Femoral component rotation in patients with leg axis deviation.

PURPOSE: Correct alignment of the rotation of the femoral component and the flexion gap after total knee arthroplasty is difficult in patients with preoperative leg axis deviation. Inaccuracy may result in problems with the patellofemoral joint and instability, in particular. We examined the influence of the preoperative leg axis on the rotation of the femoral component and the symmetry of the flexion gap after total knee arthroplasty using the tibial-cut-first technique. METHODS: A retrospective study was carried out of 58 consecutive patients who underwent primary LCS total knee arthroplasty using the tibial-cut-first technique in 2008 based on preoperative full-leg radiographs and the final radiographs taken according to Kanekasu's technique. The patients were divided into three groups (varus-valgus-neutral) according to their preoperative leg axis. RESULTS: Using the tibial-cut-first technique, a mean neutral rotation of the femoral component of 0.5° and a mean symmetrical flexion gap of -0.7° were achieved. Nevertheless, there was a positive correlation of the preoperative leg axis with the rotation of the femoral component. The differences in the rotation of the femoral component and the flexion gap between the three groups were not significant. The only significant difference between the varus and valgus groups was the extent of rotation of the femoral component, with a slightly greater external rotation of 2.7° in the valgus group. CONCLUSIONS: This study suggests that it is possible to achieve correct rotational alignment of the femoral component and a symmetrical flexion gap using the tibial-cut-first technique in patients with a preoperatively deviated leg axis.

Femoral component rotation and Laurin angle after total knee arthroplasty.

One of the main problems after total knee arthroplasty is pain in the patellofemoral joint, which in some cases leads to revision surgery. Rotation of the femoral component has a significant influence on the path followed by the patella within the patellofemoral joint. We examined the influence of rotation of the femoral component after total knee arthroplasty on patellar tilt. We retrospectively analysed the radiographs of 48 patients who underwent primary LCS total knee arthroplasty without patella resurfacing and without lateral release. Rotation of the femoral component was determined using Kanekasu's technique and patellar tilt assessment according to Laurin on Merchant's views. This radiographic study confirmed a highly significant correlation between external rotation of the femoral component and a decrease in patellar tilt following TKA. Furthermore, we found a highly significant correlation between pre- and postoperative patellar tilt angle.