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Crowe et al. Plast Aesthet Res 2019;6:4 I http://dx.doi.org/10.20517/2347-9264.2018.70 Page 3 of 15

preserves the greatest number of joints and leaves a longer lever arm, allowing for higher torque generation
and less daily energy expenditure for ambulation. However, the distal tissue must also have perfusion
sufficient to heal and soft tissue coverage must remain durable over the patient’s lifetime. In addition, a more
proximal amputation may provide better function if the most proximal joint has limited range of motion
or function. Thus, the selection of the amputation level can be complex and the decision ideally should be
made through a combined effort by the surgeon performing the amputation, the rehabilitation specialist, the
patient, and in more complex cases a reconstructive plastic surgeon.

Data regarding the comparative effectiveness of lower limb prostheses is limited and measurable outcomes
are not often standardized. Instead, we often rely on the consensus of prosthetic and rehabilitation experts.
A review of amputation levels and considerations regarding outcomes and prosthetic options are presented
below.

Transmetatarsal amputation
As its name would suggest, the transmetatarsal amputation (TMA) is performed by transecting between
[14]
the metatarsal head and base, thus salvaging the mid- and hindfoot . TMAs are most often performed in
the setting of infection, wounds or deformities of the toes or metatarsal heads. A plantar flap including the
transected flexor tendons or a fishmouth incision is used to close the surgical site and provide soft tissue
coverage to the distal foot. The precise location of amputation through the transmetatarsal is variable. For
instance, the amputation may proceed just proximal to the metatarsal head or through the foot distal to
the cuboid and cuneiform bones. A longer residual foot provides additional weight-bearing surface and less
muscle imbalance, but the quality of the soft tissue coverage should be considered.

The most common biomechanical complication of a TMA (and other midfoot amputations) is an
equinovarus deformity - a resultant imbalance between severed dorsiflexors and intact plantarflexors.
Achilles tendon lengthening should therefore be performed at the time of a TMA to reduce risk of
[15]
equinovarus deformity . Moreover, the shortened foot can be unstable during ambulation and the heel
may demonstrate excess movement in the patient’s footwear. These postoperative factors predispose to
complication - with reported rates of delayed wound healing as high as 43%-54% [16,17] and ulceration in as
[18]
many as 27% . Furthermore, a TMA by definition will reduce the moment arm of the remaining foot,
resulting in reduced ankle plantar-flexor torque generation during toe-off. As a result, patients have an
inefficient gait without the use of a prosthesis. The appropriate post-operative management of TMAs in
terms of dressings (rigid or nonrigid) and weight bearing precautions has not yet been established.

Prosthesis and orthosis for transmetatarsal amputation
After the transmetatarsal amputation has adequately healed and the patient has progressed to weight
bearing, a partial foot prosthesis or orthosis may be prescribed. There are currently several different types of
devices available to improve ambulation after partial foot amputation. A total contact in-shoe orthotic with
a metatarsal pad molded to the contour of the patient’s residual foot is used to better distribute compressive
forces along the plantar surface. A toe filler contoured to the footwear is also frequently used to prevent
excess motion during ambulation and reduce shearing forces to the plantar surface and posterior heel.
However, the use of a full-length shoe with insert and rocker bottom sole has been demonstrated to reduce
[19]
plantar pressure to a greater degree than a regular shoe with toe filler .

The truncated lever arm of the foot after transmetatarsal amputation may be mitigated by using either a
[20]
[21]
carbon-fiber inlay or steel spring integrated into the orthotic framework, thus providing additional
force during terminal stance and helping propel the limb forward. A partial food prosthesis that crosses the
ankle joint may also be used to produce additional force for push off and provide stability for patients with
[22]
impaired balance or strength . Devices range from as simple as an in-shoe orthotic to as complex as a tibial