06. principles of free tissue transfer in orthopaedic practice

Principles of FreeTissue Transfer inOrthopaedic Practice

AbstractFree tissue transfer is a vital adjunct to orthopaedic practice; it mayoptimize the treatment of many emergency and elective conditionsthat require soft-tissue or bone augmentation. Consultation with acolleague trained in microsurgery is often necessary in undertakingfree tissue transfer techniques. A two-team approach frequently isused to maximize efficiency and minimize fatigue. Flaps with reli-able pedicle anatomy are preferred. Flaps typically are raised usingan open technique, but endoscopic techniques can be utilized to de-crease donor-site scarring. Free tissue transfer is a demanding pro-cedure; careful preoperative planning is essential to ensure optimalresults. Free tissue transfer inevitably results in some donor mor-bidity, and flaps are carefully chosen to minimize this. The mostserious complication is failure of the flap. Free muscle flaps used insoft-tissue reconstruction today result in little loss of function.

Definitions andTerminology

Free tissue transfer is a procedurein which soft tissue and/or boneis harvested with its vascular pedicleand transferred to a recipient site,where the pedicle is anastomosed tolocal vessels, thus revascularizingthe tissue. The pedicle is the vascu-lar axis of the transferred tissue; itcontains an artery and one or moreveins. Pedicles with large vessel lu-mens and reliable anatomy are pre-ferred. A long pedicle makes it easierto perform a tension-free anastomo-sis in an optimal position, increasingthe likelihood of anastomotic pa-tency. Larger vessel lumens increasethe ease of anastomosis.

Free flap is a term used to de-scribe a transfer of soft tissue. Theprocess of dissecting and preparing a

flap for transfer is known as raisingor harvesting a flap. The flap is insetinto its recipient bed.

Free tissue transfers in ortho-paedic surgery may include skin,fascia, muscle, nerve, tendon, bone,and/or joint. A flap containing twoor more tissue types is known as acomposite flap. Such a flap is partic-ularly useful when reconstructionmust address the loss of several tis-sue types (eg, skin, bone, andmusclein a severe open tibial fracture)or in toe-to-hand transplantation,in which a neurosensory flap isrequired.

A fascial flap, such as the tem-poroparietal flap, contains fasciaalone and can provide a thin layer ofvascularized tissue that supports askin graft and allows underlying tis-sues to glide. A fasciocutaneous flap,such as the radial forearm flap or

Richard Lawson, MBBS, FRACS

L. Scott Levin, MD, FACS

Dr. Lawson is Lecturer, Department ofHand and Peripheral Nerve Surgery,Royal North Shore Hospital, Sydney,New South Wales, Australia. Dr. Levin isChief, Division of Plastic ReconstructiveMaxillofacial and Oral Surgery, andProfessor, Orthopedic and PlasticSurgery, Duke University MedicalCenter, Durham, NC.

None of the following authors or thedepartments with which they areaffiliated has received anything of valuefrom or owns stock in a commercialcompany or institution related directly orindirectly to the subject of this article:Dr. Lawson and Dr. Levin.

Reprint requests: Dr. Levin, Division ofPlastic and Reconstructive Surgery,Duke South Hospital, Room 134, BakerHouse, Trent Drive/Brown Zone,Durham, NC 27710.

J Am Acad Orthop Surg 2007;15:290-299

Copyright 2007 by the AmericanAcademy of Orthopaedic Surgeons.

290 Journal of the American Academy of Orthopaedic Surgeons

lateral arm flap, contains skin andfascia and is thus a composite flap.The skin and fascia are nourished bysmall vessels originating from thepedicle that pass through a fascialseptum and ultimately reach theskin (Figure 1).

A perforator flap consists of skinor subcutaneous fat and is perfusedby small vessels from an underlyingvascular system. However, thesevessels do not run in a fascial sep-tum but rather pass directly throughor perforatemuscle and fascia to vas-cularize a discrete vascular territory,or angiosome. Perforator flaps pro-vide the surgeon with increased ver-satility because these flaps do notneed to be based on a named artery.They may be based on any identifi-able perforating vessel,1 which hasmade them an increasingly populartool for reconstructive surgeons(Figure 2).

Tendocutaneous flaps, such as thefree innervated dorsalis pedis ten-docutaneous flap, contain tendonsoverlying fascia and skin and can beparticularly useful in resurfacing thedorsum of the hand when compositeloss of tissue has occurred.

Bone and periosteum can beraised alone, as in a free vascularizedfibular graft, or can be raised alongwith other tissues; an osteofasciocu-taneous transfer contains bone, fas-cia, and skin. The bone is vascular-ized by the periosteum connected tothe pedicle and may receive addi-tional inflow by a distinct nutrientartery arising from the pedicle.

A muscle flap is often raised witha paddle of overlying skin to serveboth as a source of skin for coverageand as a visual gauge of the flaps per-fusion. Such a flap is called amyocu-taneous flap, and the skin paddle iscalled a buoy.

Functioning muscle transferscontain a motor nerve in addition tothe vascular pedicle. The nerve is su-tured to a source of donor axonswiththe goal of achieving reinnervationand voluntary control of the muscle(Figure 3).

Figure 2

Perforator flaps. This cross section through the left midthigh illustrates thedifference between a septocutaneous flap, in which the feeding vessel runs alongan intermuscular septum, and a perforator flap, in which the feeding vessels runthrough muscle and fascia to vascularize the overlying tissue. (Adapted withpermission from Wei FC, Jain V, Suominen S, Chen HC: Confusion amongperforator flaps: What is a true perforator flap? Plast Reconstr Surg 2001;107:874-876.)

Figure 1

Fasciocutaneous flap. This cross section of the distal humerus illustrates the planeof dissection for the lateral arm flap. The pedicle runs along the base of a fascialseptum, with perforating branches running through the septum to supply theoverlying fascia and skin.

Richard Lawson, MBBS, FRACS, and L. Scott Levin, MD, FACS

Volume 15, Number 5, May 2007 291

A fillet flap is tissue harvestedfrom a damaged part that has beenamputated; this salvage of usablematerial may obviate the need foradditional tissue from undamagedareas of the body. An emergency freetissue transfer is a transfer per-formed immediately after the firstwound dbridement or within 24hours after this dbridement.2

History

A basic principle of reconstructivesurgery, espoused by Sir Harold Gil-lies, the father of modern plastic sur-gery, is to replace like with like.3

The tissues surrounding the area tobe reconstructed may not providethe required type, quality, or volumeof tissue, but microsurgery providesthe means to import tissues withdiscrete blood supplies to virtuallyany part of the body in which circu-lation can be reestablished.

Encouraged by the work of Jacob-son and Suarez,4 free tissue transferbecame possible in the late 1960sand early 1970s with the refinementof the operating microscope, mi-crovascular instruments, and finesuture material. The first free flap

was the free groin flap, but this isnow rarely used because of its shortpedicle length. The free groin flaphas been superseded by far more ver-satile flaps, such as the widely usedradial forearm fasciocutaneous flapdescribed by Song et al5 in 1982. Thefirst free fibula transfer was reportedby Taylor et al6 in 1975. Taylor andHam7 introduced vascularized nervegrafts in 1976. The first toe transfer,in a rhesus monkey, was reported byBuncke et al8 in 1966.

In the early days of reconstruc-tive microsurgery, the primary em-phasis was on achieving flap sur-vival. However, now that survivalrates of 95% to 98% have becomeexpected, the emphasis has shiftedtoward optimizing function andappearance and minimizing donorsite morbidity.9

Harvesting the FreeTissue Transfer

Flaps with reliable pedicle anatomyare preferred. In most commonlyused flaps, the surface anatomy pro-vides a useful guide to the underly-ing pedicle. However, a handheldDoppler probe may be used to accu-

rately localize the pedicle; this canbe particularly useful in perforatorflaps, such as the anterolateral thighflap.

Flaps typically are raised using anopen technique, but endoscopictechniques can be utilized to de-crease scarring in the donor site. Thegracilis flap lends itself to endoscopicharvesting because amajor disadvan-tage of harvesting this flap by openmethods is the long scar createdalong the medial aspect of the thigh.The rectus abdominus and latissi-mus dorsi muscles are also some-times harvested using endoscopictechniques. Although endoscopicharvest is technically demandingand initially time-consuming, localdonor site scarring can be signifi-cantly decreased. For example, an in-cision length of 20 to 30 cm resultingfrom an open method can be de-creased to 7 cm, on average, usingendoscopy for the latissimus dorsi.10

The endoscopic technique also hasbeen shown to result in increased pa-tient satisfaction.11

Application of the FreeTissue Transfer

Coverage of TissueDefects and Managementof Combined Injuries

Optimal surgical management ofcomplex open injuries commenceswith rigorous, methodical dbride-ment of contaminated and devital-ized tissue under tourniquet control.Nerves and major vessels should becleaned and preserved; all other softtissues may be dbrided. Bony frag-ments lacking soft-tissue attach-ment should be removed. Second-and third-look operations may benecessary to ensure complete re-moval of all contaminated tissue.

When dbridement has been com-pleted, the surgeon is left with thechallenge of obtaining coverage ofthe resultant defect.12-14 One tool foranalyzing the options for woundcoverage is the reconstructive lad-der.15 The bottom rung of the ladder,

Figure 3

Free gracilis flap, illustrating its pedicle, motor nerve, and overlying skin flap.

Principles of Free Tissue Transfer in Orthopaedic Practice


representing the simplest option, isprimary wound closure. If this is notpossible, the ladder is ascended tomore complex options, including de-layed primary closure, healing bysecondary intention, and skin graft-ing. Next in increasing complexityare local flaps (raised from tissuesimmediately adjacent to the defect)and regional flaps (raised from tis-sues in the same limb). The top rungof the ladder is a free flap (Figure 4).

Although it is usually advisableto start at the bottom rung of the re-constructive ladder and attemptsimple wound closure, in some sce-narios it can be advantageous to pro-ceed directly to the top of the ladder,particularly when dbridement hasleft an extensive soft-tissue defect orhas exposed hardware or vital struc-tures, such as bone, vessels, nerves,or tendons. A free tissue transferbrings in healthy vascularized tissue,fills dead space, can cover large de-fects, and can expedite rehabilitationby allowing earlier joint movement.

Open FracturesGodina16 demonstrated that early

coverage (within 72 hours) of openfractures with muscle flaps resultsin improved outcomes, includinghigher rates of bone union and low-er rates of wound infection. Muscleflaps are therefore usually chosen tocover open fractures; these in turnare coveredwith split-thickness skingrafts because myocutaneous flapsare often too bulky and are prone toshearing of the skin component.

An appropriately sized flap is cho-sen to eradicate dead space. Smalldefects can be covered with slips ofthe serratus anterior muscle or por-tions of the gracilis. Large defectscan be coveredwith a latissimus dor-si flap, which provides up to 25 40cm of coverage. Initially the musclemay have a bulky appearance, butbecause the muscle is denervated inthe course of transfer and atrophieswith time, the contour of the recip-ient site improves.

Management of DeepInfection

Chronic osteomyelitis is mostcommonly seen after an open frac-ture. The soft tissues at the fracturesite are usually scarred and adherentto the underlying bone, and the vas-cularity of the region is impaired. Infractures of the distal tibia, no reli-able local muscles are suitable forcoverage of wounds after dbride-ment of the infected tissue.

This situation can be managedusing the principles of Cierny andMader,17 which consist of aggressivedbridement of devitalized bone andscarred tissues and coverage with amuscle flap. A muscle flap is prefer-able to a fasciocutaneous flap be-cause the muscle flap can effective-ly fill and eradicate dead space,increase the vascularity of the affect-ed area, and increase leukocyte func-tion in the immediate area. If theunderlying internal fixation is con-taminated, the optimal approach isto remove it, provided the fracturehas united. When internal fixationmust be retained, it should be ex-changed with noncolonized metal-work or, preferably, stabilized byanother means, such as external fix-ation. Retention of infected metal-work beneath the flap increases therate of recurrence of infection.

Reconstruction ofSegmental Bone Defects

Severe trauma, extirpation of a tu-mor, nonunion, or congenital pseud-arthrosis all may result in segmentalskeletal loss. When amputation isinappropriate, nonvascularized bonegrafting can be used for defects

midsection while preserving the at-tachments of the peroneal artery,thereby providing two segments thatare placed side by side in a double-barreled arrangement.

It is possible to harvest the prox-imal fibula and proximal fibular phy-sis to provide longitudinal growth ofthe transplanted fibula. This proce-dure is technically demanding, how-ever, because the proximal fibularepiphysis receives its dominant vas-cular supply from the genicular ar-teries and branches of the anteriortibial artery, whereas the shaft of thefibula is nourished by a nutrientbranch from the peroneal artery. Tomaximize the chances of epiphysealgrowth, both vascular territoriesmust be preserved19 (Figure 5).

Other sources of vascularized bonefor reconstruction include the lateralborder of the scapula as part of a scap-ular flap, the lateral distal radius aspart of an osteofasciocutaneous radialforearm flap, and the lateral distal hu-merus as part of an osteofasciocuta-neous lateral arm flap. Cautionmust

be exercised with the latter two do-nor sources because iatrogenic frac-ture is a recognized complication.The ends of the osteotomy site shouldbe beveled to minimize stress risers,and the defect should be prophylac-tically plated. The iliac crest, ribs, andsecond metatarsal are also availableas sources of bone.

Functioning Free MuscleTransferBrachial Plexus Surgery

Among the surgical options formanagement of brachial plexus inju-ries are direct nerve repair and nervetransfers. Both rely on reinnervationof denervated muscles before the de-velopment of irreversible fibrofattydegeneration. After degeneration hasoccurred, a functioning free muscletransfer, such as an innervated graci-lis, rectus femoris, or latissimus dor-si, can be used to bring a healthymuscle into the arm. The muscle isharvested along with its nerve,which is sutured to a healthy intra-plexal or extraplexal nerve.

The gracilis muscle is often cho-sen for functioning free muscletransfer because it is expendable, haslong muscle fiber length (providinggood excursion), and has a reliablevascular pedicle from themedial cir-cumflex femoral artery. Following asuccessful gracilis transfer for defi-cient brachialis and biceps musclefunction, approximately 75% of pa-tients have grade 3 or 4 elbow flex-ion; the typical patient can lift ap-proximately 5 kg.20

An alternative approach to com-plete brachial plexus injury is to pro-ceed to functioning freemuscle trans-fer soon after the injury rather thanafter muscle degeneration has oc-curred.Doi et al21 have advocated thisapproach, which is designed to pro-vide Prehensile function through theuse of two freemuscle transfers. Thefirst free gracilis crosses the flexor sideof the elbow joint, using the brachio-radialis and radial wrist extensors asa pulley; the muscle is then suturedto the wrist extensors. The secondfree gracilis transfer is performed ap-proximately 3months later to providemotors for the finger flexors. Themuscles are innervated by extraplexaldonorsthe first transfer by the spi-nal accessory nerve, the second by in-tercostal nerves. Intercostal nervesare also used to motor the tricepsmuscle and to provide sensory fibersto the median nerve. Using this se-quence of procedures, Doi et al22 ob-tained satisfactory elbow flexion in96% of patients and prehension of atleast 30 of total active fingermotionin 65% of patients.

Volkmanns IschemicContracture in the Forearm

In mild or moderate Volkmannscontracture, sufficient muscle maysurvive to allow tendon transfers toreplace lost functions. In severeVolkmanns contracture, most of theflexor mass and much of the exten-sor muscle mass of the forearm un-dergoes ischemic necrosis, leavinginsufficient muscle for tendon trans-fer. A solution to this problem is free

Figure 5

Overview of sources of vascularized bone for reconstruction of segmental defects.* = vascularized epiphyseal fibular transfer for distal radius reconstruction inskeletally immature patients, = double-barreled fibula option for femoral shaftreconstruction



muscle transfer. One innervated gra-cilis free muscle can be used to pro-vide finger (or wrist) flexor muscle,and a second one can be used to pro-vide finger (or wrist) extension.

Hand Reconstruction:Toe-to-Thumb Transfer

Toe-to-hand transfer can providepinch grasp in the child with con-genital absence of the digits, partic-ularly in the setting of constrictionband syndrome, and can restorefunction in the patient with trau-matic digital loss. Options availablefor toe-to-thumb transfer include us-ing all or part of the great toe or us-ing the second or third toes. Thegreat toe can be transferred en blocor, for reconstruction of a more dis-tal defect, a segment can be obtainedin the form of a wraparound or atrimmed toe transfer. The great toeis approximately 30% larger thanthe thumb, and a trimmed toe trans-fer has superior cosmetic resultscompared with a standard great toetransfer. Second toe transfer offers amore pleasing donor site but has aninferior appearance on the hand aswell as poorer functional results.23

OsteonecrosisOsteonecrosis of the FemoralHead

Urbaniak developed the use of thevascularized fibula for managementof osteonecrosis of the femoral head,in lieu of joint replacement with ar-throplasty.24 The fibula acts as astructural support for the subchon-dral bone and as a source of mesen-chymal stem cells, which encouragerevascularization of the osteone-crotic bone. Comparison of patientswho underwent vascularized fibulargrafting with a cohort of patients inwhom osteonecrosis was treatedwith core decompression demon-strated improved survival of the freefibula group. Conversion to total hiparthroplasty was the end point. At50 months, 81% of the free vascular-ized fibula group had not requiredconversion to a total hip arthroplas-

ty compared with 21% of the coredecompression group.24

Osteonecrosis and Nonunionof Carpal Bones

Many pedicled grafts have beendescribed for the treatment ofscaphoid nonunion and Kienbcksdisease. Free vascularized bone graftsmay offer some advantages to localpedicled grafts in the form of stron-ger, more easily shaped grafts and inincreased flexibility of placement ofthe graft. Doi et al25 reported on thesuccessful treatment of 10 patientswith scaphoid nonunion, each ofwhom received a free vascularizedgraft from the medial supracondylaraspect of the femur that was nour-ished by the descending medial gen-icular artery and fixed on the volaraspect of the scaphoid.

Vascularized JointThe options for reconstruction of

damaged or congenitally deficientthumb or finger joints include pri-mary repair of the joint surfaces andfusion. Another solution, when therequirement for motion of the jointjustifies the increased complexityand donor morbidity, is a vascular-ized toe joint.26 The metatarsopha-langeal joints of the second and thirdtoes can be used to reconstruct themetacarpophalangeal (MCP) joints,and the toe proximal interphalangeal(PIP) joints can be used to recon-struct either the MCP joints or thefinger PIP joints. The vascular pedi-cle for the toe joints is based on thedorsalis pedis arterial system.

Toe joint transfers have greaterranges of motion when used to man-age posttraumatic defects comparedwith congenital lesions; approxi-mately 30 of motion is typically ob-tained. An extensor lag of 20 to 30usually occurs. This procedure isvery technically demanding.

Vascularized NerveVascularized nerves may be pref-

erable to nonvascularized graftswhen they will be placed in a scarred

bed or if a particularly large segmen-tal defect must be spanned.

Adult patients with complete bra-chial plexus palsy will not achievereturn of function of the muscles in-nervated by the ulnar nerve. The ul-nar nerve can therefore be harvestedalong with the ulnar collateral arter-ies as a source of vascularized nervegraft for reconstruction of the bra-chial plexus. This option is com-monly used when the contralateralC7 nerve root is chosen as a sourceof axons for reconstruction of severebrachial plexus palsy (Table 1).

Patient Selection

When assessing patients for electivefree tissue transfer, the treating sur-geon must seek to optimize all med-ical parameters. Smoking has beenshown to affect blood flow andwound healing, although it may notaffect the overall rate of anastomot-ic patency or flap survival.27

Simpler options, including ampu-tation, may be preferable in the pres-ence of complex pathophysiologicstates, such as chronic renal failureor severe diabetes. Diminishedmen-tal capacity or psychiatric illnessmay prevent compliance with post-operative care and rehabilitation.

Patient age does not appear to bea major factor in patient selec-tion.9,28

Perioperative andPostoperativeManagement of FreeTissue Transfer

A free tissue transfer is a demandingsurgical procedure; careful preopera-tive planning is essential to ensureoptimal results. A two-team ap-proach is often used to maximize ef-ficiency and minimize fatigue, withone team raising the tissue to betransferred while the other team pre-pares the recipient site. Even themost accomplished surgeon willhave a failure rate of 2% to 5%, andpart of the surgical plan is to have an



Table 1

Overview of Donor Options for Free Tissue Transfer

TissueType Donor Site Size of Flap Comments Disadvantages

Skin Radial forearm Up to 10 30 cm Workhorse flapReliable pedicle, pliable

skin, can be combinedwith transfers oftendon and bone

Healing of donor site maybe suboptimal, with pooraesthetic appearance

Compromises arterial inflowto hand

Groin 10 25 cm Easily disguised donorsite

Short pedicle, aestheticimplications of pubic hairat medial aspect of flap,complex vascular anatomy

Anterolateral thigh Up to 25 18 cm Large area of skin andfascia available

May be aesthetic objectionsin females

Less reliable pedicleCan have very thick layer of

adipose tissue, particularlyin white patients

Lateral arm Up to 8 15 cm (nomore than 6 cm widthif primary closuredesired)

Allows harvest fromsame arm as affectedlimb

Can be innervated withposterior cutaneousnerve of arm andharvested with aportion of the humerus

Can have very small pedicleIf harvested over lateral

epicondyle, can causeproblems in healing ofgraft used to cover donordefect

Scapular andparascapular flaps

Up to 20 7 cm Simple, reliable anatomy,hairless

Can be harvested withstrip of scapula if bonealso required

Spreading of scar common,and skin can beparticularly thick

Not innervated

Dorsalis pedis Up to 14 12 cm Can harvest withextensor tendons, canbe innervated withsuperficial or deepperoneal nerves

Very thin, pliable flapGood for extensor

surface of hand

Requires skin graft to coverdonor defect, which oftenhas poor take; thus, thereis significant donor-sitemorbidity

Muscle Latissimus dorsi Up to 25 40 cm Workhorse muscle flapLargest available muscle,

thin and pliable, longreliable pedicle

Seroma formation at donorsite relatively common

Gracilis Up to 6 24 cmSkin paddle up to16 18 cm

Full length of muscleoften used for freemuscle transfer; smallportion can be used forsmaller defects

Disguised donor scar, nodeficit

Distal skin paddle unreliable

Serratus anterior 10 15 cm Used for small defectsThin pliable muscle,

easily contoured

Winging of scapula whenmore than four slips areremoved



Table 1 (continued)

Overview of Donor Options for Free Tissue Transfer

TissueType Donor Site Size of Flap Comments Disadvantages

Muscle(contd)

Rectus abdominis Up to 25 6 cmSkin paddle up to21 14 cm

Easily harvested, goodpedicle diameter

Hernia possible unlesscareful closure of rectussheath

Fascia Radial forearm 8 20 cm Can take fascia alonewith improved donorcosmesis

Loss of radial artery

Temporoparietal 8 15 cm Thin, pliable bilayeredflap applicable forcoverage of exposedtendons

Inconspicuous donor site

Possible damage to frontalbranch of facial nerve

May cause alopecia ifdissection plane toosuperficial

Bone Fibula Up to 25 cm Long, strong strut ofbone that can be usedto reconstruct defectsof all long bones

Can be combined withvascularizedepiphyseal transfer toallow growth

Uncommon peroneal nervepalsy, flexor hallucislongus contracture, ankleinstability

Relatively short pediclelength

Radius 8 to 10 11.5 cm Lateral aspect of distalradius can beharvested with radialforearm flap

Radial fracture commonunless defect wellcontoured and plated

Scapula Up to 3 11 cm Can be harvested withscapular orparascapular flap

Bone is thin and not easilyworked

Humerus Up to 1 10 cm Distal lateral humeruscan be harvested withlateral arm flap

Bone is thin and not easilyworked

Iliac crest Up to 12 4 cmSkin paddle 8 18 cm

Curved bone can beused to match curveddefects; rapidly healingcancellous bone

Inguinal hernia possible ifinadequate closure; curvedbone infrequently requiredin orthopaedicreconstruction

Toe Great toe Best thumb substitute Larger than thumb by 30%;significant donormorbidity

Trimmed great toe (greattoe is harvested buttrimmed to bettermatch thumb)

Improved aestheticscompared with greattoe transfer

Donor morbidity of loss ofgreat toe

Wrap-around Best aestheticappearance of all toetransfers

Preserves function ofgreat toe

Only applicable to thumbloss where there is someproximal phalanx available

Second toe Less significant donordefect

Inferior aesthetic appearanceon hand; looks like a toe



alternative procedure to achievewound closure, should the first pro-cedure fail.

Perioperative strategies are direct-ed toward maximizing flap perfu-sion. Before surgery, the patient isvasodilated; this is achieved by keep-ing the patient hot, happy, and hy-drated. Some surgeons prefer to ad-mit the patient the night beforesurgery to allow intravenous hydra-tion and to ensure that a warm envi-ronment is maintained.

Once in the operating room, theambient temperature should be kepthigh (around 24C) and the patientkept normothermic through the ap-plication of hot air blankets, heatingpads, andwarmed intravenous fluids.

The optimal hematocrit level is30, which provides the best compro-mise between low viscosity (promot-ing blood flow) and acceptable oxy-gen delivery to the tissues. Adequateblood pressure is maintained prima-rily through use of fluid volumerather than pressor agents. A urineoutput of at least 1 mL/kg/hr is de-sirable. Poor flow through the vascu-lar pedicle is often directly related tolow blood pressure or hypothermia;correction of these variables typical-ly results in a marked improvementin blood flow.

The use of agents to alter viscos-ity and clotting, both during and af-ter the operation, is controversial;there is no high-quality scientific ev-idence to guide the surgeon. Aspirin,heparin, and dextran are used fre-quently. Conrad and Adams29 havepublished a useful review of pharma-cology in microsurgery.

Postoperatively, the patient oftenis kept intubated and sedated over-night to minimize fluctuations inblood pressure and to allow an expe-ditious return to the operating roomshould reexploration of the flap benecessary.

Adequate perfusion of the freetissue transfer can be monitoredthrough clinical observation orthrough adjuncts such as laser orimplantable Doppler probes, which

may give an early indication of flapperfusion problems and enhance theflap salvage rate. Arterial insufficien-cy is indicated by a pale, cool flapwith delayed capillary refill and fail-ure to bleed upon pin prick. Venousinsufficiency leads to a blue,mottledcolor with immediate capillary refilland swelling of the flap. Arterial in-sufficiency is an indication for im-mediate return to the operatingroom, as is venous insufficiency inmost cases. Flap congestion may berelieved by the removal of selectedsutures, changes in position, or theloosening of constricting dressings;however, when immediate improve-ment is not noted, emergency explo-ration is mandatory.

On return to the operating room,the pedicle is inspected for kinking,torsion, or compression, and anylarge hematomas are removed. Pa-tency of the pedicle is checked by vi-sual inspection, aided by a sterileDoppler probe. When there is noother obvious reversible problem,the anastomosis may need to be re-done. As a last resort, a thrombolyt-ic agent, such as streptokinase, maybe injected into the artery of thepedicle to break down any thrombiin the vascular bed. However, it isimportant to disconnect the venousoutflow before doing this in order toprevent systemic administration ofthe agent.

Early return to the operatingroom allows the salvage of >50% ofcompromised flaps.9

Complications of FreeTissue Transfer

The most serious complication isfailure of the flap (ie, ischemic necro-sis of the tissue). Flap failure occursmore frequently early in the sur-geons experience. Different tissueshave varying tolerance for ischemia.Muscle flaps are the least tolerant,and failure to reestablish effectiveperfusion by 2 hours usually resultsin irreversible insult to the muscle.Skin, fascia, and bone have greater

tolerance to ischemia, but ischemictime should always be minimized.

Free tissue transfer inevitably re-sults in some donor morbidity, andflaps are carefully chosen to mini-mize this. For example, an anterolat-eral thigh flap leaves a large defectthat may be cosmetically unaccept-able in a young female but wouldhave little aesthetic consequence ina male. Endoscopic harvesting oftissue can decrease donor-site scar-ring.

Themuscle flaps that are routine-ly used typically result in little lossof function. The gracilis is entirelyexpendable. Loss of the latissimusdorsi is compensated for by the re-maining shoulder girdle muscles.

Harvest of a large flap and cre-ation of a large raw surface may re-sult in seroma formation, which ismost commonly seen with the latis-simus dorsi flap. The seromamay betreated with repeated aspirations orexcision if encapsulated.

The most common serious com-plication of a vascularized bonetransfer is nonunion. Bishop30 founda primary union rate of 68% for vas-cularized fibular grafts, which in-creased to 82%with supplementarybone graft.

Future Directions

The ultimate example of matchinglike with like is allograft handtransplantation. This provides theonlymeans of replacing themultiplecomplex structures within the hand.The main obstruction to use of thistechnique, outside the experimentalsetting, is the need for ongoing im-munosuppression to prevent rejec-tion of the allograft. Presently thereis intense research interest in thefield of immunomodulation to over-come this problem.31

Summary

Free tissue transfer can provide supe-rior functional and aesthetic resultsin a variety of posttraumatic and



elective settings. Refinements in in-dications and technique have result-ed in higher rates of flap survival andimproved results.

The primary indication for freetissue transfer in the emergency set-ting is to cover exposed vital struc-tures. In the elective setting, freetissue transfer can be used toreconstruct segmental defects, treatchronic deep-seated infection, re-place lost function with free muscletransfer, and replace lost or absentdigits.

Free tissue transfer is a demand-ing surgical procedure; careful atten-tion to detail from both the surgeonand anesthesiologist is necessary tomaximize flap survival. Physiologicparameters must be closely moni-tored, hydration and temperature op-timized, and pain controlled. In thesetting of a failing flap, urgent explo-ration in the operating room offersthe best chance to salvage the flap.

Acknowledgment

We thank Mr. Stan Coffman forpreparation of the figures accompa-nying the manuscript.

References

Citation numbers printed in boldtype indicate references publishedwithin the past 5 years.

1. Wei FC, Jain V, Suominen S, ChenHC: Confusion among perforatorflaps: What is a true perforator flap?Plast Reconstr Surg 2001;107:874-876.

2. Lister G, Scheker L: Emergency freeflaps to the upper extremity. J HandSurg [Am] 1988;13:22-28.

3. Gillies H, Millard DR: The Principlesand Art of Plastic Surgery. Boston,MA: Little & Brown, 1957.

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06. principles of free tissue transfer in orthopaedic practice

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