Major Limb Amputations and Prosthetics

Indications

Unlike in the lower extremity, the majority of upper extremity amputations are performed for acute trauma. ^, In fact, in a Scandinavian epidemiologic study, up to 90% of upper extremity amputations were trauma-related. Amputations may be performed acutely when the hand surgeon believes that the functional potential of the salvaged limb would be substantially worse than prosthetic limb rehabilitation. At times, the surgeon will elect to perform multiple operative procedures in an attempt to salvage a hand or extremity but are unsuccessful in these attempts. It is even possible that these attempts to salvage a severely damaged limb can be detrimental to the health of the patient. In these cases, there is often severe and irreparable damage to the neurovascular supply to the extremity or severe injuries to the skeleton, either of which may make meaningful recovery nearly impossible. It is also possible that amputations are performed in a delayed or staged fashion, such as when replantations and other reconstructive efforts ultimately fail.

Major upper extremity amputations may also be required following burns or infections or as treatment for malignancies. Up to 26% of electrocution injuries require some form of major amputation. Deep thermal burns result in amputations approximately 3.8% of the time, usually due to nonviable tissues, but at times for control of a septic source ( Fig. 50.1 ). While most infections can be managed with antibiotics and surgical debridement, invasive fungal infections, like mucormycosis, almost uniformly result in amputation, particularly in the solid-organ transplant patient population. There has been only one case report published of a salvaged upper extremity in an immunocompromised patient with a mucormycosis infection. The mortality in this patient population has been reported as high as 92%. ^, Advances in radiation therapy, chemotherapy, and limb salvage surgical techniques have considerably reduced the need for upper extremity amputation in sarcoma patients over the past 40 years, yet radical amputation remains a mainstay of treatment in recurrent disease and large tumors. ^,

Wrist Disarticulation and Transradial Amputation

After decades of research and clinical experience, controversy remains regarding the ideal level of amputation in patients that require removal of the hand. Wrist disarticulation preserves limb length, thus providing a longer lever arm with which to perform work. More importantly, the longer residual limb preserves the distal radioulnar joint (DRUJ), resulting in better pronation and supination. The metaphyseal flare of the distal radius also provides a contour that aides in suspension of a terminal device ( Fig. 50.2 ). However, these benefits come at a cost. The prominence of the distal radius and ulnar styloids can become pressure points, leading to breakdown of the soft tissues of the residual limb, usually along the incisional scar. Though the additional length in a wrist disarticulation provides a longer lever arm, it leads to a limb-length discrepancy with the uninvolved side when a prosthesis is worn. A myoelectric terminal device may add several centimeters of additional length to the end of a residual limb, making the limb length discrepancy even more prominent. This not only presents an esthetic concern but also makes it more difficult for a patient to reach the anatomic midline, requiring greater shoulder abduction and scapular retraction.

For these reasons, patients with wrist disarticulations are more likely to abandon their prostheses than patients with transradial amputations. ^, Ideally, the patient is afforded the opportunity to have a preoperative consultation with a physiatrist and a prosthetist so that they may make an educated decision between a wrist disarticulation and a transradial amputation. Given the usual indications for transradial amputation, however, this is unfortunately rarely the case. Amputation 8 to 10 cm proximal to the ulnar styloid provides the greatest variety of prosthetic options for functional restoration of the extremity. ^, This preserves an adequate arc of pronation and supination and a reasonable lever arm for flexion at the elbow. However, one form of amputation is not ideal for all patients, making the preoperative consultation critically important in the process. For instance, patients who perform heavy labor frequently prefer a wrist disarticulation due to the increased durability of a body-powered prosthetic, the increased lever arm length, and the preserved DRUJ.

As the transradial amputation becomes more proximal and approaches the elbow, the anticipated pronation and supination may be minimal. In fact, there is minimal pronation and supination once half of the original forearm length is removed. Yet preserving at least 5 cm of ulna is sufficient for successful prosthetic fitting. The addition of an elbow joint to the prosthesis greatly increases the amount of work required to use it and dramatically increases the likelihood of abandonment. As a result, preserving the elbow joint should remain a high priority, even when complex reconstructive efforts such as free flaps are required to maintain this joint.