Once the patient develops non-reconstructable soft tissue loss or irreparable vascular insufficiency, amputation becomes the patient’s next step toward rehabilitation and recovery. Helping the patient through this transition is both a medical team and family effort for the patient [1]. These two groups play an integral role in both physical and emotional support as well as the medical and psychological well-being of the patient through this entire process. While the foot and ankle surgeon stabilizes infection and plans for functional amputation, the vascular interventionalist will assure adequate blood flow is present and the medical staff will stabilize systemic disease and administer antibiotic therapy, and psychiatry/psychology may provide a role for counseling. Physical therapy is necessary to aid with gait assistance pre- and postoperatively and a physiatrist may be of assistance to aid with mobility as well. Once the patient has closure of the residual limb, a pedorthotist or prosthetist may be invaluable in helping choose appropriate footwear accommodation and protection for the residual foot. Family or caregiver participation in this entire process is critical for the best outcomes. Clearly, the transition through the process of amputation is a team effort that involves medical staff and family working toward the recovery of their shared patient and loved one.

There are many factors involved in selecting the appropriate amputation level. At times the surgeon may choose the biologic amputation level, which is the most distal level the foot can heal. Although this level may sometimes be appropriate, the residual limb may not withstand the activities of daily living. Education of the patient, family, and medical staff regarding functional amputation levels will help ensure that a durable level is chosen at which the patient is best able to perform their activities of daily living [2–4]. Occasionally these choices must be made in the face of a nonambulatory patient, and the team must decide whether local salvage should be chosen or would proximal amputation (such as a through-knee amputation) be more beneficial for the long-term health of the patient. Sepsis and medical instability of the patient may also influence the amputation level decision. When the patient is too unstable for any surgical care, a freezer boot may be applied to the limb. While this provides a physiologic amputation of the limb that may be lifesaving, the process also commits the patient to an above-knee amputation.

Care must be taken to protect the contralateral foot during the process of surgery and recovery. Regular checks of the contralateral limb should be incorporated in the postoperative assessment of the patient. Should the patient wear prescription footwear, this should be worn during any physical therapy, and care should be taken to make sure that the contralateral foot does not rest against the end of the bed or on a wheelchair foot plate for extended periods of time as ulceration or soft tissue injury may occur. The ultimate goal is to maximize quality of life and preserve a functional level of independence. Utilizing this team approach, our patients can often reach a reasonable level of postoperative function.

The most common amputation levels within the foot are digital (distal and proximal), toe and metatarsal, transmetatarsal (TMA), Lisfranc, Chopart, and ankle disarticulation. Each of these amputations may be left open to heal on their own or may be utilized as stepping-stones to a more proximal amputation due to persisting infection or mechanical considerations. The statistics for pedal amputation show that revisions are more frequent when amputations are performed within the foot. This fact is not unexpected. It is quite common for a patient to have an open amputation of a toe, metatarsal, or even a midfoot/hind foot disarticulation to eradicate severe infection or gangrene. Once the patient has recovered from their sepsis and soft tissue infection is controlled, a decision on wound closure or amputation level can be made. Care can be taken to make sure that the patients have control of their infection, adequate tissue nutrition, and an appropriate choice for amputation level leading to the best function.

Osteomyelitis can be a limiting factor in salvage of the forefoot and midfoot. Early resection of metatarsal heads or the local bone that is infected for biopsy and culture in the care process can lead to accurate early decisions on antibiotic therapy. This in turn may improve the rate of cure and more distal salvage of the infected limb by reducing soft tissue destruction from infection. Consideration may be given to taking a “clearance fragment” of the bone at the most proximal level of amputation [5]. This specimen is sent for pathologic and microbiologic assessment to make sure that all of the infection has been resected. Should these fragments not be infection-free, consideration must be given to an extended course of antibiotics, unless further revision amputation removes the remainder of the affected bone. Certainly culture-driven antibiotic therapy with infectious disease consultation, as needed, will lead to the best potential outcome .

Amputation flaps predominately heal by collateral circulation. Due to this phenomenon, arteriography is rarely useful as diagnostic tool to predict amputation healing. Doppler ultrasonography is commonly utilized to determine whether adequate perfusion exists in the extremity prior to performing an amputation. The ischemic index is a ratio of the Doppler pressure at the anatomic level of concern compared to the brachial systolic pressure. An ischemic index of 0.5 or greater at the surgical site is thought to be necessary to support wound healing. An ankle-brachial index (ABI) of 0.45 in the patient with diabetes has been considered adequate for healing as long as the systolic pressure at the ankle was 70 mmHg or higher [6]. These values are falsely elevated, and non-predictive, in at least 15 % of patients with peripheral arterial disease. This is primarily due to the noncompressibility of calcified peripheral arteries [7]. Other forms of noninvasive vascular testing can be considered when ABIs are unreliable. This would include the use of transcutaneous partial pressure of oxygen (TcPO2) [8–10], measurement of skin perfusion pressure (SPP), and the toe brachial index (TBI) [11–14]. The vascular laboratory can measure toe pressures as an indicator of arterial inflow to the foot. The arteries of the hallux are less commonly found to be calcified than the vessels of the leg and at the level of the ankle. The accepted threshold for toe pressure is 50 mmHg. Consultation with a vascular specialist should be obtained for patients who do not have adequate inflow demonstrated on these exams .

Preoperative review of nutritional status is obtained by measuring the serum albumin and the total lymphocyte count (TLC). The serum albumin should be at least 3.0 gm/dL and the total lymphocyte count should be greater than 1500. A serum albumin level of 3.5 g/dL or less indicates malnutrition [15]. Serum prealbumin levels can also be considered when nutritional competence is borderline. Prealbumin levels are thought to be a better measure when determining the effects of nutritional supplementation due to its short half-life. Normal prealbumin levels range from 6 to 35 mg/dL [16]. The TLC is calculated by multiplying the white blood cell count by the percent of lymphocytes in the differential. When these values are suboptimal, consultation with a nutritionist is helpful to assist with optimizing the patient before definitive amputation. Surgery in stabilized patients with malnutrition or immunodeficiency should be delayed until these issues can adequately be addressed. When infection or gangrene dictates urgent surgery, the goal should be to eradicate infection and eliminate necrotic tissue to viable margins. An open amputation at the most distal viable level, followed by open wound care, should be performed until wound healing potential can be optimized [15, 17–19]. Patients with severe renal disease may never achieve desirable nutritional parameters. Distal salvage attempts may still be pursued, but at known higher risk for failure.

Poor glycemic control has been identified as a risk factor associated with a higher frequency of amputation [20, 21]. Hyperglycemia will deactivate macrophages and lymphocytes and may impair wound healing. There is also a higher risk of urinary tract and respiratory infections when glucose levels are uncontrolled. Ideal management involves maintenance of glucose levels below 200 mg/dL [22]. Caution must be taken in managing the perioperative patient’s glucose with calorie reduction. This may lead to significant protein depletion and subsequent wound failure. If the patient’s BMI is normal, 25 cal/kg is required to maintain adequate nutrition and avoid negative nitrogen balance.

The combined wound healing parameters of vascular inflow and nutritional status have been shown to significantly affect healing rates for pedal amputations. Optimizing the patient’s nutritional parameters and achieving adequate perfusion will limit the risk of wound complications and failure .

Many of the patients that require surgical care for amputation have significant cardiovascular disease. Recurrent anesthetic exposures may be detrimental to such patients. All pedal amputations can be performed under local anesthesia with monitored care (MAC) or under a regional block with sedation. Regional blocks can be quite successful with sedation and provide a comfortable option for the patient. Care must be taken to assure that anesthesia is provided at the level of the tourniquet. Tourniquets at the ankle, calf, and thigh may be used, but care must be taken not to place these over areas of cellulitis/abscess or at a level of vascular repair. Elevation of the extremity for three minutes prior to tourniquet inflation is preferred to exsanguination of the infected extremity as compression of the soft tissues from distal to proximal may spread infection. Spinal anesthetics are contraindicated in the septic patient due to the risk of seeding the spinal fluid during the procedure .

Peripheral neuropathy affects many of the diabetics who require peripheral amputation [22]. Significant motor imbalance with overpowering of the posterior leg compartment is not uncommon. Neuropathy can lead to nonfunctional intrinsic muscles within the foot as well as a weakened anterior motor compartment of the lower limb. This imbalance can lead to significant contractures postamputation (Fig. 52.1). The potential for imbalance at each of the amputation levels will be addressed through discussion of these amputation levels .

Occasionally, forefoot infection may be well localized to an immediate infected area of ulceration. Soft tissue infection may be controlled with antibiotic therapy, and there is no ascending cellulitis or lymphangitis. There is minimal soft tissue necrosis in the area. This site may or may not be associated with a significant bony prominence. Additionally, the patient has no systemic signs of infection. Such findings are often present and associated with focal osteomyelitis at a metatarsal head or phalanx. Local resection of that metatarsal head or portion of the phalanx may be performed [23]. The microbiologic specimen and pathologic specimen are taken and sent for assessment. Depending on the resection of the bone, this procedure may be curative or may require a longer course of antibiotics. The wound may be closed or may be packed open and treated much like an ulceration leading to closure of the wound with wound care. This internal amputation of the bone may allow for preservation of the soft tissues and lead to a stable digit over time [24]. Digital surgery, such as this, functions much like hammertoe surgery and may lead to a long-term cure for local infection (Fig. 52.2). Metatarsal head resections function much like a ray amputation. Transfer ulceration to an adjacent metatarsal head is possible. Prevention may be possible with prescription footwear, accommodative insoles, and frequent clinical follow-up. When ulceration persists, pan metatarsal head resection [25, 26] and/or posterior compartment lengthening such as an Achilles lengthening or gastrocnemius recession may be needed .

Sizer and Wheelock [27] described toe amputations and their healing outcomes. They reviewed 692 toe amputations. When pulses were palpable, nearly 98 % healed; but, if pulses were not palpable, the failure rate was 11 %. Attempts to predict toe amputation healing with vascular studies have not been fully successful.

The anatomy of the toe limits amputation to either proximal or distal levels. The wing and sling mechanism allows flexion of the toes at the distal interphalangeal joint (DIPJ) and toe extension occurs through a lifting mechanism at the base of the proximal phalanx. Excision of a portion of the distal phalanx may allow for a stable digit with good motor balance. Resection through the PIPJ in the neuropathic patient may, however, result in extension deformity of the toe. Extension can lead to irritation of the residual toe from footwear with the possibility of new ulceration. The unsalvageable toe is best resected through its base or disarticulation at the metatarsal phalangeal joint (MPJ). Preservation of the MPJ maintains the plantar plate and joint intrinsic muscle capsule attachments and may limit proximal retraction of the plantar fat pad of the forefoot. Whether or not this absolutely reduces the risk of ulceration at the metatarsal heads has yet to be determined. If the toe is disarticulated at the MPJ, and the wound is to be left open for drainage, the cartilage of the metatarsal head is resected to allow granulation over the residual metatarsal [28]. This resection is not absolutely necessary if wound closure is performed. Due to the cartilage avascularity, the authors will typically resect the cartilage .

Incisions for toe amputations create flaps dorsal to plantar or medial to lateral. Plantar flaps have more durable skin and are preferred when healthy tissue is available. Side-to-side flaps are of value if proximal incision is necessary over the foot dorsally or plantarly to allow drainage of infection. Hallux amputation has the most elevated risk of complications with new ulcers developing at adjacent metatarsal heads as well as increased hammertoe formation on the residual foot .

Nail bed and distal tip ulceration from osteomyelitis or gangrene may occasionally be managed with bone biopsy and culture-driven antibiotic therapy [29]. When this is not feasible, amputation is needed (Fig. 52.3).

A toe and metatarsal amputation may be utilized as a definitive amputation procedure or as an incision and drainage for management of infection. Isolated ray amputations have an elevated risk of new ulceration developing at an adjacent metatarsal head [28]. The risk of re-ulceration at an adjacent metatarsal is higher with the first ray than with lateral ray resections [31].