General Principles of Amputations

Peripheral Vascular Disease

Peripheral vascular disease with or without diabetes, which most frequently occurs in individuals aged 50 to 75 years, is the most common indication for amputation. The treating physician should keep in mind that if vascular disease has progressed to the point of requiring amputation, it is not limited to the involved extremity. Most patients also have concomitant disease processes in the cerebral vasculature, coronary arteries, and kidneys. In addition to obtaining a vascular surgery consultation to evaluate the diseased limb, appropriate consultation is indicated to evaluate these other systems.

Approximately half of amputations for peripheral vascular disease are performed on patients with diabetes. The most significant predictor of amputation in diabetics is peripheral neuropathy, as measured by insensitivity to the Semmes-Weinstein 5.07 monofilament. Other documented risk factors include prior stroke, prior major amputation, decreased transcutaneous oxygen levels, and decreased ankle-brachial blood pressure index. Diabetics must be instructed on the importance of proper foot care and footwear and must examine their feet frequently. Ulcers should be treated aggressively with appropriate pressure relief, orthoses, total-contact casting, wound care, and antibiotics when indicated. Other risk factors, including smoking and poor glucose control, should be minimized.

Before performing an amputation for peripheral vascular disease, a vascular surgery consultation is almost always indicated. Improved techniques currently allow for revascularization of limbs that previously would have been unsalvageable. However, revascularization is not without risk. Although there is no conclusive evidence in the literature that peripheral bypass surgery compromises wound healing of a future transtibial amputation, our experience seems to indicate otherwise.

If amputation becomes necessary, all effort must be expended to optimize surgical conditions. All medical problems should be treated individually. Infection should be controlled as effectively as possible, and nutrition and immune status should be evaluated with simple screening tests. It has been shown that the risk for wound complications is greatly increased in patients whose serum albumin is less than 3.5 g/dL or whose total lymphocyte count is less than 1500 cells/mL. Perioperative mortality rates for amputation in peripheral vascular disease have been reported to be 30%, and 40% of patients die within 2 years. Critical ischemia develops in the remaining lower extremity in 30% of the remaining patients.

Determining the appropriate level of amputation is discussed later in this chapter. The energy required for walking is inversely proportionate to the length of the remaining limb. In an elderly patient with multiple medical problems, energy reserves may not allow for ambulation if the amputation is at a proximal level. If a patient’s cognitive function, balance, strength, and motivation level are sufficient for ambulatory rehabilitation to be a reasonable goal, amputation should be performed at the most distal level that offers a reasonable chance of healing to maximize function. Conversely, a nonambulatory patient with a knee flexion contracture should not undergo a transtibial amputation because a transfemoral amputation or knee disarticulation provides better function and less risk.

Trauma

Trauma is the leading indication for amputations in younger patients. Amputations caused by trauma are more common in men because of vocational and avocational hazards. These patients are often otherwise healthy and productive, and such injuries may have profound effects on their lives. The only absolute indication for primary amputation is an irreparable vascular injury in an ischemic limb. With improvements in prehospital care, acute resuscitation, microvascular techniques, and bone transport techniques, orthopaedic surgeons more often are faced with situations in which a severely traumatized limb can be preserved, although this involves substantial compromises.

Several studies have suggested guidelines to help decide which limbs are salvageable. Most of these studies have concentrated on severe injuries of the lower extremity. Most authors would agree that type III-C open tibial fractures, which include complete disruption of the tibial nerve, or a crush injury with warm ischemia time of more than 6 hours, are an absolute indication for amputation ( Fig. 14.1 ). Relative indications for primary amputation include serious associated injuries, severe ipsilateral foot injuries, and anticipated protracted course to obtain soft-tissue coverage and tibial reconstruction. Although these relative indications are subject to various interpretations, they serve as reasonable guidelines.

Other authors have attempted to remove subjectivity from the decision-making process. To predict which limbs will be salvageable, available scoring systems include the predictive salvage index, the limb injury score, the limb salvage index, the mangled extremity syndrome index, and the mangled extremity severity score. Of these, we have found the mangled extremity severity score to be most useful ( Table 14.1 ). This system, which is easy to apply, grades the injury based on the energy that caused the injury, limb ischemia, shock, and the patient’s age. The system was subjected to retrospective and prospective studies, with a score of 6 or less consistent with a salvageable limb. With a score of 7 or greater, amputation was the eventual result. Although we do not strictly follow these guidelines in all patients, we do calculate and document a mangled extremity severity score in the chart whenever we are considering primary amputation versus a complicated limb salvage.

No scoring system can replace experience and good clinical judgment. Amputation of an injured extremity might be necessary to preserve life. Attempts to salvage a severely injured limb may lead to metabolic overload and secondary organ failure. This is more common in patients with multiple injuries and in the elderly. It has been suggested that an injury severity score of greater than 50 is a contraindication to heroic attempts at limb salvage. Concomitant injuries and comorbid medical conditions must be considered before heading down a long road of multiple operations to save a limb.

After determining that a limb can be saved, the surgeon must decide whether it should be saved, and this decision must be made in concert with the patient. The surgeon must educate the patient regarding the tradeoffs involved with a protracted treatment course of limb salvage versus immediate amputation and prosthetic fitting. On entering the hospital, most patients are concerned only with saving the limb; they must be made to understand that this often comes at a great cost. They may have to face multiple operations to obtain bony union and soft-tissue coverage and multiple operations on other areas to obtain donor tissue. External fixation may be necessary for several years, and complications, including infection, nonunion, or loss of a muscle flap, may occur. Chronic pain and drug addiction also are common problems of limb salvage because patients endure multiple hospital admissions and surgery, isolation from their family and friends, and unemployment. In the end, despite heroic efforts, the limb ultimately could require amputation, or a “successfully” salvaged limb may be chronically painful or functionless.

Patients also need to understand that the advances made in limb salvage surgery have been paralleled by advances made in the amputation surgery and prosthetic design. Early amputation and prosthetic fitting are associated with decreased morbidity, fewer operations, shorter hospital stay, decreased hospital costs, shorter rehabilitation, and earlier return to work. The treatment course and outcome are more predictable. Modern prosthetics often provide better function than many “successfully” salvaged limbs. A young, healthy patient with a transtibial prosthesis is often able to resume all previous activities with few restrictions. In long-term studies, patients who have undergone amputation and prosthetic fitting are more likely to remain working and are far less likely to consider themselves to be “severely disabled” than patients who have endured an extensive limb salvage.

Several comparisons of limb reconstruction and limb amputation have come to differing conclusions, with one large study of 545 patients projecting lifetime health care costs to be three times higher for patients with amputations than for those with reconstruction. A meta-analysis, on the other hand, concluded that length of rehabilitation and total costs are higher for patients who have undergone limb salvage procedures. Reports of functional results have been equally varied, with one study reporting a 64% return-to-work rate after limb salvage compared with 73% after amputation, and another study reporting that long-term functional outcomes were equivalent between limb salvage and primary amputation.

The worst-case scenario occurs when a limb must be amputated after the patient has endured multiple operations of an unsuccessful salvage or after years of pain following a “successful” salvage. After realizing the function that is possible with a prosthesis, many patients ask why the amputation was not performed initially. It is important to present all information from the very beginning so that the patient can make educated decisions regarding which course to follow. The physician cannot understand the importance each patient places on cosmesis, function, or body image without specifically asking these questions. Other important issues include the patient’s ability to handle uncertainty, deal with prolonged immobilization, accept social isolation, and bear the financial burden. Without discussing all these issues, a physician would not be able to help patients make the “correct” decisions. The “correct” decisions are based on the patient as a whole, not solely on the extent of the limb injury.

When an amputation is performed in the setting of acute trauma, the surgeon must follow all the standard principles of wound management. Contaminated tissue must undergo debridement and irrigation followed by open wound management. Although all devitalized tissue must be removed, any questionable areas should be retained to preserve future reconstructive options and reevaluated at a repeat debridement in 24 to 48 hours. This time will not only allow the wound to further declare its course but also allow the patient to comprehend the severity of the problem. Functional stump length should be maintained whenever possible; this may require using nonstandard flaps or free muscle flaps for closure. Traction neurectomy for all named nerves and large cutaneous nerves should be performed proximal to the end of the residual limb to avoid sympathetic neuromas. Vascularized or nonvascularized tissue may be harvested from the amputated part to aid in this endeavor. If adequate length cannot be maintained acutely, the stump may be revised later using tissue expanders and the Ilizarov technique for bone lengthening. Negative pressure wound therapy is a useful adjuvant until the time of revision surgery. Controlled localized negative pressure promotes healing by promoting wound contraction, decreasing extracellular fluid, increasing tissue oxygenation, and stimulating formation of granulation tissue. A multidisciplinary approach involving other subspecialties (e.g., general surgery, vascular surgery) is recommended in the acute setting when patients are unable to be involved in the decision process secondary to their other injuries.

Burns

Thermal or electrical injury to an extremity may necessitate amputation ( Fig. 14.2 ). The full extent of tissue damage may not be apparent at initial presentation, especially with electrical injury. Treatment involves early debridement of devitalized tissue, fasciotomies when indicated, and aggressive wound care, including repeat debridements in the operating room. Compared with early amputation, delayed amputation of an unsalvageable limb has been associated with increased risk of local infection, systemic infection, myoglobin-induced renal failure, and death. In addition, length of hospital stay and cost are greatly increased with delayed amputation. Performing inadequate debridements with the unrealistic hope of saving a limb may put the patient in undue danger. Debridements must be aggressive and must include amputation when necessary.

Frostbite

Frostbite denotes the actual freezing of tissue in the extremities, with or without central hypothermia. Historically, frostbite was most prevalent in wartime; however, anyone exposed to subfreezing temperatures is at risk. This is a common problem for high-altitude climbers, skiers, and hunters. Also at risk are homeless, alcoholic, and schizophrenic individuals.

When heat loss exceeds the body’s ability to maintain homeostasis, blood flow to the extremities is decreased to maintain central body temperature. The problem is exacerbated by exposure to wind or water. Actual tissue injury occurs through two mechanisms: (1) direct tissue injury through the formation of ice crystals in the extracellular fluid and (2) ischemic injury resulting from damage to vascular endothelium, clot formation, and increased sympathetic tone.

The first step in treatment is restoration of core body temperature. Treatment of the affected extremity begins with rapid rewarming in a water bath at 40°C to 44°C. This requires parenteral pain management and sedation. After initial rewarming, if digital blood flow is still not apparent, treatment with tissue plasminogen activator or regional sympathetic blockade may be indicated. Tetanus prophylaxis is mandatory; however, prophylactic systemic antibiotics are controversial. Blebs should be left intact. Closed blebs should be treated with aloe vera. Silver sulfadiazine (Silvadene) should be applied regularly to open blebs. Low doses of aspirin or ibuprofen also should be instituted. Oral antiinflammatory medication and topical aloe vera help stop progressive dermal ischemia mediated by vasoconstricting metabolites of arachidonic acid in frostbite wounds. Physical therapy should be started early to maintain range of motion.

In stark contrast to traumatic, thermal, or electrical injury, amputation for frostbite routinely should be delayed 2 to 6 months. Clear demarcation of viable tissue may take this long. Even after demarcation appears to be complete on the surface, deep tissues still may be recovering. Despite the presence of mummified tissue, infection is rare if local wound management is maintained. Triple-phase technetium bone scan has helped delineate deep tissue viability. Performing surgery prematurely often results in greater tissue loss and increased risk of infection. An exception to this rule is the removal of a circumferentially constricting eschar.

Infection

Amputation may be necessary for acute or chronic infection that is unresponsive to antibiotics and surgical debridement. Open amputation is indicated in this setting and may be performed using one of two methods. A guillotine amputation may be performed with later revision to a more proximal level after the infection is under control. Alternatively, an open amputation may be performed at the definitive level by initially inverting the flaps and packing the wound open with secondary closure at 10 to 14 days.

Partial foot amputation with primary closure has been described for patients with active infection; the wound is closed loosely over a catheter through which an antibiotic irrigant is infused. The constant infusion is continued for 5 days. The wound must be closed loosely enough to allow the fluid to escape into the dressings. The dressings must be changed frequently until the catheter is removed on postoperative day 5. This method may allow for primary wound healing, while avoiding a protracted course of wound healing by secondary intention.

In the acute setting, the most worrisome infections are those produced by gas-forming organisms. Typically associated with battlefield injuries, gas-forming infections also may result from farm injuries, motor vehicle accidents, or civilian gunshot wounds. Any contaminated wound that is closed without appropriate debridement is at high risk for the development of gas gangrene.

Three distinct gas-forming infections must be differentiated ( Table 14.2 ). The first is clostridial myonecrosis, which typically develops within 24 hours of closure of a deep contaminated wound. The patient has an acute onset of pain, swelling, and toxemia, often associated with a mental awareness of impending death. The wound develops a bronze discoloration with a serosanguineous exudate and a musty odor. Gram stain of the exudates shows gram-positive rods occasionally accompanied by other flora. Treatment consists of immediate radical debridement of involved tissue, high doses of intravenous penicillin (clindamycin may be used if the patient is allergic to penicillin), and hyperbaric oxygen. Emergency open amputation one joint above the affected compartments often is needed as a lifesaving measure but may be avoided if treatment is initiated early.

Streptococcal myonecrosis usually develops over 3 to 4 days. The onset is not as rapid, and patients do not appear as sick as patients with clostridial infections. Swelling may be severe, but the pain is typically not as severe as that experienced in clostridial myonecrosis. Abundant seropurulent discharge may be seen with only small amounts of gas formation. Debridement of involved muscle compartments, open wound management, and penicillin treatment usually allow for preservation of the limb.

The third entity that must be distinguished is anaerobic cellulitis or necrotizing fasciitis. Onset usually occurs several days after closure of a contaminated wound. Subcutaneous emphysema may spread rapidly, although pain, swelling, and toxemia usually remain minimal. Gas production may be abundant with a foul smell, but muscle compartments are not involved. Causative organisms include clostridia, anaerobic streptococci, Bacteroides, and gram-negative rods. Treatment includes debridement and broad-spectrum antibiotics. Amputation rarely is indicated.

Indications for amputation of a chronically infected limb must be defined on an individual basis. The systemic effects of a refractory infection may justify amputation. Disability from a nonhealing trophic ulcer, chronic osteomyelitis, or infected nonunion may reach a point at which the patient is better served by an amputation and prosthetic fitting. Rarely, a chronic draining sinus is the site of development of a squamous cell carcinoma, which necessitates amputation.

Tumors

Advances in diagnostic imaging, chemotherapy, radiation therapy, and surgical techniques for reconstruction now make limb salvage a reasonable option for most patients with bone or soft-tissue sarcomas. Four issues must be considered when contemplating limb salvage instead of amputation:

• 1.

  Would survival be affected by the treatment choice?

• 2.

  How do short-term and long-term morbidity compare?

• 3.

  How would the function of a salvaged limb compare with that of a prosthesis?

• 4.

  Are there any psychosocial consequences?

Several studies have discussed the first question with regard to osteosarcoma. With the use of multimodal treatment, including surgery and chemotherapy, long-term survival for osteosarcoma patients has improved from 20% to 70% in most series. For osteosarcoma of the distal femur, the rate of local recurrence after wide resection and limb salvage is 5% to 10%, which is equivalent to the local recurrence rate after a transfemoral amputation for osteosarcoma. Although the rate of local recurrence of a tumor after hip disarticulation is extremely low, no study has shown a survival advantage for this technique. In general, provided that wide surgical margins are obtained, no study has proved a survival advantage of one technique over the other.

Amputation for malignancy may be technically demanding, often requiring nonstandard flaps, bone graft, or prosthetic augmentation to obtain a more functional residual limb ( Fig. 14.3 ). Limb salvage is associated with greater perioperative morbidity, however, compared with amputation. Limb salvage involves a more extensive surgical procedure and is associated with greater risk of infection, wound dehiscence, flap necrosis, blood loss, and deep venous thrombosis. Long-term complications vary depending on the type of reconstruction. These include periprosthetic fractures, prosthetic loosening or dislocation, nonunion of the graft-host junction, allograft fracture, leg-length discrepancy, and late infection. A patient with a salvaged limb is more likely to need multiple subsequent operations for treatment of complications. After initial successful limb salvage surgery, one third of long-term survivors ultimately may require an amputation.

Regarding function, the location of the tumor is the most important factor. Resection of an upper extremity lesion with limb salvage, even with sacrifice of a major nerve, generally provides better function than amputation and subsequent prosthetic fitting. Similarly, resection of a proximal femoral or pelvic lesion with local reconstruction generally provides better function than hip disarticulation or hemipelvectomy. Sarcomas around the ankle and foot are frequently treated with amputation followed by prosthetic fitting. Treatment for sarcomas around the knee must be individualized.

Most patients with osteosarcoma around the knee are treated with one of three surgical procedures, which include either wide resection with prosthetic knee replacement, wide resection with allograft arthrodesis, or a transfemoral amputation. In one study of osteosarcoma patients, patients who had undergone resection and prosthetic knee replacement showed higher self-selected walking velocities and a more efficient gait with regard to oxygen consumption than patients with transfemoral amputations. Individuals with a transfemoral amputation functioned at more than 50% of their maximal aerobic capacity at free walking speeds, requiring anaerobic mechanisms to sustain muscle metabolism, which results in decreased endurance. The problem in many of these patients is compounded by decreased cardiac function from doxorubicin-induced cardiomyopathy.

In a comparison of the long-term function of amputation, arthrodesis, or arthroplasty for the treatment of tumors around the knee, patients with an amputation had difficulty walking on steep, rough, or slippery surfaces but were very active and were the least worried about damaging the affected limb. Patients with an arthrodesis performed the most demanding physical work and recreational activities, but they had difficulty with sitting, especially in the back seat of cars, theaters, or sports arenas. Patients who had arthroplasty generally led more sedentary lives and were more protective of the limb, but they had little difficulty with activities of daily living. These patients also were the least self-conscious about the limb.

No study has shown a significant difference between amputation and limb salvage with regard to psychologic outcome or quality of life in long-term sarcoma survivors. The decision of limb salvage versus amputation involves more than the question of whether the lesion can be resected with wide margins. The patient ultimately must make the final decision based on long-term goals and lifestyle decisions.

Rarely, amputation may be indicated as a palliative measure for a patient with metastatic disease and pain that has been refractory to standard surgical treatment, radiation, chemotherapy, and narcotic pain management. Amputation may be indicated for treatment of a recurrent pathologic fracture in which stabilization is impossible. It also may be indicated if the malignancy has caused massive necrosis, fungation, infection, or vascular compromise ( Fig. 14.4 ). Although cure is not the goal, amputation may dramatically improve the functional status and pain relief for the remaining months in some patients. The surgeon must remember, however, that survival is not always predictable. One such “palliative” hemipelvectomy was performed at this institution on a patient who subsequently lived comfortably for an additional 20 years.