Chapter 39. Below- and Above-the-Knee Amputation

Below‐the-Knee Amputation (BKA)

• Nonsalvageable lower extremity infection.
• Chronic nonhealing lower extremity wounds.
• Acute lower extremity infection.
• Trauma with vascular or neurologic injury; open tibia fracture with posterior tibial nerve disruption or warm ischemia > 6 hours.

Above‐the-Knee Amputation (AKA)

• Severe peripheral vascular disease not amenable to bypass graft with popliteal pressures inadequate to heal BKA.
• Chronic nonhealing BKA wound.
• Nonreconstructible traumatic injury to the lower extremity involving the knee joint or proximal tibia.

Below‐the-Knee Amputation

• Cardiopulmonary disease and inability to tolerate surgery (relative contraindications).
• Fixed knee contracture that would cause pressure on the distal stump after amputation (AKA is indicated in these cases).
• Nonfunctional limbs (an indication for AKA).
• Paraplegia (relative contraindication).
• Infection that extends above the knee.
• Inadequate blood flow to heal a BKA (popliteal artery pressures < 50 mm Hg).

Above‐the-Knee Amputation

• Aortoiliac occlusive disease with inadequate femoral artery flow to heal an AKA wound.
• Osteomyelitis of the proximal femur, femoral head, or acetabulum.
• Cardiopulmonary disease and inability to tolerate surgery (relative contraindications).

• For either BKA or AKA, the patient should be supine.

Wound Care

• Most surgeons keep the initial dressing in place for 2 days before examining the wound.
• For both AKA and BKA, the lower extremity stump must be kept strictly elevated at all times to reduce edema.

Medical Management

• A patient-controlled analgesia pump is often used for postoperative pain.
• Perioperative tight glucose control is essential to decrease the risk of wound infection and optimize healing.
• Due to concomitant cardiovascular disease in many patients undergoing amputation, perioperative aspirin, statins, and β-blockers should be continued.
• Patients should be closely monitored for symptoms of cardiac ischemia.

Rehabilitation

• Early physical therapy consultation is required to initiate teaching of transfers and one-legged mobility.
• If not consulted preoperatively, the Physical Medicine and Rehabilitation service should be consulted after amputation is completed.
• With BKA, the patient should be monitored closely for any evidence of flexion contracture at the knee.
  • If contracture is developing, a posterior splint can be used to keep the knee straight.
• Some surgeons prefer to use a rigid removal cast dressing in the initial postoperative period to protect the stump and help prevent flexion contracture.
• The patient should remain non-weight bearing on the amputated extremity for a minimum of 3 months.
• A prosthesis may be fit at 6 weeks but should not be used until all wounds have completely healed.

• Delayed wound healing.
  • May occur during the first few postoperative weeks secondary to persistent infection or poor vascular inflow.
  • Often managed with antibiotics when indicated and local wound care but can require surgical debridement, revision, or higher amputation
• Hematomas.
  • Should be drained to prevent future infection.
• Joint contractures ...