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).

Potential Risks

• Nonhealing wound.
• Phantom pain.
• Chronic pain.
• Neuroma.
• Persistent infection.
• Need for higher amputation.
• Loss of mobility.
• Bleeding requiring transfusion.
• Complications related to general medical condition, including heart attack, stroke, venous thromboembolism, or death.

• Tourniquet.
• Electrocautery and surgical ties for hemostatic control.
• Bone-cutting saw (either a powered oscillating saw or Gigli saw).
• Bone rasp.
• Amputation knife.
• Standard vascular and soft tissue instruments.

• Ankle-brachial index studies (if applicable) and segmental arterial pressures of the lower limb.
  • Popliteal artery pressure of 50 mm Hg is generally considered adequate to heal a BKA.
• Full vascular evaluation for possible salvage procedures, including angioplasty, stenting, or vascular bypass (see Figure 39–1).
• Full medical evaluation (given the high incidence of cardiac disease among patients).
  • Consider cardiac optimization with aspirin, a statin, and a β-blocker as tolerated.
• Preoperative Physical Medicine and Rehabilitation Amputee service consultation.
• Preoperative anesthesia consultation for spinal or regional block.
• Discussion among orthopedic, vascular, and plastic surgery services regarding limb viability in patients with traumatic injury.
• Preoperative type and crossmatch, as appropriate.

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

• Figure 39–1: Vascular anatomy of the lower extremity, showing locations for skin incision and femoral and tibial transection.

Below‐the-Knee Amputation

• General, epidural, or long-acting spinal anesthesia may be used.
• The entire leg is prepared circumferentially to the level of the proximal thigh; open wounds should be prepared with povidone-iodine.
• A sterile thigh tourniquet is applied.
  • Caveat: a tourniquet should not be used in patients with severe vascular occlusive disease.
• The distal foot is covered with stockinette or Ioban antimicrobial drape ...