What is the procedure for performing a below knee amputation?

Below Knee Amputation Procedure

Below knee amputation (BKA) should be performed using a team-based approach with preservation of maximal tissue while ensuring a functional limb and optimal healing. 1

Indications for Below Knee Amputation

• BKA is indicated when limb salvage is not possible due to:

  • Advanced soft-tissue infection with sepsis control needed 1
  • Severe metabolic derangements from extensive tissue necrosis 1
  • Failed revascularization with prohibitive pain 1
  • Non-reconstructable vascular disease 1

• When possible, limb salvage should be attempted in hemodynamically stable patients 1

Preoperative Considerations

• Multispecialty care team collaboration is essential for optimal outcomes 1
• Determine optimal level of amputation based on:
  • Presence and extent of infection 1
  • Degree of ischemia and tissue loss 1
  • Potential for healing at the selected level 1
• Consider quality of life factors that influence outcomes:
  • Age (patients >65 years have lower QOL) 1
  • Presence of diabetes (associated with lower QOL) 1
  • Timing of amputation (affects QOL) 1
  • Informed decision-making with patient 1

Surgical Technique

Incision and Flap Design

• Create anterior and posterior flaps with the posterior flap longer than the anterior flap 1
• Ensure adequate soft tissue coverage for the residual limb 1
• Position the incision to avoid weight-bearing areas of the residual limb 1

Bone Management

• Transect the tibia approximately 12-15 cm distal to the knee joint 1
• Bevel the anterior crest of the tibia to prevent sharp edges 1
• Transect the fibula 1-2 cm proximal to the tibial cut 1

Soft Tissue Management

• Identify and individually ligate major vessels (anterior and posterior tibial, peroneal) 1
• Identify, gently pull down, and transect major nerves (tibial, peroneal) to allow retraction to prevent neuroma formation at pressure points 1
• Secure muscle flaps over the distal tibia to provide cushioning 1

Closure

• Close the wound in layers with non-absorbable sutures for skin 1
• Avoid excessive tension on the wound edges 1
• Apply a soft compression dressing or rigid cast depending on wound characteristics 1

Special Considerations

• Autogenous vein grafts provide the best patency results if vascular bypass is needed 1
• Below-knee amputation offers better functional outcomes than above-knee amputation 1
• Prosthetic grafts may be used if autogenous vein is unavailable 1
• Antibiotic prophylaxis should be administered as soon as possible and continued for 48-72 hours in cases of open fractures 1

Postoperative Management

• Implement a plan for management of diabetes and medical comorbidities 1
• Provide postamputation support to improve quality of life 1
• Monitor for wound complications, which are common in patients with peripheral artery disease 1
• Begin early rehabilitation to maximize functional outcomes 1

Common Pitfalls and Complications

• Wound complications and hospital readmission rates are high in patients with chronic limb-threatening ischemia 1
• Risk factors for complications include:
  • Advanced cardiovascular disease 1
  • Diabetes 1
  • Residual infection 1
  • Ongoing smoking 1
• Staged approach to BKA may reduce risk for postamputation complications in selected patients 2

Outcomes

• Below-knee amputations have better functional outcomes compared to above-knee amputations 1, 3
• Walking with prosthesis is associated with higher quality of life 1
• Surgeon specialty may impact outcomes, with orthopedic surgeons having lower complication rates but typically operating on healthier patients 4