Lower Extremity Amputation

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Chapter 117

Lower Extremity Amputation

General Considerations

Christian Bianchi, Ahmed M. Abou-Zamzam Jr.,

Based on a chapter in the seventh edition by Wayne W. Zhang and Ahmed M. Abou-Zamzam, Jr.

Major lower extremity amputations continue to be part of all vascular practices, despite the general approach of aggressively attempting to salvage limbs. Though often viewed as a failure of treatment, major amputation should be considered reconstructive, when possible, and a definitive treatment option. The convergence of several important factors, including the increased life expectancy of the population and the epidemics of diabetes and peripheral arterial disease (PAD), suggests that amputations will remain an important issue facing patients and surgeons.

The goal of amputation is to remove all infected, gangrenous, and ischemic tissue and provide the patient with the longest functional limb. Avoidance of repeated amputations and provision of uncomplicated healing of operative sites are crucial for the patient’s optimal recovery and best functional rehabilitation or palliation.

Epidemiology

In the United States, approximately 60,000 major amputations (above the ankle) are performed annually.13 In 2003, 115,749 amputations of all types were performed in the United States, which included 55,574 major amputations.1 Diabetes and PAD remain the major risk factors for lower extremity amputation worldwide.4 Studies show that 25% to 90% of all amputations are associated with diabetes.2,4 Patients with diabetes have a 10-fold greater risk of amputation than those without diabetes.3 This association is multifactorial and relates to the presence of neuropathy and infection, as well as the markedly increased prevalence of PAD in this patient population.

Despite the increase in the prevalence of diabetes, current published data support an overall decrease in major amputations.58 A review of all Medicare claims from the Centers for Medicare and Medicaid Services between 1996 and 2006 showed a 29% decline.5 Results were not different if above-knee amputations were studied distinctly from below-knee amputations because both decreased in similar magnitude. A report from the National Hospital Discharge Survey and National Health Interview Survey on diabetes prevalence showed the age-adjusted nontraumatic lower extremity major amputation discharge rate per 1000 persons decreased from 11.2 in 1996 to 3.9 in 2008, while rates among persons without diabetes were unchanged.6 These trends were validated in a Scottish national cohort study from 2004 to 2008, where major amputation rates decreased by 40.7% from 1.87 per 1000 in 2004 to 1.11 per 1000 in 2008.8

Variation in Amputation Rates

There is significant regional variation in the performance of amputation around the world, which suggests that factors other than strictly medical issues may affect amputation rates.410 A study from the United Kingdom cited significant regional variation in amputation rates and stressed the need for consensus guidelines.9 The Global Lower Extremity Amputation Study Group reported that the highest amputation rate (for a first major amputation) was 44 per 100,000 population per year among Navajo men, and the lowest rate was 2.8 per 100,000 per year in Madrid, Spain.4 These disparities likely result from the influence of socioeconomic issues, the access to care, and the functionalities of health care systems. Physician experience also plays a key role in the selection of amputation as a treatment. In the treatment of critical limb ischemia, surgeon caseload and hospital volume have been shown to affect amputation rates, with low volumes being associated with higher amputation rates.11

A study of a Medicare claims database demonstrated that the number of vascular specialists influences the rate of amputation. A 0.30-fold increase in the number of vascular surgeons per 10,000 Medicare beneficiaries led to a 1.6% reduction in amputations.12 The distribution of vascular surgeons and interventional radiologists in the United States is strongly correlated not only with regional medical needs but also with local climate, education, crime, and transportation. This observation suggests that policies to increase the supply of vascular specialists in underserved areas may reduce regional disparities in amputation rates.12 Patient and health care provider education has also been demonstrated to reduce amputation rates.13 Prompt identification of patients at risk leads to more timely referral, treatment, and intervention.

Effect of Ethnicity and Economic and Social Status

The interaction between race or ethnicity and amputation rates is complex. In certain groups, such as the Native American Navajo population, amputation rates appear to be related to the high incidence of diabetes.4 However, blacks are more likely than whites to undergo amputation as opposed to revascularization, even when controlling for the presence of diabetes.1416 These differences have been attributed to variations in access to health care, treatment of co-morbidities, and possible physician and patient factors. Insurance status also has an effect on amputation rates. Patients without insurance coverage have higher rates of amputation than those with access to health insurance.16 Data from the National Inpatient Sample documented that 34% of the 691,833 patients presenting with lower extremity ischemia from 1998 to 2002 underwent amputation. The primary amputation rates were significantly higher among people of color and patients with low income and lack of commercial insurance.17 Similar results showed that black patients were 1.7 times more likely to have both primary and repeat amputations than were white or other patients.18

Effect of Revascularization Rates

Trends in the interplay between revascularization and amputation rates are complicated. During a 10-year period, the Mayo Clinic reported a 50% reduction in amputation rates that corresponded to increased rates of lower extremity revascularization by both surgical and endovascular techniques.19 A Finnish study also demonstrated that an increase in revascularization rates correlated with a decrease in major amputation rates in elderly patients.20 A U.S. study of two national (Nationwide Inpatient Sample and National Hospital Discharge Survey) and four state databases demonstrated that both the number of lower extremity revascularizations and the number of major amputations have declined; this has been accompanied by a substantial increase in lower extremity endovascular interventions. From 1998 to 2003, the volume of major amputations decreased 16% regionally1 (New York, California, New Jersey, and Florida) and 25% nationally.5 However, the number of minor amputations increased 4% regionally and 3% nationally. It has been speculated that the improved limb salvage rates are partially explained by the increase in total revascularization procedures (propelled by endovascular interventions attributable to the perceived decrease in morbidity). Earlier endovascular interventions, in less critical lesions, and expanding endovascular procedures in the patient at high risk for open bypass may contribute to the decreased rates of major amputations. Also, failed endovascular procedures may not directly translate into amputations. Other possible factors contributing to lower rates of amputation include the greater awareness of PAD, the presence of clear guidelines for medical management of atherosclerosis, the implementation of risk factor modification, and the availability of improved methods of wound care.

High-risk patients treated with endovascular intervention have superior rates of limb salvage and maintenance of ambulation compared with patients undergoing primary amputation. However, these patients have no better functional benefit than those treated with primary amputation after 1 year.21 The medium-term results of the Bypass versus Angioplasty in Severe Ischemia of the Leg (BASIL) trial indicate that the outcomes of bypass surgery–first and balloon angioplasty–first strategies are similar in terms of amputation-free survival.22

The ideal balance of endovascular and open surgical reconstructions has yet to be determined for lower extremity ischemia. Nationwide Inpatient Sample data suggest that lower extremity revascularizations have reached a plateau of around 140,000; similarly, major amputation may have settled near 60,000 annually.1 The total number of revascularizations may be higher because same-day endovascular procedures might not be included in the Nationwide Inpatient Sample database. The Trans-Atlantic Inter-Society Consensus (TASC) II Working Group documented that the incidence of major amputations varies from 12 to 50 per 100,000 population per year.23 With the aging of the population, future trends in these areas will have a great effect on health care expenditures.

Indications for Amputation

Indications for amputation have traditionally been divided into acute ischemia, chronic ischemia, foot infection, severe traumatic injury, and lower extremity skeletal or soft tissue malignancies. Trauma and malignancy are beyond the scope of this chapter and are not discussed. In the presence of acute ischemia, major amputation is undertaken for irreversible ischemia, for severe ischemia with no revascularization options, or following unsuccessful attempts at revascularization. Amputation for chronic ischemia may be performed owing to failure of revascularization, lack of suitable conduit or target arteries, severe patient co-morbidities, poor functional status, or extensive gangrene or infection such that foot salvage is not possible. Pedal sepsis without ischemia constitutes another major subgroup of patients undergoing amputation; this presentation is extremely common in patients with diabetes and associated neuropathy. Because the underlying indications for amputation frequently overlap, it can be difficult to compare indications for and outcomes of amputations reported in the literature.

Impact of Diabetes

The presence of PAD and diabetes, either alone or in combination, contributes to the majority of major nontraumatic lower extremity amputations. Many general classifications, however, overemphasize the role of diabetes and understate the role of concomitant ischemia. Malone reported the indications for amputation as follows: complications of diabetes (60% to 80%), infection without diabetes (15% to 25%), ischemia without infection (5% to 10%), chronic osteomyelitis (3% to 5%), trauma (2% to 5%), and miscellaneous (5% to 10%).24 These general classifications have a certain degree of overlap and mask the true interaction between ischemia and diabetes. This simplistic breakdown does not provide clear insight into the true influence of ischemia or the full potential of revascularization to reduce amputation rates. Also, ischemia may occur in an acute or chronic setting, and because no revascularization is entirely successful, amputation may ultimately follow revascularization.

Impact of Tissue Loss and Anatomy

To understand the continued high number of amputations performed despite aggressive revascularization programs, attempts have been made to more clearly categorize the indications for major amputation.25 When identifying the indications for amputation, it must be recognized that with chronic ischemia, limb loss may ultimately occur despite revascularization. Also, patients may present initially with acutely ischemic limbs that are beyond any hope of salvage. The influence of gangrene and pedal sepsis must also be considered because they have a significant impact on the options for limb salvage. Lastly, patient co-morbidities and ambulatory or functional status influence the decision for amputation.

The TASC II Working Group reported that the rate of primary amputation in chronic critical leg ischemia is approximately 25%. Unreconstructable vascular disease is the most common indication for secondary amputations, which account for nearly 60% of patients.23 To more clearly delineate the reasons for major amputation in an academic vascular practice, a series of 131 consecutive major lower extremity amputations were reviewed, and the indications for amputation clearly classified (Table 117-1). In this setting, more than 50% of patients who underwent amputation had prior attempts at limb salvage via revascularization or had no anatomically feasible revascularization options. This group of patients had exhausted the armamentarium of vascular surgery. Seventeen percent of patients were not considered candidates for aggressive attempts at limb salvage owing to a preexisting nonambulatory status (8%) or the presence of excessive surgical risk (9%). Additionally, 32% of patients had nonsalvageable limbs at presentation attributable to extensive pedal gangrene, pedal sepsis, or a nonviable foot that mandated primary amputation.

Similar findings were reported by Nehler and colleagues in a series of 172 major amputations.26 The indications for amputation were critical ischemia in 87% of the patients and complications of diabetic neuropathy without significant ischemia in 13% of the patients. Forty-six patients (30%) had prior bypass failures or amputations despite patent reconstructions, and 10 (6%) had no revascularization options; therefore, 36% had exhausted the resources of revascularization. Eighty-five patients (55%) underwent primary amputation because of severe co-morbidities, poor functional status, extensive necrosis, or a combination of these factors. In another series of 125 major amputations, 38% of procedures were performed following failed revascularizations.27

Impact of Delay in Presentation

The significant role of delay in patient presentation cannot be overstated. The mean time to vascular surgery consultation was 73 days for pedal tissue loss and 27 days for ischemic rest pain in the report by Nehler and colleagues.26 Such delays likely account for the large percentage of primary amputations in their series and underscore the need for patient and physician education. Indeed, in a report by Bailey and coworkers, only 24% of patients with critical limb ischemia were perceived as needing “urgent” vascular consultation, with a mean 8-week duration of symptoms before vascular evaluation.28 Such studies suggest that delayed patient presentation involves not only patient factors but also access issues and physician factors.

Primary Amputation Versus Revascularization

The most important decision in treating critical limb ischemia is the initial determination of whether to attempt limb salvage or proceed with primary major amputation. Despite widespread discussion of great triumphs in revascularization, there is a growing awareness that primary amputation may be the best approach in specific patient subsets. As stated earlier, more than 140,000 lower extremity revascularizations are performed annually in the United States. In recent years, open revascularizations have been partially replaced by endovascular procedures, yet nearly 60,000 major amputations are still being performed each year.1 This implies that the ratio of amputation to revascularization may be close to 1 : 2 nationally. Many specialty centers may have a much lower ratio owing to the filtering effect of referring physicians. Many patients perceived as not being candidates for revascularization are treated locally with amputation and are never referred to these high-volume centers specializing in revascularization.

The ratio of major primary amputation to revascularization differs among facilities and may vary because of surgeon experience and practice protocols. One prospective study demonstrated that 43% of the 224 patients presenting with limb-threatening ischemia were treated by primary amputation, and 57% were treated with revascularization.29 Diabetes mellitus, end-stage renal disease, tissue loss, and poor functional status were all predictors of treatment with amputation as opposed to revascularization.

Groups Benefiting from Primary Amputation

A very reasoned approach to patients presenting with critical limb ischemia is necessary. A thoughtful strategy considering the patient’s co-morbidities, the status of the foot, and the complexity of the required revascularization has been outlined by Nehler and colleagues.30 In a good-risk patient with minimal pedal tissue loss, an aggressive attempt at revascularization should be undertaken with appropriate endovascular or open bypass techniques including the consideration of alternative vein conduits. However, when the patient’s overall health status is poor or the foot lesions are extensive, primary amputation must be considered. Aggressive use of revascularization, particularly endovascular interventions, has resulted in limb salvage attempts in higher risk patients that may have helped to decrease the number of overall major amputations.31 Despite this, secondary amputations are not an uncommon occurrence. In a study that included 358 consecutive patients (412 limbs) with limb loss despite patent endovascular interventions, functional outcomes were compared with the rest of the endovascular-treated group and with those who underwent amputations with patent bypasses (APB). Amputations occurring despite a patent revascularized segment constituted 38% of limb loss in open surgical patients and 80% in endovascular-treated patients (P = .001). Most amputations in the endovascular group were performed within 3 months of the endovascular procedure and the indications were extensive tissue loss or limb dysfunction after radical débridement of infection or gangrene (37%), presentation of recurrent infection (42%), and failure to reverse ischemia (21%).32

The perceived improved outcomes following revascularization compared with amputation have driven the belief that revascularization is always the better option. However, an examination of the data demonstrates that functional outcomes following amputation may not be markedly different from those following revascularization for specific patient subgroups. Taylor and associates analyzed 553 patients who underwent 627 primary major limb amputations.33 In patients younger than 60 years, functional outcomes following below-knee amputation were similar to those of patients undergoing successful revascularization. Such information lends credence to the observation that primary amputation should be considered not a failure of therapy but a viable, important treatment option.26,30,33

Advances in percutaneous revascularization have raised the question of how best to treat the patient considered “unfit” for open revascularization. Taylor and coworkers reported an analysis of 314 patients treated for critical limb ischemia who were unsuitable for open revascularization because of medical, functional, or mental co-morbidities.21 Patients were treated with either percutaneous transluminal angioplasty (PTA) or major amputation. The 131 patients treated with PTA had higher rates of maintenance of ambulation and independent living compared with the 183 patients treated with amputation. However, the PTA group had a higher mortality, and the advantages in ambulation and independent living lasted only 12 months and 3 months, respectively. In the “unfit” patient, endovascular treatment may be no better than primary amputation.

Indeed, in those with extensive foot lesions, severe co-morbidities, or very unfavorable anatomy, primary amputation is often the best treatment option.26,30,33 Because of delayed referral, many patients ultimately undergoing amputation present to the vascular surgeon with extensive pedal necrosis, which makes limb salvage unlikely, regardless of the availability of suitable arterial targets for revascularization. End-stage renal disease presents a particularly difficult challenge, and the presence of advanced heel gangrene in this group of patients may best be treated with primary amputation.34,35

Perioperative Evaluation

Although surgeons have traditionally focused on the preoperative evaluation and near-term (usually 30-day) results of amputations, a more lengthy view of the perioperative period can be helpful. For the patient, the overall experience is important and clearly lasts longer than the 30-day postoperative period. A more global view of the patient during the first year may help identify key issues at different points in the patient’s treatment and recovery. A team approach to patient care is useful during all stages of the perioperative period since the results in any series of amputations are directly related to the skill and enthusiasm of the people involved in the program.36 Members of the team include the patient, family, surgeon, podiatrist, physiatrist, therapist, rehabilitation medicine specialist, prosthetist, nurse, social worker, psychologist, peer support group, and case manager. The common goal should be maximal recovery and rehabilitation after limb loss. The team should be flexible since different team members share the leadership and service responsibilities throughout the 12- to 18-month time frame that typically defines the perioperative period.

Perioperative Stages

The postoperative year-long continuum does not separate easily into “stages.” However, for practical purposes, five stages in the treatment of the amputation patient have been described.37

Stage 2.

Once the surgery is completed, the acute hospital postoperative stage begins and is the time the patient spends in the hospital after the amputation. This stage typically ranges from 3 to 10 days. During this time, transition of care to the appropriate rehabilitation experts is appropriate. The surgeon is still involved because treatment for local and systemic complications is important.

Stage 3.

The immediate postacute hospital stage begins with hospital discharge and extends 4 to 8 weeks after surgery. This is the time of recovery from surgery, a time of wound healing, and a time of early rehabilitation. During this phase the surgeon is less involved but uncomplicated wound healing is essential to early rehabilitation.

Stage 4.

The intermediate recovery period is the time of transition from a postoperative strategy to the first formal prosthetic device. It is during this stage that the most rapid changes in limb volume occur, attributable to the beginning of ambulation and prosthetic use. This stage begins with the completed healing of the wound and usually extends 4 to 6 months from the healing date.

Stage 5.

The transition to stable stage is defined as a period of relative limb stabilization although the limb will continue to change to some degree for a period of 12 to 18 months after initial healing. The newer prosthesis will still require occasional adjustments, and visits to the prosthetist will remain relatively frequent until after the first year of prosthetic use. In this stage the patient should move toward social reintegration and higher functional training. The patient should become more empowered and independent from his or her health care practitioner during this period.

Reducing Perioperative Risk

The overall mortality for major amputations is about 8%. Most reports find that mortality is doubled for AKA as compared to BKA patients.38 A recent study of 2911 patients enrolled in the ACS National Surgical Quality Improvement Program (NSQIP) demonstrated a 30-day mortality of 7% for BKAs. Multivariate analysis identified renal insufficiency, cardiac issues, preoperative sepsis, chronic obstructive pul­monary disease (COPD), steroid use, and increased patient age as predictors of mortality.39 The same study identified preoperative sepsis, regular alcohol use, steroid use, cardiac issues, renal disease, and contaminated/infected wounds to be independent predictors of developing postoperative complications. The overall perioperative complication rate was 34%. Local stump complications occurred in nearly 10% of patients. Of note, the incidence of cardiopulmonary, venous thromboembolic, and cerebrovascular events ranged from 0.5% to 2.1%. The low observed incidence is probably due to the current widespread use of beta blockers, statin therapy, and antithrombotic medications in the vascular patient.40,41 A similar study involving 8696 veterans showed that AKA patients were older (69.0 vs. 66.5 years) and suffered a higher mortality (16.5% vs. 9.7%) when compared to BKA patients although both groups had a similar rate of postoperative complications.6 This study found that increased age, increased patient complexity, and admission with acute thromboembolism were predictive of death.6

Perioperative treatment with beta blockade has been beneficial in the general vascular surgery population, but these important studies included few patients undergoing major amputation.4042 With regards to the need for preoperative cardiac evaluation, guidelines issued in 2007 by the American College of Cardiology and the American Heart Association clarified that its purpose is not to give medical “clearance” but rather to evaluate the patient’s current medical status and cardiac risks over the entire perioperative period.42

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