Below Knee Amputation: Surgical Technique
The optimal below knee amputation technique involves creating a long posterior flap with the tibia transected 12-15 cm distal to the knee joint and the fibula cut 1-2 cm proximal to the tibial level, followed by immediate application of a removable rigid dressing in the operating room. 1, 2
Preoperative Planning
Determine the amputation level based on three critical factors: presence and extent of infection, degree of ischemia and tissue loss, and potential for healing at the selected level. 1 The goal is to preserve maximum tibial length while ensuring adequate soft tissue coverage for optimal prosthetic function. 2
Prioritize life over limb - if the patient is hemodynamically unstable or has life-threatening conditions (severe infection with sepsis, extensive tissue necrosis causing metabolic derangement, or prohibitive pain from failed revascularization), proceed with amputation rather than attempting limb salvage. 3, 1
Surgical Technique: Step-by-Step
Flap Design and Incision
Create anterior and posterior skin flaps with the posterior flap longer than the anterior flap to ensure adequate soft tissue coverage over the residual limb. 1 This long, broad posterior flap design conserves maximum blood supply and has proven safer than equal-length flaps. 4
Mark the incision to allow for a tibial transection approximately 12-15 cm distal to the knee joint. 1
Bone Division
Transect the tibia at 12-15 cm distal to the knee joint, using a saw to create a smooth, beveled anterior edge to prevent pressure points. 1
Cut the fibula 1-2 cm proximal to the tibial cut level to prevent distal fibular prominence that could interfere with prosthetic fitting. 1
Vascular and Nerve Management
Identify and individually ligate all major vessels (anterior tibial, posterior tibial, and peroneal arteries) to prevent hemorrhage and hematoma formation. 1 Consider dividing and ligating vessels distally to maximize blood supply to the flap. 4
Identify major nerves (tibial, common peroneal, sural) and transect them sharply under gentle traction to allow retraction proximally into soft tissue, minimizing neuroma formation and phantom limb pain. 1
Muscle and Soft Tissue Management
Bevel the gastrocnemius and soleus muscles to create adequate padding over the tibial end. 1
Consider de-epithelializing and burying any redundant tissue ("dog ears") at the stump end to provide extra padding rather than excising it. 4
Ensure the posterior flap provides sufficient soft tissue coverage without excessive tension when brought anteriorly over the tibial end. 1
Closure
Approximate muscle layers over the bone end without excessive tension. 1
Close skin in layers, ensuring the suture line is positioned anteriorly rather than directly over the tibial end. 1
Immediate Postoperative Management
Apply a removable rigid dressing (RRD) immediately in the operating room - this is the single most important postoperative decision affecting outcomes. 2 RRDs provide faster healing, reduced edema, prevention of knee flexion contractures, protection from trauma, reduced pain, and earlier prosthetic fitting compared to soft dressings. 2
Never use soft dressings alone as they are inferior for virtually all outcomes. 2
The RRD must allow regular wound inspection, which is critical for patients with ischemic disease at high risk for wound dehiscence. 2
Postoperative Medical Management
Initiate antiplatelet therapy immediately postoperatively and continue indefinitely unless contraindicated, as this improves graft patency and reduces cardiovascular events. 2
Inspect the surgical wound regularly for signs of infection, dehiscence, or hematoma formation. 2
Administer antibiotic prophylaxis for 48-72 hours in contaminated cases. 1
Special Considerations and Pitfalls
High-risk patients including recent smokers, those with bleeding disorders, patients requiring preoperative ventilator use, or those transferred from another facility have significantly increased reoperation rates (up to 9.63% require unplanned reoperation). 5 These patients require enhanced monitoring.
Avoid cutting the tibia too short in an attempt to ensure healing - preserve maximum length while ensuring adequate soft tissue, as longer residual limbs dramatically improve prosthetic function and quality of life. 2
Do not use weight-bearing immediate postoperative prostheses (IPOPs) in ischemic patients due to high risk of wound complications and falls. 2
For staged amputations in severe infection cases, ankle disarticulation can be used as an alternative first-stage procedure, providing rapid infection decompression while minimizing blood loss compared to traditional tibial osteotomy. 6