Robotic-arm Assisted Total Knee Arthroplasty Achieves More Symmetrical Medio-lateral Balance Without Significant Clinical Differences in the Short-term

Introduction With the advent of robotic-arm assisted total knee arthroplasty (TKA), a different approach known as the functional alignment (FA) has been newly suggested. Studies have shown that FA can achieve better functional outcomes compared to conventional mechanical alignment (MA). However, its impact on gait is yet unclear. The purpose of the study was to compare the gait profiles between TKAs performed under MA or FA. Methods A retrospective analysis on prospectively collected data in a single, tertiary institute was performed. 64 TKAs (22 robotic-arm assisted functionally aligned RoFA, 22 robotic-arm assisted mechanically aligned RoMA, and 20 manually performed mechanically aligned ManMA) performed using a single type of prosthesis were selected for analysis. Gait analysis and clinical scores (WOMAC and Forgotten joint score FJS) were compared between the groups until postoperative one year. Results Gait speed increased in most of the patients although it was not significant for the RoMA group. The magnitude of knee motion in the coronal plane (represented by the varus-valgus arc angle) decreased for all three groups postoperatively. The varus-valgus arc angle, although significantly reduced from before surgery, was the highest for ManMA group postoperatively (3.7 ±1.4°, p= 0.048). Postoperative WOMAC scores and FJS did not differ between the groups. Conclusion Robotic-arm assisted TKA led to lower knee varus-valgus arc angle in comparison to manually performed TKAs, suggesting more symmetrical medio-lateral balance. However, this difference was not associated with short-term clinical outcomes. There were no significant gait differences between functionally aligned and mechanically aligned TKAs.