What are the steps involved in the management of a patient undergoing an Above-Knee Amputation (AKA)?

Management of Above-Knee Amputation (AKA): Step-by-Step Approach

For patients undergoing above-knee amputation, implement a systematic protocol encompassing pre-operative optimization, precise surgical technique with equal-length myocutaneous flaps, and early post-operative mobilization with rigid dressings to maximize functional outcomes and minimize mortality. 1

Pre-Operative Assessment and Planning

Vascular Assessment

• Confirm adequate vascular supply with ankle pressure >50 mmHg or ankle-brachial index (ABI) >0.5 before proceeding 1
• For patients with acute limb ischemia requiring amputation (Category III), perform amputation as the first procedure when the limb is nonsalvageable (insensate and immobile >6-8 hours) 2
• In cases of acute gangrenous ischemia of a potential AKA stump, consider prophylactic inflow revascularization prior to amputation, as mortality reaches 28.5% without revascularization versus 2.8% with appropriate vascular optimization 3

Level Selection

• Measure 12-15 cm proximal to the knee joint line as the standard femoral transection point 1
• Avoid transecting the femur too proximally, as this significantly impairs prosthetic function and patient mobility 1

Pre-Operative Optimization

• Prescribe pre-operative fluid therapy routinely, as many patients become hypovolaemic before surgery 2
• Implement cardiac output-guided fluid administration to reduce hospital stay and improve outcomes 2
• For high-risk patients (those with limited left ventricular function, valvular heart disease, or undergoing complex procedures), establish invasive blood pressure monitoring and consider central venous pressure monitoring 2

Anesthetic Considerations

• Either regional anesthesia (neuraxial or peripheral nerve block) or general anesthesia are acceptable, as no difference exists in 30-day mortality (11.7% for both) or morbidity outcomes 4
• For patients with significant comorbidities, consider bispectral index monitoring to optimize anesthesia depth and avoid cardiovascular depression 2
• Monitor cerebral oxygen saturation in older patients to reduce postoperative cognitive dysfunction 2

Intra-Operative Management

Surgical Technique

• Create equal-length anterior and posterior myocutaneous flaps, each measuring approximately 50% of the limb circumference at the level of bone transection 1
• Mark incisions to allow 10-12 cm of soft tissue distal to the planned femoral cut for adequate coverage without redundancy 1
• Avoid creating unequal flaps that result in "dog ear" deformity or tension on the suture line 1
• Do not leave sharp bone edges, as these cause skin breakdown and pain with prosthetic use 1

Infection Prevention

• Administer antibiotics within one hour of skin incision following hospital protocols 2

Thromboprophylaxis

• Apply thromboembolism stockings or intermittent compression devices intra-operatively 2
• Administer low molecular weight heparin between 18:00 and 20:00 to minimize bleeding risk related to neuraxial anesthesia during daytime trauma lists 2

Hemostasis and Blood Conservation

• Consider tranexamic acid administration to minimize post-operative blood loss 1
• Use point-of-care hemoglobin analyzers at surgery completion to assess anemia and guide transfusion 2

Pressure Care and Positioning

• Position patients sympathetically to avoid pressure sores and neuropraxia 2
• Take care when removing dressings or diathermy plates due to thin, fragile skin 2

Temperature Management

• Employ active warming strategies throughout surgery and continue postoperatively 2

Fluid Management

• Optimize peri-operative fluid management to reduce morbidity and hospital stay 2
• Avoid intravascular volume depletion, particularly if bone cement is used 2

Post-Operative Management

Immediate Post-Operative Care

• Monitor core temperature routinely 2
• Assess hemoglobin levels to guide transfusion decisions 2

Thromboprophylaxis

• Initiate early pharmacological thromboprophylaxis with low molecular weight heparin after hemorrhage control and hemostasis 1
• Continue thromboembolism stockings or intermittent compression devices 2

Cardiovascular Protection

• Start antiplatelet therapy pre-operatively unless contraindicated, continuing indefinitely post-operatively 1

Pain Management

• Continue regular paracetamol administration throughout the peri-operative period 2
• Use non-steroidal anti-inflammatory drugs with extreme caution; they are contraindicated in patients with renal dysfunction 2
• For patients with renal dysfunction, avoid oral opioids and reduce both dose and frequency of intravenous opioids by half 2
• Do not administer codeine, as it causes constipation, emesis, and postoperative cognitive dysfunction 2

Wound Management and Dressing Selection

• Apply non-weight bearing removable rigid dressings (RRDs) as first-line treatment for post-operative care 2
• RRDs provide faster healing times, reduced limb edema, preparatory contouring for prosthetic use, prevention of knee flexion contractures, and reduced external trauma compared to soft dressings 2
• RRDs permit regular wound inspection with greater ease than traditional approaches, critical for the 82% of patients receiving amputation for ischemic disease who are at high risk of wound dehiscence 2

Early Mobilization

• Begin physical therapy early with modifications to avoid excessive stress on the surgical site 1
• Expedited mobilization reduces the risk of deep vein thrombosis 2

Prognostic Considerations

Functional Outcomes

• Among AKA patients, 45% achieve good functional outcome (living at home and ambulating independently) at 1 year, compared to 55% for below-knee amputation 5
• Patients most likely to remain ambulatory are those living at home preoperatively and those with preoperative statin use 5
• Patients with coronary disease, dialysis dependence, or congestive heart failure are less likely to achieve good functional outcomes 5

Mortality Risk

• The 5-year mortality rate after AKA for prosthetic joint infection is 50% 6
• Severe comorbidities, alcohol abuse, and preoperative anemia are associated with higher risk of requiring AKA 7
• All patients requiring AKA should have anemia addressed preoperatively, as it is well amenable to therapeutic measures and associated with worse outcomes 7

Prosthetic Fitting

• Among survivors, 86% are fit for prosthesis following AKA, though only 7% report functional independence with their prosthesis 6
• Despite low independence levels, 86% of patients report satisfaction with their AKA and 42% would have chosen it sooner if offered 6

Critical Pitfalls to Avoid

• Never delay amputation in patients with Category III acute limb ischemia (insensate and immobile limb), as reperfusion of ischemic metabolites can result in multiorgan failure and cardiovascular collapse 2
• Never perform revascularization on a frankly necrotic amputation stump, as mortality reaches 60% in this scenario 3
• Never create unequal flaps or leave sharp bone edges 1
• Never use codeine for pain management 2
• Never apply soft dressings alone when removable rigid dressings are available 2