Influence of the position of the fibular head after implantation of a total knee prosthesis on femorotibial rotation.

A gold standard for the correct rotation of the tibial component has not been established in total knee arthroplasty (TKA). The target parameter of correct rotation is the facilitation of femorotibial rotation over the entire range of motion with no implant overhang. Although the origin of the lateral collateral ligament is a recognized landmark for determining the rotation of the femoral component (epicondylar axis), the attachment of the lateral collateral ligament has not been taken into consideration for adjusting tibial rotation until now. The objective of the current investigation was to examine whether the position of the fibular head, as the attachment of the lateral collateral ligament, influences femorotibial rotation. Seventy patients who underwent TKA were enrolled in this retrospective study. Computed tomography (CT) of the operated knee was performed 6 months postoperatively in all cases and the position of the lateral facet of the fibular head and the tibial tuberosity, and the geometric center of the tibia and the femoral epicondyles were determined. The angle between the lateral facet of the fibular head, the geometric center of the tibia, and the tibial tuberosity was 45.7°±6.9°. The angle between the surgical epicondylar axis and the line from tibial tuberosity to tibial center was 69°±8.3°. This close correlation (R=.73; P<.001) shows that the position of the fibular head determines femorotibial rotation. The fibular head may become a helpful landmark for establishing the rotation of the tibial component; it could be useful in interpretation of postoperative CT scans in knees suspected of tibial malrotation.