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Effect of femoral and tibial component position on patellar tracking following total knee arthroplasty: 10-year follow-up of Miller-Galante I knees.

Rotational alignment of the femoral and tibial components using computed tomography (CT) was evaluated to establish if errors of alignment have a significant effect on patellofemoral complications. From 1987-1990, 54 knees in 39 patients were replaced with the Miller-Galante I knee system. Of these, 10 patients (13 knees) comprised this study. All patients had osteoarthritis. Mean patient age at surgery was 70.3 years. Mean follow-up was 10.3 years. On CT, rotational position of the femoral component relative to the epicondylar axis and the position of the tibial component relative to the tibial tubercle were evaluated. Patellar displacement and patellar tilt angle also were evaluated when the knee was flexed at 30 degrees. Mean rotation of the femoral component was 6.1 degrees of internal rotation (2.7 degrees-11.2 degrees). Mean rotation of the tibial component was 16.7 degrees of internal rotation (2.4 degrees-27.7 degrees). Mean lateral patellar tilt angle was 2.9 degrees (-6.0 degrees-11.9 degrees), and mean lateral displacement was 2.7 mm (-3.2-8.9 mm). Rotational position of both the femoral and tibial components showed a statistically significant correlation with the patellar tilt angle. This study showed the internally rotated femoral and tibial component were related to the patellar maltracking. This malalignment of the components, as well as nonanatomical patellar groove and metal-backed patellar component, could be one of the causes of the patellofemoral complications with the Miller-Galante I knee.