Yearly changes of limb alignment toward varus as measured by the femorotibial angle after total knee arthroplasty.

Total knee arthroplasty was performed in 126 knees of 104 patients, using either the UCI, the Kinematic Anteriorly Joined (K-AJ), or the Kinematic Posterior Cruciate Retention (K-PCR) prosthesis. The average patient age at the time of surgery was 59 years; the average follow-up period was 3.3 years. The UCI device was used in 25 knees, the K-AJ in 75, and the K-PCR in 26. Postoperatively, the femorotibial angle was measured yearly for a period of at least six years on an anteroposterior radiograph of the patient standing on one leg. The cases with the UCI prosthesis, with an average standing FTA of 175 degrees one year postoperatively, showed a gradual change of limb alignment toward varus. In contrast, in the cases with the K-AJ and K-PCR prostheses, with an average standing FTA of 172 degrees one year after surgery, limb alignment remained essentially unchanged throughout a long period of follow-up. The authors recommend that total knee arthroplasty be performed to achieve a postoperative femorotibial angle (standing) as close to 172 degrees as possible, which allows the mechanical axis of the lower extremity to pass through the center of the knee.