Abstracts / Journal of Equine Veterinary Science 33 (2013) 860-883 873

bone marrow-derived stem cells; otherwise, allogeneicUCB-derived MSCwere used for subsequent treatments. Allcases were treated at 1-month intervals for up to 4treatments.

stem cell administrationThe stem cells were suspended in sterile saline andadministered via retrograde venous digital perfusion, usingthe palmar/plantar digital vein. Each patient was sedatedwith detomidine and perineural anesthesia performed atthe basisesamoid level with 2%mepivacaine hydrochloride.A tourniquet made from surgical tubing was placed aroundthe metacarpophalangeal joint and the skin over themedial or lateral palmar/plantar digital veinwas asepticallyprepared.A 21-ga, ¾ -in. butterfly catheter was placed into the digitalvein and the limb slowly perfused with the MSC suspen-sion. The foot was unweighted during at least half of theinjection process. The tourniquet was left in place for 25–30minutes after completion of the infusion. Followingremoval of the tourniquet and catheter, the limb wasbandaged.Results: The time from onset of laminitis to first MSCtreatment varied: < 30 days (10 cases), 30–60 days (4cases), 60–90 days (2 cases), and > 90 days (14 cases). Eachcase received 1 to 4 treatments with MSC per affected foot,most receiving 3 or 4 treatments. Deep digital flexortenotomy was performed on at least 1 affected limb in 15patients (50%).Of the 30 cases, 21 patients (70%) had a successfuloutcome. In the cases receiving stem cells < 30 days afterthe onset of laminitis, the success rate was 100%. Thesuccess rate in the cases receiving stem cells > 90 daysafter the onset of laminitis was only 50%. Statistical anal-ysis is pending.Discussion: The ideal timing for the first dose of stem cellsis currently unknown, although reason would argue that,for greatest benefit, MSC therapy would be most usefulbefore lamellar wedge or epidermal cell hyperplasia hasoccurred. This process takes place within 30 days of pedalbone displacement [5].In our experience, MSC therapy has no effect on theprognosis in chronic, advanced cases with bone diseaseand lamellar wedge formation. These cases maintaina thick lamellar wedge which does not change in radio-graphic appearance. However, MSC therapy has a signifi-cant effect on the prognosis in cases treated early, within30 days of the laminitic insult. The majority of these caseshave healed with a decreased distance between the boneand hoof wall (radiographically, the horn-lamellar zone).Studies are currently underway to evaluate lamellarbiopsy samples from cases treated with MSC therapy tofurther evaluate the quality of tissue which repairs thisinterface.

References

[1] Morrison SE. Foot Management. Clin Tech Equine Pract 2204;3:71–82[2] Hood DM. The mechanisms and consequences of structural failure

of the foot. Vet Clin North Am Equine Pract 1999;15:437–61.

[3] Grosenbaugh DA, Morgan SJ, Hood DM. The digital pathologiesof chronic laminitis. Vet Clin North Am Equine Pract 1999;15:419–36.

[4] Collins SN, van Eps AW, Pollitt CC, Kuwano A. The lamellar wedge.Vet Clin North Am Equine Pract 2010;26:179–95.

[5] Kuwano A, Katayama Y, Kasashima Y, et al. A Gross and histopath-ological study of an ectopic white line development in equinelaminitis. J Vet Med Sci 2002;64:893–900.

[6] Lacitignola L, Crovace A, Rossi G, Francioso E. Cell therapy fortendinitis, experimental and clinical report. Vet Res Commun 2008;32:33–8.

[7] Smith RK. Mesenchymal stem cell therapy for equine tendinopathy.Disabil Rehabil 2008;30:1752–8.

[8] Watts AE, Yeager AE, Kopyov OV, Nixon AJ. Fetal derived embryonic-like stem cells improve healing a large animal flexor tendonitismodel. Stem Cell Res Ther 2011;2:4.

[9] Caniglia CJ, Schramme MC, Smith RK. The effect of intralesionalinjection of bone marrow derived mesenchymal stem cells andbone marrow supernatant on collagen fibril size in a surgicalmodel of equine superficial flexor tendonitis. Equine Vet J 2012;44:587–93.

[10] McIlwraith CW, Frisbie DD, Rodkey WG, et al. Evaluation of intra-articular mesenchymal stem cells to augment healing of micro-fractured chondral defects. Arthroscopy 2011;27:1552–61.

[11] Ferris D, Kisiday J, McIlwraith CW. In vivo healing of meniscallacerations using bone marrow-derived mesenchymal stem cellsand fibrin glue. Stem Cells Int 2012;2012:691605.

[12] Godwin EE, Young NJ, Dudhia J, Beamish IC, Smith RK. Implantationof bone marrow-derived mesenchymal stem cells demonstratesimproved outcome in horses with overstrain injury of the superfi-cial digital flexor tendon. Equine Vet J 2012;44:25–32.

[13] Carter RA, Engiles JB, Megee SO, Senoo M, Galantino-Homer HL.Decreased expression of p63, a regulator of epidermal stem cells, inthe chronic laminitic hoof. Equine Vet J 2011;43:543–51.

[14] Peroni JF, Borjesson DL. Anti-inflammatory and immunomodulatoryactivities of stem cells. Vet Clin North Am Equine Pract 2011;27:351–62.

[15] Morrison SE. Long-term prognosis using deep digital flexor tenot-omy and realignment shoeing for treatment of chronic laminitis. JEquine Vet Sci 2011;31:89–96.

[16] Bras RJ. How to use foot casts to manage horses with laminitis anddistal phalanx displacement secondary to systemic disease.Proceedings, American Association of Equine Practitioners 2011;57:415–23.

051Management of foot casts

Vernon Dryden DVM, CJF, APFRood and Riddle Equine Hospital, Lexington, KY

Take-home message: Foot casts are useful for a variety offoot disorders. Complicated laminitis cases, particularlysinkers, carry a poor prognosis but have responded totreatment with foot casts. The foot cast must be monitoredwith great care and should not be left on for longer than 4weeks at a time.Introduction: Chronic laminitis cases with distaldisplacement of the pedal bone, or “sinkers,” are verydifficult and carry a poor prognosis. Foot casts have beenshown to be effective in aiding the rehabilitation of thesecases. The foot cast provides two very important elementsnecessary for the sinker to recover: (1) the cast reducesunilateral loading and shearing forces by eliminatingcollateral movement of the hoof capsule, and (2) the domecreated on the bottom of the cast reduces torsional forcesand allows the patient to choose the most comfortablestanding position.

Abstracts / Journal of Equine Veterinary Science 33 (2013) 860-883874

Application of a foot cast has been described in earlierproceedings [1]. Here we highlight some practical aspectsof particular importance.Application of the Cast: Thoroughly clean the foot andgive it a balanced trim before applying the foot cast. If thepatient is very painful, then use regional anesthesia (nerveblocks) as necessary. Alternatively, apply the foot casts withthe patient in lateral recumbency, under heavy sedation orgeneral anesthesia.Choose an area for cast application that is clean and dry,and neither too hot nor too cold. If the horse is standing, itis important that the limb be in full weight-bearing posi-tion before the cast sets, otherwise cast sores may developon the dorsal or palmar aspect of the pasternwhen the limbis under load.The top of the cast should come to the base of the fetlock.When wrapping the cast tape, it is very important not topull the material too tight or it will cause discomfort andpossibly reduce circulation in the distal limb. Once thecast is set, dome the bottom of the cast as previouslydescribed [1], to facilitate breakover and reduce torsionalforces.Monitoring: Pay close attention to ensure that thepatient is wearing the cast well. Evaluate the cast at leastonce a day, looking for abnormal swelling, odor,discharge/drainage, and any reduction in the patient’scomfort. If cast sores have developed or the patient is notwearing the cast well, remove the cast, assess, and reap-ply if necessary.Duration: The treatment goals are different for eachpatient, so how long the cast should be left in place variesfrom case to case. Typically in sinker cases, the foot cast isleft on for 3–4 weeks at a time and reapplied as often asneeded until the new hoof wall growth is at least 50% of thelength of the wall. Once the patient reaches this point,a transition is made to a wooden clog-type shoe for anadditional 4–6 months (with the shoes reset every 4–5weeks or so).Complications: Complications can and do arise whenusing foot casts, and are usually mechanical or septic. Castrubs or sores are by far the most common complication.They occur most often at the dorsal and palmar aspects ofthe pastern and over the heel bulbs.When dealing with severely compromised feet, thepossibility of sepsis is always increased. Often, the septicarea within the hoof can be identified and a port madethrough the cast to treat the problem area. Sterile-maggotdebridement therapy through such a port or windowplaced in the cast is an easy and effective way to treatareas of sepsis within the foot. In addition, perfusion ofthe digit with antibiotics (regional limb perfusion) ispossible, even while the patient is wearing the foot cast,as the palmar/plantar vein can be catheterized proximalto the cast.

Reference

[1] Bras RJ. Management of distal displacement of P3 (“sinking”) withfoot casts. J Equine Vet Sci 2011;31:573–7.

052The suspensory apparatus of the distal phalanx (SADP)

C.C. Pollitt, and S.N. CollinsAustralian Equine Laminitis Research Unit, School ofVeterinary Science, The University of Queensland,Australia

Take-home message: Understanding the SADP is essentialif strategies for rehabilitating the laminitic foot are tosucceed. The principal load-bearing structure of the normalfoot is the hoof wall, not the sole, so removal of the hoofwall’s bearing border to deliberately load the sole has noanatomical legitimacy and is contraindicated.Introduction: The inner layer of the equine hoof consistsof numerous proximal-to-distal oriented epidermallamellae that interface with complementary dermallamellae. The surface area of the lamellar layer is vastlyincreased by a structural hierarchy of primary andsecondary lamellar components. The hoof wall and itsinternal lamellae form the main load-support system of theequine foot and participate, via the suspensory apparatus ofthe distal phalanx (SADP), in achieving painless forcetransfer between the hoof and the appendicular skeletonduring weight-bearing.The SADP as a constituent of the equine foot is defined as allof the connective tissue and epidermal structures involvedin the transfer of weight or force from the distal phalanx(DP) to the hoof wall [1]. The corium, or dermis, betweenthe parietal surface of the DP and the lamellar epidermis ofthe inner wall is an integral component of the SADP.Bundles of collagenous fibers radiate from the DP surface inan oblique, distal-to-proximal direction and penetratebetween primary and secondary epidermal lamellae wherethey attach.The SADP radiating from the tip of the DP is fan-shaped [2],with proximal collagen bundles of the fan projectingupwards, the middle portions horizontally, and the lowerportions oriented distally. The distalmost bundles of the fanterminate in the dermis of the terminal papillae, on thedistal borders of the dermal lamellae, and serve as exten-sions of the deep flexor tendon to anchor the DP.The vital suspensory function of the SADP is illustratedwhen laminitis causes it to fail. Instead of being suspendedcomfortably within the hoof capsule, the DP sinks below itsattachments, resulting in varying degrees of discomfort andpain. Here we revisit the pioneering work of the Budrasgroup [2,3] and use special stains, bone decalcification, andnew section orientations to further investigate the SADP ofthe equine foot.Material and Methods: The feet of 6 normal Standard-bred horses humanely killed at a local abattoir weresectioned into blocks along the sagittal plane, mid-dorsalhoof wall transverse plane (the traditional plane), orobliquely along planes aligned with the long axis of SADPcollagen bundles. Excess hard horn was trimmed from the20 x 20 x 5 mm blocks before 21 days’ treatment inStewart’s formic acid decalcifying solution. Thereafter, thetissues underwent alcohol dehydration, paraffin wax