecans fragmentshas been described in man (GuhI1984). Note, however, that

some clot organization within the defect. After this time, it istheorised that exercise will facilitate modulation of the tissuewithin the defect toward some form of fibrocartilage. On thebasis of follow-up results, the horse can return to lighttraining 3 to 4 months postoperatively, depending of the ageof the animal.

IResultsThe

results of arthroscopic surgery performed in the first40 cases of osteochondritis dissecans involving 24 horseswere reported by McIlwraith & Martin (1985). More recently,we

published the results of arthroscopic surgery for the treat-ment of OCD in 250 femoropatellar joints in 161 horses(Foland et al 1992). There were 82 Thoroughbreds, 39Quarter Horses, 16 Arabians, Warmbloods, and 15 others ofvarious breeds. There were 53 females and 108 males: 22horses were less than 1 year old at the time of surgery, 68were yearlings, 36 were 2 year olds, 21 were 3 year olds, and14 were either 4 years old or older: 91 had bilateralinvolvement and 70 had unilateral disease.

Follow-up information was obtained on 134 horses,including 79 racehorses and 55 non-racehorses. Eighty-six(64%) of these 134 horses returned to their intended use, 9(7%) were in training at the time of publication, 21 (16%)were unsuccessful, and 18 (13 %) were unsuccessful due toother defined reasons. Horses with Grade I lesions (less than2 cm in length) had a significantly higher success rate (78%)than did horses with Grade II (2-4 cm) or Grade III (greaterthan 4 cm) lesions (63% and 54% success rates respectively).A significantly higher success rate was also noted for horsesoperated on as 3 year olds compared with the remainder ofthe study population. A significantly lower success rate wasnoted for yearlings than for the remainder of the population.There was no significant difference as related to genderinvolved, racehorse vs non-racehorse, lesion location, uni-lateral vs bilateral involvement, presence or absence of patellaror trochlear groove lesions, or presence or absence of loosebodies.

Although a permanent clinical cure would likely be anti-cipated with this surgery in most cases, the nature of healingwithin the defects is less certain. On the basis of long-termfollow-up radiographs obtained in horses that are sound, itseems irregular contours in the subchondral bone frequentlypersist. After debridement, defects presumably fill with fibroustissue or fibrocartilage, but this supposition is based onminimal amounts of follow-up necropsy data (Pascoe et al1984) or second-look arthroscopy (Fig. 6.55). Whatever thetissue that fills the defect, it seems to provide satisfactorystroma for articulation. No lateral trochlear ridge lesion isnecessarily too big to negate surgery but more detailedfollow-up evaluation of larger lesions in elite athletes wouldbe appropriate. As mentioned previously, if lateral luxation ofthe patella is present, surgery is contradicted. Limitations forhealing have been described in the medial condyle of thefemur (Converyet al19 72), but our clinical data support someform of functional filling of these defects on the trochlear

ridges.

Postoperative managementHorses generally receive procaine penicillin and gentamicinsulfate perioperatively and phenylbutazone before surgeryand for 5 successive days. This regimen is a precautionagainst any development of interfacial swelling. Most casesare simple to manage. and the horse can be discharged soonafter surgery. Hand walking commences after 1 week to allow

The condition is characterized by osteochondral fragmen-tation of the distal aspect of the patella. In the initial report of15 horses, the problem was unilateral in 6 horses andbilateral in 9 and occurred in 8 Quarter Horses, 3 Thorough-breds, 2 American Saddlebreds, 1 American Paint and 1Warmblood/Thoroughbred cross. A previous medial patellardesmotomy had been performed on 12 of the 15 horses.

The condition manifests as hind limb lameness andstiffness ranging from mild to severe. There is fibrousthickening in the stifle area in all cases associated withprevious medial patellar desmotomy (the fibrosis is centeredover the desmotomy site) and synovial effusion is normallypresent and recognizable if the fibrosis is not too extensive.The radiographic changes include bony fragmentation,spurring (with or without an associated subchondral defect),subchondral roughening, and subchondral lysis of the distalaspect of the patella (Fig. 6.56).

The treatment is arthroscopic surgery. In the initial seriesthe lesions at arthroscopy varied from flaking, fissuring,undermining, or fragmentation of the articular cartilage tofragmentation and/or lysis of the bone at the distal aspect ofthe patella (Fig. 6.57). The subchondral bone was involved inall cases that had a previous medial patellar desmotomy. Ofthe 12 horses that had a previous medial patellar desmotomy,8 horses became sound for their intended use, 1 horse wassold in training without problems, 1 horse was in earlytraining without problems at the time of publication, 1 horsenever improved and 1 horse was in convalescence. Of thethree cases that did not have a medial patellar desmotomy,2 horses performed their intended use, but 1 horse was un-satisfactory. In these instances, there was no severe boneinvolvement. It is possible that such cases are equivalent tothe chondromalacia syndrome described by Adams (1974).

The healing potential of horses that have undergoneoperations at 2-3 years of age may be less than that ofyounger aniJIlals. Fortunately. these older horses typicallyhave smaller defects. complete resurfacing of which may notbe as critical for athletic function. Our published data for3 year olds supports this conclusion (Foland et alI992).

A common question from clients regarding surgery forOCD of the stifles is what is the likelihood of having morelesions develop or will the problem develop in other joints? Ofthe 161 horses operated on for femoropatellar OCD. 12 under-went concurrent surgery for other lesions as well as femoro-patellar arthroscopy (Foland et aI1992). Five of these horseshad OCD lesions in both metatarsophalangeal joints. 4 horseshad OCD of the tarsocrural joint. 2 horses had subchondralcystic lesions of the medial femoral condyle. and 1 horse hadOCD of a scapulohumeral joint. In other words. the likelihoodof lesions developing elsewhere is low. Also. the more recentwork by van Weeren & Barneveld (1999) shows that if ahorse is operated on at 11 months of age or older. thereis no likelihood of additional lesion development in the

femoropatellar joint.

Preoperative considerationsThe history in these cases usually involves the development of

hind limb lameness referable to the stifle, usually after medial

patellar desmotomy. In most instances, the specific indication

for the medial patellar desmotomy is unknown (performed by

other veterinarians). Subsequent to desmotomy, a gonitis

develops and persists. Femoropatellar effusion may be present

in addition to pericapsular fibrosis. The lameness is typically

obvious at the trot but is observable commonly at the walk.

Radiographs of the femoropatellar joint reveal either a defect

in the bone at the distal aspect of the patella or bony

fragmentation (usually associated with an observable defect)

of the distal aspect of the patella (see Fig. 6.56). On the basis

of a lack of clinical improvement as well as the presence of

radiographic lesions in these cases, arthroscopic surgery is

recommended.

Fragmentation of the distal patellaTechniqueAn arthroscopic examination of the femoropatellar joint isperformed as previously described. The lesion is identified onthe distal patella and any other changes in the joint arenoted. A distal lateral arthroscopic portal is made to allow an

This condition was mentioned in the second edition of thistextbook. It has now been further explained and reported inthe literature (McIlwraith 1990) and its pathogenesisexplained (Gibson & McIlwraith 1991).

1988).

During this period. Lewis developed an arthroscopicItechnique for use in these cases and reported 77 cases. of

which follow-up data are available in 67 (Lewis 1987). This

latter technique was then adopted by the first author andreported in the second edition of this text.

well as damage elsewhere (seen occasionally). The frag-ments are removed by using a medial or lateral portal asappropriate.

Instruments may include a banana blade,elevator, Ferris-Smith rongeurs, and motorized abrader.In occasional instances, a fracture of the medial patellarfibrocartilage

without osseous involvement may be seen(Fig. 6..e0).

A retrospective study of five performance horses withpatellar fractures treated with arthroscopic removal has beenreported

(Marble & Sullins 2000). Four of five horses hadfractures of the medial aspect of the patella and one horsehad

a fracture of the lateral aspect. Arthroscopy wasperformed in the femoropatellar joint using techniquesdescribed

previously. There were no complications with thejoint or the arthroscopic portal incisions. Recovery periodsranged

from 3 to 5 months. All horses recovered completelyfrom surgery and performed at the same or a higher level ofcompetition as before arthroscopy.

Preoperative considerationsThe

typical clinical sign is lameness in one or both hind limbsat a trot. In some horses, lameness is subtle and is noticeableonly during riding. Historically, some of these horses can bein

training for considerable periods of time, with clinical signsmanifesting only after a certain amount of work has beendone.

Most horses swing the leg medially and the lameness isaccentuated when trotting in a circle with the affected leginside.

Medial femorotibial analgesia localizes the lesion but aresponse can also be obtained with femoropatellar blockade.

Any change in the external appearance of the stifle isminimal. Mild distention of the femorotibial joint may be

seen in more chronic cases. It is more common to see femoro-patellar effusion (Howard et al1995).

The lesion is apparent radiographically. Both flexed lateraland caudocranial views (Figs 6.61 and 6.62) are useful to

ascertain the location and size of the lesion. The typical lesionis round or oval with a defect at the articular surface ofvarying

size (see Fig 6.61). Such lesions may be bilateral. Inother cases, a small flattened or concave defect (see Fig 6.62)may be present. Most commonly, the latter lesion is seen inthe

stifle opposite to one manifesting lameness and exhibitinga large cystic lesion or as an incidental finding on pre-purchaseradiographs

of yearlings. Although surgical debridement ofcystic lesions is being described here, there are a number of

Cystic

lesions of the medialcondyle of the femur

For 8 years, the first author (C.W.M.) treated subchondralcystic lesions of the femorotibial joint using a femorotibial

arthrotomy with good results (Mcilwraith 1983. White et al

evaluation period showed that healing was similar in graftedand ungrafted defects in the equine medial femoral condyle at6 months Uackson et al 2000). This suggested that surgicaldebridement alone rather than adjunctive bone grafting ofcystic lesions is the treatment of choice.

The development of subchondral cystic lesions has beenassociated with osteochondrosis and trauma. Whereas osteo-chondrosis was initially considered the exclusive pathogenesis.observations of cystic enlargement after surgery promptedfurther investigation into the pathogenesis of these lesionsand to reasons why they may potentially expand. Work in thefirst author's (C.W.M.) laboratory (Ray et a11996), showedthat it was possible to consistently produce (5/6 cases)subchondral cystic lesions by creating a 5 mm diameter, 3 mmdeep defect in the subchondral bone at the centralweightbearing portion of the medial condyle of the femur.Other work then revealed that the fibrous tissue ofsubchondral cystic lesions (removed surgically) releasednitric oxide, PGEz, and neutral metalloproteases into culturemedia after in vitro culturing. It was also shown thatconditioned media of the cultured tissue was capable ofrecruiting osteoclasts and increasing their activity (vonRechenberg et al 2000). It was therefore felt that fibroustissue could play an active role in the pathologic processes ofbone resorption occurring in the subchondral cystic lesionsand may be partially responsible for the slow healing rate andexpansion of these lesions. For this reason, the first author(C.W.M.) has in recent years injected corticosteroids at thetime of surgical debridement. Recent reports by Sandler et al(2002) suggest that simple debridement still has a highsuccess rate. On the other hand, reports of arthroscopicintralesional injection of corticosteroids (Vandekeybus et al1999) have prompted evaluation of this technique and thiswill also be described.

other options that have been used. Historically, cancellousbone grafting has been used (Kold & Hickman 1984), butresults with this technique through arthrotomy at least werenot as good as simple debridement (White et aI1988). Morerecently, some controlled work with cancellous bone graftingin experimentally created 12.7 mm diameter and 19-mmdeep defects in the medial femoral condyle and a 6-month

TechniqueThe authors have previously used a cranial arthroscopic portalbetween the middle and lateral ligaments with a cranialinstrument portal medial to the arthroscopic portal initially.The technique developed by Lewis (1987) is superior,however, and is now routinely used by the author. This lattertechnique is described here (Figs 6.63 and 6.64).

The procedure is performed with the horse under generalanesthesia in dorsal recumbency. The leg is flexed such thatthe stifle and hock are approximately at 900 angles. Stabilizingthe leg in this position is recommended. The medialfemorotibial joint can be distended with irrigating solution,but for experienced surgeons, this is generally not necessaryand the arthroscope is inserted through the lateral portalbetween the lateral patellar ligament and the origin of thelong digital extensor tendon as previously described. Examin-ation of the medial femorotibial joint is also performed aspreviously described.

The characteristic dimple in the articular cartilage over-lying the subchondral cystic lesion is visualized (Fig. 6.65)and the location for the instrument portal is determined byplacement of a needle (see Fig. 6.64A). The instrument portal

~I'

Femoropatellar and Femorotibial Joints

made using an 8 mm incision through the skin andand a stab through the joint capsule with a No. 11

.This portal must be positioned so thatsite of the lesion perpendicular

the articular surface to enable effective surgical mani-

are removed by using a curette and rongeurs (seeIn some instances a motorized burr is used to assist

The configurations of the cystic lesions at arthroscopyand can be multi-loculated. Typically debridement of

subchondral tissue continues to normal bone. Because

hole is conservatively cut back to gain sufficient access to thecystic lesion, but not more than that. More recently, one ofthe authors (AJN) has been using cancellous bone graft in thebase of the cystic lesion and adding fibrin with cells on top(see Chapter 16). Although drilling of the cystic lesion hasbeen abandoned because it appeared to be associated withenlargement of cysts (Howard et al1995), micro fracture hasbeen perfomed in the walls of the cystic lesions and it is asubjective impression that it is quite useful.

Following debridement, the joint is lavaged liberally andsuction is also applied after this procedure. The skin portalsare closed with simple interrupted sutures. Care is takenduring initial debridement of the contents of the cyst toremove defective tissue immediately from the joint and tobe a difficult decision. Cartilage that is overhanging the

minimize debris accumulation elsewhere. Debris is releasedinto the joint. but it generally accumulates in the inter-condylar area lateral to the medial condyle. A special effort ismade during lavage and suctioning of the joint to remove alldebris from this area.

in 11 horses had an osteochondritis dissecans lesion

from the opening of the subchondral cystic lesion. ~debridement performed by arthroscopy was the onlyment for 37 lesions in 23 horses.drilling of the defect bed was performed in 23 lesions18 horses. Complete follow-up information39 horses: 22 (56%) horses had a successful result17 (44%) horses had an unsuccessful result.

Postoperative managementPerioperatively, the horse receives procaine penicillin andphenylbutazone. The patient is confined to a stall for2 months. Hand walking commences at the time of sutureremoval. A minimum of 4 more months pasture rest isrecommended before training resumes. Training shouldresume only if the horse is sound at a trot after this time. Inthe series of cases reported by Lewis. the postoperativeconvalescence in cases that were ultimately successful variedfrom 4 to 18 months and averaged approximately 7t months(Lewis 1987).

results because of factors not directly attributed tosubchondral cystic lesion of the medial femoral(censored analysis), 23 of 31 '

result and 8 of 31 (26%) horses had,Within this group of horses, the prognosis for a

sex, size of ]lesion was drilled, the presence ofwith the subchondral cystic lesion, or whether theenlarged after surgery. ComparedArabians, Quarter Horses had a poorer]Follow-up radiographs were available for 14 horses.these 14 horses, the subchondral cystic lesion --

significantly with drilling of the lesion bed at the time

surgery.Lesions were classified on radiographic appearance

either Type I lesions (10 mm or less in depth.

surface ofII lesions (more than 10 mm in depth andconical or spherical) (see Fig. 6.61B), or Type ill(flattened or irregular contours of the subchondral jthe distal aspect of the medial femoral condyle. 1regression showed a significant association betweentypes as assessed from preoperative radiographs and ~types based on surgical assessment. However, '

in six joints; of the SCL that appeared to be Type I

were later determined to be Type I on the basis ofscopic findings. Of the 15 joints that appeared to ~three had a Type I SCL. six:four appeared to be norma

ResultsIn the series reported by Lewis, complete soundness forintended use was achieved in 34 of the 67 cases based onfollow-up information from the owners. In addition, 14 horseswere sound enough that they were used as intended, despiteoccasional mild lameness in the affected limb. Of the remaining19 horses, various degrees of residual lameness presented aproblem for athletic use as intended; however, some animalswere used for less stressful activities and were satisfactory inthat respect. In summary, the overall satisfactory outcome forintended use was 72% (48 of the 67 cases). Of the 19 failuresfor intended use, 11 were from a group of 28 potential race-horses, producing a 39% failure rate. Eight were from a groupof 39 horses intended for other use (cutting, reining, roping,and pleasure), representing a 21 % failure rate in these typesof horses. Lewis concluded that several factors could affectthe prognosis, including age (younger horses in general had abetter prognosis), unilateral versus bilateral lesions (cases ofbilateral involvement were somewhat less successful), signifi-cant training or use before surgery (generally decreased theprognosis), previous administration of intra-articular medi-cation (subjectively, the author thought prior corticosteroidinjection was detrimental to the ultimate outcome), radio-graphic appearance (the broader opening of the cyst at thearticular surface was associated with a less favorable prog-nosis), pre-existing degenerative joint disease (poorer prog-nosis), and intended use (racehorses were the most difficult toreturn to intended use).

Howard et al (1995) described the results of arthroscopicsurgery for subchondral cystic lesions in the medial femoralcondyle in 41 horses. There were 17 Quarter Horses, 15Arabians, 8 Thoroughbreds, and 1 Holsteiner with 28 (68%)of the horses being 1-3 years old. For all horses, the owner'scomplaint was mild to moderate hind limb lameness, or analtered gait. Bilateral radiographic abnormalities of the medialfemoral condyle were detected in 27 horses. Nineteen of the27 horses had lesions identified bilaterally at arthroscopicsurgery. In addition to the subchondral cystic lesion, 13 joints

attached to the subchondral bone on palpationand no surgical treatment was done; however.stifle of these horses did have a surgical lesion.not performed on two of the joints with a SD. Given

lesional injection of 40 mg of MPA (Depo-Medrol@) toregime. The latter technique ' -

supported by more recent work demonstrating thatfibrous tissue of

cause

achieving

lesion was

amount ofmeasured

(Howard et alsurface disrupted by

at the 1into two groups: those with lesions that involvedor less cartilage surface and those with greater

15 mm of disruption. During the period between 1989150 clinically lame Thoroughbred horses with a

214 subchondral cystic lesions had surgery. Of the86 (58%) horses had unilateral lesions and 64

(55) of the horses raced as 4 year olds. The number of startsand average earnings per start for the horses that had beenoperated on were less than their maternal siblings for their2- and 3-year-old racing careers, but were similar to theirsiblings for the 4-year-old racing year. Of the 49 horses withType I lesions, 34 (69.3%) horses started a race in their career,whereas 62 (61.3%) horses with Type II lesions started. Thisindicated that radiographically assessed lesion depth was oflittle consequence in defining the prognosis.

Additionally, there were 91 (60.6%) horses with less thanor equal to 15 mm of surface debridement and 59 (39.3%)horses with greater than 15 mm of surface debridement. Ofthe 91 horses with 15 mm or less of surface disrupted, over70% started at least one race, whereas only about 30% of the59 horses with greater than 15 mm of cartilage surfaceinvolvement started a race. The amount of cartilage surfaceaffected seemed to be a better predictor of success than lesion

depth.Most recently, one author (C. W.M.) has treated a number

of cases with intralesional injection of corticosteroid(triamcinolone acetonide) under arthroscopic visualization(Fig. 6.66). In 2-year-old Thoroughbreds, everyone at thisstage has been able to go back into training at 2 months, withalready some increased density in their cystic lesions. The

were raced, whereas 77% of the siblingswhereas 71% of males raced;

61 % (79) of the horses raced as 3 year oIds, and 51%

results are very preliminary. The technique's rationale isbased on the findings of von Rechenberg et al (2000). It ispossible that this technique offers an ability to return theathlete to racing more quickly than arthroscopic debride-ment does.

Articular cartilage lesions on medialcondyle of femur

These cases will be detected during diagnostic arthroscopy ofthe stifle. A typical signalment will be lameness with possiblesynovial effusion, positive response to hind limb flexion testsand response to intra-articular local anesthesia of the stifle(Schneider et al199 7). Lameness will be localized to the stifleby analgesia and the diagnosis confirmed with arthroscopicexamination. Diagnostic arthroscopy of the medial femoro-tibial joint is performed as previously described. Of 12 jointsin 11 horses that were affected with this condition anddescribed by Schneider et al (1997), all horses had focal areasof damage to articular cartilage on the weightbearing surfaceof the medial femoral condyle. Cartilage was dimpled,wrinkled, and folded and was not firmly attached to thesubchondral bone (Fig. 6.67). Palpation of damaged cartilagewith a blunt arthroscope probe consistently revealed an areaof loose cartilage through which the probe could be easilyinserted into the subchondral bone. Fibrillation and exposureof subchondral bone were also evident in some horses. Thelocation of the lesions was at the same site as for horses withmedial femoral condylar cysts. Areas of separated cartilageshould be debrided. In some instances of extensive damage,what can be done surgically is limited as extensive debride-ment will not produce a successful result.

In the report of Schneider et al (1997), follow-up inform-ation was available for all horses. Six of seven horses thatwere treated for focal cartilage lesions recovered completelyand resumed activities (successful racehorse, horse used inthree-day eventing, jumper, dressage horse, trail riding horse,and pleasure horse). One racehorse that had intermittentlameness in the affected limb did not resume activities. Only1 of the 4 horses with generalized damage to articular cartilagebecame clinically normal (show horse that was retired andused for pleasure riding). Two of the other 3 horses wereStandardbred racehorses and the remaining case was aQuarter Horse used for ranch work. These horses were unableto resume their previous activities as a result of persistentlameness. It is therefore concluded that horses with general-ized cartilage damage have a poor prognosis for becomingclinically normal and performing well after treatment.

Subchondral cystic lesions of theproximal extremity of thetibia in horses

old, with a range of 6-24 months old (Textor et al 2001).~Horses will present with severity of lameness from 0 to 3 and

in all cases the lameness can be exacerbated by stifle flexion.!Stifle joint effusion (with pouch undefined) was present in

This condition is relatively uncommon. When it occurs, it istypically present at a young age. In one report of 12 cases, themean age of these horses at presentation was 12.3 months

6 of the 12 horses previously described. In 6 horses, intra-articular anesthesia improved the lameness in 4 horses andthis was unchanged in 2 horses (these had extensive deeplesions of the lateral tibial condyle). In 6 horses the lesionswere considered to be the result of osteochondrosis and weresolitary lesions involving the lateral tibial condyle withoutother signs of joint disease (Fig. 6.68). In 5 out of 6 horses inwhich the lesions were considered to be the result of osteo-arthritis (OA) , there was a well-defined cystic lesion of themedial condyle of the tibia and signs of mild to marked OA,including remodeling the proximal extremity of the tibia,

osteophyte formation on the medial aspect of the tibia andfemur, and subchondral bone sclerosis.

A technique for arthroscopic surgery has been reported(Textor et al 2001) and cases arthroscopically approachedhad lesions located in the cranial third of the tibial plateau. Inhorses with lesions involving the lateral tibial condyle, thelateral aspect of the femorotibial joint was arthroscoped usinga medial portal, as described previously, with the arthroscopeinserted between the middle and medial patellar ligaments.Lesions would typically be identified cranial and immediatelylateral to the lateral tuberosity of the intercondylar eminence

(see Fig. 6.68). The cranial ligament of the lateral meniscususually obscured the stoma and the ligament was retractedcranially or bluntly divided with the probe to expose thestoma. Lesions were curetted to healthy bone.

If the lesion was located in the proximomedial aspect ofthe tibia (medial to the intercondylar eminence), the medialfemorotibial joint was approached through a lateral portaland, again, lesions would be identified by probing through thefibers of the cranial ligament of the medial meniscus in amanner similar to that described for lesions lateral to theintercondylar eminence. In the paper of Textor et al (2001),arthroscopic debridement was performed in 4 horses inwhich the lesions were considered to be the result ofosteochondrosis and in 3 horses with osteoarthritis. Threehorses in which SCL were considered to be the result ofosteochondrosis performed athletically after debridement.Two horses with moderate OA returned to work afterarthroscopic debridement, but at a lower level of athleticperformance. One horse with SCL related to osteochondrosisresponded to medical treatment and went on to race.

Fracture of the medial tibialintercondylar eminence

Although these fractures have been associated with avulsionof the insertion of the cranial. cruciate ligament (Prades et al1989. Mueller et aI1994).tt is the first authors experience, aswell as that of Walmsley (2002), that this is not usually thecase. It is quite common to have these fractures with minimaldamage to the cranial cruciate ligament (Fig. 6.69-6.71).even when they are quite large. The injury can of coUrse beaccompanied by damage to other structures. There is obviouslameness and signs localizing the problem to the femorotibialjoint. The fracture can be diagnosed on radiographs. In casesof isolated fracture, the usual treatment is removal of thefractured portion through a cranial instrument portal in themedial femorotibial joint (Mueller et al 1994). One authorhas pointed out that if the fracture causes significantdisruption to the surrounding tissues. lag screw fixation ispreferred (Walmsley 1997). In the case described, fixationwas performed using a cranial arthroscopic portal with anextra instrument portal in line with the angle of the implant.The prognosis in these cases is related to absence or presenceof other injury in the joint. The authors have treated casesboth by internal fixation and with arthroscopic removal.

if the examiner has considerable experience (Cauvin et al1996). However, arthroscopy is the preferred choice for adefinitive diagnosis.

Diagnostic arthroscopy of the cranial pouch of the medialfemorotibial joint can be done through a lateral or cranialportal. The cranial portal will give better overall visualizationof the cruciate ligaments in the intercondylar notch, but bothapproaches can be used. A typical partial-thickness tear willinvolve the body of the cranial cruciate ligament, rather thanthe insertion. This is consistent with experimental work thathas shown cranial cruciate ligaments fail in mid-body (Rich &Glisson 1994), at least in the pony. However, avulsion at boththe tibial and femoral insertions of the cranial cruciateligament has been reported (Edwards & Nixon 1996, Pradeset al 1989). Caudal cruciate ligament injury has beendescribed in the literature (Moustafa et al1987), but is un-common. Caudal cruciate injuries observed arthroscopicallygenerally appear as longitudinal shredding of the femoralorigin, although radiographic lesions associated with thetibial insertion of the caudal cruciate can occasionally beseen. Cranial cruciate injury can vary from hemorrhage onthe synovial membrane covering the cruciate ligamentsor mild fiber disruption to more severe fiber disruption

Injuries to the cruciate ligaments

Cruciate ligament injury in the horse was initially describedby Sanders-Shamis et al (1988) and Prades et al (1989).Complete rupture of the cranial cruciate ligament in thehorse is catastrophic and it is unusual to examine these casesarthroscopically (Fig. 6.72). Less severe injuries to cruciateligaments can be regularly diagnosed with diagnosticarthroscopy. It has been pointed out that sometimes strainsand partial ruptures may be diagnosed ultrasonographically

.Grade III, a severe tear of the meniscus and ligamentthat extends beneath the femoral condyle so that thelimits of the tear cannot be seen.

It is less common to see tears of the meniscus in the caudalpouch of either the medial or lateral femorotibial joint,although this probably reflects the reduced frequency thatsurgeons successfully enter and examine the caudal pouches.

For meniscal tears in the cranial portion of the meniscus(medial femorotibial joint), the arthroscope is usually placedthrough the lateral portal, as visualization is satisfactory andit is out of the way of the instrument. Meniscal injuriesseen in the horse can be categorized as vertical radial(transverse) vertical longitudinal, vertical flap or buckethandle, or as horizontal transverse (Fig. 6.74). True buckethandle tears, as seen in man are rare in the horse. A cranialinstrument portal is made and the torn portion removed. Thiscan be accomplished with a combination of Ferris-Smithrongeurs, biopsy suction forceps, or motorized equipment(Figs 6.75-6.77). The aim is to leave a clean edge of healthymeniscus. One of the authors (A.J.N.) has used intraarticularsuturing of the meniscus in four horses. The meniscal tearshould be clean, vertical, and relatively fresh. Suturing can beachieved by using flexible needles (Fig. 6.78) (Nitinol,Arthrex Corporation, Florida) to tie mattress sutures throughthe tear, and more complex tears can be sutured with aBankart shoulder repair device (Fig. 6.79) (Arthrex Corpo-ration, Florida) used in an upside-down configuration. Trans-verse vertical tears can be more difficult to trim or suture,since they orientated across the structure of the meniscus(Fig. 6.80). Additionally, they occur more commonly in thecentral (medial) to caudomedial portion of the meniscus andcan be difficult to even visualize.

Similarly, tears of the lateral meniscus will be encounteredon exploration of the lateral femorotibial joint using theportal that starts in the medial femorotibial joint. Access canbe a little more difficult with the arthroscopic portal in thisjoint as the long digital tendon and popliteal tendon are bothpresent intra-articularly. Avulsion fracture of the insertion ofthe cranial ligament of the lateral meniscus can causemeniscal instability (see Fig. 6.81). This site is predisposed,and in one author's opinion (A.J.N.), occurs as frequently astears in the lateral meniscal body.

In the initial report of Walmsley (1995), there were5 horses with a vertical tear in the cranial horn and cranialligament of the medial meniscus and 2 horses with similarinjuries in the lateral meniscus. All the lesions had similarcharacteristics and the tear was about 1 cm from the junctionof the axial border of the meniscus and the cranial ligamentof the meniscus ligament. In all but one case it was in-complete, with much of the torn tissue loosely attached to theaxial part of the meniscus from where it was removed. Theremaining meniscus abaxial to the tear was displacedcranially and abaxial and its torn edges were debrided. Inthose cases, 3 horses returned to full competition, 1 horsewas useable for hacking, 2 were convalescing and 1 was lameafter 1 year. Walmsley (1995) pointed out that these lesionswere quite different from the vertical meniscal tears, whichoccurred in the cranial horn of the meniscus at least 1 cm

abaxial to the junction of the meniscus and its cranialligament and involved separation of meniscal tissue on eitherside of the tear. The author was also uncertain as to whetherfraying was symptomatic or associated with age and use. Thispaper served as the hallmark for making meniscal injuries arecognizable syndrome.

A later retrospective study described 80 cases ofmeniscal tears in horses (Walmsley et al 2003). Inclusioncriteria were:

1. Lameness localized to the femorotibial joint with clinicalconfidence (in most cases that involved intra-articular

diagnostic analgesia).2. Diagnostic arthroscopy identifying an abnormality in one

or both of the femorotibial menisci.3. The meniscal injury was considered to be the primary

lesion in the joint.

The medial meniscus was involved in 60 cases and the lateralin 20 cases. Forty-three tears were Grade I. 20 were Graden, and 17 were Grade Ill. Distention of either or boththe femoropatellar and femorotibial joint was recorded in31 horses, but in 14 of these, distention was recorded in onlythe femoropatellar joint. The relative likelihood of jointdistention was nine times greater among horses with Grade nand III injuries (17/20,13/17), respectively, as compared tohorses with Grade I injuries (4/43). The median lamenessGrade was 3 (on a scale of 5); the response to intra-articularanalgesia was positive in 59/65 horses in which it wasperformed and, in 45/76 horses in which the informationwas recorded, the flexion test worsened the lameness. Radio-graphic abnormalities were seen in 38 horses and increasedwith severity of lesions. New bone formation on the medialintercondylar eminence of the tibia occurred in 23 casesand OA of the femorotibial joint was evident in 18 cases.Mineralization of soft tissue structures was seen insix cases.

Walmsley et al (2003) used the Outerbridge (1961)human grading system for articular cartilage lesions. Lesionsin the articular cartilage of the medial femoral condyle (MFC)or lateral femoral condyle (LFC) were recorded as:

.circumscribed areas of prominent fibrillation lessthan 1.5 cm in diameter, (similar to those graded asOuterbridge Grade 2)

.generalized fibrillation extending over larger areas,associated with a parent thinning of the articularcartilage (similar to Outerbridge Grade 3)

.superficial, mild fibrillation (similar to mild Outer-bridge Grade 3)

.full-thickness lesions of variable size in which thesubchondral bone could be palpated with a probe(similar to Outerbridge Grade 4)

.shear lesions or chondral flaps characterized by thepresence of torn flaps of articular cartilage

.thickened, softened, enfolded, or fissured articularcartilage (similar to Outerbridge Grade 1, but moresevere and with fissuring)

.small (about 3 mm), raised plaques of firm cartilagetissues sometimes containing shiny, yellowish tissue.

Left Tibia

A

Horizontal transverse

Vertical radial (transverse)Bucket handle

B Vertical Flap Vertical longitudinal

Fig. 6.74(A) Schematic diagram of the menisci and associated ligaments. (8) Types of meniscal tears: horizontal; vertical radial; vertical

..

abnormalities of the femoral orrecorded in 61 horses. These

and 12 of 17 Grade ill tears. Full-thicknessgeneralized fibrillation of the articular

3 and 4) lesions were recordedhorses and these had a median age of 10 years old3-22). Concurrent cranial cruciate ligament injury

in 12 cases. Twenty-five other horses showed

Overall, 47% of affected horses returned to full use. TheGrade was 63% for Grade I tears, 56%

concurrent cruciate injury were followed up and

Of the horses with radiographic

more were lame

follow-up as compared to those that did not have a

75% vs 10/34

.In the series of cases by Walmsley et al (2003),

I lesions were not debrided, but consideration was

to suturing. It was not considered practical in most

but one Grade III lesion was sutured using the

of the laparoscopic extracorporeal knotting

technique (Sopera & Hunter 1992) with No.3 polYglactin910 (Vicryl).

Meniscal tears, particularly the longitudinal tearsdescribed by Walmsley et al (2003) as Grade ill, can progressinto the mid-portion and even the caudal horn of themeniscus. Any meniscal tear where the abaxial (medial) andcaudal termination cannot be discerned needs to be exploredfurther by examination through the caudal joint pouch ofthe femorotibial joint. Discrete tears of the caudal horn of the

~

Other indications for arthroscopicsurgery in caudal pouches

the caudal aspect of the femoral condyles in foalsexamination of the caudal pouches has been(Hance et al 1993). We have also used this approach

The caudal compartment of the medial femoralis quite voluminous and free fragments can be

the instrument portal is vital in reaching theand avoiding instruments and the arthroscopewith each other as they penetrate deeper tofree pieces.

The caudal portion of the caudal r

medial meniscus can also occur (Fig. 6.82). The authors nowalways examine the caudal portion of the medial femorotibialjoint. even if a tear in the cranial horn appears contained.The medial meniscus is predominately affected; the lateralmeniscus caudal horn has been involved only once in ourexperience. Vertical longitudinal tears of the medial meniscushave also been seen (Fig. 6.83). Mineralization of the meniscusis a late-stage development (Fig. 6.84) and frequently signalschronic meniscal tearing. Surgical aims in mineralized casesshould be to trim all protruding portions that impact on thecaudal surface of the femoral condyle. debride free orfibrillated soft portions of the meniscus and suture anylongitudinal tears that are not disintegrated. Manipulation ofinstruments in the caudal compartment is tedious. particu-larly since the depth of the damaged meniscus from the skinsurface is often 6-8 cm. Trimming of caudal horn meniscaltissue is best accomplished with a motorized resector,particularly the large-format tooth synovial resectors such asthe orbit incisor or Synovator. Removal of mineralizationgenerally requires an arthroburr.

In common with other species, macerated tears of themenisci carry a poor prognosis for return to working sound-ness as the loss of fibrocartilagenous meniscal tissue isusually marked. These injuries frequently also extend into thecentral inaccessible regions of the meniscus so that removalof torn tissue often is incomplete.

medial femorotibial joint (Fig. 6.85). However,ence of authors, disruption of the insertion of(evident radiographically) may not be visiblearthroscopy. Moreover, the popliteal artery is ~this ligament and exposure of the caudal cruciatemotorized resection of the covering joint capsule wouldhazardous. A caudal cruciate ligament avulsion in ;'has been defined with imaging (Rose et aI2001).

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Schneider RK. Jenson P. Moore RM. Evaluation of cartilagelesions on the medial femoral condyle as a cause of lameness inhorses: 11 cases (1988-1994). J Am Vet Med Assoc 1997; 20:1649-1652.

Soper NJ. Hunter JG. Suturing and knot tying in laparoscopy. SurgClin N Am 1992; 72: 1139-1152.

Steinheimer DN. Mcilwraith CWo Park RD. Steyn PF. Comparison ofradiographic subchondral bone changes with arthroscopicfindings in the equine femoropatellar and femorotibial joints.A retrospective study of 72 horses. Vet Radiol 1995; 36:478-484.

Stick JA. Borg LA. Nickels. Peloso JG. Perau DL. Arthroscopicremoval of an osteochondral fragment from the caudal pouch ofthe lateral femoral tibial joint in a colt. J Am VetMed Assoc 1992;200: 1695-1697.

Textor JA. Nixon AJ. Lumsden J. Ducharme NG. Subchondral cysticlesions of the proximal extremity in horses: 12 cases(1983-2000). J Am Vet Med Assoc 2001; 218: 408-413.

Trotter CW Mcilwraith CWo Norrdin RW A comparison of two surgicalapproaches to the equine femoropatellar joint for the treatment ofosteochondritis dissecans. Vet Surg 1983; 12: 30--40.

Trumble TN. Stick JA. Arnoczky SP. Rosenstein D. Consideration ofanatomic and radiographic features of the caudal pouches of thefemorotibial joints of horses for the purpose of arthroscopy. Am JVet Res 1994; 55: 1682-1689.

et al. Lesions of the caudalaspect of the femoral condyles in foals: 20 cases (1980-1990). JAm Vet Med Assoc 1993; 202: 637-646.

Arthroscopic surgery forsubchondral cystic lesions of the medial femoral condyle inhorses: 41 cases (1988-1991). J Am Vet Med Assoc 1995; 206:842-850.

WA, Stick JA, Arnoczky Sp, Nickels FA. The effect ofcompacted cancellous bone grafting on the healing of sub-chondral bone defects on the medial femoral condyle in horses.Vet Surg 2000; 29: 8-16.

J. Results of treatment of subchondral bone cystsin the medial condyle of the equine femur with an autogenouscancellous bone graft. Equine Vet J 1984; 16: 414,

c --A retrospective study of diagnostic and surgical

arthroscopy of the equine femorotibial joint. Proceedings of the23rd Annual Meeting of the American Association of EquinePractitioners, 1987.

CWo Surgery of the hock. stifle and shoulder. Vet ClinNorth Am 1983; 5: 333-362.

Experience in diagnostic and surgical arthroscopyin the horse. Equine Vet J 1984; 16: 11-19.-.Treatment of osteochondritis dissecans and

subchondral cystic lesions. Proceedings of Panel on Develop-mental Orthopedic Disease. American Quarter Horse Association,Dallas, TX, April 1986; 21-22.

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Mcllwraith CW Osteochondritis dissecans of the femoropatellarjoint. Proceedings 39th Annual Meeting AAEP, 1993: 73-77.

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Wyburn RS. Degenerative joint disease in the horse. NZ Vet J 1977;25: 321-322, 335.

.

~

tarsocrural (tibiotarsal) joint has proven highlyboth diagnostic and surgical arthroscopy. The

The tarsocrural joints are shaved on both sides of the joint.The draping system includes an adhesive barrier andimpermeable drapes (Fig. 7.1). The joint is distended beforemaking the skin incisions. The skin incisions for thearthroscopic and instrument approaches are located to thesides of the group of extensor tendons on the dorsal aspect ofthe joint (the long digital extensor, the peroneus tertius, andthe cranialis tibialis tendons). These structures are col-lectively referred to in the remainder of the text as theextensor tendons. As a general principle, all portals are madeclose to (approximately 1 cm from) the extensor tendons tomaximum visualization.

the other joints, new discoveries have causedin the indications for diagnostic arthroscopy as

as an increase in the spectrum of surgical conditionstarsocrural joint. For instance, before the use of

surgical intervention was not considereda tarsocrural joint manifesting effusion and/

unless it had a radiographic lesion. Now wethat not all cases of tarsocrural OCD, for instance,

radiographically. Although this finding furtherthe limitations of radiographs, it does, however,to define and treat cases of "idiopathic synovitis"

undefined. In addition,other joints, OCD can be treated conveniently with

and the same advantages exist.

Arthroscopic examination using adorsomedlal approach

The dorsomedial approach is used most commonly. If thearthroscopic portal is made close to the cranialis tibialis andperoneus tertius tendons. a large portion of the dorsal aspectof the joint can be seen. The approach provides excellentvisualization of the cranial or dorsal compartment of thetarsocrural joint. including the trochlear ridges and trochlear

diagnostic arthroscopy in the tarsocruraldorsal and plantar. The dorsal approach

a dorsomedial (craniomedial) arthroscopic portal.

approach involves a plantarolateral or plantaro

arthroscopic portal. Most arthroscopic cases involve, ,. In the previous

were described. However. with the exception ofthe lateral malleolus of the tibia. a dorsolateral

.An appropriately placed

areas where surgery is done. Therefore diagnosticin this text are now limited to those seen with a

..approach.In all situations, the patient is in dorsal recumbency. This

which is important for triangulation. but also theflexion of the joint is easily controlled. The leg may

or hangs free. With relevance to arthroscopicalso minimizes the risk

Examination commences on the lateral

and its articulation with the tibia. This viewlateral malleolus (Fig. 7.3). c

visualize the central lateral trochlear ridge (Fig.further distad, the distal part of the lateralcomes into the visual field (Fig. 7.5). In this

of the arthroscope. The view of the arthroscope

and the arthroscope is withdrawnoriented in a plantar direction to

of the trochlear groove of the talus (Fig. '

of the trochlear groove is visible further distallyaddition. the talocentral (proximal intertarsal) jvisualized (see Fig.usually patent in very young foals. A

the talus (Fig. 7. 7E).Further withdrawal of the arthroscope

rotation, so that the view is proximal andvisualization of the proximalridge and its articulation with the distal tibia (Fig.

the medial malleolus is possible (Fig. 7.9). Theaspects of the medial trochlear ridge can be -

groove of the talus. Flexing and extending the joint, whichbrings different areas of the trochlear ridges into view, canincrease the area of visualization. The corresponding area ofthe distal tibia from the medial malleolus to the distal inter-mediate ridge is also visible. Many adult horses also have anopening that allows visualization of the proximal intertarsal(talocentral) joint distally. Inspection of the synovial lining ofthe dorsal aspect of the tarsocrural joint can also be performed.

The joint is distended using a needle placed through thedorsomedial pouch with the leg in extension (see Fig. 7.1).The skin portal is made slightly dorsal to the center of thedistended dorsomedial outpouching and just below thepalpable distal end of the medial malleolus. and the arthro-scopic sleeve and conical obturator are inserted (Fig 7.2).This position is ideal for visualization within the joint. If thearthroscope is placed more medially, it is difficult to pass thearthroscopic sheath over the trochlear ridges of the talusacross the joint. The skin portal is made sufficiently large(8-10 mm) to ensure that the saphenous vein is not directlybeneath the incision and to avoid its penetration. In manyhorses, the arthroscope portal can be made between thesaphenous vein and the extensor tendons, and this locationprovides optimal visualization of the deeper region of theintermediate ridge. A No. 11 blade is then used to continuethe portal through the fibrous capsule. The sleeve and conicalobturator are then inserted until contact with the medial sideof the talus is made (Fig. 7.2). The joint is then flexed,enabling the arthroscopic sleeve and obturator to pass acrossthe joint, over the top of the trochlear ridges. and beneaththe extensor tendons (this maneuver is impossible in anextended joint).

The arthroscopic portal can also be made with the jointflexed, eliminating the need to flex the joint during placementof the sheath; however. the landmarks (as well as location ofthe saphenous vein) are more easily identified with the limbin extension.

allows examination of the medial side ofdorsomedial pouch (Fig. 7.12).

With this approach. imposition of soft tissue sometimesmakes examination of the lateral trochlear ridge and other

(Tibiotarsal) Joint

areas of the lateral part of the joint challenging. It requiresthe end of the arthroscope to be close to the lateral trochlearridge of the talus along with the use of the instrument toretract soft tissue. However, with practice, this becomesreasonably easy.

Arthroscopic examination using plantarlateral or plantar medial approaches

These approaches are used far less commonly. They allowexcellent visualization of the remaining (proximal) portionsof the lateral and medial trochlear ridges that are notvisualized by using the previously described dorsal approaches.Each trochlear ridge is best evaluated by using an arthroscopicapproach through the same side (Fig. 7.13). The principalbenefit of using the plantar approaches is allowing examin-ation of defects in the proximal portion of the trochlearridges. the removal of loose bodies in the plantar pouch, andthe treatment of sepsis and osteomyelitis. This approachsometimes also is useful to access fractures of the lateralmalleolus of the tibia. Virtually all of the synovial lining ofthe plantar joint pouch can be inspected through use of these

approaches. Additionally, the planfar aspect of the distal tibiaand the deep digital flexor tendon (DDFT) within its tendonsheath can be seen, but these observations have not proven tobe of major clinical relevance. Since the second edition, theapproach to the plantar pouch has been reported in therefereed literature (Zamos et al 1994). Joint distention iscritical for the plantar lateral approach, and is done byplacing a needle in the center of the plantar pouch whichusually allows adequate distention. The skin portal is made inthe center of the plantar outpouching with the tarsus flexedat 90°. The arthroscopic sheath is placed in the joint usingthe blunt obturator. The surgeon should be careful to avoiddamaging the trochlear ridges of the talus. Viewingcommences with the hock flexed (Fig. 7.13).

Introduction of the arthroscope through a plantaromedialor plantarolateral portal located in the center of the plantarpouch puts the arthroscope immediately dorsal to the tarsalsynovial sheath surrounding the DDFT and plantar to thetrochlear ridges of the talus. This permits evaluation of theplantar aspects of the medial and lateral trochlear ridges ofthe talus as well as the trochlear groove, the distal tibia(plantar aspect of intermediate ridge) and the articularportion of the tendon sheath containing the DDFT (see

7.13). Through a plantarolateral arthroscopic portal. thec -

and the lateral malleolus can also be observed if., ., , Withdrawing the arthro-

~

spavin) is noted in the young horse, even when the radio-graphic signs are negative. In addition, arthroscopy is anexcellent means by which to evaluate the joint in a case ofsevere synovitis, suspectedThe general aspects ofdiscussed in Chapter 3. Septicyoung horse can be evaluated and

If a plantaromedial arthroscopic portal is used, directingarthroscope dorsally allows observation of the dorso-

malleolus cannot be seen.

Chapter 14. Arthroscopy also permits identification of softtissue lesions such as tears of the collateral ligaments. withinor communicating with the tarsocrural joint. As in otherjoints.

arthroscopy is superior to radiographic examination orsynovial fluid analysis for diagnosis in the tarsocrural joint.

By extending the joint more (approximately 120°), the, and lateral dorsal cul-de-sacs of the joint can be

enhanced examination of the proximal areas of the

arthroscopy of the

jointArthroscopic surgery has proven to be an excellent tool in thetarsocrural joint and is indicated for the following conditions;

1. Osteochondritis dissecans of the distal intermediate ridge

The most common indication for arthroscopy in the tarso-crural joint is for the surgical treatment of OCD. In someinstances. however. OCD is .and

2.

dissecans of the lateral and medialexamination. For this

3.

4. Osteochondritis dissecans of the medial malleolus ofthe tibia.

5. Removal of lateral malleolar fragments.6. Debridement of septic lesions of the trochlear ridges of

the talus.7. Removal of fibrin in septic arthritis.8. Treatment of some forms of proliferative synovitis.9. Traumatic lesions and osteoarthritis. including diagnostic

arthroscopy in cases of lameness and hemarthrosis.10. Intra-articular fractures of the tarsocrural joint.11. Retrieval of fragments from the talocentral (proximal

intertarsaljoint).12. Tears/avulsions of the collateral ligaments.13.

Tears/avulsion of the joint capsule.

Osteochondritis dissecans ofthe tarsocrural joint

In our experience, OCD of the dorsal aspect of the distalintermediate ridge of the tibia is the most common indicationfor arthroscopic surgery in the equine tarsocrural (tibiotarsal)joint. A review of a series of cases of OCD of 318 tarsocruraljoints treated by arthroscopic surgery (McIlwraith et al19 91)provides an indication of the location of these lesions

(Table 7.1).Lesions were seen most frequently on the intermediate

ridge of the distal tibia, followed by the lateral trochlear ridgeof the talus, and the medial malleolus, respectively. Lesionswere also seen at multiple sites in 22 joints. Loose bodies werepresent in 8 joints; 5 of them had separated from inter-mediate ridge lesions and 3 fragments had separated fromlateral trochlear ridge lesions.

These lesions occurred in 203 horses (Table 7.2).Horses with OCD of the intermediate ridge of the tibia

usually have joint effusion and/or lameness. Commonly, theclinical situation is joint effusion in the young horse ofyearling age; lameness is often not evident. Careful examina-

tion, however, often reveals a gait abnormality, which mayrelate solely to decreased flexion in the tarsus owing toincreased synovial fluid pressure.

In the 1991 retrospective study of 303 joints in whichsynovial effusion was recorded, it was the presenting clinicalsign in 261 (86.1%). In racehorses, effusion was present in166 joints (81 %) and absent in 39 joints. In non-racehorses,effusion was present in 95 joints (96.9%) and absent in3 joints. The degree of lameness was not recorded con-sistently, but usually was designated as mild. The exceptionwas when a severe lesion was present on the lateral trochlear

Number of Joints

2443712

318

Location

Intermediate ridge of the distal tibiaLateral trochlear ridge of the talusMedial malleolus of the tibiaIntermediate ridge of the tibia plus the

lateral trochlear ridge (both)Intermediate ridge plus medial malleolusof the tibia (both)Intermediate ridge plus medial trochlear

ridge of talusLateral trochlear ridge of the talus and the

medial malleolus of the tibia (both)Medial trochlear ridge of the talusLateral and medial trochlear ridges of thetalus (both)

Total

From Mcllwraith et a11991.

.,

Tarsocrural (Tibiotarsal) joint

Once the fragment is elevated. an appropriately sized pair ofgrasping forceps is introduced and the fragment is grasped(Fig. 7.17). The grasping forceps are then rotated to breakdown any remaining soft tissue attachments and withdrawn.As discussed in Chapter 4. the forceps should enclose thefragment. In many instances in the tarsocrural joint. how-ever. due to the large size of fragments this is not alwayspossible. as in the case illustrated in Fig. 7.18. As the fragmentis pulled through the joint capsule. fluid flow is again stoppedto minimize the development of subcutaneous fluid extra-vasation. As in other joints. larger fragments may necessitateenlargement of the skin incision. Otherwise. the surgeonruns the risk of losing the fragment subcutaneously.

The defect from which the fragment was removed is thenevaluated (Figs 7.16 and 7.17) and any additional fragmentsare removed. Light curettage elevates any tags of tissuewithin the defect or at the edge of the defect. which areremoved with forceps or rongeurs. The surgeon must payparticular attention to the most plantar portion of the defect,where fragments may remain but cannot be visualized.Reduced flexion and careful probing of the defect along theedge facing the trochlear groove can reveal additionalfragments and these need to be loosened and removed. Thejoint then is lavaged copiously. Postoperative radiographs are

As with all other OCD lesions, thearthroscopic manifestations in c -~ .

.""

but an osteochondritis dissecans flap was found.

that in the case illustrated in Fig. ; crural joint had an effusion but no

~

pouch of the tarsocrural joint, or descend

the loose fragments and debridement of the primary]are needed.

bandage -(and Elasticon@ -J

operation. Maintenance of J

are removed is particularly important since these incisionsare prone to dehiscence and later sepsis.

The patients can be discharged from the clinic on the firstpostoperative day. Therefore the protocol depends on theseverity of the case. Animals should be hand walked for4 weeks and then allowed small paddock or controlled lightexercise for an additional 4 weeks. Some clinicians considerthe use of sodium hyaluronate or polysulfated glycosamino-glycan (Adequan@) useful 30 days postoperatively. Trainingcan resume in 8-12 weeks unless some other clinical problemarises. Because of the early return to exercise. trainers aremore willing to stop training and remedy the problem while itis fresh. The same advantages as discussed with regard tocarpal and fetlock fragments apply to operations involvingthe tarsocrural joint.

Treatment of osteochondritis dissecansof the trochlear ridges

The technique for arthroscopic surgery of lesions on thelateral trochlear ridge of the talus is illustrated in Figure7.21. Typical cases of OCD of the lateral trochlear ridge areillustrated in Figures 7.22-7.24. Defects on the trochlear Iridge may have an OCD flap in situ (Fig. 7.22), an osteo- Ichondral fragment at the distal aspect of the lateral trochlear i

ridge (Fig. 7.23), or both a primary lesion and a loose bodyremote from the lesion that is totally free or embedded in thesynovial membrane (Fig. 7.24). The presenting clinical signsassociated with OCD of the lateral trochlear ridge of the talus

may be the same as with lesions on the intermediate ridge ofthe tibia or they may be more severe. The severity of theclinical signs is usually related to the amount of lateraltrochlear ridge that is affected.

For cases of OCD or fragmentation of the trochlear ridges,a triangulation approach using a medial arthroscope andlateral instrument portals is used (see Fig. 7.21). As discussedin the section concerning diagnostic arthroscopy, when adorsomedial arthroscopic approach is made, the medialtrochlear ridge on the near side is visualized easily, but thelateral trochlear ridge may be difficult to visualize because ofthe closer apposition of the extensor tendon bundle and associ-ated joint capsule on this side. In all instances, use of a needleto ascertain the optimal site for the instrument portal is recom-mended. It should be recognized that the technique for lateraltrochlear ridge debridement is more difficult than that usedfor intermediate ridge lesions. In the report on arthroscopicsurgery for the treatment of OCD in 318 tarsocrural joints(Mcllwraith et alI991), one of the two surgeons was still doingarthrotomy for lateral trochlear ridge lesions. Therefore, inthat published report, the relative percentage of lateral troch-lear lesions is smaller than a large population would providebecause only the first author's (C. WM.) lateral trochlear ridgecases were included. Although arthroscopic surgery for lateraltrochlear ridge lesions is more challenging than for distalintermediate ridge problems, all lateral trochlear ridge lesionscan be effectively managed using arthroscopic techniques.

The principles of fragment removal are the same asdescribed for osteochondritis dissecans of the intermediateridge. Debridement to healthy subchondral bone is importantin the more involved trocWear ridge lesions. Any osteochondralflap or fragment on the trochlear ridge is elevated andremoved and the lesion is debrided (Fig. 7.24). Loose bodiesa-e removed. Fragments embedded in the synovial membrane[13rC

,-¥ ,-"ilJUV"'U JJ .'-'-".1 ...'" VJ"JU1"'.

OCD lesions on the medial trochlear ridge of the talus arerare, but do occur occasionally. When they occur, they aretypically on the trochlear ridge immediately distal to the tibiawhen the leg is straight (Fig. 7.25). There were 3 cases in theinitial series published by McIlwraith et a11991. All casespresented as typical undermining of the cartilage in thissame position on the medial trochlear ridge (Fig. 7.25). Thearthroscopic approach is illustrated in Figure 7.26.

Bone spurs and fragments (so-called dewdrop lesions) havebeen identified distal to the medial trochlear ridge of thetalus. These spurs and fragments are typically extraarticularand are generally considered normal radiographic variationsthat are of no clinical significance (Shelley & Dyson 1986)(Fig. 7.27). Surgical intervention generally is not indicated.Most articular lesions (depressions) on the medial trochlearridge of the talus are incidental findings at arthroscopy (see

Osteochondritis dissecans of themedial malleolus of the tibia

nIrQ Irgical.mentation of the Imon location and th

dial malleolus is tht:Iinical. radiographic.

distal to the level of the arthroscopic portal. The fragment isthen elevated away using an elevator or osteotome, dependingon the degree of attachment remaining before fragmentationis removed and the defect debrided (Figs 7.30 and 7.31).

ML

Results of arthroscopic surgeryfor treatment of osteochondritisdissecans of the tarsocrural joint

findings are consistent with OCD. The axial intra-portion of the medial malleolus is affected. Such

must be distinguished from fractures of the medialthat typically involve the entire malleolus, ex-

manifestations of OCD in the medial malleolus

.in our experience. the more common situation is the

, effusion and/or lameness when animals are

broken or beginning with race training or racing.

The results of arthroscopic surgery for the treatment of OCDin 318 tarsocrural joints in 225 horses have been reported(Mcilwraith et al 1991). Arthroscopic surgery was aneffective technique for treating OCD of the tarsocrural joint.The overall functional ability and cosmetic appearance of thelimbs were excellent. Post-surgical follow-up information wasobtained for 183 horses, of which 140 (76.5%) horses racedsuccessfully or performed their intended use followingsurgery. Of the remaining 43 horses, only 11 horses were stillconsidered to have a tarsocrural joint problem. Nineteenhorses developed other problems precluding successful per-formance, 8 horses were considered poor racehorses withoutany lameness problems, 3 horses were euthanized because ofseptic arthritis (all associated with the horse getting thebandage off within 24 hours of surgery), and 2 horses diedfrom other causes. There was no significant effect of age, sex,or limb involvement on the outcome. The success rate relativeto three size groups for intermediate ridge lesions was 27/33(81.8%) for lesions 1-9 mm in width, 86/116 (74.1%) forlesions 10-19 mm in width, and 41/47 (87.2%) for lesions20 mm or more in width (no significant difference).

When success rate was considered relative to the findingsof additional lesions at arthroscopy, 16/19 (84.1%) witharticular cartilage fibrillation, 5/10 (50%) with articularcartilage erosion or wear lines (see Fig. 7.32),3/5 (60%) withloose fragments (Fig. 7.33), 0/2 with proliferative synovitisand 0/1 with joint capsule mineralization were successful.There was a significantly poorer outcome in racehorses witharticular cartilage degeneration or erosion (p < 0.05).

The synovial effusion resolved in 117/131 racehorsejoints (89.3%) and in 64/86 non-racehorse joints (74.4%).The outcome for synovial fluid effusion was significantlyinferior for lesions of the lateral trochlear ridge of the talusand medial malleolus of the tibia compared to distal inter-mediate ridge lesions. There was no significant relationshipbetween resolution of effusion and successful performanceoutcome.

More recently, the results of 64 Thoroughbreds and 45Standardbred horses treated for OCD of the tarsocrural jointwith arthroscopic surgery prior to 2 years of age were reportedand were compared to those of other foals from the dams ofthe surgically treated horses (Beard et al 1994). For theStandardbreds, 22% of those who had surgery raced as2 year olds and 43% raced as 3 year olds, compared with 42%and 50% of the siblings that raced as 2 year olds and 3 yearolds respectively. For the Thoroughbreds, 43% of those thathad surgery raced as 2 year olds and 78% raced as 3 year oldscompared with 48% and 72% of the siblings that raced as

usually confirm the presence of a lesion (Fig. 7.28),

A dorsomedial arthroscopic portal is used (Fig. 7.29). The, is extended. A needle is then used to decide on the

position for the instrument portal. but because ofpositioning of the fragment it needs to be also in the

pouch and is axial to the arthroscopic portal7.29). The instrument portal is axial and usually slightly

2 year olds and 3 year olds, respectively. The median numberof starts for surgically treated horses was lower than themedian number of starts for siblings for all groups except 3-year-old Thoroughbreds. Median earnings were lower foraffected horses than for siblings for both breeds and both agegroups. There was a tendency for horses with multiple lesionsto be less likely to start a race than horses with only a singlelesion; however, the difference was significant only for 2-year-old Standardbreds. Mfected Standardbreds and Thorough-breds were less likely to race as 2 year olds than were theirsiblings. It is noted that this study was quite different from thefirst follow-up study (McIlwraith et al 1991); the selectioncriteria and control groups were different and racingperformance was not analyzed by year in previous studies. Inanother study, horses treated for OCD of the dorsal inter-mediate ridge of the tibia performed as well as matchedcontrols (Laws et aI1993).

Subchondral cystic lesion of proximaltrochlear groove of talus uptake of technetium on a bone scan and diagnostic

arthroscopy detected a hole and cystic lesion in the trochleargroove (using a plantar approach). A medial plantararthroscope approach and a lateral plantar instrument entry

These

lesions are uncommon, but have been seen (Fig, 7.34).The case illustrated in Figure 7.34 showed an increased

allow debridement of trochlear groove cystic lesions. Somelesions can be quite deep, despite minor radiographic abnor-malities (Fig. 7.34). Flexion of the joint after insertion of thearthroscope is used to expose the cyst entry. Needle insertionthen guides the instrument portal.

Fractures of the lateral malleolus

These fragments are encountered less commonly than OCDfragments and appear to be traumatic in origin. The importantpoint to note with fragments of the lateral malleolus is that arelatively small portion of the lateral malleolus is actuallyintra-articular; most of it is enclosed within the collateralligaments. A case example is provided in Figure 7.35. Both adorsolateral arthroscope and instrument portals are usedand the arthroscope portal is axial to the instrument portal.This permits dissection of the fragmentation from the lateralcollateral ligaments and then removal and subsequentdebridement of the parent bone and ligamentous attachments.

If fragmentation runs the full dorsoplantar width of thelateral mallelous. the arthroscope can usually be pushedthrough the traumatic defect. from the dorsal to the plantarcompartments of the joint. Sometimes there will be frag-mentation that will hinge on the short collateral ligamentsinto the plantar pouch or indeed become loose bodies in theplantar pouch and these can be retrieved with the arthroscopepassing from dorsal to plantar and an instrument portalcreated laterally in the plantar pouch. Such procedures aredifficult. because most of the fragments are embedded withinsoft tissue. and inexperienced arthrocopists may use radio-graphic localization with needles and/or external dissectiondown to the fragment.

displaced fracture fragments may also occur off the medialtrochlear ridge (Fig. 7.39).

Occasionally, fractures amenable to lag screw fixation willoccur in the talus; these are usually in a sagittal plane(Fig. 7.40). Small linear fractures have been repaired withone screw, but the cases illustrated in Figure 7.40 requiredthree cortical screws.

Retrieval of fragments from thetalocentral (proximalintertarsal) Joint

Fragments will occasionally be seen in the dorsal talocentraljoint. They are often under a plica or a fibrous membrane. Thedorsomedial arthroscopic portal is the same for all othersurgery and allows visualization into the talocentral joint(Fig. 7 AI). A needle is used to decide on optimal placement ofthe instrument portal. In some cases, a medial instrumentportal will be satisfactory, while in most we have used alateral instrument portal to retrieve the fragment from underthe joint capsule or plica. Exchange of arthroscope andinstrument portals may be useful and in several cases, a thirdincision, medial and distal, in the dorsomedial joint pouchhas been required. Resection of the perimeter of the openingbetween the tarsocrural and talocentral joints is oftennecessary to identify and retrieve loose fragments from thedorsomedial recess of the joint (Fig. 7 AI).

Other intra-articular fractures of thetarsocrural joint

These fractures are relatively uncommon. Figure 7.36-7.39show some examples of cases that may be encountered.Fractures can occur through the medial malleolus of the tibiaand will show different manifestations than medial malleolusOCD. There will be an obvious linear fracture line and usuallythe fragment is displaced distally (Fig. 7.36). The fragmentsare removed arthroscopically and prognosis will be related towhether the long medial collateral ligament can be left intact.Fragments may occur off the proximal plantar aspect of themedial trocWear ridge (Figs 7.37 and 7.38) and are operatedon using an approach through the plantar pouch. Larger

.,

Tarsocrural (Tibiotarsal) joint

Tears and avulsions of the collateralligaments of the tarsocrural joint

Tears of the collateral ligaments are most common laterally.The majority involve the short collateral ligaments only. A

will have long collateral ligament involvement. and lessthe short medial ligament. All

present with lameness. tarsocrural distention. and Treatment of proliferative synovitis

Occasionally, severe proliferative synovitis occurs in thetarsocrural joint, and debridement of some of the tissue(partial synovectomy) can offer some relief" The authors haveused both hand instrumentation or motorized instru-mentation (the latter is usually better) for debridement inthese cases.

phase and later there may be an irregular abaxialto the malleolus. Ultrasound usually detects dis-(Fig. 7.42). Arthroscopically, the torn ligamentous

into the dorsal compartment and iswith a motorized resector (Fig. 7.43).

Treatment of septic arthritis and septiosteomyelitis

Reference:

The use of arthroscopy in the treatment of septic osteomyelitlesions of the talus was mentioned previously. ArthroscoIhas also been used to remove fibrin from patients witseptic arthritis and is considered to emulate the successflresults achieved with arthrotomy (Bertone et aI1987). Tl.management of sepsis in synovial structures is discussed iChapter 14.

Aftercarl

Careful maintenance of a bandage postoperatively is critic;(Fig. 7.44). As discussed with regard to osteochondritdissecans in the intermediate ridge, routine aftercare involv(1 month of stall rest with hand walking and then son:limited exercise before training commences at 2-4 monthdepending on the amount of disease. In cases of oste(arthritis or septic arthritis, the period of convalescence m8vary. In cases of proliferative synovitis, anti-inflammatoItherapy is often indicated. Intra-articular corticosteroiadministration also has been used.

Beard WL, Bramlage LR, Schneider RK. Embertson RM. Post-operativracing performance in Standardbreds and Thoroughbreds wit.osteochondrosis of the tarsocrural joint: 109 cases (1984-1990JAmVetMedAssoc 1994: 204: 1655-1659.

Bertone AL. McIlwraith CWo Jones RL. et al. Comparison of varioutreatments for experimentally induced equine infectious arthritiiAmJ Vet Res 1987: 48: 519-529.

Dik KJ. Emerink E. van Weeran PRo Radiographic development (osteochondral abnormalitis in the hock and stifle of DutcWarmblood foals from age 1 to 11 months. Equine Vet J 199~Suppll. 31: 9-15.

Hoppe F. Radiological investigations of osteochondrosis dissecans iStandardbred Trotters and Swedish Warmblood horses. EquinVetJ 1984: 16: 425-429.

Laws EG. Richardson DW. Ross MW. et al. Racing performance iStandardbreds following conservative and surgical treatment fctarsocrural osteochondrosis. Equine Vet J 1993: 25: 199-202.

McIlwraith CWo Surgery of the hock, stifle and shoulder. Vet CliNorth Am Large Anim Pract 1983: 5: 333-362.

McIlwraith CWo Foerner JJ, Davis DM. Osteochondritis dissecans cthe tarsocrural joint: Results of treatment with arthroscopisurgery. Equine Vet J 1991: 23: 155-162.

McIlwraith CWo Foerner JJ. Diagnostic and surgical arthroscopy 4the tarsocrural joint. In: McIlwraith CW (ed). Diagnostic ansurgical arthroscopy in the horse. 2nd edn. Philadelphia; Lea anFebiger, 1990: 161-193.

Shelley J. Dyson S. Interpreting radiographs. 5. Radiology of tl:equine hock. Equine VetJ 1984; 16: 488-495.

Zamos DT. Honnas CM, Hoffman AG. Arthroscopic approach anintra-articular anatomy of the plantar pouch of the equirtarsocruraljoint. Vet Surg 1994; 23: 161-166.

.

surface of the scapula. Collateral and stabilizing support forthe shoulder is derived from periarticular tendons andligaments. Lateral support is provided by the supraspinatusand infraspinatus tendons of insertion, while medial supportis formed by the subscapularis tendon of insertion and aplical fold, referred to as the medial glenohumeral ligament.The primary cranial stabilizer is the biceps tendon of origin.Similarly, caudal support is derived from the tendons of originof the teres minor and deltoideus muscles. Access for thearthroscope and instrument entry is limited to the lateralaspects by the close association of the scapula with thethorax. Finally, the accessible portions of the shoulder arefunctionally divided into cranial and caudal regions by theinfraspinatus tendon of insertion.

surgery of the shoulder is not a commonin horses and two of the authors' (C.W.M. and

experience over 20 years includes only 114 cases,all but eight of those cases involving osteochondrosis.techniques for performing arthroscopic surgery of the

have been described: a craniolateral approach.

shoulder joint immediately caudal to the infraspinatus(Nixon 1987. Bertone & McIlwraith 1987b). Inthe use of arthroscopic surgery for treating osteo-

and the results achieved in 11 horses (13have been published (Bertone & McIlwraith

1987a). (Note: in this discussion osteochondrosis is a collectiveterm for osteochondritis dissecans (OCD) and subchondralcystic lesions, as both commonly occur together.)

Conservative (non-surgical) treatment of osteochondrosisof the shoulder has met with minimal success, particularly Inthe limited numbers of horses able to enter athletic activities(Meagher et al 1975, Nyack et al 1981, Rose et al 1986).Rapid onset of osteoarthritis and a general delay in definitivediagnosis often limit the response to surgery. Early surgicalreports describe several animals that responded well to treat-ment by arthrotomy (Schmidt et a11975, Mason & Maclean1977, DeBowes et al 1982, Nixon et al 1984); however,extensive soft tissue dissection is necessary and the cranio-medial aspect of the joint may not be visualized (Nixon et al1984). Other complications include loss of lateral joint stability(Schmidt et al 1975) and seroma formation (Nixon et al1984). These complications are not only avoided witharthroscopy but also the minimally invasive nature ofarthroscopy provides many of the intraoperative and post-operative advantage~ seen in other joints. On the other hand,arthroscopy of the shoulder is more technically complex. andin adult horses it can be a particular challenge.

Insertion of the arthroscope

Surgical Anatomy ofthe Shoulder

The horse is positioned in lateral recumbency. with theaffected limb uppermost and unsupported in a slightlyadducted position. The leg is draped so that traction can beapplied to the limb during surgery. After aseptic preparationand draping of a wide sterile field. the appropriate landmarkfor insertion of a spinal needle immediately cranial to the infra-spinatus tendon and proximal to the notch dividing the greatertubercle of the humerus into cranial and caudal componentsis identified (Fig. 8.1). An 18-gauge. 3-inch spinal needle isinserted at this location at an angle approximately 250 caudaland distal to penetrate the shoulder joint cranial cul-de-sac(Fig. 8.2). The needle is advanced until the tip contactsarticular cartilage. and about 60 ml of a balanced electrolytesolution are then injected to distend the joint (Fig. 8.3).

The spinal needle is removed. and when the craniolateralapproach to the shoulder is selected. a 5-mm vertical skinincision is made in the same location (if it is not made beforeplacement of the spinal needle). For the lateral approach. theskin incision for the arthroscope portal is made 1 cm caudalto the palpable caudal border of the infraspinatus tendon.

The shoulder is a relatively tightly articulated diarthrodialjoint. and consists of the rounded articular surface of thehumeral head and the depressed concavity of the glenoid

The arthroscope cannula and conical obturator are theninserted through the joint capsule in the same direction asthe I8-gauge spinal needle under the infraspinatus tendontoward the caudal aspect of the joint (Fig. 8.4). Entry intothe joint is confirmed by removing the obturator andobserving a flow of fluid from the cannula. The arthroscopeis then placed within the cannula. and the diagnosticarthroscopic evaluation can commence from this position(Fig. 8.5).

Normal arthroscopic anatomy

Systematic examination of the joint begins with the tip of thearthroscope in the caudal aspect of the joint. In this position,the caudal humeral head (ventrally), glenoid (medially), andsynovial membrane (laterally) can be visualized (Fig. 8.6).The arthroscope and cannula are then withdrawn along thelateral aspect of the joint to allow visualization of the lateralrim of the glenoid medially, the humeral head ventrally, andthe synovial surface of the infraspinatus tendon laterally. Thesynovial membrane adjacent to the infraspinatus tendon isarranged in longitudinal bands and is relatively devoid of villi(Fig. 8.7). At this stage, elevation of the limb to a position

to the floor (as opposed to the adducted position)

the joint capsule on the humeral head. and the lateral8.8). Returning

the humeral head. The tip of the arthroscope is

, the synovial membrane underlying the bicepstendon, and the cranial aspect of the humerus (Fig. 8.9).With the joint maximally distended so the glenoid and humeralhead are separated, the tip of the arthroscope is inserted overthe humeral head and under the glenoid toward the medialside of the joint. The articular surface of the glenoid and/orcaudomedial humeral head can be closely examined by rotatingthe viewing angle of the scope 180°. Traction on the limb atthis stage also facilitates the procedure. The medial aspect ofthe glenoid and humeral head are inspected as well as themedial surface of the synovial membrane, which contains anormal plica, devoid of villi, which has been referred to as themedial glenohumeral ligament, despite the fact it is not truly

a ligament (Fig. 8.10). In mature horses, complete examinationof the medial and caudomedial aspects of the shoulder jointbecome more difficult. Additional traction can aid exposure,but access can be limited unless erosion and malformation ofthe humeral head are extensive.

Lateral arthroscopic approach

An alternative approach for arthroscopic examination of theshoulder joint uses a direct lateral approach (Nixon 1987). Inthis approach, the arthroscope penetrates the joint 1-2 cm

caudal to the infraspinatus tendon, entering between the infra-spinatus and teres minor muscles (Fig. 8.11). This approachallows examination of the cranial, lateral, and caudal portionsof the humeral head and the glenoid cavity, and portions ofthe medial aspect depending on the age of the horse and extentof disease. In most situations it also allows good visualizationof the caudomedial aspect of the humeral head (Fig. 8.12),which can be difficult to examine using the craniolateralapproach. Additionally, it also leaves the portal cranial to theinfraspinatus tendon available for the egress cannula. In adulthorses the cranial portal can also provide access for thesurgeon to insert a curved, blunt-tipped forceps acrossthe non-articular portion of the shoulder joint to engage theglenoid notch and distract the humeral head from the glenoidby rotation of the forceps. This allows the arthroscope to beadvanced safely to the medial aspect of the joint (Fig 8.13). Athird portal. 2-4 cm caudal to the arthroscope entry portal,is used as an instrument portal for arthroscopic surgery bytriangulation. This method of internal distraction precludesthe need for external traction; however. since it risksiatrogenic damage to the cranial aspect of the humeral head,it is generally used only in heavily muscled mature horses.For surgical debridement of most OCD lesions, the youngerage of the horse and the chronicity of the disease providesufficient laxity that fluid distention and axial traction areadequate to allow access to most regions of the articulation.

The primary indication for diagnostic arthroscopy of theshoulder joint is the evaluation and treatment of osteo-chondrosis section). Diagnostic arthroscopy is also indicatedwhen lameness is localized to the shoulder by response tointra-articular anesthesia but whenare equivocal. In such cases, fibrillation of the

dissecans. the arthroscopic findings do :-with the radiographic changes. and the diagnostic examin-

lation is a critical part of the arthroscopic procedure. Arthro-scopy is also appropriate in cases of septic arthritis. both forevaluating the articular cartilage and for treatment. 1

Using a probe during diagnostic arthroscopy of theshoulder joint is critical. An instrument portal is necessaryfor probe placement. and creation of this portal is described inthe next section. The optimal site to insert the probe isascertained using an I8-gauge. 3-inch spinal needle.

In addition to defining intra-articular disease entities.arthroscopy has been used in human patients with shoulder

instability and in assessing cases of supraspinatus tendinitis(Cofield 1983), ruptured biceps tendon, and loose bodyremoval Oohnson 1986). Such indications have not beenrecognized in the horse as yet; the horse does not have aglenoid labrum.

chondrosis in the shoulder. In many instances,is evaluated after the elimination of problems in 1limb with the use of nerve blocks.

The diagnosis of osteochondrosis is confirmed]graphically. Standing radiographs may be taken. and

Arthroscopic Surgery of theShoulder joint for Treatmentof Osteochondrosis

are sometimes necessary to provide images of rquality to rule out the presence of any lesions in IRadiographic signs of osteochondritis dissecans inhumeral head include malformation of the.flattening and/or undulation of the bone caudally,

caudal portion of the humeral head, particularlyphyseal junction, may be seen. Occasionally, ( .

development is evident without other radiographicosteochondritis dissecans.

Radiographic abnormalities in the scapula thatconsidered to relate to osteochondrosis j ,

of osteochondritis dissecans, osteochondraland abnormal flattening of , c .8.16). In most instances, the glenoid cavity develops

border. More chronic shoulder OCD cases have

As mentioned previously, non-surgical treatment of osteo-chondrosis in the equine shoulder has rarely allowed horsesto regain athletic capability. Three different arthrotomyapproaches have been used to treat cases of osteochondrosisin the equine shoulder. Complications of loss of lateralsupport (Schmidt et al197S), limited access (DeBowes et al1982), and seroma formation (Nixon et al1984) have beenseen, but probably of more importance is the fact thatcomplete visualization of the articulation is not possible withan arthrotomy incision (Nixon et al1984). Extensive tractionis also critical to the performance of the procedure.

Arthroscopy provides advantages over arthrotomy in bothavoiding these complications as well as providing additionalbenefits through the minimally invasive approach. It shouldbe stressed, however, that adequate arthroscopic visualizationand surgical manipulation in the equine shoulder joint aremore difficult than in other joints described previously inthis text.

The material presented is based on the experience of theauthors, both in evaluating the approaches in cadavers aswell as involvement in 114 clinical cases, including a pre-viously published series of cases of osteochondrosis withfollow-up (Nixon 1986, Bertone & McIlwraith 1987a).

formation on the caudal aspect of the glenoid. Ininstances. however. r ." ,articular ( .-'-

1987a).Arthrography of the shoulder' .-

a technique to diagnose OCD. but more importantly.

to those that are eroded to the extent that they aresalvage (Nixon & Spencer: ' -, --

head and glenoid cavil,that one cartilage surfPreoperative considerations

Most patients manifest clinical signs before 1 year of age. Theage of presentation does depend somewhat on the observationskills of the owners. In some cases, a recent history of lamenessmay be described. Contracted conformation of the feet signifiesmore accurately the duration of a problem. Preoperativeclinical signs include lameness with a shortened cranialphase of stride. Some horses show resentment to firm digitalpressure caudal to the infraspinatus tendon. Extension andflexion of the shoulder joint is also resented in some cases.Intra-articular anesthesia of the shoulder joint improves oreliminates the lameness in most cases. However, when thearticular cartilage over subchondral bone defects is still intact,intra-articular local anesthesia may not generate a response.Intra-articular anesthesia is performed by using the samelandmark as previously described for placing the spinal needleduring arthroscopy. The absence of these localizing clinicalsigns, however, does not rule out the presence of osteo-

prognosis, and can lead to surgery and generally aoutlook (Fig. 8.18).

Arthroscopic technique

A thorough exploration of the scapulohumeral joint,previously described, is performed as the first step. r

exploration involves probing all visible lesions as well

entry for triangulation during arthroscopic surgery inshoulder, is illustrated in 1 .-.

is selected to permit access to the caudal humeral rcentral articular surface of the glenoid. To determinelocation. an I8-gauge spinal needle is inserted about (caudal to the infraspinatus tendon and 4 cm distal (-arthroscopic portal (Fig. 8.20). This location usually f

When the needle position is judged to be satisfactory, an8 mm skin incision is made at that location. and a stabincision is continued into the muscle mass with the use of aNo. 11 or 15 blade (Fig. 8.21). A conical obturator is insertedalong the same path to ensure the presence of a workableportal. It is important that fluid pressure be at a minimum atthis time. When the portal is unobstructed. intermuscularextravasation of fluid is minimal, although it usually becomesa problem later during surgery, regardless of the portal size.

The shoulder is one of the few sites where screw-in self-sealing cannulae are useful to prevent massive subcutaneousfluid accumulation. They limit the size of instrument entry,and so must be at least 7 mm internal diameter to be useful(described in Chapter 2). A blunt probe is initially passedthrough the instrument portal to evaluate the lesions in thejoint.

to palpate the articular cartilage peripheral to thedefects, and to explore the extent of the undermined cartilagein osteochondritis dissecans lesions as well as the openings ofsubchondral cystic lesions. The presence of all lesions andtheir degree is ascertained before any surgical manipulationsare performed (Fig 8.22-8.31).

This caudolateral instrument portal is used for debridingmost lesions. Laterally located defects are easier to operatethan medially placed lesions. Therefore, procedures involvinglesions on the medial side of the joint are performed firstwhile maximal joint distention can be maintained. andseparation of the glenoid and humeral head are achieved.Adjunctive traction is also sometimes necessary at this stage

~

as well. Surgical intervention on laterally placed lesions is stillpossible later. when joint distention has decreased.

Humeral head defects (see Figs 8.23 and 8.24) aredebrided initially with a hand curette or periosteal elevator;large pieces of cartilage are removed by using Ferris-Smith

rongeurs (Fig. 8.32). A motorized resector can be used fordebriding large lesions. The resector works well in thedebridement of easily accessible humeral head lesions. Whenthe defect is deeper within the subchondral bone, however,the resector and/or burr may not reach, and a right-angledcurette is used. Angled motorized resectors (see Chapter 2)can be very helpful to accommodate to the curvature of thehumeral head. Similarly, small angled rongeurs (patellar

forceps) can be helpful to enter deep OCD lesions and retrievecartilage flaps or debride subchondral bone (Fig. 8.34). At thecompletion of subchondral bone debridement, the edges ofthe defect are debrided with a hand curette and Ferris-Smithrongeurs. When intact articular cartilage overlies a sub-chondral defect (a common manifestation with osteochondritisdissecans in the shoulder), all cartilage superficial to thedefect is removed and the defect beneath is debrided. Figures

8.30 and 8.31 depict defects on the humeral head afterdebridement.

Similarly, articular cartilage fissures, areas of erosion, cyst-like lesions, and detached articular cartilage in the glenoid(Figs. 8.25-8.29) are debrided and removed by using Ferris-Smith disk rongeurs, patellar forceps, curettes (both straightand angled) and occasionally the motorized resector or burr.The concave shape of the glenoid sometimes makesaccessibility with the straight resector blade difficult. Anangled resector and the right-angled curette are particularlyuseful for debriding extensive lesions and deep lesions.Osteochondral fragments are rare in the shoulder.

In some cases, an additional cranial incision or exchangeof the arthroscope and instrument portals is needed to gaininstrument access to the cranial aspect of the joint (Figs 8.35and 8.36). Alternatively, using the lateral arthroscope entrytechnique, the arthroscope remains caudal to the infraspinatustendon, leaving the existing portal cranial to the infra-spinatus tendon free for rongeurs or curettes, which replaceany egress cannula that have been placed during the initialphase of surgery. Instrument entry through the cranial portalallows removal of free osteochondral fragments from thecranial cul-de-sac of the joint or access to lesions of thehumeral head that extend more cranial than normal

(Fig. 8.37).At the completion of the procedure, the joint is lavaged by

using a large-bore (4.5 mm) egress cannula through theinstrument portal (Fig. 8.33). Suction is usually applied atsome stage to ensure removal of debris. As discussed in

a focal subchondral cystic lesion may also be noted.

the cyst (Fig. 8.25).

Postoperative management

Antibiotics are administered perioperatively and for 2 days ipostoperatively. Phenylbutazone is administered on the day of jthe operation and for the successive 3-5 days. Horses areconfined to a stall for 10 days, at which time hand walkingcommences. We usually start with hand walking for5 minutes per day, with incremental increases of 5 minuteseach week to 30 minutes per day. Horses are then turned outfor periods of 4-12 months before forced exercise begins.

Problems and complications

and surgical manipulation are more difficult in tJshoulder joint than in most other joints in which artisurgery is commonly performed. A definite J '

most people experience one or more of thedifficulties and complications.

Arthroscopic placement in the joint

tDifficulty can be experienced with this step. Accurateplacement of the spinal needle. predistention of the joint. andpractice alleviate this problem.

Chapter 3. the use of a motorized pump is important in casesinvolving extensive lesions. With an open large bore egress

cannula in position fluid flow is usually set at maximal tolavage the joint effectively.

As recorded previously (Bertone & McIlwraith 198 7a). thelesions found at arthroscopy are usually more extensive thanthey appeared radiographically. In most instances. thecartilaginous changes extend beyond the limits of the sub-chondral bone abnormalities observed on the radiographs.particularly in the glenoid of the scapula. In some horses inwhich radiographically the lesion appears limited to theglenoid or humeral head, additional lesions are foundarthroscopically on the opposing articular surface. The mostcommon arthroscopic abnormalities of the humeral head arecartilage discoloration with undermining and erosion downto subchondral bone on the caudal aspect of the articularsurface (see Figs 8.23 and 8.24). In some instances. a lesionis not visible initially and probing is required to ascertain thearea of undermined cartilage. The most common arthroscopicabnormality in the glenoid is cracked undermined articularcartilage with fissure formation and fibrillation (seeFigs 8.25-8.29). An additional common finding is friable,defective subchondral bone. and these lesions may extendquite deeply. In most horses. the center of the glenoid cavityis most severely affected. Occasionally. however, lesions extendlaterally to the glenoid rim, and the bone of the glenoid rimmay also be fragmented (see Fig. 8.29). In other instances,the medial portion of the glenoid is affected. Although adiffuse osteochondritis dissecans lesion is the most common

Difficulty in establishing triangulation

Visualizing the spinal needle is dillicult in certain cases due to

the depths of the joint from the skin surface, but the severity

of this problem decreases with surgical practice. Changes in

limb position and difference in the size of the patient can

confuse the operator. For most instances in which access to

the joint was not achieved initially, the needle was placed too

cranial and/or too proximal. Maintaining the limb in an

unsupported, adducted (resting) position facilitates joint

entry by widening the lateral aspect of the joint.

Extravasation of fluidsExtravasation occurs in all shoulder arthroscopy cases to

some degree. During surgery the amount of fluid in the peri-

articlar tissue increases. causing increased extra-articular

pressure. This increase in turn produces technical difficulty,

such as collapse of the joint space and decreased ability to see

and manipulate instruments. An efficient surgical procedure

is critical in operations involving the shoulder. A clear.

unobstructed instrument portal. careful control of fluid

ingress and judicious use of self-sealing cannulae also

improve surgical procedures in this region.

Difficulty in reaching potential lesions

In some instances. the surgeon may visualize lesions and notbe able to reach them with the instruments. These lesions areusually located on the caudomedial surface of the humeralhead of adult horses and become even more difficult to accessin well-muscled patients. In one series (Bertone & McIlwraith1987a), the problem of inadequate instrument length wasencountered in three horses. Debridement of these areas canbe performed in young horses without difficulty, where tractionon the limb opens the joint space and facilitates curettage ofthe medial surfaces. However, the ideal instrument forreaching medial lesions in larger horses has not been found.Long rongeurs are rare, and instruments with some curvatureare also difficult to find. It is important to advise owners thatcomplete debridement may not be achieved when the horseweighs 500 kg or more. Large accumulations of subcutaneousfluid also contribute to inadequate instrument length, andperiodic application of pressure massage to drive fluid out theskin portals often improves access to remote regions of thehumeral head.

Damage to instruments

The instrument portal passes through 6-8 cm of musclebefore entry into the joint. Manipulation of the instrumentsis restricted by this muscle mass. The instrument portal canbe enlarged, but. in certain instances, the probe or trocar hasbeen bent when removed.

One possible solution to the difficulty sometimes experi-enced in maintaining separation of the glenoid and humeralhead (this distance becomes critical when fluid extravasationinhibits distention) is placing the patient in dorsal recumbency.By

suspending the leg and lowering the table slightly, "gravitytraction" may provide a less energy-consuming alternative.The authors have not tried this technique. The possibility ofdamaging the brachial plexus is one potential hazard.Transient paresthesia in the upper extremities after shoulderarthroscopy involving traction was reported in man, andbrachial

plexus strain versus joint accessibility with differentshoulder positions has been described (Klein et al19 8 7).

Results

horses were completely sound at a jog within 4 months. Fivehorses were atWetically sound and were being shown, ridden,or raced after 5-20 months. A sixth horse was sound whenbeginning race training. A seventh horse was pasture soundand was to begin race training at the time of the report. Aneighth horse showed well in halter for 12 months, butshoulder lameness returned. This horse was donated, and anecropsy was performed. The ninth and tenth horses werenot completely sound at 11 months. The eleventh horseimproved but remained lame and could not be used forathletic performance.

Follow-up radiographic assessment revealed improvementin contour of the humeral head and joint space and moreeven density of the humeral epiphysis and the glenoid of thescapula in 6 horses. One of these horses showed markedimprovement in subchondral bone density and surfacecontour of the glenoid cavity. In 2 of the remaining 5 horses,the caudal border of the glenoid cavity had remodeled toappear more like the contralateral joint. In the fourth of the6 horses, radiographs obtained 1 year later showed a sub-chondral cystic lesion in the scapula (1.5 cm in diameter)that had not been present previously (Fig. 8.38). However,this horse was athletically sound. The contour of the glenoidarticular surface and its caudal border was smoother post-operatively and the subchondral osteosclerosis was reducedin thickness. In the fifth horse in this group, an osteophyte onthe humeral head had enlarged, but improvement was notedin joint contour of both the humeral head and glenoid cavity(Fig. 8.39). Radiographs obtained from one of the two horsesthat improved but were still lame showed no improvement inthe glenoid lesion radiographically. In the horse whereeuthanasia was chosen when it deteriorated clinically, thehumeral epiphysis was severely distorted with a defect in thearticular surface contour, a subchondral cystic lesion, and asmall intra-articular fracture of the cranial margin of the

glenoid cavity.In summary, all 11 horses improved clinically. Soundness

was achieved in 9 horses, and 5 of 11 horses have been usedathletically. Two horses did not become sound. One of thesehorses was young but had extensive lesions of the glenoidcavity and humeral head; a large osteophyte also developed.The other horse was 4 years of age at the time of surgicalintervention and did show some clinical but no radiographicimprovement. One horse developed severe degenerativechanges in the joint after being sound for 8 months. It seemsthat considerable healing response can be obtained if surgicaltreatment occurs in a timely fashion.

Hand curettage was satisfactory for treating most lesions,but the motorized resectors and burr provided the mostefficient debridement of articular cartilage and subchondralbone in both the scapula and humerus, and it avoided thepotential difficulties associated with hand curettage.Osteochondrotic lesions of the humeral head were the easiestto debride, especially in horses that were yearlings oryounger, because they had less muscle mass as well as moreflexible periarticular structures. However, the lesions wereaccessible even in older horses when the joint was distracted.Traction is extremely important for access to extensive

The initial series of 11 horses reported by the authorsincluded one postoperative complication (Bertone & Mcllwraith1987a): a subcutaneous infection with Actinobacillus sp.produced swelling and drainage from the incision 48 hoursafter surgery. The incision and subcutaneous tissues wereopened. flushed. and allowed to heal by second intention.Moderate swelling in the shoulder region in all horses.resulting from leakage of lavage fluid subcutaneously andintramuscularly. generally resolved within 7 days.

None of the horses were more lame postoperatively. and allimproved clinically from within 2 weeks of the operationuntil the time of follow-up evaluation. Nine of the 11 horsesachieved soundness and 8 horses remained sound. Seven

bearing areas, contributing to expansion of iin the bone (Landells 1953).

The radiographic evidence of remodeling of thecavity and humeral head in six horses less than 1 ~may help explain the clinical improvement in severe

scapular lesions, but arthroscopic surgery in the treatment ofthese lesions is recommended only for surgeons withconsiderable experience with this technique.

Euthanasia was chosen for four horses in this study. On thebasis of ideas concerning postoperative healing gained fromthese four cases, it appeared that lesions of the humeral headhealed with successive layers of hyaline cartilage, fibrocartilage,and fibrous tissue. Whether the hyaline cartilage representedremnants from surgery or transformation of fibrocartilage tohyaline cartilage is unclear. The quality of the repaired tissuevaried. From necropsy findings in three cases in whichglenoid lesions were debrided, it seemed these lesions did notheal as well as similar lesions of the humeral head. The defectswere filled with mixtures of fibrous tissue and fibrocartilage.In addition, cystic lesions in the bone also developed.

The development of cystic lesions in the subchondral boneof the glenoid subsequent to surgery is an interesting finding.This may be a sequel to untreated osteochondritis dissecansor to debridement in which the articular cartilage is removeddown to subchondral bone. Subchondral bone cystic lesionscan form in normal joints if full-thickness articular cartilagedefects are created surgically in weightbearing areas(Kold et al1986). These lesions can develop within 6 months,and some authors state that intra-articular synovial fluidpressure may exceed subchondral bone pressure in weight-

Since this published series. the authors have

and humeral head and have achieved considerableimprovement. ] , .

to avoid operating on these types of lesions usuallyhigh detail preoperative radiographs or even [ .'

Additionally. older horses may have a poor prognosis becausecartilage remodeling decreases with advancing age.

A more recent survey of 70 cases of one author (C.W.M.)reveals an overall success rate for return to athletic activity

of 45%.

cases

of osteochondritis dissecans. In each instance. thehorse was involved in athletic activity when the problemdeveloped.

The lesions manifested arthroscopic ally as areas offibrillation and were treated with debridement.

Articular fractureArthroscopic Surgery forOther Clinical Entitiesin the Shoulder

Some

fractures of the glenoid and portions of the perimeter ofthe humeral head can lead to severe lameness, and requireremoval

of fragments to improve the outcome. Fragmentationof the cranial or caudal glenoid rim can be removedarthroscopically, while larger fractures generally requirecompression by lag screw insertion. Extensive craniocaudallyoriented

fractures of the glenoid cavity, which extendproximally to involve the neck of the scapula, may requireboth arthroscopic debridement and small fragment removal,and then screw compression. These types of fracture canappear normal in lateromedial radiographs, largely becauseof the minimal craniocaudal displacement of the fracture.

Osteoarthritis

The authors have been involved in seven cases in which thehorse was considered to have degenerative articular cartilagelesions of the humeral head that differed from the typical

Septic arthritis/osteomyelitis

Foals

and weanlings are predisposed to septic physitis andosteomyelitis. which can seed a joint and necessitate furtherdebridement. Routine arthroscopy of the shoulder for

fibrinectomy and removal of inspissated debris is required forresolution in advanced cases. Lateral or cranial arthroscopicapproaches provide visualization of the joint surfacessufficient to allow debridement of synovial membrane andcartilage.

The large caudal and cranial cul-de-sacs needparticularly aggressive lavage and manual fibrin removal toreduce

the bacterial load. Debridement of deeper lesionsinvolving cartilage and subchondral bone may occasionallybe

necessary (Fig. 8.40). Placing ingress drains for antibioticdelivery can also improve the outcome. Additional detail isprovided

in Chapter 14.

ReferencesBertone

AL. McIlwraith CWo Arthroscopic surgery for the treatmentof osteochondrosis in the equine shoulder joint. Vet Surg 1987 a;16(4): 303-311.Bertone

AL. McIlwraith CWo Arthroscopic surgical approaches andintraarticular anatomy of the equine shoulder joint. Vet Surg1987b; 16: 312-317.

Cofield RH. Arthroscopy of the shoulder. Mayo Clin Proc 1983; 58:501-508.DeBowes

RM. Wagner PC. Grant BD. Surgical approach to the equinescapulohumeral joint through a longitudinal infraspinatustenotomy. Vet Surg 1982; 11: 125-128.

Johnson u,. Arthroscopic surgery principles and practice. 3rd edn.St. Louis: Mosby; 1986.

Klein AH. France JC. MutscWer TA. Fu FH. Measurement of brachialplexus strain in arthroscopy of the shoulder. Arthroscopy 1987;3: 45-52.Kold

SE. Hickman J. Melsen F. An experimental study of the healingprocess of equine chondral and osteochondral defects. Equine VetJ 1986; 18: 18-24.

Nixon AI. Stashak TS. et al. A muscle separating...,

Vet Surg 1984; 13; 247-256.Nyack B. Morgan JP. et al. Osteochondrosis of the shoulder

the horse. Cornell Vet 1981; 71: 149-163.

osteochondrosis in the horse. Proc 31st Annual Conv1986.

Schmidt GR. Dueland R. Vaughan JT. .-

the equine shoulder joint. Vet Med/Small An Clin 1975;542-547.

Landells JW. The bone cysts of osteoarthritis. J Bone Joint Surg Br1953; 35-B: 643-649.

Mason TA. Maclean AA. Osteochondrosis dissecans of the head ofthe humerus in two foals. Equine Vet J 1977; 9(4): 189-191.

Meagher DM. Pool RR. O'Brien TR. Osteochondritis of the shoulderjoint in the horse. Proc Am Assoc Equine Prac 1975; 19: 247-256.

Nixon AJ. Diagnostic and operative arthroscopy of the equineshoulder joint. Vet Surg 1986; 15: 129.

Nixon AJ. Diagnostic and surgical arthroscopy of the equineshoulder joint. Vet Surg 1987; 16: 44-52.

Nixon AJ, Spencer CPo Arthrography of the equine shoulder joint.Equine VetJ 1990; 22(2): 107-113A.

ER

~

diseases such as osteochondral fragmentation,, or traumatically induced cartilage

frequency to warrant techniques for arthro-surgery of the various pouches of the elbow joint.

'humeral condyle or

the humeral condyles, this can be overcome to some extent bythe large range of motion of the elbow, allowing articularsurfaces to be exposed by flexion or extension. The tightarticulation essentially divides the elbow to a cranial jointpouch, a limited caudal joint pouch, and a large proximo-caudal joint pouch surrounding the anconeal process.

Approaches to the cranial portion of the elbow joint placesmall terminal branches of the radial nerve at risk as theyarborize and terminate in the antebrachial extensor musclebellies. The arthroscope entry avoids these branches; how-ever, instrument access cranially, through the muscle bellies,may impact on several small branches of the radial nerve. Noclinical repercussions, including extensor muscle dysfunction,have been recognized. The caudomedial approach to theelbow joint penetrates between the muscle bellies of the flexorcarpi radialis and flexor carpi ulnaris, and inadvertent entrycaudal to the flexor carpi ulnaris places the arthroscope closeto the ulnar nerve coursing over the caudomedial aspect ofthe humerus and continuing down the medial aspect of theulna. Similarly, inadvertent entry to the elbow joint cranial tothe flexor carpi radialis muscle belly places the median nerveat risk. During the caudomedial approach to the elbow, theinstrument entry often penetrates through the flexor carpiulnaris muscle belly, but also without repercussion. Thecaudal extremity of this approach also may impact onportions of the ulnar nerve. The approach to the olecranonpouch of the elbow penetrates the distal terminal portions ofthe triceps musculature or tendon of insertion; however, nosignificant neurovascular structures are at risk using thisapproach.

a second describing seven horses (Hopen et al 1992).

Other lesions. including osteochondritis dissecans.the humeral condyles. may be more appropriatelyby surgical debridement. Arthroscopic techniquesaccess to the cranial portions of the humeral

.both condyles and to the anconealthe ulna using a caudoproximal approach via the

complexity of periarticular neurovascular structuresinherent risks of elbow arthroscopy are well known in(Lynch et al1986, Thomas et al1987, Baker & Jones

1999). and have also been described to a limited extent in thehorse (Nixon 1990). Overall, arthroscopic access to the cranialregions of the elbow in man and horses is relatively simple.while the caudal compartments are more challenging, withincreased risk to adjacent neurovascular structures (Nixon1990. Poehling & Ekman 1994. Baker & Jones 1999).

The elbow joint of the horse is a complex articulation of thehumerus. radius, and ulna. All three bones are intimatelyconnected by substantial collateral ligaments. As a result.distraction of the humeroradial articulation and humeroulnararticulation results in little separation of the articularsurfaces and therefore limited access to regions predisposedto disease. particularly the proximal surface of the radius. For

Positioning

Positioning for arthroscopy of the elbow is dictated by the siteof surgical disease. Only dorsal recumbency will allowsimultaneous access to all three pouches of the elbow joint.However, this can increase the degree of difficulty in

arthroscopic access to the caudoproximal olecranon pouch.For access to specific disease conditions involving the cranial,caudal, or caudoproximal region of the elbow, lateralrecumbency is preferred. The cranial pouch and the caudo-proximal pouch of the elbow can be accessed with theaffected limb uppermost, while access to the caudomedialpouch requires the affected limb to be placed down on thesurgery table. Repositioning the horse from affected limbdown to affected limb uppermost during the surgicalprocedure is another possibility, although this delays thesurgical process. is manpower demanding, and risks breaks insterile procedures.

Craniolateral approach to the elbow

Caudomedial approachto the elbow joint

Dorsal positioning can be used if access to !joint pouches is expected, as previously described.preparation and draping, the site for arthroscopeidentified by systematically palpating from cranial!to identify the medial collateral ligament, the r

The horse is positioned in lateral recumbency so the limb canbe manipulated into extension and flexion of the elbow joint.After preparation and draping, the elbow joint is distendedthrough the cranial pouch with 40-60 mlof lactated Ringer'ssolution. The cranial perimeter of the humeroradial articu-lation is palpated cranial to the lateral collateral ligament anda 5-mm stab incision made approximately 2-3 cm cranial tothis palpable collateral ligament border. The muscle belly ofthe common digital extensor forms a cranial limit to thetriangular target area for access of the arthroscope. If theentry is made too close to the cranial palpable border ofthe lateral humeral condyle. manipulation within the cranialpouch of the elbow becomes more difficult. The arthroscopesleeve is inserted across the cranial pouch of the elbowjoint, and the obturator exchanged for the forward obliqueviewing arthroscope (Fig. 9.1). The cranial articular surfacesand cranial joint pouch of the elbow can then be examined(Fig. 9.2). The arthroscope is inserted as deeply as possibleto examine the craniomedial margins of the radius andhumerus. A 700 arthroscope may be useful in this region;however, it is not essential. Withdrawal of the arthroscopeidentifies the medial followed by the lateral condylesof the humerus, with a large synovial fossa interposedbetween the two (see Fig. 9.2). Further withdrawal of thearthroscope reveals the lateral portion of the humeroradialarticulation and the lateral collateral ligament. Thecranial joint pouch of the elbow is voluminous and easilyexamined.

An instrument portal can be made cranial to thearthroscope entry, after placing a 7.5 cm x 18-gauge spinalneedle. This portal usually penetrates between the ante-brachial extensor muscle bellies, generally where a shallowdivision can be palpated between the extensor carpi radialisand common digital extensor muscles. The midcranial regionshould be avoided to minimize potential damage to thetransverse cubital artery. For lesions involving the cranio-lateral extremity of the radius or lateral humeral condyle. thearthroscope and instrument entry portal can be exchangedto provide instrument access to the lateral portions of thearticular perimeter. Following completion of the procedure.fluid is expressed from the joint and the skin incisions closedwith interrupted sutures.

the approximation of flexor carpi radialis and flexor Iulnaris muscle bellies. A needle is inserted to identifyhumeroradial articulation,articular level and between the muscle bellies of the i-carpi radialis and flexor carpi ulnaris is identified.palpable division between these muscle bellies is imore easily at the mid-radius level, and thetracked proximally to the point 2-3 cm distal to thethe humeroradial articulation. The palpable'

overlying superficial pectoral muscles and

Fig. 9.1Arthroscopic technique for access to the cranial pouch of theelbow joint. Arthroscope entry is made in the triangle formedby the craniolateral curvature of the lateral condyle of thehumerus, the proximal perimeter of the craniolateral surfaceof the radius, and the caudal border of the muscle belly of thecommon digital extensor tendon. Instrument entry can bemade between the muscle bellies of the common digitalextensor and extensor carpi radialis muscles.

arthroscope sleeve and obturator (Fig. 9.3). The arthroscopesleeve with obturator in place is advanced proximally in anoblique direction to enter the caudomedial aspect of theelbow joint pouch. When cartilage or bone are encounteredand joint fluid is returned through the egress outlets on thearthroscope sleeve, the conical obturator is replaced bythe arthroscope. In many instances the arthroscope sleevecan be inserted to its limit. as it penetrates into the caudal

fascia. Insertion of the arthroscope proximal to the level ofthe humeroradial articulation places the ulnar neuro-vascular structures at risk. particularly if a second entry forinstruments is then made caudal to the flexor carpi ulnarismuscle belly.

Mter insertion of the needle to the caudomedial aspect ofthe joint. the elbow is distended with 60 ml of lactated Ringer'ssolution and a 5 mm skin incision made for entry of the

limb is made easier by positioning the horse in lateral ratherthan dorsal recumbency. Manipulating the tip of thearthroscope caudally. exposes the trochlear notch of the ulnaand the apposing articular surface of the humeral condyles(Fig. 9.4). Further caudally, the intrusion of the medial epi-condyle of the humerus. and the proximal regions of thetrochlear notch of the ulna are evident (Fig. 9.4). The largetendon of origin of the humeral head of the deep digitalflexor tendon is also visible. The space between the trochlearnotch of the ulna and this mobile tendon provides access tothe caudoproximal cul-de-sac of the elbow. However. for easeof surgical manipulation, the caudoproximal approach to thiscul-de-sac using a lateral access technique is recommended

(described later).Instrument entry portals are made through the muscle

belly of the flexor carpi ulnaris. caudal to the arthroscopeportal. The most suitable path for instrument entry is selectedafter inserting a 7.5 cm long spinal needle. This providesready access to the medial condyle and the medial aspects ofthe lateral condyle. The central regions of the capitular foveaof the radius cannot be accessed surgically.

Caudoproximal approach to theelbow Joint

The voluminous caudoproximal pouch of the elbow joint canbe accessed using approaches similar to those described forarthrocentesis of the elbow (Stashak 1987). This approach isbest done with the horse in lateral recumbency with the limbfree to be manipulated through flexion and extension. Thejoint is distended with 60-80 ml of lactated Ringer's solutionusing a 7.5 cm spinal needle inserted over the lateral epicondyleto enter the lateral portion of the caudoproximal cul-de-sac ofthe joint. Needle entry is approximately level with the point ofthe elbow, and caudal to the palpable lateral epicondyle of thehumerus. The spinal needle is angled distally and cranially totarget the anconeal process of the ulna. Following removal ofthe needle, the skin incision for arthroscope entry is made ina similar location and the arthroscope sleeve and conicalobturator inserted, angling distally and cranially to contactthe articular surface of the anconeal process (Fig. 9.5). Theobturator is then exchanged for the arthroscope. allowingexamination of the voluminous caudoproximal joint pouch(Fig. 9.6). The anconeal process and proximal portions of thehumeral condyles are readily visible (Fig. 9.6). Flexion of theelbow exposes the entire caudal one-half of the humeralcondyles for surgical procedures. Instrument entry foraccess to lesions is then made by preplacing a 7.5 cmspinal needle to give direct access to lesions on the anconealprocess or humeral condyles. This entry usually perforatesterminal portions of the triceps musculature and occasion-ally the tendon of insertion on the olecranon. Handinstruments and motorized burrs can be inserted for surgical

debridement.

cul-de-sac of the elbow and farther into the caudoproximalcul-de-sac surrounding the anconeal process. A standardforward oblique arthroscope is inserted and the caudalregions of the elbow examined. The medial humeral condyleis readily visible (Fig. 9.4). The caudal perimeter of thehumeroradial articulation is a convenient landmark tocommence examination of the joint (Fig. 9.4). The articularsurfaces of the humeral condyles, particularly the medialcondyle. are readily evaluated. Flexion of the elbow improvesthe exposure of the caudal portions of the humeral condyles.Portions of the weightbeai"ing articular surface of the radiuscan be seen. but the arthroscope cannot be advancedbetween the radius and humerus (Fig. 9.4). Distraction of themedial aspect of the humeroradial joint by abduction of the

of the radius (capitula fovea of the radius). Conservative

therapy of subchondral cystic lesions of the proximal radius

is generally accepted as the treatment of choice for these

subchondral cysts (Hopen et a11992) (Fig. 9.8) but surgical

treatment has also been successful (Bertone et al1986). OCD

lesions of the humeral condyles can involve the caudal one-

half of either the medial or lateral condyle (Hopen et al19 92).

The flap lesions present as lysis on radiographs, similar to

OCD lesions in most other sites in the body (Fig. 9.9). Access

to lesions of the medial humeral condyle is provided using the

caudomedial arthroscopic approach. This provides visualization

but dillicult triangulation to lesions of the lateral condyle

(Fig. 9.10). Use of the caudoproximal approach with the

elbow fully flexed provides better access to the lateral condyle.

Triangulation is also easily accomplished using instrument

entry through the triceps muscle or the -;junction. This is a rare site for OCD in the horse. -

ence is limited j , ,

author (A.J.N.). 7"'-

favorable. with all going on to athletic work. 1 planning to decide the most appropriate' .'

approach to the humeral condyles requires a flexed

simpler, safer, and provides more extensive roommanipulate surgical instruments. Similar controversy:rounds treatment of elbow OCD in ] ,--

Pill et al2003), although the results ofsurgical treatment.

Fractures of the craniolateral portionof the humerus Fragmentation of the anconeal

The craniolateral portion of the distal humerus, particularlythe lateral portion of the humeral condyle, is exposed toexternal impact injury, which can dislodge intra-articularosteochondral fragments (Fig. 9.7). Removal of these frag-ments is generally simple using the craniolateral arthroscopicaccess. After examination of the remainder of the cranialaspects of the elbow joint, the arthroscope and instrumentportals are reversed, placing the arthroscope through aninstrument portal approximately between the muscle belliesof the extensor carpi radialis and common digital extensor.This leaves the more lateral portal for rongeur entry forfracture removal. Debridement of the subchondral bed isroutine and debris can be flushed from the joint with a largeegress cannula. The extent of articular involvement usuallydefines the expected outcome, although the predisposed areafor impact fracture is generally 2-4 cm in length.

The anconeal process can develop fragmentationmanifestation of osteochondrosis, f

process using the caudoproximal approach issimple (Fig. 9.11). Fragment removal can be rusing triangulation i ' '- ,- ;

fragments are rare in this location, and many offragments should be considered trauma-induced. :complex fractures of the I '

fixation. The open lateral approach to the anconealduring plate application to the olecranon fsimple, and arthroscopy can be utilized to ithe free fragment either during the plating(Fig. 9.11) or at a later time.

Septic arthritisOsteochondrosis and osteochondritisdissecans of the elbow

Osteochondrosis of the elbow usually takes the form of eitherOCD flap lesions of the humeral condyles or subchondralcystic lesions of the proximal radius. To date, there are noarthroscopic techniques that will provide access to the head

involved in hematogenous septic processes in foals.lateral aspect of the joint also has minimal: r .

and is a common site for kicks from other animals'frequently penetrate the joint through or adjacent tolateral collateral ligament. Lavage and flushing of

compartments of the elbow joint represents minimal therapyfor septic arthritis (see Chapter 14). Recalcitrant cases needarthroscopic exploration, using debridement of inspissatedand fibrinous material, and partial synovectomy ofproliferative regions. Arthroscopic exploration also allowsevaluation of the cartilage surfaces of the humerus and ulna,and debridement of any areas that have developed separationfrom the subchondral bone. The access to the cranial pouchof the elbow joint is relatively simple using the craniolateralapproach and, similarly, access to the proximal caudal jointpouch can be provided using the caudoproximal approach.Both can be accomplished with the patient in lateralrecumbency. The necessity to enter the smaller joint pouchassociated with the caudomedial arthroscopic approach isquestionable. Most areas of the joint can be adequately lavagedand inspissated material removed from the more voluminouscranial and caudoproximal pouches. Drains can be instilledor antibiotic repository devices placed in either or both of thecranial or caudoproximal pouches. The outcome for synovialsepsis is described in Chapter 14, and is generally dictated bythe extent of osteomyelitis in the subchondral bone.

prominent regions for osteophyte formation includecranial aspect of 1

lavage and chondroplasty for arthritis are questionablereview in Chapter 17); ]matic relief may be provided for several years.

Despite the complexity of the elbow articulation andproximity to important neurovascular structures. (

complication during arthroscopic procedures around 1elbow is subcutaneous fluid accumulation, which canextensive using the approaches described. Distention Ivisualization should be used in moderation, '

Arthroscopy for osteoarthritis

Arthroscopic exploration and debridement of areas of cartilagedegeneration in osteoarthritis is occasionally warranted.depending on the extent of osteophytosis in the elbow. The easily examined with moderate distention.

Necropsy examination of horses used in the developmentof arthroscopic approaches to the elbow showed minor areasof muscle hemorrhage associated with instrument entry duringtriangulation (Nixon 1990). The primary concern in elbowarthroscopy is surgical planning to provide access to the lesionswithout the necessity for repositioning the horse. The use ofdorsal recumbency can result in difficulty in orientation andmanipulation. but should be taken into consideration whenall three compartments of the joint need to be examined.

References

Hopen LA, Colahan PT, Turner TA, Nixon AJ. Nonsurgical treatmentof cubital subchondral cyst-like lesions in horses: seven cases(1983-1987). J Am VetMed Assoc 1992; 200: 527-530.

Krijnen MR, Lim L, Willems WI. Arthroscopic treatment ofosteochondritis dissecans of the capitellum: report of 5 femaleathletes. Arthroscopy 2003; 19: 210-214.

Lynch GJ, Meyers JF, Whipple TL, Caspari RB. Neurovascularanatomy and elbow arthroscopy: inherent risks. Arthroscopy1986; 2: 190-197.

Nixon AJ. Arthroscopic approaches and intraarticular anatomy ofthe equine elbow. Vet Surg 1990; 19: 93-101.

Pill SG, Ganley TJ, Flynn IM, Gregg JR. Osteochondritis dissecans ofthe capitellum: arthroscopic-assisted treatment of large, full-thickness defects in young patients. Arthroscopy 2003; 19:222-225.

Poehling GG, Ekman EF. Arthroscopy of the elbow. J Bone Joint Surg1994; 76A: 1265-1271.

Stashak TS. Diagnosis of lameness. In: Stashak TS (ed.), Adams'lameness in horses. Philadelphia: Lea and Febiger; 1987:150-153.

Thomas MA, Fast A, Shapiro D. Radial nerve damage as acomplication of elbow arthroscopy. Clin Orthop 1987: 130-131.

Baker CL Jr. Jones GL. Arthroscopy of the elbow. Am J Sports Med1999; 27: 251-264.

Bertone AL. Mcllwraith CWo Powers BE et al. Subchondral osseouscystic lesions of the elbow of horses: conservative versus surgicaltreatment. J Am Vet Med Assoc 1986; 189: 540-546.

Hardy J. Marcoux M. Eisenberg H. Osteochondrosis-like lesion of theanconeal process in two horses. J AmVet Med Assoc 1986; 189:802-803.

.~

The clinical signs associated with clinical hip lameness inhorses vary, depending on whether the derangement is aresult of developmental disease in foals and weanlings,trauma to the hip resulting in tearing of the ligament ofthe head of the femur, degenerative osteoarthritis, or fractureof various portions of the acetabulum (Rose et al 1981,Miller & Todhunter 1987, Nixon et al1988). Under the bestof circumstances, the diagnosis of hip disease is oftenprotracted, leading to osteoarthritis as a common sequela.When the lameness is marked, muscle atrophy of the affectedhind limb is evident in the gluteal and quadriceps mus-culature, facilitating an earlier diagnosis. More obscureupper hind limb lameness may take more diligence in thework-up. Diagnostic manipulative tests are useful; however,the definitive diagnosis often requires intra-articular anesthesia.Rectal examination is also recommended, although palpableenlargements have been recorded in only 50% of acetabularfractures (Rutkowski & Richardson 1989). and many otherconditions including OC and OA are not detected using rectalexamination.

Nuclear scintigraphy has improved the diagnosticspecificity for chronic hind limb lameness. but still lacks theconclusive nature of intra-articular anesthesia. Blocking thehip can be difficult until some familiarity with the surfaceanatomic landmarks is gained. Later confirmation andstaging of the degree of the hip joint involvement can be

provided by radiographs. Good-quality radiographs requiregeneral anesthesia. and ventrodorsal and oblique ventrodorsalviews for evaluation of the acetabulum and femoral heads.Moderate and severe degenerative osteoarthritis, osteochon-drosis, osteochondritis dissecans (OCD), and luxation or sub-luxation of the hip are apparent on hip radiographs. Lessobvious hip diseases, such as tearing of the ligament of thehead of the femur and mild osteoarthritis, may not be evidenton routine radiographs. These lesions may need to beidentified through direct visualization during arthroscopicexamination.

recognize, and the need for arthroscopic evaluationdiagnostic arthroscopy and

surgical correction of problems in the hip arerare. They may be in part due to the inherent

of isolating problems to the coxofemoral joint,horses with chronic lameness. Moreover, the

associated with surgical therapy often diminishfor arthroscopic exploration. However, an

awareness of hip joint diseases and the use ofimaging modalities such as nuclear scintigraphy andthermography, coupled with increased use of intra-articularanesthesia, have increased the likelihood of establishing adefinitive lameness associated with the coxofemoral joint. Alogical extension of improved diagnostic capabilities is the useof arthroscopic examination with a view to surgical correctionof some diseases. Arthrotomy of the hip joint is difficult,results in limited exposure of relevant structures, is debilitatingfor the horse and surgeon, and is accompanied by high-woundhealing complication rates: given this, it is rarely warrantedfor any surgical disease of the hip, other than separation ofthe proximal femoral capital physis. However, arthroscopyfor diagnostic purposes is feasible, particularly in foals(Honnas et aI1993).

Diagnostic arthroscopy has been used to evaluate tearingof the ligament at the head of the femur (round ligament),osteoarthritis (qA) , fracture of the acetabulum, and osteo-chondrosis (DC) in the hip (Nixon 1994). In man, diagnosticarthroscopy of the hip is a useful technique to establish adiagnosis, as well as aid in treatment; it actually altered thepreoperative diagnosis in 53% of 328 patients (Baber et al1999). Given the preoperative use of computed tomography(CT) and magnetic resonance imaging (MRI) in man, theseresults represent a marked increase in diagnostic usefulnessof arthroscopy. In foals, arthroscopic surgery is particularlyvaluable in the treatment of sepsis involving the coxofemoraljoint, and in the treatment of osteochondrosis (Nixon 1994).

to penetrate the joint of horses less than j

arthroscope sleeve and 4-mm forward oblique viewingarthroscope (Fig. 10.2). However, a longer arthroscope (25-cmarthroscope, Karl Storz Endoscopy, Goleta, CA) is useful formore complete examination in adult horses (Fig. 10.3). Thearthroscope sleeve and conical obturator are insertedthrough the skin and angled 200 ventral and 200 cranially, tofollow the dorsal (proximal) contour of the femoral neck(Fig. 10.1). The lateral portion of the hip joint is penetrated,the obturator removed, and the arthroscope inserted. Thestandard 25 or 300 forward oblique viewing arthroscopes aresatisfactory for examination of most regions of the hip joint. i

J

A 700 arthroscope is useful but not essential to examine the 1,

Arthroscopy is indicated for the diagnosis of hip joint disease,particularly in cases in which radiographs provide littleadditional information after a positive intra-articularanesthetic response has been obtained and as a therapeutictool for other conditions. Arthroscopic examination of the hipjoint in horses has been described in a limited case series(Honnas et al199 3, Nixon 1994). Arthroscopic visualizationwas useful in determining the extent of cartilage damageassociated with fractures of the acetabular rim, in severalcases where radiographically visible small fractures wereidentified associated with the periphery of the acetabular rim,in assessing the degree of tearing of the ligament of the headof the femur, and in cases where cartilage defects wereevident during examination of horses with hip joint lamenessbut no radiographic lesions (Nixon 1994). Intra-articulardebridement of torn and partially torn ligaments of the headof the femur, debridement of OCD of the acetabulum, andcystic lesions of the femoral head have been described (Nixon1994). Similarly, arthroscopic lavage and synovectomy withdebris removal is a u~eful method for improving the responsein foals with infectious arthritis of the hip.

Surgical technique

Arthroscopic examination of the hip joint is readilyaccomplished in foals and can be performed with somedifficulty in horses up to 500 kg. In larger horses, exam-ination of the articular structures is less complete; theprocedure is more technically demanding and is associatedwith more surgical trauma to the articular and periarticularstructures than encountered during hip arthroscopy in foals.However, hip joint laxity associated with persistent effusionprovides a largely unrecognized advantage in adult horseswith chronic hip disease. With appropriate axial traction onthe affected hind limb. the femoral head can be distractedfrom the acetabulum sufficiently to allow examination oflarge portions of the femoral head and acetabulum.

The horse is anesthetized and positioned in lateralrecumbency with the affected limb uppermost. The entirelateral region of the hip and gluteal muscle is draped forsurgery with the affected limb supported but free to bemobilized during surgery. An arthroscope entry portal ismade at the site that has been previously described for intra-articular anesthesia (Stashak 1987, Nixon 1994). A skinincision is made between the cranial and caudal portions ofthe greater trochanter, entering approximately 2 cm proximalto the palpable level of the trochanter (intertrochanteric fossa)(Fig. 10.1). This provides arthroscopic access to both thecranial and caudal recesses of the hip joint. The joint isinitially distended with 60-80 ml of lactated Ringer'ssolution administered through a 15-20-cm spinal needle orth~ stvl~tt~ frQm a 15-cm intravenQUS catheter. The arthro-

skin portal, for fluid egress and later instrument access, ismade 4-5 cm cranial to the arthroscope portal. using a1 5-cm spinal needle or catheter stylette to define the path forinstrument entry prior to skin incision.

Visualization of the articular surface of the cranial,lateral, and caudal regions of the hip joint is accomplishedwith the limb supported in a horizontal position (Fig. 10.4).Manipulation of the limb into a flexed and extended positionallows other regions of the femoral head to be viewed. Giventhe depth of the joint from the skin surface. manipulation ofthe limb must be done with care, to avoid damage to thearthroscope. Distraction of the limb by axial tension is vitalfor a complete examination of the hip. This allows thearthroscope to be inserted between the femoral head and theacetabulum. In immature horses, distraction and arthroscopeinsertion can be accomplished easily and allow examinationof the deeper regions of the joint (Fig. 10.5). In older horses,distraction and increased intra-articular fluid pressures aremore important to allow visualization of the femoral headand round ligament of the head of the femur (Fig. 10.6). Jointdistraction can be provided by axial tension on the limb froman assistant or by mechanical devices such as a winchattached to the surgery wall. The torso of the horse must bestabilized on the surgery table when distraction techniquesare used. An intraoperative decision can be made as to thenecessity and degree of mechanical distraction. The use ofsurgical assistants is necessary for arthroscopy of the hipjoint in adults, primarily to manipulate the limb and toprovide axial distraction when required.

Instrument access is generally provided through thecranial instrument portal after developing a path to the hipjoint through the tendinous insertion of the middle glutealmuscle using a conical obturator. The arthroscope andinstrument portals can be exchanged for better examinationof the caudal acetabular rim. This allows entry for rongeurs 1and curettes through the original arthroscope portal. which jcan then be directed into the caudal regions of the joint. A jlong 6-mm diameter egress cannula (Sontec Instruments. jEnglewood, CO) or a second arthroscope sleeve is suitable for 1fluid egress after surgical debridement. The use of motorized jinstruments is possible in small and moderate-sized horses,but use of motoriz~(J ~m1inm~nt ~f!n h~ limitp(J hv thp (Jpnth

generally have either focal or more widespreadlesions associated with the femoral head and/orthe ligament of the head of the femur whenarthroscopic ally. Focal articularconfined to the cranial aspect of the femoral head

from the cartilage lesion (Fig. 10.7). Removal of the

instruments and motorized equipment need to be inserted tothe limits of their length. Pressing in on the skin and glutealmusculature occasionally allows an extra 1-2 cm of effectivelength to be garnered from routine surgical instruments.Long rongeurs and long egress cannulae are useful (SontecInstruments). Most surgical triangulation techniques in thehip are difficult. Debridement of cartilage lesions of thefemoral head and removal of free bodies and debris within thecranial and caudal recesses of the joint can be achieved withpersistence. Lesions in the acetabulum can be more difficultto debride. In smaller horses, examination and debridementof torn portions of the round ligament of the head of thefemur can be achieved. Osteochondrosis cysts of the head ofthe femur and fractures of the caudal acetabular rim areparticularly difficult to adequately debride.

improved lameness in two racehorses. More

osteophyte formation is often evident overcaudal perimeter of the acetabulum (Fig. 10.8).moderate osteoarthritis, most of these osteophytes

lesions of the femoral head can be accomplishedappropriate manipulation of curettes and rongeurscombination with axial distraction. A moderateiatrogenic damage to surrounding cartilage is alwayspossibility during debridement of these lesionsadvanced cases of hip joint osteoarthritis canarthroscopy (Fig. 10.9), however, lasting -following debridement of fibrillated regions is rare.

Tearing of the ligament of thehead of the femur

Fraying and tearing of

of hip joints from small breed horses. but can also be

Femoral head cartilage lesions of this ligament can occur, and the outlook evendebridement is guarded (Fig. 10.10). Tearing in -

hreeds. nHrtif'111Hrlv miniHt11re horses f'Hn he Hdp,

in those cases with incomplete rupture of the ligament(Nixon 1994). Manipulation of biopsy punch rongeursand motorized equipment is necessary fordebridement of the visible portions of theaccessory ligament of the head of 1difficult to visualize. and lesions in this

recognized.

Osteochondrosis anddissecans

the lateral half of the femoral head. Lesions in the

areas up to and including Iinsertion of the ligament of the head of the femur.deeper, more medial, aspects of l' ,

adequately visualized.extensive effusion, the hip joint is easily distracted. i '

better debridement of OCD lesions. Subchondral

the depths of the cyst can rarely be adequately debrided.Secondary packing of the debrided cysts with cancellousbone or other graft materials has not been possible. Cartilagelesions associated with the caudal perimeter of theacetabulum may not necessarily represent OCD. but can bedebrided with long rongeurs.

Acetabular chip fractures

Small fractures of the cranial and caudal perimeter of theacetabulum can be removed with rongeurs. More extensivefractures can be removed with some difficulty; however, theoutcome is rarely satisfactory, due to the resultant instabilityof the coxofemoral articulation (Fig. 10.13). Most of theseprocedures are tedious and time-consuming due to the increaseddepths of the joint from the skin surface. Insertion of instru-ments targeting the acetabular rim also places the sciaticnerve at risk, if the instrument rides over the acetabular rimand exits the dorsal (proximal) perimeter of the hip joint.

There are no large series of cases to describe the results ofdiagnostic or surgical arthroscopy for any of the conditionsin the equine hip. Diagnostic arthroscopy has been useful inthe treatment of septic hip joints in foals; however. a delay indiagnosis and involvement of other joints is common in foals.and reduces the likelihood of a sound horse. Diagnosticarthroscopy is also very useful to establish the severity ofcartilage injury in mild and moderate degenerative osteo-arthritis. Several cases have had focal cartilage injuries whichresponded particularly well to local debridement. Theestablishment of a more accurate prognosis is also a usefulbenefit of hip arthroscopy.

Surgical debridement can be expected to improve theoutcome with osteochondrosis and OCD conditions of thehip. Improvement in lameness after debridement of OCD flaplesions on the acetabular perimeter and after debridement ofsubchondral cysts of the femoral head have been seen. Accessfor debridement of femoral head lesions depends on thelateromedial location of the cysts within the femoral head.Debridement of relatively shallow cysts can be accomplished.and deeper cysts can be opened to some extent althoughdebridement is incomplete. In foals and miniature horses,debridement of fraying and tearing of the ligament of thehead of the femur can be easily performed, and at least withincomplete rupture, the results are quite satisfactory.Removal of frayed ligament fibers and lavage of debris fromthe joint improve the degree of lameness and minimizes thelikelihood of secondary osteoarthritis. Synovectomy ofportions of the accessible synovial membrane also appears toimprove the postoperative response in these cases. Completedisruption of the ligament of the head of the femur results inpermanent lameness. and long-term improvement after

Infectious arthritis

Arthroscopy provides an effective means for lavage anddebridement of debris from septic hip joints. The voluminouscranial and caudal recesses of the hip joint frequently containfibrinous and purulent debris. which can be removed bylarge-bore egress cannulae. or retrieved using rongeurs ormotorized resectors. Lavage can also be facilitated by asecond instrument entry portal for an egress cannula in thecaudal recess of the hip joint. Careful insertion of all instru-ments into the caudal region of the hip is necessary to avoidtrauma to the sciatic nerve.

Referencesarthroscopy has not been seen. These lesions need furtherstabilization. and techniques for hip stabilization have notbeen successful in adult horses.

The prognosis for a horse with hip disease depends on thetype of lesion. extent of degenerative osteoarthritis. and thecompleteness of lesion debridement. In some circumstanceship arthroscopy has improved the prognosis. whereas inother cases the extent of osteoarthritis and cartilage damagehas prevented a satisfactory outcome. Based on limited caseexperience. arthroscopic debridement of OCD lesions in thehip appears to improve the prognosis. whereas a diagnosis ofcomplete rupt,ure of the head of the ligament of the femuris a predictor of continued lameness. Synovectomy anddebridement of portions of incomplete rupture of theligament of the head of the femur have been useful inproviding lasting improvement in the level of lameness.Removal of chip fractures associated with the acetabular rimis possible; however. significant improvement in outcome isevident only with small fragments. Larger lesions result indestabilization of the articulation and little long-term benefit.

Baber YF, Robinson AH, Villar RN, Is diagnostic arthroscopy of thehip worthwhile? A prospective review of 328 adults investigatedfor hip pain, J Bone Joint Surg (Br) 1999; 81: 600-603.

Honnas CM, Zamos DT, Ford TS. Arthroscopy of the coxofemoraljoint of foals. Vet Surg 1993; 22: 115-121.

Miller CL, Todhunter R. Acetabular osteochondrosis dissecans in afoal. Cornell Vet 1987; 77: 75-83.

Nixon AJ. Diagnostic and operative arthroscopy of the coxofemoraljoint in horses. Vet Surg 23, 377-385.

Nixon AJ, Adams RM, Teigiand ME. Subchondral cystic lesions(osteochondrosis) of the femoral heads in a horse.J Am Vet MedAssoc 1988; 192: 360-362.

Rose JA, Rose EM, Smylie DR. Case history: acetabularosteochondrosis in a yearling thoroughbred. J Equine Vet Sci1981; 1: 173-175.

Rutkowski JA, Richardson DW. A retrospective study of 100 pelvicfractures in horses. Equine Vet J 1989; 21:256-259.

Stashak TS. Diagnosis of lameness. In: Stashak TS (ed.),Philadelphia: Lea and Febiger; Adams'lameness in horses. 1987:150-153.

16 Warmblood horses were reported. An arthroscopicapproach to the palmaroproximal and plantaroproximalaspect of the distal interphalangeal joints was subsequentlydeveloped by Vacek et al (1992), who described the anatomy.It was the author's opinion that most conditions affectingthese aspects of the coffin joint such as navicular bonefractures, arthrosis of the distal interphalangeal joint,penetrating wounds and septic arthritis, did not produceradiographic lesions in the acute phase and diagnosticarthroscopy was essential in establishing the diagnosis.Recently Brommer et al (2001) described a case of a Warm-blood yearling suffering from an osteochondral fragment atthe palmaroproximal aspect of the DIP (Figs 11.1 and 11.2).They successfully removed the fragment. which consisted of abony core completely surrounded by cartilage. They used alateral arthroscopic portal and a medial instrument portal.Another clinical use for this approach is in evacuation ofcysts in the navicular bone (Zierz et al2000).

Introduction

As in other small joints. arthroscopy in the distal and proximalinterphalangeal joints has specific features. The majordifferences between arthroscopy in "large" and "small" jointsare as follows:

.Exact anatomic positioning of arthroscope andinstrumental portals is extremely important in allsmall joints.

.Limited distention in small joints results in limitedfield of view.

.Limited distention and limited mobility in small jointsleads to difficulties in orientation.

.The tip of the arthroscope and the tips of instrumentsare always close to tissue.

.The tip of the arthroscope is always close to the tip ofhand instruments. which increases the risk of lens

damage..Diagnostic inspection of a small joint is done mainly

by lateral movement and rotation of the telescoperather than by inserting and withdrawing thearthroscope as in big joints.

.Re-arthroscopy is almost always performed throughthe same initial portals.

.It is delicate surgery with delicate surgical equipment-equipment breakage or equipment failure can resultin irretrievable loss of foreign bodies.

.Air bubbles from escaping gas develop easier in smalljoints than in large joints.

.Foals. yearlings. and ponies might require smallerdiameter (2.7 mm) arthroscopes.

General considerations

The author's G.B.) technique of diagnostic and surgical use ofthe arthroscope in the dorsal aspect of the distal interpha-langeal joint (DIP) was first described in 1990 (Boening et al1990). The arthroscopic technique and long-term results in

Indications

Indications for coffin joint arthroscopy include diagnosticinspection of the dorsal pouch or of the palmar/plantar pouchof the joint, removal of osteochondral fragments or avulsionfragments, removal of osteophytes (Bramlage 1988), syno-vectomy, debridement and joint lavage. The most commonindication in the dorsal distal interphalangeal joint is theremoval of fragments of the extensor process of the distalphalanx (Fig. 11.3).

Diagnostic arthroscopy of the dorsalpouch of the distal interphalangeal joint

Insertion of the arthroscopeThe horse is under general anesthesia in dorsal recumbency.The surgical leg is either passively flexed and loose orextended and supported in a stand. Some authors prefer aloose limb and, therefore, an assistant is needed for jointmanipulation and support. After surgical preparation foraseptic surgery, the operating field is draped with sterileadhesive antibacterial barriers in addition to a largeimpervious arthroscopy drape. The articulation is extendedand an 18- or 16-gauge needle is inserted into the dorsal jointcavity (Fig. 11.4), which is then distended with sterile isotonicpolyionic Ringer's solution.

phalanx (Fig. 11.8). From there the dorsal concave part ofthe articulation of the second phalanx and the convex part ofthe articulation of the third phalanx can be visualized. Byrotation and relocation of the tip of the arthroscope. thelateral and medial rim of the articulation and the attachmentof the joint capsule and the extensor tendon become visible.Hyperflexion. hyperextension. and medial and lateral hoofrotation will expose additional. deeper parts. of the articu-lation. With this approach. even lateral or medial aspects ofthe distal articulation of the middle phalanx will becomevisible. By careful withdrawal and positioning the tip of thearthroscope into a more proximally orientated position. thedorsal joint capsule and the proximal reflection of the jointcapsule can be examined.

The dorsal joint capsule bulges easily with distention anda No. 11 scalpel blade is used to make a 5 mm vertical skinincision about 3 cm proximal to the coronary band and about3 cm lateral or medial of the sagittal midline. This incisioncontinues into the joint cavity. These landmarks assure anoptimal position for the arthroscope -a portal too close to thecoronary band and too far from the sagittal plane createsmajor problems in DIP joint arthroscopy. Misplacement ofportal sites also incurs the risk of hitting a major blood vessel(Fig. 11.5) and the loss of orientation. As in all arthroscopicprocedures. the shorter the distance from skin to joint cavity.the better.

The arthroscopic sleeve is introduced and positioned in thedistal interphalangeal joint by the use of a blunt obturator topenetrate the fibrous joint capsule (Figs 11.6 and 11.7). Oncethe sleeve is in the joint. the obturator is exchanged for thearthroscope. and the camera. light cable. and fluid and gasingress line are attached. The diagnostic arthroscopicevaluation can commence from this position. One author GB)prefers gas distention with carbon dioxide. as he considers itsuperior for all diagnostic and surgical procedures; a parallelfluid distention line is used for postoperative lavage. Handinstruments such as probes. forceps. rongeurs and cannulasare introduced through the instrument portal. This isdetermined by the use of a hypodermic needle. Diagnostic arthroscopy of the

palmar/plantar poucf1 of the distalInterphalangeal jointNormal arthroscoPic anatomy of distal

interphalangeal jointThe dorsal pouch of the distal interphalangeal joint representsabout 30% of the entire joint. The main landmark for thispart of the joint is always the extensor process of the distal

Indications

For the palmar/plantar approach the horse may be positionedin either dorsal or lateral recumbency. Dorsal recumbency

(Boening 1995). The palmar/plantar pouch of the DIP isquite spacious in the axial area, but surgical removal offragments remains challenging. Through contralateral:

instrument portals, only limited mobility of thehand instruments can be achieved.

CD

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Insertion of the arthroscope -palmar/plantaraspectFor inspection of the palmar/plantar aspect of the (

interphalangeal joint. it is preferable to have the horselateral recumbency. For preoperative distention of ian I8-gauge.:. ..Up to 25 ml of sterile saline can be injected.:.- -into the dorsal: " .rpalmar/plantar pouch. which is then used i ' --

landmark to aid in exact positioning of the incision~'I

,.11.,1~:

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distention is palpable immediately axial to ;collateral cartilage. A 5 mm vertical skin incision isdirectly over the lateral or medial aspect ofpalmaro/plantaroproximal pouch. Landmarks for;orientation are the collateral cartilage (keep

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,11/1-artery and nerve (keep axial) and the deep digitaltendon and the digital tendon sheath (keep abaxial).Esmarch bandage and/or a tourniquet can help to I

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A conical obturator within ( .advanced (Figs 11.9 and 11.10) parallel to theplantar rim of the second phalanx. f' .,

of the frog. Introduction of the sheath under j-guidance is useful if available.

Entrance into the joint is marked by flow of fluidthe open stopcocks. Once in the joint cavity, (-replaced by the 300 arthroscope and joint distentionmaintained by either fluid or gas.

distal interphalangeal joint, the limited maneuverabilityoffers a more easy contralateral instrumental approach(Boening et al1990, Mcllwraith, 1990a).

The use of fluoroscopy for anatomic orientation is helpful.Under such visualization, the insertion of the arthroscope,insertion of hand instruments, and the identification of thefragment's side can be achieved. In the palmar/plantar pouchof the coffin joint (see Figs 11.1 and 11.2) fragment removalis the most common indication for arthroscopic surgery(Brommer et al 2001). These fragments are either freefloating and OCD in origin or embedded in the joint capsule orligaments. Lesions that are the result of secondary bonemetaplasia can be detected in these areas. In such cases theirappearance seems to be flattish and generally accompaniedby signs of degenerative joint disease. A further indication forpalmar/plantar coffin joint arthroscopy is debridement of cysticlesions at the proximal rim of the navicular bone (Zierz etal2000). The technique can be combined with cancellous bonegrafts, in which CO2 gas distention of the joint is required

in the coffin joint will be closed after completion ofination and/or surgery' .-, .

Sterile bandaging incorporating the entire hoof isvalue. The risk ofand secondary joint infection is directly correlatedimproper bandaging. If loose bandages expose i'

even loss of the patient from joint infection might result. Thebandages should be changed every second day until primaryhealing of the skin incisions is achieved.

Normal arthroscoPic anatomy -palmarolplantaroproximal aspectThe midsagittal ridge of the dorsal articular border of thenavicular bone is the first structure to identify (Fig. 11.11).

Fig.11.7Diagram of arthroscope position -dorsal pouch of the distal

interphalangeal joint. CD, Common digital extensor tendon.

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The entire proximal border of the navicular bone plus theattachment of the joint capsule to this bone can be examinedby moving the tip of the arthroscope in a palmar or plantardirection. At the medial aspect of the joint and also on thelateral aspect of the joint. parts of the collateral sesamoideanligaments can be identified. These structures are not intra-articular but they are visible through the joint capsule atthese locations. To view these ligaments the tip of the arthro-scope has to be directed distally in between the navicularbone and the palmar/plantar articulation of the secondphalanx. Hyperflexion causes the navicular bone to moveaway from its contact point with the second phalanx and thisexposes more of the distal axial parts of the joint cavity.

extensor process of the distal phalanx. 'Ibe securely embedded in the attachment of the

...,

Their size and outline varies from 2 mm up to 30 mIDdiameter. They can be round with a smooth outline. asosteochondritis dissecans (OCD) fragments. or in ,. --

with traumatic fractures they might appear more iin shape.

A complete set of preoperative radiographs :-important information about the size and location of

--Arthroscopic surgery of the dorsal distalinterphalangeal joint for treatment ofextensor process fragments

Indications

The most common indication for arthroscopy of the dorsaldistal interphalangeal joint is the removal of fragments of the

plantar view are standard; slightly oblique views canhelpful in cases of an abaxial fragment. ( --~-(CT) images may -~

of the damage, and, finally, arthroscopic accessibility.After arthroscopic identification the fragment -

with a periosteal elevator and removed from the joint by

of small cup rongeurs. Most of the fragments.

bit is recommended. In case of

synovitis. The protruding synovial villiment. In such cases the use ofhelps to improve visibility.

process are much more difficult to access (Figs 11.12

mental portal (Vail & McIlwraith 1992) and:might be impossible to remove from the joint at all

Fig. 11.14).

of postoperati~ osteoarthritis. Osteophytes and newformation. and trauma and damage to the coronaryand to the attachment of the common digitaltendon are potential complications after dorsal coffin

arthrotomy.One author (Hertsch 1972) removed'

arthrotomy Ilonger an appropriate optionscopy is the method of choice for all sizes of fragments.

Preoperative considerations

ments are often found on pre-purchase examination. jscopic surgery in such cases, therefore, is prophylactic

an 18-gauge needle is inserted about 3 cm medial to thesagittal line and 3 cm proximal to the coronary band. Asmost fragments are small, the tip and cutting edges of theneedle can be used as a probe and for initial cut down ofminor attachments of the fragment. When the needleposition is judged to be satisfactory, a 5 rom stab incision witha No. 11 scalpel blade is made in the skin and continued intothe joint. It is important to use well designed, strong, andunbreakable hand instruments (Fig. 11.15). In cases ofinstrument failure, pieces may disappear into an inaccessiblearea of the joint cavity.

The fragment is identified and the attachment to theconnecting tissue is severed with a V-shaped periostealelevator. The surgeon then identifies the soft tissue line betweenthe fragment and the remaining coffin bone and carefullyelevates the 4agment from its origin (Fig. 11.16-11.19).

Narrow cup alligator forceps or low profile rongeurs areintroduced into the joint and the fragment securely grasped,rotated (to make sure there are no remaining attachments),and removed from the joint cavity. At completion of theprocedure, the defect created by the fragment is debrided andthe joint cavity is lavaged using a 4.5 mm egress cannula.

In chronic cases, secondary hypertrophic reaction of thesynovial membrane, combined with soft tissue fibrosis, canmake identification and removal of fragments a challenge.In such cases, it is helpful to remove the interfering synoviumby the use of a mechanical synovial resector. In chroniccases, various stages of cartilage damage become visible.Discoloration, fibrillation, and erosion up to full-thicknessloss of cartilage will be in proportion to the duration of theinitial disease. Intraoperative radiographs may be necessaryto ensure that all parts of the fragment are removed.

"cosmetic" in nature. However, we feel that many joints withso-called silent fragments develop secondary lesions, such asproliferative synovitis and articular cartilage damage.

In lame horses, the prognosis for complete recovery is stillgood as long as there are no signs of secondary new boneformation. The earliest signs of secondary osteoarthritis areosteophytes on the dorsal aspect of the middle phalanx andthey are usually most obvious on oblique radiographic views.

Arthroscopic techniqueThe surgical technique for extensor process fragment removalfollows the steps of diagnostic coffin joint arthroscopydescribed earlier in this text. The instrument portal iscarefully selected to permit access to the central articularsurface. To determine the location of the instrument portal.

arthroscopic removal of extensor processPostoperative managementSpecial care is taken with bandaging, keeping in mind thatbandage failure will result in exposure of the surgical incisionand potential contamination with manure. It is importantthat the bandage covers the entire hoof. An elastic. adhesivebandage prevents slippage. Bandages are carefully monitoredand changed until the skin sutures are removed 12 days afterthe procedure. Horses are confined to a stall for a minimum of12 days and then hand walked daily for 15 minutes. Ridingand more intensive training can start 3 to 6 weeks after thesurgery. Antibiotics and phenylbutazone are administeredpostoperatively for a period of 3 days.

component,may develop (Gabel & Bukowieckie 1983).

another choice but incurs the risk of secondaryfailure. The implant at this location is exposed tocyclic loading and can break. The obvious

operative time with less incisional exposure,visibility within the joint, and shortenedperiod.

Problems and complications

The most common problem in dorsal coffin joint arthroscopyis inadequate visualization. Suitable case selection andaccurate placement of both arthroscope and instrumentportals alleviates this problem. Only with optimal placementcan effective triangulation be achieved. The most commonmistakes are having the portals too far lateral or medialand/or to close too the coronary band. If a fragment or partof a fragment becomes loose it might be extremely difficult torelocate. Loose fragments either disappear further distally inthe joint or move into the proximal pouch of the joint. Re-arthroscopy within a few days after the first attempt is anoption if the fragment cannot be found.

Arthroscopic surgery of otherconditions in the ~istaljoint .

Abaxial articular fragments

Other. intra-articular fragments (see Figs 11.12 and 11..including osteochondral chip fractures or '

& McIlwraith 1992, McIlwraith & Goodmanvisibility of imight still be a challenge (Fig. 11.22). Theapproach is routine. .portal site for hand instruments is located eithermedial to the extensor tendon. An 18-gauge

Results

Since the first report in 198reports published. Boening etlame horses that recovered

characterized by significant porosity of the bone,reduction and fixation of the fragment is not {

8 there have only been caseal (1990) described 14 of 16full athletic function after

Periosteal elevators are used to free ligamentous attachmentsand motorized arthroscopic cutting instruments can be usedfor resection of hypertrophic synovial membrane. fibrousbands, and for final cleaning up of the fragment bed. Jointlavage and skin closure follow the surgical procedure. Thesepatients require secure bandaging for 10 days and box rest foranother 3 weeks, followed by hand walking for an additional3 weeks. Visibility and accessibility seem to be the mostdemanding features of these cases.

Fragments in the palmarolplantaroproximalpouch of the distal interphalangeal joint

Osteochondral fragments located in the palmar/plantaraspect (Figs 11.23 and 11.24) of the DIP proximal to thenavicular bone are rare (Brommer et al 2001. Wagner et al

1982). Such fragments could be caused by an avulsionfracture of the middle phalanx or navicular bone. trauma to

the articular cartilage with secondary ossification. or osteo-chondrosis. With arthroscopy of the palmar/plantar

capsule at all or inadvertent intrusion into the navicularbursa or digital tendon sheath. Using fluoroscopic assistance,anatomically correct positioning can be achieved andessential structures in close proximity to each other can beprotected. Injection of fluid into the dorsal aspect of the jointresults in distention of the palmar/plantar pouch, which isthen an important additional landmark to aid in exactpositioning of the arthroscope sheath.

Distal phalanx cysts

Cysts of the central weight bearing surface of the distalphalanx occur infrequently, and have been treated with intra-articular medication and transcortical drilling. Most respondtransiently to medication. and transcortical debridementthrough hoof wall windows has been complicated by recur-rent abscessation and lameness. Intra-articular approachesfor debridement have been described recently in 11 horses(Story & Bramlage 2004). Dorsal arthroscopic approacheswith the distal interphalangeal joint extended and the jointdistracted allow access for cyst debridement (Fig. 11.25).Successful return to work was reported in 10 of the 11 horses,which is a considerable improvement compared to results ofextra-articular and conservative approaches.

proximal pouch of the DIP. the proximal articular margin ofthe navicular bone can be visually assessed. The palmaraspect of the distal articular margin of the middle phalanx.the collateral sesamoidean ligaments of the distal sesamoidbone. and the joint capsule are further structures in thevisual field. The distal margin of the navicular bone and thearticulation between the middle and distal phalanx cannot bevisualized (Vacek et al 1992). Arthroscopy in the palmar/plantar pouch of the joint can be accompanied by problemssuch as hemarthrosis and iatrogenic damage to articularcartilage. Most errors are related to incorrect placement ofthe arthroscope sheath. resulting in failure to enter the joint

Proximal navicular cysts

Surgical treatment of cyst-like defects of the proximal rim orbody of the navicular bone was reported by Zierz et al (2000).Referring to a technique published by Wolter & Ratusinski

({{~:1):~

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II~: I II ,\(1985), they drilled out bone cysts in the navicular bone of 5horses. The arthroscopic approach was according to Vacek et al(1992). After the insertion and positioning of the arthroscope,they created a contralateral portal for a 4.5 mm drill andsleeve. The cyst was identified and subsequently drilledthrough diagonally. As soon as the drill reached the cyst,there was a significant loss in drill resistance. All 5 horseswere Warmbloods from 6 to 16 years of age (3 show jumpers,1 dressage, and 1 pleasure horse). Horse 1 was re-operated9 months after the first surgery; 7 months after the secondsurgery there was significant progress in bone remodeling atthe cyst site. Horse 2 was considered to be completely healedand was back in work 5 months after the surgery. Horse 3became sound and went back into training after 12 weeks.There are no reports on the outcome of horses 4 and 5. Thisreport is contrary to experiences with drilling cysts in themedial femoral condyle, where progression of cyst enlarge-ment after drilling has been observed.

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Arthroscopy of the dorsal pouch of theproximal interphalangeal joint

Limited space in the dorsal pouch makes accurate location ofarthroscopic portals critical. The limb should be fixed inmaximal extension and placement of the obturator andarthroscopic cannula into the joint is facilitated by distendingthe joint with fluid from the palmar/plantar aspect(Fig. 11.26). The cannula should be inserted along the dorsalproximal margin of the middle phalanx to the center of thejoint.

Ideally. the arthroscopic portal is in the distal aspects ofthe dorsal pouch (Fig. 11.27). Placement too far proximallylimits

the ability to view the entire dorsal joint space. Optimalplacement results in sufficient space in the joint to allowfragments

to be removed safely. Small alligator-cup, or lowprofile Ferris-Smith rongeurs are recommended because of

Reports of arthroscopy of the proximal interphalangeal jointare rare in the equine veterinary literature (Mcllwraith1990b, Schneider et al1994). One report describes a singlecase and the second a group of 3 Standardbred racehorseswhere osteochondral fragments were removed from thedorsal aspect of the proximal interphalangeal joint. In thelatter study, after arthroscopic removal of the fragments fromthe dorsal proximal interphalangeal joint, all 3 horsesreturned

to training and raced successfully.

Fig. 11.27Diagram of arthroscope position in the dorsal pouch of theproximal interphalange359al joint. CD, Common digitalextensor tendon.

space limitation. The intra-articular anatomy of the dorsalproximal interphalangeal joint is simple and consists of thedorsal distal articular cartilage of the proximal phalanx aswell as the dorsal rim of the middle phalanx and joint capsuleattachments (Fig. 11.28). This dorsal proximal rim of themiddle phalanx is the usual location for osteochondral chipfragments (Fig. 11.29 and 11.30). Fragments found at thislocation could possibly result from osteochondrosis. Thesefragments usually cause synovitis. which results in localswelling of the proximal interphalangeal joint and associatedlameness. Intra-articular anesthesia is essential for properdiagnosis. To establish the exact location of the operativesite for fragment removal, at least four preoperativeradiographs are required. Size and anatomic location of thefragment may be identified with a dorsopalmar/plantar, a

latero-medial, and two oblique views usingradiographic films.

Following removal of fragments, ---' "---

padded bandaging of the surgical site for 1 0 daysconfinement for 2 weeks post-surgery.hand-walked for another 2 weeks. The,allowed to train for a period of 6-8 weeks after surgery.

Arthroscopy of thep<?uch of the proximalJoint

So far there are no reports found on arthroscopy ofpalmar/plantar pouch of '

in the literature. Although fragments occur in the palmar/plantar aspect of the pastern, it has been suggested that thecapsular and ligamentous attachments limit entry into thecentral part of the joint (McIlwraith 1990).

Fragments located in the axial palmar/plantar pouchare found occasionally on pre-purchase examination(Fig. 11.31). These cases often show only Grade 1 lamenessand insignificant clinical signs like joint distention andpositive flexion test; some are without any lameness.

Fragments. that are located abaxial and which originatefrom the proximal lateral or medial rim of the middle

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2 cm proximal to the margin of the distal condyle ofproximal phalanx (Fig. 11.26), close to theplantar margin, the obturator and cannulathe palmar/plantar pouch aiming axially (Fig. 11.3311.34). The axial palmar/plantar pouch is quite(Fig. 11.35), r

The instrument portal can be ipsilateral or

orientation of portals and fragment identification.After fragment removal, the joint is debrided and I

and the skin is closed. The postoperative training

interphalangeal joint arthroscopy. One author GB)phalanx, remain cases for mini-arthrotomy as they cannot beaccessed arthroscopically (Fig. 11.32). The pathogenesis ofthe avulsed abaxial fragments is traumatic; these fragmentswill create significant lameness in the acute stage.

For surgery of axial palmar/plantar fragments in theproxinlal interphalangeal joint, one of the authors OR) prefersthe horse in lateral recumbency, while the remaining authorsprefer dorsal recumbency. The joint is pre-distended withpolyionic Ringer's solution by the use of a 16-gauge hypo-dermic needle. The landmarks for palmar/plantar injectionare about 2-3 cm proxinlal to the palpable distal condyle ofthe proxinlal phalanx. After making a 5 mm skin incision

of the proximal interphalangeal joint on 5 occasions:European Warmblood horses and 1 pony: Three ofcases showed Grade I lameness which could be, after

joint. All fragments. ranging from 4 to 12 mm

had failed previous pre-purchase examinations. Only

}.1

after surgery. In this case the fragment could be visualizedarthroscopically in between the distal condyles of Iproximal phalanx. but was inaccessible.

References

the 1st Advanced Arthroscopic Surgery Course, I

University,1988.Boening KJ. Contact-Arthro-Microscopy and synovial

-

Annual ECVS Scientific Meeting, Konstanz, 1995: 71-72.--

EquinePract 1990; 311-317.Brommer H. Rijkenhuizen ABM. van den Belt AIM. Keg

Arthroscopic removal of an osteochondral fragment atpalmaroproximal aspect of the distal interphalangeal.Equine Vet Educ 2001; 13(6): 294-297.

Gabel AA. Bukowieckie CF. Fractures of the phalanges. Vet'North Am Large Anim Pract 1983; 5: 233-260.Hertsch B. Diagnosis and treatment of pedal bone fractures. ~

Tieriirztl Wochenschr 1972; 79(21): 524-532.Mcllwraith CWo Other uses for arthroscopy in the horse.

horse. Philadelphia: Lea & Febiger 1990a: 219.McIlwraith CWo Other uses for arthroscopy in the

horse. Philadelphia: Lea & Febiger; 1990b: 220.Mcllwraith CWo Goodman NL. Conditions of i

of osteochondraljoint of the pelvic limbs in three horses. JAVMA79-82.

Story MR. Bramlage LR. Arthroscopic debridement ofbone cysts in the distal phalanx of 11 horses :--EquineVetJ2004; 36: 356-360.

articular anatomyaspects of distal interphalangeal joints. Vet Surg 1992;257-260.

Vail TB. McIlwraith CWo Arthroscopic removal of ' C

fragment from the middle phalanx of a horse. ~269-272.

Wagner PC. Modransky PD. Gavin PRo Grant BD...-

Equine Pract 1982; 4: 9-15.Wolter D. Ratusinski C. Das extraartikuliire. I

1985; 88:425-431.ZieI"l J. Schad D. Giersemehl K. Chirurgische Moglichkeiten

Versorgung von Strahlbeinzysten sowie StrukturdefektenStrahlbein. pferdeheilkunde 2000; 16:171-176.

out of this group of 5 horses had a problem in the front limb;all the others were affected in a hind limb. The horse with thefragment in the front leg was not lame before surgery and didnot show lameness after fragment removal. All horses withaffected hind limbs became sound and could go back intotraining; 1 of the horses with a hind limb fragment exhibitedno evidence of pre-surgical lameness nor did it develop anysigns of lameness post-surgically. Only the pony stayed lame

CHAPTER

Tenoscopy of the DigitalFlexor Tendon Sheath

digital flexor tendon sheath (Ragland 1968. Dik et a11995.Fortier et al1999. All are exquisitely sensitive. Surgical treat-ment of these complex cases is appropriate to debride theprimary tendon defect and stop the cycle of annular ligamentconstriction and ongoing sheath irritation (Fortier et al1999).

Introduction

The primary indication for tenoscopy of the digital flexortendon sheath is assessment and treatment of the variousmanifestations of chronic, proliferative, so-called "complextenosynovitis" of this sheath. Chronic tenosynovitis is arelatively common problem of the digital flexor tendon sheath,particularly in the hind limbs. Most mild and moderate formsof tenosynovitis cause only low-grade lameness and 'can bemanaged medically. More severe tenosynovitis cases, andthose chronic cases that have disruption of the tendonsheath, the various mesotenons. the annular ligament, or theflexor tendons themselves, may result in a more profound andself-perpetuating cycle of increasing tendon sheath fibrosisand annular ligament thickening (Fortier et al1999). Teno-synovial masses and adhesions can develop as a consequence(Watrous et al 1987). These latter types of complextenosynovitis not only require surgical intervention but alsogenerally have a reduced prognosis for good cosmetic out-come and return to complete soundness (Fortier et al1999,Wilderjans et al 2003). The duration of symptoms seemsparticularly relevant to the final outcome of these cases.

Preoperative assessment

Lameness originating from the digital flexor tendon sheath isconfirmed by intrathecal anesthesia, and should be followedby a thorough ultrasonographic assessment. Particularattention should focus on the extent of tendonitis of thesuperficial digital flexor tendon (SDFT) and the deep digitalflexor tendon (DDFT) , since they profoundly affect theprognosis and the decision for surgery (Barr et al 1995).Additionally, ultrasonographic evaluation determines thethickness of the tendon sheath wall and palmar annularligament, and defines the number, and lateral or medial attach-ment, of tenosynovial masses that need to be addressed at thetime of surgery (Stanek & Edinger 1990, Dik et al 1991,Redding 1991). Central core lesions of the flexor tendons canbe treated by injection or stab incision at the time of surgicalsection of the annular ligament. Linear clefts within theDDFT and occasionally the SDFT present special problems inrepair, with most requiring debridement, and some requiringsuture repair (Wright & McMahon 1999). In the authors'experience ultrasonographic examination is not sensitive indetecting linear clefts in the tendon structure. Any ultra-sonographic suggestion of echolucencies within the surfaceone-third of the flexor tendons is highly suspicious, and thisregion should b'~ carefully assessed during endoscopic explo-ration. Additionally, adhesions and soft tissue masses withinthe tendon sheath, as well as between the SDFT and DDFT,need to be removed. Presurgical preparation and drapingmust provide access to both lateral and medial portions of thedigital flexor tendon sheath, to allow instrument access tothese tissues for removal or sectioning.

Pathogenesis

Acute tenosynovitis can result from tearing of various portionsof the digital flexor tendon sheath, the mesotenons, or lineartears in the flexor tendons within the sheath. Recalcitranttenosynovitis and secondary constriction due to the palmar/plantar annular ligament can then follow acute tenosynovitis(Dik et al19 9 5). Progressive fibrous thickening of the sheathand the intimately attached annular ligament can compressand restrict the free movement of the flexor tendons throughthe fetlock canal (Adams 1974, Gerring & Webbon 1984,Verschooten & Picavet 1986, 1988). The consequencesinclude turgid fluid accumulation within the tendon sheath.enlarging tenosynovial masses along the abaxial portions ofthe flexor tendons, particularly in the proximal portion of thedigital flexor tendon sheath. and adhesions spanning fromthe tendons to the dorsal and abaxial parietal layers of the

Surgical anatomy

The digital flexor tendon sheath consists of a parietal andvisceral layer that provide the inner lining of the sheath andthe surface layer of the enclosed tendons, respectively. Theintimal layer is several cell layers thick, and is supported by

Cut annular ligament

dense subintimal and sheath fibrous layers (Hago et aI1990).The digital flexor tendon sheath extends from the junction ofdistal and middle thirds of the third metacarpus/metatarsusto the level of the middle phalanx and navicular bone(Fig. 12.1). The sheath encloses the SDFT and DDFT, both ofwhich have mesotenon attachments to the tendon sheath.

The most robust meso tenon extends from the palmar midlineof the SDFT to the adjacent tendon sheath (Figs 12.2 and12.3). Short thick meso tenons also extend from the proximo-medial and proximolateral margins of the DDFT. The proximalportion of the DDFT is encircled by a complete but thin sleeveof the SDFTknown as themanicaflexoria (see Figs 12.1-12.3),

which ensures alignment of the tendons during their passagearound the fetlock. The digital flexor tendon sheath has itsproximal reflection and attachment to the full circumferenceof both the SDFT and DDFT, which forms the proximalendpoint of the sheath cavity. In the distal portions of the

digital flexor tendon sheath, the DDFT has several dorsal anda single palmar/plantar meso tenon attachment (see Fig. 12.1,inset). There is also a small encircling component (the digitalmanica) of the SDFT (see Fig. 12.1, inset), which stabilizesthe SDFT against the DDFT during the final path toward

Proximal phalanx4 ~..~ ,-' ,~~.J"~("

.,:,r"';' ~'".~ 'r;,"', ~.~~.f..~i~

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tendon insertion (Nixon 1990c, Redding 1991 1993). TheSDFT can be seen to bifurcate and exit the digital flexor tendonsheath in the region of the distal portion of the proximalphalanx (Fig. 12.4). Vascular supply to the flexor tendons isderived through the mesotenon and digital sheath reflections.Synovial fluid from the tendon sheath has a similar com-position to that from joints, with slightly reduced hyaluronicacid content (Malark et aI1991).

gently in a proximodorsal direction

dorsal recesses of the sheath (see Fig. 12.5). High

wall of a fibrosed tendon:the initial phases of digital flexor tendon sheathallowing time for the tissues to expand andhemorrhage and synovial fluid to 1 ' ,

through several needles.

should involve entry outside the manic a flexoria,many of the larger tendon sheath masses develop (Fig.Tenoscopic techniques

Diagnostic tenoscopyThe standard approach to the digital flexor tendon sheathuses a skin entry portal for the arthroscope on the palmaro/plantarolateral aspect of the sheath between the annularligament and proximal digital annular ligament (Fig. 12.5).Distention of the tendon sheath defines an outpouching atthis site. A skin incision is made slightly palmar/plantar tothe center of this prominent outpouching, to allow thearthroscope to be directed proximally through the fetlockcanal, and then to be redirected for examination of the distaltendon sheath region (see Fig. 12.5). Entry of the arthroscopesleeve and conical obturator needs to be performed with care,since the flexor tendons in chronic cases have fragile epitenalsurface layers. and iatrogenic damage is a possibility. The skinincision and entry portal through the fibrotic tendon sheathneed to be slightly larger than normal, so thatthe arthroscopesleeve and obturator enter easily. Once the sleeve andobturator have entered the digital sheath, they are pushed

canal and inserted beneath the manicathe proximal DDFT. Linear clefts ifound at this~vel, which may correspond to ,stricted region of the fetlock canal when the limb

SDFT, paying particular attention to adhesions andmasses directly between the flexor tendons (Fig. 12. '; -

the arthroscope is withdrawn from Iredirected palmar/plantar to the SDFT, where themesotenon attachment is evident (see Fig. 12.7).

sheath is restricted. In such cases, examination canimproved by severing the annular ]phases of the surgical procedure, (tendon sheath masses and other adhesions. The

Fig. 12.6Tenoscopic view of the fetlock canal region with the arthroscopeinserted distal to the annular ligament and looking proximally (asin Fig. 12.5). The lateral sesamoid (Ses). annular ligament (AL).manica flexoria (MF) of the SDFT (S). and the DDFT (D) areevident. Ses

~

instrument entry is made in the dorsolateral region of theproxinlal cul-de-sac of the digital flexor tendon sheath (seeFig. 12.5). This is defined by needle entry followed by scalpelincision. The entry to the digital flexor tendon sheath shouldbe palmar to the neurovascular bundle, to avoid damage tothese structures. Preoperative placement of a tourniquet isroutine and is a useful means to limit hemorrhage from skinentries, adhesion and mass removal sites, and the annularligament division. particularly if this is done early in the

surgical examination and treatment of complex cases.tourniquet is ]ment of a septic digital flexor tendon sheath.lateral skin entry then provides

motorized resectors. As resection of

layer of 1_- ---~--- ~--- medial entry can be made to the proximal portion of 1

J '

~lade, Dyonics -Smith & Nephew, Andover, MA), with relatively\Tide cutting apertures and active suction, allow entry of theissue

to the cutting blade. Biopsy punch rongeurs (Dyovac;.2, Dyonics -Smith & Nephew), biopsy cutting forceps,etractable

blades, and arthroscopic scissors can all be usefulDr removal of masses (Fig. 12.12). The biopsy punch rongeurs useful for removal of adhesions; however, motorized'esectors

provide more efficient soft tissue mass removal.Nith large masses, a second instrument portal may be required0 provide tension on the mass while it is severed at its basemd

removed using hand instruments. Access to the region)etween the DDFT and SDFT will require an instrument entry;hrough the proximal portion of the manic a flexoria of the)DFT.

The original skin portal in the dorsal lateral surface of:he proximal portion of the digital flexor tendon sheath canJe

used; however, a separate incision needs to be developedthrough the surface of the manica flexoria to allow instru-ments

to enter between the DDFT and SDFT. The authorsl1ave not recognized complications associated with these

additional perforations. Bleeding from the sheath andepitenon surface of the tendons after mass resection can beprofuse, and a tourniquet becomes more important as diseasechronicity increases. In most circumstances, the palmar/plantar annular ligament is transected after removal oftendon sheath masses. However, if movement through thefetlock canal is restricted, the annular ligament should bedivided

early.

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annular ligamentThe

only effective treatment for genuine palmar/plantarannular ligament constriction is surgical division. A simpleannular ligament transection can be accomplished withoutthe

need for tenoscopy, but in many cases constriction is partof a complex tenosynovitis syndrome which requiresresection of tissues in addition to the annular ligament.Tenoscopically assisted annular ligament transection can beaccomplished free hand using a variety of right-angledblades, or preferably using a slotted cannula (Dyonics -Smith& Nephew, Andover, MA) for better control of the blade(Fig. 12.13). This latter technique was developed for carpaltunnel surgery in man (Chow 1989. 1999). and has beenadapted without change to the instrumentation for annularligament release in horses (Nixon et al1993). The advantagesof tenoscopic annular ligament release include the precisionof the cut, the safety of identifying and avoiding vital structuressuch as the manica flexoria and flexor tendons, and theextensive dissection that can be performed through limitedentry wounds. which provides better wound healing withless risk of dehiscence and earlier postoperative exercise(Nixon et al 1993). Placement of the slotted cannula iscritical to facilitate insertion of the arthroscope and 900angled blade. The proximal entry portal should be dorsal inthe digital flexor tendon sheath and the distal exit portalplantar/palmar. to allow the arthroscope or blades to clear

flexor Ienaun ~Il~ltLIl LU ItUUW ~llLLY VI lla11U 111"" U111"1'." =1"motorized resectors for direct access to synovial masses andadhesions

(Fig. 12.8).Redirection of the arthroscope into the distal regions ofthe digital flexor tendon sheath permits evaluation of bothsurfaces

of the DDFT and the dorsal surface of the SDFT, thedigital manica, and the mesotenon (vinculae) (Fig. 12.9).Ultimately, the arthroscope can be inserted to the distal limitsof the digital flexor tendon sheath. Generally, proliferativemasses

and adhesions are less prevalent in the distal regionsof the sheath.

Reversal of the instrument and arthroscope portals allowsexamination of the digital flexor tendon sheath using aproximal approach (Fig. 12.10). Instruments can be insertedthrough the distal skin portal, allowing further motorizedresection of adhesions and masses associated with theflexor tendons and tendon sheath distal to the level of

the fetlock.

.eno~~op'~ mu~~ "~'"UYU"UU"~~"'" ..u..~~'"..v..

Open tendon surgery for removal of tenosynovial masses andadhesions delays initiation of exercise postoperatively andpredisposes to adhesion reformation (Watrous et al 1987,Nixon 1990b). Tenoscopic examination of the digital flexortendon sheath is preferred, as the minimally invasive approachprovides complete access to most of the sheath contents,permits multiple mass removal, and allows early return towalking in the convalescent period (Nixon 1990c). Largetenosynovial masses can be challenging to remove, andcomplete assessment can be difficult until some of the tissueis resected. Preoperative ultrasonography is used to targetand develop a plan for mass removal (Fig. 12.11). Straight

(Fig. 12.16). Complete division is verified by external palpa-tion of the blade tip beneath the skin, transillumination oflight from the arthroscope through the skin, and direct visualevidence of a lack of remaining ligament fibers along the pathof the transection. Hemorrhage is flushed from the cannulaand tendon sheath, the cannula is removed. and the skinincisions sutured if no further procedures are required. Inmany cases the arthroscope is reinserted. the annularligament desmotomy inspected. and further exploration andsurgical procedures performed. The increased maneuver-ability of the arthroscope within the digital flexor tendonsheath provides a more complete assessment of the adequacyof adhesion and mass removal.

Several single portal carpal tunnel release devices havebeen developed for use in man (Arthrex. Naples, FL; Linvatec,Largo, FL). Both work for release of the annular ligament inhorses. However, it is rare not to require a proximal and distalentry for other digital flexor tendon sheath procedures, so asingle entry portal system has less utility in the horse.

the heel-bulbs (Fig. 12.14). Interference of the heel-bulb withthe arthroscope and video camera can be frustrating,particularly in breeds such as Cobbs.

The cannula with obturator in place is inserted fromproximal to distal using arthroscopic visualization (seeFig. 12.14). The insertion path must be external to themanica flexoria, or this ring of the SDFT will be divided alongwith the annular ligament. As the slotted cannula and itsribbed obturator near the distal portal. the tip of thearthroscope is retracted 5 mm into its sleeve, to create adocking portal for the obturator of the slotted cannula(Fig. 12.15). This is then advanced, pushing the arthroscopeand sleeve out of the tendon sheath and allowing the slottedcannula to exit the arthroscopic skin portal. The ribbedobturator is then removed from the slotted cannula, and theunsheathed arthroscope inserted to view and confirmpositioning with respect to the flexor tendons, the sesamoidsurface, and the palmar/plantar annular ligament. The slotin the cannula is then oriented to open directly toward theannular ligament (Fig. 12.14D), before the 900 angled bladeis inserted and drawn across the fibers of the annularligament to sever the full thickness of the ligament

Tendon linear clefts

An increasingly recognized syndrome involves longitudinalclefts in the DDFT and less frequently in the SDFT. The linearclefts can penetrate a variable distance into the substance ofthe tendon, and in some instances have been extensive. Thetreatment of choice is tenoscopic debridement (Fig. 12.17),which has proved superior to suture repair following opensurgical approaches (Wright & McMahon 1999, Nixon2002a). Length of tears in the DDFT can extend from 4 to10 cm, and frequently involve the DDFT from the level of midproximal phalanx to extend beyond the level of the apex ofthe proximal sesamoid bones. The depth of linear cleft variesfrom penetration to the center of the DDFT (see Fig. 12.17),to more superficial fiber erosion. Trimming of exposed tendonfiber can be accomplished using a combination of biopsypunch rongeurs (Dyovac 5.2), and motorized resectors withboth side and forward aperture, which are also effective intrimming down epitenal and tendon fiber damage. The aimshould be a relatively smooth tendon surface. Access to theregion between the DDFT and SDFT may also be required totrim linear clefts in the DDFT that extend proximal to thesesamoid,(bones, and this needs an entry through theproximal portion of the manica flexoria for instrumentation,as described earlier.

In some cases there may be tearing of the manica flexoria.This may result from ongoing pressure within the fetlockcanal associated with constriction by the palmar/plantarannular ligament, or may arise as primary lesions. Dependingon the extent of the tear, the edges of the cleft can bedebrided, or the manica resected in toto using arthroscopicscissors, knives or motorized resectors (Fig. 12.18). Noattempt at suture repair has been used. Other pathologicconditions can develop associated with chronic constrictionof the annular ligament, including separation of the palmarmesotenon of the SDFT. These areas can be trimmed, and anysecondary adhesions resected. The aim of digital flexortendon sheath adhesion removal should be free motion of the

flexor tendons within the digital flexor tendon sheath.Alternating the arthroscope entry from the distal to theproximal portals is necessary to allow complete assessment ofthe adequacy of the surgical procedures. Tears of theproximal mesotenon of the DDFT and of the digital manicahave also been encountered by one of the authors (I.M. W.).

Postoperative care

~

injection of NaHA is recommended 2Injection of the digital flexor tendon sheath is

Sodium hyaluronan (NaHA; 20-40 mg) is frequently injectedinto the tendon sheath at the time of wound closure.Research in horses and smaller experimental animals indicatesNaHA reduces the formation and reformation of tendonadhesions in the sheath area and enhances intrinsic tendonhealing (Weiss et al1986, Amiel et al1989, Gaughan et al.1991, Moro-oka et al 2000). Additionally, intrathecal localanesthetic installation provides good postoperative paincontrol. The use of long-acting anesthetic agents such asbupivacaine provides 4-6 hours of postoperative analgesia. Afirm bandage is also applied, not only to provide a sterileenvironment but also to add counterpressure that providesadditional comfort to the operated limb. The bandage isusually maintained for 3-4 weeks after surgery.

Antibiotics such as potassium or procaine penicillin arecommenced prior to surgery and continued for 1 or 2 dayspostoperatively. Surgery around the bulb of the heel and thedistal portion of the digital sheath can be difficult to establishand maintain a sterile field, particularly around the ergot,and antimicrobial drugs are a useful precaution. Longer-termpain control is provided with nonsteroidal anti-inflammatoryagents such as phenylbutazone (4.4 mg/kg orally), which isusually administered for 7-10 days after surgery to minimizetissue inflammation and swelling.

Hand walking for increasing periods commences 2-3 daysafter surgery: Long periods of walking exercise are particularlyhelpful if tendon adhesions were present at surgery. Acompromise between incisional healing and the beneficialaffects of early exercise is usually reached on a case-by-casebasis. Use of mechanical walkers, swimming, and passive

intravenous NaHA (Legend, Bayer Corp, AnimalShawnee Mission, KS) may also be useful.

Return to work'secondary tendonitis, which frequently delays returnexercise for 6-12 months.

ultrasonographic examination is useful to evaluate

Results and prognosis

Endoscopic mass removal and annular ligament division in25 horses followed for 1-7 years revealed a normal cosmeticoutcome in 10 horses, and an improved cosmetic outcome in12 of 22 horses (Fortier et alI999). Lameness was eliminatedin 18 horses (72%) and improved in another 4 horses, while3 horses remained lame. The poorest response was evident in2 horses with concurrent tendonitis in the region of thefetlock canal. The cosmetic outcome was inversely related topreoperative duration of clinical signs and the severity ofsynovial masses. Additionally, a longer history of symptomsled to a thicker annular ligament on preoperative ultrasono-graphy, which was frequently later confirmed at surgery. Theresults following debridement of linear tears in the DDFT

response of the flexor tendons. particularly where lineartendon tears were trimmed or core lesions were injected withgrowth factors or NaHA at the time of palmar/plantarannular ligament transection.

Tenoscopy of the CarpalSheath

have also been reasonably good (Wright & McMahon 1999,Wilderjans et aI2003).

Simple constrictive syndromes due to a wound, desmitis ofthe palmar/plantar annular ligament, or chronic fibrosingsynovitis of the tendon sheath have a good prognosis forreturn to work after annular ligament transection. Theoutlook is guarded where extensive tendon adhesions areresected, as these cases often have residual obliteration of thetendon sheath cavity with tendon tie-down in the proximaland distal limits of the sheath. A better prognosis can beafforded by an aggressive tenoscopic dissection to free thetendons within the tendon sheath.

Introduction

The carpal sheath has been used for many years to refer towhat is now listed in Nomina Anatomica as the commoncarpal sheath of the digital flexor tendons. Throughout thischapter, we refer to this structure as the "carpal sheath" forthe sake of brevity and reader familiarity. Additionally, other

artery and nerve (Fig. 12.20), which can be compressed incarpal canal syndromes. These are rarely viewed duringroutine carpal sheath tenoscopy because the approach isgenerally from the lateral aspect. The SDFT and DDFT areclosely intertwined during their passage through the carpalsheath, and have a common and extensive mesotenon thatexits from the caudomedial aspect of the tendons andattaches to the caudal aspect of the carpal sheath (seeFig. 12.20). This effectively prevents complete examination ofthe carpal sheath using lateral surgical approaches. Otherimportant neurovascular structures that lay outside of thecarpal sheath (see Fig. 12.18), are relevant in carpal canalrelease (Textor et al 2003), and should be avoided in thetenoscopic dissection. The substance of the carpal flexorretinaculum forming the carpal canal and the distal extent ofthe proximal check ligament can be seen intruding on themedial wall of the carpal sheath in the center and proximalregions, respectively (see Fig. 12.19). Vascular support for theSDFT and DDFT is provided through the mesotenon attach-ment, the proximal and distal carpal sheath reflections to thetendons, the radial head of the DDFT, the proximal checkligament attachment to the SDFT, and the entry of vesselsthrough the myotendinous junctions. The carpal sheath fluidhas a similar composition to digital flexor tendon sheathfluid. The carpal sheath becomes considerably reduced indiameter distal to the carpal canal (Fig. 12.21), which limitsthe mobility of instruments during tenoscopic examination,despite the fact the mesotenon is thinner in the distal recess ofthe sheath.

terms occasionally used to indicate the carpal sheath include"carpal flexor tendon sheath" and "carpal canal". The carpalcanal will be used to describe that subcomponent of thecarpal sheath bound by the carpal flexor retinaculum,spanning from the accessory carpal bone to the carpal

ligament.Carpal sheath conditions that result in chronic and often

insidious lameness have been increasingly recognized andexamined by exploratory endoscopy (McIlwraith 2002a,Textor et al 2003, Nixon et al 2004). Many of the clinicalcomponents of carpal sheath/carpal canal lameness may beinterrelated. Radial osteochondroma, radial physeal exostoses,tendonitis or myotendonitis of the proximal portion of thedigital flexors, and idiopathic carpal tunnel syndromes mayall result in lameness and/or sheath distention. These con-ditions frequently have little to differentiate them based ontheir clinical appearance. Endoscopic examination is usefulfor assessment and confirmation of the diagnosis of many ofthese syndromes, and can then be followed by definitiverepair. Arthroscopic approaches to the carpal sheath havebeen described (Cauvin et a11997, Southwood et alI998).Removal of radial osteochondroma under arthroscopicvisualization is simple and effective, and eliminates the deepdissection necessary with open approaches (Squire et al1992,Southwood et al1997, ter Braake & Rijkenhuizen 2001).Additionally, many horses have caudally protruding bonyexostoses associated with the closed distal physis of the radius(Nixon et al 2004). These exostoses are considered to resultfrom previous physitis and when centrally placed canpenetrate the carpal sheath and excoriate the DDFT (Nixon et al2004). Idiopathic carpal canal syndrome can arise fromdamage to the carpal retinaculum, carpal sheath, myo-tendinous junction of the flexor tendons, and fracture of theaccessory carpal bone. Tenoscopic division of the carpalretinaculum can be used to open the carpal canal and releasepressure on the digital flexor tendons (Textor et al2003). Thisreduces the risk of complications associated with opensurgery, including persistent swelling, seroma formation,wound dehiscence and fistula formation.

Tenoscopic techniques

Introduction

The role of radiographically evident bony exostoses andosteochondromas in causing damage to the DDFT and carpalsheath effusion are well described. and tenoscopic removalhas been curative (Squire et a11992. Southwood et al1997,Mcllwraith 2002a, Nixon et al2004). Careful ultrasonographicexamination of the carpal sheath has also identified softtissue lesions within the tendons or carpal sheath. and providesbetter preoperative information for planning the tenoscopicaccess. Casestwith carpal sheath effusion but without anobvious radiologic or ultrasonographic cause are frequentlytreated initially with a combination of intrathecal NaHA andcorticosteroids. If lameness and/or distention persists,diagnostic tenoscopic examination is warranted.

Surgical anatomy

The carpal sheath is a voluminous synovial cavity thatextends from the level of the lower middle third of the radiusto the upper middle third of the metacarpus. It envelops theSDFT and DDFT and their myotendinous junctions duringpassage through the carpal canal. Functionally, the carpalsheath provides protection and lubrication. and minormetabolic support. to both tendons as they traverse the carpalcanal. The parietal and visceral surfaces of the carpal sheathare morphologically similar to the digital flexor tendonsheath. The carpal sheath is more spacious proximal to thelevel of the accessory carpal bone. where it contains bothSDFT and DDFT and the radial head of the DDF, coursingfrom the caudal aspect of the radius to its aponeurosis on theDDFT (Fig. 12.19). The medial side of the SDFT within thecarpal sheath also has an intimately attached medial palmar

Diagnostic arthroscopy of the carpal sheathThe authors use variations of the standard proximolateralapproach to the carpal sheath as described by Southwood et al(1998). This technique allows evaluation of the entireproximal portion of the carpal sheath, including the carpalcanal region, but provides limited access to the metacarpalregion of the sheath. Insertion of the arthroscope into thedistal region of the carpal sheath improves examination ofthis area (Cauvin et aI1997).

.

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extensor tendon \

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middle carpaljoint

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ligaments

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carpal sheath immediately cranial to the radial head of theDDFT, but can be more clearly defined by using an instrumentto probe for the intrusion of the ligament into the sheath (see

Fig. 12.23).The arthroscope can then be redirected to more caudal

regions of the carpal sheath, examining the caudal surface ofthe DDFT and a small portion of the SDFT (see Fig. 12.23).The arthroscope can be inserted from the lateral to medialdirection to assess these areas of the SDFT and can beinserted a small distance between the SDFT and DDFT beforeencountering the common mesotenon joining the DDFT andSDFT.

Further examination of the craniomedial depths of thecarpal sheath reveals the transversely oriented fibers of thecarpal flexor retinaculum, forming the medial boundary tothe carpal canal (Fig. 12-24). The proximal and distal limitsof the retinaculum are not as distinct as the intrusion formedby the proximal check ligament. The proximal border of theretinaculum can be recognized only by the adjacent caudalprotuberan~ of the physeal scar of the radius. The distalborder of the retinaculum can be determined by digitalpressure over the caudomedial portion of the carpal sheath,which can easily be indented only beyond this distal margin.The distal regions of the carpal sheath can be examinedbeyond the level of the carpometacarpal joint, but mobilitydistal to this level is restricted. Examination of the most distalregions of the carpal sheath can be performed by insertingthe arthroscope through the palmarolateral surface of thecarpal sheath in the proximal metacarpus (Cauvin et al1997), and viewing proximally. This can be difficult with thehorse in dorsal recumbency, but the limb should be draped toallow this portal if needed. The arthroscope portal can also bemade in the palmaromedial surface of the sheath at this levelbut, with the horse in dorsal recumbency, manipulating thearthroscope becomes even more difficult.

Surgery can be performed with the horse in dorsalrecumbency, or in lateral recumbency with the affected limbuppermost. Dorsal recumbency is generally preferred by theauthors. It has obvious advantages for bilateral evaluationand significantly reduces intraoperative hemorrhage. Lateralrecumbency facilitates tenoscopy through the distal (meta-carpal) portal and some surgeons find the operating positionto be more comfortable. In both situations, the carpus ispositioned in slight (approximately 15-20°) flexion. Thecarpal sheath is distended with 50-60 ml of lactated Ringer'ssolution and the arthroscope entry portal is made laterally,6-8 cm proximal to the remnant of the radial physis. Thisallows examination of the carpal sheath, while leaving theregion between the arthroscope entry and the distal physis ofthe radius available for instrument entry (Fig. 12.22).

Initial examination from the lateral approach revealsthe caudal aspect of the radius, and the lateral portion of theDDFT, which at this level obscures most of the SDFT(Fig. 12.23). The SDFT can be examined later by rolling theDDFT with a probe, but this exposes only small portions ofthe tendon; complete examination of the SDFT is difficultusing the lateral approach. The common mesotenon forthe SDFT and DDFT attaches to the caudolateral aspect of thecarpal sheath, and effectively prevents examination of theSDFT over its caudal and medial surfaces. In the more distalregions of the carpal sheath, the SDFT emerges, althoughbetter examination of this tendon is provided through apalmarolateral portal 4-6 cm distal to the accessory carpalbone (Cauvin et aI1997).

Maneuvering the arthroscope to examine the moreproximal regions of the carpal sheath reveals the radial headof the DDFT coursing from its aponeurosis on the DDFTcranially to curve and expand into its origin on the caudalaspect of the radius (see Fig. 12.23). The proximal checkligament can also be identified within the medial wall of the

~

Removal of radial osteochondromaRadial osteochondromas originating on the caudal portion ofthe radial metaphysis penetrate a variable distance into thecarpal sheath (Fig. 12.25). They are usually lateral and canbe easily identified arthroscopically. An 18-gauge spinalneedle is used to identify an appropriate instrument portaldirectly over the mass (Squire et al 1992). An osteotome(4 rom Cottle) is used to separate the osteochondroma fromthe caudal aspect to the radius. The osteochondroma is thenretrieved using large rongeurs, and the bony bed smoothedusing a curette, bone rasp, or motorized burr. Secondarydamage to the DDFT may require debridement with biopsyrongeurs or motorized apparatus. Finally, debris is flushedfrom the sheath before routine skin closure.

One of the principal advantages of tenoscopy compared toopen surgery for removal of osteochondroma is the ability toassess and treat tendon lesions, which also allows for a moreaccurate prognosis. Fibrosis and thickening of the carpalsheath secondary to osteochondroma is common, and anassessment of the degree of resultant carpal canal stenosiscan also be obtained tenoscopically. If there is evidence ofcarpal canal constriction, which can be subjectively deter-mined by the limitation to arthroscope movement throughthe carpal canal, release of the carpal flexor retinaculum canalso be accomplished (see later description).

Removal of radial physeal exostoses

Radial physeal exostoses are removed using a similartechnique to that for radial osteochondroma (Nixon 2002a,

Nixon et al 2004). Most clinically relevant radial physealexostoses involve protrusion of one or two caudally directedphyseal remnants (Fig. 12.26). The lateral remnant isgenerally more severe than the medial, and they can form avalley through which the DDFT courses. Damage to the DDFTcan be extensive, including excoriation of the epitenon, linear

during division of the more proximal regions of the checkligament. With experience. it is generally easier to performthe entire surgery with the arthroscope placed in the moredistal instrument portal. The instrument and arthroscopetend to follow a sinlilar plane, making triangulation moredifficult during the latter portion of the surgery. However, theproximal fibers of the check ligament can be identified anddivided using biopsy rongeurs. Use of a radiofrequency probe(Arthrex, Naples, FL) has been helpful to divide the proximalcheck ligament more cleanly (Fig. 12.30). However, becausethe probe cuts cleanly, and it can be difficult to see the depthsof the division between the closely apposed divided edges,particularly in the proximal region of the check ligament.

At the end of the procedure, the surface of the flexortendons should be carefully examined to be sure there are noadditional tendon injuries that may influence prognosis orrequire treatment. Several cases have also had tearing of theaponeurosis of the radial head of the DDFT with the mainstructure of the DDFT (Fig. 12.31). This has been recognizedby three of the authors; however, the clinical significance ofthis lesion is still unclear.

Carpal tunnel syndrome

The carpal flexor retinaculum can be released usingthe tenoscopic access portal described above. but withthe arthroscope directed distally rather than proximally(Fig. 12.32) (Textor et aI2003). Identification of the fibers ofthe carpal flexor retinaculum that form the medial aspect ofthe carpal tunnel is accomplished using digital pressurefollowed by insertion of a needle to define the distal andproximal extent of the retinaculum. An instrument portal isthen made 10-15 mm proximal to the accessory carpal bone.This should be defined by prior insertion of a spinal needle toverify there will be sufficient angulation for instrumentaccess to the distal aspect of the retinaculum. If the incisionis made immediately adjacent to the accessory carpal bone. itcan be difficult to insert instruments obliquely to access thedistal portion of the retinaculum. Arthroscopic release ofthe retinaculum is performed in the visible portion cranialto the SDFT and DDFT. Partial flexion of the carpus is used toallow retraction of the DDFT within the carpal canal andexposure of the~visible fibers of the carpal retinaculum. Theincision in the ,retinaculum is made 5-10 mm caudal to itsconfluence with the palmar carpal ligament. which forms thepalmar surface of the carpal joints (Fig. 12.33). Transectionis confirmed by entry into the tendon sheath of the flexorcarpi radialis. This is a major landmark in safely performingcarpal retinaculum release. Severing the carpal retinaculummore caudally risks perforation of the radial artery or medialpalmar vein. The palmar retinaculum predominantly runs onthe deep surface of the flexor carpi radialis tendon. althoughthere are some portions that are superficial (medial) tothis tendon (Textor et al 2003). The retinaculum is dividedwith a curved serrated blade or radiofrequency probe. cuttingproximally from the distal edge until 1 cm beyond theproximal border of the accessory carpal bone. The carpalsheath is then probed to ensure there are no thickened

recumbency. Penetration of the thin sheath surrounding theflexor carpi radialis tendon is routine. and is an importantlandmark since it defines the medial endpoint for thedissection (Nixon 1990a). Exchange of arthroscope andinstrument portals is often useful to improve visualization

1990b). The procedure is simple. has few risks of woundhealing complications. and can often be added to other pro-cedures during the tenoscopic examination and treatment ofdisorders of the carpal sheath contents.

Postoperative care

areas containing residual fibers of the carpal retinaculum,either proximally or distally. The flexor carpi radialis tendonshould be visible throughout the entire transected area

(Fig. 12.34).If necessary, the dissection can be continued superficial

(medial) to the flexor carpi radialis tendon, by retraction ofthis tendon cranially and division of the superficial lamina ofthe flexor retinaculum (see Fig. 12.34). The surgeon shoulddecide whether to continue the dissection through this thinmedial portion of the carpal retinaculum. This is based on thedegree of relief of the carpal canal, which can be assessed bythe increased ease of movement of the arthroscope and theincrease in viewable structures within the carpal canal.Severing the medial portion of the retinaculum can be donesafely, since the radial artery is approximately 7 mm caudalto the flexor carpi radialis tenqon. However, the medial palmarvein is only 2-4 mm caudal to this site, and careful dissectionis necessary to avoid perforating this vessel.

In clinical cases, the carpal sheath and flexor retinaculumhave been thickened predominantly on the deep (inner)portion, forming the visible interior layer of the retinaculumoverlying the flexor carpi radialis tendon. Division of only thisportion of the retinaculum has been adequate to resolvecarpal canal symptoms in two horses in a recent publication(Textor et al 2003), and a further seven horses operatedon since then. However, a larger case series has not beenpublished. Secondary carpal canal syndrome, developing as aresult of radial physeal exostoses, or myotendonitis and/ortendonitis of the contained flexor tendons, may also benefitfrom division of the carpal retinaculum, using the samerationale as described for treating flexor tendonitis within theconfines of the palmar annular ligament at the fetlock (Nixon

The use of tenoscopic techniques to evaluate the carpalsheath and address specific pathology has minimized woundhealing complications. The need for extended wound supportby bandaging and limitation of postoperative exercise hasalso been reduced. Return to an active walking program israpid, and the extent of layoff from work is then dictated onlyby the pathology of the tendons themselves rather than thesurgical approach. Animals are usually given perioperativeantimicrobial,l:lrugs. Intrathecal NaHA (20-40 mg) iscommonly usep, both at surgery and 2-3 weeks later. Follow-up intravenous NaHA may also be useful, commencing4-6 weeks after suture removal. Bandage support should beprovided to keep the arthroscopic and instrument portalscovered for the first 5-10 days after surgery. This usuallyconsists of light bandages, sponges. and adhesive elasticbandage. Most horses undergoing tenoscopic procedures ofthe carpal sheath show little lameness beyond the initial dayof surgery. Intrathecal anesthetics such as bupivacaine areuseful during surgery but generally are unnecessary in thecontrol of postoperative pain. Nonsteroidal anti-inflammatoryagents are usually given for 2-3 days after surgery.

Horses are confined to the stall for the initial 1-2 days aftersurgery. and small periods of hand walking are theninstituted. A balance is necessary between an early return to

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walking exercise and healing of carpal sheath structures.Adhesions associated with surgery in the carpal sheathappear to be rare.

five horses undergoing tenoscopic carpal canal release haverecovered from the lameness associated with the carpalsheath region (Textor et al 2003). The prognosis for SDFtendonitis treated by proximal check ligament desmotomy isdifficult to determine because of the influences of ancillarytreatment to the tendon, exercise protocol, and the amount oftime provided for convalescence.

Results and prognosis

Tenoscopy of the TarsalSheath

Introduction

The nomenclature surrounding the tarsal sheath and theDDFT has been through several changes. The DDFT has beenreferred to as the flexor hallucis longus and as the flexor digiti Itendon. The m()re recent term for the DDFT is the "lateraldigital flexor tendon". However, the use of DDFT is stillextremely common among surgeons and has been continuedhere for the sake of clarity. Persisting lameness associatedwith tenosynovitis of the tarsal sheath (thoroughpin) isrelatively common, and can result from trauma to the fibrouslayers of the tarsal sheath, damage to the meso tenon attach-ments of the DDFT within the tarsal sheath, and tendonitis ofthe DDFT itself (Van Pelt etal1969, Van Pelt 1969, Dik &Merkens 1987. Mcllwraith 2002b). Additionally. the DDFTcourses over the sustentaculum tali. which can be injuredthrough direct trauma, resulting in bone proliferation anddamage to the flexor tendon as it undergoes directionalchange through the region of the hock (Edwards 1978,Dik & Merkens 1987). The tarsal sheath is not invested byas dense a constrictive flexor retinaculum as the carpalsheath. and although "tarsal tunnel syndrome" is possible, itis poorly characterized (Van Pelt et a11969. Van Pelt 1969,

There are several individual case reports or small case seriesdescribing tenoscopic removal of osteochondroma, excisionof exostoses of the caudal aspect of the physis of the radius,and release of the carpal tunnel (ter Braake & Rijkenhuizen2001. Mcllwraith 2002a. Textoret al2003, Nixonet al2004).These reports suggest exostoses from the physeal remnantand osteochondroma arising from the metaphyseal regionpresent with similar carpal sheath effusion and lameness.and both resolve with mass removal (Mcllwraith 2002a.Nixon et al 2004). Lameness and effusion resolved in all 10cases reported with radial exostosis (Nixon et al 2004). Aseries of horses having endoscopically assisted check ligamentdivision has also been described (Kretzschmar & Desjardins2001). This procedure was considered minimally invasiveand was completed in less time than open division. It has alsoresulted in a renewed interest in the use of proximal checkligament desmotomy for treating SDF tendonitis. However.one of the authors (A.J.N.) recommends the procedureshould be performed bilaterally in all horses. regardless ofage. since a 6% incidence of bowed tendon in the oppositelimb has been recorded in a recent study (Nixon 2002b).

The prognosis following repair methods using carpalsheath tenoscopy largely depends on the original pathology.Ultrasonographic examination followed by tenoscopicevaluation and treatment provides critical information forthe prognosis, and the structure and duration of theconvalescent interval. The prognosis following removal ofosteochondroma and exostoses of the caudal perimeter of thephysis of the radius is good to excellent (Held et al 1988.Squire et al 1992, Southwood et al 1997. ter Braake &Rijkenhuizen 2001, Nixon et al 2004). The prognosisfollowing carpal retinacular release is unknown. although

Indications for tarsal sheath tenoscopy include a chronictenosynovitis that is poorly responsive to medical therapy.These cases may be improved by debridement of masses andadhesions spanning from the tarsal sheath parietal lining tothe DDFr. Several other manifestations of chronic tenosynovitismay be tenoscopically debrided. including tears of the DDFT,mineralizing masses within the tarsal sheath. and mineraliz-ation of the surface and deeper structures of the DDFT. Removalof fragmentation of the sustentaculum tali, and debridementand lavage of contaminated or infected tendon sheaths arealso major indications for tenoscopy (MacDonald et al1989.Welch et a11990. Santschi et al1997, Cauvin et al1999,Mcllwraith 2002b)

Surgical anatomy

small vinculae in the proximal recesses of the tarsalsheath (Cauvin et al 1999). As the DDFT approaches thesustentaculum, the tarsal sheath becomes narrowed by theflexor retinaculum forming the tarsal tunnel (Fig. 12.37).The distal cul-de-sac of the tarsal sheath is narrow andslightly better defined on the plantar aspect of the DDFT. Thiscul-de-sac contains a synovial fold attached to the DDFT andthe dorsomedial sheath wall, which forms a blind dorsomedialpouch (Fig. 12.38). The lateral extension of the tarsal sheathextends more distal than the medial terminal cul-de-sac, bothof which can be viewed tenoscopically. The tendon of insertionof the medial digital flexor tendon (MDFT) (flexor digitorumlongus), which has a separate tendon sheath, conjoins withthe DDFT ilIimidiately distal to the termination of the tarsalsheath.

There are no major neurovascular structures within thetarsal sheath, but there are several neurovascular bundlesassociated with its outer fibrous layers that need to berecognized when making instrument portals. Proximally, thedivided tibial nerve that has become the medial and lateralplantar nerves, the medial tarsal artery, and the recurrenttarsal vein are located in the caudomedial fibrous layers (seeFig. 12.36). The recurrent tarsal vein is in a more mediallocation, and is susceptible to injury when making instrumentportals. More distally, at the level of the sustentaculum tali,the medial and lateral plantar nerves, arteries, and veins arelocated caudally, deep in the fibrous layers of the tarsalsheath, but also within the confines of the tarsal flexorretinaculum (see Fig. 12.37). Distally, the chestnut overlies

The structures and associations of the tarsal sheath andthe enclosed DDFT throughout its course around the hockhave been described (Cauvin et al1999). The tarsal sheathcommences 6-7 cm proximal to the level of the medialmalleolus, and extends approximately one fourth of thedistance down the third metatarsus (Fig. 12.35). Theenclosed DDFT has a continuous mesotenon attachment onits caudo/plantaromedial margin, which is relatively thinand contains obvious fine vasculature (see Fig. 12.35 andFig. 12.36). This can limit visualization of caudal and caudo-lateral portions of the DDFT, depending on the position ofthe arthroscope access portal. The DDFT also has several

Fig. 12.37(A) Labeled diagram of B showing relevant structures in the cross-sectional specimen of the tarsal sheath at the level of the mid-sustentaculum tali. (B) Cross-sectional specimen of the sustentaculum level of the tarsal sheath. The sheath cavity contains red latex.(C) Same cross section with DDFT retracted to show medial mesotenon attachment spanning from the DDFT to the tarsal sheath.

Long digital

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the tarsal sheath medially, and has to be avoided. The lateralplantar neurovascular structures are positioned along theplantarolateral perimeter of the termination of the sheathand are relatively protected (Fig.12.38).

perforated in several areas if necessary, allowing thearthroscope to view the caudal portions of the proximalpouch of the tarsal sheath. A separate instrument entry,directly over lesions, is preferred for ease of triangulation. Thedorsomedial or plantaromedial arthroscope entry incisioninto the sheath is positioned largely based on the location ofthe predominant lesions, dorsal or plantar, to the mesotenon.

With the arthroscope directed proximally, the DDFTand proximal reflection of the tarsal sheath are evident(Fig. 12.40). The mesotenon and medial and cranial/dorsalsurfaces of the DDFT are readily examined. Redirection of thearthroscope more distally reveals the DDFT as it curvesover the sustentaculum tali (Fig. 12.40). Limited portions ofthe fibrocartilage surface of the sustentaculum forming thesupport surface for the DDFT can also be examined. TheDDFT can be retracted after a local instrument portal is made,which improves access to the caudolateral surface of thesustentaculum (Fig. 12.40). The medial extremity of thesustentaculum is extrasynovial and cannot be viewedtenoscopically.lhis area is also the most frequent site forbony exostosis. and fragmentation, which may then have tobe removed using open approaches. Over the sustentaculumthe tarsal sheath is confined by the tarsal flexor retinaculum,which stabilizes the DDFT (Fig. 12.40). Redirection of thearthroscope allows the DDFT to be viewed as it curves distally(Fig. 12.41). When the arthroscope entry has been madedorsal to the mesotenon, the sustentaculum and dorsal surfaceof the DDFT are readily examined. Advancing the arthroscopefurther distally allows examination of the remainder of thesustentaculum and the DDFT as it courses toward the distaltermination of the sheath. The medial mesotenon is thickerand somewhat compressed within the tarsal canal (Fig.12.41), and to facilitate examination of the distal regions ofthe DDFT and sustentaculum, sequential entry both dorsaland plantar to the mesotenon allows complete assessment of

Tenoscopic techniques

Diagnostic tenoscopy of the tarsal sheathSeveral approaches to the tarsal sheath have been described,but the preferred arthroscopic entry is a central medial portalmade 1-2 cm proximal to the sustentaculum tali (Fig. 12.39).This permits visualization of both proximal and distal regionsof the sheath (Cauvin et aI1999). Examination and debride-ment of the visible portions of the DDFT and many areas ofthe sustentaculum tali can be performed using instrumentportals directly over or immediately distal to the sustenta-culum tali.

The central medial approach can be performed with thehorse in dorsal or lateral recumbency with the limb extended.Hemorrhage is slightly reduced by using dorsal recumbency.and a tourniquet is useful for hemorrhage control whenusing lateral recumbency, since the affected limb is down. Thetarsal sheath is distended with saline if it is not alreadymarkedly enlarged. The voluminous outpouching of theproximomedial aspect of the tarsal sheath is readily palpated.A skin incision is made in the distal region of this proximaloutpouching. approximately level with the medial malleolusof the tibia. The arthroscope sleeve is inserted in a proximaldirection to commence the examination in the proximalregion of the tarsal sheath (Fig. 12.39). The mesotenon ofthe DDFT originates from the caudal/plantaromedial borderof the DDFT and provides a barrier to complete examinationof the caudal and medial portions of the tarsal sheath(Fig. 12.35). However, this layer is relatively thin. and can be

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the DDFT surfaces and the weightbearing surfaces of thesustentaculum.

A distomedial approach to the tarsal sheath is lessfrequently necessary (Fig. 12.42). The retinaculum of thetarsal sheath is more dense distally, and the chestnut providesa problem for sterile skin preparation. However, examinationof this area is occasionally necessary, and a skin incision canbe made 1-2 cm proximal to the level of the chestnut overthe medial aspect of the distended tarsal sheath (Fig. 12.42).The DDFT can then be seen as it courses over the distalportions of the sustentaculum tali. Surgical procedures inthe distal limits of the tarsal sheath are more difficult, due tothe small volume of the tarsal sheath at this level and theoverlying retinaculum. Additionally, the converging MDFTand check (accessory) ligament immediately distal to thetarsal sheath narrow the sheath as the distal limits are

approached.

Tenosynovial mass and adhesion resection~

Ultrasonogr~phic evaluation of cases with chronic tarsalsheath distention frequently reveals tenosynovial masseswithin the sheath (Fig. 12.43). Further inflammation andadvancing fibrosis of the tarsal sheath restrict the free rangeof motion of the DDFT within the tarsal sheath. Mineralizationis a late complication of chronic disease, and can involveportions of the mesotenon as well as the surface layers of theDDFT (Fig. 12.44). Removal of most tenosynovial masses canbe accomplished using the central medial approach to thetarsal sheath (Fig. 12.45). After a thorough examination, an18-gauge 7.5 cm spinal needle is used to define the mostappropriate portal for mass removal. The neurovascularstructures caudal/plantar to the tarsal sheath can be avoidedby penetration with arthroscope and instruments immediatelyadjacent to the cranial-caudal midline, allowing entry either

side of the mesotenon. This provides access for mass removaland debridement of the medial surfaces of the DDFT(Fig. 12.45). Masses can involve the inner layers of the tarsalsheath, or become more pendulous and float between theDDFT and the tarsal sheath lining (Fig. 12.46). With chronicdisease, the tarsal sheath can become quite thick, andexamination of the sheath contents can be slow and tedious.High ingress fluid pressure frequently results in subcutaneousfluid accumulation, making the surgical exploration moredifficult. A gradual increase in the areas available for examin-ation can be accomplished using motorized resection ofproliferative synovium. Masses can be removed with scissorsand rongeurs, biopsy punch rongeurs, motorized resection(Fig. 12.47), or radiofrequency probes, depending on thedensity of the masses. Large masses and mineralized areasmay need a second instrument portal to allow the mass to bestabilized prior to transection at its base. Mineralized massesgenerally result from dystrophic mineralization of chronic

lesions and are more common in the tarsal sheath than theequivalent syndromes in the carpal sheath. Radiographicallyevident mine~lization of the DDFT can be differentiated frommineralizatiqn in the mesotenon and sheath by comparing itsposition on extended and flexed radiographs. Motorizedresection of masses and surface proliferation of the DDFT canbe associated with hemorrhage. Tourniquet applicationproximal to the tarsal sheath may be helpful, but mosthemorrhage is controlled by the pressure of the ingress fluid.Distention with gas is an alternative if bleeding continues tohamper the diagnostic examination and further mass removal.

Mineralization can extend down to the terminal portionsof the tarsal sheath, and a second arthroscope and/or instru-ment entry in the distal medial recess of the sheath may berequired. After removal of masses, the sheath is flushed priorto routine skin closure. Intrathecal administration of NaHAmay be helpful in reducing reformation of tendon sheathadhesions.

Postoperative careDebridement of the sustentaculum taliThe sustentaculum tali is prone to trauma over its plantaro-medial aspect, resulting in bone proliferation within oradjacent to the insertion of the retinaculum on the calcaneus.Some wounds also cause contamination or infection of thetarsal sheath. The most medial areas of bone proliferation arebeyond the medial extremity of the tarsal sheath. Resection ofaccessible proliferative bone, and debridement of the DDFT-bearing surfaces of the sustentaculum, can be accomplishedusing the central medial arthroscope entry, with instrumentportals made directly over the sustentaculum. Alternatively,and sometimes additionally, the distomedial portal (Figure12.42), is required for arthroscope entry, to allow completeexamination of the medial edges of the sustentaculum andthe lateral perimeter of the tarsal tunnel as it curvesproximally. Fragmented or infected foci in the sustentaculumcan be removed and/or debrided using hand instruments.Further details concerning the principles of treatingcontaminated or infected lesions are provided in Chapter 15.

Wound healing complications associated with tenoscopicevaluation of ;he tarsal sheath are generally minimal.Exercise can b~ initiated 2-4 days after surgery, depending onthe degree of lameness. Horses respond to tenoscopic surgeryof the tarsal sheath differently, and some can be quite lamepostoperatively. This can be controlled at the time of surgeryby intrathecal deposition of bupivacaine at the time of closure,while postoperative pain relief is provided with nonsteroidalanti-inflammatory agents. More severe reactions to surgeryor the primary disease can be treated using epidurallyadministered morphine and detomidine. Horses with diseaseprocesses involving the sustentaculum tali frequently alsohave damage to the dorsal surface of the DDFT, and aremore lame than horses with tarsal sheath tenosynovitis.Additionally, follow-up medication to the tarsal sheath ismore likely to be necessary, and includes intrathecal NaHAand follow-up intravenous NaHA. Repeat ultrasonographic

examination is also useful in these cases to assess return oftenosynovial masses, and to evaluate tendon healing.

Results and prognosis

There are few published case studies of tarsal sheathtenoscopy (Cauvin et aI1999). Contaminated and infectedcases represent a large proportion of the tarsal sheathsrequiring tenoscopy (MacDonald et al1989, Santschi et al1997, Cauvin et al1999. McIlwraith 2002b). Their outcomeis often improved by tenoscopic debridement and lavage, butosteomyelitis of the sustentaculum is considered a seriouscomplication (MacDonald et al1989. Santschi et aI1997).Non-infected tarsal sheath tenosynovitis can be improved bymass removal and synovectomy, depending on the extent ofdystrophic mineralization.

include fibrous thickening of the sheath and secondary massand adhesion formation. Ultrasonographic evaluation revealsareas of fibrinous and fibrous tissue deposition, considerableamounts of free fluid. and quite often relatively normal tendonfiber architecture (Fig. 12.49). Lameness is variable butrestricted carpal flexion is common. In some cases tenoscopyis undertaken to improve the cosmetic appearance of thelimb. The presence of infection usually results in more severelameness. St~plechase horses are predisposed to thornpenetration of the forelimb extensor sheaths, which can leadto obvious lameness and the need for more aggressivesurgical and medical therapy (Platt & Wright 1997).

Tenoscopy of the ExtensorTendon Sheaths

Indications

Tenoscopic techniques

Tenoscopy of the extensor sheaths can be done in lateral ordorsal recumbency. The arthroscope portal to the affectedextensor sheath is generally made toward the proximal ordistal extremity of the sheath, depending on ultrasonographicevidence of the more severely affected region, which isreserved for the instrument portal. Examination of the interiorof the sheath often reveals adhesions and proliferativemasses. Most masses are combinations of fluid pockets or

The extensor tendon sheaths are prone to injury due to theirlocation on the dorsal aspect of the limb (Mason 1977, Platt& Wright 1997). Blunt trauma can result in variable degreesof tendonitis and chronic effusion of the sheath. A smallnumber of these cases do not spontaneously resolve, butprogress to develop intrathecal adhesions and soft tissuemasses. This can involve the sheath of the extensor carpiradialis, the common digital extensor, or rarely the lateraldigital extensor or extensor carpi obliquis in the forelimb. Inthe hind limb, the lateral digital extensor seems predisposedto injury and chronic distention. The long digital extensorsheath can be distended; however, this sheath merges withthat of the tibialis cranialis and the fascia of the dorsal aspectof the tarsus, and has little free space to distend with fluid orallow tenoscopic examination.

Extensor tendon fiber disruption varies from none tomoderate (Fig. 12.48), and the most consistent features

organizing fibrinous deposits (Fig. 12.50). Instrument portalsare made as necessary to allow rongeur and motorized resectoraccess for soft tissue debridement. The aims of debridementinclude removal of proliferative masses and re-establishmentof free motion of the affected tendon. Synovectomy should beused judiciously in an attempt to reduce fluid accumulationin the sheath. After removal of synovial masses, the use oftie-down sutures can occasionally be employed to reducedead space within the enlarged tendon sheaths (Fig. 12.51),although postoperative bandaging is considered moreimportant. Cosmetic results can be difficult to achieve inchronically distended extensor sheaths, unless some attemptat reducing the extensor sheath volume is utilized. Syno-vectomy of the parietal surfaces of the extensor sheath and

.pressure bandaging, occasionally with the use of splinting,can be effective in achieving cosmetic results. Occasionally,the use of cast-bandage combinations may also be necessary.Use of tenoscopic approaches to close spontaneous or iatro-genic fistulae between the carpal joints and the commondigital extensor tendon sheath or the tendon sheath of theextensor carpi radialis have been largely unsuccessful. Acombination of arthroscopically assisted synovectomy andlimited open approaches for suture are generally recommendedfor these fistulae.

Results of open treatment of chronic extensor sheathtenosynovitis are fair to good in the limited series of cases inthe literature (Mason 1977, Platt & Wright 1997). In theauthors' experience, tenoscopic treatment of the sheaths of

the extensor carpi radialis and common digital extensor.and the sheath of the lateral digital extensor of the hind limb.has allowed more aggressive debridement with good resolutionof lameness. Cosmetic appearance after debridement of mostdistended extensor sheaths can be substantially improved.although most have some residual fibrosis.

References

Chow JCY. Endoscopic release of the carpal ligament: a new tech-nique for carpal tunnel syndrome. Arthroscopy 1989; 5: 19-24.

Dik KJ. Dyson SJ. Vail TB. Aseptic tenosynovitis of the digitalflexor tendon sheath. fetlock and pastern annular ligamentconstriction. Vet Clin North Am Equine Pract 1995; 11:151-162.

Dik KJ. Merkens HW. Unilateral distension of the tarsal sheath in thehorse: a report of 11 cases. Equine Vet J 1987; 19: 307-313.

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Fortier LA. Nixon AJ. Ducharme NG. Mohammed HO. Yeager A.Tenoscopic examination and proximal annular ligamentdesmotomy for treatment of equine "complex" digital sheathtenosynovitis. Vet Surg 1999; 28: 429-435.

Gaughan EM. Nixon AJ. Krook LP. et al. Effects of sodiumhyaluronate on tendon healing and adhesion formation inhorses. AmJ Vet Res 1991; 52: 764-773.

Gerring EL. Webbon PM. Fetlock annular ligament desmotomy: areport of 24 cases. Equine- Vet J 1984; 16: 113-116.

Hago BED. Plummer IM. Vaughan LC. Equine synovial tendon sheathsand bursae: an histological and scanning electron microscopicalstudy. Equine VetJ 1999; 22: 264-272.

Held JP. Patton CS. Shires M. Solitary osteochondroma of the radiusin three horses. J Am Vet Med Assoc 1988; 193: 563-564.

Kretzschmar BH. Desjardins MR. Clinical evaluation of 49tenoscopically assisted superior check ligament desmotomies in

Adams OR. Constriction of the palmar (volar) or plantar annularligament of the felock in the horse. Vet Med/Small An Clin 1974;69: 327-329.

Arniel D. Ishizue K, Billings E, et al. Hyaluronan in flexor tendonrepair. J Hand Surg 1989; 14A: 837-843.

Barr ARS. Dyson SJ. Barr FJ, O'Brien JK. Tendonitis of the deep digitalflexor tendon in the distal metacarpal/metatarsal regionassociated with tenosynovitis of the digital sheath in the horse.Equine VetJ 1995; 27: 348-355.

Cauvin ER, Tapprest J, Munroe GA, May SA, Schramme MC.Endoscopic examination of the tarsal sheath of the lateral digitalflexor tendon in horses. Equine VetJ 1999; 31: 219-227.

Cauvin BRJ, Munroe GA, Boyd JS. Endoscopic examination of thecarpal flexor tendon sheath in horses. Equine Vet J 1997; 29:459-466.

Chow JC. Endoscopic release of the carpal ligament for carpal tunnelsyndrome: long-term results using the Chow technique.Arthroscopy 1999; 15: 417-421.

Southwood 11. Stashak TS. Fehn JE. Ray C. Lateral approach faendoscopic removal of solitary osteochondromas from the disuradial metaphysis in three horses. J Am Vet Med Assoc 199;210: 1166-1168.

Southwood 11. Stashak TS. Kainer RA. Tenoscopic anatomy of thequine carpal flexor synovial sheath. Vet Surg 1998; 2;150-157.

Southwood 11. Stashak TS. Kainer RA. Wrigley RH. Desmotomy <the accessory ligament of the superficial digital flexor tendon ithe horse with use of a tenoscopic approach to the carpal sheatlVetSurg 1999; 28: 99-105.

Squire KR. Adams SB. Widmer WR. Coatney RW. Habig (Arthroscopic removal of a palmar radial osteochondroma causincarpal canal syndrome in a horse. J Am Vet Med Assoc 199~201: 1216-1218.

Stanek C. Edinger H. Rontgendiagnostick bei der striktur defesselringbandes bzw. durch das fesselringband beim pfer<pferdeheilkunde 1990; 6: 125-128.

ter Braake F. Rijkenhuizen ABM. Endoscopic removal of oste<chondroma at the caudodistal aspect of the radius: an evaluatioin 4 cases. Equine Vet Educ 2001; 13: 90-93.

Textor JA. Nixon AJ. Fortier LA. Tenoscopic release of the equiDcarpal canal. Vet Surg 2003; 32: 278-284.

Van Pelt RW. Inflammation of the tarsal synovial sheat(Thoroughpin) in horses. J Am Vet Med Assoc 1969; 15:1481-1488.

Van Pelt RW. Riley WF. Jr. Tillotson PI. Tenosynovitis of the deedigital flexor tendon in horses. Can Vet J 1969; 10: 235-243.

Verschooten F. Picavet TM. Desmitis of the fetlock annular ligamerin the horse. Equine VetJ 1986; 18: 138-142.

Verschooten F. Picavet TM. Desmitis of the fetlock annular ligamerin the horse. Vet Ann 1988; 28: 98-101.

Watrous BJ. Dutra FR. Wagner PC. Schmotzer WB. Villonodulasynovitis of the palmar and plantar digital flexor tendon sheathand the calcaneal bursa of the gastrocnemius tendon in thhorse. Proc AAEP 1987; 33: 413-428.

Weiss C. Levy HI. Denlinger J. Suros JM. Weiss HE. The role of NEhylan in reducing postsurgical tendon adhesions. Bull Hosp JoirDis Orthop Instit 1986; 46: 9-15.

Welch RD. Auer JA. Watkins JP. Baird AN. Surgical treatment <tarsal sheath effusion associated with an exostosis on the cacaneus of a horse. J Am Vet Med Assoc 1990; 196: 1992-1994

Wilderjans H. Boussauw B. Madder K. Simon O. Tenosynovitis of tbdigital flexor tendon sheath and annular ligament constrictiosyndrome caused by longitudinal tears in the deep digital flexctendon: a clinical and surgical report of 17 cases in warmbloohorses. Equine VetJ 2003; 35: 270-275.

Wright 1M. McMahon PI. Tenosynovitis associated with longitudinltears of the digital flexor tendons in horses: a report of 20 case:Equin~etJ 1999; 31: 12-18.

27 horses. Proc 47th Ann Conv Am Assoc Equine Pract 200147: 484-487.

MacDonald MH. Honnas CM. Meagher OM. Osteomyelitis of th,calcaneus in horses: 28 cases. J Am Vet Med Assoc 1989; 1941317-1323.

Mcllwraith CW: Osteochondromas and physeal remnant spikes iIthe carpal canal. Proc 12th Ann ACVS Symposium 2002a; 12168-169.

Mcllwraith CW: Tenosynovitis; diseases of joints. tendons. ligamentand related structures. In: Stashak TS (ed.). Adams' lameness iIhorses. Philadelphia: Lippincott. Williams & Williams; 2002b630-633.

Malark JA. Nixon AJ. Skinner KL. Mohammed H. Characteristics adigital flexor tendon sheath fluid from clinically normal horsesAmJ Vet Res 1991; 53: 1292-1294.

Mason TA. Chronic tenosynovitis of the extensor tendons anctendon sheaths of the carpal region in the horse. Equine Vet1977; 9: 186-188.

Moro-oka T. Miura H. Mawatari T. et al. Mixture of hyaluronic acuand phospholipid prevents adhesion formation on the injure!flexor tendon in rabbits. J Orthop Res 2000; 18: 835-840.

Nixon AJ. Superficial flexor tendinitis. In: White NA. Moore IN (edsCurrent practice of equine surgery. Philadelphia: JB Lippincott1990a: 441-448.

Nixon AJ. Annular ligament constriction. In: White NA. Moore Jr(eds). Current practice of equine surgery. Philadelphia: JlLippincott. 1990b: 435-440.

Nixon AJ. Endoscopy of the digital flexor tendon sheath in horsesVet Surg 1990c; 19: 266-271.

Nixon AJ. Arthroscopic surgery of the carpal and digital tendo!sheaths. Clin Techn Equine Pract 2002a; 1: 245-256.

Nixon AJ. Medical and surgical therapy for tendinitis. Proc ACV:Symposium 2002b; 12: 161-164.

Nixon AJ. Sams AE. Ducharme NG. Endoscopically assisted annulaligament release in horses. Vet Surg 1993; 22: 501-507.

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Redding WR. Evaluation of the equine digital flexor tendon sheatlusing diagnostic ultrasound and contrast radiography. Vet Radioilltrasound. 1993; 34: 42-48.

Santschi EM. Adams SB. Fessler JF. Widmer WR. Treatment abacterial tarsal tenosynovitis and osteitis of the sustentaculuntali of the calcaneous in five horses. Equine Vet J 1997; 29244-247.

Introduction evaluation, reduced postoperative care, earlier return ofmobility, reduced convalescence and morbidity, and improvedresults compared with open surgical procedures,

Bursoscopy is a term which has crept into common usage todescribe intrathecal endoscopy of synovial bursae. These areclosed sacs. found interposed between moving parts or atpoints of unusual pressure and may be congenital or acquired.Congenital bursae develop before birth and are located inconstant positions. They may be subfascial. subligamentous.submuscular. or subtendinous. The latter are most commonand are found between tendons and bones at points wherethe tendon direction changes. The bursal side of the tendonand bone are fibrocartilaginous and in most circumstancesthe bursal margins are covered with villous synovium. In aclassical work. translated by Ottaway & Worden (1940). Muller(1936) described 22 congenital subtendinous bursae in thehorse. The principal congenital bursae of clinical importance(from an endoscopic perspective) are the calcaneal bursa. theintertubercular (bicipital) bursa. and the podotrochlear(navicular) bursa. Interestingly. techniques describing theirendoscopic evaluation were all published within 2 months ofeach other by Ingle-Fehr & Baxter (1998). Adams & Turner(1999). and Wright et al (1999). respectively.

Acquired. also called reactive. functional. or pathologicalbursae. are formed after birth. They are most common overosseous prominences and may be subcutaneous. The mostcommon etiology is synovial metaplasia within encapsulatedseromas or hematomata. The most frequent sites of acquiredbursae are subcutaneous or subfascial over the calcaneusand olecranon and either subcutaneously or between theextensor tendons and fibrous joint capsule of the metacarpo-phalangeal and metatarsophalangeal joints.

All bursae are amenable to evaluation with an arthroscope.In man. techniques have been described for endoscopictreatment of the subacromial (Ellmann 1987). deep infra-patellar (Klein 1996). trochanteric (Bradley & Dillingham1998) and retrocalcaneal (van Dijk et al 2001) bursae.Techniques reported include ablation. removal of tendinoustears and mineralization. debridement of fibrocartilaginousand osseous lesions. and decompression procedures. includingrelief of impingement lesions. debridement of torn tissue.ligament resection. and synovectomy (Levy et al1991. Klein1996. Bradley and Dillingham 1998. van Dijk et al 2001.Suenaga et al 2002). Endoscopic resection of acquiredolecranon and prepatellar bursae in man have also beendescribed (Kerr & Carpenter 1990. Kaalund et al 1998.Ogilvie-Harris & Gilbart 2000). All authors report improved

Calcaneal BursaThere are two congenital calcaneal bursae (Fig. 13.1). Thelargest has as its plantar margin the superficial digital flexor(sdf) tendon and. dorsally, is bordered by the tendon ofinsertion of gastrocnemius, the calcaneus, and the long plantarligament (Fig. 13.2). A smaller bursa, which is sometimesconjoined, lies between the tendon of insertion of gastro-cnemius and the calcaneus (Fig. 13.3).

Standard arthroscopic equipment is suitable for al~ bursalendoscopy and the usual principles of fluid distention withtriangulation of arthroscope and instruments apply. Incongenital bursae, portals are made abaxial to associatedtendons. Corporate experience of bursal endoscopy is (as yet)limited, and thus understanding of bursal pathophysiology isin its infancy. It appears that bursae respond to aseptic insultin a manner similar to tendon sheaths but little is as yetknown about healing of the fibrocartilaginous surfaces.Endoscopy has resulted in identification of previously un-reported lesions and it appears likely that the diagnostic andsurgical advances that have followed arthroscopy andtenoscopy will also be enjoyed with bursoscopy. The responseto open wounds and/or other introduction of contaminantsis common to all synovial cavities. However, with establish-ment of infection, the response of congenital bursae hassome features in common with tendon sheaths and some incommon with diarthrodial joints.

Current indications for endoscopy of congenital bursaeinclude lameness referable to the bursa, investigation ofbursal distention, contamination and infection. Some caseswill have radiologic and/or ultrasonographic changes, butthere is invariably bursal distention. Lesions identified andtreated endosc~ically include defects in the fibrocartila-ginous surface of tendons and bones, osseous fractures,lesions of adja~ent ligaments, contamination, and infection.The principal indications for endoscopy of acquired bursaeare contamination and infection.

Technique

Endoscopy of the calcaneal bursa may be performed with ahorse in lateral or dorsal recumbency. with the limb in anextended position. The technique described by Ingle-Fehr &Baxter (1998) is appropriate for the majority of circumstances(Fig. 13.4). Following standard preparation of the site. ifthe bursa is not distended markedly then it is inflatedfurther. A 1.1 x 40 mm (19-gauge x 1.5 inch) needle isinserted between the sdf tendon and the plantar ligamentdistal to the medial or lateral retinacular insertion of theformer and the bursa is distended maximally (Fig. 13.5A). Askin portal is created approximately 10 mm distal to theretinaculum, medially or laterally. and this is extended with aNo. 11 or 15 blade through to the bursa. The arthroscopicsleeve with a conical or blunt obturator is then inserted anddirected proximally, initially between the sdf tendon and longplantar ligament. and then plantar to the calcaneus andgastrocnemius to the proximal limit of the bursa (Fig. 13.5B).

This approach permits thorough examination of

evaluation requires rotation of the arthroscope in orderutilize its lens angle effectively. Instrument portalscreated at appropriate locations. as determined by

the retinacular insertions of the sdf tendon and mayipsilateral or contralateral to the arthroscope.

Endoscopic anatomy

Proximally, the bursa contains villous synovium. Almostcircumferential evaluation of the tendon of insertion ofgastrocnemius is possible (Fig. 13.6). It is at this site thatthere may be communication with the underlying bursabetween the tendon of insertion of gastrocnemius andthe calcaneus and, if present, this is usually identifiable.Proximally, the sdf tendon may exhibit some evidence oflongitudinal fiber orientation and proximal to the calcanealtuber there are sometimes visible shallow transverse lines or

far as the retinacular insertions of the sdf tendon.With further (distal) withdrawal of the arthroscope,

plantar ligament emerges from the fibrocartilage ofcalcaneal tuber. As this courses distally, itligamentous form (Fig.that the camera

distal recess of the bursa, the arthroscope may be

Villous synovium covers the capsular reflection fromplantar ligament to the dorsal surface of the sdf tendon.where there may once again be discernible ligamentous form.

Clinical application

Lesions identified and treated endoscopically includeosteolytic lesions in the calcaneal tuber. tearing of theretinacular insertions of the sdf tendon. tendonitis of the sdftendon. traumatic fragmentation of the calcaneus, contam-ination through open wounds, and punctures and infection.

ridges in its dorsal surface: as the sdf tendon approaches thecalcaneus and becomes wider in a mediolateral plane. theseare replaced by an amorphous fibrocartilaginous surface(Fig. 13.7). However. obliquely angled fibres are identifiable.extending medially and laterally from the sdf tendon to theabaxial margins of the calcaneus: these are the medial andlateral retinacular insertions of the sdf tendon (Fig. 13.8).Fibrocartilage also covers the apex of the calcaneal tuber and

Osteolytic lesions of the calcaneal tuber

Regions of osteolysis in the calcaneal tuber have beenreported by Ingle-Fehr & Baxter (1998) and Bassage et al(2000). Affected animals present with distention of thecalcaneal bursa and lameness that is responsive to intrathecallocal analgesia. Radiographs demonstrate radiolucencies in

the proximal plantar margin and/or apex of the calcanealtuber (Fig. 13.10). Ultrasonography confirms distention of thecalcaneal bursa and may also reveal disruption of the proximalplantar margin of the calcaneus and irregular echogenicity ofthe adjacent insertion of gastrocnemius. At endoscopy, theremay be discoloration of the calcaneal fibrocartilage with soft,crumbling, and apparently degenerate bone exposed by use ofa blunt probe. Removal of the degenerate bone and debride-ment has resulted in return to soundness but the number ofcases is small and thus confident prognostication is difficult.The etiology of such lesions is unknown. Previous authorshave tentatively suggested that these may be avulsion injuriesof the plantar ligament (Ingle-Fehr & Baxter 1998), or ofgastrocnemius (Bass age et aI2000).

may be hemorrhage at the site but torn fibrils are discernible(Fig. 13.11). Tearing and herniation of disrupted tendonfibrils is generally more obvious in long-standing cases(Fig. 13.12A). Removal of torn fibrils and debridement of theparent tendon is performed with a motorized synovial resector(Fig. 13.12B). Cases treated in this manner have returned tosoundness.

Traumatic fragmentation of the calcaneusE.xternal trauma, usually as a result of falls or kicks fromother horses, ~ay result in intrathecal fragmentation of thecalcaneal tuber. These may be open or closed. Most fracturesare identified radiographically and, when the apex of thecalcaneus is involved. flexed plantaroproximal-plantarodistaloblique (skyline) projections are most useful.

Endoscopy should be performed with ipsilateral arthroscopeand instrument portals. When accompanied by wounds, thesurgeon should look diligently for the presence of hair andforeign material. Fragments are removed with appropriatelysized arthroscopic rongeurs and the fracture bed debridedwith curettes. In some instances foreign material may beembedded in bone. Lesions should be debrided using the sameprinciples as applied with osteochondral fragmentation indiarthrodial joints but fibrocartilagenous margins alwaysappear less sharply demarcated than their hyaline counter-parts (see Fig. 14.9).

Tearing of the retinacular insertions of thesuperficial digital flexor tendon

Tearing of the medial (most commonly) or lateral retinacularinsertions of the sdf tendon has been associated withcontralateral luxation or subluxation of the tendon from theapex of the calcaneal tuber (Sullins 2002). Partial tears ofthe retinaculi have been identified on endoscopic examinationof the calcaneal bursa in animals with lameness, whichlocalizes to a distended calcaneal bursa. A tentative diagnosismay be obtained ultrasonographically, but a definitivediagnosis is obtained endoscopically. In acute lesions there

capsules and an intervening fat pad. '

the humerus bears three tubercles: lateral(lesser), and ~ intermediate tuberosity (tubercle). The over-lying tendon is bilobed and indented markedly by the inter-mediate tuberosity. The medial lobe is slightly larger than itslateral counterpart. A tendinous band envelops the tendonand bursa in the region of the humeral tuberosities. Over thehumeral tuberosities the biceps tendon is partly cartilaginousand presents a smooth fibrocartilaginous bursal surface. Themusculotendinous junction of biceps brachii lies in the distalportion of the bursa. which terminates just proximal to thedeltoid tuberosity of the humerus.

I ntertubercular (Bicipital)Bursa

The intertubercular bursa is found between the tendon oforigin of biceps brachii and the cranial margin of thehumerus (Fig. 13.13). The bursa envelops the medial andlateral margins of the tendon, and proximal to the humerusis separated from the scapulohumeral joint by their fibrous

Technique

Endoscopy is performed with the horse in lateral recumbency,with the affected limb uppermost and positioned parallel to

the ground (Fig. 13.14). In the majority of circumstances adistal arthroscopic portal. as described by Adams & Turner(1999) (Fig. 13.15), is most suitable but occasionally thereare advantages to a proximal arthroscopic portal. Generally,pathologic bursae are distended and there is no advantage tofurther distention. A skin portal is made using a No. 11 or 15blade over the craniolateral margin of the humerus 2-3 cmproximal to the deltoid tuberosity. Using a conical obtur~torthe arthroscopic cannula is directed axially and proximallythrough the brachiocephalicus muscle and between thecranial margin of the humerus and the tendon of origin ofbiceps brachii. Entry of the bursa is usually accompanied byflow of synovial fluid from the cannula. and this is advancedproximally before the arthroscope is inserted (Fig. 13.16Aand B). Instrument and/or additional arthroscopic portalsmay be made proximal to the lateral tuberosity of the humerusutilizing a percutaneous 1.2 x 90 mm (18 g x 3.5 inch)needle as a guide (Fig. 13 .16C). If necessary. arthroscopy andinstrument portals can be interchanged (Fig. 13 .16D). At theend of the diagnostic and surgical procedures the skin portalsmay be closed in a routine manner and the wounds protectedby oversewing swabs or gauze pads as stent bandages.

Endoscopic anatomy

Proximal to the humeral tuberosities the bursal synovium isvillous and covers the supraglenoid tuberosity of the scapula,the origin of biceps brachii, and the voluminous bursal recesscranial to the scapulohumeral joint. At this level, the proximalportion of the biceps brachii tendon has visible fiber orientation(Fig. 13.17). Withdrawing the arthroscope provides visualiza-tion of the lateral tuberosity and abaxial side of the inter-mediate tuberosity of the humerus. These and the overlyingbiceps brachii tendon are covered with smooth fibrocartilage

Fig. 13.14Horse positioned for endoscopy of the left bicipital bursa.

Fig. 13.15Distal endoscopic approach to the bicipital bursa; D = deltoidtuberosity of humerus; B = tendon of origin of biceps brachii;S = supraglenoid tubercle of the scapula; J = scapulohumeral

joint.

(Fig. 13.18). The tight interdigitation of the tendon and thecranial surface of the humerus precludes evaluation of themedial tubercle and axial side of the intermediate tubercle ofthe humerus from this arthroscopic position. Abaxial to thelateral margin of the lateral tubercle of the humerus there isa cover of fine synovial villi through which tendinous bandsfrom pectoralis ascendens are seen perpendicular andattaching to the lateral tuberosity. With further withdrawalof the arthroscope. a synovial plica is visible at the lateralmargin of the intertubercular groove (Fig. 13.19). At this levelthe arthroscope can be insinuated between the biceps brachiitendon and fibrocartilagenous surface of the humerus asfar axial only as the intermediate tubercle (Fig. 13.20).Approaching its distal margin the fibrocartilage is slightlyirregular (Fig. 13.21). Beyond this point the cranial surface ofthe humerus and biceps brachii tendon and musculotendi-nous junction are covered by villous synovium (Fig. 13.22).In the distal recess it is possible to visualize also a small areaof the fibrocartilage medial to the intermediate tubercle (Fig.13.22) and to push the arthroscope axially to obtain limitedvisualization of the distal medial lobe of the tendon. Utilizinga proximolateral arthroscopic portal. the most proximalmargin of the intermediate tubercle and a small portion ofthe medial lobe of the tendon can be visualized (Fig. 13.23).

Clinical applicationintrathecal fragmentation of the supraglenoid tubercle of thescapula and lateral tuberosity of the humerus together withcontaminated and infected bursae.

Endoscopy of the bicipital bursa has been used in theinvestigation of lameness referable to this site and to treat

adhesions to the bicipital tendon. The extensive nature of thelesions precluded treatment but endoscopy was considereddiagnostically useful. The authors have seen loss of humeralfibrocartilage with fibrillation of the adjacent bicipital tendon(Fig. 13.24) and rupture of the lateral wall of the bursa in

Traumatic bicipital bursitis

Booth (1999) reported a horse with lameness. localizing tothe bicipital bursa. that was accompanied by radiologic andultrasonographic abnormalities. Endoscopy revealed wide-spread loss of fibrocartilage from the humerus. with

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'-~'Oo"horses with lameness localizing to this site. These cases havebeen treated endoscopically by debridement of torn and/ordetached tissue.

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Fragmentation of the supraglenoid tubercleand lateral tuberosity of the humerus

Most fractures of the supraglenoid tubercle of the scapulaproduce large fragments that involve the articular surfaceand approximate to the physealline. However, occasionally,smaller more proximal fragments can displace distally andare intrathecal with respect to bicipital bursa. Such fracturescan be visualized, removed. and associated tissues debrided

endoscopically.Intrathecal fragmentation of the lateral tuberosity of the

humerus is most commonly associated with penetratingwounds. Radiologic signs can be subtle but frequently arehighlighted by craniomedial-caudolateral oblique projections.llitrasonography may also image fragmentation at this site.This may be removed and the fracture bed debrided utilizingthe arthroscope and instrument portals described above.

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~ ~ "'r,"'? I 'c."Contamination and infection

Endoscopic evaluation and treatment of an infected bursahas been described by Tudor et al (1998). The authors haveendoscopically managed contaminated and infected bicipitalbursae (see Fig. 14.5), including cases with infected osteitis/osteomyelitis of the humeral tuberosities. The use of proximaland distal arthroscope and instrument portals is recommended.Treatment follows the principles detailed in Chapter 14.

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Podotrochlear (Navicular)BursaThe dorsal margins of the navicular bursa are, from distal toproximal, the impar ligament, the palmar/plantar surface ofthe navicular bone, the navicular suspensory ligaments, andthe intervening T ligament. The latter is thin and consists oflittle more than the fibrous capsules of the distal inter-phalangeal joint, digital flexor tendon sheath, and navicularbursa. The dorsal surface of the deep digital flexor (ddf)tendon forms the palmar/plantar margin of the bursa.

~

Technique

Endoscopic evaluation of the navicular bursa is performedwith the distal limb joints in a slightly flexed position. Thehorse may be in either dorsal or lateral recumbency. Dorsalrecumbency facilitates triangulation and use of medial andlateral arthroscope and instrument portals. whereas lateralrecumbency is favored for investigation and treatment ofsolar penetrations. The technique described originally byWright et al (1999). and subsequently by Cruz et al (2001)

and Rossignol & Perrin (2003), permits the most compre-hensive evaluation of the bursa. A 5-mm skin incision is madeproximal to the collateral cartilage on the abaxial margin ofthe ddf tendon, palmar/plantar to the digital neurovascularbundle. The arthroscope cannula with a conical obturator isthen introduced through the skin wound and advanceddistally and axially, dorsal to the ddf tendon to enter thebursa at approximately the midpoint of the middle phalanx(Fig. 13.25). As the bursa is entered, there is usually a loss ofresistance to advancement of the cannula and the obturatoris then withdrawn and replaced by the arthroscope.

An instrument portal can be created using a similartechnique on the contralateral side of the limb following a

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ligament (Fig. 13.27). A slight withdrawal of the arthroscopewill allow evaluation of the sagittal ridge of the navicularbone and the adjacent surface of the ddf tendon. Thepalmar/plantar surface of the navicular bone is covered byrelatively homogeneous fibrocartilage. although in someanimals there is a shallow indentation (sometimes termed asynovial fossa) in the sagittal ridge where the overlyingfibrocartilage is thinner. The dorsal surface of the ddf tendonis indented to varying degrees for the sagittal ridge of thenavicular bone (Fig. 13.28). In some animals the dorsal surfaceof the ddf tendon presents a relatively homogeneous surface,whereas in others there is evidence of a longitudinallyoriented fiber pattern. Movement of the arthroscope mediallyand laterally peRmits evaluation of the abaxial margins of thebursa. This is ~nerally easiest on the side contralateral to thearthroscope but with rotation of the lens can be achieved alsoon the ipsilateral side. At the margins there are plicalreflections between the ddf tendon and the abaxial marginsof the navicular bone (Fig. 13.29). If the arthroscope is thenreturned to an axial position and withdrawn slightly further,this will visualize the proximal margin of the navicular boneand reflection of the T ligament from this site (Fig. 13.30).Abaxially, this thickens to blend imperceptibly into theinsertions of the suspensory ligaments of the navicularbone. Further proximally, the bursal reflection from the ddftendon, suspensory, and T ligaments is covered by villoussynovium (see Fig. 13.30). Proximal to the navicular bone.the dorsal surface of the dill tendon has a recognizablefiber pattern.

trajectory established by prior insertion of a 1.2 x 90-mm(18 g x 3.5-inch) stiletted needle.

Using the above technique, the trajectory of the arthro-scopic cannula is proximodorsal to distopalmar/plantar. Ifthe trajectory is too dorsal, then it is likely that the arthro-scopic sleeve will pass through the T ligament and into thepalmar/plantar compartment of the distal interphalangealjoint. In such circumstances, the sleeve should be withdrawnand realigned to a more palmar/plantar direction before it isadvanced again distally. This approach to the navicular bursamay also result in penetration of the digital flexor tendonsheath. In this event the arthroscope may be positioneddorsal to the ddf tendon at the distal reflection of the sheathwall before the arthroscope is withdrawn and replaced onceagain with a conical obturator. Advancement of the cannulain the trajectory described above along the dorsal surface ofthe ddf tendon, will usually result in successful entry into thenavicular bursa. It is also possible to enter the digital flexortendon sheath, electively pass the arthroscope distally dorsalto the ddf tendon and, then, use cutting instruments to createportals on the dorsal and palmar/plantar sides of theT ligament into the distal interphalangeal joint and navicularbursa, respectively (Fig. 13.26).

Endoscopic anatomy

Evaluation of the bursa usually commences distally. Here.villous synovium reflects off the ddf tendon and impar

date. there are inadequate numbers to assess the potential forendoscopic surgery to enhance case management.

Penetrating injuries of the navicular bursa

The management principles for contamination and infectionof the navicular bursa are similar to those of other synovialcavities and are dealt with in Chapter 14. However, at this sitethere are a number of features that merit special attention.The navicular bursa may be punctured by penetratingwounds in the palmar/plantar one-half of the solar surface ofthe foot. The risk and site of penetration are determined bythe length of the penetrating object and its trajectory. Inorder to reach the navicular bursa, there must be a penetratingwound in the~ddf tendon and, in some circumstances,perforating objfcts may continue also proximally through theT ligament and into the digital flexor tendon sheath or, morecommonly, distally through the impar ligament and into thedistal interphalangeal joint.

The bursa is evaluated utilizing an arthroscopic portal, asdescribed above (Wright et al1999). In acute cases there willusually be drainage of fluid from the puncture as soon as thebursa is inflated (Fig. 13.31). Thorough evaluation of the bursashould be performed in all cases to include identification ofthe puncture wound (Fig. 13.32) and detection of foreignmaterial (Fig. 13.33). Penetrating objects may also producedefects in the navicular fibrocartilage and/or underlyingpalmar/plantar subchondral bone. Instruments are generallyintroduced through the penetrating wound (Fig. 13.34).From this site, removal of foreign material and pannus and

Clinical

application

Currently, the principal indication for endoscopy of thenavicular bursa is evaluation and treatment of contaminationand

infection resulting from penetrating wounds. Thecontribution of the technique to the evaluation of lamenesslocalizing

to this site has yet to be evaluated. Intrathecallesions have been identified, removed, and debrided but, to

debridement of contaminated and infected tissues may

The ddf tendon is debrided by rotating a motorized synovialresector around its circumference.

be evaluated and treated by redirecting thecannula with c

approached in a conventional manner.At the end of the procedures, arthroscopic

instrument skin portals are closed routinely. Unlessundermining of laminar tissues, solar wounds

dressing.The resu~ of 10 of 16 (Wright et al1999) and 15 of 27

(Wright 20P2) animals being sound and returning to theirpre-injury use is significantly better than with open surgicaltechniques (Richardson et al 1986, Steckel et al 1989,Honnas et al199 5). There is also greater pain relief, reducedpostoperative nursing and medical requirements and fewercomplications with endoscopic treatment.

Diagnostic endoscopy

Endoscopy of the navicular bursa may provide usefulinformation in the evaluation of lameness localizing to thisarea but, as yet, its use has been limited. Lesions identifiedhave included fragmentation of the distal margin of the bone(Fig. 13.35), tearing of the impar ligament (Dyson 2002) and

ddf tendon (Fig. 13.36), and disruption of the fibrocartilageof the bone and ddf tendon (Fig. 13.37). However, thenumber of diagnostic examinations performed is small andclinically correlative studies are lacking.

ReferencesAdams MN. Turner TA. Endoscopy of the intertubercular bursa in

horses. J Am Vet Med Assoc 1999; 214: 221-225.Bassage IJI ll. Garcia-Lopez J. Gurrid EM. Osteolytic lesions of the

tuber calcanei in two horses. J Am Vet Med Assoc 2000; 217:710-716.

Booth TM. Lameness associated with the bicipital bursa in an Arabstallion. VetRec 1999; 145: 194-198.

Bradley DM. Dillingham MF. Bursoscopy of the trochanteric bursa.Arthroscopy 1998; 14: 884-887.

Cruz AM. Pharr JW. Bailey JV. Barber SM. Fretz PB. Podotrochlearbursa endoscopy in the horse: a cadaver study. Vet Surg 2001;30: 539-545.

Dyson Sf. In: Diagnosis and management of lameness in the horse.Ross MW and Dyson SJ (eds). Philadelphia: WB Saunders; 2002:286-299.

Ellmann H. Arthroscopic subacromial decompression: analysis ofone to three year results. Arthroscopy 1987; 3: 173-181.

Honnas CM. Crabill MR. Mackie JT. Yarbrough TB. Schumacher J.Use of autogenous cancellous bone grafting in the treatment ofseptic navicular bursitis and distal sesamoid osteomyelitis inhorses. J Am Vet MedAss 1995; 206: 1191-1194.

Ingie-Fehr IE. Baxter GM. Endoscopy of the calcaneal bursa inhorses. VetSurg 1998; 27: 561-567.

Kaalund S. Breddam M. Kristensen G. Endoscopic resection of theseptic prepatellar bursa. Arthroscopy 1998; 14: 757-758.

Kerr DR. Carpenter CW: Arthroscopic resection of olecranon andprepatellar bursae. Arthroscopy 1990; 6: 86-88.

Klein WK. Endoscopy of the deep infrapatellar bursa. Arthroscopy1996; 12: 127-131.

wvy HI. Gardner. Lenmak 1J. Arthroscopic subacromial decompressionin the treatment of full-thickness rotator cuff tears. Arthroscopy1991; 7: 8-13.

Muller F .ScWeimbeutel und Sebnenscheiden des Pferdes. Arch wisspracktTierheiIk 1936; 70: 351-370.

surface in patients with subacromial impingement syndromArthroscopy 2002; 18: 16-20.

Sullins KE. In: Stashak TS (ed.), Adams'lameness in horses, 5th edPhiladelphia: Lippincott, Williams & Wilkins 2002: 974-976.

Tudor RA, Bowman KF, Redding WR, Tomlinson JC. EndoscoJ;treatment of suspected infectious intertubercular bursitis inhorse. J Am VetMed Assoc 1998; 213: 1584-1585.

van Dijk CN, van Dyk GE , Scholten PE, Karte NP. EndoscOJ;calcaneoplasty AmJ Sports Med 2001; 29: 185-189.

Wright IM, Phillips TJ, Walmsley JP. Endoscopy of the naviculbursa: a new technique for the treatment of contaminated aJseptic bursae. Equine Vet 1999; 31: 5-11.

Wright IM. Endoscopy in the management of puncture woundsthe foot. Proc Eur Coli Vet Surg 2002; 11: 107-108.

~ Ogilvie-Harris DJ, Gilbart M. Endoscopic bursal resection: Tl

olecranon bursa and prepatellar bursa. Arthroscopy 2000; 1249-253.

Ottaway CW, Worden AN. Bursae and tendon sheaths of the hor~Vet Rec 1940; 52: 477-483.

Richardson GL, O'Brien TR, Pascoe JR, Meagher DM. Punctuwounds of the navicular bursa in 38 horses: a retrospective stucVetSurg 1986; 15: 156-160.

Rossignol F, Perrin R. Tenoscopy of the navicular bursa: endosco!;approach and anatomy. J Equine Vet Sci 2003; 23: 258-265.

Steckel RR, Fessler IF, Huston LC. Deep puncture wounds of tIequine hoof: a review of 50 cases. Proc Am Assoc Equine Pra1989; 35: 167.

Suenaga N, Minami A, Kimitaka F, Kaneda K. The correlatubetween bursoscopic and histologic findings of the acromion und

Introduction

Diarthrodial joints, tendon sheaths, and bursae are closedspaces with a similar mesenchymal synovial lining thatproduces and maintains a selective physical, cellular, andbiochemical environment. The principles of synovial contam-ination and infection are similar for each of these cavities.Contamination results from the introduction of micro-organisms and can occur through open wounds or self-sealingpunctures, by hematogenous spread, local extension of aperisynovial infection, or iatrogenically. Open wounds andself-sealing punctures may also introduce foreign material.Infection follows when the microorganisms reproduce andcolonize the synovial cavity. The principal potentiatingfactors for establishing infection are considered to be thepresence of foreign material and/or devitalized tissue, thenature and number of contaminating organisms, andimmunologic compromise, particularly in young animals.Following colonization of the synovium, a combination ofbacterial pathogenicity and host-immune response lead tothe release of a variety of enzymes and free radicals, whichresult in massive inflammation and ultimately destruction ofthe tissues in the synovial cavity. The acute inflammatoryresponse following inoculation of microorganisms is charac-terized by a rapid influx of inflammatory cells, predominatelyneutrophils (Bertone & Mcllwraith 1987). A plethora ofdestructive enzymes have been detected in synovial fluid frominfected joints, including collagenase, caseinase, lysozyme,elastase, cathepsin G, and gelatinase (Palmer & Bertone 1994,Spiers et al 1994). These appear to originate both frominvading neutrophils and activated synoviocytes. Togetherwith other inflammatory mediators, such as eicosanoids,interleukins, and tumor necrosis factor (Bertone et al1993)and the disturbed synovial environment in joints, thesetrigger production of degradative enzymes by chondrocytes(such as stromelysin, aggrecanase, collagenase, and gelatinase).There also is reduced proteoglycan synthesis (Palmer &Bertone 1994).

Established infection frequently results in the productionof an intrasynovial fibrinocellular conglomerate (pannus).This may cover foreign material and devitalized tissue. andact as a nidus for bacterial multiplication; it is rich in inflam-matory cells. degradative enzymes and radicals. It is also abarrier to synovial membrane diffusion. thus compromisingfurther intrasynovial nutrition and limiting access forcirculating antimicrobial drugs. The quantity and nature ofpannus appears to be dependent on the type and numberof infecting organisms. and its production is also enhancedby the presence of foreign material. Its presence has beenassociated with increasing duration of clinical signs. presenceof osteochondral lesions. and presence of osteomyelitis(Wright et aI2003).

The objectives in treating contamination and infection aresimilar for all synovial structures: removal of foreign material.debridement of contaminated/infected and devitalized tissue.elimination of microorganisms. removal of destructive enzymesand radicals. promotion of tissue healing. and restoration ofa normal synovial environment. A number of techniques havebeen described which include use of drains Gackman et al1989). through and through lavage (Koch 1979). open surgery(Rose & Love 1979. Honnas et al1991a. Bertone et al1992.Schneider et,.al 1992a. Baxter 1996). and endoscopy(Mcllwraith ],983. Bertone et a11992. Wright et al1999.2003. Frees et al 2002). Variations of these techniques havealso been described. These include open surgery followed byinsertion of closed suction (Mcllwraith 1983) or open passive(Santschi et a11997) drains or by open drainage (Bertone et al1992. Schneider et al 1992a) and endoscopy followed byclosed suction drainage (Ross et al1991. LaPointe et al1992).fenestrated drains (Honnas et al1991b). or creation of anopen draining wound (Bertone 1999).

In treating joint infection in man. arthroscopy is con-sidered to offer several advantages over lavage and arthrotomy.including improved visualization. identification of foreignmaterial and infected or devitalized tissue. and access to alarger area of synovial surfaces (Dory & Wantelet 1985. Jackson1985. Parisien & Shaffer 1990). Arthroscopy is reported to

ensure an efficiently evaluated, cleaned, debrided,decompressed joint with minimal morbidity,

to other treatments Garrett et al1981, Ivey & Clark 1985,

& Shaffer 1990, Bussiere & Beaufils 1999, Stutz et al2000,Wirtz et a12001. Vispo Seara et aI2002).

Four stages of joint infection have been reported in man(Gachter 1985. cited by Stutz et aI2000):

.Stage I: turbid fluid, hyperemic synovium, possiblepetechial bleeding, no radiologic changes.

.Stage II: severe inflammation. fibrinous deposition,purulent fluid, no radiologic changes.

.Stage III: thickening of the synovial membrane.villous adhesions and compartment formation, no

radiologic changes..Stage IV: aggressive pannus with infiltration of the

cartilage, possibly undermined cartilage. radiologicsigns of subchondral osteolysis, possible osseouserosions. and cysts.

These stages are related to but do not follow preciselytemporal categorization. Vispo Seara et al (2002) adopted thisclassification and recommended the following arthroscopictreatment protocols for each category:

.Stage I: thorough irrigation of all joint compartments.

.Stage II: removal of fibrin and clots. sometimes alsowith a limited synovectomy followed by I (above).

.Stage III: as II, but with resection of adhesions andsubtotal synovectomy.

.Stage IV: as above. but including removal of detachedcartilage and debridement of osseous lesions.

Stutz et al (2000) and Vispo Seara et al (2002) also reportedcorrelation between the stage of the disease process.prognosis, and the number of arthroscopic proceduresrequired. Like all attempts to categorize clinical disease, thisclassification suffers from oversimplification. Nonetheless, itprovides a useful comparative guide.

Evaluation

than in other endoscopic procedures and control of ]rhage improves the efficiency of the procedures significantly.

In most cases.made utilizing standard endoscopic portals as described inpreceding chapters. It is important in all circumstances toevaluate fully each structure and thus to use all availableportals. examining dorsal and palmar/plantar or cranial andcaudal compartments. and also, whenever appropriate,evaluating each cavity from both medial and lateral sides. If atourniquet is used, the surgeon should take particular care inthe creation of portals (especially into the digital flexortendon she~h), as neurovascular bundles are less readilyappreciated,and iatrogenic damage is possible.

An initial lavage of the cavity is usually necessary in orderto clear discolored synovial fluid. A thorough systematicevaluation should follow, examining the whole intrasynovialenvironment and. in turn, all of the contained structures.Particular attention should be paid to the vicinity of wounds

(Fig. 14.1).Acute synovial infection is characterized endoscopically

by severe synovitis (Fig. 14.2). In the absence of osteochondraldefects. chronic joint infection is characterized by cartilagedegeneration (Fig. 14.3). but if subchondral bone is breachedthen infected osteitis/osteomyelitis may result. If the epitenonis intact. chronic tenosynovitis is characterized by synovialproliferation and adhesion formation (Fig. 14.4). whereas if itis disrupted there is usually rapid intratendinous collagenolysis.

Most contaminated and infected synovial cavities areamenable to endoscopic evaluation and surgery. Occasionally,there will be sufficient capsular disruption to precludeinflation but in some individuals, even if there is markedtissue loss on one aspect of the limb, other synovial compart-ments may be treated endoscopically. The absence of adequatesynovial space precludes the use of endoscopy in few sites,the most frequently affected examples being the centrodistal(distal intertarsal) and tarsometatarsal joints.

Endoscopy is performed under general anesthesia and thepatient should be positioned to permit all-round access to theaffected synovial cavity(ies). Esmarch bandages and tour-niquets are recommended for distal limbs. Generally, there is

cover avillous synovium and in some advanced cases it alsocovers articular cartilage and tendon surfaces.

Foreign material

In the presence of open wounds or self-sealing punctures, thesurgeon should be aware of the potential presence of foreignmaterial within the synovial cavity. Frees et al (2002) foundintrasynovial foreign material in 4/20 (20%) of tenoscopicallyinvestigated wounds involving the digital flexor tendonsheath, whereas Wright et al (2003) documented foreignmaterial in 41 of 95 (43%) horses with wounds or puncturesinto synovial cavities which were investigated endoscopically.In the latter series, foreign material was predicted pre-operatively in only 15% of animals (Fig. 14.7). The majorityare free floating but the foreign material may also beadherent to pannus or synovium, embedded in osteochondrallesions or foun~in penetrating soft tissues. The most commoncontaminantsure hair and wood (Fig. 14.8A). An associationhas been demonstrated in man between the presence offoreign material and the development of infected synovitisfollowing penetrating wounds (Reginato et alI990). Foreignmaterial acts as a nidus for infection and causes physical andbiochemical irritation within the synovial environment.Large pieces may be removed with Ferris-Smith rongeurs(Fig. 14.8B), small pieces by a motorized synovial resector,and if embedded in bone, curettes may be necessary.

DebridementThe features of chronic infective bursitis are similar to bothinfected arthritis and tenosynovitis (Fig. 14.5).

Pannus is usually identified first over areas of villoussynovium and, as it increases in mass, villi become obscured(Fig. 14.6) If the infective process continues, pannus will also

In the series reported by Wrightet al (2003), 51 of 121 (42%)horses had endoscopically identifiable osseous or chondral

~

lesions, of which only 25 (49%) were predicted beforeendoscopy. Fragmentation may be removed with rongeurs.Foreign material may be embedded in the fracture bed(Fig. 14.9) and debridement of contaminated or infectedfracture sites is invariably appropriate. Foci of osteitis/osteomyelitis are generally debulked with rongeurs (Fig. 14.10)before debridement with curettes. Motorized burrs are rarelyindicated. When debriding chondral or osteochondral defectsin bursae, the surgeon should be cognizant that fibrocartila-genous m~ins will invariably be less well defined than theirhyaline co1interparts in diarthrodial joints.

Penetrating wounds and punctures of tendon sheaths andbursae may result in defects in the associated tendons(Fig. 14.11) and frequently articular wounds will alsotraumatize periarticular ligaments; an incidence of 34% hasbeen documented (Wright et al 2003). Removal of detachedcontaminated and infected tissue is appropriate and may beachieved with a motorized synovial resector. Occasionally,discrete detached pieces of tendon or ligament are removedmore satisfactorily by sharp dissection using arthroscopicscissors or knives.

Piecemeal removal of pannus preserves underlyingsynovium and is appropriate with localized deposits. Whenpannus is widespread, use of a motorized synovial resector isusually required, although this almost invariably results in at

least partial synovial resection. The authors' preference inmotorized resectors, for safety and efficiency, is an enclosed,serrated blade. This is used in a to-and-fro oscillating modewith suction applied to draw material into the blade. Angledblades are also available and can be useful in some areas.

It is suggested that synovium may harbor bacteria, sequesterinflammatory cells, release potent inflammatory mediators,and be a source of immunologic components of inflammation(Riegels-Nielson & Jensen 1984, Riegels-Nielson et aI1991).Synovectomy has therefore been proposed to be of benefit intreating infected arthritis (Ross et al1991, Bertone et al1992)although some surgeons consIder its use should be limited(Parisien & Shaffer 1990). The authors generally removecontaminated/infected synovium that is adjacent to woundsand punctures. More extensive resection is performed in thepresence of marked pannus deposits, which are usuallyassociated with long-standing infective processes. Regenerationof normal villous synovium does not occur followingsynovectomy (Theoret et al1996, Doyle-Jones et al 2002),but the clinical implication of this and potential compromisecompared to the benefits of synovectomy have not beendetermined.

(Bertone et al 1987a. Baird et al 1990) and this shouldbe delivered by a pump system capable of rates in excess of500 ml/minute. It is important to move the arthroscope. andthus the fluid ingress. repeatedly to all parts of the cavity inorder to produce effective lavage. The surgeon should be awareof all synovial sulci as. without individual attention. fluidswill frequently flow over or past pockets of debris in thesesites. This is particularly important in tendon sheaths. where.in addition to moving around the tendons. the arthroscopeshould be insinuated between these structures. The mechanicalaction of flushing removes small. free-floating debris. debulksmicroorganisms. and reduces the load of destructive radicalsand enzymes. Lavage is also thought to raise the pH from theacidic environment produced by infective processes. Thisin turn imprDKes the action of several antimicrobial drugs.including aInil1ogiycosides (Mcllwraith 1983). Effective lavageinvariably requires multiple ingress and egress portals. Inanimals with wounds or punctures. these may also serve asinstrument and egress portals (Fig. 14.12).

Potential additives to lavage fluid include antimicrobialdrugs. antiseptics. dimethyl sulfoxide. and fibrinolytics. Anti-microbial preparations used by the authors include a combi-nation of sodium benzylpenicillin (2.5 x 106 ill) with gentamicinsulfate (250 mg). or alternatively ceftiofur sodium (500 mg).amikacin sulfate (500 mg). or enrofloxacin (500 mg). addedto the final liter of lavage fluid. There is no objective evidenceto support the use of antimicrobial drugs in this manner.although administration of an aqueous antimicrobial oncompletion of lavage has been suggested to be of benefit(Nixon 1990). Antiseptic solutions appear to offer no

LavageLavage is visually directed, high pressure, and should beperformed thoroughly until all areas of the synovial cavityare visibly clean (Gaughan 1994, Thiery 1989, Smith 1986).The fluid of choice is sterile buffered polyionic solution

benefits have been documented, but deleteriousequine cartilage matrix metabolism have been(Matthews et al 1998. Smith et al 2000), Jthe use of fibrinolytics have been mentioned in the humanliterature (Jackson 1985), but they are uncommonlyemployed in veterinary medicine, With the advent ofendoscopic removal of fibrinoid deposits, their use largelyappears superfluous.

Wound management

Arthroscope and instrument portals are closed routinely.Traumatic wounds are debrided or (preferably) excised to aclean/ contaminated state and then if possible these also areclosed. This is based on the premise that endoscopic surgerycan thorou~y cleanse synovial cavities and that a closedwound minj,mizes the risk of further and/or secondary conta-mination or infection. These principles contrast with those ofothers in the literature (Gibson et al 1989, Schneider et al1992a, Baxter 1996) who advocate open management ofinfected synovial cavities in order to maintain decompression.Such alternatives include closed suction drainage (Ross et al1991, LaPointe et a11992), fenestrated drains (Honnas et al1991b), or creation of an open draining wound (Bertone1999), techniques which the authors also advocate in casesof chronic infection. Solar punctures are debrided, dressed,and managed as open wounds. Traumatic wounds elsewherein which soft tissue loss precludes closure should be debridedas rigorously as if closure was to be effected. The wound isthen dressed and the limb immobilized while secondintention healing ensues.

advantages over buffered polyionic solution (Bertone et al1986) and, even in dilute concentrations may produce synovialirritation (Bertone et al1986, Wilson et aI1994). Dimethylsulfoxide has been recommended as part of the final lavage(Bertone 1996,1999, Frees et al2002). Its efficacy has not

constructing a Robert Jones bandage). Commercial. tailoredelasticized bandages are effective on the carpus and tarsus.whereas in the proximal limb stent bandages may beoversewn.

Local antimicrobial therapy

At the completion of surgery, antimicrobial drugs may begiven by regional intravenous (iv) technique. Regional anti-microbial drugs have been shown to produce high andprolonged levels in synovial fluid (Whitehair et al1992a) andtheir efficacy in treating experimentally induced infectedarthritis in horses has also been reported (Whitehair et al1992b). Foals have been given 1 x 106m of sodium benzyl-penicillin with 100 mg of gentamicin sulfate or amikacinsulfate or, alternatively 100 mg of ceftiofur sodium. Otheranimals have received sodium benzylpenicillin (2.5 x 106 m)with gentamicin sulfate (500 mg) or, alternatively, amikacinsulfate (500 mg), ceftiofur sodium (500 mg), or enrofloxacin(500 mg). The doses all are empiric and have been used safelyin the authors' practices.

Antimicrobial drugs may also be given as intrasynovialdeposits, by continuous infusion, or by elution from impreg-nated polymethylmethacrylate (PMMA) beads or collagensponges. A number of authors have recommended intra-synovial injection of antimicrobial drugs (Lloyd et al1990,Schneider et al 1992a, McClure et al 1993, Baxter 1996,Bertone 1999, Frees et al2002). Dosages are empiric but it isgenerally recommended that drugs are given at not greaterthan a single systemic dose and that this is not repeated at lessthan 24-hour intervals (Baxter 1996). Infusion cathetershave been used for continuous administration of gentamicininto the tarsocrural joint of horses for up to 5 days (Lescun et al2000). This produced> 100 x the MIC (minimum inhibitoryconcentration) reported for common equine pathogens. Theuse of antimicrobial-impregnated PMMA is based on theprinciple that the antimicrobial drug will be released fromthe cement over time, thereby achieving continuous anti-microbial action in situ (Weisman et al 2000). Many of thecommonly used antimicrobial/PMMA combinations achievehigher local antimicrobial concentrations than can beachieved through systemic administration (Tobias et al1996).However, in-vitro elution tests suggest that antimicrobialconcentration at tissue level may be below the MIC for mostbacteria after 2-3 days (Weisman et al2000). Antimicrobial-impregnated PMMA beads may be deposited using arthroscopictechniques but a second surgical procedure will be necessaryfor their removal. Wire breakage can be a problem (Butson et al1996) and their use has also been associated with intra-articular trauma and capsulitis (Farnsworth et al 2001).Collagen sponges also can be deposited using endoscopictechniques. They are slowly absorbed and are reported tohave no irritant effect, although marked wound exudationhas been reported (Summerhays 2000). These techniquesmay not be necessary in acute cases but the authorsrecommend their consideration in cases of recalcitrant orrecurrent infection.

When wound healing will be optimized by limb immobiliz-ation. casts may be fitted. A nonadherent dressing is appliedover the wound with a thin layer of conforming bandage.This is followed by a layer (approximately 5 mm) of plaster ofParis and then layered fiberglass. Two of the authors (CWM.AJN) rarely use plaster of Paris anymore. Thermoplasticpolymer may be applied around the solar surface to resistabrasion and slipping. Counterpressure should be applied toall other sites: this limits extravascular exudation of fluid.promotes primary wound healing. and reduces pain (Nixon1990. Bertone 1999). It can be applied effectively to the distallimb with layered compressed cotton wool (as used in

Systemic antimicrobial drugs are appropriate in all cases.In most situations antimicrobial choice must, at least initially,be made without the results of bacterial isolation andsusceptibility determination. It is thus based on a knowledgeof the likely microbial populations involved in contaminationand infection of equine synovial cavities. Furthermore, withthe exception of juvenile infective arthritis of hematogenousorigin, results of bacterial isolation are frequently unrewardingand/or contribute little to the choice of effective antimicrobialregimes. When synovial contamination has a hematogenousetiology, single organisms may be responsible for infection.However, horses that develop synovial infection followingwounds are likely to have multiple bacterial involvement(Schneider et al 1992b). Reported bacterial studies andsusceptibility patterns suggest that a cephalosporin/aminoglycoside combination is likely to be most efficaciousbut that most organisms are likely to be susceptible to asynergistic combination of penicillin and an aminoglycoside(Snyder et al1987, Moore et al1992, Schneider et aI1992b).Wright et al (2003) reported the use of sodium benzylpenicillinat > 30,000 ill/kg iv every 8 hours and gentamicin sulfate at2.2 mg/kg iv every 8 hours. Single daily gentamicin adminis-tration at 6.6 mg has been proposed as an alternative. It issuggested that this achieves greater peak and lower troughconcentrations in serum and thus provides greater immediatebactericidal effect, longer duration of post antibiotic effect(PAE), and reduced risk of nephrotoxicosis (Godber et aI1995).However, the period of effective concentrations of gentamicinin tissues added to the PAE is also exceeded by every 8 hoursadministration at 2.2 mg/kg (Godber et al 1995). Also,gentamicin toxicity in horses is rare and there is no docu-mented reduction in incidence with once daily administration.In the authors' experience in animals which have no additionalmedical compromise, the three times daily regime has beensafe and is clinically efficacious.

With wounds involving the foot or wounds contaminatedby soil or feces, supplementing the above regimen withmetronidazole at 20 mg/kg orally every 8 hours is logical.Anaerobic species are important contributors to orthopedicinfections in horses and a 25% isolation rate from post woundinfected arthritis has been reported (Moore et al 1992).The majority of these bacteria are susceptible to penicillin.The most common isolates that are resistant to penicillin areBacteroides spp. which are common fecal contaminants. These,and all other anaerobic isolates from orthopedic infectionsare susceptible to metronidazole (Moore et aI1992).

The authors also have used a penicillin/amikacincombination: penicillin dosed as above with amikacin sulfateat 6.6 mg/kg iv every 8 hours. Low incidences of resistanceto amikacin have been reported among common equineorthopedic isolates (Snyder et al19 8 7) and organisms isolatedfrom horses with gentamicin resistance have demonstratedsusceptibility to amikacin (Orsini et al19 8 9). With known orsuspected staphylococcal involvement, such as cases of iatro-genic infection (LaPointe et al1992, Schneider et a11992b),

ceftiofur sodium is a logical choice at 3-4 mg/kg iv every8 hours either alone or in combination with gentamicin sulfatedosed as above. Enrofloxacin at 5 mg/kg iv every 24 hours or7.5 mg/kg orally every 24 hours has a broad spectrum ofactivity that includes staphylococci. It also has been useful inthe treatment of aminoglycoside-resistant Gram-negativebacteria (Orsini & Perkous 1992). Chondrotoxicity has beenreported at higher than clinically used doses (Beluche et al1999, Davenport et al 2001, Egerbacher et al 2001) and,consequently, caution has been expressed with respect to itsuse in foals (Orsini & Perkous 1992, Baxter 1996).

Determination of an appropriate duration of antimicrobialadministration is difficult. The authors prioritize clinical signsof response and continue antimicrobial administration untilthere is a consistent improvement in lameness, together withreduced synovial distention, adjacent soft tissue swelling,surface temperature, and engorgement of visible drainingveins. The use of sequential synovial fluid analysis has alsobeen advocated (Bertone 1999). Largely based on experiencesof experimental joint infection (Bertone et a11987b), otherauthors have employed or recommended protracted adminis-tration of antimicrobial drugs (Gibson et al1989, Honnas et al1991b, Gaughan 1994, Frees et aI2002). In a review of 121cases of synovial contamination and infection treated endo-scopically, there was a mean period of antimicrobial adminis-tration of 13 days (Wright et al 2003). A shorter period ofantimicrobial administration required with arthroscopictreatment of infected joints compared to other techniqueshas also been reported in man (Smith 1986).

Nonsteroidal anti-inflammatory drugs have been advocatedin the treatment of synovial infection to provide analgesiaand to limit deleterious effects of inflammatory mediatorson the synovial environment (Bertone & McIlwraith 1987,Gaughan 1994, Baxter 1996, Cook & Bertone 1998,Schneider 1999). There is some support for the concept in anexperimental rabbit model (Smith et al 1997). However, inthis experiment, the treatment comparisons were only betweenadministration of antimicrobial drugs or administration ofantimicrobial and anti-inflammatory drugs; there wasno surgical decompression or lavage, etc. Evidence thatsystemically administered therapeutic doses of nonsteroidalanti-inflammatory drugs suppress deleterious effects ofintrasynovial ~flammatory mediators is lacking (May & Lees1996). These\ drugs may partially lessen release of factorsinvolved in joint tissue breakdown (Lee et al 2003), butadministration of nonsteroidal anti-inflammatory drugseffectively obviates use of clinical parameters, particularlylameness, in determining response to treatment (McIlwraith1983, Gaughan 1994). Current opinion in assessing potentialbenefits of postoperative administration of nonsteroidal anti-inflammatory drugs is therefore divided. This is reflected inthe diversity of clinical use in the authors' practices, althoughall use nonsteroidal anti-inflammatory drugs for provision of

perioperative analgesia.Intermittently, the use of other, adjunctive medicaments

have also been recommended, principal of which is post-operative intrasynovial hyaluronan. Benefits have beenreported in an experimental model of tarsocrural infection

(Brusie et al199 2) and it has been advocated in clinical casesof infected tenosynovitis (Nixon 1990, Gaughan 1994, Freeset aI2002).

Movement is necessary for restoration of a normalsynovial environment and endoscopy permits an early returnto exercise (Nixon 1990, Frees et al2002, Vispo Seara 2002).The association between immobilization and cartilagedegeneration has been well documented (Palmoski et al19 79,Josza et al1987, Videman 1981, Kallio et aI1988). Benefitsfrom early instigation of exercise, in the form of continuouspassive motion, have been demonstrated in experimentalmodels (Salter et al1981) and reported in clinical cases inman (Parisien & Shaffer 1990, Perry et aI1992). Dynamicloading counteracts effects of inflammatory mediators, suchas bacterial lipopolysaccharide, on chondrocyte metabolismand it is suggested that this may have contributed tosuccessful management of articular infection (Lee et al2 00 3).Whenever possible, the authors recommend walking exerciseto commence in1mediately after surgery and a graduated,controlled exercise program follows in line with tissue

compromise.

Close clinical monitoring is critical in the immediate post-operative period. Since most synovial structures will beenclosed in bandages at this time, pain is the most sensitiveindicator of response to treatment. In the face of progressivelameness or lack of clinical improvement. complete case re-evaluation, including repeated radiographs, ultrasonographs.and synoviocentesis, is always merited. If potential reasonsfor relapse or lack of response can be identified, then manage-ment can be changed in a logical manner. Since endoscopymaximizes intrasynovial evaluation, this is also indicated inrecurrent or recalcitrant cases. Repeated endoscopy hasproved useful in detecting and removing foreign material,infected bone, and intra-articular sequestra that were notpresent or identified at the first surgery (Wright et al 2003).When no satisfactory explanation for a poor response orrelapse has been identified, then lack of susceptibility of thecausative organisms to the current antimicrobial regimenshould be considered and modification is frequently appro-priate. It always remains possible that infecting organismsare susceptible but that they have not been exposed to theantimicrobial drugs at an appropriate level; nonetheless, achange in regimen is usually made at this time.

arthrotomy and open drainage in the treatment of experi-mentally induced infection of tarsocrural joints (Bertone et al1992). However, this experiment does not reflect manyfeatures found in clinical cases of synovial contaminationand infection. Arthrotomy was also associated with anincreased risk of secondary infection by other organisms andpostoperative fibrosis and required a greater degree of post-operative care. The senior author of this report now alsorecommends endoscopy as a primary line of therapy (Bertone1999). Frees et al (2002) reported 18 of 20 (90%) casessurviving and 14 (70%) returning to athletic soundnessfollowing tenoscopic treatment of contaminated and infecteddigital flexor tendon sheaths. A retrospective analysis of 121cases of contaminated and infected synovial cavities treatedendoscopically reported a 90% survival rate, with 81% ofanimals returning to their preoperative level of performance.Negative prognostic indicators included involvement of thenavicular bursa, the presence of marked pannus, and thepresence of osteochondral lesions (Wright et al2003). Neitherof these studies found a correlation between the duration ofclinical signs prior to endoscopy and case outcome. In acomparable series of 192 cases treated by combinations oflavage, open surgery, drainage, intrasynovial antimicrobialdrugs, and systemic antimicrobial drugs, 73% of 126 animals>6 months of age and 45% of foals < 6 months of age survivedand 56% of 52 adult horses returned to performance(Schneider et a11992b).

The authors currently suggest that management ofcontaminated and infected synovial cavities is optimized byendoscopic treatment. This permits thorough evaluation,with appropriate debridement, effective lavage, and minimaltissue trauma. Multiple synovial cavities may be treatedsimultaneously, there is early pain relief, few complications,and minimal postoperative care. Animals are able to make anearly return to exercise and the prognosis appears to be betterthan with other reported regimens.

References

Results of endoscopic surgery in treating clinical cases ofcontaminated and infected synovial cavities have beenreported by a number of authors (Gibson et al1989, Ross et al1991, LaPointe et al1992, Schneider et a11992a. Steel et al1999. Wright et al1999, 2003. Frees et al2002). Arthroscopyand partial synovial resection were reported to be inferior to

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Bertone AL, Mcllwraith CW, Jones RL et al. Povidone-iodine lavagetreatment of experimentally-induced equine infectious arthritis.AmJ Vet Res 1987a; 48: 712-715.

Bertone AL, Mcllwraith CW, Jones RL et al. Comparison of varioustreatments for experimentally induced equine infectious arthritis.AmJ Vet Res1987b; 48: 519-529.

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Brusie RW, Sullins KE, White NA, et al. Evaluation of sodiumhyaluronate therapy in induced septic arthritis in the horse.EquineVetJ 1992; (Suppl) 11: 18-23.

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Butson RJ. Schramme MC, Garlick M, et at. Treatment of intrasynovialinfection with gentamicin impregnated polymethylmethacrylatebeads. Vet Rec 1996; 138: 460-464.

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Dory MA, Wantelet MJ. Arthroscopy in septic arthritis. ArthritisRheum 1985; 28: 198-203.

Doyle-Jones PS, Sullins KE, Saunders GK. Synovial regeneration inthe equine carpus after arthroscopic, mechanical or carbon dioxidelaser synovectomy. Vet Surg 2002; 31: 331-343.

Egerbacher M, Edinger J, Tschulenk W. Effects of enrofloxacin andciprofloxacin hydrochloride on canine and equine chondroytes inculture. Am J Vet Res 2001; 62: 704-708.

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Godber 1M, Walker RD, Stein GE, et at. Pharmacokinetics, nephro-toxicosis, and in vitro antibacterial activity associated with singleversus multiple (three times) daily gentamicin treatments inhorses. AmJ Vet Res 1995; 56: 613-618.

Honnas CM, Schumacher J, Cohen ND, et al. Septic tenosynovitis inhorses: 25 cases (1983-1989).J Am Vet Med Assoc 1991a; 199:1616-1622.

Honnas CM, Schumacher J, Watkins JP. et at. Diagnosis and treatmentof septic tenosynovitis in horses. Comp Cont Educ Pract Vet1991b; 13: 301-311.

Ivey M, Clark R. Arthroscopic debridement of the knee for septicarthritis. Clin Orthop ReI Res 1985; 199: 201-206.

Jackman BR, Baxter GM, Parks AH, et at. The use of indwellingdrains in the treatment of septic tenosynovitis. Proc Am AssocEquinePract 1989; 35: 251-257.

Jackson RW. The septic knee -arthroscopic treatment. Arthroscopy1985; 1: 194-197.

Summerhays GES. Treatment of traumatically induced synovialsepsis in horses with gentamicin-impregnated collagen sponges.Vet Rec 2000; 147: 184-188.

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polymethylmethacrylate. J Am Vet Med Assoc 1996; 208:841-845.

Videman T. Changes in compression and distances between tibialand femoral condyles during immobilization of rabbit knee. ArchOrthopTrauma Surg 1981; 98: 289-291.

Vispo Seara JL. Barthel T. Smitz H. et aI. Arthroscopic treatment ofseptic joints: prognostic factors. Arch Orthop Traum Surg 2002;122: 204-211.

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Introduction

There are only very few reports in the veterinary literature onequine temporomandibular joint (TMJ) disorders. Earlyclinical reports (Blasse 1909, Hardy & Shiroma 1991,Holmlund 1992) point out a relation between teeth and jawabnormalities and TMJ diseases. It was never clear ifabnormalities in teeth secondarily create TMJ diseases or viceversa. Recently, clinical attention has been drawn to disordersof this joint as possible reasons for headshaking, misbehavior,"back problems", and head tilt.

In humans, TMJ problems are much more commonlydiagnosed; 5-12% of North American people developsignificant and treatable disorders of the TMJ (Rugh &

Solberg, 1985).The few reports in the veterinary field describe mainly

dramatic situations such as luxation (Barber et al 1985),intra-articular fractures (Hurtig et al 1984), and septicarthritis (Warmerdam et alI997). These few reports mightgive a wrong impression of actual percentage of TMJ dis-orders. An initial report was presented by Boening (1996) ofa horse suffering from orthopedic symptoms which were laterlocalized as primary TMJ disease. He described a clinical caseof a German Warmblood dressage horse with chronic "backproblems" and active head tilt which was attributed to atransverse, unilateral tear in the joint disk of the TMJ. Thediagnosis was made arthroscopically after previous scinti-graphy of the head (Fig. 15.1), followed by intrasynovialanesthesia. This horse improved significantly after partialarthroscopic removal of the articular disk, debridement, andlavage. Postoperatively, this horse received repeated intra-articular corticosteroid injections.

Increasing use of imaging and minimally invasivetechniques has led to increased opportunities for diagnosticand therapeutic procedures. Different authors (Tietje, et al1996, Weller et al1999a, 1999b, Stadtbiiumer & Boening2000, 2002, Maierl et al2000) have described the anatomy,pathogenesis, radiologic and sonographic findings, (Fig.15.2), computer tomography abnormalities, and arthro-scopic approaches, as well as therapeutic and arthroscopicsurgery.

As the TMJ is another small joint. all specific features for smalljoints described previously for arthroscopic surgery of thedistal and proximal interphalangeal joints can be adapted.

The TMJ is an incongruous joint formed ventrally by thecondylar process of the mandibular head and dorsally by thezygomatic process of the temporal bone. As in all joints whichare incongruous. a fibrocartilaginous disk is interposed tolevel out the incongruity. This disk has an elongated.roundish appearance, and is about 5 mm thick at the border.Even in adult horses. the center of the disk is thinned andtransparent (Fig. 15.3). The TMJ is completely divided intotwo compartments: the dorsal disco temporal compartmentis more spacious than the ventral disco mandibulararticulation. Both compartments have caudal recesses; thedorsal caudal recess allows arthroscopic access to the discotemporal joint and the caudal ventral recess to the discomandibular compartment. A significant joint capsule. as wellas a lateral and a caudal (elastic) ligament, assure lateral

For unilateral arthroscopy of the TMJ, the horse is undergeneral anesthesia and in lateral recumbency -for a bilateralapproach, dorsal recumbency is an option. After spaciousshaving and aseptic preparation the caudal recessus of thedisco temporal joint is predistended with about 10-15 ml ofpolyionic R~er's solution. The insertion of a hypodermicneedle is made immediately adjacent to the dorsal aspect ofthe palpable condylar process. A skin incision is made with aNo. 11 scalpel blade right over the bulging rostral jointcapsule before the joint capsule is penetrated with anarthroscopic sleeve and a conical obturator of the 4 mm 300arthroscope (Figs 15.4 and 15.5) and advanced in a rostro-medial direction. The arthroscopic portal to the rostral recessof the ventral compartment is located immediately rostral tothe mandibular caput and ventral to the joint space. To enterthis compartment the sleeve has to be advanced in a morehorizontal plane and in a medial direction. This jointcompartment is even smaller than the dorsal compartmentand does not allow surgical manipulation. In this particularcompartment, because of the limited space. there is a higherrisk of iatrogenic cartilage damage.

stabilization of this joint. For invasive manipulation of theTMJ. the more ventrally located transverse facial artery andvein and the transverse facial branch of the auricular-temporal nerve have to be prelocated. Another structure ofimportance is the rostral-dorsal part of the parotid gland.partially covered by the parotid-auricular muscle.

Once in the joint, gas distention (CO2) prevents theprotrusion of synovium. After diagnostic evaluation ofthe joint. the ideal site for the instrument portal (about 1 cmfurther dorsally) is determined by inserting a hypodermicneedle. Routine exploration of articular structures is followedby passive movement of the mandible. This will expose rostralparts and allow disk palpation with a probe. Figures 15.6to

15.10 show examination of the proximal compartment

with the temporal bone above and the disk below. Figures15.6 and 15.7 are central and medial views respectively.Chondropathy on the temporal articular surface can beseen in Fig 15.8 with more chronic change in Fig 15.9.Penetration of the medial joint capsule results in exposureof masseter muscle fibers. Each arthroscopic procedureis followed by lavage and skin closure with simple inter-rupted sutures.

Temporomandibular Joint

Sound after 6 weeks

postoperatively

Chronic, diffuse

proliferative synovitis

Improved, but still irregular

headshaking

Improved, easy work

possible

Slight chronicheadshaking. behaviourai

problems

Swelling TMJ withreduction of jaw

motility

Post-traumatic

hemarthrosis, significantlesion joint capsule

Chronic swelling, rightjoint capsule after colic

Sound, no symptoms after6 weeks

Significant traumaticsynovitis andproliferation of villi +++

Scintigraphy: left TMJ hotspot +, ultrasound:distended joint filling

Ultrasound: joint

distention,

intrasynovialhyper-echogenicstructures

Scintigraphy: right hotspot +++, ultrasound:distended joint, increased

thickness joint capsule

Scintigraphy: right hotspot ++++, ultrasound:thickened joint capsule

Subtotal, transverse,axial rupture of articulardisk, secondary mechanical

synovitis, free floatingbony fragment, small size

Sound and back to fullwork after 4 months

Case 4Warmblood,6-year-old, gelding,showjumper

Case 5Warmblood,9-year-old mare

dressage

Significant back

problems, compressionpain right TMJ, bilateralteeth abnormalities

Resu Its graphy, and diagnostic/surgical arthroscopy (Table 15.1).Obvious clinical syndrome such as fractures, luxations. andseptic arthritis were not encountered in this study. Theage ranged from 6 to 12 years: 4 horses were Warmbloodsand one was a Quarter Horse; there were 3 geldings and2 mares.

An initial clinical series involving 5 Warmblood horses wasreported by Stadtbaumer & Boening (2002). Over 4 years

(1996-2000), they diagnosed TMJ diseases using differentdiagnostic tools such as scintigraphy, ultrasonography, radio-

Table 15.1 Horses with diagnosis of inflammation of the temporomandibular joint (TMJ) (1996-2000)

Treatment is summarized in Table 15.1. The outcome wasexcellent in three of five horses. with the symptoms in theremaining two improved. The authors emphasised the needfor careful examination of the TMJ in extended orthopedicwork-up when horses are presented with back problems.behavior problems. and headshaking.

ReferencesBarber SM. Doige CE. Humphreys SG. Mandibular condylectomie:

technique and results in normal horses. Vet Surgery 1985: 14:79-86.

Blasse A. Untersuchung fiber die Arthritis des Kiefergelenkes beimPferde. Inaug.-Diss.. GieBen 1909.

Boening KI. Equine arthroscopy Seminar. Proc ESVOT. Munich.Germany. 1996.

Hardy I. Shiroma IT. What is your diagnosis? Rostral luxation of theright temporomandibular joint. I Am Vet Med Assoc. 1991; 198:1663-4.

Holmland A. Diagnostic TMI arthroscopy. Oral Surg Oral Diagn.1992; 3:13-8.

Hurtig ME. Barber SM. Farrow. CS. Temporomandibular jointluxation in a horse. Am Vet Med Association 1984; 185: 78-80.

Maierl JR. Weller R. Zechmeister R. Liebich HG. Arthroscopic anatomyof the equine temporomandibular joint. Polish I Vet Sci 2000; 3(Suppl): 28.

May KA, Moll HD, Howard RD et al. Arthroscopic anatomy of theequine temporomandibular joint. Vet Surg 2001; 30: 564-571.

Rugh ]D, Solberg WK. Oral health status in the United States:temporomandibular joint disorders. J Dent Educ 1985; 49:398-405.

Stadtbaumer G, Boening KJ. Diagnostische und minimal-invasiveVerfahren am Kiefergelenk des Pferdes. Proc der Arbeitstagungder Fachgruppe "pferdekrankheiten" der DVG "Fortschritte in derMinimalinvasiven Chirurgie", Tutzing, 2000: 51-53.

Stadtbaumer G, Boening KJ. Diagnostische und arthroskopischeVerfahren am Kiefergelenk des Pferdes. Tieriirztl Prax 2002;30(G): 99-106.

Tietje S, Becker M, Bockenhoff G. Computed tomographic evaluationof head diseases in the horse: 15 cases Equine VetJ 1996: 98-105.

Warmerdam EPL, Klein WR, Van Herpen BPJM. Infectious temporo-mandibular joint disease in the horse: computed tomographicdiagnosis and treatment of two cases. Vet Rec 1997; 141:172-174.

Weller R, Cauvin BR, Bowen 1M, May SA. Comparison of radio-graphy, scintigraphy and ultrasonography in the diagnosis of acase of temporomandibular joint arthropathy in a horse. VetRecord 1999; 144: 377-379.

Weller R, Taylor S, Maierl J, Cauvin BRJ, May SA. Ultrasonographicanatomy of the equine temporomandibular joint Equine Vet J1999;31:529-532.

Weller R, Maierl J, Bowen 1M et al. The arthroscopic approach andintra-articular anatomy of the equine temporomandibular joint.Equine VetJ 2002; 34: 421-424.

IntroductionArthroscopy involves. in most circumstances. hospitalizationof horses and general anesthesia. which can both result incomplications to case management. In addition. there are anumber of intraoperative and postoperative complicationsthat are of particular importance with respect to arthroscopy.The nature and incidence of complications in human arthro-scopy have been documented for the most commonly operatedjoints and will be reviewed briefly. Documentation of compli-cations in equine arthroscopy is limited (McIlwraith 1990).

Complications of

Arthroscopyin Man

The most common joint for human arthroscopy is the knee.Three surveys have reported complication rates of 0.8%(DeLee 1985). 0.56% (Small 1986). and 1.68% (Small 1988).However. in a smaller series. Sherman et al (1986) reported acomplication rate of 8.2%. Complication rates of 9% for arthro-scopyof the ankle and 9.8% for the foot and ankle combinedwere published by Ferkel et al (1996) and Ferkel et al (2001).respectively. Complications occurred in only 1.6% of hip arthro-scopies reported by Griffin & Villar (1999). None of thesewere major or long term and most were attributed to use oftraction techniques. Kelly et al (2001) reported serious compli-cations in 0.8% and minor complications (which all resolved)in 11 % of arthroscopic procedures in the elbow. whereasReddy et al (2000) documented an overall incidence of 1.6%at this site. The highest reported incidence of complications inman appears to be associated with arthroscopy of the shoulder.where Berjano et al (1998) reported a 10.6% incidence.

The specific complications encountered in man vary withindividual joints and also with the surgical techniques used.The most common complications associated with arthroscopyof the human knee are presented in Table 16.1. Thecommonest complication associated with foot and ankle

(Ferkel et al 2001) and elbow (Kelly et a12001) arthroscopyis neurologic injury caused by iatrogenic damage to adjacentneural trunks. Systemic complications in man include cardio-pulmonary events, atelectasis, pulmonary embolus, myocardialinfarction, and death. Preoperative complications includeincorrect diagnosis, lack of preoperative planning, and failureto obtain appropriate preoperative studies (Ferkel et al2001).

A number of factors have been identified as predisposingto complications. Small (1986) and Ferkel et al (2001)recognized complex surgical procedures such as meniscalrepair and reconstruction of the anterior cruciate ligamentas being associated with an increased incidence of compli-cations. Indust&! injuries, meniscectomy, abrasion arthroplasty,patients of gre'ater than 50 years of age, and tourniquet timewere associated with increased risk by Sherman et (1986).Allum (2002) commented that, surprisingly, the incidence ofcomplications was unrelated to surgeon experience.

In making recommendations to minimize complicationsassociated with arthroscopy of the knee, Allum (2002) madefour specific recommendations:

1. Use of a sharp trocar should be avoided.2. Instruments should be used only if they can be seen clearly.3. Tissues should never be cut blindly but always under direct

visualization.4. Care should be taken with power instruments, particularly

when suction is applied, as this can rapidly result in jointevacuation and compromised visibility.

Hemarthrosis Ligament injuryInfection Neurologic injury

Thromboembolism FractureAnesthetic complications Adhesion formationInstrument breakage and/or failure Postoperative effusionArticular pain Wound healing complications

Complex regional pain syndrome Ecchymoses

Data from Delee (1985). Small (1986.1988) and Sherman et al (1986) reviewed

by Allum (2002).

Perisynovial neurovascular structures can be injuredby incorrect portal placement (Boardman & Cofield 1999,Ferkel et al 2001, Kelly et al 2001). More remote neuralinjury can result from inappropriate patient positioning ormanipulation and from extrasynovial fluid extravasation(Kim et al2002).

Postoperative effusion can be considered a sign ofunresolved lesions. Dandy (1987) has reported an incidencevarying between zero and 15% and ascribed the effusion toinflammatory synovitis. Hemarthrosis is said to have anincidence of 1% in human arthroscopy (Allum 2002). It istreated by lavage and instillation of local analgesic and

epinephrine.In arthroscopy of the knee, the use of skin sutures has

been reported to carry a higher complication rate than theuse of adhesive tape (Fairclough & Moran 1987) or leavingwounds open (Maffulli et alI991). No significant differenceswere reported between the latter two techniques (Hussein &Southgate 2001). By contrast, the use of skin sutures isassociated with a reduced complication rate in foot andankle arthroscopy (Ferkel et al2001). Also, an increased rateof drainage or erythema was noted with adhesive tapecompared to sutures in arthroscopy of the elbow (Kelly et al2001). If synovial fistulae result. treatment is focused onimmobilization (DeLee 1985, Proffer et alI991).

Hemarthrosis

Hemarthrosis is not usually a significant problem. Distal limbhemorrhage is invariably reduced when animals are in dorsalrecumbency compared to those positioned laterally. Use of anEsmarch bandage and tourniquet may be of benefit whendealing with lesions in which hemorrhage may be anticipated.Examples include contaminated and infected synovial cavitiesand tenoscopy of the digital flexor tendon sheath. In mostother situations. hemorrhage is controlled by the pressuregenerated by i,rigating fluids. However. if the joint is exited,left undistended. and then re-entered, the surgeon willencounter hemorrhage. particularly from debrided tissues. Insuch instances. flushing with an open egress cannula,followed by closure of the cannula and redistention, is allthat is necessary to eliminate the problem. The sameprocedure is performed if hemarthrosis is present at the timeof initial entry.

The fact that hemorrhage is minimized with distention isimportant to note, particularly with reference to debridementof subchondral defects. During curettage of subchondralbone, hemorrhage (as seen during arthrotomy) is not evidentwhile the joint is distended. The surgeon must thereforeeither use other criteria to evaluate an appropriate depth ofdebridement or must release fluid pressure in order to assessbleeding from subchondral bone.

The importance of thorough three-dimensional anatomicknowledge and location of the correct sites for creation ofportals has been emphasized in the shoulder (Boardman &Cofield (1999) and ankle (Ferkel et al 2001). The use ofappropriately sized instruments was also recommended byFerkel et al (2001).

Postoperative infection rates of 0.08%, 0.1 %, 0.23%, and0.42% have been reported following knee arthroscopy by(DeLee (1985), Sherman et al (1986), D'Angelo & Ogilvie-Harris (1988), and Armstrong et al (1992), respectively.Barber et al (1990) reported a postoperative infection rate of1.4% following arthroscopy of the ankle. The higherincidence at this site was attributed to thinner skin, lesssubcutaneous tissue and reduced local healing compared tothe knee. Factors which predispose to infection include longeroperating times, an increased number of procedures duringeach surgery, prior surgical procedures, chondroplasty andsoft tissue debridement (Armstrong et aI1992). Concurrentadministration of corticosteroids has also been identified asproducing an increased incidence of postoperative infection(Armstrong et al1992, Gosal et al1999, Kelly et al 2001).Allum (2002) states that most surgeons undertakingarthroscopy of the knee routinely do not use prophylacticantimicrobial drugs except for complex procedures such asreconstruction of the anterior cruciate ligament. However,D'Angelo & Ogilvie-Harris (1988) have suggested that theymay be indicated on a cost/benefit basis. Prophylacticantimicrobial drugs have been reported to reduce theinfection rate associated with arthroscopy of the foot andankle (Ferkel et a12001) and their use has also been advocatedwith arthroscopy of the elbow (Kelly et al2001) and should~r(Berjano et aI1998). In the face of postoperative infection therecommended treatment in man consists of intravenousantimicrobial drugs, repeated arthroscopy with debridementand vigorous high-volume lavage (Armstrong et al 1992,Ferkel et al2001, Allum 2002).

If instruments break, creating loose intra-articular debris,Allum (2002) recommends that, if the fragment is visible, thefluid should be switched off and the piece retrieved. If thepiece is not visible, then lavage may flush it into view or itmay be localized with conventional radiographs or fluoroscopy.Occasionally, magnetic instruments may aid retrieval (e.g.Golden RetrieveTM from Instrument Makar, Inc., Okamos, MI).

Pain is uncommon after diagnostic arthroscopy or simplesurgical procedures but may be a problem following extensivesoft tissue interference such as meniscal repair, synovectomy,or intra-articular reconstruction of ligaments (Allum 2002).This may be controlled by intra-articular opiates Ooshi et al1992) or local analgesics (Chirwa et al 1989). Complexregional pain syndrome, which has also been termed reflexsympathetic dystrophy, is a complex, unpredictable, andvariable problem which has proved difficult to define, predict,or prevent (Allum 2002).

Iatrogenic damage to articular cartilage is consideredthe most frequently unreported complication of arthroscopyof any joint (Ferkel et al 2001). Small joints are mostsusceptible and long-term sequelae are unknown (Ferkel et al2001).

Obstruction of view by synovial villi femur. Assessment of these sites can usually be made using aprobe to displace the villi, but frequently sufficient visualiz-ation to permit confident and accurate surgical interferencewill require local synovial resection (Fig. 16.2). This isperformed most efficiently with motorized apparatus withsuction attached. Resection should always be limited since,although the clinical implications are unknown, it has beendemonstrated that regeneration of normal villous synoviumdoes not occur (Theoret et a11996. Doyle-Jones et aI2002).In addition. overzealous use of motorized apparatus mayresult in trauma to the fibrous capsule.

Within each synovial cavity there are regions of villous andavillous synovium. Synovial villi may obstruct arthroscopicvisualization throughout a synovial cavity or this may be alocalized problem. When generalized, this problem is usuallyassociated with either inadequate distention or excessive fluidmovement. Distention may be limited by inadequate deliveryof fluid. capsular fibrosis. or the development of extrasynovialextravasation of fluid. Excessive fluid movement can occurwith an open outflow portal. This is seen most commonlywith an open egress cannula or an excessively large andpatent instrument portal. The latter can occur as a technicalerror but more commonly follows removal of large intra-articular fragments. For these reasons, initial arthroscopicexamination should be performed with a closed egress cannula.In addition, whenever feasible, large fragments should beremoved after small fragments. Many mechanical pumpswill deliver fluids at rates up to 1 liter/minute. These willcompensate for excessive fluid outflow in many situations,but at high flow rates bubbles are frequently produced, whichalso result in diminished visualization. Fluid exit through alarge, patent instrument portal can also be controlled to somedegree by retention of an instrument within the portal.However. the surgeon must try not to prevent fluid outflow byplacing a finger over the instrument portal. as this will resultin rapid extrasynovial extravasation.

Proliferative synovial villi may obscure articular marginsand lesions in these locations. Common examples includefragmentation of the dorsoproximal and plantaroproximalarticular margins of the proximal phalanges (Fig. 16.1) &ndosteochondritis dissecans of the lateral trochlear ridge of the

Many of the problems associated with obstructing synovialvilli are reduced or eliminated by use of gas distention.

In most circumstances extravasated fluid dissipates within24 hours of surgery. Occasionally. when associated with largefascial planes such as those adjacent to the femoropatellarjoint. this may take longer.

Extrasynovial extravasation of fluid

Iatrogenic damage to articular cartilageExtravasation of irrigating fluid into the subcutis and otherfascial planes is a problem commonly encountered whenlearning arthroscopic techniques but occurs, to some degree,even with the most experienced surgeon, The principalpredisposing factors are the shape of instrument portals,excessive perfusion pressure in the presence of obstructedoutflow, and instrument manipulation.

Instrument portals in which the incision in the skin andextra-articular tissues is smaller than the opening into thejoint will result in dissecting lines of fluid through fascialplanes. This can occur quickly and may be controlledeffectively by minimizing perfusion pressure at the time ofportal creation and also by completing the incision throughthe skin before the blade is advanced into the joint. The shapeof a No. 11 blade assists also, since this creates a triangularincision with the apex of the triangle at the point of the blade.An obstructed outflow with excessive perfusion pressure canoccur while instruments (particularly large instruments) arebeing inserted or manipulated. It results also during removalof large fragments, while these are being pulled through theinstrument portal. Selective reduction in perfusion pressureat this time will reduce the severity of the problem signifi-cantly. Similarly, repeated instrument entry and/or a largerange of instrument movement through a portal will open upand/or weaken fascial planes with the same result. Noyes &Spievack (1982) demonstrated that excessive intra-articularfluid pressure potentiates subcutaneous extravasation of fluid.

The site at which surgeons experience most difficultieswith extravasation of fluid is the scapulohumeral joint. Here,caudal instrument portals must traverse not only the skinand subcutis but also several centimeters of muscle andmultiple fascial planes. The ability of the periarticularmuscles and their fascial planes to imbibe fluid can result inrestricted articular distention and thus loss of visibility andsurgical access, particularly to lesions which are axial in thejoint. Since this joint generally requires a high perfusionpressure to maintain arthroscopic access, particular careshould be taken in the creation and use of instrument portals.Some degree of extra-articular extravasation is inevitable.The surgeon should be cognizant of its occurrence andplan surgical procedures such that more axially locatedlesions are treated first. Also, once extravasation has begunsurgical access time will be limited. Extrasynovial fluidaccumulation can also hamper instrument entry to the stiflejoints and both carpal and tarsal tendon sheaths. These areascan be reduced considerably by temporary cessation ofingress fluid and firm massage of fluid from skin portals.Surgery can then recommence. At the end of surgery largequantities of subcutaneously extravasated fluid may resultin excessive tension in skin sutures. This can usually beameliorated by simple hand massage of the site prior toclosure.

Full- and partial-thickness defects in articular cartilage canbe created iatrogenically: this occurs most commonly whenthe joint is being entered and particularly when there isminimal distention. It can be limited by careful technique anduse of a conical obturator (rather than a sharp trocar) in thearthroscopic sleeve.

Arthroscopic portals should be made using a blade directlyinto synovium and the sleeve then can be passed along thispathway with minimal resistance. Use of two hands, one toadvance the cannula and the second positioned adjacent tothe skin portal to act as a bridge or brake, is recommended. Inaddition. the surgeon should angle entry of the arthroscopicsleeve and subsequent instruments away from the direct lineof articular surfaces. When minor scuffing of the cartilagedoes occur, it does not appear to be of major significance(Dick et al19 78. McIlwraith & Fessler 1978).

Iatrogenic damage to other tissues

Perisynovial structures may be damaged inadvertently duringcreation of arthroscope and/or instrument portals. Obviously,the risk is dependent on proximity to portal sites. Elements ofthe palmar/plantar neurovascular bundle may be traumatisedin surgery of the digital flexor tendon sheath. Use of anEsmarch bandage and tourniquet appears to be a predisposingfactor in making the bundle difficult to identify. The surgeonis usually unaware of damage during surgery. Laceration ofthe palmar/plantar artery may become apparent on releaseof the tourniquet or by the presence of postoperativehemorrhage during recovery from general anesthesia. Thisusually is controlled by the application of counterpressure.Damage to the palmar/plantar nerve may be clinically silentbut a painful neuroma may develop at the site.

The carpal s~aths of extensor carpi radialis and commondigital extensor tendons can be penetrated by injudiciousplacement of arthroscope and instrument portals. This isusually apparent to the surgeon as intra- and postoperativedistention of the sheath. These sheaths can also betraumatized during removal of large fragments from thecraniodistal margin of the radius. The tendon sheath of thecommon digital extensor is most commonly affected whenfragments are removed from the craniolateral margin (inter-mediate facet) of the radius.

Intrasynovial instrument breakage

The most common cause of instrument breakage is the use ofinappropriate force. It follows that the incidence of this

Intrasynovial foreign material

Tiny metallic fragments have been seen following impact ofinstruments on the arthroscopic sleeve or sometimes followingother "metal on metal" contact. Such debris is usually flushedout with the irrigating fluid or may become embedded in thesynovial membrane. No detrimental effects have beenrecognized.

When needles are used either to inflate a synovial cavity orto determine sites for appropriate instrument portals. thesemay cut small pieces of skin. which are carried into thesynovial space. This is seen most frequently with stilettedneedles. If adhesive drapes are employed. then needles willalso carry small pieces of plastic into the synovial space. Suchdebris is readily flushed from the synovial environment andno adverse effects have been recognized. The risk of pushinglarger pieces of plastic into the synovial cavity or adjacenttissues can be reduced by removing the adhesive materialfrom the immediate vicinity of portals. Plastic fragments canresult in swelling and discharge when lodged in the subcutis.

Infection

The incidence of intrathecal infection following arthroscopicsurgery in horses has not been documented but appears rare.Nonetheless. the potentially devastating consequences ofiatrogenic synovial infection mean that aseptic techniquesshould never be compromised. Direct visualization has beenidentified as an obvious potential source of contaminationbut its use is now virtually obsolete. The authors have

problem usually decreases as a surgeon gains experience. Ifloose pieces are created within the synovial environment,then fluids should be stopped immediately or the perfusionrate reduced dramatically in order to maintain the fragmentin the visible field. An appropriate grasping instrument shouldthen be inserted and the fragment removed. If the piece dis-appears from view, a systematic search should follow, bearingin mind that most pieces will be metallic and therefore willgravitate to dependent areas (Fig. 16.3). If this fails to locatethe debris, then intraoperative radiography should be employed(Fig. 16.4). Magnetic retrievers are available but the limitedfrequency of their use makes the cost hard to justify.

Prevention is certainly better than cure and the surgeonshould avoid excessive bending or lever movements. The useof fixed rather than disposable blade cutting instrumentswithin joints is also recommended. Disposable No. 15 scalpelblades and the shafts of small angled spoon curettes areconsidered to be particularly vulnerable to intra-articularbreakage.

Ferris-Smith arthroscopic rongeurs are a workhorse ofequine arthroscopic surgery. However, if used inappropriately,particularly if attempts are made to twist firmly attachedbone, then the pin linking the blades will shear. This disarmsthe instrument completely but does not produce debris. Thepin can be replaced by manufacturers.

Minor trauma to the distal window of the arthroscope willresult in cumulative image artifacts and loss of clarity,whereas major trauma can cause complete loss of image.There is generally no intrasynovial debris. Trauma to theglass is minimized principally by careful surgical techniquesand it is vital to maintain a direct view of instruments duringsurgical procedures. Protection of the distal window is aidedalso by a slightly recessed arthroscope position within thecannula.

Sudden movement during surgery, which occurs mostcommonly if an animal begins to wake, can bend or breakinstruments (Fig. 16.5).

implicated inadequate or premature removal of postoperativebandages in cases of postarthroscopic infection of tarsocruraljoints.

There is no consensus on the use of prophylactic anti-microbial drugs with arthroscopic surgery, although theauthors all use perioperative medication. Penicillin preparationsare most commonly employed. One frequently used regimenis intravenous sodium benzylpenicillin at >20,000 ill/kggiven at the time of anesthetic premedication followed bythree similar postoperative doses at 8-hour intervals. Alter-natives include a similar protocol with potassium penicillin oruse of intramuscular procaine penicillin. When implants areused or if there is a history of recent intra-articular medi-cation, then a combination of penicillin and gentamicin maybe employed.

Infected cellulitis and/or fasciitis have been documented asuncommon sequelae to arthroscopic surgery. All casesappear to have resolved following systemic administration ofantimicrobial drugs. Drainage from skin portals or surgicallycreated sites mayor may not occur (Fig. 16.6):-

Occasionally, small skin abscesses or suture sinuses areencountered. These almost invariably require no treatmentand resolve when sutures are removed, although in somecases a small fibrous lump may persist at the site. Infectioncan also follow suture removal if this is not performed

appropriately. may not be so in the tarsocrural joint. Mild synovial distentionmay persist without clinical significance. for example whenpreoperative distention has been long-standing. In theabsence of additional clinical signs. such as lameness andreduced or resented flexion. mild distention usually does notjustify further investigation or treatment. Marked synovialdistention is more likely to result when active intrasynoviallesions persist and re-evaluation is indicated. If causativelesions are not identified. then treatment of the synovitis maybe beneficial.

Postoperative distention/synovitis

Distention usually signifies persistent synovitis and thusongoing intra-articular (or intrathecal) problems. However,this is an oversimplification. There is variability according tosite, e.g. in the femoropatellar joint persistent distention isfrequently a sign of continued intra-articular lesions but this

Failure to remove fragments

In surgery for removal of traumatic or developmentalfragments it is possible. particularly in cases with multiplefragmentation. that all pieces are not removed. There are anumber of possible explanations which fall into two broadcategories: those fragments which may be identifiedimmediately after surgery and those that are identified later.The former category includes the simple surgical error offailing to identify lesions. Predisposing factors includeinadequate preoperative examination -e.g. failure to identifyfragments that may be medial and lateral in a joint andincomplete arthroscopic evaluation of the joint. At some sites-e.g. the dorsoproximal margin of the proximal phalanx -fragmentation can be covered by proliferative synovium andmay not be apparent until this is lifted with a probe. In someanimals there is a distinct dorsal recess of the joint capsule atthis site. which also can obscure fragments. At other sites -e.g. in animals with multiple. loose osteochondral fragmentsin the femoropatellar joint -it may be difficult to determineaccurately from preoperative radiographs the exact numberof fragments which need to be accounted for. It should also beappreciated that some fragments identified radiographicallymay be embedded within the joint capsule. Current opinionsuggests that the dissection necessary to identify and removethese is not justified. Failure to remove fragments is limited bya thorough preoperative evaluation and the surgeon shouldensure that all identified fragments are accounted for atsurgery. Within individual joints. loose fragments movefrequently to consistent locations. e.g. into the suprapatellarpouch of the femoropatellar joint (Fig. 16.7) or the inter-

condylar fossa of the medial femorotibial joint. These sitesshould always be assessed at the end of each surgery anddebris removed. Use of intraoperative and postoperativeradiography has been recommended (and can help avoidlitigation), but is not necessarily an assurance.

Lesions that may be identified some time after surgery andmisinterpreted as failure to remove fragments include newbone deposits at the site of previous lesions, fragmentationof the same, additional new fragments, and dystrophicmineralization in adjacent soft tissues.

Postoperative cal?sulitis, entheseousnew bone, and soft tissuemineralization

In many instances capsulitis may be present preoperatively,such as when there is tearing of the fibrous joint capsule(Fig. 16.8) or can be anticipated when articular damage issevere. Problems can also develop with surgical trauma to thejoint capsule. Traumatic attempts at removing capsular frag-ments, trauma to the capsule during debridement, particularlywith motorized apparatus, and undue trauma to the sensitivetransition zone of the joint can all cause problems.

Problems associated with positioning

Transient failure to extend hind limb joints on recovery fromgeneral anesthesia has been noted following long surgicalprocedures in which (usually both) hind limbs are fixed in an

extended position. Some cases are thought to be associatedwith a femoral neuropathy or neuromyopathy involving thequadriceps muscles. Others appear able to fix the proximaljoints but fail to extend the metatarsophalangeal and inter-phalangeal joints. In both instances, symptoms generallysubside quickly. The problem is readily controlled bysupporting extended limbs during surgery and by flexing thecontralateral limb while this is not undergoing surgery.

Pain

Anesthetists frequently report that distention of the digitalflexor tendon sheath is more painful than joint distention.Postoperatively, the degree of pain exhibited by horsesappears proportional to soft tissue (particularly tendon andligament) involvement. However, this is usually transient andrequires little more than analgesia provided by nonsteroidalanti-inflammatory drugs for 24 hours after surgery. It hasbeen reported that horses with extensive articular or tendonsheath derangements can be maintained on lower levels ofinhaled anesthetic agents and have improved recovery byusing bupivacaine or mepivacaine for initial synovial inflation.One author (AJN) now u~es such a protocol routinely.

Generally, most complications can be avoided by goodtechnique and none preclude the advantages of arthroscopicsurgery. The problems with equine arthroscopic surgery aremainly technical and anatomic. Good technique comes withtraining and experience and the benefits of practice oncadaver limbs cannot be overemphasized.

References

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Doyle-Jones PS, Sullins KE, Saunders GK. Synovial regeneration inthe equine carpus after arthroscopic, mechanical or carbondioxide laser synovectomy. Vet Surg 2002; 31: 331-343.

Fairclough JA. Moran CG. The use of sterile adhesive tape in theclosure of arthroscopic puncture wounds: a comparison with asingle layer nylon closure. Ann R CoIl Surg Engl 1987; 69:140-141.

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Ferkel RD, Small HN, Gittins }E. Complications in foot and anklearthroscopy. Clin Orthop ReI Res 2001; 391: 89-104.

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Griffin DR, Villar RN. Complications of arthroscopy of the hip. J BoneJoint Surg (Br) 1999; 81B: 604-606.

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McIlwraith CWo In: Diagnostic and surgical arthroscopy in the horse,2nd edn. Philadelphia: Lea and Febiger; 1990.

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weanlings compared to debridement of articular erosions inadults. The size of the lesion is critical. Convery et al (1972)showed that lesions in the equine femorotibial joint less than3 mm in diameter healed with little residual deformity(Convery et al 1972). More recently, Hurtig et al (1988)determined that lesions larger than 15 mm2 in surface area(3 x 5 mm rectangle) tended to show reasonably good repairat 5 months but degenerated with increasing time (Hurtig et al1988). These studies indicate that most clinically relevantdefects in adults cannot be expected to heal well. Themetaplasia of fibrous tissue to fibrocartilage is not alwaysevident, and depending on the time of examination, degener-ation to fibrous tissue and later mechanical erosion of therepair tissue can occur. Repair tissue is biomechanicallyinferior to normal articular cartilage, even though the histo-logic appearance is often fibrocartilage or even hyaline-liketissue (Ahsan & Sah 1999). Repair tissue generally hassignificantly less proteoglycan and to some extent type IIcollagen than normal cartilage. Additionally, the developmentof subchondral architecture and re-establishment of a tide-mark is often irregular and inconsistent. This creates stressrisers and susceptibility to cartilage deterioration with normaljoint activity. Poor-quallty, relatively short-lived repair cartilagehas led to the development of pharmacologic and surgicalmethods to improve the repair process.

Articular cartilage rarely reforms a functional hyalinesurface after injury. Most simple cartilage lacerative injuriesreach a benign non-healing phase, which remains unchangedover time (Mankin 1982, Hunziker & Rosenberg 1996). Deepercartilage lesions, violating the tidemark and extending intothe subchondral bone plate, result in an improved healingresponse (Campbell 1969). This is largely due to the pro-liferation of undifferentiated mesenchymal cells from thedeeper tissues. In horses, spontaneous healing in cartilagedefects progresses from granulation to fibrous tissue and finallyfibrocartilage (Riddle 1970). The fibrous tissue undergoesprogressive chondrification to form a fibrocartilaginous mass,loosely attached to the original cartilage edges. The subchondralbone plate occasionally reforms to the same approximatelevel as the adjacent undamaged bone, but in cartilage lesionsthat do not involve substantial erosion of the underlyingbone. the reformed subchondral bone plate may be higherthan the surrounding normal bone plate (Frisbie et aI1999).Immediately above the reformed subchondral plate, areas ofcartilage proliferation predominate. The deeper cartilagelayers and surface fibrous tissue generally follow a pattern ofdecreasing cellularity as the defect matures. At 12 months.type II collagen content approaches normal but proteoglycanlevels are only about half that of normal (Howard et aI1994).The phenomenon of matrix flow, an intrinsic repair mechanism.may also contribute to healing of articular cartUage defectsby centripetal collapse of the perimeter of the lesion(Ghadially & Ghadially 1975). In small defects. this canresult in significant reduction in lesion size, but in defectsover 9 mm, matrix flow is proportionally insignificant(Convery et al1972).

Depth of injury (full or partial thickness). the size of thedefect, location in relation to weightbearing or nonweightbearing areas. and the age of the animal. influence the repairrate and resiliency of new cartilage surfaces. The healing ofchondral and osteochondral defects is more complete in younganimals. due to the increased mitotic capacity of chondrocytes,more active matrix synthesis, and closer proximity to thevascular supply in the depths of the articular-epiphysealcomplex cartilage (Madsen et al19 8 3). Examples of improvedrepair capacity are easily seen in the resurfacing potentialfollowing osteochondritis dissecans (OCD) flap removal in

Techniques that enhance the quantity and hyaline charac-teristics of cartilage repair tissue, would allow the surgeon toimprove the long-term outcome when debriding cartilagelesions, particularly in challenging conditions of the stifle,carpus, and shoulder. These techniques should meet severalimportant criteria:

1. be achievable arthroscopically2. result from local manipulations or use of simple transplant

tissues3. be available to surgical specialists with minimal delay

between the diagnosis, decision for surgery, and theinstitution of the surgical repair

4. be reasonably economical

5. be well tested in a research setting, and able to offeradvantages in durability and hyaline quality in the repairtissue

6. be amenable to the variety of shapes and locations ofacute, subacute, and in some instances chronic, cartilagelesions in the joint.

No one arthroscopic system routinely provides all of theseadvantages. Indeed, those with inherent simplicity such ascartilage debridement, forage, and microfracture meet manyof the criteria for simplicity, economy, and minimal delaybetween diagnosis and repair, but provide less assured hyalinecartilage and cartilage durability than many of the morecomplex transplant methods. Techniques for cartilage repairthat are clinically used or have been studied in a researchsetting can be subdivided into two categories: localmanipulative procedures or cell and tissue transplantation

techniques.

Local manipulative procedures

Surgical techniques that rely on simple manipulativeprocedures include:

.cartilage debridement.chondroplasty to remove partial-thickness fibrillation.cartilage reattachment.forage or drilling of the subchondral bone using a

drill to provide a uniform diameter perforationthrough the subchondral plate

.microfracture or micropick, which uses a taperedsurgical awl to perforate the subchondral bone toopen marrow spaces

.abrasion arthroplasty, using a motorized burr to removea uniform layer of eburnated cartilage and bone

.spongiallzation (saucerization) of the subchondralplate to open up larger marrow spaces by removal ofgreater thicknesses of the subchondral bone.

Cartilage debridementSome form of cartilage debridement is common duringarthroscopic surgery. As a simple rule, fibrous interpositional

,,'tissue or exposed loose bone should be removed from full-thickness defects. Debridement should continue down tofirm, normal appearing, subchondral bone plate. Maintainingas much subchondral bone as possible keeps the bone andoverlying cartilage repair tissue contoured to the normalcongruency of the opposing joint surface, thereby enhancingthe chance of healing cartilage tissue persistence. However,the remaining bone must be viable. Crumbly, brownish boneshould always be removed by debridement, using either handinstruments or motorized equipment (Fig. 17.1). At least forthe carpus, the amount of residual bone after debridement isan important parameter in determining the prognosis forreturn to athletic activity (McIlwraith et al19 8 7, McIlwraith1990). Several studies indicate the advantage of removal offull-thickness fibrillated cartilage. However, more debate sur-

rounds the potential advantages of debriding partial-thicknesscartilage defects down to subchondral bone. in efforts toencourage new cartilage formation from subchondral bonecellular and growth factor elements (Baumgaertner et al1990.Hubbard 1996). Consensus appears to favor not debridingpartial-thickness fibrillated cartilage, but rather leaving itattached to the calcified cartilage and underlying bone(Mcllwraith 1990). Partial-thickness defects have beenshown to remain physically unchanged for at least 2 years(Mankin 1982). Conversely, some symptomatic benefit forseveral months can be derived from chondroplasty of theobviously fibrillated portion of partial-thickness defects,

Repair Methods

while leaving perpendicular cartilage defect walls (Fig. 17.2).A controlled study in dogs indicated the benefit of perpen-dicular cartilage walls following debridement, compared tobeveled edges, which tended to increase the overall dimensionof the healing defect (Rudd et al198 7).

Exposed subchondral surfaces can be smoothed eitherwith hand tools, which include curettes, rasps, and rongeurs,or with motorized burrs. Several types of burr heads areavailable, varying from spherical to oval acromioplasty ornotchplasty blades, which have an elongated profile formaximum bone removal effect (see Chapter 2). Hand tools aregenerally preferred to avoid excessive bone loss; however, forlarge areas of irregular hard bone, a burr may expedite theprocedure and provide a better end result. Since the need for

which is described in more detail later (Thompson 1975,Kim et al 1991). In summary. chondroplasty reduces thepossibility of damaged cartilage leaching degraded cartilagematrix fragments, including collagen, proteoglycan, andcellular components to the synovial fluid. where theyincrease synovitis and concurrent lameness (Thompson

1975).Full-thickness cartilage lesions are debrided to removeresidual

portions of the calcified cartilage layer, which tendsto retard the development of well-attached cartilage repairtissue

from the subchondral bone and surrounding cartilage.The most appropriate tools for cartilage debridement include

a series of spoon and ring curettes that allow adequate removalof residual fibrous areas attached to the subchondral bone

substantial bone removal is low. an inventory of a single burrtype is recommended.

ChondroplastyResection of the protruding surface strands of partial-thickness cartilage fibrillation has been promoted as amechanism to reduce cartilage-derived detritus entering thesynovial environment (Thompson 1975. Childers & Ellwood1979. Kim et al1991. Altman et al1992). Motorized synovialabraders are used to smooth the surface of the more seriouslydamaged cartilage. The residual cartilage then presents amore uniform non-clefted surface, which may be moredurable and incites less synovitis than the large surface areapresented by multiple strands of fibrillated cartilage. Theconcept seems simple. but there is a paucity of evidencedocumenting any discrete benefit. either in reducing synoviallevels of fragmented proteoglycan and collagen or in abrogatingthe symptoms of synovitis. Despite this, the technique hasempirical benefits and has been used in equine arthroscopyfor trimming extensive areas of partial-thickness fibrillatedcartilage. The most frequent site for application in the horse isthe stifle (Fig. 17.3). TrocWear ridge OCD in mature horses(>3 years) is often accompanied by fibrillation of the sur-rounding cartilage and the patella. Chondroplasty has beenused to trim these areas to smooth articular cartilage andseems to reduce the incidence of persistent effusion whenthese horses re-enter competition. No controlled clinical orexperimental data support chondroplasty in the horse. so itsuse remains controversial. It may be preferable to doingnothing. but the resection depth should only involve thefibrillated surface and not be aggressively pursued down tothe subchondral bone, since the ensuing repair tissue rarelyhas the hyaline characteristics of the original deep cartilagelayers that were resected.

Chondroplasty cannot be efficiently performed withoutsharp motorized abraders. Disposable cutting heads arerecommended. Attached suction is also helpful in drawingand holding the cartilage fronds into the shaver blades. A"whisker" technique is used to avoid penetration of the intactdeeper layers of cartilage. Benefits in man have been describedfor months to years after chondroplasty; however. as much as6 months symptomatic relief has also been attributed tosynovial washout using a saline lavage (Hubbf1rd 1996).

worked satisfactorily on large flaps in the fetlock, hock andstifle, where undulating OCD cartilage has been salvaged bypinning to th~ underlying bone (Nixon et al 2003a). Theintervening fi~rosis between cartilage and bony defect shouldbe removed if the procedure can be performed withoutdisturbing remaining perimeter attachment. A 1.2 rom K -wireis then used to drill through the cartilage flap and into theunderlying bone (Fig. 17AA). With changes in the degree offlexion of the joint, multiple K-wire perforations can be made,all perpendicular to the surface. The soft tissues are protectedby insertion of the K-wire through an arthroscopic guidecannula. The kit also contains five 40 rom long x 1.3 romdiameter pins, each of which can be cut in half to provide twopins approximately 20 rom in length. Except in cases withextremely deep subchondral defects. these pins adequatelysecure the OCD flap. For deeper lesions, pins can be cutlonger. up to the entire 40 rom pin. After carefully drilling theK-wire to end 1 rom short of the anticipated pin length. the

Cartilage reattachmentSome cartilage flaps in the stifle. hock, and fetlock can bepotentially salvaged and reattached (Nixon et al2003a). Whilenot common, an OCD cartilage flap that is relatively smoothand has not detached on its entire perimeter can be elevatedand the underlying necrotic cartilage and marrow fibrosisdebrided. The flap can then be replaced and secured withpolydioxanone (PDS) pins (OrthoSorb, Ethicon-Johnson &Johnson) (Fig. 17.4), or PLLA tacks (Chondral darts, Arthrex.Naples, FL). Importantly, the OCD flap must be worthreattaching, which requires a smooth congruous surface,minimal fibrillation, and some perimeter continuity. This has

PDS pin is inserted down the cannula and pushed into placeusing the obturator (see Fig. 17.4B). Approximately 1 mm ofpin is left protruding from the surface of the cartilage so it canbe flattened level with the articular surface to make a securinghead to the PDS pin. Any excess pin can be removed witha biopsy punch rongeur or other severing rongeur (seeFig. 17 AC). Multiple pins are inserted approximately 10 mmapart so that the entire cartilage flap is securely reattached tothe subchondral bone. As few as 2 and as many as 10 PDSpins have been inserted (Nixon et al 2003a).

Use of the multi-shot chondral dart system (Arthrex,Naples, FL) for simultaneous multiple anchoring with bidi-rectional barbed pins is being explored, and appears a satis-factory alternative to PDS pins. Rapid resolution of effusionand subchondral bone lysis on radiographs is a consistentfeature (Fig. 17.5), and reformation of the subchondralcontour was complete in all but 2 of 16 joints in 12 horses(Nixon et aI2003a). This compares favorably to debridementof OCD lesions, which generally leaves a depressed subchondralbone plate at the lesion site. Eleven of the 12 horses were not

cartilage repair. It is simple and inexpensive. However, in acontrolled study using arthrotomy approaches, it did notprovide superior healing in defects on the equine third carpalbone (Vachon et aI1986). Similarly, it did not benefit healingof partial-thickness cartilage defects in the same third carpalbone model (Shamis et al1989).

Subchondral bone forage or drilling was introduced intohuman arthroscopy in the 1960s (Pridie 1959, InsalI1974).Since then it has been frequently used to improve cartilagequality following chondromalacia of the patella (Childers &Ellwood 1979). Historically, the most frequent site forsubchondral bone forage in the horse was the sclerotic rimassociated with subchondral cystic lesions (Mcllwraith 1983,White et al1988). The use of this technique has diminished, asreports of cyst enlargement subsequent to forage have beenpublished (Howard et al 1995), and surgeons have founddifficulty in arthroscopically making drill holes that areperpendicular to a defect. The technique has largely beenreplaced by microfracture.

Microfrocture

The use of microfracture. or micropick as it has been referredto in equine arthroscopy, has many of the advantagesassociated with forage, including focal penetration of thedense subchondral plate to expose defects to the benefits ofcellular and growth factor influx, as well as improvinganchorage of the new tissue to the underlying subchondralbone and to some extent the surrounding cartilage (Rodrigoet al 1994, Frisbie et al 1999, Breinan et al 2000). Thesimplicity of microfracture comes from the use of a taperedawl (Unvatec, Largo, FL; Arthrex, Naples, FL), instead of aparallel-sided twist drill. Using the awl abrogates the need forpowered instrumentation to perforate the subchondral bone.giving additional control over the placement of theperforation, and also allowing the formation of a tapered entryto the subchondral marrow spaces. The microfracture awlsshould penetrate the subchondral bone deep enough (2-4 mm)to provide ready access to the marrow spaces, therebymaximizing cellular and anabolic growth factor delivery(Fig. 17.6). The microfracture awl also tends to make a craterin the subchondral bone. which may playa role in betterattachment of, the cartilage repair tissue (Lee et al 2000).Microfracture, 'holes are generally placed 3-5 mm apart andcover the entire debrided area in a cartilage lesion (seeFig. 17.6). It is also important to microfracture the sub-chondral bone on the perimeter of the cartilage lesion toencourage new tissue at the junction of repair tissue andresidual cartilage. The technique has become popular inhuman arthroscopy (Rodrigo et a11994, Blevins et a11998,Steadman et al2001. 2002), and is now frequently comparedto chondrocyte transplantation as one of the two mostfrequently employed techniques to improve cartilage healing.One experimental study in the horse documented improve-ments in the quantity of tissue and the hyaline quality of thecartilage (collagen type n content) at 4 and 12 months aftermicro fracture of full-thickness cartilage defects (Frisbie et al1999). Improvements in early gene expression of cartilage

lame, and it appeared that reattachment was a valuableoption to salvage the dissected hyaline cartilage flap inselected cases.

Forage

Forage or subchondral bone drilling has been explored in thehorse. The rationale is to perforate the subchondral bone andallow entry of subchondral marrow elements. vasculature.and growth factors to the defect, which then contribute to

Abrasion arthroplasty

Abrasion arthroplasty uses a motorized burr to resect auniform layer of residual cartilage and eburnated subchondralbone Gohnson 1986. 2001). Eburnated bone is often charac-terized by a surface layer of non-viable bone Gohnson 2001).which forms a barrier to effective cartilage repair. Abrasionarthroplasty. a.it was originally conceived Gohnson 1986).removes this superficial layer of dead subchondral plate.thereby exposing vascular tufts from the deeper marrowspaces. In addition. it provides access to a viable pool ofmarrow-derived stem cells that could participate in cartilagerepair. Use of motorized equipment is necessary due to thesclerosis associated with subchondral bone eburnation. Theresult is a coalescing group of fibrocartilaginous tissue tuftsGohnson 1986. 1991. Menche et al1996). Although. it hasbeen used to a limited extent. particularly for areas ofeburnation of the trochlear ridges of the talus. widespreadexperience with this technique in horses is lacking. and thereare no published reports documenting other possible sites forabrasion arthroplasty. The utility of arthroplasty has beenreduced by the introduction of marrow stimulating tech-niques such as micro fracture. which perforate the sub-

specific markers were evident within 8 weeks of microfracture(Frisbie et aI2003).

The technique clearly has advantages over forage andtransplantation methods, including ease of application usingarthroscopy, use of a simple hand tool. the relative economiesof the equipment required, the simplicity and minimalplanning required to use the technique. and the apparentincrease in cartilage repair tissue that deve~ps after theprocedure. ...

Results of microfracture in equine clinical syndromeshave not been published. However, individual experienceswith micro fracture have included focal and severe cartilagedefects on the carpal bones, femoral condyles and trochlearridges. proximal sesamoids and distal metacarpal/metatarsalcondyles, and the trochlear ridges of the talus (see Fig. 17.6).Anecdotal evidence of improved cartilage healing hasbeen derived from the use of microfracture at each of thesesites. Further case numbers and comparative studies arerequired before a definitive recommendation can be madefor its use. Of the available local manipulative proceduresthat follow debridement of cartilage lesions, microfractureappears to have the most benefit with the least cost and

complexity.

chondral bone plate at multiple sites over eburnated ordebrided cartilage regions and allow reformation of cartilagerepair tissue while still maintaining the subchondral platecontour.

Spong;al;zat;on

Spongialization can be considered an extension of abrasionarthroplasty. since extensive areas of the subchondral boneplate and overlying cartilage are removed (Ficat et aI1979).Resection extends through the subchondral bone. essentiallyexposing the defect to the marrow spaces that then parti-cipate in cartilage repair. Given the benefits to maintaining sub-chondral bone architecture. we do not consider there is anyindication for the use of spongialization in equine arthroscopy.

for focal cartilage injury in the knee has been reported(Niedermann et a1198S, O'DriscoII1998, 1999). On balance,the disadvantage of an arthrotomy for insertion of periostealgrafts in man is not outweighed by the potential benefits inhyaline cartilage. Additionally, in an equine study, periostealtransplants to the stifle occasionally induced vascularizationof the healing cartilage, which led to exuberant tissue andmineralization in the repair, both of which were detrimentalto the formation of durable hyaline cartilage (Nixon et al2002, unpublished data).

In other equine studies, autogenous periosteal transfer tothe radial carpal bone provided no additional advantage todefects healing spontaneously (Vachon et a11991a, 1991b).Moreover, there was a tendency for synovial pannus andadhesions to overwhelm the healing defects (Vachon et al1991b). In other research studies, the application of auto-genous periosteal grafts as a mechanism to secure autogenouschondrocyte grafts in full-thickness cartilage defects providedbetter cartilage repair than periosteal graft alone (Breinan etal 1997), and is probably the only widespread clinicalapplication of periosteal grafts in cartilage repair in man(Brittberg et al 1994). In horses, there are no reports ofsuccessful clinical application of periosteal grafting in

cartilage repair.

Transplantation procedures

In mature horses most debriding and marrow stimulatorytechniques result in fibrocartilage formation with modest bio-mechanical capabilities. The use of supplemental free cells.various vehicles containing cells. or entire tissues such asperiosteum or cartilage grafts have been advocated to improvethe modest impact that these local manipulative procedureshave on both the quality and quantity of cartilage repairtissue. Transplantation procedures can be classified accordingto the origin of transplanted tissue: (1) periosteal trans-

plantation. (2) perichondrial transplantation. (3) autogenouscartilage (articular. sternal. or auricular) transplantation.(4) osteochondral transplantation. (5) chondrocyte trans-plantation. and (6) pluripotent stem cell transplantation.

There is a considerable body of literature that describes thepotential advantages derived from transplantation of wholetissues. The disadvantages with these methods and the tissuesthey transfer predominantly hinges on the limited applicationby arthroscopic means. Arthrotomy is required for insertionof periosteum. perichondrium. intact cartilage. and osteo-chondral grafts. Similarly. tissue-engineered cartilage analogessuch as chondrocytes cultured on collagen. polygiycolic acid(PGA). or PGA/polylactic acid (PGA/PLA). or newer syntheticmaterials such as hyaluronan membranes. are also difficult orimpossible to implant arthroscopically. This serious practicallimitation has tempered interest in using thesrimplants.

Perichondrium

Several research groups have studied the use of perichondriumrather than periosteum for improved cartilage repair (Ohlsen& Widenfalk 1983. Kwan et al 1989. Coutts et al 1992.Bruns et a11992. Ritsilaet a11994. Bouwmeester et aI2002).While these tissues behave similarly to periosteum. variousinvestigators considered they were more programmed towarda chondrocyte lineage. and should hold special benefits forcartilage repair. In a study comparing free grafts of perichon-drium to periosteum implanted in equine joints. perichondriumdid not produce significant cartilage (Vachon et al 1989).Perichondrial grafting holds few benefits over other techniques.and is rarely mentioned in clinical applications in horses orman (Ritsila et a11994. Bouwmeester et aI2002).

Osteochondral Grafts~

The use of o~teochondral autograft and allograft has beenthrough several periods of clinical interest. Originally,autogenous osteochondral shell grafts were favored becauseof the secure attachment to the recipient bed afforded by thebony portion of the graft. The overlying cartilage was wellattached at its base since it was harvested as an osteo-chondral composite, and the graft also had minimal gappingat the cartilage perimeter. However. research and clinicalevaluations were tempered by the limited availability of auto-genous osteochondral graft and the donor site morbidity. Fewsites in man or animals can sacrifice considerable areas of ajoint for donation as osteochondral grafts. The use of allo-graft osteochondral shell grafts was designed to overcomethese limitations. Several investigators have found utility inthe use of fresh osteochondral hemiarthroplasty shell allografts

PeriosteumAutogenous periosteal transplants have improved the

quality of repair tissue in various animal models (Rubak

1982, O'Driscoll & Salter 1984, 1986, Hulse et al 1986,

O'Driscoll et a11986, Moran et aI1992). Moreover, high-

quality hyaline cartilage was produced when transplantation

was combined with the use of continuous passive motion in

rabbits. Subsequent application in man has been limited to

carefully selected cases over the last 10 years (Niedermann et al

1985, O'Driscoll 1999). However, the surgery is extensive

and includes harvest of tibial periosteum and arthrotomy for

suture attachment of the periosteal flaps to irregular-shaped

lesions in the human knee. Application of periosteal grafts

created widespread instability and joint pain (Meyers et al

1989, Ghazavi et al1997, Chu et a11999. Aubin et a12001.

Gross et al 2002). However, it should be stressed that these

are not dowels but entire femoral condyle shell grafts.

The immunogenicity with allografts, particularly the

osseous component is also of concern (Elves & Zervas 1974,

Strong et al1996).

More recently. mosaicplasty. using autogenous osteochondral

dowel grafts. has become popular (Hangody et al1997. 1998.

2001a, Jakob et al 2002). This technique has recently been

arthroscopically performed in the human knee. and involves

harvest of osteochondral dowels from less weightbearing

regions of the same joint, and insertion of these dowels to

reconstruct a relatively congruous joint surface (Hangody et al

1998. 2001a). Considerable research data support the clinical

application of osteochondral dowel grafting. The technique

has been used successfully in the horse (Bodo et al 2000).

Other investigations of autogenous and allograft osteochondral

dowel transfer in horses have yielded mixed results (Hurtig

1988. Hurtig et al2001). The technical difficulties associated

with careful graft harvesting and the precision and crafting

needed for heterotopic graft insertion in the recipient bed have

detracted from wider clinical application (Pearce et aI2001).

Additionally. empty spaces that naturally form between

inserted osteochondral dowels heal poorly and allow synovial

fluid entry to the bone tunnels of adjacent dowels.

Several instrument systems are available for the harvest

and implantation of osteochondral dowels in man and animals.

These include the mosaicplasty system (Acufex -Smith &

Nephew. Andover. MA). the osteochondral autograft transfer

system (OATS -Arthrex. Naples. FL), and the consistent osteo-

chondral repair system (COR -Innovasive), that have been

marketed for use in man. Frequently. "mosaicplasty" is used

as an umbrella term for all of these techniques, despite its

trademark use for the Acufex -Smith & Nephew instrumen:'

tation. The benefits of autogenous osteochondral dowel transfer

include immediate weightbearing capabilities. relatively good

integration of the bony portion of the dowel. and the long-

term data available from clinical trials (Hangody et al2001b,

Mendicino et al 2001. Jakob et al 2002). In horses. the

arthroscopic application of osteochondral dowel transfer is

cumbersome. harvest of the osteochondral plugs can be

challenging due to the optical aberrations associated with

arthroscopic viewing, and insertion of the osteochondral

dowels can be technically demanding. Until the technical

difficulties associated with dowel insertion can be further

minimized. widespread use in horses is likely i~ be limited.

Experimental work suggests mosaicplasty techniques also

become more difficult in mature horses (Bodo et al 2001).

Despite this. a case report of mosaicplasty for repair of a

subchondral bone cyst of the medial femoral condyle in a

horse has been published (Bodo et aI2000).

--articular cartilage biopsies are harvested arthroscopicallyfrom minimally weightbearing regions of the injured knee,propagated ex vivo in cell culture, and later implanted underan autogenous periosteal tissue patch (Brittberg et al1994).The indications for the procedure include previously failedsurgery, large lesions, and minimal secondary osteoarthriti~(Brittberg et al 2001, King et al 2002). These indicationsinclude extensive focal defects and osteochondritis dissecans(Robert & Bahuaud 1999, Peterson et al 2000,2002). Thedelivery of cells requires an arthrotomy, and the harvest andsuture attachment of a periosteal patch is tedious and tech-nically demanding. Both factors complicate the surgery aswell as the postoperative course. There are still several un-resolved questions, including the ideal number of chondro-cytes to transplant and most particularly the role of theperiosteum in the technique. The periosteum has been shownby others to contribute to cartilage healing (O'Driscoll1999).One study compared chondrocyte transplantation securedwith a periosteal patch to defects treated with periostealpatches without chondrocyte implantation, and found nodifference between the healing tissue after a year (Breinanet al19 97). Clinical outcome in multiple studies in man havereported good to excellent results, with 80-90% return topain-free function for femoral condyle defects and slightlylower success rates for lesions on the patella (Minas 1998,2001, Richardson Evans et al1999, Minas & Peterson 1999,Peterson et al2000, 2002. Minas & Chiu 2000, Brittberg et al2001, Lindahl et al 2001). Long-term studies are becomingavailable for patients treated with autogenous chondrocyterepair, one of which shows that 84% of patients had asuccessful outcome from 2 to 9 years after the procedure(Richardson et al1999, Peterson et al2000, 2002, Brittberget al2001, Minas 2001).

In horses, chondrocyte implantation techniques have beenexamined in a variety of matrix carrier vehicles (Hendricksonet al1994, Sams & Nixon 1995, Fortier et aI2002a). Initialresearch trials indicated the significant effect of chondrocyteimplantation using a fibrin vehicle (Hendrickson et aI1994).Subsequent methods to enhance the matrix vehicle, usingtissue-engineering approaches with collagen matrix scaffolds,did not provide a satisfactory improvement in repair (Sams &Nixon 1995, Sams et al 1995). The addition of anabolicgrowth factors was initiated to bolster the matrix elaboratedby transplanted chondrocytes. Initial studies used vehiclescontaining growth factors, but no cells, with the expectationthat a repositofH of a growth factor would enhance repairtissue from pluclpotent cells arising from the subchondral bed(Nixon et aI1999). Insulin-like growth factor-1 (IGF-1) hasbeen extensively evaluated for its effect on chondrocyte activity(Luyten et al1988, Nixon et al 1998, Fortier et al 1999),although other growth factors have also been found tostimulate proliferation, migration, matrix synthesis, and dif-ferentiation. Many of these growth factors, including basicfibroblast growth factor, transforming growth factor-g (TGF-g),and epidermal growth factor, induce beneficial effects tocartilage healing (Mankin et al1991, van den Berg 1995,Trippel et al1996, O'Connor et al2000). Local treatment of

Chondrocyte transplantation

Autogenous chondrocyte implantation is one of the few FDA-approved tissue engineering techniques to treat articular

ubiquitous matrix that further isolates them from the hostimmune response. Comparison of studies in the horse clearlydocumented the benefits of allograft cells compared to defectswithout cells (Hendrickson et a11994). Allograft chondrocytepersistence has also been assessed in horses, using a markerof male cells (the SRY gene) to track the survival of maleallograft transplants in female recipients (Ostrander et al2001, Hidaka et al 2003). This polymerase chain reaction-based assay indicated persistence of equine allograft cells at8 months, ranging from 0 to 28% (Hidaka et al 2003). Mostassays of the persistence of allograft cells in more vascularizedlocations indicate rapid cell loss Oackson & Simon 2002).Despite cell loss, enhanced repair can be induced, either bythe initial impact of the allograft cells, or the later enhancedelaboration of paracrine growth factors and matrix that mayimprove the quality of cartilage repair. Clearly, however, anautogenous cell would be an advantage. Recent studies in thehorse, using autogenous chondrocytes seeded onto a collagenmembrane and inserted via arthrotomy, have yielded en-couraging results (Frisbie 2003, unpublished data). Use ofbone marrow-derived pluripotent mesenchymal stem cells(MSCS) is one solution to the limited availability of predeter-mined chondrocytes.

Pluripotent mesenchymal stem cell transplantation

The use of a pluripotent cell to enhance cartilage repair hasbeen investigated for several years. Initial studies in the rabbitindicated MSCs could enhance cartilage repair (Wakitani et al1994, Grande et al 1995, Johnstone & Yoo 1999, 1m et al2001). Follow-up work in small animals demonstrated thatMSCs can be partially induced down chondrocyte lineages(Butnariu-Ephrat et aI1996). Studies in the horse indicatethat, bone marrow-derived MSCs can be harvested an4icultured for sufficient time in defined media to differentiatetoward a chondrocyte lineage (Fortier et a11998f. However,in-vivo studies in the horse report little advantage after8 months in a femoral trochlear ridge cartilage defect model(Wilke et al2001). Moreover, bone marrow-derived stem cellsfrom horses are tedious to culture, and accumulation ofsufficient numbers to graft large articular defects can take upto a month. Additionally, the yield from mature horses(representing the majority of a clinic caseload) is reducedover yields fr~m immature animals, making the accumu-lation of sufficient cells for grafting age-dependent butgenerally very slow (Fortier et al 1998, Huibregtse et al2000). Overcoming these limitations will require furtherresearch before this source of cells becomes a practicalreplacement method for fully differentiated chondrocytes.

chondral or osteochondral defects with growth factors hasthe potential to stimulate a more durable and hyaline-likerepair, provided the defect penetrates to the level of the sub-chondral bone, Despite the interest in many different growthfactors, IGF-1 has the most potential to provide practicalresults in cartilage repair (described in more detail later).Studies in the horse indicate that IGF-1 combined withchondrocytes results in superior cartilage repair comparedwith other cell-based methods for repair (Fortier et aI2002a).

Practical application of chondrocyte and growth factortransplantation techniques is being pursued in the horse. Anintegral part of chondrocyte implantation is the developmentof a banked source of allograft chondrocytes. Use of allograftcells raises questions concerning the immune response.Several studies document an immune reSponse to thechondrocyte cell wall, which is both predictable and aggressive(Moskalewski et a11966, Elves 1974, Gertzbein et a11977,Kawabe & Yoshinao 1991, Lance et al 1993). However,chondrocytes implanted in vehicles, such as fibrin, hyaluronan,or synthetic composites. are immediately protected from theimmune response (Heyner 1969). Additionally, chondrocytesare somewhat unique in that they are implanted in arelatively poorly vascularized region. Synovial fluid bathesthe surface of cartilage repair areas, and the only direct accessto vascularity comes through the defect base. To this end,defects that do not penetrate the subchondral bone plate, andare implanted with chondrocytes in an attachment vehicle,have some immediate protection against the immunecascade. Furthermore. chondrocytes rapidly elaborate a

Growth factorsSeveral naturally occurring polypeptide growth factors playan important role in cartilage homeostasis. The differentiatingand matrix anabolic promoting activity of IGF-1 and TGF-Bare particularly important in counteracting the degradatoryand catabolic activities of cytokines, serine proteases.. andneutral metalloproteases (Fortier et al 1997. Nixon et al1998). The manipulation of this balance in disease conditions

such as arthritis and acute cartilage injury may be possible byexogenous administration of IGF-l and TGF-B (Tyler et al1989.Nixonetall998. 1999, Fortier et alI999). In-vitro chondro-cyte monolayer and cartilage explant culture studies showIGF-l and TGF-B generally stimulate matrix elaboration andmitogenic effects (Fortier et a11997, Frisbie & Nixon 1997.Nixon et aI1998). Three-dimensional culture assessment ofthe impact of these same growth factors on equine chondro-cyte metabolism. using fibrin gels to provide a stable suspensionculture resembling cartilage matrix (Fortier et aI1999), alsoconfirmed enhanced proteoglycan and collagen synthesisand resulted from exposure to IGF-l concentrations of50-100 ng/ml and TGF-B levels of 5-10 ng/ml (Fortier et al1997. Fortier et alI999). Further studies in the horse havelargely focused on IGF-l, since TGF-B was toxic at moderateconcentrations and IGF-I was stimulatory to chondrocytemetabolism. even when present in excess concentrations(Fortier et al2002b). In-vivo investigations of articular repairfollowing TGF-B administration also showed synovitis andosteophyte development. both of which are alarming featuresof TGF-B use in these animal studies (van den Berg et al199 3.van Beuningen et a11994. van den Berg 1995). Given theseresults. IGF-l was selected as a suitable growth factor for in-vivo studies in the horse. Slow-release delivery of IGF-l withinthe cartilage defect. to facilitate matrix production in localand transplanted chondrocytes, provides a mechanism forenhanced cartilage repair (Nixon et alI999). Elution studiesusing IGF-l-laden equine fibrin indicated that stimulatorylevels of IGF-l (greater than 50 ng/ml) remained for up to3 weeks following an initial loading dose of 2 5 ~ (Foley &Nixon 1997). In-vivo evaluation of a fibrin vehicle loadedwith 2 5 ~g of IGF-l and polymerized in situ in cartilage lesionSin the femoropatellar joints, showed improved cell populationwith a more cartilage-like architecture after 6 months (Nixonet alI999). However. markers of hyaline cartilage such astype II collagen had increased to only 47%. far short of the90% expected in normal articular cartilage. Nevertheless.simple fibrin vehicle grafts used in control stifles did notsignificantly enhance healing. with mean type II collagencontent of 39%, similar to the healing in empty full-thicknessdefects (Hendrickson et alI994). Other studies using injectedcombinations of IGF-l and pentosan polysulfate showattenuation of the symptoms of synovitis in osteoarthritismodels in dogs (Rogachefsky et alI993). In geiIeral, IGF-lseems to have better application in combination withchondrocyte grafts. where more complete cartilage repairdevelops (Fortier et al 2002a). Evaluation of stifle lesions 8months following implantation of a mixture of chondrocytesand 25 ~ of IGF-I. showed considerably improved jointrepair, with 58% type II collagen and better cartilageintegration at the defect edges (Fortier et al 2002a).

Clinical applications of chondrocytetransplantationClinical resurfacing trials in horses have used a regimen ofautogenous fibrin laden with 50 IJ.g of IGF-l and 30 millionchondrocytes per ml of fibrin.

Preparation of autogenous fibrinogen. The horse'sjugular vein area is aseptically prepared for whole bloodcollection. A commercial 500 ml blood pack containing acidcitrate dextrose (Travenol) is used for whole blood harvest.The blood cell~are allowed to settle in a refrigerator forseveral hours before titrating off the plasma. The cells arethen discarded and the plasma aliquoted to 50 ml centrifugetubes prior to freezing at -80°C overnight. The plasma is thenallowed to slowly thaw in a refrigerator for 30-36 hours, andthe fibrinogen-rich cryoprecipitate collected by centrifugationat 3000 g at O°C in a swinging bucket centrifuge. Approxi-mately 0.5-0.75 ml of cryoprecipitate fibrinogen can becollected from each 50 ml tube of plasma (Fig. 17.8A). As aprecaution against contamination at collection or handling,a bacterial culture is submitted prior to using the product forcell grafting. Fibrinogen can be stored refrigerated for severaldays, or frozen for later use.

Chondrocyte banking. Chondrocyte isolation requiresthe services of a laboratory equipped for cell culture. Allo-graft chondrocytes are harvested from foals destroyed for

to the end of a hemostat. Drying of the subchondral bed andsurrounding intact cartilage allows better application of thenaturally adhesive properties of fibrin. The polymerizing liquidnature of fibrin allows contouring of the cell transplant to theirregularities of many joint surfaces (Fig. 17.9).

Clinical application of chondrocyte grafting in horses hasincluded traumatic cartilage lesions of the third carpal bone,fetlock metacari'al condylar fractures, and OCD or subchondralcystic lesions qF the fetlock (14 horses) and stifle (43 horses).Chondrocyte augmentation following third carpal bone slabfracture repair and shoulder OCD debridement have resultedin few horses capable of returning to athletic work. However,results for stifle OCD and subchondral cyst grafting of thestifle and fetlock have been generally good. Complete radio-graphic filling has occurred in more than half of the stiflesubchondral cysts radiographed at or beyond 12 months post-operatively (Fig. 17.10), and 73% of stifle subchondral cysts,including failures of previous simple debridement alone, havebeen in athletic work for a minimum of 2 years. Similarly,fetlock subchondral cYsts have been treated using arthroscopicextirpation and grafting (Fig. 17.11). Radiographic filling ofthe fetlock cysts can be slow, and residual deeper lytic regionscan remain despite athletic performance (Fig. 17.12). All but

noninfectious disease, most frequently irreparable fracturesor severe congenital deformities. Cartilage slices are harvestedaseptically from the stifle, shoulder, or elbow, and the cellsisolated from their matrix by overnight collagenase digestion(Nixon et alI992). The cells are then counted and dimethylsulfoxide (DMSO) added to the culture medium prior to freezingand storage in liquid nitrogen. When the cells are required,48 hours lead time is needed to thaw the cells and then brieflyculture to allow removal of any dead cells, before collectionfor use in surgery.

Clinical application. At the time of surgery the chondro-cytes are mixed with fibrinogen and stored at 4°C. IGF-l(50 flg) is added to 250 or 500 units of activated thrombin, toprovide a two-component system for immediate injection.Thrombin is obtained from Sigma-Aldrich Corporation(Fig. 17.8B), and the lyophilized powder reconstituted withcalcium chloride (40 mmol), and sterilized by filtrationthrough a 0.2 ~ millipore syringe filter. At surgery, the poly-merization process develops immediately upon injection ofthe two components into the articular defect (Fig. 17.8C).Arthroscopic lesion debridement is followed by gas insuffiationfor the few minutes required for fibrin injection. This allowsdrying of the defect using Q-tips or surgical sponges applied

two horses more than 12 months postoperative have enteredathletic work. Both of these cases had evidence of remodelingdue to osteoarthritis at the time of grafting.

studies with autogenous chondrocytes cultured on collagenmatrix allow implantation of a soft composite, and the resultshave been encouraging. Allograft chondrocytes can potentiallyoffer younger, more metabolically active cells, which havebetter replicative capacity. However, as methods to inducechondrogenesis in MSCs become more efficient, use of an auto-genous cell of bone marrow origin that has been extensivelyprogrammed using a combination of growth factor peptideand gene modulations may provide a differentiated chondro-cyte (Nixon et al 2000). Moreover, the addition of anabolicgrowth factors to the cell mixture, including IGF-l and severalfrom the transforming growth factor superfamily, particularlyBMP7 and/or BMP2, will promote long-term matrix synthesisand chondrocyte persistence (Nixon et al 2000). Studies ofIGF-I and BMP7 gene enhanced chondrocyte function inequine models suggest both stimulate extraordinary earlyhealing, be~nd that seen in unstimulated chondrocyteimplanted cartilage defects (Goodrich et al2002, Hidaka et al2003). Long-term provision of an anabolic growth factor(IGF-I) and an anticatabolic factor (1L-1 receptor antagonist)using gene therapy has shown encouraging results, at least invitro (Nixon et al 2004b).

Future directions

Numerous tissue-engineered cartilage composites have beendeveloped for cartilage repair during the past 10 years, usingthe concept of artificial implantable hyaline-like cartilage.None of these techniques have entered clinical practice. Thepredominant reason for failure with preformed cartilageanaloges is the lack of integration of the cartilage-likematerial to the subchondral bone and, most particularly, thesurrounding cartilage. Most composites that begin to take onthe biomechanical characteristics of cartilage before integ-ration will fail. For this reason, soft, self-polymerizing andself-contouring grafts that are placed as liquids or softcomposites and attach to the surrounding tissues are morelikely to succeed. These grafts accumulate intrinsic mechanicalcompetency as the cells synthesize their own matrix, whichallows a better stress transition to adjacent cartilage. Equine

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Peterson 1, Minas T, Brittberg M, Nilsson A, Sjogren-Jansson E,Lindahl A. Two- to 9-year outcome after autologous chondrocytetransplantation of the knee. Clin Orthop 2000; 374: 212-234.

Pridie KH. A method of resurfacing osteoarthritic knee joints. J BoneJointSurg 1959; 41B: 618.

Richardson]B, Caterson B, Evans EH, Ashton BA, Roberts S. Repairof human articular cartilage after implantation of autologouschondrocytes. J Bone Joint SurgBr 1999; 81:1064-1068.

Riddle WE. Healing of articular cartilage in the horse. J Am Vet MedAssoc 1970; 157:1471-1479.

Ritsila VA, Santavirta S, Alhopuro S, et al. Periosteal and peri-chondral grafting in reconstructive surgery. Clin Orthop 1994;302:259-265.

Robert H, Bahuaud J. Autologous chondrocyte implantation. Areview of techniques and preliminary results. Rev Rhum Engi Ed1999; 66: 724-727.

Rodrigo JJ, Steadman JR, Silliman ]F, Fulstone HA. Improvement offull-thickness chondral defect healing in the human knee afterdebridement and microfracture using continuous passive motion.AmJ Knee Surg 1994; 7: 109-116.

Rogachefsky RA, Dean DD, Howell DS, Altman RD. Treatment ofcanine osteoarthritis with insulin-like growth factor-1 (IGF-1)and sodium pentosan polysulfate. Osteoarthritis Cart 1993; 1:105-114.

Rubak JM. Reconstruction of articular cartilage defects with freeperiosteal grafts. An experimental study. Acta Orthop Scand1982; 53: 175-180.

Rudd RG, Visco DM, Kincaid SA, Cantwell lID. The effects of bevelingthe margins of articular cartilage defects in immature dogs. VetSurg 1987; 16: 378-383. ,,~.

Sams AE, Minor RR, Wootton JAM, Mohammed H, Nixon AJ. Localand regional matrix responses to chondrocyte laden collagenscaffold implantation in extensive articular cartilage defects.Osteoarthritis Cart 1995; 3: 61-70.

Sams AE, Nixon AJ. Chondrocyte-laden collagen scaffolds forresurfacing extensive articular cartilage defects. OsteoarthritisCart 1995; 3: 47-59.

Shamis LD, Bramlage LR, Gabel AA, Weisbrode S. Effect ofsubchondral drilling on repair of partial-thickness cartilage

bone degeneration 94bone density in third carpal bone 104bone scintigraphy. temporomandibular

joint (TMJ) 441bulb pump 11-12burrs. round or oval 22bursae

acquired 409calcaneal 409-13clinical application 421-4communication between 410congenital 409contamination and infection 419dissection 410distention 410endoscopic anatomy 411-12.420endoscopic view with arthroscope close

to entry portal and angledproximally 412

endoscopic view at apex of tuber 412intertubercular (bicipital) 414-19lateral endoscopic approach 411medial approach 411osteolytic lesions of calcaneal tuber

412-13podotrochlear (navicular) 419-25proximal endoscopic view 411 -

bursoscopy 409-26clinical application 412-13.417-\9general technique 409overview 409

arthroscopyadvantages of 3complications in man 447-8development 1-3early applications 1-3evolution 1-3general technique 31-46historical review 1-3human 15human knee 34intraoperative problems 448-51joint surgery 2learning technique 45overuse and abuse 3overview 1-3positioning problems 453-4see also diagnostic arthroscopy; surgical

arthroscopy; and under specific

applicationsarthrotomy 1articular cartilage 72

degeneration 94erosion 152-3evaluation 41-3iatrogenic damage 448. 450lesions on medial condyle of femur 254separation 153

articular fractures 2-3articular surface

damage 93reconstruction 124

autoclavable cameras 10autoclaving 25autogenous fibrinogen, preparation 465avascular synovium 37axial osteitis of proximal sesamoid bones

186 JoV '!

,BBacteroides spp. 436basal sesamoid fragment 184basket forceps 18. 20Baxter-Edwards system 22biceps brachii

endoscopic view 417indentation produced by 311

bicipital bursaendoscopy 415-16infection 430proximal recess 416

blade types 22-3blunt obturator 33blunt probe 16

Ccalcaneus

t1exed plantaroproximal-plantarodistaloblique radiograph 413

intrabursal fracture 433traumatic fragmentation 413

camera coupler 11capillary network 37capitular fovea of proximal radius 334capsulitis, postoperative 453carpal canal 382

instrument insertion level 393tenoscopically assisted release 392use of term 380

carpal chip fractures 94, 99

carpal chip fragmentsdistribution 61repair with small fragement screws 124specific sites 64-93

carpalchipremoval43,61-4

Aabaxial plica, endoscopic view 421abrasion arthroplasty 461-2accessory carpal bone (ACB) 101, 385accessory ligament of superficial digital

flexor, desmotomy of 386acetabulum, chip fracture removal 345adhesion resection 398-400adhesions 404amikacin 436amikacin sulfate 435aminoglycosides 436anatomy 36, 48anconeal process, fragmentation 332anesthesia, recovery of 64angled rongeurs 321annular ligament

severing 377tenoscopically assisted division 376

antebrachiocarpaljoint 36, 47,59,88,99,108arthroscopic examination 49-56most lateral portion 56

antebrochiocarpal joint, with recurrenthemarthrosis 40

antimicrobial drug therapy 435postoperative care 436-7prophylactic 448, 452

Arthrex Continuous wave AR 6400S pump13

Arthrex pump assembly 12arthritis 345, 436arthrofibrosis of the knee 39arthroscope 7-9

angled lense 7-8available types 8conical obturator 9direct view 8fields of view 8insertion 32-4, 59magnifying 3 7minor trauma to distal window 451positioning 32-4, 90protective stainless steel sleeve or

cannula 8range of sizes 7-9rotating 34, 48, 54-6self-locking sleeve 8small diameter 7

arthroscopic portals 4arthroscopic probes 16arthroscopic surgery see surgical

arthroscopy

cold bandaging 28-9collagen sponges 435comminution 110-11, 113, 118common digital extensor tendon 133computer-based simulations 45condylar fracture

AO/ASIF reduction forceps 194arthroscopic monitoring 191

conical obturator 32-3consistent osteochondral repair system

(COR) 463contamination

endoscopic evaluation and surgery 428management 427-39postoperative care 436-7postoperative monitoring 437results and prognosis 437

coxofemoral joint see hip jointcranial cruciate ligament 220cranial cul-de-sac 321-2cranial ligament 219

of lateral meniscus, avulsion fracture264

cruciate injuries 2, 256cubital joint see elbow jointcurettage of undermined and separated

cartilage 63curettes 20cutting forceps 18cutting heads or blades for motorized units

22cutting instruments 18-20

types available 19cystic lesions of medial condyle of femur

246

desmotomy of accessory ligament ofsuperficial digital flexor 386

dewdrop lesions at distal aspect of medialtrochlear ridge of talus 292

diagnostic arthroscopyadjunctive diagnostic technique 35-9carpal joint 47-58femoropatellar joint 197-9femorotibial joint 199-223limitations 36pitfalls 36problems and complications 447-54use of probe 35usefulness of 36see also specific applications

digital camera 23-4digital extensor tendon sheath, multiple

masses 406digital flexor tendon sheath

adhesions between flexor tendons anddorsomedial aspect of tendon sheath375

anatomic structures 366composite tenoscopic view 370, 372diagnostic tenoscopy 368-71distention of 454infection 429medial instrument portal for resector

entry 371pathogenesis 365penetrating wound 434postoperative care 376-7results and prognosis 3 77-9reversed arthroscope entry 373standard tenoscopic approach 369structures 367-8surgical anatomy 365tenoscopy 365-79ultrasound image 374see also deep digital flexor tendon sheath

digital image capture and storage devices24-5

digital video capture 9-10discotemporal articulation under gas

distention 443-4disposable blades 22distal articular surface of radius 55, 57distal digital flexor tendon sheath,

endoscopic view 420distal epiphysis of radius 56distal intermediate carpal bone 74-6distal intermediate ridge of tibia,

osteochondritis dissecans (OCD)281-6

distal interphalangeal joints 2,347-59abaxial articular fragments 356-7coffin joint arthroscopy 348coffin joint under carbon dioxide gas

distention 355-6

diagnostic arthroscopydorsal compartment 351dorsal pouch 348-9palmar compartment 353palmar/plantar pouch 349-52

carpal flexor tendon sheath. use of term380

carpal fragmentation. basic protocol 62carpal joint 36.38.47-127

anatomy 47arthroscopic view 34diagnostic arthroscopy 47-58skin incision 32

carpal lesions 147carpal retinaculum 3carpal sheath

craniomedial depths 382cross-section anatomy 381-2diagnostic arthroscopy 380-91lateral approach 382postoperative care 391-3proximolateral 392standard entry point 383surgical anatomy 380tenoscopic view 384-5tenoscopy 379-93use of term 379-80

carpal slab fractures 3. 109-22. 124current status of surgery 109-10

carpal tunnel syndrome 388-91

cartilagechange 41damage 146. 442debridement 456-8degeneration and immobilization 437disruption IIIerosion 342irregularity 343lesions 340reattachment 458-60response to injury 455shavings 45see also articular cartilage

cartilage repair 3. 455-72future directions 467manipulative procedures for 456-62methods 455-67

caudal cruciate ligament 217caudal medial femoral condyle 221caudal medial meniscus 221caudal pouches. arthroscopic surgery 264ceftiofur sodium 435-6central trochlear groove of femur 233cephalosporin 436chip fractures 60

chondrocytebanking 465-6clinical applications of transplantation

465death 23grafting. clinical application 466transplantation 463-5

chondrocyte-IGF-1 grafting ofsubchondral cyst of femoral condyle466

chondroplasty 458chondrotoxicity 436Cidex-activated dialdehyde solution 26closed coupled device (CCD) chips 10

Ddebridement 44-5.62. 71-2. 83-4. 86.

88,106.108. Ill. 118. 142. 150.153.161-4.184.188.287.334.344-6.429-32after chip fracture removal 94-6cartilage 456-8conservative approach 96foreign material 430!)umeral head 320 ~

'-osteochondritis dissecans (OCD) 33~ ..

subchondral cystic lesion 164-7, 251suspensory defect with motorized

resector 176suspensory ligament tags with

motorized resector 175sustentaculum tali 401using motorized equipment 96using motorized resector 187

deep digital flexor tendon (DDFT) 278.365-8.371-4.376-80.382.384-8.395.397-400.404.421endoscopic appearances of penetrating

wounds 423nomenclature 393rupture of body of radial head 391tearing of dorsal surface 425

endoscopycalcaneal bursa 410intertubular bursae 414management of contamination and

infection 427-39enrofloxacin 435-6entheseous new bone 453epinephrine 448esteotome 19ethmoid forceps 141ethmoid rongeurs 16-17exfoliation 44-5extensor carpi radialis (ECR) 53.405-6extensor tendon sheath

removal of mass 407tenoscopy 403-7

extrasynovial extravasation of fluid450

dorsal recumbency 48dorsal synovial pad. fibrous thickening

39dorsal synovial recesses 48dorsodistal articular surface of radius 58dorsodistal intermediate carpal bone

69-73dorsodistal radial carpal bone 64-9dorsolateral arthroscopic portal 53dorsolateral-palmaromedial (DLPMO)

oblique views 65. 73-4. 78. 89dorsolateral pouch, synovial membrane of

272dorsomedial eminence of proximal phalanx

148dorsomedial intercarpal ligament 39. 48dorsomedial joint pouch 278dorsomedial-palmarolateral (DMPLO)

projection 69. 85dorsomedial portal 53dorsoproximal chip fractures of proximal

phalanx 152dorsoproximal margin of radial carpal

bone 82dorsoproximal radial carpal bone 78dorsoproximal third carpal bone 73drapes and draping systems 27Dyonics DyoVac suction punch rongeurs

21Dyonics InteliJET pump 14Dyonics Power Mac system 22Dyonics PS3500EP power shaving system

21

Ffasciitis 452femoral condyle 217

chondrocyte-IGF-l grafting ofsubchondral cyst 466

femoral headcartilage erosion, over cranial portion

342cartilage irregularity 343cartilage lesions 340complete rupture and contraction of

proper ligament 343lateral portions 342partial rupture of ligament 344subchondral cystic lesion 344tearing of ligament 340-4

femoropatellar joint 2clinical conditions 199diagnostic arthroscopy 197-9fragments in proximal pouch 239insertion of arthroscope 197insertion of arthroscopic sheath 199lateral approach 212normal arthroscopic anatomy

197-9relationship of arthroscope and sleeve

to patella and distal femur at initialentry 200

surgical arthroscopy 223-46femoropatellar pouch, egress cannula to

flush debris from 240femorotibial joint 2,36

arthroscopic portals for caudal pouches220

clinical conditions 223cranial approach 199-212diagnostic arthroscopy 199-223insertion of arthroscope 199-212

into caudal compartment 222into caudal pouch 218-20

normal arthroscopic anatomyof caudal compartment 222-3of caudal pouch 220-2of cranial compartment 218

Eegress cannula 15-16, 33-5, 62,131,

240, 295, 320egress flushing 171egress needle 340elbow joint 327-36

anatomy 327arthroscopic approaches 327-36arthroscopic surgery 332caudomedial approach 328-30caudomedial portions 331

,;;-l' caudomedial pouch 330 ~caudoproximal approach 330caudoproximal aspect 333caudoproximal pouch 332complications 334-6cranial pouch 328-9craniolateral approach 328osteoarthritis 334osteochondritis dissecans (OCD) 332osteochondrosis 332positioning for arthroscopy 327-8septic arthritis 332-4triangulation 336

electrolyte solution 12, 308electrosurgery 44

devices 23malfunction 26

elevators 18-19

distal interphalangeal joints (Continued)dorsal approach for joint distention and

palmar location of arthroscopeportal 352

fracture of dorsomedial perimeter ofdistal condyle surface of middlephalanx 357

fragments in palmaro/plantaroproximalpouch 357-8

free-floating osteochondral fragment 347general considerations 347insertion of arthroscope 348-9

palmar/plantar aspect 350normal arthroscopic anatomy 349

palmaro/plantaroproximal aspect350-2

osteochondral fragment 348osteochondritis dissecans (OCD) 354palmar cul-de-sac 358position of arthroscope 350

palmar/plantar aspect 352position of hypodermic needle 348postoperative management 356preoperative considerations 354-5problems and complications 356radiograph of abaxial intra-articular

traumatic avulsion fracture ofmiddle phalanx condyle 354

results of arthroscopy 356surgical arthroscopy for treatment of

extensor process fragments 352-6surgical technique 355

distal lateral radius 85-7fragmentation 88

distal medial radius 89-90distal medial trochlear ridge 206

axial aspect 231distal metacarpus 42

drilled hole 192fractures of lateral condyle 189

distal navicular bursa. endoscopic view420

distal phalangeal blood supply 349distal radial carpal bone 43. 49. 65. 68.

70. 72. 107distal radius

lateral aspect 85-9medial aspect 89-90

distal recess. endoscopic view 418distal sesamoidean ligaments 184distended extensor carpi radialis tendon

sheath 406distention 11-12.32.48

digital flexor tendon sheath 454maintenance 57-8postoperative 452

dorsal arthroscopic portals 47dorsal aspect of proximal phalanx. frontal

fractures of 152dorsal metacarpophalangeal joint 453dorsal pouch

of fetlock joint 132insertion of arthroscope 130synovial membrane proliferation 158

humeruscranial aspect 311craniolateral portion 332endoscopic view 417-18lateral tuberosity 419loss of fibrocartilage 418osteochondritis dissecans (OCD) 315

hyaluronan 436hyperemic villi 37hypertrophic medopatellar plica 39

fractures 2fragmentation 47. 88. 93

anconeal process 332calcaneus 413carpus and fetlock 2distal margin of navicular bone 424glenoid 319multiple sites 93patella 242-5

fragments. failure to remove 453frontal fracture of proximal phalanx 152.

154fucal subchondral bone disease 43

~GameReady for pneumatic pressure and

cold bandaging 28gas distention 34gas emphysema 15gas insufflator 14-15gentamicin 435-6. 452gienohumeralligament 312glenoid

articular fracture 325cranial rim 311cyst debridement 321cystic lesion 315. 318fragmentation 319osteochondritis dissecans (OCD) 315.318osteochondrosis 324undermined cartilage 319

gram-negative bacteria 436growth factors 464-5

IIGF-l 465.467infected cellulitis 452infection

classification 428endoscopic evaluation and surgery 428iatrogenic synovial 451intrathecal 451management 427-39postoperative care 436-7postoperative complications 451-2postoperative monitoring 437results and prognosis 437stages of 428treatment protocols 428

infectious arthritis 436hip joint 345

infraspinatus tendon 308.310.312instrument portal 33. 35instrumentation 7-30

breakage 448.450-1broken instrument retrieval 18care and maintenance 2 7-8hand instruments 16-23motorized 21-3see also specific types and applications

intercondylar eminence fracture 2intermediate carpal bone 52.54. 57International Cartilage Repair Society

(ICRS) 41. 94interphalangeal joints 347-64

distal phalanx cysts 358proximal navicular cysts 358-9see also distal interphalangeal joints;

proximal interphalangeal jointsintersesamoidean ligament 137-8

detachment from proximal sesamoidbone 186

intra-articular fragments. location of 60-1intra-articular ligaments and menisci.

evaluation 40intrasynovial evaluation 3intrathecal endoscopy of synovial bursae

409intrathecal NaHA 391ipsilateral arthroscope 183irrigation 11.59.62

femurarticular cartilage lesions on medial

condyle 254central trochlear groove 233concave subchondral defects of medial

condyle 249cystic lesions of medial condyle 246

postoperative management 252preoperative considerations 246-9results 252-4technique 249-52

flattened lesion on lateral trochlearridge 225

lateral trochlear ridge 228-9,232-3,235,238

medial condyle 214,216medial trochlear ridge 226, 229, 233,

236osteochondritis dissecans (OCD) 226subchondral cystic lesion of medial

condyle 248, 250, 467, 469Ferris-Smithrongeurs 17, 62, 88-9, 157,

170-2,177-8,185,228,295,317,320-1

fetlock joint 2,60diagnostic arthroscopy 129-36dorsal pouch of 132insertion of arthroscope 132-5loose plantar fragments in 172palmar or plantar 132-5palmar or plantar pouch 135-6surgical arthroscopy 136-95

fetlock lesions 147fibrillation 41-2, 44-5, 261

lateral patellar ligament 247fibrotic changes 37-8fibrotic synovial pad proliferation 157fibrous joint capsule, tearing 453flexed dorsoproximal dorsodistal (skyline)

projections 110-11flexor digitorum longus see medial digital

flexor tendon (MDFT)flexor retinaculum 395

superficial lamina 391tenoscopic view 394

flexor tendons, cross-section anatomy381-2

flow-regulated roller pump 12fluid egress 34fluid extravasation 34fluid ingress line 33fluid irrigation system 11-15fluid pumps, types and properties 12-13fluid system, complications 34focal bone disease 188Foerner elevator 19forage 460forceps 16foreign material

debridement 430detecting and removing 437

intrasynovial451in synovial cavity 429

Hhemarthrosis 448

synovial membrane 40hemorrhagic tenosynovial mass 403hemostats 64high-frequency (HF) equipment 44hip joint 2, 337-46

arthroscopic examination 338-40arthrotomy 337cranial. middle. and caudal aspects 341diagnostic arthroscopy 337-40, 345diseases of 337

"' ,infectious arthritis 345

osteochondritis dissecans (OCD) 344-6osteochondrosis 344-6preoperative assessment 337surgical arthroscopy 340-5

histologic analysis 95history taking 60hook knives 20hook scissors 20human arthroscopy 15. 35humeral head

articular fracture 325debridement 320osteochondrosis 324positioning of arthroscope for surgery

321Jjoint capsule 35, 64

Kkissing lesion 62. 71knee joint

arthrofibrosis 39complication in arthroscopy 447human 34postoperative infection rates following

arthroscopy 448recommendations to minimize

complications associated witharthroscopy 447

knee regeneration 45

osteochondritis dissecans (OCD) 158-62palmar pouch 136pannus deposits 430ultrasonography of dorsal aspect 431

metacarpophalangeal joints 129-96metacarpus 137metaplasia of villi 36metatarsophalangeal joint

indications for arthroscopy 129osteochondritis dissecans (OCD) 158-62

metatarsophalangeal joints 129-96metronidazole 436microfracture 460-1middle carpal joint 47.49.51.59.95

arthroscopic examination 48middle patellar ligament. avulsion of 247midsagittal ridge 133mineralization 400. 402mosaicplasty 463-4motorized equipment 21-3.39.96.

175-6.187.424.458multiple joints 59multiple sites. fragmentation at 93Myobacterium tuberculosis 26

Nnavicular bone

fibrillated fibrocartilage on sagittal ridge425

fragmentation of distal margin 424proximal margin 421sagittal ridge 421

navicular bursaacute endoscopy 422diagnostic endoscopy 424-5endoscopic approach 419penetrating injuries 421-4proximal recess 424treatment of penetrating wound 435

necropsy examination 336necrosis of villi 36nephrotoxicosis 436Nitinol suture needle 263nitrogen driven flutter valve assembly 12.

14nonsteroidal anti-inflammatory drugs 436nuclear scintigraphy 337

Llameness 3. 60. 110.223.246.325.365.

377.380.393.424large fragments. removal of 34lasers 40. 44

types and applications 23lateral condylar fossa. glide hole 192lateral condylar fracture. repair of 186. 190lateral condyle of distal metacarpus.

fractures of 189lateral digital extensor tendon 133lateral digital flexor tendon 393lateral eminence 149lateral femoral condyle 218-20. 222lateral femorotibial joint. insertion of

arthroscope into cranial compartment214

lateral humeral condyle. cranial portion334

lateral meniscus 218-19lateral palmar intercarpal ligaments

(LPICL) 105lateral patellar ligament. fibrillation 247lateral portal 48lateral recumbency 48lateral styloid process 56lateral tibial condyle 219-20lateral trocWear ridge 208-10.228-9.

232-3. 235. 238. 241distal aspect 230

lateromedial projection 69. 73-4. 78lavage 44. 432-4. 448light cable 33light generators 9light intensity 9-10light sources 9-10long digital extensor tendon (LOE) 219long-handled forceps 17loose bodies 18loose body forceps 18

MMcIlwraith arthroscopic rongeurs 17McIlwraith fragment forceps 18McIlwraith-Scanlan elevator 18magnetic retrievers 451manipulative procedures for cartilage

repair 456-62

medial

collateral ligament 276medial condyle 133. 215-16

subchondral cysts of 467-9medial digital flexor tendon (MDFT) 395medial dorsal intercarpal ligament (MDIC)

69medial eminence 149medial femoral condyle 207medial

femorotibial jointapproach to cranial pouch 212-13lateral approach 213manipulation of arthroscopic sleeve

and conical obturator 213normal arthroscopic anatomy of

cranial compartment 213-14positioning of arthroscope 212. 214rupture of cruciate ligaments 258surgical arthroscopy 246-64

medial humeral condyle. osteochondritisdissecans (OCD) 335

medial lateral condyle 219medial malleolus 278

displaced fracture 299osteochondritis dissecans (OCD) 293-4position of arthroscope and instrument

294medial meniscus 215-16

fibrillation of free border of cranialhorn 261

longitudinal tear of caudal horn 265longitudinal tear of cranial horn 261-2transverse vertical meniscal tear 264

medial palmar intercarpal ligament(MPICL) 37.48.104-6

medial patellar fibrocartilage 246fracture of 247

medial patellar ligament 205medial patellar plica syndrome 39medial plica 73medial portal 54medial sesamoid bone. basal fragment 182medial tibial intercondylar eminence.

fracture of 256medial trochlear ridge 204-5. 207.229.

231.233.236meniscal injuries 257-64meniscalligament injuries 257-64 {i

meniscal tears 2. 260meniscectomy in humans 1meniscotome 22meniscus

and associated ligaments 260removal of axial portion 261repair technique 263

mercury vapor lamps 9metacarpal/metatarsal condyle fractures 3metacarpophalangeal joint 38

arthroscopic examination 129-32indications for arthroscopy 129infection 429insertion of arthroscope 130-2insertion of arthroscopic sheath and

conical obturator 131

0obturator 32-3. 99.131.213.309.376-7olecranon. cranial cortex of 336operating arthroscope 3 5osteoarthritis (OA) 60. 343

elbow joint 334in humans 45progressive 111secondary 111shoulder joint 325

osteochondral autograft transfer system(OATS) 463

osteochondral chip fragmentation 60

proximal check desmotomy 389proximal check ligament 386.390proximal dorsal aspect of proximal

phalanx. removal of osteochondralfragments from 136-52

proximal dorsal eminences of proximalphalanx 152

proximal dorsomedial eminence ofproximal phalanx 146.153

proximal intermediate carpal bone 78. 82-4proximal interphalangeal joints 359-64

arthroscopy of dorsal pouch 359-60arthroscopy of palmar/plantar pouch

360-4avulsion fracture of abaxial distal

condyle of first phalanx 361osteochondritis dissecans (OCD) 361position of arthroscope for

palmar/plantar pouch 362removal of palmar middle phalanx

osteochondral fragmentation fromaxial midline of palmar pouch 364

proximal intertarsal joint (PIT) 274proximal phalangeal fracture 144proximal phalanx 2. 133-5. 139

dorsomedial eminence 148dorsoproximal chip fractures 152fragmentation of plantaroproximal

articular surface 449frontal fractures 152. 154lateral eminence 147multiple fragments associated with

lateral plantar process 171osteochondral fragments of proximal

palmar or plantar aspect 167-72proximal dorsal aspect of. removal of

osteochondral fragments from136-52

proximal dorsal eminences of 152proximal dorsal fragments of 139proximal dorsomedial aspect 143proximal dorsomedial eminence of 146.

153proximodorsal aspect 147

proximal radial carpal bone 54. 82proximal radius. capitular fovea of 334proximal sesamoid bones

apical-abaxial fragmentation 181axial osteitis 186removal of fragments 172-85

proximal third carpal bone 43proximal ulnar carpal bone 85Pseudomonas aeruginosa 26pumps 11-14. 34punctate erosions 41

osteochondral disease 2. 44osteochondral erosion 43osteochondral fragments 60.65.147.453

palmar aspect of carpal joints 99-100proximal dorsal aspect of proximal

phalanx 136-52proximal palmar or plantar aspect of

proximal phalanx 167-72osteochondral grafts 462-3osteochondral healing 99osteochondritis dissecans (OCD) 2. 16. 18.

105.223-42.269.315.466cartilage flap re-attachment 459chronic lesions 237debridement 335distal dorsal aspect in

metacarpophalangeal andmetatarsophalangeal joints 158-62

distal intermediate ridge of tibia 281-6distal interphalangeal joints 354distribution of lesions 224elbow joint 332glenoid 315.318hip joint 344-6humeral head 318humerus 315lateral trocWear ridge 224-6. 460medial humeral condyle 335medial malleolus 293-4patella 227postoperative management 241preoperative considerations 223-6proximal interphalangeal joints 361results 241-2shoulder joint 319surgical treatment 279tarsocrural (tibiotarsal) joint 269. 280technique 226-40

osteochondroma. tenoscopic removal 393osteochondrosis

arthroscopic technique 314-22elbow joint 332glenoid 324hip joint 344-6humeral head 324preoperative considerations 314shoulder joint 314-25

osteomyelitis 325osteophytes 92-3osteotome 18. 62. 385

p

middle carpal and antebrachiocarpaljoints. arthroscopic examination 57

palmarolateral outpouching 59pannus

deposits in scapulohumeral joint 432formation 37removal 430

partial thickness chondrectomy 44-5patella 202-4. 208

articular surface 230fractures 245-6fragmentation 242-5

postoperative management 245preoperative considerations 242results 245technique 242-5

osteochondritis dissecans (OCD) 227.238

secondary remodeling 238patella forceps 18patella rongeur 17-18patellofemoral articulation 36pathologic plicae in man 39penicillin 436.452periarticular osteophytes 60periarticular swelling 29periarticular tissues 59perichondrium for improved cartilage

repair 462periosteum transplantation 462perisynovial structures

iatrogenic damage 450injury 448

petechiation of villi 37. 429phenylbutazone 97. 322photography 23plica-associated disease 39pluripotent mesenchymal stem cell

transplantation 464pneumoperitoneum 15pneumoscrotum 15polymethylmethacrylate (PMMA) beads 435popliteal tendon 222post-antibiotic effect (PAE) 436post-arthroscopic irrigation and closure 35postoperative care 436pos~operative complications 451-4 tpostoperative effusion 448 '

postoperative monitoring 437preoperative evaluation 31preoperative preparation 31pressure bandaging 28-9pressure management systems 28-9probe use 16

in diagnostic arthroscopy 35in medial palmar intercarpal ligament

37proliferative synovial villi 449proliferative synovitis 158. 305proximal articular surface 53-4

intermediate carpal bone 56proximal aspect of intermediate carpal

bone 83

Rradial carpal bone 42, 57, 66, 69, 71,

80-1,92,95,98-9,106,108large fragment off dorso distal margin

125slab fracture 123-4

pain and pain relief 401. 454palmar carpal ligament (PCL) 385palmar intercarpal ligaments. tearing

104-5palmar osteochondral wedge 87palmar/plantar annular ligament.

transection 371-4palmar pouch

fetlock joint 135-6metacarpophalangeal joint 136

radial osteochondroma 40removal of 385

radial physeal exostoses, removal of 385-8

radiofrequency devices 23radiofrequency energy (RFE) 44radiography

postoperative 36,119,125preoperative 36,119,125

radiusdistal articular surface of 55, 57distal epiphysis of 56dorsodistal articular surface of 58

Richard Wolf Surgical Arthro PowerSystem 22

Ringer's solution 442rongeurs 16-18, 20-1, 62, 321

see also Ferris-Smith

caudal pouches 264current status 58-9femoropatellar joint 223-46limb suspended for 32medial femorotibial joint 246-64post-surgical follow-up information 97postoperative management 97. 115postoperative protocol 102preoperative information 60preoperative planning IIIprinciple of 34-5problems and complications 59. 447-54prognosis 97relevant pathobiology 60removal of osteochondral chip

fragments 58-99results 97.115-22shoulder joint 314-25see also specific applications

surgical assistants 26-7suspensory ligament tags resection with

synovial resector 179sustentaculum tali. debridement 401suture sinuses 452sutures 35synovectomy 39-40. 96

capsular defects and fibrosis following40

carbon dioxide laser 40effect on articular cartilage in equine

joints 40equine joint tissues 39human hemophiliac patients 39mechanical 40

synovial 449-51. 3649synovial bursae 3

intrathecal endoscopy 409

synovial diverticulum 218synovial effusion 280synoviall1ap 133synoviall1uid

bloody or brown 65-6debris in 36

synovial fold 39synovial fossa 273-4synovial membrane 36-7, -

205, 220, 273-4biopsy 37dorsal pouch 158

evaluation 36-9hemarthrosis of 40proliferation 39.158resection of 170

synovial pattern 37synovial proliferation 37.

osteoarthritis 325osteochondritis dissecans (OCD) 319osteochondrosis 314-25placement of arthroscope 322postoperative management 322problems and complications 322radiograph and positive contrast

arthrogram 316results of surgical arthroscopy 323-5septic joint 325specific indications and technique for

diagnostic arthroscopy 312surgical anatomy 307triangulation 317.322see also scapulohumeral joint

skin abscesses 452skin incision 32.35.48.64.89.282

suturing 35skin portals. closure 132skin sutures. complication rate 448slab fractures see carpal slab fracturesslotted cannula 376-7small fragments 16-17Smith & Nephew Dyonics Arthroplasty

System 22smooth edged resectors 22sodium benzylpenicillin 435-6. 452soft tissue mineralization 453spinal needle 282.307-8.314.317.322.

340spongialization 462spoon curettes 20spurs 92-3stem celltransplantation 464sterilization 10-11. 25-7stifle joints 2Storz AIDA digital image capture and

storage device 25Stryker arthroscopy pump 14Stryker SDC Pro 2 digital video and still

image storage and printing system 25Stryker System 22subchondral bone 42

disease 100--4. 152-3drilling 460

subchondral cyst 2.108-9.164-7.254-6.467-9 :0,

§libchondrallucency 104subchondral microfracture 99subfascial cellulitis 452suction

applications 21use on shavers 23

sulcus muscularis 218superficial digital flexor tendon (SDFT) 38.

365-8.371-4.378-80.384.386.388.413-14

supraglenoid tubercle. fragmentation 419suprapatellar pouch 201surgical arthroscopy 44

advantages of 58-9basic techniques 35case selection 97

40synovial resection 96synovial resector units 22

5scalpel blade 32.35Scanlan-Mcllwraith scissor-action

rongeurs 20scapulohumeraljoint 307-26

caudal aspect 309cranial aspect 311exploration 314lateral aspect 310medial aspect 312pannus deposits in 432see also shoulder joint

sclerosis of third carpal bone 100self-sealing cannula 20-1septic arthritis 306. 325

diagnosis 37elbow joint 332-4

septic osteomyelitis 306septic physitis 325sesamoid bone 137-9. 367

basal fragment of 183fracture 172. 180fragmentation of 185

shavers 22suction use on 23

sheath insertion 32-3sheathed blades 19sheathed knife system 20shoulder joint

arthroscopic surgery 31~25caudal aspect 313damage to instruments 323diagnostic arthroscopy 307-14difficulty in reaching potential lesions

323final position of arthroscope within

sheath 309fluid extravasation 322insertion of arthroscope 307-8insertion of arthroscopic sheath and

obturator 309lateral approach 309-12medial aspect 313normal arthroscopic anatomy 308-9

infection 427-39

290-1

synovial villi 38. 49morphologic features 36obstruction of view by 449-51

synovitischanges in 37evaluation 36-9experimentally induced 37forms 37post-operative 452proliferation and thickening of synovial

villi 38 extremity 254-6

tight spaces 17toothed edged resectors 22transillumination 36

traumatic joint disease 37. 40triamcinolone acetonide 253triangulation 1

elbow joint 336principle of 34-5shoulder joint 317.322

trochlear groove 202-3.211

Uulnar carpal bone 52. 85ulnar fracture. mid-shaft 336ultrastructural studies 45

Vvacuum attachments 21vasculature changes 37VCRs 24

video cameras 10-11video documentation 10. 23-4video recorders 10

lightweight single-chip or three-chip 10videoarthroscopes 8. 11videotape 9. 24villi

metaplasia 36necrosis 33petechiation 37.429proliferative synovial 449synovial 36. 38.49.449-51visualization 47

villonodular synovitis 152-8villous regeneration 40villous synovial membrane 210. 219viruses 26

Ttalocentraljoint

fragments dislodged from medialtrochlear ridge and entereddorsomedial pouch 304

retrieval of fragments 299talus

central medial trocWear ridge 277dewdrop lesions at distal aspect of

medial trocWear ridge 292distal medial trocWear ridge 277distal trocWear groove 274lateral trochlear ridge 272lateral trochlear ridge and distal tibia

junction 271medial trocWear ridge 273-4, 276, 278

and distal tibia and medial malleolusjunction 275

osteochondritis dissecans (OCD)286-91

osteomyelitis of dorsodistallateraltrocWear ridge 434

sagittal fracture 303subchondral cystic lesion of trochlear

groove 294-5,297wear lines on medial trochlear ridge 295

tarsal sheathcentromedial approach 398cross-sectional specimen 396-7diagnostic tenoscopy 397-8distal aspect 401distal region 400, 404inflammation 402medial aspect 395nomenclature 393postoperative care 401-2proximal region 396. 399surgical anatomy 395-7sustentaculum level 396tenoscopy 393-402

results and prognosis of tenoscopy402

tenosynovitis 402wound healing complications 401

tarsal tunnel 395tarsal tunnel syndrome 393tarsocrural joint 269-306

diagnostic arthroscopy 269-79dorsomedial approach 269-79

insertion of arthroscopic sleeve 270

Wwear lines 42, 44wounds

healing complications 401management 434-5postoperative care 436-7

intra-articular fractures 299osteochondritis dissecans (OCD) 280. 296

results 291-4plantar lateral or plantar medial

approaches 278-9positioning of arthroscope 270puncture wound in dorsolateral aspect

428surgical arthroscopy 279-306

aftercare 306tears and avulsions of collateral

ligaments 305tarsus. fracture of proximal plantar aspect

of medial trochlear ridge 300-1temporomandibular joint (TMJ) 441-5

arthroscopic approach 442-3articular disk 442bone scintigraphy 441clinical results 444-5diagnosis of inflammation 444disco temporal compartment 441-2medial penetration of joint capsule 444overview 441preoperative considerations 441-2proximal compartment 443ultrasound image 442ventral disco mandibular articulation

441tendon linear clefts 374-6tendon sheath

problems 3see also extensor tendon sheath

tenoscopy 365-408carpal sheath 379-93diagnostic 368-71digital flexor tendon sheath 365-79extensor tendon sheath 403-7mass removal/adhesion transection

371results and prognosis 393tarsal sheath 3.393-402techniques 368-76. 380-91. 397-401

tenosynovial masses 398-400. 403and adhesions 371

tenosynovitisacute 365 1'$chronic 365complex 365

thermal chondroplasty 44third carpal bone 43.78-80.97.102

bone density 104lag screw fixation of slab fractures

110-15sagittal fracture 121-2sclerosis of 100slab fracture 109-10.112.114-16.

118-20.124third metacarpal bone

debridement of subchondral cysticlesions 164-7

subchondral cyst in medial condyle 468tibia 218

distal intermediate ridge 273

Xxenon light sources 9-10