Improved femoral component rotation in total knee arthroplasty: an anatomical study with optimized gap balancing

Surgically balanced total knee arthroplasties have shown improved functional and clinical outcomes. Two different alignment methods have been proposed, the measured resection technique which uses femoral landmarks on the one hand and the ligament balanced technique which uses spreaders on the other. As anatomical landmarks also vary widely, with regards to the tibial cut irrespective of the collateral ligaments, we hypothesized that anatomical landmarks are not suitable for ideal femoral component rotational alignment.

Ten cadaveric bilateral knees underwent TKA using a navigational device and a double tensiometer. By means of the navigational device, flexion gaps were balanced by femoral component size, rotation and flexion until a symmetric flexion and extension gap was obtained. Acquired femoral component rotation was compared to femoral landmarks (Whiteside Line, posterior condylar line and trans-epicondylar line).

Using the Whiteside line, the posterior condylar line and the surgical trans-epicondylar line to identify femoral component rotation did not balance the flexion gap as well as navigation. Depending on the parameter, deviations in femoral rotation of up to 6° were observed compared to the gap balancing technique. Furthermore, large deviations between these landmarks were observed.

Based on this study flexion gap balancing can be better optimized using ligament balancing technique. As this technique is highly dependent on the proximal tibial cut, we do recommend the use of navigational devices, which additionally assure a neutral leg alignment.