Tourniquets

Although the use of tourniquets in amputation surgery has often been proscribed in the past, the experimental basis for this prohibition is lacking. A controlled, randomized trial of tourniquet use in foot amputations in diabetic and dysvascular nondiabetic patients demonstrated no difference in healing rates between patients with tourniquets and those who did not have tourniquets applied.⁶ In this series, the tourniquet was released once the amputated part was removed, before beginning the closure, to check for hemostasis and flap viability.

Use of tourniquets requires three other considerations: the location, the type of tourniquet, and the presence of underlying vascular bypass grafts. For partial foot amputations, if a tourniquet is desired or needed, an Esmarch bandage just above the malleoli is safe and effective.6,7 For more proximal amputations, a thigh tourniquet is required and thus must be a pneumatic tourniquet. Although easy to use, thigh tourniquets can inhibit quadriceps function postoperatively, which may be a consideration in some patients. Surgeons are reluctant to place a tourniquet over this area in patients with vascular bypass grafts.

In the case of below-knee amputations, it is reasonable and very often helpful to use a thigh tourniquet to improve visualization, especially for ligature of the vascular bundles. The tourniquet is released before wound closure to check for hemostasis.

Soft Tissue Preservation

The most important first step in amputation surgery is aggressive debridement of infected and necrotic bone and soft tissue. This must be balanced by the need to preserve the maximum amount of viable skin and soft tissue, especially plantar flaps, because they make the best soft tissue coverage of weight-bearing surfaces. When the amputation is done for gangrene, the initial and preliminary line of resection should be quite close, usually a few millimeters, from the edge of the gangrene, in order to save the maximum amount of soft tissue. At the time of return to surgery for closure, if the edge proves not to be viable, it can be cut back farther at that time. Surprisingly, the skin is usually viable because the level of nonviability has already been demarcated. Taking a too-generous margin of skin often can force the surgeon to go to the next higher level of amputation.

The surgeon should not hesitate to make irregular or asymmetric flaps and then to reevaluate the pattern of closure once a bleeding edge has been obtained all around the wound. The surgeon must make the best use of the available soft tissue and is encouraged to use “creative” local flaps. The principle is to make use of the areas of viable tissue that might not fit the pattern of a standard flap for the level of amputation. For example, the pattern of locally viable tissue might allow the surgeon to swing a local flap medially to laterally instead of using the typical long plantar flap for closure of a transmetatarsal amputation. The innovative use of local tissue in such a situation often is the only way to achieve closure at that level. Otherwise, the patient has the disadvantage of requiring a more proximal amputation. This type of local flap is also preferable to a skin graft because it is more durable and more sensate. Classically, the ideal length of the flap is approximately half the width of its base. However, the real-life situation of patient care is not always ideal, and some allowance must be made for the vagaries of each case if it affords a potential advantage to the patient.

Residual local flaps often need to be thinned, especially where they form corners. This is true at all levels of amputation. As the excessively thick flap is folded over, it bunches up in the corner and pushes the skin edges away from each other. Thinning the flap excessively can disturb the vascularity of the skin edge; some residual thickness contributes to a natural eversion of the edges.

If doubt exists about the viability of an area, the area can be preserved and observed and then further debrided at the next session in the operating room. Especially with an infected wound, the patient might require two or three sessions in the surgical suite: the first time for initial, aggressive debridement; the second time, if needed, for redebridement of residual areas of infection or necrosis after a period of intervening wound care; and definitive closure at that or a subsequent session. Occasionally, it is necessary to expand the middle step to more than one secondary debridement. After the debridements, the wound is usually left open to allow drainage and wound care. Surgical redebridement at intervals augments wound care until the wound is clean or has good granulation. In many cases, the focus of infection is sufficiently distal or localized that the debridement and closure can be done in a single session (see the discussion of surgical treatment of infection in Chapters 16 and 27).

Wound Closure

The final wound, especially in a partial amputation of the foot, must be fashioned to balance the length of preserved bone with the available soft tissue to cover it. Wound closure, and thus the ultimate length of the foot, is almost always a function of the amount, location, and shape of the remaining viable soft tissue. If there is deep infection of the bone, the overlying soft tissue is usually compromised by infection as well. Once both are resected to a level proximal to the infection, the bone length can be balanced to the soft tissue.

In many cases, it is necessary to sacrifice an additional portion of the osseous structure to achieve this balance. With an infected diabetic foot, this can signify excision of additional uninfected metatarsals to achieve delayed primary closure of a partial forefoot or transmetatarsal amputation. In an example of a partial forefoot amputation, the metatarsal in question would have been partially exposed at surgery. With subsequent skin closure, the surgeon finds it impossible to completely cover the wound with the remaining viable skin and soft tissue, and skin grafting would not result in a stable closure. An example of a transmetatarsal amputation is a patient in whom the medial two or three rays have been partially resected for osteomyelitis, and the remaining lateral rays create an insufficient platform for weight bearing. Resection of the uninfected rays allows a better balanced and more functional foot.

Once a clean, granulating wound is achieved, whether the procedure is a diabetic or a posttraumatic amputation, the wound should be closed. Although primary closure cannot always be achieved, especially in the dysvascular or diabetic patient, the surgeon should strive for primary closure of the amputation site. This can be either immediate primary closure at the time of resection or delayed primary closure at the second or third procedure in the surgical suite. This can be attained in the majority of cases.

Failure to achieve primary or delayed primary closure in a large number of cases signifies poor decision-making. Leaving large gaping wounds to granulate inward as the main method of healing amputations, especially in diabetic patients, condemns the patient to an unnecessarily and very long recovery (Fig. 28-2). This technique often represents the surgeon’s failure to make a decision about the viability of the local tissue and the appropriate final level of healing. It is more effective and far more cost-effective, not to mention less debilitating to the patient, to establish an assessment of the vascularity and healing potential of the partial foot amputation wound and do a definitive procedure with good, viable local closure. If needed, the limb should first be revascularized by the vascular surgeon and then redebrided and eventually closed at the new level of viability.

Allowing an entire amputation wound to granulate slowly is an extremely slow process. Large wounds that are left to granulate very often require skin grafting and produce an irregular scar or an invaginated skin surface. The process of wound contracture can be hindered by the shape of the wound and the amount of residual bone structure beneath. Delayed primary closure is valuable, even if it only achieves partial closure of the wound. It reduces the amount of coverage to be achieved and speeds healing. In such cases, the wound flaps adhere over part of the wound’s length, and a portion fails to close and continues to drain small amounts. This still reduces the morbidity because the residual wound that must be treated and that must granulate inward is still only a fraction of the original wound’s size.³² The validity of this concept has been reaffirmed by the advent of negative-pressure wound dressings.^11,16,33,45

The technique does not work for every case, and it certainly cannot overcome inadequate debridement or inclusion of nonviable soft tissue. However, primary closure, even when partial, is a durable technique for maximizing foot salvage.

A common pattern is adherence and closure of the two ends of the suture line, with a small dehiscence in the middle third. The sutures in the healing areas are usually left in place for a minimum of 4 to 6 weeks, occasionally longer while wound care continues on the central portion of the wound. This is an important consideration because the entire wound in a diabetic or dysvascular patient can take many months to granulate inward. If partial closure is achieved, the time to complete healing is greatly reduced.

There are several possible explanations for a wound that does not appear ready for delayed primary closure. Debridement might have been inadequate, and nonviable tissue remains; the soft tissue flaps might have inadequate vascularity; or the wound might have had insufficient time to begin granulating. Even if it is decided to cover the wound with a split-thickness skin graft, a good granulating base, or well-vascularized tissue (e.g., muscle), is necessary first.

In amputation closures, the skin edges are handled as little as possible. Forceps should be used on the subcutaneous and deeper layers, rather than on the skin edges. Flaps should be tested at closure by gently bringing them together manually. This should demonstrate an ability to close the wound without tension. If such a closure cannot be completed, more of the underlying bone must be resected to reduce the pressure on the flaps. The stump should be palpated through the flaps to make sure that no rough edges, sharp angles, or undesirable bony prominences remain. The balance of soft tissue to bone discussed earlier is most evident at closure because there should be no tension on the skin edges or suture line. The surgeon should inspect the skin for blanching as a sign of an overly tight closure. In diabetic amputations, the sutures should be left in place an extended time, usually at least twice as long as in a nondiabetic patient. In most of these patients, the nylon skin sutures, which are nonreactive, should be left in place a minimum of 4 weeks, and sometimes longer.

It is not necessary to resect the cartilage from the exposed surfaces at the level of the amputation. Preservation of the cartilage, and thus of the underlying subchondral bone, can create a barrier to infection of the residual bone. The clearly defined line of the subchondral bone makes it easier to follow the postoperative radiographs for changes such as erosion of the distal bone.

Drains

Drains are usually used at the time of the delayed primary closure. Some form of suction drain is preferable. The type depends on the surgeon’s judgment, the configuration of the wound, and the characteristics of the wound closure. Penrose drains, which typically exit through the closure and between the sutures, are discouraged. They tend to interfere with early adherence of the wound edges in that location and are less effective than a suction drain in reducing postoperative collection of fluid or hematoma. Ideally, the drain should exit through a small separate stab wound.

Skin Grafting and Flap Coverage

Skin grafting is an acceptable technique for obtaining coverage (as distinguished from closure) of amputation wounds. Split-thickness grafting is somewhat more successful in traumatic amputations than in those done in insensate diabetic feet. Because of the loss of protective sensation, primary closure with local soft tissue flaps is still preferable in diabetic patients. Skin grafts often make the difference between salvage and loss of an amputation stump, but they have a higher rate of recurrent breakdown than local skin coverage.

Free tissue transfer has been a valuable adjunct to limb salvage, especially in traumatic amputations of the foot. The greatest benefit has been in obtaining coverage over wounds of the ankle, heel, and hindfoot. These areas have relatively little subcutaneous tissue, and the skin, especially in the hindfoot, is fixed and immobile, which makes rotation of local flaps difficult. Free tissue transfers are difficult, and they add time, expense, and morbidity to the patient’s recovery. Their use should thus be thoughtfully justified. In general, the technique is not often applicable to the forefoot and midfoot. However, when appropriately indicated for coverage of a soft tissue defect over the hindfoot or heel, a free tissue transfer has the potential to create a great difference in functional outcome. The dramatic effect is credited with converting the patient who has no heel from being a user of a prosthesis (e.g., a Syme ankle disarticulation or below-knee amputee) to being a user of a shoe.

Vascular Reconstruction

With an amputation in a diabetic or dysvascular limb, the skin edges should be checked once the final flaps have been fashioned. If there is not at least a small amount of visible bleeding, the flaps should probably be revised to a more proximal level. Typically, the surgeon checks for the presence of punctate bleeding spots in the flaps, and especially along the skin edges. When the limb is dysvascular, vascular consultation should be obtained. Revascularization of the limb can be done through angioplasty, placement of a proximal stent, endarterectomy, proximal bypass, or distal bypass surgery. Regardless of the technique, revascularization is often the key to salvage of the foot. It is crucial to remember this and to work as a team with vascular surgeons.

Bypass is the most common of these techniques. Balloon angioplasty is applicable primarily to discrete, well-localized (and usually proximal) occlusive lesions, which are relatively uncommon in diabetic patients and more common above the popliteal artery in nondiabetic vascular disease. In the nondiabetic patient, bypass usually takes the form of proximal bypass of a major occlusion at the iliac, femoral, or popliteal levels. In the dysvascular diabetic patient, similar proximal occlusions or stenoses occur and respond well to a vascular bypass. In addition, and very commonly, diffuse occlusions of the arteries distal to the trifurcation of the popliteal artery can occur in the lower part of the leg. Unlike in the nondiabetic patient, these are not discrete blockages but usually consist of atherosclerotic involvement diffusely through the vessel. Bypass done down to the level of the ankle may use in situ or reversed saphenous vein grafts. The emphasis should be on doing the revascularization before fashioning the final amputation flaps. Preferably, the final level of amputation is determined once maximum tissue perfusion has been achieved.⁸

The customary surgical techniques described here are basic guidelines, not absolute requisites, for successful amputations. No matter what the conscientious surgeon does, some amputations will fail and will need to be revised to a higher level. If every amputation heals primarily, the surgeon may be doing some amputations at too-proximal a level and not achieving enough salvaged cases from the feet. Often, several procedures and revisions are needed before the final result is obtained, and the revisions do not prejudice the quality of the ultimate result; rather, they make the attempt at foot salvage worthwhile.23,25,29 Healed amputations that result from revision procedures yield satisfactory results similar to those that heal after a single level of amputation. Once partial amputations of the foot heal, the reported rate of revision is as low as 10%, thus indicating that these function as definitive procedures. The surgeon uses imaging and laboratory data, clinical experience, and surgical judgment to select the level for partial foot amputation.

Determination of Amputation Level

A plethora of tests have been promulgated in the surgical and orthopaedic literature as the “best” method to determine the proper level of amputation. Most are based on statistical review of ultimate healing of the amputated limb and the correlation with predicted healing from the test. These procedures include arterial Doppler pressure measurements, fluorescein angiography, transcutaneous oxygen tension measurements, and xenon clearance.12,37,40,57

The literature is replete with these reports, although all the studies examine levels of healing on the thigh and leg. Most of these studies do not address the question of the proper level of amputation within the foot, that is, the question of the correct level for a partial foot amputation procedure. For this reason, these studies are often difficult or impossible to apply to the decision-making process of foot salvage, which depends greatly on local wound factors of gangrene, infection, and general perfusion of the foot. Differences in vascularity between a transmetatarsal amputation and a Syme ankle disarticulation are at best difficult to determine on the basis of most noninvasive preoperative testing. Even when tests indicate differences, their reliability for differentiating levels of viability within the foot has not been clearly proved or widely accepted. Most of the studies on predictive tests for amputation healing levels have been aimed at assessing the segmental vascularity of the limb, that is, healing below the ankle, at the ankle, below the knee, or above the knee.

None of the procedures has been demonstrated to have a clear hegemony in this battle to forecast healing accurately, at least not in the arena of widespread clinical practice. Each of these procedures has clear advantages, and a few of these characteristics are mentioned here, although this is by no means an exhaustive review of this broad subject.

The most commonly used and widely available test is the arterial Doppler ultrasound. This is most useful as a guideline to general levels of perfusion and is the best initial screening test to determine whether the patient needs a vascular surgery consultation and an arteriogram. The Doppler ultrasound is painless, quick, and inexpensive and does not require extensive instrumentation. As discussed in the section on vascular evaluation in Chapter 27, the pulse-volume recordings (waveforms) are reliable indicators of perfusion, but ratios of ankle pressures to arm pressures can be unreliable, especially in the diabetic patient with noncompliant, calcified vessels that give falsely elevated pressures. For healing of distal amputations, the most reliable measures are toe pressures. A forefoot amputation is likely to heal with a toe pressure of 40 mm Hg or greater. Distal wound healing in the presence of toe pressures between 30 and 40 mm Hg is possible but less predictable.³

Some authors advocate transcutaneous oxygen measurements. These measurements are clearly much more cumbersome to perform than Doppler studies. The readings must be obtained in an environment of controlled temperature because they are temperature dependent, and they are time consuming to perform. On a practical level, an adequate number of readings cannot be done efficiently without multiple simultaneous probes. No equivalent to Doppler toe pressures exists; thus this technique does not offer information about healing of the most distal procedures. Recent studies have questioned the reliability of transcutaneous oxygen measurements.⁴⁷ The real question is to what degree the surgeon finds a correlation of test results with wound edge bleeding at surgery and with the healing rate of amputation wounds in that particular institution.

Other Factors Affecting Healing

Other factors that affect healing include edema in the local tissues, systemic disease, and nutritional factors. Systemic factors include glycemic control in diabetic patients or vasculitis in patients with inflammatory arthritides. As noted in Chapter 27, simple indices of nutritional status can have a predictive value for wound healing after amputation.¹⁴ Of course, the adequacy of nutritional status is important to achieving healing. Published measures of this are the total lymphocyte count, which should be greater than 1500/µL; serum albumin 3.5 g/dL or greater; total protein 6.2 g/dL or higher; and hemoglobin greater than 11 g/dL.

Amputation of the Distal Toe and Nail

The terminal Syme amputation, which has been described for severe posttraumatic nail deformity, onychomycosis, or recurrent infection of the great toenail, can be used for the same problems in a lesser toe as well. The key is to remove sufficient bone to allow closure without tension.

Amputation of the Great Toe Through the Proximal Phalanx Base

Although it is technically easier to amputate the great toe through a metatarsophalangeal (MTP) disarticulation, there are potential advantages to saving the base of the proximal phalanx. The minimum length of the base to save is about 1 cm (Fig. 28-4). This recommendation is both intuitive and scientific. The benefits of preserving the base of the phalanx for the subsequent gait of the patient and the pattern of pressure under the foot have been demonstrated in plantar pressure studies with the pedobarograph. The intuitive basis is that by saving the base of the phalanx, the attachments, and thus the functions, of the plantar fascia and flexor hallucis brevis tendon are preserved, at least partially. The independent plantar flexion mechanism of the first ray is not entirely lost, and some of the weight-bearing function of the first ray may be preserved, possibly reducing the transfer of pressure to the second and third metatarsal heads (Video Clip 3).

Metatarsophalangeal Disarticulation of the Great Toe

In some cases, it is preferable to amputate through the MTP joint. There are several important technical points. It is not necessary to remove the cartilage from the metatarsal head, as noted in the section on wound closure. The most important technical point is that the flaps must be viable (bleeding edges, no residual necrotic tissue) and must be easily closed without tension on the skin edges.

It is surprising how distal the flaps must be to achieve closure without tension. In general, the length of the flaps must be at a minimum, equal to half the length of the proximal phalanx.

Once the proximal phalanx has been resected, and before closure, the sesamoid complex should be inspected. As with most distal foot amputations, the extensor and flexor tendons are resected proximal to the level of closure. The flexor hallucis longus passes between the sesamoids in a tight sheath. In many cases of disarticulation of the hallux, the sesamoids retract. However, if they do not, or if the sesamoids are enlarged and arthritic, they can create plantar pressure under the first metatarsal postoperatively, constituting a risk for ulceration in the neuropathic patient. The conjoined tendons of the sesamoid complex are relatively avascular, and the thickness can impede mobility of the plantar flap during closure.

For these reasons, sesamoidectomy is often a necessary component of MTP disarticulation. This can take the form of excision of the medial sesamoid only or of the entire complex of both sesamoids with the cradle of conjoined tendons. It is not typically necessary to resect the plantar crista of the first metatarsal head.

Postoperative Care

Routine dressing changes are continued until adequate healing has occurred. In concept, it would seem preferable not to allow weight-bearing postoperatively in order to protect the wound and the suture line from shearing forces that would pull the wound apart. In reality, many patients are not physically able to sustain non–weight bearing for the reasons elaborated in Chapter 27. A compromise is to allow weight bearing on the hindfoot only, but this is more difficult to achieve than it appears. The use of partial shoes that allow the forefoot to hang over the distal edge of the shoe increases the pressure on the heel and hindfoot.

Sutures are removed 4 to 8 weeks after surgery. Early suture removal should be avoided because wound dehiscence may occur.

Once a great toe has been amputated, a custom-molded filler in the shoe helps to compensate for and diminish sliding of the foot inside the shoe (Fig. 28-6).¹⁵

Figure 28-6 Molded insole for healed partial forefoot amputations.

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