Surgical dominance and alignment accuracy: Do sides matter in bilateral total knee arthroplasty?

In simultaneous bilateral total knee arthroplasty (TKA), the effect of surgical side dominance on mechanical alignment and its clinical implications remains uncertain. This study aims to evaluate whether radiographic alignment differs between sides and whether such differences influence functional outcomes.

89 patients (178 knees) who underwent same-day bilateral TKA were prospectively assessed at a minimum of two years postoperatively. Radiographic parameters included hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (LDFA), mechanical medial proximal tibial angle (MPTA), mechanical axis deviation (MAD), and tibial slope. Clinical evaluations included pain (VAS), Knee Society Score (KSS), WOMAC, KOOS, Forgotten Joint Score (FJS), Oxford Knee Score (OKS), satisfaction (0-10 scale), and range of motion (ROM). Side-to-side comparisons were performed using Wilcoxon signed-rank and paired t-tests where appropriate.

HKA was significantly greater on the left side (5.00 ± 3.86°) compared to the right (3.74 ± 3.22°) (p = 0.0087), and LDFA was also significantly higher on the left (91.51 ± 3.89° vs. 90.20 ± 2.83°, p = 0.0009), indicating a varus tendency on the left knees. No significant differences were found in MAD, MPTA, or tibial slope. Similarly, clinical outcomes including VAS, KSS, WOMAC, KOOS, FJS, OKS, ROM, and satisfaction scores showed no significant differences between the two sides (all p > 0.05).

Despite the presence of subtle but statistically significant varus alignment on the left knees, clinical outcomes were equivalent between sides. These findings suggest that mild side-related radiographic asymmetries may not compromise functional recovery or patient satisfaction in simultaneous bilateral TKA performed by experienced surgeons.