Early clinical outcomes after robotic-assisted medial unicompartmental knee arthroplasty according to age: a retrospective cohort study
TL;DR
In selected patients undergoing medial RA-UKA, no statistically significant age-group differences in measured early outcomes were detected during the first month, and serial observations provide reference points for early postoperative counselling but do not establish equivalent recovery or comparative safety.
Abstract
Evidence describing recovery during the first month after robotic-assisted medial unicompartmental knee arthroplasty (RA-UKA) across age groups is limited. We compared pain, active knee motion, function, and satisfaction in patients aged < 65 and ≥ 65 years. In this single-centre retrospective cohort, 358 patients were screened; 34 were excluded from the analytic cohort on the basis of pre-existing eligibility criteria, and 23 of the remaining 324 did not attend day-30 follow-up. The principal analysis included 301 patients (146 aged < 65 years; 155 aged ≥ 65 years) who underwent medial RA-UKA between April 2024 and November 2025. Pain at rest on a visual analog scale (VAS) and active knee range of motion were assessed at baseline, on postoperative days 1 and 3, and at approximately days 14 and 30. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society scores were assessed at baseline and the outpatient visits. Baseline-adjusted linear mixed-effects models estimated age-group differences. Adjusted day-30 VAS and WOMAC contrasts were designated co-primary during revision (Bonferroni threshold, P < 0.025 each). Sensitivity analyses included available observations from non-completers and adjustment for American Society of Anesthesiologists (ASA) class. Mean VAS decreased and active knee motion increased in both groups during the first month. The adjusted day-30 differences (Older minus Younger) were − 0.030 VAS points (95% CI − 0.220 to + 0.161; P = 0.760) and − 0.447 WOMAC points (95% CI − 1.526 to + 0.631; P = 0.416); neither met the revised significance threshold. Group-by-visit interactions were not statistically significant for VAS (F (3, 897) = 0.517; P = 0.670) or WOMAC (F (1, 299) = 0.023; P = 0.879). Among day-30 completers, 144/146 Younger patients (98.6%) and 154/155 Older patients (99.4%) reported satisfaction scores of 4 or 5 (absolute difference + 0.7% points; 95% CI − 2.4 to + 4.3). All 23 non-completers lacked day-30 outcome and satisfaction data. In selected patients undergoing medial RA-UKA, no statistically significant age-group differences in measured early outcomes were detected during the first month. These serial observations provide reference points for early postoperative counselling but do not establish equivalent recovery or comparative safety.