The effect of built-in external femoral rotation on patellofemoral tracking in the genesis II total knee arthroplasty.

External rotation of the femoral component during total knee arthroplasty (TKA) has been suggested to improve flexion space balancing and patellofemoral tracking. Incorporation of external rotation into the design of the femoral component offers an alternative method to achieve this goal. This study compared 150 TKAs performed with traditional external rotation of the femoral component on the distal femur with a similar group of 150 TKAs performed with an implant that incorporates 3 degrees of external rotation into the femoral component. Statistical improvements were noted in the latter group, with respect to the need for intraoperative lateral retinacular release and in postoperative patellar tracking. Incorporation of 3 degrees of external rotation into the design of the femoral component seems to improve the overall result of TKA, especially with respect to patellofemoral resurfacing.