Amputation of the Lower Extremity: Above-Knee Amputation, Below-Knee Amputation, Through-Knee Amputation
Jason T. Lee
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Approximately 1.7 million Americans are living with the loss of a limb, and this number is expected to nearly double by 2050.1
Amputations of the lower extremity may be performed for a myriad of reasons including infection, trauma, cancer, and pain.
Thoughtful patient selection, early involvement of neuropsychiatry, and physical medicine and rehabilitation (PM&R) are fundamental to a successful outcome.
Before considering an amputation, the patient should be evaluated by vascular surgery to ensure no other options (endovascular or open) exist.
Patients who are suited for an above-knee amputation (AKA) include those who have limited or no mobility, a nonfunctional limb, infection that has progressed above the knee, inadequate overlying skin/muscle to provide stump coverage, and those patients who do not have adequate blood flow to heal a below-knee amputation (BKA) incision (popliteal pressures less than 50 mm Hg).
BKA is suited in patients who wish to ambulate with a prosthesis, do not have extensive infection above the knee joint, and have popliteal pressures greater than 50 mm Hg to heal the stump.
Knee disarticulations (through-knee amputations) represent less than 2% of all amputations and are typically performed for trauma; they are best suited for patients who are unlikely to ambulate.
AKA is also suitable for patients unlikely to ambulate, but cannot be performed in patients with inadequate femoral artery blood flow as the AKA stump will not heal.
Severe infection that involves the femoral head or proximal femur also preclude AKA.2
All patients undergoing an amputation should be evaluated early by both neuropsychiatry and PM&R.
Thorough physical exam and arterial pressures should be used to determine which level (AKA or BKA) is best for the patient (FIG 1).
Cardiac optimization is important given the high incidence of cardiac disease among this patient population.
If discussing limb viability status post trauma, a multidisciplinary approach involving vascular, orthopedic, and plastic surgery services should take place prior to proceeding with amputation.
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