Rotational Alignment of the Femoral Component in Computer-Assisted Total Knee Arthroplasty

This study compared two Computer Assisted Surgery (CAS) methods in 212 total knee arthroplasties to evaluate the differences between anatomic landmark axes in determining rotational position of the femoral component. Overall, there were large variations between CAS defined component orientation using an optimized gap-balancing technique and component orientation using anatomic reference axes (range, 16o internal rotation to 16o external rotation). If based on anatomic landmarks, these large variations would have led to asymmetrical flexion gaps in up to 60% of the knees studied. Of the anatomic axes studied, the posterior condylar axis was the only axis not significantly different from CAS optimized orientation. If anatomic landmarks are used for femoral component rotation with either a conventional or a CAS technique, asymmetric trapezoidal flexion gaps may result.