transfemoral (above-knee) amputation
/ tranz-FEM-or-ul /
A transfemoral amputation removes the leg above the knee, cutting through the thigh bone (the femur) and sacrificing the knee joint along with everything below it. The loss of the knee is the defining fact of this level: the person must now rely on a prosthetic knee they cannot feel, and on the muscles of the hip and the residual thigh to control a much longer, heavier artificial limb. Walking is achievable but is a bigger task than below the knee.
The surgeon shapes a residual thigh that ends in a rounded, muscle-padded stump. A crucial surgical step is myodesis or myoplasty — anchoring the cut thigh muscles to the bone or to each other under tension — so the muscles keep their pulling power and the residual limb can actively press the prosthesis into walking rather than dangling uselessly. A well-balanced thigh that does not drift into a fixed bent-and-out position (a hip flexion-abduction contracture) is essential, because such a contracture makes a prosthesis almost impossible to align and use.
The trade-offs are real and worth stating plainly. The energy cost of walking jumps sharply — commonly half again to two-thirds more than normal, and even higher in older vascular patients — so some frail people find a wheelchair more practical than a prosthesis for getting around. Those who do walk depend heavily on the prosthetic knee's design and on retraining the hip to swing and stabilise the limb. The reward, for the right candidate, is upright mobility and the independence that comes with it.
An above-knee amputee learns to swing the prosthetic knee through using a small backward push of his own hip, timing each step so the artificial knee locks into a stable position the instant his heel lands and he puts weight on it.
Without a real knee, the hip and the prosthetic knee's design carry the burden of safe stepping.
A hip flexion contracture is the silent saboteur of above-knee rehabilitation: if the thigh stiffens in a bent position, no prosthesis can be aligned to let the person stand straight, so early stretching and prone lying matter enormously.