Amputations of the Lower Extremity

Lower limb amputations are the most common of all amputations. Despite advances in revascularization techniques, the most common indication for lower extremity amputation remains a dysvascular limb, including that caused by diabetes mellitus and peripheral vascular disease. Peripheral vascular disease from all causes affects over 8 million Americans. The rate of lower extremity amputation in this population is around 4 per 1000. Amputation of the contralateral limb is necessary within 5 years in 30% to 50% of patients who have an amputation of a dysvascular lower limb. Twenty percent of below-knee amputations are converted to above-knee amputations. Over 50% of nontraumatic amputations occur from diabetes-related pathology. In the diabetic population, first-year mortality rates after amputation are reported to be as high as 40%, while overall mortality rates range from 60% to 70%.

The number of amputations for causes other than diabetes and vascular disease, such as tumors and infection, has decreased in the United States because of surgical and medical advances. In war-torn countries, improvised explosive devices and land mines continue to be frequent causes of traumatic amputations. Also, a high rate of combat-related lower extremity amputations remains in the military population. Current level I and II studies are underway to investigate optimal lower extremity amputation techniques in this highly active population.

We advocate a multidisciplinary approach to the medical management of lower extremity amputations. Diabetic patients and those with vascular insufficiency who have had lower extremity amputation demonstrate high rates of 30-day mortality, stump complications, and hospital readmissions. Associated coronary artery disease and end-stage renal disease are predictors for perioperative medical complications and hospital readmissions.

The level of amputation is always a difficult decision and has a major effect on a patient’s quality of life. Morbidity is more frequent after transfemoral amputations than after transtibial amputations. Energy expenditure is an important consideration in choosing the level of amputation. The increased energy consumption of bipedal locomotion for transtibial amputees ranges from 40% to 50%, compared with 90% to 100% in transfemoral amputees. Patients with transfemoral amputations are less likely to use a prosthesis successfully and consistently than are patients with more distal amputations. Higher-level amputations, even in children, are associated with a decline in physical function and quality of life.

Younger patients with traumatic amputations or amputations required for tumor treatment are more successful with prosthetic use than are patients with amputations of dysvascular limbs; dialysis patients are even less successful with prostheses. In dysvascular limbs, the level of amputation is critical because of poor wound healing. The most distal level should be chosen where the wound will have the best chance of healing. This decision process can be augmented using clinical tools such as transcutaneous oxygen tension, determining the nutritional status of patients (albumin level of >3 g/dL, lymphocyte count of >1500/mL) and preoperative medical frailty.

Amputation should not be viewed as a failed limb salvage or reconstruction. The amputation must be viewed as an opportunity to reestablish or enhance a patient’s functional level and facilitate a return to near-normal locomotion. Transtibial amputation after failed attempted limb preservation can still be successful in improving pain, decreasing narcotic use, and improving function. This is especially true in the young, highly active trauma population. Meticulous surgical attention is necessary to provide an optimal base of support because the residual limb functions as a “sensorimotor end organ” with tolerance requirements at the stump-prosthesis interface to meet the dynamic weight-bearing challenges of ambulation. Anesthesia pain specialty teams often are helpful in the management of postoperative pain.

Developments in the prosthetic field range from early-stage fitting techniques (computer-assisted stump contour scanning) to the use of advanced prosthetic components (lighter materials, silicone gel liners, computer-assisted knee units, suspension device alternatives, and ankle-foot accommodative and energy storage systems). Osseointegrated prosthetic components have been investigated over the past several decades in transfemoral and transtibial amputees. Potential advantages include improved quality of life and body image, increased proximal joint range of motion, greater prosthetic comfort, better osseoperception, and improved walking ability. Minor complications include frequent superficial infections and stump irritation, and rare major complications include deep infection, osteomyelitis, peri-implant fracture, and failure of osseointegration. Tillander et al. reported a 20% cumulative risk of developing osteomyelitis.

Foot and Ankle Amputations

Amputations around the foot and ankle are discussed in Chapter 15 .

Transtibial (Below-Knee) Amputations

Transtibial amputation is the most common lower extremity amputation. The importance of preserving the patient’s own knee joint in the successful rehabilitation of a patient with a lower extremity amputation cannot be overemphasized. Transtibial amputations can be divided into three levels ( Fig. 16.1 ). The appropriate level must be determined for each individual patient. Although many variations in technique exist, all procedures may be divided into those for nonischemic limbs and those for ischemic limbs. General techniques vary primarily in the construction of skin flaps, muscle stabilization, and osseous stabilization techniques. In nonischemic limbs, skin flaps of various design and muscle stabilization techniques, such as tension myodesis and myoplasty, frequently are used. These techniques are employed to prepare a stump more suited for weight bearing and to protect from wound breakdown. In tension myodesis, transected muscle groups are sutured to bone under physiologic tension; in myoplasty, muscle is sutured to soft tissue, such as opposing muscle groups or fascia. In most instances, myoplastic closures are performed, but some authors have advocated the use of the firmer stabilization provided by myodesis in young, active individuals. In addition, some surgeons advocate creating a bone bridge between the distal tibia and fibula (Technique 16.2). Advocates of the Ertl technique claim that a bone bridge creates a more stable end-bearing construct and decreases the incidence of proximal tibiofibular joint instability. In addition, closure of the intramedullary canal in osteomyoplastic transtibial amputation has been shown to increase blood flow to the residual limb. In ischemic limbs, tension myodesis is relatively contraindicated because it may compromise further an already marginal blood supply. Also, a long posterior myocutaneous flap and a short or even absent anterior flap are recommended for ischemic limbs because anteriorly the blood supply is less abundant than elsewhere in the leg.

FIGURE 16.1, Levels of transtibial amputations.

In combat injuries that result from blasts or fragmentation wounds, the use of standard flaps may be impossible. Often flaps have to be fashioned from viable remaining tissue. Skin grafts may be used to cover soft-tissue defects, but skin grafts are not ideal for a stump-prosthesis interface.

Nonischemic Limbs

Rehabilitation after transtibial amputations in nonischemic limbs generally is quite successful, partly because of a younger, healthier population with fewer comorbidities. The optimal level of amputation in this population traditionally has been chosen to provide a stump length that allows a controlling lever arm for the prosthesis with sufficient “circulation” for healing and soft tissue for protective end weight bearing. The amputation level also is governed by the cause (e.g., clean end margins for tumor, level of trauma, and congenital abnormalities). A longer residual limb would have a more normal gait appearance, but stumps extending to the distal third of the leg have been considered suboptimal because there is less soft tissue available for weight bearing and less room to accommodate some energy storage systems. The distal third of the leg also has been considered relatively avascular and slower to heal than more proximal levels. Contemporary liners and ankle-foot storage systems now allow more options for accommodating a longer residual limb, but the long-term risk of skin breakdown in older patients with these newer prosthetic components is unknown. Our recent war experiences have shown that early posttraumatic amputations decrease the risk of chronic residual limb infection. If only one posttraumatic debridement procedure and 5 days or fewer pass before definitive amputation, the risk of infection is limited.

In adults, the ideal bone length for a below-knee amputation stump is 12.5 to 17.5 cm, depending on body height. A reasonably satisfactory rule of thumb for selecting the level of bone section is to allow 2.5 cm of bone length for each 30 cm of body height. Usually the most satisfactory level is about 15 cm distal to the medial tibial articular surface. A stump less than 12.5 cm long is less efficient. Stumps lacking quadriceps function are not useful. In a short stump of 8.8 cm or less, it has been recommended that the entire fibula together with some of the muscle bulk be removed so that the stump may fit more easily into the prosthetic socket. Many prosthetists find, however, that retention of the fibular head is desirable because the modern total-contact socket can obtain a better purchase on the short stump. Transecting the hamstring tendons to allow a short stump to fall deeper into the socket also may be considered. Although the procedure has the disadvantage of weakening flexion of the knee, this has not been a serious problem, and genu recurvatum has not been reported.

Amputations in nonischemic limbs result from tumor, trauma, infection, or congenital anomaly. In each, the underlying lesion dictates the level of amputation and choice of skin flaps. Microvascular techniques have made preservation of transtibial stumps possible with the use of distant free flaps and “spare part” flaps from the amputated limb. A description of the classic transtibial amputation using equal anterior and posterior flaps follows.

Transtibial Amputation

Technique 16.1

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Place the patient supine on the operating table and use a pneumatic tourniquet for hemostasis.
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Beginning proximally at the anteromedial joint line, measure distally the desired length of bone and mark that level over the tibial crest with a skin-marking pen.
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Outline equal anterior and posterior skin flaps, with the length of each flap being equal to one half the anteroposterior diameter of the leg at the anticipated level of bone section.
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Begin the anterior incision medially or laterally at the intended level of bone section and swing it convexly distalward to the previously determined level and proximally to end at a similar position on the opposite side of the leg ( Fig. 16.2A ).
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When crossing the tibial crest, deepen the incision and mark the periosteum with a cut to establish a point for future measurement.
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Begin the posterior incision at the same point as the anterior and carry it first convexly distalward and then proximally as in the anterior incision (see Fig 16.2A ).
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Deepen the posterior incision down through the deep fascia, but do not separate the skin or deep fascia from the underlying muscle.
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Reflect as a single layer with the anterior flap the deep fascia and periosteum over the anteromedial surface of the tibia.
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Continue this dissection proximally to the level of intended bone section.
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Because it contracts, the anterior flap cannot be used to measure the level of intended bone section. Instead, use the mark already made in the tibial periosteum to measure the original length of the flap and reestablish the level of bone section. With a saw, mark the bone at this point.
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Insert a curved hemostat in the natural cleavage plane at the lateral aspect of the tibia so that its tip follows along the interosseous membrane and passes over the anterior aspect of the fibula to emerge just anterior to the peroneus brevis muscle.
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Identify and isolate the superficial peroneal nerve in the interval between the extensor digitorum longus and peroneus brevis, gently draw it distally, and divide it high so that it retracts well proximal to the end of the stump.
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Divide the muscles in the anterior compartment of the leg at a point 0.6 cm distal to the level of bone section so that they retract flush with the end of the bone. As these muscles are sectioned, take special care to identify and protect the anterior tibial vessels and deep peroneal nerve.
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Isolate these structures and ligate and divide the vessels at a level just proximal to the level of intended bone section.
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Exert gentle traction on the nerve and divide it proximally so that it retracts well proximal to the end of the stump.
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Before sectioning the tibia, bevel its crest with a saw: begin 1.9 cm proximal to the level of the bone section and cut obliquely distalward to cross this level 0.5 cm anterior to the medullary cavity.
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Section the tibia transversely and section the fibula 1.2 cm proximally.
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Grasp their distal segments with a bone-holding forceps so that they can be pulled anteriorly and distally to expose the posterior muscle mass.
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Divide the muscles in the deep posterior compartment 0.6 cm distal to the level of bone section so that they retract flush with the end of the bone. This exposes the posterior tibial and peroneal vessels and the tibial nerve lying on the gastrocnemius-soleus muscle group. Doubly ligate and divide the vessels and section the nerve so that its cut end retracts well proximal to the end of the bone.
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With a large amputation knife, bevel the gastrocnemius-soleus muscle mass so that it forms a myofascial flap long enough to reach across the end of the tibia to the anterior fascia ( Fig. 16.2B ).
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Smoothly round the ends of the tibia and fibula with a rasp and irrigate the wound to remove all bone dust.
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Release the tourniquet and clamp and ligate or electrocoagulate all bleeding points.
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Bring the gastrocnemius-soleus muscle flap over the ends of the bones and suture it to the deep fascia and the periosteum anteriorly ( Fig. 16.2C ).
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Place a plastic suction drainage tube deep to the muscle flap and fascia and bring it out laterally through the skin 10 to 12 cm proximal to the end of the stump.
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Fashion the skin flaps as necessary for smooth closure without tension and suture them together with interrupted nonabsorbable sutures.

Technique 16.2

(MODIFIED ERTL; TAYLOR AND POKA)

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Place the patient supine on a radiolucent bed; a tourniquet is used for hemostasis.
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Make an anterior incision at the level of the intended tibial resection and a posterior flap incision. The posterior flap should measure 1 cm more than the diameter of the leg at the level of bone division ( Fig. 16.3A ).
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Sharply incise the anterior compartment fascia, transect the musculature of the anterior compartment, and ligate the anterior neurovascular bundle.
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Identify the saphenous nerve, transect it proximally under tension, and allow it to retract.
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Identify the tibial resection site and elevate an osteoperiosteal sleeve proximal to the intended transection level both anteriorly and posteriorly before making the tibial cut ( Fig. 16.3B ).
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Measure the medial-to-lateral distance between the tibia and fibula at the area of transection and transect the peroneal muscle and fibula at this distance distal to the transected tibia.
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Transect the peroneal musculature and ligate the lateral neurovascular bundle.
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Transect the deep posterior compartment at the level of the tibial transection and sharply bevel the superficial posterior compartment to fashion a future flap.
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Identify the posterior compartment neurovascular bundle, ligate and transect it, allowing for retraction.
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Identify the sural nerve and transect it in the posterior subcutaneous flap.
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Remove the amputated limb from the operative field, saving bone for possible grafting.
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Osteotomize the remaining fibula at the level of the resected tibia; with a burr, create notches in the fibula and tibia for placement of the cut fibular autograft strut ( Fig. 16.3C,D ).
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Drill holes to accommodate heavy suture passage: two in the medial tibia, two in the medial fibular autograft, two in the lateral fibular autograft, and two in the distal fibula (screw fixation may alternatively be used; Fig. 16.3E ).
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Secure the autograft strut with heavy suture and sew the tibial periosteal sleeve around the strut distally. Autogenous bone graft may augment the distal bone bridge if necessary.
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Release the tourniquet and achieve hemostasis.
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Mobilize the peroneal musculature distally to cover the end of the bone bridge and suture it to the medial aspect of the tibia.
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Suture the posterior musculature to the anterior tibial periosteum and close the subcutaneous tissues. Use nonabsorbable stitches in a mattress fashion to close the skin.

Rehabilitation in Nonischemic Limbs

Rehabilitation after transtibial amputation in a nonischemic limb is fairly aggressive unless the patient is immunocompromised, there are skin graft issues, or there are concomitant injuries or medical conditions that preclude early initiation of physical therapy. An immediate postoperative rigid dressing helps control edema, limits knee flexion contracture, and protects the limb from external trauma.

A prosthetist can be helpful with such casting and can apply a jig that allows attachment and alignment for early pylon use. Weight bearing is limited initially, with bilateral upper extremity support from parallel bars, a walker, or crutches. The dressing is changed every 5 to 7 days for skin care. Within 3 to 4 weeks, the rigid dressing can be changed to a removable temporary prosthesis if there are no skin complications. The patient is shown the proper use of elastic wrapping or a stump shrinker to control edema and help contour the residual limb when not wearing the prosthesis. The physiatrist and therapist can assist in monitoring progress through the various transitions of temporary prosthetics to the permanent design, which may take several months. Endoskeletal designs have been more frequently used because modifications are simpler. Formal inpatient rehabilitation is brief, with most prosthetic training done on an outpatient basis. A program geared toward returning the patient to his or her previous occupation, hobbies, and educational pursuits can be structured with the help of a social worker, occupational therapist, and vocational counselor.

Ischemic Limbs

The frequent comorbidities in patients with ischemic limbs demand precautionary measures and interaction with a vascular surgical team. Because the skin’s blood supply is much better on the posterior and medial aspects of the leg than on the anterior or anterolateral sides, transtibial amputation techniques for the ischemic limb are characterized by skin flaps that favor the posterior and medial side of the leg. The long posterior flap technique popularized by Burgess is most commonly used, but medial and lateral flaps of equal length as described by Persson, skew flaps, and long medial flaps are being used. All techniques stress the need for preserving intact the vascular connections between skin and muscle by avoiding dissection along tissue planes and by constructing myocutaneous flaps. Also, amputations performed in ischemic limbs are customarily at a higher level (e.g., 10 to 12.5 cm distal to the joint line) than amputations in nonischemic limbs. Tension myodesis and osteomyoplasty, which may be of value in young, vigorous patients, historically have been contraindicated in patients with ischemic limbs due to concerns of blood flow restriction. However, recent data demonstrate that the Ertl procedure may be safe in these high-risk patients.

Traditionally, tourniquets have not been used in the amputation of dysvascular limbs to avoid damage to more proximal diseased arteries. However, recent studies (including randomized controlled trials) demonstrate decreased blood loss, decreased postoperative transfusion rates, and no increased risk of vascular or wound complications with the use of a tourniquet.

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