What are the recommended steps for performing a below‑knee amputation (BKA), including pre‑operative evaluation, surgical technique, and post‑operative care?

Below-Knee Amputation: Recommended Steps

The most critical decision in BKA management is immediate application of a removable rigid dressing (RRD) in the operating room, which is superior to soft dressings for virtually all outcomes including healing time, edema control, contracture prevention, and earlier prosthetic fitting. 1, 2

Pre-Operative Evaluation

Determine the most distal amputation level that will heal while maximizing functional ability through multispecialty team evaluation. 2 Below-knee amputation offers dramatically better functional outcomes and quality of life compared to above-knee amputation due to preservation of the knee joint. 2

• Confirm adequate vascular supply with objective testing such as xenon-133 clearance, which has demonstrated 100% accuracy in predicting healing of the last 30 BKAs in published series. 3
• Consider primary amputation only when life-threatening instability exists, such as severe infection with systemic sepsis, metabolic derangement, or ischemia causing systemic compromise. 2
• Evaluate patient factors including diabetes (associated with 39% five-year survival vs 75% in non-diabetics), peripheral arterial disease (PAD patients progressing to stump complications universally required conversion to above-knee amputation), and pre-operative ambulatory status. 3, 4, 5

Surgical Technique

Preserve maximum tibial length while ensuring adequate soft tissue padding, as longer residual limbs directly improve prosthetic function and patient mobility. 2 The goal is to balance maximal bone length with sufficient soft tissue coverage to prevent wound complications.

• Create myocutaneous flaps with adequate length to cover the tibial stump without tension—typically requiring 10-12 cm of soft tissue distal to the planned tibial cut. 2
• Perform precise surgical technique including beveling of the anterior tibial crest, adequate myodesis or myoplasty for soft tissue stabilization, and careful hemostasis. 3
• Avoid cutting the tibia too short in an overly conservative attempt to ensure healing, as this significantly impairs prosthetic function. 2

Immediate Post-Operative Management

Apply a removable rigid dressing (RRD) immediately in the operating room rather than soft dressings—this is the single most important post-operative decision affecting outcomes. 1, 2 The evidence supporting RRDs over soft dressings is universal across 15 published studies including 5 level I randomized controlled trials. 1

Benefits of RRDs include:

• Faster healing times and reduced time to prosthetic fitting (51 days to preparatory prosthesis vs 247 days with standard care). 1, 2, 4, 5
• Reduced limb edema and preparatory contouring of the residual limb for prosthetic fitting. 1, 2
• Prevention of knee flexion contractures through splinting the knee in extension. 1, 2
• Protection from external trauma and falls (10.8% fall rate with IPOP vs 21.4% with soft dressings). 1, 2, 4
• Reduced pain compared to soft dressings alone. 1, 2
• Regular wound inspection capability, which is critical for the 82% of patients with ischemic disease at high risk for wound dehiscence. 1, 2

Critical Distinction on Weight-Bearing:

Do not use weight-bearing immediate post-operative prostheses (IPOPs) in ischemic patients due to high risk of wound complications, falls, and inconsistent pressure on the surgical wound. 1, 2 Weight-bearing IPOPs are reserved almost exclusively for trauma patients without vascular or neurologic impairment. 1

Post-Operative Medical Management

Initiate antiplatelet therapy immediately post-operatively and continue indefinitely unless contraindicated, as this improves graft patency and reduces cardiovascular events. 1, 2

• Inspect the surgical wound regularly for signs of infection, wound dehiscence, or hematoma formation—the removable nature of RRDs facilitates this critical monitoring. 1, 2
• For major stump complications (operative infection or dehiscence), employ staged operative debridement for source control, negative pressure wound therapy, and reformalization rather than immediate conversion to above-knee amputation. 5 This approach achieved 100% BKA salvage in non-PAD patients. 5

Rehabilitation and Prosthetic Fitting

Begin early ambulation and rehabilitation on post-operative day 1 when using appropriate rigid dressing systems, which provides significant physiologic and psychological benefit. 4

• Reduce time to prosthetic fitting through use of RRDs, which decrease edema and prepare the limb for casting—optimal prosthetic fitting occurs when edema is controlled and the residual limb is properly shaped. 1, 2
• Expect 100% prosthetic rehabilitation in appropriately selected patients using this comprehensive approach, with 75% of patients remaining independently ambulatory on prostheses at five years. 3

Common Pitfalls to Avoid

• Never use soft dressings alone—they are inferior to rigid dressings for virtually all outcomes including healing time, edema control, contracture prevention, pain, and time to prosthetic fitting. 1, 2
• Avoid cutting the tibia too short in an overly conservative attempt to ensure healing—preserve maximum length while ensuring adequate soft tissue coverage. 2
• Do not use weight-bearing IPOPs in ischemic patients (82% of amputation patients) due to high risk of wound dehiscence and falls. 1, 2
• Do not delay antiplatelet therapy in the post-operative period unless specific contraindications exist. 1, 2
• Recognize that patients with PAD and major stump complications have universally poor outcomes—all patients progressing to above-knee amputation in one series had PAD, while none without PAD required conversion. 5