How to Perform Amputation of the Equine LimbUsing a Caudal Flap Technique

Ted P. Vlahos, DVM, MS, Diplomate ABVP;Barrie D. Grant, DVM, MS, Diplomate ACVS; and Howard A. Hawkins, DVM

Authors’ addresses: Sheridan Equine Hospital, PC, 510 College Meadows Drive, Sheridan, Wyoming82801 (Vlahos and Hawkins); and 31624 Wrightwood Road, Bonsall, California 92003 (Grant);e-mail:drv@sheridanequine.com. © 2010 AAEP.

1. Introduction

Amputation of the equine limb has been performedfor the past four decades.1–6 Previous reports indi-cate that, in cases where fracture configuration,impaired circulatory status, or sepsis render tra-ditional means of limb repair hopeless, amputationshould be considered as a viable option to euthana-sia.1,2 As experience has been gained in surgicaltechnique, and prosthetic designs have become rou-tine, removal of the diseased limb can no longer beconsidered an abstract, controversial procedure.In addition, recent, high-profile cases of catastrophiclimb failure in Thoroughbred racehorses havesparked an interest in the procedure from both thepublic and the insurance industry.a In a previousreport of 30 cases involving distal limb amputation,both a caudal flap technique and frog graft wereused with good results.1 The frog graft techniquecan be used in cases where insufficient tissue isavailable for a caudal flap or in cases where frogchorium can be transposed as a local flap. Thedisadvantages in the frog graft technique include (i)graft failure and (ii) excessive growth of grafted frog,which can result in a poor-fitting prosthesis.1,b Un-like the human amputee, which will be non–weight

bearing on the affected limb until the stump healingis complete, the equine patient must be able toweight bear immediately after surgery. The caudalflap technique provides an excellent opportunity forprimary healing and rapid stump loading.

The purpose of this paper is to provide the equinesurgeon with a step-by-step approach to removal ofthe limb with rapid return to function.

2. Materials and Methods

Case SelectionAmputation of the diseased limb has been routinelyperformed up to the level of the proximal metacar-pus/metatarsus.1–6 The authors have performedamputations in horses ranging in age from 2 mo to20 yr. Case selection should include horses with atemperament to allow sling recovery during anes-thesia and cast changes. In addition, horses thatundergo upper hind limb amputations should beexpected to tolerate a rigid cast and prosthesis thatimmobilizes the hock. An important factor in se-lecting candidates for amputation is having ownersand caretakers that are dedicated to the long-termmaintenance of the horse. Owners should antici-pate the equine amputee to perform without limita-

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tions as a breeding or pasture animal. Breedingstallions should be expected to perform with either aforelimb or hindlimb removed, and broodmares canbe expected to accommodate the weight associatedwith gestation.1,2,b Pregnant mares have undergoneamputation and delivered healthy foals.1 Horsesup to 600 kg have been included in reportedcases.1–6

Contralateral limb laminitis is a universal con-cern in the non–weight-bearing patient and in thepostoperative fracture patient. All amputee candi-dates are provided with frog support during thecourse of their injuries and immediately after sur-gery. Although traditional rationale would dis-qualify a horse as a candidate for amputation oncelaminitis has developed in the contralateral limb,one of the authors (T.P.V.) has had occasion to re-move the original painful limb just to have moderatelaminitis resolve in the contralateral limb. There-fore, one cannot always exclude horses as candidateswith contralateral limb laminitis, although a carefulcase by case assessment should be made.

In selecting the level of amputation, every effortshould be made to preserve the nutrient artery inthe affected limb. Enough soft tissue covering onthe caudal aspect of the limb should be intact andextend 2.5 times the width of the bone in a distal

direction from the proposed site of amputation (Fig.1). If insufficient soft tissue is available for a flap,another method such as a frog graft may be used.

Patient Preparation/Temporary ProsthesisThe patient is prepared for surgery in a routinemanner. In all forelimb and hindlimb cases wherethe site of amputation is at or below the level of thefetlock joint, a transfixation cast is used in the im-mediate postoperative period. In hind limb casesabove the fetlock, a cast will be applied to just belowthe stifle. A transfixation cast is not necessary inthese cases because the angle of the hock will allowsufficient weight bearing on the cranial aspect of thetibia, thus requiring minimal loading of the stumpuntil primary healing of the incision is complete.The temporary prosthesis in the upper hind limbcases will include four straps that incorporate into atitanium post (Fig. 2). This is coupled to a footplate of 0.25-in stainless steel with borium. Theforelimb and distal hindlimb cases incorporate analuminum cup into the transfixation cast, whichpermits rotation of the limb while minimizing shear-ing stresses at the bone–pin interface (Fig. 3).

All horses are provided preoperative broad-spec-trum antimicrobials, non-steroidal anti-inflamma-tory drugs (NSAIDS), and tetanus prophylaxis.

Surgical ProcedureThe horse is placed under general anesthesia and ispositioned in dorsal recumbency to allow access tothe entire limb. The diseased portion of the limb isdraped out of the surgical field. Neurectomy of thepalmar/plantar nerves is performed at a level 4–8cm proximal to the site of amputation and at least 2cm of nerve is removed. Closure of the neurectomysites is routine. In forelimb cases and distal hind-limb cases, two positive-profile 6.3-mm transfixationpinsc are placed at 30° divergent angles in the distalone third of McIII/MtIII (Fig. 4). A skin incision is

Fig. 1. Appearance of a preoperative limb with sufficient tissuefor a caudal flap.

Fig. 2. Appearance of applied temporary upper hind limb pros-thesis immediately after surgery.

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made on the palmar/plantar aspect of the limb per-pendicular to the long axis of the bone and distal tothe site of amputation at a distance of 2.5 times thewidth of the bone at the amputation site. The in-cision extends in a cranial direction on both themedial and lateral aspects of the limb. Care shouldbe taken to ensure that the medial and lateral as-pects of the incision are symmetrical. As the inci-sion reaches the middle of the limb, it is extendedproximal to the site of amputation and then horizon-tal to complete the dorsal margin of the incision.Blood vessels are double ligated with absorbablesuture and transected. The superficial digitalflexor tendon, deep digital flexor tendon, and sus-pensory ligaments are sharply transected at thelevel of the caudal incision and are not separatedfrom the skin and subcutaneous tissue. The exten-sor tendons are similarly transected at the skin mar-gin on the dorsal aspect of the limb. The caudalskin, tendons, suspensory ligament, and vascularbundle are carefully dissected from the bone in aproximal direction to the level of the amputation(Fig. 5). In cases where the amputation is per-formed at the fetlock or pastern joint, the joint issimply disarticulated at this time. If the fetlockjoint is the site of amputation, the sesamoid bonesshould be preserved to allow a bulbous stump end,which will prevent spinning and slippage of the per-manent prosthesis. Cold fluids are used for irriga-tion during the amputation with an oscillating sawto prevent overheating of the cortical bone. Once

Fig. 4. Placement of transfixation pins in the distal one third ofMtIII.

Fig. 3. Temporary distal limb prosthesis that will be incorpo-rated in a transfixation cast. The cup allows the horse to freelyrotate, thus minimizing shearing forces at the bone–pin interface.

Fig. 5. Caudal flap dissected free from MtIII immediately beforeamputation.

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the limb is removed, a bone rasp or arthroburr isused to smooth the edges of the bone (Fig. 6), andbone wax is applied to control hemorrhage. Thecaudal flap is positioned for closure. The suspen-sory ligament and flexor tendons are sutured to theextensor tendons in a modified compound lockingloop pattern using size 2 monofilamentd (Fig. 7).A 0.5-in penrose drain is placed in the subcutaneousspace to exit through a separate stab incision, andthe skin is closed using 0 polydioxanonee in an in-terrupted vertical mattress pattern and oversewnwith surgical staples. If transfixation pins wereplaced, they are cut to appropriate length at thistime to permit placement of a transfixation cast.A sterile bandage is applied to cover the incision,and a layer of sterile 0.5-in cast felt is applied to thestump. Absorbent cast linerf is applied to the limbat this time, and the transfixation cast and tempo-rary prosthesis are applied. The patient is trans-ported to the recovery stall for a sling-assistedg

recovery. Hoof acrylic and support shoeing of thecontralateral limb is verified at this time. Once thehorse recovers in the sling, the sling is removed, andthe horse is expected to walk unassisted to his stall.

AftercareThe horse is maintained on broad-spectrum anti-microbials and NSAIDS for 7 days. Two weeks af-ter surgery, the horse is placed in a sling, and thecast is changed under IV anesthesia. Thirty daysafter surgery, the sling is again used, and the trans-fixation cast and pins are removed under IV anes-thesia. Molding of the permanent prosthesish isdone at this time. The healed stump can accommo-date loading without risk of incisional failure, and asimple cast/temporary prosthesis is applied. Oncethe permanent prosthesis is constructed (1–2 wk),the cast is removed with the horse standing, and thepermanent prosthesis is applied (Fig. 8). The pros-thesis is changed daily using a wool prosthetic sock.i

Care should be taken to ensure that the leg is dryand free of pressure sores at every cast change.

Fig. 6. Arthroburr is used to remove sharp edges from ampu-tated MtIII. The caudal flap is 2.5 times in length as the MtIIIis wide. This allows sufficient coverage of the bone and closurewith minimal tension on sutured ends of the tendons and skin.

Fig. 7. Closure of stump as flexor tendons and suspensory liga-ment are sutured to extensor tendons.

Fig. 8. Appearance of typical amputee 60 days after surgerywith permanent prosthesis made of graphite and polypropylenewith titanium pylon and a stainless steel and borium footplate.

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The horse can be turned out into a corral and re-sume controlled exercise.

3. Results

From 1986 –2010, thirty four clinical cases of par-tial limb amputation using a caudal flap techniquewere reviewed. Twenty-two of the 34 cases werepreviously reported by the authors. Twenty-twohorses (64.7%) survived at least 6 mo (mean, 31.1mo). Age at amputation ranged from 2 mo to 13yr (mean, 7.2 yr). Septic arthritis/tenosynovitiswas the most common cause of amputation (53%).Chronic pain patients (n � 24) comprised a majorityof the cases compared with horses with an acutelyinjured limb (n � 10). Of horses that survived, 7were salvaged for sentimental value, 13 were brood-mares, and 2 were breeding stallions.

4. Discussion

The goal of amputation is to remove an irreparablypainful or unstable limb and return the horse tofunction as rapidly as possible. In restoring func-tion, it is important to maintain comfort and pro-mote primary closure of the stump. Unlike thehuman amputee, who will undergo several monthsof muscle atrophy and stump sclerosis, this is not asignificant issue with the distal limb in the horse.Once stump healing is complete, the morbidity as-sociated with amputation is minimal.1–3,5,6 As inhumans, performing a high neurectomy facilitates arapid return to comfort. Neuroma formation didnot develop in any of the cases in this study. Phan-tom pain, a poorly understood syndrome in the hu-mans, has been described in horsesb but did notdevelop in any of the cases in this study. Applica-tion of the caudal flap allows a firm, tough pad oftissue on the end of the bone. Transfixation castingwas used by one of the authors (T.P.V.) in six of sixdistal limb cases, of which five resulted in primaryclosure. In cases where primary closure did notoccur, the stump was allowed to heal by secondintention. Of horses that did not survive at least 6mo, four developed contralateral laminitis, one per-forated her right dorsal colon, one horse fracturedabove her prosthesis, and one broodmare was eutha-nized after aborting.

Amputation in itself is not a difficult procedure.It does require facilities that provide for sling-as-sisted recovery and follow-up care. An experiencedstaff is essential in the postoperative period. Mosthorses tolerate the procedure and aftercare ex-tremely well. In the initial limb changes, some

horses become anxious with the prosthesis removedsimply because of a loss of proprioception in thelimb. This is easily remedied by placing a cuppedhand on the stump and applying upward pressure.Horses will tolerate bathing of the limb and dryingwith an electric hair dryer. A well-fitted prosthesiscannot be overemphasized. As in humans, a looseprosthesis is one that will cause pressure sores.Excess padding is therefore detrimental and shouldbe avoided. A clean wool prosthetic sock will ab-sorb moisture and keep the limb dry. The mostfrequent complications with the prosthesis itself arebroken straps, which can easily be replaced.

Partial limb amputation using a caudal flap tech-nique provides for a firm pad of tissue on which thehorse can load. A transfixation cast can be used incases including and below the fetlock joint to facili-tate primary stump healing. As in humans, a highneurectomy provides comfort to the equine amputeeand has not resulted in any significant complica-tions. Morbidity associated with the catabolic stateof the chronic pain patient can be decreased by rec-ognizing the availability of amputation as a viabletreatment option early in the course of managing thehorse with a limb beyond repair.

References and Footnotes1. Vlahos TP, Redden RF. Amputation of the equine distal

limb: indications, techniques and long-term care. EquineVet Educ 2005;17:212–217.

2. Grant BD. Amputation and prosthetic devices. In: Cola-han PT, Merritt AM, Moore JN, et al., eds. Equine medicineand surgery, 5th ed. St. Louis: Mosby, 1999;1406–1407.

3. Crawley GR, Grant BD, Krpan MK, et al. Long-term fol-low-up of partial limb amputation in 13 horses. Vet Surg1989;18:52–55.

4. Herthel DJ. Application of the interlocking intramedullarynail. In: Nixon AJ, ed. Equine fracture repair. Philadel-phia: WB Saunders, 1996;373–375.

5. Koger LM. Limb amputation and prosthetic devices. In:Mannsman TS, McCallister ES, eds. Equine medicine andsurgery, 3rd ed. Santa Barbara, CA: American VeterinaryPublications, 1982;1026–1028.

6. Krpan MK, Grant BD, Crawley GR, et al. Amputation of theequine limb: a report of three cases, in Proceedings. 31stAnnual Meeting of the American Association of Equine Prac-tioners 1986;429–444.

aR. Jones. Personal communication, 2009.bR. F. Redden. Personal communication, 2009.cImex Veterinary, Longview, TX 75604.dProlene, Ethicon, Somerville, NJ 08876.ePDS-II, Ethicon, Somerville, NJ 08876.fProcel Cast Liner, WL Gore and Associates, Flagstaff, AZ

86003.gAnderson Sling, CDA Products, Potter Valley, CA 95469.hHanger Prosthetics and Orthotics, Sheridan, WY 82801.iKnit-Rite, Knit-Rite, Kansas City, KS 66105.

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