Purpose: The rotational alignment of the femoral and tibial components is closely related to the results after total knee arthroplasty (TKA). In this study, we measured the combined rotational alignment change (ΔCR) after TKA and compared the different influence of symmetric and asymmetric tibial component designs on the combined rotational alignment.
Materials and methods: Eighty-four patients (mean age, 67.9 years) were included. A symmetric tibial component was used in 51 knees (group I), whereas an asymmetric tibial component was used in 50 knees (group II). We measured the angles of four anatomical landmarks by using preoperative and postoperative computed tomography images. The combined rotational alignment and the amount of change were calculated. The correlation between the isolated tibial component rotation (ITR) and ΔCR was analyzed by using the Spearman correlation coefficient.
Results: The mean ΔCR was -0.1°±6.3° in group I and -4.8°±5.7° in group II after TKA. Excluding the intercomponent rotation, the change was -1.0°±7.3° and -6.7°±6.7° in group I and group II, respectively. A correlation analysis between the ITR and tibial component rotation relative to the tibial tuberosity showed a statistically significant correlation.
Conclusions: The combined lower limb rotational alignment was internally rotated in both symmetric and asymmetric tibial component designs after TKA. The asymmetric tibial component was better than the symmetric tibial component in achieving internally rotated combined lower limb rotational alignment. The internal rotation of the symmetric tibial component relative to the tibial tuberosity tip should fall within 20° to correct the externally deformed lower limb.
Keywords: Arthroplasty; Knee; Rotation; Tibia.