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Through-Knee Amputation Preserves Independent Ambulation

Magdiel Trinidad-Hernandez, MD, Connie Ryjewski, RN, Norton M. Flanagan, MD, Giohn Lee, MD, Amy Sun, MD, Gregory D. Caldwell and John V. White, MD
University of Illinois College of Medicine/Metropolitan Group Hospitals, Chicago, IL and Advocate Lutheran General Hospital, Park Ridge, IL

Introduction: Preserving independent ambulation in patients with untreatable leg ischemia is problematic, epecially when a below-knee (BKA) amputation is not possible. Above-knee amputations (AKA) are associated with a high mortality risk (>15%), high wound complication rate (9%), and reduced likelihood of independent ambulation, particularly in the elderly and frail. The lower ambulation rate is due to loss of muscle strength and lever arm advantage from femur shortening.
Through-knee amputation (TKA) has many advantages, such as preservation of thigh muscle, minimal femoral shortening, and suitability for prosthesis with efficient knee joints.
Objective: To determine if TKA could replace AKA as the procedure of choice for patients who were not candidates for BKA. Morbidity, mortality, and ability to ambulate compared to pre-operative assessment of likelihood were evaluated.
Methods: Patients who met criteria for AKA (untreatable distal arterial disease, popliteal pressure<50mmHg) were treated with TKA. Inflow problems were treated before or during amputation. Before surgery, the patient’s aptness for independent ambulation with prosthesis was determined by assessment of cardiac status, pre-admission ambulatory status, pulmonary status, and other co-morbidities. Eligible patients entered a rehabilitation program when wound healing permitted. Post-operative ambulatory status was determined by successful completion of the rehab program.
The Kappa coefficient test was used to analyze concordance between the pre-operative assessment and postoperative ambulatory status. A forward stepwise logistic regression method was utilized to seek factors predictive of postoperative ambulatory status.
Results: Twenty-four TKA were performed in 23 patients. The mean age was 74.96 years, 70% were men, 52% were diabetic, 61% had hypertension, 22% had end-stage renal disease, and 43% had a smoking history. Of the 23 patients 61% had failed grafts. Distal infection was present in 12 of 24 limbs pre-operatively, 2 had popliteal fossa abscesses (PFA). There were no operative deaths. The 30-day mortality was 9%. Complications included DVT in 9%, pulmonary in 9%, cardiac in 9%, renal in 4%, infectious in 9%, and depression in 4%. Three patients (13%) including 2 with PFA, had a revision of skin flaps or femoral condyle without conversion to AKA. All 12 patients who ambulated pre-operatively could walk with a prosthesis post-amputation. Pre-operative ambulatory status was the sole predictor of post-operative independent ambulation (k= 0.911 p=0.00) as confirmed by forward stepwise logistic regression analysis (p=0.001).
Conclusion: For patients with untreatable leg ischemia requiring amputation, TKA is associated with low morbidity and mortality and a high likelihood of preservation of independent ambulation. TKA should be the procedure of choice for those who are not candidates for BKA.