NATON robotic-assisted unicompartmental knee arthroplasty achieves superior radiological alignment and comparable one-year functional outcomes to conventional surgery

To compare the early clinical efficacy and postoperative implant alignment between NATON robotic-assisted unicompartmental knee arthroplasty (RA-UKA) and conventional UKA (C-UKA) in treating severe medial compartment knee osteoarthritis (OA). This retrospective matched cohort study included 40 RA-UKA and 40 C-UKA patients, matched 1:1 by age, gender, and surgical site et al. Primary outcomes included operative time, intraoperative blood loss, and patient-reported outcome measures (PROMs): knee society score (KSS), Oxford knee score (OKS), visual analogue scale (VAS) for pain, and forgotten joint score (FJS). Radiological assessments included coronal/sagittal angular deviations of femoral/tibial components, hip-knee-ankle (HKA) angle, and Kennedy zone distribution. The follow-up time was 15.4 ± 1.6 months. Operative time was significantly longer in the RA-UKA group (95.8 ± 6.8 min vs. 75.3 ± 6.5 min, P < 0.001). No significant differences were observed in KSS score, OKS score, or intraoperative blood loss between groups (all P > 0.05). RA-UKA achieved significantly better subjective PROMs, with lower VAS score (1.97 vs. 2.5, P = 0.012, Cohen’s d = − 0.60) and higher FJS score (86.9 vs. 84.3, P = 0.025, Cohen’s d = 0.50). The RA-UKA group had smaller femoral component coronal alignment deviation (2.39 ± 1.41° vs. 5.79 ± 1.15°, P < 0.001, Cohen’s d = − 2.46) and flexion alignment deviation (3.3° (2.9–4.0) vs. 6.5° (5.9–7.1), P < 0.001, Cohen’s d = − 0.78). No significant differences were observed in tibial component coronal deviation and posterior tibial slope(PTS) deviation between two groups (all P > 0.05). Correlation analysis revealed weak negative correlations between FJS score and femoral coronal/flexion deviations (all P < 0.05). VAS score was weakly positive correlated with PTS deviation (ρ = 0.240, P = 0.032) and moderately positive correlated with femoral coronal deviation (r = 0.311, P = 0.005). No serious complications occurred in either group during follow-up. The NATON RA-UKA achieved more accurate early implant positioning than C-UKA, while short-term clinical outcomes were generally comparable between groups.