Techniques for lower extremity amputation

INTRODUCTION — Lower extremity amputation is performed to remove ischemic, infected, or necrotic tissue or locally unresectable tumor and may be lifesaving. The majority of lower extremity amputations are performed for lower extremity ischemia (peripheral artery disease, embolism) and diabetes mellitus. Extremity trauma is the second leading cause for amputation, and malignancy accounts for the remainder [1,2].

The techniques for major amputation and foot amputations are reviewed here. The indications for lower extremity amputation, preoperative and postoperative care, complications, and outcomes are reviewed separately. (See "Lower extremity amputation".)

SURGICAL ANATOMY

Hip and thigh — The hip joint is a multiaxial ball-and-socket joint. The ligamentous structures of the joint are the fibrous capsule; the acetabular labrum; the ligament of the head of the femur; and the iliofemoral, ischiofemoral, pubofemoral, and transverse acetabular ligaments.

The muscles that surround the hip joint are divided into three groups: anterior, posterior, and inferior. The anterior group, lateral to medial, includes the rectus femoris, iliopsoas, and pectineus. Anterior to this group are the sartorius and tensor fascia lata. The posterior group consists of the piriformis, obturator internus, quadratus femoris, and obturator externus.

The muscles of the thigh are divided into three groups (figure 1): the anterior group consists of the sartorius, tensor fascia lata, and quadriceps femoris (vastus medialis, intermedius, and lateralis, rectus femoris); the medial group includes the gracilis, pectineus, and adductor longus, brevis and magnus; the posterior group consists of the biceps femoris, semitendinosus and semimembranosus. The adductor muscles insert into the posterolateral femur along a narrow ridge called the linea aspera.

The femur articulates with the tibia via the knee joint while the fibula articulates with the tibia via the superior tibiofibular joint. The stability of the knee joint depends upon the anterior and posterior cruciate ligaments and medial and lateral collateral ligaments. The patellar ligament is the central portion of the common tendon of the quadriceps femoris, which inserts on the tuberosity of the tibia.

Leg — Four compartments contain the muscles of the leg (figure 2). The anterior compartment contains the tibialis anterior, extensor hallucis longus and the extensor digitorum longus muscles, and the deep peroneal nerve. The lateral compartment contains the peroneus longus and brevis muscles and the superficial peroneal nerve. The posterior compartment is subdivided into superficial and deep compartments. The superficial posterior compartment consists of the gastrocnemius and soleus muscles. The deep posterior compartment contains the tibialis posterior, flexor digitorum longus, and the flexor hallucis longus muscles. The tibial nerve runs distally in this compartment adjacent the posterior tibial artery.

The sural artery arises from the popliteal artery proximal to the tibial trifurcation and supplies the gastrocnemius muscle and the posterior skin. The skin of the leg is also supplied by fasciocutaneous perforating arteries that arise from the posterior tibial, anterior tibial, sural, saphenous, and peroneal arteries. To preserve adequate skin blood supply via these fasciocutaneous perforators, the skin and subcutaneous tissues should not be separated from the underlying fascia. The saphenous artery accompanies the saphenous vein and nerve (figure 3) below the knee and supplies the skin of the anteromedial leg along with perforating branches of the posterior tibial artery [3].

Ankle and foot — The tibia and the fibula are connected distally by a fibrous inferior tibiofibular joint that is sacrificed in conventional below-knee amputation (BKA). The tibia and the fibula articulate with the talus via the talocrural joint (figure 4). Ligamentous attachments include the deltoid, anterior and posterior talofibular, and the calcaneofibular ligaments. The talus articulates with the calcaneus at the subtalar joint. The medial and lateral talocalcaneal ligaments and the cervical ligament support this joint.

The talocalcaneonavicular joint (figure 4) is a multiaxial joint supported by the talonavicular and plantar calcaneonavicular ligaments. A heavy fibrofatty heel pad firmly adheres to the calcaneus and the skin and provides protection during heel strike. Supination (inversion) at this joint is produced by the tibialis anterior and posterior. Pronation (eversion) is produced by the peroneus longus and brevis. When these strong ankle extensor attachments are divided during midfoot and hindfoot amputation, the Achilles tendon exerts unopposed plantar flexor forces on the residual foot. The Achilles tendon may require division or lengthening to prevent an equinus deformity. (See 'Midfoot and hindfoot amputations' below.)

The metatarsal heads (figure 4) are stabilized by a series of segmental deep transverse metatarsal ligaments that connect the plantar ligaments of the adjacent metatarsophalangeal joints. Proximally, the metatarsals articulate with the three cuneiforms (medial, intermediate, and lateral) and the cuboid bone. These bones are connected by the dorsal and plantar tarsometatarsal and the interosseous cuneometatarsal ligaments. The tarsometatarsal, or Lisfranc's joint, connects the midfoot to the forefoot.

There are two phalanges in the first toe and three in each of the remaining four toes (figure 4). The interphalangeal and metatarsophalangeal joints are hinge joints. Each has an articular capsule and medial and lateral collateral ligaments. The plantar surface of the articular capsule is strengthened to form a fibrous plate (plantar ligament), which limits toe extension. The flexor hallucis longus and flexor digitorum longus tendons insert on the distal phalanges. The flexor hallucis brevis inserts on the proximal phalanx of the first toe. There are typically two sesamoid bones contained within the flexor hallucis brevis tendon that articulate with the plantar surface of the first metatarsal head.

GENERAL PRINCIPLES OF AMPUTATION — Regardless of the level of amputation, a number of general principles should be observed to minimize complications [4]. The level of the amputation is dictated by the extent of the disease, healing potential of the stump, and rehabilitation potential of the patient. Although preservation of limb length is desirable, removal of all nonviable and infected tissue is a higher priority. Amputations performed to resect tumors are dictated by the location of the tumor and the need for adequate margins. (See "Lower extremity amputation", section on 'Level and amputation types'.)

Staged amputation — Staged (two-stage) amputation involves first a debriding amputation in the form of an open "guillotine" amputation (transfemoral, transtibial), through-the-joint amputation, or less commonly, cryoamputation, followed by definitive revision and wound closure after infection has been controlled [5-9]. Debriding foot amputation at the toe, forefoot, or ankle level can also be used.

A debriding amputation is a rapid and effective method for removing infected or necrotic tissue that is a source of sepsis. Nonstaged amputations should be avoided in patients with severe lower extremity infections, particularly patients with diabetes with severe forefoot infections. A subset of patients with severe medical comorbidities may also benefit from a staged amputation. In two small trials, staged amputation was associated with better outcomes. In one of these trials, the incidence of postoperative stump infection was reduced (none versus 21 percent), rates of primary healing were higher (97 versus 78 percent), and fewer revisions (none versus 11 percent) were needed compared with nonstaged amputation [5]. Disadvantages of this technique include the need for a second procedure, additional anesthetic, prolonged hospitalization, and increased cost. Another disadvantage is the pain associated with dressing changes to the open stump.

Once the infected limb is removed, the patient is treated with antibiotics and open dressing changes for three to five days. If the white blood cell count is trending downward and the stump is clean, the second stage can be performed. At the second stage, the stump is debrided and closed. A drain is usually left in place. (See 'Dressings and drains' below.)

Cryoamputation — Cryoamputation refers to a bedside technique that uses dry ice to "hard freeze" the extremity, resulting in a physiologic amputation. Cryoamputation controls local infection by quarantining metabolic waste products within the frozen limb. For patients with indications for amputation but who have severe medical comorbidities that preclude safe anesthesia, cryoamputation can be used as a temporizing measure to avoid surgery until the patient can be stabilized medically [10,11]. However, cryoamputation is rarely needed where modern surgical and anesthetic techniques are available. Proponents of the technique report improved mortality compared with emergency amputation in appropriately selected patients [10,12,13]. The main complication associated with cryoamputation is migration of the frost line above the intended level of amputation [11]. The need for amputation stump revision may also be greater.

Draping — A mechanical barrier (impervious plastic sleeves, iodinated adhesive skin drape) should be used to isolate infected areas prior to undertaking amputation. For foot or toe amputation, adhesive drapes are impractical on the toes, but the finger of a surgical glove may serve as an effective condom to isolate a necrotic or septic area.

Tourniquets — Tourniquets have been shown to reduce intraoperative blood loss and decrease the need for postoperative blood transfusion in above-knee and below-knee amputations [14]. However, tourniquets are probably of little benefit in patients undergoing amputation for extremity ischemia.

To use a tourniquet, the extremity is first exsanguinated using elastic compression (eg, Esmarch), followed by placement of a sterile tourniquet usually in the proximal thigh (above-knee and below-knee amputation) or calf (foot amputations) and insufflated to 1.5 to 2.0 times the systolic pressure. Exsanguination is omitted if there is associated soft tissue infection.

Standard techniques — Specific surgical techniques minimize tissue ischemia when performing lower extremity amputation in patients with lower extremity ischemia, and these practices are equally applicable to lower extremity amputation in patients with normal lower extremity perfusion, such as the younger patient with extremity injury or a patient with a Charcot foot deformity.

●Handle the soft tissues gently.

●Avoid beveling of the skin and tissues by maintaining the scalpel perpendicular to the skin surface.

●Do not separate the skin from the underlying fascia to prevent ischemia of the skin flaps.

●Use skin hooks or fine-toothed forceps to retract the skin, and not crushing instruments (eg, Debakey forceps). Some surgeons rely only on gentle finger retraction.

●Dissect named arteries and veins free from one another and ligate and divide each separately to prevent arteriovenous fistula formation. Oversew major arteries and ligate them more proximally. Simple ligation is adequate for occluded or partially occluded vessels (minimal flow). Simple ligation suffices for most veins.

●Ligate nerves just proximal to their point of transection to minimize bleeding from the perineurium and transect the nerve sharply proximal to the weight-bearing surface to avoid the development of neuroma, which can lead to chronic stump pain. Target muscle reinnervation and a regenerative peripheral nerve interface are alternative options to consider to decrease postoperative neuroma formation [15-17].

●Minimize the use of electrocautery by using suture ligatures for hemostasis.

●Avoid creating surgical scars (new or old) on the weight-bearing surface.

●Prevent scar retraction by interposing muscle and fascia between the skin and cut surface of bone.

●Approximate skin flaps without tension. Skin closure with either monofilament sutures or staples is acceptable.

●Avoid excessive trimming of small dog-ears or other minor cosmetic irregularities. Although a large amount of redundant soft tissue will interfere with proper prosthetic fit, minor irregularities will remodel.

●Irrigate the wound thoroughly once the dissection is complete to remove any debris or bony fragments.

●Stabilize antagonistic muscle groups using myoplasty (suture fixation of antagonistic muscle groups to bone) or myodesis (suturing the muscle to the periosteum) to prevent muscle atrophy and skeletal misalignment [18].

●Bevel bony prominences and file sharp edges smooth.

●Avoid excessive periosteal stripping to prevent ring sequestra or bony overgrowth.

●Close the amputation stump in layers with interrupted absorbable sutures. The use of skin staples has been associated with an increased risk for infection [19].

Adjunctive techniques

Osseous integration — Osseous integration involves implanting an anchoring system directly into the bone, typically using a two-stage procedure for the reconstruction and rehabilitation, with several weeks between the two stages. There has been attempts at performing this in one stage [20]. Different types of osseointegration have been described. These are Osseointegrated Prostheses for the Rehabilitation of Amputees (OPRA), the Integrated Leg Prosthesis (ILP), and the Osseointegrated Prosthetic Limb (OPL). Primary concerns with the osseointegration techniques are periprosthetic fracture and infection leading to osteomyelitis [21].

Agonist-antagonist myoneural interface amputation — The agonist-antagonist myoneural interface amputation is a procedure that restores physiological agonist-antagonist muscle relationships with the aim of improving proprioceptive sensory feedback to the brain from the stump, which may help improve prosthetic control and reduce pain [22,23].

Target muscle reinnervation — Target muscle reinnervation (TMR) is a procedure that was originally used when attaching a myoelectric prosthesis after an upper extremity amputation (figure 5). Subsequently, TMR has been successfully used with lower extremity amputation in prevention and treatment of neuromas and phantom limb pain in lower extremity amputations [16,24]. (See "Lower extremity amputation", section on 'Phantom limb pain'.)

MAJOR AMPUTATIONS — Major amputations of the lower extremity are those above the level of the ankle. These include hip disarticulation, above-knee amputation (transfemoral), knee disarticulation, and below-knee amputation (transtibial). Techniques to perform these procedures are discussed below.

Hip disarticulation — To perform a hip disarticulation, an anterior racquet incision or a long posterior flap incision can be used (figure 6) [25]:

●The anterior racquet incision starts an inch medial to the anterior superior iliac spine, extends to the pubic tubercle, and continues posteriorly distal to the ischial tuberosity and gluteal crease. The incision continues anteriorly, medial to the greater trochanter and the anterior inferior iliac spine to rejoin the starting point.

●To create a posterior flap, the incision begins an inch inferior and parallel to the inguinal ligament anteriorly and extends to the posterior thigh to create a flap. The length of the posterior flap is one and a half times the diameter of the thigh at the level of the hip joint.

Once the skin incision has been made, the femoral artery and vein are identified and ligated. The musculature and associated vessels and nerves in the proximal thigh are divided, beginning anteriorly and progressing posteriorly (figure 6). The sartorius and iliopsoas muscles are divided at the anterior superior iliac spine and lesser trochanter, respectively. The pectineus, gracilis, and adductor muscles are divided at their origins at the pubis and ischium. The obturator neurovascular bundle is then ligated and divided. The obturator externus muscle is divided from its insertion to the lesser trochanter. The hamstrings (semimembranosus, semitendinosus, and biceps femoris) are divided at the ischial tuberosity. Next, the tensor fascia lata, gluteus maximus, and rectus femoris are divided. Finally, the muscles attached to the greater trochanter are divided. The ligamentum teres is divided and the capsule of the hip joint is incised. The sciatic nerve is ligated and transected and will retract posterior into the piriformis muscle. The limb is passed off the operating table.

Myoplasty is then performed by joining the flexors and extensors over the acetabulum. The quadratus femoris posteriorly is sutured to the iliopsoas anteriorly. Next, the gluteus medius laterally is sutured to the obturator externus medially. The gluteal fascia is approximated to the inguinal ligament and the skin closed loosely.

Above-knee amputation — For above-knee (transfemoral) amputation, the level of amputation can be chosen to divide the femur at the junction of its middle and distal third in most patients. A hemostatic tourniquet can be used if the femur is of sufficient length. (See 'Tourniquets' above.)

A transversely oriented fish-mouth (figure 7) with equal anterior and posterior flaps is commonly used, but sagittal flaps are equally effective. Some surgeons prefer a simple, circular incision. Almost any incision that results in sufficient soft tissue coverage is appropriate.

The fascia and muscles of the anterior thigh are divided, and the superficial femoral artery and vein are identified medially, divided, and sutured closed. The remainder of the thigh musculature is divided laterally and posteriorly. The femur is transected two fingerbreadths proximal to the skin incision to provide adequate skin and soft tissue coverage over the bone. The sciatic nerve is ligated, divided sharply, and allowed to retract. The edges of the transected femur are smoothed with a rasp or file. It is important to flex the patient's hip prior to closing the wound. If hip flexion leads to tension on the wound, the femur should be shortened.

Myopexy of the posteromedial musculature should be performed prior to skin closure. Myopexy prevents a dysfunctional and cosmetically unappealing stump due to the unopposed action of the hip flexors causing abduction and flexion of the proximal femur in the absence of the posteromedial adductor muscles. Myopexy is performed by sewing the muscles of the posterior and medial compartment to the periosteum anterolaterally on the femur. Some surgeons use direct myoplasty of the adductor muscles by passing nonabsorbable suture through holes drilled into the anterolateral femur. Following either myopexy or myoplasty, the deep fascia is approximated with absorbable suture. The skin can be closed using staples or interrupted monofilament sutures.

Through-the-knee (knee disarticulation) — Compared with a traditional transfemoral amputation, a through-the-knee amputation is an attractive alternative because it results in a longer lever arm and uses a simple end weight-bearing prosthesis compared with ischial weight-bearing that is needed for an above-knee prosthesis [26]. The functional outcome may be superior to below-knee amputation in some patients, such as those with severe ischemia or wounds that would limit the creation of an adequate below-knee stump or prevent proper fitting of a below-knee prosthesis. The main disadvantage of this amputation is that wound problems may require revision to a higher level. We reserve this technique for younger patients who have an above-average rehabilitation potential who are not candidates for transtibial amputation. Whether there are any benefits in using a through-the-knee amputation in nonambulatory patients is unresolved.

Equal anterior and posterior flaps (figure 8) are usually made, but equal sagittal (medial/lateral) flaps can also be used. The apex of the anterior flap should be positioned between the distal patella and the tibial tuberosity. The skin is incised circumferentially and the medial and lateral collateral ligaments are divided. The patellar tendon is divided at its insertion into the tibia. The joint capsule is incised anteriorly and the cruciate ligaments are divided. The popliteal artery and vein are identified, divided, and sutured closed. The popliteus muscle and gastrocnemius muscles are then divided. The remaining attachments of the hamstring muscles are divided and the knee disarticulated. The transected end of the patellar tendon is sutured to the cruciate ligaments and the hamstring tendons in the intercondylar notch under slight tension using nonabsorbable suture. The wound is irrigated with sterile saline and closed in layers with interrupted absorbable sutures.

The Gritti-Stokes amputation divides the distal femur (anterior to posterior angle of 10°) just distal to the insertion of the adductor magnus prior to suturing the tendons together [27]. The angulation allows the patella (after its articular surface has been resected) to fit snugly onto the end of the femur [28]. Another technique is to remove the posterior, medial, and lateral projections of the femoral condyles (Mazet modification) [29].

Below-knee amputation — Amputation techniques for below-knee amputation are named for the origin of the flap used to cover the tibia. The posterior flap is the most commonly used technique for below-knee amputation and can be used for any indication [30-32]. The advantage of this technique is the placement of the incision, and resultant scar, on a surface that is not weight bearing. A disadvantage is the potential for ischemia in the posterior flap.

Four other below-knee (transtibial) amputation techniques are described using sagittal, skew, medial, and fish-mouth flaps (figure 9), each of which may be more useful when one flap may be better vascularized than another.

A systematic review identified three randomized trials comparing the posterior flap with other flap techniques for lower extremity amputation. No significant differences were observed in rates of primary stump healing, postoperative wound necrosis, reamputation, or mortality [33].

Posterior flap technique — The tibia should be divided ideally 10 to 12 cm (three or four fingerbreadths) distal to the tibial tuberosity (figure 10). However, a functional stump may still be possible with as little as 5 cm of residual tibia.

The anterior incision extends from medial to lateral, encompassing one half to two thirds of the circumference of the leg (figure 9). The length of the posterior flap is approximately one third the circumference of the leg. A wider posterior flap may be better vascularized but will result in more prominent dog-ears with skin closure. Gently curving the transition of the posterior flap to the anterior incision will help reduce redundant skin and limit the formation of dog-ears. The skin and fascia are incised and divided beginning anteriorly and extending to the posterior flap. The muscles of the anterior and lateral compartment muscles are divided.

The periosteum of the tibia is incised circumferentially two fingerbreadths proximal to the skin incision, and the tibia is divided using a powered saw perpendicular to the long axis of the bone. The anterior surface of the tibia is beveled to eliminate sharp edges that may cause pressure on the overlying skin. The fibula is divided with a saw 1 to 2 cm proximal to the tibial transection site. Excessive resection of the fibula results in a conical stump that is difficult to fit properly with a prosthetic. The bony surfaces are filed smooth. The posterior flap is completed by dividing the residual posterior compartment musculature at a plane just deep to the tibia and fibula with a long amputation knife.

Hemostasis is achieved by identifying the anterior tibial, posterior tibial, and peroneal vessels. The arteries are suture ligated; the veins may be simply ligated. The associated tibial and peroneal nerves are ligated and sharply divided and allowed to retract. The sural nerve is identified in the subcutaneous tissue in the midline of the posterior flap and divided 5 or 6 cm proximal to the skin edge. Smaller vessels bleeding from the surface of the musculature are suture-ligated.

The deep fascia of the posterior flap is sutured to the fascia anteriorly with interrupted absorbable sutures, taking care to completely cover the tibia without tension. Some surgeons prefer to advance the posterior flap 3 to 4 cm proximal to the tibial osteotomy [34]. If the posterior flap is too bulky to allow tension-free closure, the soleus muscle can be excised at the proximal level of the tibial osteotomy and removed, taking care to preserve the fascia and gastrocnemius muscle. The skin is closed with staples or interrupted monofilament suture.

Other flap techniques — If the creation of a long posterior flap is not possible, skew or sagittal flaps can be used. The disadvantage of these techniques is the creation of a scar on the weight-bearing surface. Fish-mouth and medial-based flap techniques are discussed below for completion, but these techniques are rarely used.

●Skew – With a skew flap technique, equal anteromedial and posterolateral fasciocutaneous flaps are created (figure 9 and figure 11). The posterior muscle flap is similar to the conventional long posterior flap and based on the gastrocnemius muscle but is shorter [35]. The skew technique is useful if there is inadequate skin to create a conventional long-posterior flap.

●Sagittal – In the sagittal flap technique, equal length medial and lateral myocutaneous flaps are created (figure 9) [36]. A myoplasty is performed to cover the tibia by suturing the anterior and lateral compartment muscles to the medial component of the gastrocnemius and soleus [37].

●Medial – A medial flap technique constructs a long medial flap and short lateral flap. Incisional planning is based on thermographic imaging (figure 9 and figure 12) [38].

●Fish mouth – Prior to the development of the long posterior flap, the equal anterior and posterior flap technique was the most common transtibial amputation technique (figure 9). The main disadvantage is the vulnerability of the anterior flap to ischemia. The fish-mouth incision has no advantages over other techniques and is rarely indicated.

Adjunctive techniques — A modification of below-knee amputation, Ertl amputation, also known as amputation osteoplasty or tibiofibular bone bridging, is thought by some to improve transmission of torque from the distal femur to the prosthesis [39]. The procedure involves creating a bone bridge between the distal tibial and fibular using a portion of the fibula from the amputated limb [40]. The efficacy of this technique compared with standard transtibial amputation without distal bone bridging remains controversial [40-42].

FOOT AMPUTATIONS — Patients are more likely to ambulate with a foot amputation compared with a below-knee amputation; however, more distal amputations are more likely to require reamputation or revision to a higher level compared with more proximal amputation. (See "Lower extremity amputation", section on 'Need for re-amputation'.)

In cases in which there is a low likelihood of healing of a minor amputation, it is important to explain to the patient the risk and consequences of failure. Although the patient may wish to preserve the extremity for as long as possible, prolonging the patient's course with multiple trips to the operating room to manage a nonhealing amputation stump or progressively more proximal amputations cannot be justified.

Ankle disarticulation — Open ankle disarticulation is a quick and simple amputation that can be used to manage a septic foot. Because no bones are transected, it can be performed with local anesthesia (and sedation, if tolerated hemodynamically) at the bedside if the patient is too ill to transport to the operating room. The procedure involves making a circumferential incision at the level of the ankle joint after the placement of a proximal tourniquet. The incision is carried through the tendons of the foot and into the joint capsule followed by transection of the ligaments. The subcutaneous anterior tibial and posterior tibial vessels are identified, ligated, and divided.

Midfoot and hindfoot amputations — Five midfoot and hindfoot amputations are available and are occasionally useful in selected populations of patients. These include Lisfranc, Chopart, Syme, Boyd, and Pirogoff amputations (figure 13A-B) [43,44]. These amputations were developed when options for lower extremity prostheses were limited and preservation of any portion of the foot was an advantage. The Boyd and Pirogoff hindfoot amputations are used primarily in children to preserve length and bony growth centers [43,45-47].

The use of midfoot and hindfoot amputations in patients with diabetes remains controversial. Many surgeons recommend formal transtibial (below-knee amputation) if transmetatarsal amputation (TMA) cannot be performed or has failed. Others suggest that increased limb salvage rates can be improved using proximal foot amputation [46,48]. Preservation of limb length may have a survival advantage for patients with diabetes, with one study reporting that patients with diabetes undergoing proximal foot amputations had better function and survival compared with below-knee amputation [47]. These findings were not observed in dialysis-dependent patients with diabetes.

The chief advantage of the Syme amputation is the preservation of native limb length that may allow brief periods of weight bearing without the need for a prosthesis, such as during transfer from a bed to wheelchair or to the bathroom. The disadvantages include a slight leg length discrepancy, which may lead to biomechanical side effects in more proximal or contralateral joints. When a prosthesis is used, it is typically quite bulky at the ankle and less cosmetically appealing than a conventional below-knee prosthesis, which can be designed with a near-normal ankle profile. Because the Syme amputation is an end weight-bearing stump, the heel fat pad may become unstable and can migrate medially, exposing the distal tibia to excessive force. Thus, the Syme amputation has its greatest utility in young, otherwise healthy patients (eg, extensive forefoot injury) who are highly motivated to avoid transtibial amputation. Diabetic neuropathy is a relative contraindication to Syme amputation because of the patient's inability to protect the stump from injuries.

The basic principles of the more common midfoot and hindfoot amputations are described below [49,50].

●Syme amputation – The anterior incision of the Syme amputation extends across the ankle just distal to the tip of each malleolus (figure 14). The posterior incision extends from the malleoli vertically and transversely across the heel. The extensor tendons are divided at the level of the skin incision. The dorsalis pedis artery and vein are divided and ligated. The ankle joint capsule is incised while plantar-flexing the foot. The medial and lateral ankle ligaments are divided. The tendons of the posterior tibialis and flexor hallucis longus are transected, taking care to avoid injury to the posterior tibial artery. The heel fat pad is carefully dissected by staying close to the calcaneus to avoid creating a buttonhole. The ankle joint is disarticulated, and the foot is passed from the table.

In a single-stage amputation, the malleoli are divided with a saw at the level of the articular surface of the tibia, and the width is reduced by vertical bone excision. Holes are drilled in the medial, anterior, and lateral parts of the distal tibia and fibula to secure the heel pad directly under the tibia. In a two-stage Syme amputation, the wound is closed by suturing the heel flap to the dorsal fascia. Six weeks later, the malleoli are removed through separate vertical incisions.

●Lisfranc tarsometatarsal disarticulation – The incision is placed over the metatarsal heads and produces a long plantar flap. The tendons and synovial sheaths are divided at the level of the skin incision. The 2^nd metatarsal is divided 1 to 2 cm distal to the medial cuneiform (figure 13A-B) [27]. The 1^st, 3^rd, 4^th and 5^th tarso-metatarsal joints are disarticulated. To reduce the risk of developing equinovarus deformity, a modification of the Lisfranc amputation (Sanders) preserves the insertion of the peroneus brevis muscle at the base of the 5^th metatarsal [46]. The Achilles tendon is released by transection or Z-plasty [51,52]. The plantar fascia of the posterior flap is approximated to the dorsal periosteum with absorbable sutures and the skin is closed.

●Chopart midfoot amputation – The incision is placed over the talocalcaneonavicular joint and a long plantar flap is created similar to the Lisfranc amputation. The amputation is performed through the talocalcaneonavicular joint and calcaneocuboid joints (figure 13A-B). The extensor hallucis longus and the tibialis anterior tendons can be reattached to the talar neck. The extensor digitorum longus can be reattached to the calcaneus [27]. To prevent equinovarus deformity due to unopposed plantar flexion, Achilles tendon release should be performed. The plantar fascia of the flap is approximated to the dorsal periosteum and the skin is closed.

Transmetatarsal amputation — Transmetatarsal amputation (TMA) is appropriate for wounds that involve the entire forefoot. TMA offers the benefits of full limb length, normal shoes, and near-normal ambulation. Foot mechanics, healing, and rehabilitation rates may be improved with TMA compared with first ray amputation, and TMA may be preferred to manage foot wounds in selected patients. TMA is contraindicated if excessive bony deformity is present in the midfoot or hindfoot that would compromise foot stability. (See 'Ray' below.)

The incision is made from a point just medial to the first metatarsal head transversely across the dorsum of the foot to the lateral aspect of the fifth metatarsal head (figure 15) [45]. The incision extends around to the plantar surface to the base of the toes to create a plantar flap. The extensor tendons and sheaths are divided at, or slightly proximal to, the dorsal skin incision to expose the metatarsal shafts. The periosteum is divided just proximal to the metatarsal heads, and the metatarsals are transected using a power microsaw.

We prefer to divide the metatarsals in a gentle curve from medial to lateral starting at the great toe with each successive shaft (digits 2 through 5) transected 3 to 5 mm shorter than the previous one. Some surgeons advocate transecting the metatarsal shaft with a 30 to 45 degree plantar-oriented bevel to facilitate lift-off during ambulation.

Following transection of the metatarsal bones, the distal metatarsal fragments can be grasped with a bone clamp or bone hook and retracted to divide the associated plantar myofascial attachments. The flexor tendons and sheaths are poorly vascularized, and these should be excised individually along with associated fibrocartilaginous structures on the plantar flap, taking care to not incise too deeply into the flap.

The wound is irrigated and closed in two layers with interrupted absorbable sutures in the fascia. The skin is closed loosely with interrupted nonabsorbable monofilament sutures or staples.

Toe amputation — Simple toe amputation is appropriate for wounds limited to the mid- to distal toe and not involving the skin overlying the metatarsal head. More proximal wounds typically require ray amputation.

Local anesthesia (ankle or digital nerve block) is usually adequate for most toe amputations. Care should be taken to avoid direct puncture of the pedal arteries or excessive infiltration of anesthetic in the dysvascular foot because of the risk of exacerbating ischemia. Some surgeons avoid the use of ankle blocks and digital blocks in the setting of local foot sepsis because of concern for spreading infection. (See "Lower extremity nerve blocks: Techniques", section on 'Ankle block' and "Digital nerve block", section on 'Great toe' and "Digital nerve block", section on 'Other toes'.)

Simple — Partial or complete amputation of any toe can be performed. However, since a hallux valgus deformity commonly develops following isolated partial or complete second toe amputation, a second ray amputation may be preferable to simple toe amputation because it reduces the angle between the first and third metatarsals. (See 'Ray' below.)

Almost any incision that results in tension-free coverage of the transected bone can be used. For partial toe amputation, a transverse or vertical fish-mouth skin incision should suffice. The simplest technique for complete toe amputation is with a racquet incision (figure 16). For amputation of the first and fifth toes, we prefer to orient the handle of the racquet on the medial or lateral surface of the respective metatarsal head. For the second, third, and fourth toes, the handle of the racquet is oriented longitudinally along the dorsal surface of the digit.

The flexor and extensor tendons are divided at the level of the skin incision and allowed to retract. The bone is divided at the appropriate level. If disarticulation is needed, a #15 knife blade can be inserted into the joint and the joint capsule incised sharply to avoid injury to surrounding soft tissue. Since the articular cartilage is poorly vascularized, we prefer to excise it with a rongeur. We also gently shape the exposed bone to eliminate any bony projections that might lead to wound or skin problems. After irrigation and hemostasis, the skin is closed without tension with a single layer of nonabsorbable monofilament sutures.

Ray — The term "ray amputation" is used to describe amputation of the toe along with all or part of the corresponding metatarsal bone. Ray amputation is useful for managing mal perforans ulcers in the neuropathic diabetic foot, particularly when associated with osteomyelitis of the metatarsal head. Ray amputation is also appropriate for the treatment of digit thromboembolism that involves the toe and its base. In these circumstances, resection of the toe alone may leave insufficient skin to cover the exposed metatarsal head.

Although an isolated single ray amputation can be durable, multiple ray amputations narrow the foot excessively and create an unstable foot that increases the load on the remaining metatarsal heads, which can result in new areas of increased pressure, callus formation, and ulceration. Transmetatarsal amputation is preferred to multiple ray amputations. (See 'Transmetatarsal amputation' above.)

Near-normal foot mechanics can be achieved after amputation of the individual lateral four rays, but amputation of the great toe and first metatarsal head markedly alters foot mechanics and normal ambulation. Recurrent ulceration following first ray amputation occurs in up to 60 percent of patients [53]. As a result, some surgeons recommend formal transmetatarsal amputation rather than isolated first ray amputation [54]. However, given that 40 percent of patients do not require revision or reamputation, others feel that first ray amputation is justified [55,56]. Given the lack of consensus, the choice between first ray amputation and transmetatarsal amputation should be individualized. (See 'Transmetatarsal amputation' above.)

In a typical ray amputation, we modify the racquet incision by extending the handle of the racquet along the dorsal surface to provide exposure of the shaft of the metatarsal bone (figure 17). The extensor tendons are divided and allowed to retract, and the shaft of the metatarsal head is transected with a power microsaw. The distal segment of metatarsal is retracted with a bone hook, and the remaining plantar soft tissue attachments are divided. Care is taken to stay close to the bone to avoid injury to the adjacent digital arteries and nerves. Sesamoid bones are excised and the flexor tendons are transected under tension so they retract. After irrigation and hemostasis, the skin is closed without tension with a single layer of nonabsorbable monofilament sutures.

DRESSINGS AND DRAINS — A wide variety of soft, semirigid, and rigid removable dressings have been developed for use after amputation, but there is no consensus regarding the optimal method of stump treatment [57-60]. The ideal stump dressing protects the wound from contamination and trauma, allows easy access for wound examination, prevents contractures, and minimizes edema without restricting stump perfusion.

All caregivers should be aware that accidental injury following amputation is a frequent cause of stump failure and need for stump revision. Injury to the stump is prevented by the use of appropriate protective soft or rigid dressings depending upon the nature of the amputation. In most cases, weight bearing should be completely avoided until the wounds are well healed. (See "Lower extremity amputation", section on 'Weight bearing and ambulation'.)

In general, our initial postoperative dressing consists of a gauze dressing or wrap on the stump over which a loose elastic dressing is placed. A rigid dressing (splint, immobilizer) may also be placed. The dressing is maintained for a 24 hour period, after which it is removed. Suggested dressings for the various amputation sites are given below:

●Toe – Simple, bulky, soft dressing and postoperative shoe.

●Partial foot – For transmetatarsal amputation, a posterior plaster splint is applied to maintain the foot at 90°. For proximal foot amputations, a short leg plaster cast is used over the sterile dressings. The cast must be molded to ensure that the talus is slightly dorsiflexed in relation to the tibia and the calcaneal tuberosity is parallel to the long axis of the tibia. The cast is changed weekly to check the healing of the wound.

●Below-knee – A soft dressing is applied over the stump and a rigid dressing used to prevent postoperative knee contracture. We prefer a simple knee immobilizer with Velcro straps because it is widely available and can be easily removed to examine the wound. A foam cylinder can be cut to shape and inserted into the end of the knee immobilizer to provide additional protection to the stump.

●Above-knee – A simple dressing is appropriate for above-knee and through-knee amputations. Care must be taken to avoid constrictive, circumferential dressings that impair blood flow. A simple and effective dressing consists of nonadherent gauze on the suture line covered with a protective adhesive sheet.

COMPLICATIONS — Complications following lower extremity amputation are common. Local wound complications include stump hematoma, infection, flexion contracture, and chronic stump pain, whereas systemic complications include, but are not limited to, acute cardiac events, venous thromboembolism, pneumonia, new-onset renal failure, and sepsis. The complications of lower extremity amputation are discussed in detail elsewhere. (See "Lower extremity amputation", section on 'Complications'.)

SUMMARY AND RECOMMENDATIONS

●Lower extremity amputation – Lower extremity amputation is indicated to remove ischemic, infected, or necrotic tissue or locally unresectable tumor and, at times, may be lifesaving. Peripheral artery disease and diabetes are the leading causes of lower extremity amputation in the United States. Extremity trauma is the next most common cause of amputation.

•Major amputation – Major amputations are those amputations performed above the ankle and include hip disarticulation, above-knee (transfemoral) amputation, through-knee amputation, and below-knee (transtibial) amputation.

•Foot amputation – A variety of foot amputations are available that may salvage the patient's ability to ambulate using orthotic shoe modifications. These include transmetatarsal amputation, toe amputation and various midfoot and hindfoot amputations (Syme, Lisfranc, Chopart). The amputation techniques for each are discussed above. (See 'Major amputations' above and 'Foot amputations' above.)

●Staged amputation – For patients with severe lower extremity infection requiring amputation, particularly in patients with diabetes, we suggest a staged amputation rather than a nonstaged amputation (Grade 2B). Staged amputation involves first a debriding amputation in the form of an open "guillotine" amputation (transfemoral, transtibial), through-the-joint amputation, or less commonly cryoamputation, with definitive revision and wound closure after infection has been controlled. Debriding foot amputation at the toe, forefoot, or ankle level can also be used. (See 'Staged amputation' above.)

●Standard techniques – The level of the amputation is dictated by the extent of the disease, healing potential of the stump, and rehabilitation potential of the patient. Although preservation of limb length is desirable, removal of all nonviable and infected tissue is a higher priority. Amputations performed to resect tumors are dictated by the location of the tumor and the need for adequate margins.

•Certain general techniques are universal to all amputations, regardless of the level. These include gentle tissue handling, minimizing tissue ischemia, ensuring adequate hemostasis, using techniques that prevent postoperative complications (eg, oversewing named vessels, minimizing electrocautery), liberal wound irrigation before closure, and closure without tension. The use of a proximal tourniquet, whenever possible, minimizes blood loss and the need for postoperative transfusion. (See 'Standard techniques' above.)

•For transtibial amputation, we suggest the posterior flap technique over other flap techniques (Grade 2C). The advantage of this technique is the placement of the incision, and the resultant scar, on a surface that is not weight bearing. A disadvantage is the potential for posterior flap ischemia. Four other below-knee (transtibial) amputation techniques (named for the origin of the flap used to cover the tibia) are sagittal, skew, medial, and fish-mouth flap (figure 9), each of which may be more useful where one flap may be better vascularized than another. (See 'Below-knee amputation' above.)