Special medical problems of amputees are thromboembolism, pain & flexion contracture, increased mortality rate, trauma to the residual limb and ischemia in residual limbs.
The amputee is at great risk for deep venous thrombosis (15%) and pulmonary embolism (2%) postoperatively because:
- amputation often follows prolonged immobilization during treatment of the primary disease
- the operation involves ligation of large veins, causing stagnation of blood, a situation that predisposes to thrombosis.
If immediate-fit prosthetic techniques are not employed, an additional period of inactivity follows the operation, further increasing the risk of thromboembolism.
Pain & Flexion Contracture
Flexion contractures of the knee or hip occur rapidly in the painful limb because of the natural tendency to assume a flexed posture. Measures to prevent contracture are indicated preoperatively, and application of a rigid dressing postoperatively decreases the incidence of this complication.
Persistent pain in a residual limb and phantom limb pain are common. If the cause of pain is residual limb ischemia, higher amputation is the treatment. A neuroma in a residual limb can be treated by injection of a local anesthetic or excision of the neuroma. Causalgia may respond to sympathectomy. Continuous nerve sheath block using catheters placed adjacent to the transected nerve trunks at the time of surgery may reduce early postoperative pain and late phantom pain. However, introduction of infection by the catheters is a concern.
Phantom limb pain is the sensation that a painful limb is present after amputation. Most amputees experience this phenomenon to some degree. Hypotheses concerning etiology include the gate theory, the peripheral theory and the psychologic theory (hostility, guilt, and denial are interpreted as pain). Treatment is difficult; improvement has been reported using tricyclic antidepressants, transcutaneous electrical nerve stimulation (TENS), and calcitonin. The incidence and severity of phantom limb pain are increased if there has been prolonged ischemia before amputation and decreased if postoperative rehabilitation has been rapid.
Increased Mortality Rate
Five-year survival for all lower extremity amputees is less than 50%, compared with 85% for an age-matched population. Diabetic amputees have only a 40% 5-year survival. Two-thirds of all deaths are due to cardiovascular disease.
Trauma to the Residual Limb
Because their gait is relatively unstable, amputees are at increased risk for falls that may lead to fractures or other injury to the residual limb. Disruption of the wound or skin should usually be allowed to heal by secondary intent. About 3–5% of amputees experience fractures at some time, principally of the distal femur and hip. The diagnosis of fracture is overlooked or delayed in 25% of cases. Although most fractures can be successfully treated, one-half of amputees who were ambulatory before injury become wheelchair-bound afterward.
Ischemia in Residual Limbs
Progressive vascular disease results in ischemia of about 8% of transfemoral amputations and 1% of transtibial amputations. Operations are often required to improve arterial flow when gangrene develops in a residual limb. The mortality rate of this condition is high.