[Position of the patella after knee endoprosthesis. A by radiology and computerized tomography controlled study]

The position of the Patellaimplant of 35 total knee arthroplasties (PCA) in regard to the other components, to patellar ligament and to correction of axis was analysed. The position of the patella was investigated with an average follow up of 38 months both radiologically and by computed tomography. A lateralisation of 4 mm on average and a lateral tilting of 4 degrees on average were found. The lateralisation of the patella in 30 and 60 degrees defilee radiographs demonstrated a significant dependence on the correction angle into valgus position. In lateral view and computed tomography the tilting of the patella is also dependent on the length of the ligamentum patellae. To avoid lateralisation and tilting of the patella in case of caudal position of the patella and a high intraoperative degree of correction into valgus position, careful check of the patella position is recommended in order to lateral release or medial capsular shift.