levels of amputation

When a surgeon decides where to cut, the choice is not arbitrary. Think of a tree branch: the closer to the trunk you saw, the less of the branch is left to do useful work. The level of amputation — how much limb is removed and which joints are kept — is one of the single biggest predictors of how well a person will walk or use an arm afterwards. Keeping a joint, especially the knee, is worth a great deal.

Levels are named by the bone segment cut through and the joints preserved. In the leg, from lower to higher: partial foot (part of the foot removed); transtibial or below-knee (through the shin bones, knee kept); knee disarticulation (through the knee joint); transfemoral or above-knee (through the thigh bone, knee lost); and hip disarticulation (the whole leg removed at the hip). In the arm: partial hand; transradial or below-elbow (forearm); transhumeral or above-elbow; and shoulder disarticulation. The general rule is that more length and more preserved joints mean a lighter prosthesis, easier control, and lower energy cost.

The surgeon balances two competing pressures. Going lower preserves precious function, but the tissue there must have enough blood supply to heal and enough padding to tolerate a prosthesis; cutting through dying or poorly supplied tissue means the wound breaks down and a second, higher operation is needed. In vascular disease this trade-off is delicate. The knee is the pivotal landmark: a below-knee amputee, keeping their own knee, typically walks far more easily and with much less energy than an above-knee amputee, which is why surgeons fight to save the knee whenever healing allows.