KSSTA - 2026-09-11 - Journal Article
Functional alignment robotic-assisted TKA improves clinical outcomes compared with conventional mechanical alignment TKA: A single-surgeon randomised controlled non-inferiority trial with 2-year follow-up.
Coenen R, Peeters A, Bollars P, Nathwani D, Albelooshi A, Ettinger MT, Deltour A, Schotanus MGM
Topics
Key Takeaway
FA-RATKA produced statistically significant improvements over MA-CTKA across multiple PROMs at 2 years, with effect sizes ranging from r=0.117 to r=0.214 (small to small-medium magnitude).
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Summary
This single-surgeon RCT compared functional alignment robotic-assisted TKA (FA-RATKA) to conventional mechanical alignment TKA (MA-CTKA) in 180 patients using mixed-effects models across KSS subdomains, OKS, FJS-12, VAS pain, and EQ-5D-5L. FA-RATKA demonstrated statistically significant Group × Time interactions favoring it for KSS Function (p<0.001, r=0.173), KSS Satisfaction (p<0.001, r=0.214), KSS Symptoms (p=0.004, r=0.138), OKS (p<0.001, r=0.185), VAS pain (p<0.001, r=0.188), and EQ-5D index (p=0.006, r=0.141). All effect sizes were small to small-medium, raising questions about whether the differences exceed minimum clinically important difference thresholds.
Key Limitation
The single-surgeon design prevents generalizability and cannot separate the effect of functional alignment philosophy from robotic assistance or surgeon-specific technical factors.
Original Abstract
PURPOSE
Functional alignment (FA) has emerged as an alternative to mechanical alignment (MA) in total knee arthroplasty (TKA), supported by robotic assistance to enhance precision and soft‑tissue preservation. Evidence comparing FA performed with robotic assistance to conventional MA‑TKA across mid‑term patient‑reported outcomes measures (PROMs) remains limited. This randomised controlled trial evaluated differences in recovery trajectories and 2‑year knee‑specific outcomes between FA‑RATKA and MA‑CTKA.
METHODS
This study reports the predefined primary 2-year outcomes of a prospective randomised controlled non-inferiority trial including 180 patients (FA-RATKA, n = 81; MA-CTKA, n = 82), of whom 163 completed follow-up. Assessments were performed preoperatively and at 3-months, 1- and 2-years using validated PROMs: Knee Society Score (KSS) subdomains, Oxford Knee Score (OKS), Forgotten Joint Score (FJS-12), VAS pain, EQ-5D-5L (index and VAS), Lower Extremity Activity Scale (LEAS), and overall satisfaction. Mixed-effects models evaluated group, time, and Group × Time interactions, adjusting for age, BMI, and soft-tissue release. Effect sizes (r) were calculated to contextualise clinical relevance.
RESULTS
FA-RATKA demonstrated more favourable knee-specific outcomes across follow-up, with significant Group × Time interactions for KSS Function (F(3,679) = 6.970, p < 0.001; r = 0.173), KSS Satisfaction (F(3,679) = 10.892, p < 0.001; r = 0.214) and KSS Symptoms (F(3,679) = 4.425, p = 0.004; r = 0.138). FA-RATKA also showed more favourable OKS trajectories (F(3,679) = 8.053, p < 0.001; r = 0.185), lower VAS pain (F(3,679) = 8.339, p < 0.001; r = 0.188), and higher EQ-5D index scores (F(2,515) = 5.227, p = 0.006; r = 0.141). Categorical satisfaction favoured FA-RATKA at early follow-up (F(2,503) = 3.491, p = 0.031; r = 0.117). Effect sizes ranged from r = 0.117 to 0.214, corresponding to small to small-medium magnitudes.
CONCLUSIONS
In this prospective, randomised, single-surgeon study, several knee-specific patient-reported outcomes demonstrated modest but statistically supported differences at 2-year follow-up, with consistently higher values in the FA-RATKA group.
LEVEL OF EVIDENCE
Level I, randomised controlled trials with adequate statistical power to detect differences (narrow confidence intervals) and follow up >80%, as per the KSSTA guidelines.