Rotational mismatch between the femoral and tibial components is reported to be a risk factor for unsuccessful total knee arthroplasty (TKA). However, the rotational mismatch can still occur even when each component is aligned within the desired angle. Therefore, there may be other unknown factors. This study aims to investigate a risk factor for component rotational mismatch in TKA. The authors hypothesized a significant correlation between the rotational mismatch angle and not only the rotational alignments of components, but also the preoperative tibiofemoral rotation angle.
This retrospective cohort study included 79 knees who underwent TKA. Computed tomography images were obtained preoperatively and 2 weeks after surgery for the component positional measurement. The postoperative component rotational mismatch angle between the tibial and femoral components and the rotational alignment of each tibial and femoral component to anatomical axes was evaluated. In addition, the preoperative rotational angle between the tibia and femur bones and patients' demographics were also investigated. The correlation between the postoperative component rotational mismatch angle and perioperative variables was analyzed to identify risk factors for component rotational mismatch.
The mean component rotational mismatch angle was 1.8° of internal rotation of the tibial component relative to the femoral component, and the angle ranged from 11.3° of internal rotation to 7.3° of external rotation of the tibial component. Multivariate regression analysis showed that the preoperative rotational alignment between the tibia and femur and the rotational alignment of each component were influential factors in the postoperative component rotational mismatch angle.
The preoperative tibiofemoral rotational alignment and the rotational alignment of each tibial and femoral component and are risk factors for the postoperative component rotational mismatch in TKA.