PATELLAR TRACKING: A COMPARISON OF AN IMPLANT WITH A LATERALISED TROCHLEAR GROOVE COMPARED TO A CONVENTIONAL POSTERIOR STABILISED DESIGN

Aim The aim of our study was to assess lateral tracking of the patella with differing designs of Total Knee Arthroplasty (TKA) and compare to that of the native patella. Method A modified caliper was used to measure the width and position of the patella relative to the femur at different degrees of knee flexion. The relationship of the patella midpoint to that of the femur was subsequently assessed. Group 1 consisted of 25 native knees. Group 2 consisted of 25 patients with antero-posterior stabilised knee implant with a spherical medial condyle and a deep lateralised patellar groove, and Group 3 consisted of 25 patients with a conventional cam-and-post design with a midline patellar groove. The mean follow-up was 28 months. Results Lateral tracking corresponded well in all groups, but the mean lateral displacement of the patella in group 2 correlated more closely to that of group 1. At 90 degrees of flexion, the patella was displaced a mean of 7mm laterally in both groups 1 and 2, but a mean of 4mm in group 3. Lateral patellar displacement between groups 1 and 3, and that between groups 2 and 3 were statistically significant (p Conclusion Our results indicate that lateral patellar displacement in group 2 is similar to that of native knees. The lateralised deep patellar groove of the femoral component in group 2 is more able to mimic that of the native femoral sulcus. This intrinsic implant design accommodates the natural tracking of the patella.