AMPUTATIONS
IN THE FOOT
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| AMPUTATION OF FOOT |
Amputation of all or a portion of the foot represents the most elemental form of foot surgery. Often it is disparaged by the surgeon, perhaps because it can be perceived as a failure of treatment. But when performed properly, amputation is truly a reconstructive procedure that can eradicate infection, correct deformity, decrease pain, and improve function.
Amputation in the foot can be
indicated in the treatment of diabetes, peripheral vascular disease, trauma, infection,
tumors, and congenital abnormalities. Foot amputation is especially common in
the diabetic population. Peripheral neuropathy, poor blood supply, and impaired
immune all function all contribute to place the diabetic patient at greater
risk for limb-threatening infection.
Both the great toe and the lesser
toes may require amputation. Toe amputation is usually performed for the treatment
of infection, ischemia, or post-traumatic deformity. The most distal level of great
toe amputation is known as a terminal Syme amputation. This procedure is indicated
for the treatment of post-traumatic nail deformity, onychomycosis, or recurrent
infection of the great toenail. With the terminal Syme amputation, the nail plate,
matrix, and eponychial folds are excised along with the distal portion of the distal
phalanx. The skin edges are then approximated without tension.
When amputating the great toe more
proximally, an effort should be made to maintain the base of the proximal phalanx
if possible. This better preserves the weight-bearing and plantar flexion function
of the first ray. It is also beneficial in the lesser toes to leave a portion
of the proximal phalanx. This allows the toe to serve as a spacer and prevent migration
of adjacent toes.
Ray Amputation
When injury or infection
involves an entire toe, resection of a single ray (the digit plus the head and
shaft of the corresponding metatarsal) can effectively treat the problem while maximizing
residual foot function. The most common ray amputations involve the first ray and
the fifth ray. By virtue of being located on the medial and lateral borders of the
foot, respectively, these are the technically easiest ray amputations to perform.
First ray amputation does affect the push-off power of the foot, but this can be
accommodated with a special orthotic shoe insert. Central ray amputations are less
common and technically more difficult owing to the paucity of soft tissue flaps
for closure.
When multiple rays are amputated,
it is referred to as a partial forefoot amputation. Although partial fore-foot amputations
can be successful, the more rays that are resected, the greater the impact on the
foot’s balance and function.
One of the most common amputations
for forefoot infections in diabetic patients and for severe forefoot trauma involves
removal of the forefoot by transecting the metatarsals to achieve a transmetatarsal
amputation. The line of skin incision is positioned more distally on the plantar
than on the dorsal aspect of the foot. This approach allows the wound closure to
be placed on the dorsum of the foot so that it will not break down with weight bearing.
It also preserves more plantar skin, which is generally better perfused and more
durable. The level of metatarsal transaction is determined by the amount of skin
available for tension-free closure. The metatarsals are transected in a smooth parabola,
with the shaft of the second metatarsal remaining the longest by a few millimeters.
In addition, the bones are beveled in a dorsal to plantar direction so that no bone
is prominent in the plantar aspect of the foot. The major advantage of this level
of amputation is that it preserves enough length to allow the patient to wear a
standard shoe using a foam filler in the toe box. Most patients with transmetatarsal
amputation are able to walk without a special prosthesis.
Chopart Amputation
A Chopart amputation is performed
at the transverse tarsal articulation through the talonavicular and calcaneocuboid
joint. It is not a commonly performed amputation procedure largely because the soft
tissues are frequently not adequate for tension-free closure, and a more proximal
amputation is required. It is also characterized by a marked tendency for late equinus
contracture owing to loss of the ankle dorsiflexors. If this level of amputation
is chosen, an Achilles tenotomy and transfer of the anterior compartment tendons
to maintain dorsiflexion must be performed as well. Patients with a Chopart amputation
require use of an ankle-foot orthosis for ambulation.
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| SYME AMPUTATION (WAGNER MODIFICATION) |
Syme Amputation
Syme described a technique for disarticulation of the ankle that preserves the heel pad. This level of amputation preserves most of the leg’s length and allows direct weight bearing on the durable skin of the plantar heel. Wagner popularized performing the Syme amputation in two stages. The first stage disarticulated the ankle but preserved the malleoli. In the second stage, the malleoli were resected to produce a lower profile residual limb that would fit easier in a prosthesis. Today, Syme amputations are usually performed in a single stage. Whether performed in one or two stages, the Syme amputation involves shelling out the talus and calcaneus from the surrounding soft tissues while preserving the heel pad. The pad is then sutured to the tibia to prevent instability. Syme amputation can be successful for the treatment of diabetic complications, gangrene, and trauma. But the heel pad must be healthy and intact for the Syme amputation to be considered. Ulceration or ischemia of the heel pad is an absolute contraindication to Syme amputation.
