Atlas of General Surgical Techniques (Courtney M. Townsend Jr., B. Mark Evers)

C H A P T E R 93 • Below-Knee Amputation 1039

Closure of muscles by approximation of investing fascia over tibia

FIGURE 93–9

Assistant aids in closure by approximating skin flaps

Closure of skin with surgical staples or sutures

FIGURE 93–10

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STEP 4: POSTOPERATIVE CARE

Use posterior knee extension splints to keep the knee joint in extension for use in prosthesis (Figure 93-11).

Use “stump shapers” or elastic wraps to shape the amputation stump into a cone shape to facilitate prosthetic socket fitment.

Skin sutures or staples are typically left in place for extended periods of time to allow the wound to adequately heal.

Elastic bandage applied over plastic splint with knee in full extension and tapered to cone shape at tip of stump

FIGURE 93–11

C H A P T E R 93 • Below-Knee Amputation 1041

STEP 5: PEARLS AND PITFALLS

Creation of a posterior flap initially with excess tissue allows the surgeon to trim and tailor the flap, removing redundant tissue and providing adequate soft tissue coverage.

When the patient is ambulating on the below-knee amputation stump, the socket is typically designed to not bear weight on the distal tip of the tibia but to distribute the load over a large area below the knee.

SELECTED REFERENCE

1. Lower-extremity amputation for ischemia. In Wilmore D, Cheung LY, Harken AH, et al (eds): ACS Surgery Principles & Practice. New York, WebMD, 2002, pp 934-956.

C H A P T E R 94

SUPRACONDYLAR AMPUTATION

Jong O. Lee

STEP 1: SURGICAL ANATOMY

A comprehensive understanding of the anatomy of the thigh and knowledge of the preexisting level of circulation is critical before undertaking amputation of the leg.

Figure 94-1 demonstrates key anatomic structures that must be considered with supracondylar amputation, including the relationship of the femur with the surrounding vessels.

STEP 2: PREOPERATIVE CONSIDERATIONS

Select the level of amputation that will optimize healing and preserve as much function as possible.

The indications for supracondylar amputations include the following:

Nonambulatory, debilitated patient with indication for amputation with high risk for developing flexion contracture of the knee after below-knee amputation.

Debilitated patients with knee joint contracture and/or nonviable calf muscle or skin for creation of the below-knee flap.

Failure of a bypass graft.

Failure of below-knee amputation.

Severe ischemia, necrosis, infection, joint contractures, neoplasm, trauma, and crush injuries involving the calf or distal thigh may preclude performing below-knee amputation.

A vascular study should be obtained to determine whether below-knee amputation can be attempted.

Objective evidence that the selected level is one at which primary healing is likely to occur should be established.

The most common level for supracondylar amputation is at the midfemur. Objective evidence that the selected level is one at which primary healing is likely to occur should be established.

Preservation of the length of the femur results in better function.

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STEP 3: OPERATIVE STEPS

1.INCISION

Proper positioning of the patient is supine. A roll can be placed under the thigh to position the leg.

The incision must be carefully planned to allow optimal skin flap for closure. The fish- mouth–shaped incision is made using equal length posterior and anterior flaps. The corners of the fish-mouth incision should be at the level of the amputation of the femur. The length of the flaps should be approximately two thirds of the diameter of the thigh at that level

(Figure 94-2).

The length of the flaps should be sufficient to provide secure, tension-free closure over the femoral stump.

The skin incision is made and extended through the subcutaneous tissue and the fascia over the underlying muscle at the same level of the skin incision. The muscles are divided using electrocautery at least 5 cm distal to the intended site of femur amputation and are allowed to retract.

The anterior femoral muscles are divided first followed by the medial femoral muscles. The posterior femoral muscles are divided last.

A clamp can be used under the muscles to retract them and place them under traction.

The muscle flaps should be longer if myodesis/myoplasty is planned.

2.DISSECTION

As muscles are divided, the nerves and vessels are identified.

The femoral artery and vein are found deep in the anterior medial thigh, lying adjacent to the femur.

The femoral artery and vein are isolated, double clamped, suture ligated, and divided (see Figure 94-1).

The sciatic nerve is identified between the adductor magnus and biceps femoris muscles. The nerve is placed on a gentle traction, ligated proximately, sharply divided, and allowed to retract.

The sciatic nerve contains relatively large arteries and therefore should be ligated.

C H A P T E R 94 • Supracondylar Amputation 1045

Fish-mouth incision of skin and deep tissue

Level of division of femur

FIGURE 94–2

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The femur is divided using a saw.

After anterior muscles are divided, the periosteum of the femur is incised circumferentially and is cleared approximately 2 cm distally. The femur is divided immediately distal to the periosteal incision.

The level of the femur resection is identified by cutting the periosteum, but periosteum should not be stripped from the femur. Stripping periosteum from the femur may result in loss of blood supply to the exposed bone.

The femur is divided at least 3 to 5 cm proximal to the line of skin incision.

The edges of the bone should be rasped to form a smooth contour.

Divided muscles are retracted superiorly for better exposure during resection

(Figure 94-3).

An oscillating power saw or Gigli saw is used to divide the femur (see Figure 94-3).

3. MYODESIS/MYOPLASTY

A long quadriceps flap with its fascia can be sutured to the posterior fascia and major muscle groups.

Several small holes (7⁄64 inch) are placed through the cortex of the distal end of the femur 3⁄8 inch from the distal cut end of the femur. Loop mattress sutures are placed through the major muscle groups and drawn through the holes.

The adductor and hamstring muscles are sutured to and across the end of the femur through the drill holes. The femur is kept in adduction as the adductors are tied down.

The femur should be in full extension as the quadriceps are secured to avoid hip flexion contracture.

Myodesis or myoplasty is performed in a nonischemic limb. It is avoided in ischemic limbs because of increased risk of wound breakdown.

If myodesis is planned, the posterior muscle flaps are left 2 inches longer than the level of bony transection. If both myodesis and myoplasty are planned, all muscle groups are left long.

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4. CLOSING

The wound is irrigated. Once hemostasis is achieved, closure is performed by first approximating the fascias of the anterior and posterior flaps using interrupted 2-0 Vicryl sutures

(Figure 94-4).

If there is persistent oozing, a drain is placed.

The skin edges of the two flaps are approximated with 3-0 nylon sutures in interrupted fashion or with staples (Figure 94-5), which are left in for 3 weeks.

After soft dressings are applied, splints may be applied. To prevent flexion contracture of the hip, pillows are not used for support.

Fascia and muscle are approximated with tension relieved by external compression

FIGURE 94–4