What is the risk classification of an above the knee (AK) amputation?

Risk Classification of Above-Knee Amputation

Above-knee amputation is classified as a high-risk surgical procedure due to its significant mortality and morbidity rates.

Risk Classification Evidence

• Above-knee amputation is associated with a 30-day mortality risk of 4% to 30% and a 20% to 37% risk of significant morbidity, including myocardial infarction, stroke, and infection 1
• The overall mortality rate for lower limb amputations has been reported as high as 20.2%, with sepsis being the main cause of death 2
• Recent data shows that above-knee amputation has significantly higher complication rates (37.0%) compared to other salvage procedures like knee arthrodesis (11.5%) 3
• Two-year mortality rate after above-knee amputation can reach 28.3%, with age being an independent risk factor 3

Factors Contributing to High-Risk Classification

Perioperative Risks

• Major amputation of the lower extremity carries substantial perioperative risks including cardiovascular events, infection, and death 1
• Complications requiring further revision surgery occur in up to 37.0% of above-knee amputation patients 3
• Positive intraoperative tissue cultures during above-knee amputation significantly increase the risk of requiring further surgical revision 3

Functional Outcomes

• Functional outcomes after above-knee amputation are generally poor, with studies showing:
  • 47% of patients become non-ambulatory 4
  • Only 28% become home ambulators and 26% community ambulators 4
  • Only a small percentage of patients are successfully fitted with prostheses (45.7%) 3
  • Even when fitted with prostheses, many patients never achieve functional independence 5

Quality of Life Impact

• Above-knee amputation significantly impacts quality of life, with factors associated with poorer outcomes including:
  • Age >65 years 6
  • Presence of diabetes 6
  • Being homebound/isolated 6
  • Persistent phantom pain 4

Clinical Decision Making

• A multidisciplinary care team approach is essential when considering above-knee amputation to assess the most distal level of amputation that facilitates healing and provides maximal functional ability 1, 6
• Primary amputation is indicated when life over limb is the prevailing consideration and the threatened limb is causing patient instability 1, 6
• When amputation is necessary, always aim for the most distal level possible that will heal, as below-knee amputations allow better mobility with a prosthesis 1
• For bedridden patients, above-knee amputation may be the preferred choice despite its higher risk classification 1

Postoperative Management

• Removable rigid dressings are recommended over soft dressings for post-amputation management to allow for regular wound inspection, reduce limb edema, prevent knee flexion contractures, and protect the limb 7, 8
• Regular monitoring of the surgical site for signs of infection is critical given the high complication rates 7

Risk Reduction Strategies

• Male gender, preoperative community ambulatory status, and absence of persistent phantom pain are independent predictors of better ambulation outcomes 4
• Professional-controlled factors that can improve outcomes include optimal timing of amputation, informed decision-making, and comprehensive post-amputation support 6
• Careful patient selection and thorough preoperative assessment are essential to identify those who might benefit from alternative procedures when possible 3