Aligning the tibial component with medial border of the tibial tubercle--is it always right?

Correct rotational alignment of the tibial component is crucial for total knee arthroplasty (TKA). Several studies have indicated that the best rotational orientation of the tibial component is close to the medial border of the tibial tubercle. However, it remains obscure whether it is always right. Thus, the objective of current study was to quantify tibial rotational alignment in 120 primary rotating platform TKAs using the medial border of tibial tubercle as a landmark between July 2008 and June 2010.

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° of the mean.

The mean divergence external to the medial border of the tubercle was 2.3°±3.5°. However, six of the knees (5%) had neutral points≥10° from the mean, including two valgus knees measured 10° of internal rotation and four varus knees measured 10° 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.