Effect of rotational alignment on patellar tracking in total knee arthroplasty

Forty-four consecutive patients (65 knees) who underwent identical condylar type total knee arthroplasty were evaluated retrospectively. In 22 of the patients (32 knees), the femoral component was set parallel to the posterio r condylar axis (neutrally aligned group). In the remaining 22 patients (33 knees), it was set in an external rotation position of 3 degrees to 5 degr ees relative to the axis (externally aligned group), Of the total knee arth roplasties in the neutrally aligned group, 34% required lateral release, co mpared with only 6% in the externally aligned group; patellar tracking in t he externally aligned group was significantly better than that in the neutr ally aligned group. Postoperative measurements performed using computed tom ography scans showed that the mean angle between the prosthetic posterior c ondylar axis and the transepicondylar axis was 7.9 degrees in the neutrally aligned group and 3.2 degrees in the externally aligned group. The externa l rotation setting of the femoral component diminished the need for lateral retinacular release and may decrease the rate of patellofemoral complicati ons that occur after total knee arthroplasty.