Challenging the neutral axis: 15-year results of under-corrected varus in total knee arthroplasty.

PURPOSE

While total knee arthroplasty (TKA) is effective for managing end-stage tricompartmental osteoarthritis, up to 30% of patients report dissatisfaction due to functional limitations. There is increasing interest in whether maintaining slight residual varus alignment may better replicate native knee kinematics and improve outcomes.

METHODS

This retrospective, single-center study evaluated 123 knees in 77 patients who underwent primary TKA between 2008 and 2010. The surgical aim was mild under-correction of varus deformity. Postoperative limb alignment was classified as residual varus (1°-3°), neutral (0°), or mild valgus (1°-2°). Clinical and radiological evaluations were performed at a mean follow-up of 15.5 years. Outcome measures included KOOS, KSS, FJS-12, VAS for pain/satisfaction, range of motion, and the ability to kneel or sit cross-legged. Radiographs assessed mechanical alignment and implant integrity.

RESULTS

Residual varus alignment (1°-3°) was achieved in 78.9% of knees. KOOS, KSS, and FJS-12 scores improved across all groups, with the varus group showing slightly higher final scores (KOOS: 92.8 ± 2.8) compared to neutral (92.0 ± 2.6) and valgus (91.4 ± 3.1), though not statistically significant. Radiographs showed no loosening or failure. Activities such as kneeling and cross-legged sitting were better preserved in the varus group.

CONCLUSION

At 15-year follow-up, patients with mild residual varus alignment demonstrated excellent functional outcomes and implant survival, with trends toward better satisfaction and cultural functionality. Mild under-correction in varus knees appears safe and may support more personalized alignment strategies.