SURGERY
How to Perform Amputation of the Equine Limb
Using 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, Wyoming
82801 (Vlahos and Hawkins); and 31624 Wrightwood Road, Bonsall, California 92003 (Grant);
e-mail:[email protected]. © 2010 AAEP.
1.
Introduction
Amputation of the equine limb has been performed
for the past four decades.1– 6 Previous reports indicate that, in cases where fracture configuration,
impaired circulatory status, or sepsis render traditional means of limb repair hopeless, amputation
should be considered as a viable option to euthanasia.1,2 As experience has been gained in surgical
technique, and prosthetic designs have become routine, removal of the diseased limb can no longer be
considered an abstract, controversial procedure.
In addition, recent, high-profile cases of catastrophic
limb failure in Thoroughbred racehorses have
sparked an interest in the procedure from both the
public and the insurance industry.a In a previous
report of 30 cases involving distal limb amputation,
both a caudal flap technique and frog graft were
used with good results.1 The frog graft technique
can be used in cases where insufficient tissue is
available for a caudal flap or in cases where frog
chorium can be transposed as a local flap. The
disadvantages 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 Unlike the human amputee, which will be non–weight
bearing on the affected limb until the stump healing
is complete, the equine patient must be able to
weight bear immediately after surgery. The caudal
flap technique provides an excellent opportunity for
primary healing and rapid stump loading.
The purpose of this paper is to provide the equine
surgeon with a step-by-step approach to removal of
the limb with rapid return to function.
2.
Materials and Methods
Case Selection
Amputation of the diseased limb has been routinely
performed up to the level of the proximal metacarpus/metatarsus.1– 6 The authors have performed
amputations in horses ranging in age from 2 mo to
20 yr. Case selection should include horses with a
temperament to allow sling recovery during anesthesia and cast changes. In addition, horses that
undergo upper hind limb amputations should be
expected to tolerate a rigid cast and prosthesis that
immobilizes the hock. An important factor in selecting candidates for amputation is having owners
and caretakers that are dedicated to the long-term
maintenance of the horse. Owners should anticipate the equine amputee to perform without limita-
NOTES
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Proceedings of the Annual Convention of the AAEP – Baltimore, MD, USA, 2010
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SURGERY
tions as a breeding or pasture animal. Breeding
stallions should be expected to perform with either a
forelimb or hindlimb removed, and broodmares can
be expected to accommodate the weight associated
with gestation.1,2,b Pregnant mares have undergone
amputation and delivered healthy foals.1 Horses
up to 600 kg have been included in reported
cases.1– 6
Contralateral limb laminitis is a universal concern in the non–weight-bearing patient and in the
postoperative fracture patient. All amputee candidates are provided with frog support during the
course of their injuries and immediately after surgery. Although traditional rationale would disqualify a horse as a candidate for amputation once
laminitis has developed in the contralateral limb,
one of the authors (T.P.V.) has had occasion to remove the original painful limb just to have moderate
laminitis resolve in the contralateral limb. Therefore, one cannot always exclude horses as candidates
with contralateral limb laminitis, although a careful
case by case assessment should be made.
In selecting the level of amputation, every effort
should be made to preserve the nutrient artery in
the affected limb. Enough soft tissue covering on
the caudal aspect of the limb should be intact and
extend 2.5 times the width of the bone in a distal
Fig. 2. Appearance of applied temporary upper hind limb prosthesis immediately after surgery.
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 Prosthesis
The patient is prepared for surgery in a routine
manner. In all forelimb and hindlimb cases where
the site of amputation is at or below the level of the
fetlock joint, a transfixation cast is used in the immediate postoperative period. In hind limb cases
above the fetlock, a cast will be applied to just below
the stifle. A transfixation cast is not necessary in
these cases because the angle of the hock will allow
sufficient weight bearing on the cranial aspect of the
tibia, thus requiring minimal loading of the stump
until primary healing of the incision is complete.
The temporary prosthesis in the upper hind limb
cases will include four straps that incorporate into a
titanium post (Fig. 2). This is coupled to a foot
plate of 0.25-in stainless steel with borium. The
forelimb and distal hindlimb cases incorporate an
aluminum cup into the transfixation cast, which
permits rotation of the limb while minimizing shearing stresses at the bone–pin interface (Fig. 3).
All horses are provided preoperative broad-spectrum antimicrobials, non-steroidal anti-inflammatory drugs (NSAIDS), and tetanus prophylaxis.
Surgical Procedure
Fig. 1. Appearance of a preoperative limb with sufficient tissue
for a caudal flap.
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The horse is placed under general anesthesia and is
positioned in dorsal recumbency to allow access to
the entire limb. The diseased portion of the limb is
draped out of the surgical field. Neurectomy of the
palmar/plantar nerves is performed at a level 4 – 8
cm proximal to the site of amputation and at least 2
cm of nerve is removed. Closure of the neurectomy
sites is routine. In forelimb cases and distal hindlimb cases, two positive-profile 6.3-mm transfixation
pinsc are placed at 30° divergent angles in the distal
one third of McIII/MtIII (Fig. 4). A skin incision is
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Proceedings of the Annual Convention of the AAEP – Baltimore, MD, USA, 2010
SURGERY
Fig. 3. Temporary distal limb prosthesis that will be incorporated in a transfixation cast. The cup allows the horse to freely
rotate, thus minimizing shearing forces at the bone–pin interface.
made on the palmar/plantar aspect of the limb perpendicular to the long axis of the bone and distal to
the site of amputation at a distance of 2.5 times the
width of the bone at the amputation site. The incision extends in a cranial direction on both the
medial and lateral aspects of the limb. Care should
be taken to ensure that the medial and lateral aspects of the incision are symmetrical. As the incision reaches the middle of the limb, it is extended
proximal to the site of amputation and then horizontal to complete the dorsal margin of the incision.
Blood vessels are double ligated with absorbable
suture and transected. The superficial digital
flexor tendon, deep digital flexor tendon, and suspensory ligaments are sharply transected at the
level of the caudal incision and are not separated
from the skin and subcutaneous tissue. The extensor tendons are similarly transected at the skin margin on the dorsal aspect of the limb. The caudal
skin, tendons, suspensory ligament, and vascular
bundle are carefully dissected from the bone in a
proximal direction to the level of the amputation
(Fig. 5). In cases where the amputation is performed at the fetlock or pastern joint, the joint is
simply disarticulated at this time. If the fetlock
joint is the site of amputation, the sesamoid bones
should be preserved to allow a bulbous stump end,
which will prevent spinning and slippage of the permanent prosthesis. Cold fluids are used for irrigation during the amputation with an oscillating saw
to prevent overheating of the cortical bone. Once
Fig. 4.
MtIII.
Placement of transfixation pins in the distal one third of
Fig. 5. Caudal flap dissected free from MtIII immediately before
amputation.
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Proceedings of the Annual Convention of the AAEP – Baltimore, MD, USA, 2010
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SURGERY
Fig. 7. Closure of stump as flexor tendons and suspensory ligament are sutured to extensor tendons.
Aftercare
Fig. 6. Arthroburr is used to remove sharp edges from amputated MtIII. The caudal flap is 2.5 times in length as the MtIII
is wide. This allows sufficient coverage of the bone and closure
with minimal tension on sutured ends of the tendons and skin.
the limb is removed, a bone rasp or arthroburr is
used to smooth the edges of the bone (Fig. 6), and
bone wax is applied to control hemorrhage. The
caudal flap is positioned for closure. The suspensory ligament and flexor tendons are sutured to the
extensor tendons in a modified compound locking
loop pattern using size 2 monofilamentd (Fig. 7).
A 0.5-in penrose drain is placed in the subcutaneous
space to exit through a separate stab incision, and
the skin is closed using 0 polydioxanonee in an interrupted vertical mattress pattern and oversewn
with surgical staples. If transfixation pins were
placed, they are cut to appropriate length at this
time 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 the
stump. Absorbent cast linerf is applied to the limb
at this time, and the transfixation cast and temporary prosthesis are applied. The patient is transported to the recovery stall for a sling-assistedg
recovery. Hoof acrylic and support shoeing of the
contralateral limb is verified at this time. Once the
horse recovers in the sling, the sling is removed, and
the horse is expected to walk unassisted to his stall.
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The horse is maintained on broad-spectrum antimicrobials and NSAIDS for 7 days. Two weeks after surgery, the horse is placed in a sling, and the
cast is changed under IV anesthesia. Thirty days
after surgery, the sling is again used, and the transfixation cast and pins are removed under IV anesthesia. Molding of the permanent prosthesish is
done at this time. The healed stump can accommodate loading without risk of incisional failure, and a
simple cast/temporary prosthesis is applied. Once
the permanent prosthesis is constructed (1–2 wk),
the cast is removed with the horse standing, and the
permanent prosthesis is applied (Fig. 8). The prosthesis is changed daily using a wool prosthetic sock.i
Care should be taken to ensure that the leg is dry
and free of pressure sores at every cast change.
Fig. 8. Appearance of typical amputee 60 days after surgery
with permanent prosthesis made of graphite and polypropylene
with titanium pylon and a stainless steel and borium footplate.
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Proceedings of the Annual Convention of the AAEP – Baltimore, MD, USA, 2010
SURGERY
The horse can be turned out into a corral and resume controlled exercise.
3.
Results
From 1986 –2010, thirty four clinical cases of partial limb amputation using a caudal flap technique
were reviewed. Twenty-two of the 34 cases were
previously reported by the authors. Twenty-two
horses (64.7%) survived at least 6 mo (mean, 31.1
mo). Age at amputation ranged from 2 mo to 13
yr (mean, 7.2 yr). Septic arthritis/tenosynovitis
was the most common cause of amputation (53%).
Chronic pain patients (n ⫽ 24) comprised a majority
of the cases compared with horses with an acutely
injured limb (n ⫽ 10). Of horses that survived, 7
were salvaged for sentimental value, 13 were broodmares, and 2 were breeding stallions.
4.
Discussion
The goal of amputation is to remove an irreparably
painful or unstable limb and return the horse to
function as rapidly as possible. In restoring function, it is important to maintain comfort and promote primary closure of the stump. Unlike the
human amputee, who will undergo several months
of muscle atrophy and stump sclerosis, this is not a
significant issue with the distal limb in the horse.
Once stump healing is complete, the morbidity associated with amputation is minimal.1–3,5,6 As in
humans, performing a high neurectomy facilitates a
rapid return to comfort. Neuroma formation did
not develop in any of the cases in this study. Phantom pain, a poorly understood syndrome in the humans, has been described in horsesb but did not
develop in any of the cases in this study. Application of the caudal flap allows a firm, tough pad of
tissue on the end of the bone. Transfixation casting
was used by one of the authors (T.P.V.) in six of six
distal limb cases, of which five resulted in primary
closure. In cases where primary closure did not
occur, the stump was allowed to heal by second
intention. Of horses that did not survive at least 6
mo, four developed contralateral laminitis, one perforated her right dorsal colon, one horse fractured
above her prosthesis, and one broodmare was euthanized after aborting.
Amputation in itself is not a difficult procedure.
It does require facilities that provide for sling-assisted recovery and follow-up care. An experienced
staff is essential in the postoperative period. Most
horses tolerate the procedure and aftercare extremely well. In the initial limb changes, some
horses become anxious with the prosthesis removed
simply because of a loss of proprioception in the
limb. This is easily remedied by placing a cupped
hand on the stump and applying upward pressure.
Horses will tolerate bathing of the limb and drying
with an electric hair dryer. A well-fitted prosthesis
cannot be overemphasized. As in humans, a loose
prosthesis is one that will cause pressure sores.
Excess padding is therefore detrimental and should
be avoided. A clean wool prosthetic sock will absorb moisture and keep the limb dry. The most
frequent complications with the prosthesis itself are
broken straps, which can easily be replaced.
Partial limb amputation using a caudal flap technique provides for a firm pad of tissue on which the
horse can load. A transfixation cast can be used in
cases including and below the fetlock joint to facilitate primary stump healing. As in humans, a high
neurectomy provides comfort to the equine amputee
and has not resulted in any significant complications. Morbidity associated with the catabolic state
of the chronic pain patient can be decreased by recognizing the availability of amputation as a viable
treatment option early in the course of managing the
horse with a limb beyond repair.
References and Footnotes
1. Vlahos TP, Redden RF. Amputation of the equine distal
limb: indications, techniques and long-term care. Equine
Vet Educ 2005;17:212–217.
2. Grant BD. Amputation and prosthetic devices. In: Colahan PT, Merritt AM, Moore JN, et al., eds. Equine medicine
and surgery, 5th ed. St. Louis: Mosby, 1999;1406 –1407.
3. Crawley GR, Grant BD, Krpan MK, et al. Long-term follow-up of partial limb amputation in 13 horses. Vet Surg
1989;18:52–55.
4. Herthel DJ. Application of the interlocking intramedullary
nail. In: Nixon AJ, ed. Equine fracture repair. Philadelphia: WB Saunders, 1996;373–375.
5. Koger LM. Limb amputation and prosthetic devices. In:
Mannsman TS, McCallister ES, eds. Equine medicine and
surgery, 3rd ed. Santa Barbara, CA: American Veterinary
Publications, 1982;1026 –1028.
6. Krpan MK, Grant BD, Crawley GR, et al. Amputation of the
equine limb: a report of three cases, in Proceedings. 31st
Annual Meeting of the American Association of Equine Practioners 1986;429 – 444.
a
R. Jones. Personal communication, 2009.
R. F. Redden. Personal communication, 2009.
c
Imex Veterinary, Longview, TX 75604.
d
Prolene, Ethicon, Somerville, NJ 08876.
e
PDS-II, Ethicon, Somerville, NJ 08876.
f
Procel Cast Liner, WL Gore and Associates, Flagstaff, AZ
86003.
g
Anderson Sling, CDA Products, Potter Valley, CA 95469.
h
Hanger Prosthetics and Orthotics, Sheridan, WY 82801.
i
Knit-Rite, Knit-Rite, Kansas City, KS 66105.
b
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