Comparable outcomes and early revision rates between restricted and unrestricted functional knee positioning in robotic-assisted total knee arthroplasty for varus deformities ≥10°.

Abstract

Purpose: Functional knee positioning (FKPos) in total knee arthroplasty (TKA) optimises outcomes by balancing individual anatomical and soft tissue characteristics. Managing marked varus deformity presents challenges in achieving balance when tibial alignment is restricted to 3° of varus, necessitating either medial soft tissue release or unrestricted tibial positioning. This study aims to compare restricted FKPos with medial soft tissue release to unrestricted FKPos without soft tissue release in patients with varus deformity ≥10°.

Methods: This retrospective, two-center study analysed robotic-assisted TKAs. Patients were categorised into two groups: restricted FKPos with medial soft tissue release (Group A) and unrestricted FKPos without soft tissue release (Group B). Inclusion criteria required a preoperative coronal alignment of ≥10° varus. Outcomes included Knee Society Scores (KSS), Forgotten Joint Scores (FJS), complications, and implant survivorship over a median follow-up of 38 months (interquartile range [IQR] 30-45).

Results: A total of 205 patients (Group A: 71 and Group B: 134) were included. No significant differences were observed in functional outcomes (KSS and FJS) or complication rates between the groups. Median tibial varus alignment was 1° in Group A and 4.5° in Group B (p < 0.0001). Implant survivorship was comparable between groups (1.4% in Group A and 0.75% in Group B; p = 0.65; hazard ratio = 1.94; 95% confidence interval: 0.11-35.62).

Conclusion: This study demonstrated that restricted FKPos with medial soft tissue release and unrestricted FKPos without soft tissue release result in comparable short-term outcomes, complication rates, and implant survivorship in ≥10° varus deformities. While these findings suggest that unrestricted tibial positioning may be a promising alternative to traditional approaches, further studies with long-term follow-up are needed to confirm its safety and durability.

Level of evidence: Level III.