Above-Knee Amputation: Surgical Technique
The American College of Surgeons recommends measuring 12-15 cm proximal to the knee joint line as the standard femoral transection point, creating equal-length anterior and posterior myocutaneous flaps (each approximately 50% of limb circumference), and marking incisions to allow 10-12 cm of soft tissue distal to the planned femoral cut. 1
Pre-Operative Assessment and Planning
Vascular Assessment
- Ensure adequate vascular supply with ankle pressure >50 mmHg or ankle-brachial index (ABI) >0.5 before proceeding 1
- Patients with occluded superficial femoral artery combined with occluded/stenotic deep femoral artery and no palpable femoral pulse require prophylactic inflow revascularization prior to AKA to prevent ascending gangrene 2
- Flat pulse volume recordings at the high thigh level indicate high risk for postoperative stump gangrene and warrant revascularization before amputation 2
Level Selection
- Measure 12-15 cm proximal to the knee joint line for femoral transection 1
- This balances prosthetic fitting requirements with functional limb length 1
- Avoid transecting the femur too proximally, as this significantly impairs prosthetic function and patient mobility 1
Surgical Steps
1. Skin Incision and Flap Design
- Create equal-length anterior and posterior myocutaneous flaps 1
- Each flap should measure approximately 50% of the limb circumference at the level of bone transection 1
- Mark the incision to allow 10-12 cm of soft tissue distal to the planned femoral cut 1
- This ensures adequate coverage without redundancy 1
Critical Pitfall: Avoid creating unequal flaps that result in a "dog ear" deformity or tension on the suture line 1
2. Muscle Division
- Divide muscles circumferentially at appropriate levels to create myocutaneous flaps 1
- Preserve adequate muscle length for flap construction 1
3. Femoral Transection
- Transect the femur at the predetermined level (12-15 cm proximal to knee joint line) 1
- Smooth all bone edges carefully 1
Critical Pitfall: Do not leave sharp bone edges, as these will cause skin breakdown and pain with prosthetic use 1
4. Vessel and Nerve Management
- Ligate major vessels (superficial femoral artery and vein) 1
- Identify and transect the sciatic nerve under gentle traction to allow retraction proximally 1
5. Hemostasis and Closure
- Achieve meticulous hemostasis before closure 1
- Consider tranexamic acid administration to minimize post-operative blood loss 1
- Approximate muscle flaps over the bone end 1
- Close skin without tension 1
Post-Operative Management
Thromboprophylaxis
- Initiate early pharmacological thromboprophylaxis with low molecular weight heparin (LMWH) after hemorrhage control and hemostasis 1
- Start antiplatelet therapy pre-operatively unless contraindicated, continuing indefinitely post-operatively 1
Rehabilitation
- Begin physical therapy early with modifications to avoid excessive stress on the surgical site 1
- Focus on improving residual limb strength, mobility, and preparation for prosthetic fitting 3
High-Risk Situations Requiring Special Consideration
Indications for Prophylactic Revascularization Before AKA
Three situations carry high risk for postoperative stump gangrene (mortality rate 28.5% if gangrene develops) 2:
- Acute thrombosis of a prior combined inflow/outflow procedure 2
- Occlusion of the superficial femoral artery with occluded/stenotic deep femoral artery and no palpable femoral pulse 2
- Flat pulse volume recordings at the high thigh level 2
In these cases, perform inflow revascularization prior to amputation to prevent ascending gangrene, which carries significantly higher mortality (50-100%) compared to standard AKA mortality (2.8%). 2