The femoral component was positioned parallel to the transepicondlylar axis, and a rotating platform trial insert was used to determine tibial insert rotational alignment relative to the most medial aspect of the tibial tubercle with the knee in full extension. Rotational alignment of the components was detected based on radiograph and CT scan. This investigation is based on the premise that all neutral points would lie within 10掳 of the mean.
The mean divergence external to the medial border of the tubercle was 2.3掳 卤 3.5掳. However, six of the knees (5%) had neutral points 鈮?#xA0;10掳 from the mean, including two valgus knees measured 10掳 of internal rotation and four varus knees measured 10掳 of external rotation.
Using the medial border of tibial tubercle as a landmark does not always result in a good femoro-tibial rotational alignment. Surgeons using fixed bearings component should be aware of this effect to avoid suboptimal outcomes resulting from tibiofemoral rotational malalignment in full extension.
Diagnostic study, Level II-3.