Chapter 30 Lower Extremity Amputations

This chapter will provide an overview of the types of amputations of the lower extremity. The general considerations and surgical principles of lower extremity amputations overlap considerably with those of the upper extremity (chapter 29). The techniques for below-the-knee, through-the-knee, and above-the-knee amputations, as well as hip disarticulation, will be presented.

Learning Objectives

By the end of this ASSET module, participants should be able to do the following:

1. Discuss the levels of amputation of the lower extremity and indications for damage control techniques.
2. Demonstrate formal definitive closure of a below-the-knee amputation with tension-free closure of the stump and adequate posterior flap.
3. Demonstrate formal definitive closure of a through-the-knee amputation with tension-free closure.
4. Demonstrate formal definitive closure of an above-the-knee amputation with tension-free closure.
5. Outline the steps for performing a hip disarticulation.

General Considerations and Surgical Principles

• The general considerations and surgical principles for the management of patients with or needing amputations of the lower extremity are very similar to those outlined in the previous chapter (chapter 29) on upper extremity amputations.
• As with the upper extremity, scoring systems or parameters do not accurately predict the need for amputation. Furthermore, for lower extremity injuries, the loss of plantar sensation immediately after injury does not accurately predict long-term functional outcomes; likewise, sensation is not necessarily an indication for amputation.
• Amputations should be carried out at the lowest level possible, with preservation of as much viable tissue as possible at the first operation and more formalized shaping and closure of the amputation site at a subsequent operation.
• It must be kept in mind that the desired end goal of amputation is ability to bear weight, and for this reason, adequate soft tissue coverage over the end of the stump is more important than extra length.
• The classically described levels of amputation for the lower extremity are seen in Figure 1.
• Functionally, below-the-knee amputation is superior to above the knee, which increases energy expenditure by 65 percent above baseline and is more likely to result in joint contracture.

• If below-the-knee amputation is not possible, knee disarticulation should be considered before above-the-knee amputation.
• As with the upper extremity, it is best to leave the wounds open after hemorrhage control, restoration of perfusion, and thorough debridement, delaying formal shaping and closure of the amputation for a subsequent return to the operating room.
• In complex blast injuries or wounds with significant soft tissue injury, contamination may be extensive, with debris forced well outside the zone of apparent injury. This necessitates meticulous and repeated debridement, with extension of the wounds and development of atypical skin or tissue flaps, if indicated.
• In traumatic amputations following blasts, the zone of soft tissue generally extends much further proximal than the damage to the bone.
• The amputated limb may be a source of autologous veins or arteries for subsequent vascular repair.

Below-Knee (Transtibial) Amputation (BKA)

BKA Considerations

• It has long been accepted that the middle third of the lower leg is the best site for a BKA, creating a stump 14–18 cm below the knee joint (Figure 2).
• Circulation in the lower third of the leg is relatively poor, and though satisfactory results can be obtained at this level, the presence of poor perfusion or significant soft tissue trauma may necessitate a higher level of amputation.
• The anterior aspect of the tibial crest, which lies close to the surface of the skin, should be slightly beveled.
• The fibula is normally non–weight-bearing, and in short stumps it is advisable to completely excise it. For stumps of average length, it is advisable to section the fibula 2–3 cm above the end of the tibia to facilitate fit in a prosthetic socket (Figure 2).

BKA Surgical Technique

• The entire leg is prepped circumferentially to the groin.
• A small bump placed under the ipsilateral hip to internally rotate the leg is helpful.
• A sterile tourniquet can be applied to the thigh.
• The classic BKA incision involves the creation of a long posterior myocutaneous flap (Figure 3).
• The anterior transverse skin incision is made 10– 12 cm (roughly one hand width) below the tibial tuberosity and extended to the lateral aspects of the calf.
• For the posterior flap, the coronal (anterolateral) incision is extended along the vertical axis of the calf for slightly longer than the maximum anteroposterior diameter of the limb, or about 1.5 times the length of the anterior flap (Figures 2 and 3).
• The posterior flap should be distal to the musculotendinous junction of the gastrocnemius muscle.
• The distal ends of the flap should be rounded to prevent redundancy.

• The skin and subcutaneous tissue are divided sharply, and the saphenous vein is ligated (Figure 4).
• The muscular attachments to the tibia are cleared with a periosteal elevator, and the interosseous membrane is divided sharply. The tibia is then divided with a saw (Figure 5), the anterior lip is beveled, and any sharp edges are filed smooth with a rasp.
• The lateral compartment muscles are divided sharply. The fibula is identified and cleared from soft tissue using a periosteal elevator. The fibula is resected, leaving a length of about 2–3 cm shorter than the tibial stump (Figure 6), and any sharp edges are filed smooth with a rasp.
• The anterior compartment muscles are transected sharply, and the anterior tibial artery and vein, as well as the deep peroneal (fibular) nerve, are identified. The vessels are suture ligated, and the nerve is divided sharply with distal traction to allow the nerve ending to retract proximally.
• The muscles of the posterior compartment are divided, utilizing an amputation knife or a scalpel to create a tapered posterior musculofascial flap (Figure 7).

• Enough of the soleus muscle should be removed to prevent excessive bulk or tension in the closure of the flap.
• The posterior tibial and peroneal vessels should be suture ligated when encountered. The tibial nerve should be transected sharply while employing distal traction to allow the nerve ending to retract proximally (Figure 8).
• The adequacy of hemostasis is checked, and the resulting myofascial flap is rotated over a drain to cover the transected bones.
• The posterior fascia is closed and sewn to the anterior fascia with interrupted absorbable sutures to create a tension-free closure (Figure 9). Tension-free closure must be ensured.
• The skin is closed without tension using interrupted mattress sutures (Figure 10).

BKA Pitfalls

• Failure to create a posterior flap long enough to cover the tibia will place the suture line under tension.
• Failure to make a smoothly curved posterior incision may result in excess skin and “dog- ears.”
• Removal of too much soleus muscle from the posterior flap may cause pain and irritation of the skin.
• Failure to transect the fibula 2–3 cm proximal to the tibial transection may result in pain and difficulty in fitting a prosthesis.

Knee Disarticulation (Through-Knee Amputation/TKA)

TKA Considerations

• A classically described knee disarticulation leaves the femur and patella untouched, offering some advantages over an above-knee amputation.
• While also referred to as a through-knee amputation (TKA), that is a more generic term that may or may not include removal of the patella and excision of parts of the condyles, depending on the procedure used.
• This is the least traumatic of the amputation surgeries and can be done under regional or even local anesthesia.
• The thigh muscles are completely preserved, and thus there is no muscular imbalance.
• The stump permits total end weight-bearing, and the bulbous shape permits easy and firm attachment of prosthetic devices. However, as TKAs are less common, prosthetists are less experienced and have to work harder to get a good fit. This had led some to favor excising portions of the condyles, as seen in Figure 11.
• Proprioception, control of prosthesis, and sensation of weight-bearing are superior after TKA compared to more proximal amputations.
• The maintenance of cartilage over the distal femur decreases infection and greatly reduces the possibility of bony overgrowth.
• In cases where there is significant trauma around the knee, the presence of soft tissue injury may preclude the stump from having good, comfortable, scar-free padding that would allow end weight-bearing.
• Failure rates and reamputation rates are higher with TKA than with above-knee amputation.

TKA Surgical Technique

• Multiple variations of the technique are described, with some leaving the patella and some removing it. Additionally, some report excising the bulbous portion of the condyles on the medial, lateral, and posterior aspects (Figure 11).
• The patient is placed in a supine position with access to the hip.
• A sterile tourniquet is applied to the thigh.

• The skin incision is made, with the anterior flap extending to the tibial tuberosity. A posterior flap longer than the anterior flap is made, with the final trimming of the skin delayed until wound closure (Figure 12).
• The knee is flexed, and the distal anterior skin is dissected from the patellar tendon and the tibial tubercle, taking care not to button-hole the skin.
• The patellar tendon is transected at its distal insertion, and the fat pad is incised.
• The knee joint capsule is entered and divided circumferentially just distal to the menisci.
• The hamstrings and collateral ligaments are released from their distal insertions below the knee, preserving as much length as possible.
• The knee is maximally flexed, and the posterior knee capsule is released from the tibia.

• The heads of the gastrocnemius muscles are divided 3 cm below knee level to preserve the blood supply from the superior geniculate artery.
• The major vessels are divided and suture ligated at the level of the knee, and the nerves are ligated and sharply transected while applying gentle distal traction such that the cut ends retract proximally.
• The leg is positioned with the hip extended to avoid creating excessive tightness in the rectus femoris muscle and resultant hip flexion contracture.
• The patellar tendon is further mobilized from the overlying skin, and if retained, the patella is positioned such that the apex is level with the femoral condyles.
• The patellar tendon is then sutured to the cruciate ligaments, as depicted in Figure 13.
• The hamstring (biceps femoris, semimembranosus, and semitendinosus) tendons are also sewn to the cruciate ligaments (Figure 13), with the posterior capsule also sewn to the remaining joint capsule to create a cushioned stump.
• A subcutaneous suction drain may be placed, the skin is trimmed, and a tension-free closure is created with interrupted sutures (Figure 14).
• Care should be taken to avoid skin tension at the suture line and especially over the condyles.

TKA Pitfalls

• Failure to create a posterior flap long enough to cover the stump.
• Incorrect placement of the patella (if retained) can lead to pain and skin breakdown.
• Proper prosthetic fitting is more complicated than other amputation levels, most often due to lack of familiarity with providing devices for this uncommonly performed procedure.
• Failure to make a smooth curve of the posterior incision may result in excess skin and “dog- ears.”

Above-the-Knee (Transfemoral) Amputation (AKA)

AKA Considerations

• While the major goal of AKA is wound healing, the procedure should be done with consideration of biomechanical principles and muscle preservation.
• The energy expenditure for individuals with an AKA is 65 percent or more above normal for level walking at regular speed.
• The longer the residual limb, the greater the functional ability and the better the ability to suspend and align a prosthesis.
• The goal of surgery should be the creation of a dynamically balanced residual limb with good motor control and sensation.

AKA Surgical Technique

• If needed, a sterile tourniquet can be placed as high on the thigh as possible and released prior to setting muscle tension.
• The patient is placed supine with a bump under the hip, and the lower abdomen, hip, thigh, and entire leg are prepped. In the setting of polytrauma, prepping the entire torso and the contralateral leg may be indicated.
• The knee and hip are flexed to 90°, with the limb supported by an assistant.
• For classically described AKA flaps, a pen is utilized to mark a “fish-mouth” incision, with the lateral apex about one hand breadth (10–12 cm) from the upper border of the patella and inferior to the edge of the femur (Figure 15).

• The anterior flap is generally 3–5 cm longer than the posterior flap (Figures 15 and 16) to ensure that the scar is located posteriorly.
• The skin flaps may need to be made longer than initially thought to avoid having to shorten the bone too much.
• Any flap configuration that will enhance feasible preservation of length with adequate soft tissue coverage is acceptable.
• The skin and subcutaneous tissue should be divided circumferentially, and the saphenous vein should be ligated.
• Muscles should not be sectioned until they have been identified.
• The quadriceps should be detached just proximal to the patella to retain some of its tendinous portion.
• The smaller anterior compartment muscles are sharply divided to the bone a few centimeters distal to the planned osteotomy site.
• The periosteal soft tissues are circumferentially cleared with a periosteal elevator (Figure 17).
• The femoral artery and vein are identified under the sartorius muscle (Figure 18) and are individually ligated.
• The adductor magnus is detached from the adductor tubercle and reflected medially to expose the femoral shaft.
• The adductor muscles are divided a few centimeters beyond the proposed osteotomy.
• The femur is exposed above the condylar level and is cut with an oscillating blade or Gigli saw, transecting the femur approximately 7.5–10 cm above the knee joint (Figure 19).
• The sharp edges of the bone are smoothed using a rasp (Figure 20).
• The posterior compartment muscles are divided sharply 2–3 cm distal to the osteotomy site. The sciatic nerve should be ligated and sharply divided as proximally as possible such that it will retract into the muscle compartment.

• The size and shape of the flaps in relationship to the cut end of bone are checked and trimmed if necessary to ensure adequate approximation without tension.
• Hemostasis is ensured, and bone wax is applied to the stump if there is oozing.
• A series of holes (three to six) may be drilled 1 cm proximal to the bone end (Figures 21 and 22) to allow for myodesis (attachment of muscle to bone).
• The number of holes required to provide adequate coverage of the stump is variable, and additional myodesis holes can be added as necessary.
• Myoplasty is performed by bringing the muscles over the femur to provide soft tissue coverage to the residual bone.

• Opposing muscle groups are sewn together (flexor to extensor, abductor to adductor) and anchored to the femur where possible (Figure 23). This should be done with the femur in full extension to minimize contraction.
• The quadriceps is secured to the adductor flap to complete the myoplasty (Figure 24).
• The deep fascia is closed with interrupted absorbable sutures, starting at the midline to avoid any discrepancies between the anterior and posterior flaps. This is followed by continued segmental closure of the more superficial fascia (Figure 25).
• The skin is then closed without tension using interrupted mattress sutures (Figure 26).
• Generally, one or two closed suction drains are left below the flaps and brought out laterally or medially above the suture line.

AKA Pitfalls

• Failure to preserve as much femoral shaft length as possible to improve function and prosthetic fit
• Failure to ensure enough tissue for adequate coverage of the femur.
• Failure to myodese the adductor and medial hamstrings to the bone to prevent muscle slippage over the end of the stump.
• Until the wound is soundly healed, no attempt should be made to apply compression bandaging to mold the stump.

Hip Disarticulation

• Hip disarticulation is the surgical removal of the entire lower limb by transection of the hip joint.
• Hip disarticulation is rarely required or performed but has been more common in the recent wars in Iraq and Afghanistan for hemorrhage control or in cases of massive lower extremity devitalization.
• The basic steps of the procedure are included here for the sake of completeness. It is advisable to seek experienced help if available to perform this procedure.

Hip Disarticulation Surgical Technique

• The patient is placed in a lateral position.
• A racket-shaped incision is made, with its apex medial to the anterior superior iliac spine (Figure 27).
• The incision is marked, and the skin and subcutaneous tissue are divided, with the first steps being to expose the femoral triangle and to identify and individually ligate the femoral neurovascular bundle (Figure 28).

• The muscles of the anterior-medial thigh are identified and divided in a methodical fashion, starting with the sartorius, rectus femoris, and pectineus, which are divided at their origins (Figure 28).
• The iliopsoas muscle tendon is divided at its distal insertion on the lesser trochanter, and the adductor muscles are released from their origins on the pelvis to expose the joint capsule (Figure 29).
• The obturator artery (Figure 29) and nerve are carefully ligated and transected.

• The tensor fasciae latae and gluteus maximus (Figure 30) are divided, leaving sufficient length from their origins to be swung across the empty femoral socket on completion of the hip disarticulation.
• The muscles inserting onto the greater trochanter (gluteus medius and minimus, piriformis, obturator internus and externus, and gemelli muscles) are removed to complete the exposure of the joint capsule, which can then be opened with disarticulation of the femoral head.
• The hamstring muscles are detached from their origin, and the sciatic nerve is identified, ligated, and divided after applying distal traction to allow it to retract up into the remaining tissues.
• This completes the dissection, and the wounds are closely inspected for hemostasis.
• Following removal of the limb, the acetabulum is covered by approximating preserved muscles (Figure 31), with the quadratus femoris approximated to the iliopsoas and the obturator externus to the gluteus.
• The remaining fascia is closed in layers over closed suction drains, and the skin is approximated with interrupted sutures in a tension-free fashion.

Hip Disarticulation Pitfalls

• Hip disarticulation is a radical procedure with obvious implications for limb functionality and carries with it high rates of complications and mortality.
• The best outcomes are achieved with multidisciplinary care, and formal disarticulation should be done with as much experienced help as possible.
• Development of postoperative infection following a hip disarticulation done for trauma is associated with high mortality. As such, it is imperative that adequate debridement be accomplished and optimization of physiology be achieved prior to formal shaping and closure of such wounds.