43.1  Commentary

The performance of major lower extremity amputations is an important field of expertise for the vascular surgeon. Unfortunately, the necessity of amputation has come to carry a negative connotation of “failure” of our reconstructive therapies in relationship to the treatment of chronic extremity ischemia. Instead, as physicians and surgeons, the need to perform an amputation when indicated should be viewed as an opportunity to maximize a patient’s potential functional recovery, post-operative quality of life, and independence.1,2

In the 2007 update to the Trans-Atlantic Inter-Society Consensus Document on Management of Peripheral Artery Disease (TASC II), the reported aggregate incidence of major lower extremity amputations from large population or nation-wide data is 120–500 per million people per year, with a ratio near 1:1 between above-knee (AKA) and belowknee (BKA) amputations. Continuing debate occurs as to the impact of increasing numbers of revascularization procedures on amputation rates in patients with chronic limb ischemia (CLI). Recent data from Sweden, Denmark and Finland demonstrate a significant decrease in amputations for CLI with the increased availability and use of both endovascular interventions and surgical revascularization and data from the UK demonstrates a plateau in major amputation that may reflect increasingly successful limb salvage.3 At the timeoftheTASCIIstudy,olderUSstudieshadshownnopositiveimpactofrevascularization procedures on amputation rates. However, more recent studies of Medicare B claims between 1996 and 2006 have shown trends in congruence with the European studies, namely a marked decrease in total lower extremity amputations with increasing numbers of vascular interventions.4

The leading causes of amputation vary widely between countries, influenced heavily by their socioeconomic and political situation. Countries with a recent or ongoing history of conflict may experience trauma as the most common cause of major amputation, whereas vascular and metabolic disease tends to dominate in the sedentary populations of developed countries. As a single disease entity, diabetes mellitus and its attendant complications are the leading cause of non-traumatic lower extremity amputation in the United States.5 [Q1: B] Globally, diabetes mellitus is associated with an estimated 25–90% of all amputations.6 A 2002 analysis of discharged patients from United States hospitals showed that the underlying pathology leading to amputations were dominated by far by vascular diseases including diabetic complications (82.0%), followed by trauma (16.4%), with amputations for neoplasm (0.9%) and congenital causes (0.8%) trailing behind.7

Generally, the indications for lower extremity amputation in the setting of vascular diseaseincludeoverwhelminginfectionofthefootthatthreatenspatientlife,restpaininclaudicants that cannot be controlled, and situations in which extensive necrosis has destroyed the foot. However, the advent of modern vascular surgical reconstruction strategies and improvements in endovascular techniques have markedly reduced the role of primary amputation, defined as the performance of amputation prior to revascularization attempts, in the treatment of peripheral vascular disease. Vascular reconstruction remains the mainstay of chronic limb ischemia therapy; on initial presentation of CLI, 50% of patients are initially treated with a revascularization procedure, 25% with primary amputation, and

25% undergo medical management.3 Currently, the indications for primary amputation in thesettingofvasculardiseasearelimitedtothosesituationswherearterialreconstructionis contraindicated. This includes patients in whom the burden of peripheral vascular disease does not allow for bypass grafting (i.e., “no target for bypass”), those who have gangrene to such an extent that it would not permit the salvage of a useful extremity even if vascular reconstruction is successful, and those who have prohibitive comorbid states such as advanced CHF. [Q2: D] Patients with chronic limb ischemia who are nonambulatory pose a dilemma. Due to their preoperative condition, and often possessing flexion contractures due to their ischemic disease or pain, vascular reconstruction usually produces a limb that is neither stable nor useful; primary amputation may be appropriate for this population.3

Despite the focal role of arterial reconstruction in the treatment of chronic limb ischemia, the surgeon must be sensitive to the possibility of futility in repeated treatment and the need for secondary amputation in achieving the best clinical outcome. The indications for secondary amputation include early graft occlusion with fruitless attempts to attain a patent reconstruction, exhaustion of interventional possibilities in restoring flow, or the event in which the limb continues to deteriorate despite the presence of a patent reconstruction.3,8 Indeed, the most common causes of secondary amputation are unreconstructable vascular disease (60%) and persistent infection of the lower extremity despite aggressive vascular reconstruction.3 In a review of 2,306 lower extremity bypass procedures by the Vascular Study Group of Northern New England, 8% of the cases were found to require secondary amputation within 1 year post-intervention; 17% of these amputations were performed in the setting of a patent graft. While graft occlusion was not found to be a definitive amputation requiring event, 42% of those with early graft occlusion eventually had a major lower extremity amputation. Independent risk factors associated with amputation in this population included nonambulatory status preoperatively, dialysis dependence,diabetesmellitus,atarsaltargetforthebypassgraft,andpreoperativehousing in a nursing home.9

Given the societal, economic, and personal impact of an amputation to a patient, amputees report that they are willing to undergo multiple, repeated, and potentially painful interventions in an attempt at limb salvage rather than undergoing an early amputation.10 The increasing use of endovascular techniques to treat peripheral vascular lesions has shown a potential to avoid amputation for these patients. As cited above, the decade between 1996 and 2006 saw a significant decrease in the rate of amputation. This same period also witnessed a substantial growth in Medicare B claims for endovascular intervention. It is estimatedthat,inconjunctionwithbypasssurgery,thisperiodcoincidedwithadoublinginthe total number of vascular procedures performed.4 Likewise, endovascular specific techniques such as subintimal angioplasty could potentially salvage limbs that would otherwise have undergone primary amputation.11

Appropriate selection of the level of amputation is critical to the formation of an amputation stump that can be well healed and allow for functional rehabilitation. For the vascular surgeon, a badly chosen distal level can lead to the feared complication of a “creeping amputation,” whereas an overly proximal cut would greatly hamper rehabilitation possibilities for the patient. However, no single noninvasive clinical test has been demonstrated to reliably predict primary healing in the ischemic amputee, particularly when dealing with below-knee amputations. [Q3: F] Objective evaluation of skin blood flow at the desired

level of amputation is the best means to anticipate primary healing. Clinical assessment includes a pulse exam, looking for palpable pulses above the level of the proposed amputation, the presence or absence of dependent rubor, venous filling, skin temperature as assessed by the palm of the hand, and signs of infection at the site of incision.12 Segmental Doppler systolic blood pressure measurements have been used for decades, but its use is hampered in distal amputation measurement by the calcification of arteries, and data defining a lower limit of systolic blood pressures at the popliteal artery for successful healing have been inconsistent, ranging from below 50 mmHg to as high as 70 mmHg. Skin injections of radiotracer dyes have been studied since the 1980s, but are highly subject to operator variability in injection level and factors affecting blood flow such as cardiac function, body temperature, and ambient temperature that proved difficult in providing standardization. In the case of fluorescein injection, cardiac arrest has been described following injection. There is little work to support the independent use of skin thermography alone in determining incision level.13

Much literature has been produced to support the use of transcutaneous oxygen pressuremeasurements(TcPO2)indeterminingamputationlevel.Thismethodutilizesaheated Clark electrode to overcome the limitations of skin injection dyes in a test that is both simple and inexpensive to perform. Early experiments found high correlations of TcPO2 with ischemic rest pain, intermittent claudication, and tissue loss compared to normal controls. Like the blood pressure tests, attempts to establish a lower limit threshold to predict primaryhealinghasvariedwidely,fromaTcPO2 25to40mmHg.Nonetheless,thismethod may have the highest potential for reaching significance as an adjunctive test in clinical practice, as higher TcPO2 levels are consistently associated with improved rates of primary healing, and the method can be adapted to be used preoperative, intraoperatively, and postoperatively for continued evaluation.13,14

Given the absence of a “gold standard” method, the surgeon is best served using his or her clinical judgment, with the optional conjunction of tests the surgeon feels comfortable with to augment that judgment.

In a patient with extensive gangrene or active infection, the surgeon must follow basic surgical principles regarding control of a contaminated field. The patient with evidence of tissue loss in conjunction with peripheral vascular insufficiency is particularly vulnerable to infection in ischemic areas, and can have profound difficulty clearing disease in these locations as well. Control of infection and restoration of perfusion when limb salvage is realistic is essential.

The patient described above demonstrates ongoing septic shock; while he was initially hospitalized for pneumonia, the frank purulence from his wound and evidence of deep space infection of his foot suggest that his left lower extremity is the infectious focus. Beginning broad spectrum antibiotics is a prudent initial step in his treatment. However, given his known vascular compromise in his affected foot, it is unreasonable to expect medical management alone would be adequate to treat his infection and sepsis. The wound was previously debrided for necrotic tissue to a clean base; at this stage, the deep space infection of the foot suggests that simple debridement would not be sufficient. While the initial goal for this patient was limb salvage, loss of the Achilles tendon to disease in conjunction with the extensive infection of the foot makes the possibility of a functional foot unlikely despite revascularization. High importance should be placed on avoidance of

wound infection, a complication with disastrous consequences for the patient. The most efficacious surgical intervention in this situation is an ankle disarticulation or guillotine amputation at the level of the malleoli in order to clear diseased tissue, reduce final amputation wound infection, and improve overall outcomes. [Q4: C] This incision should be no higher than a few centimeters proximal to the malleoli despite more proximal cellulitis, without flaps to allow for adequate drainage while treatment is continued with dressing changes and antibiotics. Completion amputation should be delayed until 1 week after the disarticulation to allow for sepsis clearance.8

When planning an amputation level, the surgeon must weigh competing surgical factors favoring wound healing with the desires of the patient and rehabilitation team for a highly conservative amputation. The advantages of a BKA, in comparison to an AKA, are most noticeable when considering the postoperative recovery and rehabilitation of the patient. Though factors such as presurgical fitness, mental status, and age weigh into the potential of a patient to ambulate after amputation, the presence of a preserved knee joint greatly favors positive outcomes. Amputees who have undergone a BKA achieve post-surgical bipedal amputation rates up to 80%, as opposed to 38–50% patient who have had an AKA. Similarly, while all amputees experience increased energy expenditure when compared to a non-amputated control during ambulation, BKA patients only face a 10–40% increase, as opposed to a greater than 60% increase after an AKA.15 These findings are summarized in Table 43.1.

TheprimarydisadvantageofaBKAwhencomparedtoanAKAinthesettingofperipheral vascular disease is the decreased potential for primary healing. It is often quoted in surgical dogma that, with clinical determination of amputation level, a BKA has an 80% rate of uninterrupted primary healing, while an AKA chosen under the same guidelines has a rate of primary healing of at least 90%.16,17 More recent data from the TASC II study confirms an overall rate of 75% of BKA stump healing: a primary healing rate of 60% is foundamongpatientsafteraBKA,withanadditional15%ofpatientsachievingsecondary healing while preserving their BKA residual limb. Additionally, 15% of BKA patients require conversion to AKA in the early postoperative period, while an estimated 10% succumb to perioperative death.3

In light of the post-surgical well-being of the patient, the data clearly supports the preservation of a functional knee joint whenever feasible. However, there are many patients in

Table 43.1  Energy expenditure and ambulation rates as a function of amputation level. Adapted from Tang et al., JACS 2008.

whom essential medical conditions leave an initial AKA as the best clinical option. In patients who have had chronic ischemic damage, the surgeon may find ischemia in areas precluding a BKA, or discover irreversible tissue injury during the open amputation, signified by noncontractile gray muscle or severe knee flexion contracture or rigidity; BKA in these patients may be futile, result in a nonfunctional knee joint that may not heal and wouldrequirefurthersurgery.AnothergroupinwhichAKAmaybemoreclinicallyappropriate include patients who fail to walk or would not be expected to ambulate post-opera- tive due to underlying comorbities; examples of these patients include the elderly afflicted with severe dementia, those debilitated by the sequelae of severe or multiple cerebral vascular accidents, and people who are experiencing end-stage pulmonary or cardiac dysfunction.17,18 Due to their bedridden status, severe knee contracture would inevitably result, predisposing to the formation of pressure ulcers on the residual limb that would necessitate revision to an AKA.17 [Q5: E]

The patient described in the case scenario, though reporting symptoms consistent with claudication,stillpossessesareasonableexpectationofambulationduetohispre­ -hospitalized functional status. A BKA would be an appropriate choice for his completion amputation.

Healing is a particularly complex concern for vascular and diabetic amputees, as the underlying medical comorbidities and the issues of local tissue ischemia that resulted in the pathology necessitating surgery will heavily weigh on the success of recuperation. Wound infection is the most serious complication that frequently requires an above-knee revision of the residual limb; infection greatly reduces rehabilitation potential, increases hospitalization length, and can be life-threatening. Intrinsic infection from tissues used to create the stump are more common than new extrinsic infections in this patient population.8 Antibiotic regimens should be tailored to preoperative cultures and sensitivities from infected wound beds as the clinical timecourse allows. A statistical regression of a small UKpopulationofBKAfailuresyieldedanincreasedoddsratioof14towardAKArevision over noninfected residual limbs; similarly, postoperative limb trauma was shown to contribute significantly to a need for revision or AKA.19 Wound edge necrosis in isolation does not necessarily require an AKA, its presence signifies local ischemia that may hamper adequate wound healing. The presence of necrosis and ulcerations on the stump also predispose to infection and concurrent sepsis.8,19 While a poor-fitting prosthetic or dressing can contribute to pressure ulcer formation on the residual limb, early ambulation and weight-bearing are highly encouraged and associated with increased success rates of postsurgical rehabilitation. [Q6: E]

In carefully selected populations, conversion to an AKA and its consequent distractions from the patient’s quality of life can be avoided by a revision of the BKA. Recent initial studies suggest that these patients generally have failure secondary to a history of minor trauma to the stump while possessing a palpable popliteal pulse, as opposed to a failure due to inadequate tissue perfusion. 86% of these patients were able to ambulate postoperatively, while 0% of their matched AKA controls achieved that goal.20

While the gold standard for dressing of a post-below-the-knee amputation has long been a bulky, rigid dressing, evolving technologies in the field of prosthetics has created an expanding role for the use of immediate postoperative prosthesis (IPOP). Modern use of IPOP is first cited in the early 1960s and 1970s with variable healing rates; Moore cites a primary healing rate of 62–75% with a 100% rehabilitation rate in amputees who were

ambulatory prior to surgery.21 These early designs were non-removable cylindrical casts that had to be cut for wound observation and recreated for additional use thereafter. Currently, IPOP is not the standard of treatment; concerns cited may stem from this legacy, as they include unfamiliarity with the technique, the need for frequent wound monitoring, and fear of placing a hard cast on a vascularly compromised limb. The purpose and results attributedtoIPOPuseincludecontrollingorpreventingkneeflexioncontracture,minimizing postsurgical edema and pain, providing psychological benefit of early ambulation, reducing phantom pain and the effects of inactivity through controlled weight bearing and ambulation, and protecting the residual limb from trauma. [Q7: A, C, D, F] In addition, IPOP use is also associated with assistance (but not acceleration) in wound healing and residual limb maturation. Experience through the last decade with the removable IPOP has demonstrated not only the ability for frequent wound examination for the surgeon, but benefit to the physical therapist in allowing for strengthening and range of motion exercises, and to the prosthetist in allowing for adjustments for residual limb volume loss and assisting in limb shaping.15,22 Bulky rigid or semirigid dressings also possess many of the same advantages in the avoidance of wound complications and preventing the development of flexion contracture at the knee. Advocates of these dressings cite concerns about inhibiting the patient’s movement in bed during the initial hours of recovery.8 However, the unique advantage of the IPOP is the speedy path to rehabilitation and ambulation in the capable patient.

Healing from surgery is only the first hurdle for the amputee; recovery and rehabilitation is the focus of surgical therapy in these patients. In order to maximize the patient’s chances for independent ambulation, adequate surgical recovery with appropriate amputation level selection must be combined with early ambulation. This can be maximized in BKA patients with the use of an IPOP. However, if the surgical team chooses to utilize rigid bulky dressings, rehabilitation for the patient should begin on the first postoperative day by getting the patient out of bed and encouraging weight bearing on the intact contralateral leg; by postoperative day 4 or 5, most patients will be ready for pylon and foot fitting and travel to physical therapy for more intense rehabilitation. Though amputees experiencethedangersofatelectasisandpulmonaryembolismassociatedwithprolongedbedrest common to surgical patients, muscle atrophy in the upper body and remaining lower extremity can profoundly complicate mobility and must be avoided with an aggressive rehabilitative routine.8 Ultimately, the ability to achieve independent survival is directly relatedtopatientsurvival.Inaseriesof2,616VeteransAdministrationpatientswhounderwent major lower extremity amputation, those who achieved even marginal independence had a 6 month survival rate of at least 91%; patients who remained totally dependent on assistance had only a 73.5% 6 month survival rate. Unfortunately, 36% of all patients in this population were never able to recuperate beyond total dependence on assistance. Those that were able to achieve higher levels of independence tended to be younger, have undergone fewer procedures, and carried less comorbidities.23

Despite the most ambitious of rehabilitation protocols, about 80% of BKA patients and less than 50% of AKA patients achieve ambulation (Table 43.1).15 These results drop dramatically when amputation is bilateral; it is uncommon for bilateral amputees to regain ambulationaftersurgery,regardlessoftheirage.Eveninyoung,otherwisehealthypatients, it is rare for bilateral amputees to achieve normal gait. [Q8: E]8