Rotational alignment of the native knee joint using magnetic resonance imaging compared to current optimal angles in...

Rotational malalignment is a key contributing factor to poor patient satisfaction following total knee replacement (TKR). Currently accepted target points may not be optimal for all patients. The aim of this study was to assess rotational alignment of native knee joints using magnetic resonance imaging (MRI).

The rotational alignment in native knee joints is different to current published optimal angles of rotation in TKR and different anthropological measurements affect this rotation.

Radiological cohort study evaluating MRI scans of native knee joints. A total of twelve rotational angle measurements of the distal femur and proximal tibia were analysed and compared with currently accepted values in TKR.

A total of 100 patients were evaluated. The posterior condylar angle (PCA) (mean 2.3°; range -3.1° to 5.8°) was significantly different to the conventional 3° used in TKR (p < 0.001), and was also significantly different between males (1.2°) and females (3.4°) (p < 0.001). There were also significant gender differences in the condylar twist angle (CTA) (p < 0.001) and the angle between Whiteside's line and the posterior condylar femoral line (PCFL) (p = 0.014). Height was inversely correlated with PCA (r = -0.46, p < 0.001), CTA (r = -0.37, p < 0.001) and the angle between Whiteside's line and PCFL (r = -0.32, p = 0.001). Conversely, height was directly correlated with the angle between the surgical transepicondylar axis (sTEA) and the posterior tibial condylar axis (PTCA) (r = 0.28, p = 0.005), and between the anatomical transepicondylar axis (aTEA) and the PTCA (r = 0.23, p = 0.024).

There were significant differences between rotational alignment of the native knee joint and the values considered optimal in TKR. Gender differences and significant correlations with anthropometric data highlight the need for a more tailored and individualised approach to rotational alignment in TKR.