Hindfoot Amputation Whereas some authors have reported reasonable
functional outcomes with hindfoot amputation, ie, Chopart’s or Boyd’s,
especially in children, the functional outcome is generally poor at these
levels. Most patients with hindfoot amputation retain an inadequate lever
arm, and are prone to develop significant equinus. In addition, they lack
push-off at terminal stance.
Ankle Disarticulation (Through-Ankle, Syme’s) This is a durable
amputation level that allows direct load transfer and is rarely complicated
by late residual limb ulcers or tissue breakdown in young traumatic
amputees. It provides a stable gait pattern that rarely requires
postoperative gait training. Previously, it had been suggested that a
Syme’s amputation be done in two stages. However, recent data suggest that
it can be performed in one stage, even in ischemic limbs with insensate
heel pads. The malleoli and metaphyseal flares should be removed from the
tibia and fibula, but the remaining tibial articular surface should be
retained to provide a resilient residual limb. The heel pad should be
secured to the tibia via drill holes, either anteriorly or posteriorly.
Transtibial (Below-Knee) The long posterior myocutaneous flap is
preferred to sagittal flaps in transtibial amputation. Optimal bone length
is 12 to 15 cm below the knee joint, or longer if adequate gastrocnemius or
soleus can be used to construct a functional soft-tissue envelope
comprising a mobile muscle mass and full-thickness skin. Posterior muscle
should be secured to the beveled anterior tibia by myoplasty or myodesis.
Rigid dressings should be used during the early postoperative period, and
weightbearing should be initiated between 5 and 21 days following surgery
if the residual limb is capable of transferring load. Young active
transtibial amputees have the greatest benefit from the new technology,
including flexible sockets, silicone liner suction, suspension, and dynamic
Knee Disarticulation (Through-Knee) Knee disarticulation is
performed using sagittal skin flaps and covering the end of the femur with
gastrocnemius to act as a soft-tissue envelope end pad. This level is
generally performed in the nonambulator who can support wound healing at
the transtibial, or distal level. This level is muscle-balanced, and it
provides an excellent weightbearing platform and lever arm for transfer.
When performed in a potential walker, it provides a direct load transfer
residual limb that can take advantage of the intrinsically stable
polycentric four-bar linkage prosthetic knee joint.
Transfemoral (Above-Knee) This level provides significant problems
in energy cost for walking. Transfemoral amputees who have peripheral
vascular disease are unlikely to be prosthetic ambulators. Salvaging the
limb at the knee disarticulation, or transtibial level is essential to
allow potential prosthetic ambulation in geriatric, dysvascular amputees.
The optimal transfemoral bone length is 12 cm above the knee joint to
accommodate the prosthetic knee. Adductor myodesis maintains normal femoral
adduction during stance phase, allowing optimum prosthetic function.
Ischial containment sockets improve comfort and suspension, but waist
belts of various types are frequently necessary. Although suction
suspension remains the primary mode of suspension, silicone liners, much
like those used in transtibial amputation, may be used.