Effects of Femoral Lateral Bowing on Coronal Alignment and Component Position after Total Knee Arthroplasty: A Comparison of Conventional and Navigation-Assisted Surgery

Purpose To evaluate the effects of femoral lateral bowing on coronal alignment after total knee arthroplasty (TKA) and examine whether the use of navigation helps obtain better postoperative coronal alignment and component position. Materials and Methods Radiological results and outlier rates were compared between the conventional TKA group and the navigation-assisted TKA group, and factors associated with postoperative alignment were evaluated. For clinical assessment, patient-reported outcomes were used. Results A total of 297 knees were retrospectively reviewed. Among the patients with femoral lateral bowing, a significant difference was observed between the conventional TKA group (n=72) and the navigation-assisted TKA group (n=96) in postoperative mechanical femorotibial angle (mFTA, 1.6° vs. 0.8°; p=0.005) and femoral component alignment angle (89.0° vs 90.0°; p=0.017). Preoperative mFTA (p＜0.001), femoral bowing angle (p<0.001), and mechanical lateral distal femoral angle (p=0.032) had effects on postoperative mFTA in the conventional TKA group. In the navigation-assisted TKA group, only preoperative mFTA (p<0.001) had effects on postoperative mFTA. Conclusions Despite the individualized determination of the valgus correction angle through preoperative planning, in the cases with severe lateral bowing, the outlier rate was higher in the conventional TKA group than in the navigation-assisted TKA group. However, there was no significant difference in the clinical results between the two groups in the short-term follow-up.