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Objectives and questions: The conversion of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) presents significant surgical challenges due to altered anatomy, bone loss, and soft tissue imbalance. Robotic-assisted techniques have been introduced to improve component alignment, optimize soft tissue balance, and potentially enhance clinical outcomes. However, their role in UKA to TKA conversions remains unclear. This study evaluates the impact of robotic-assisted vs. non-robotic-assisted UKA to TKA conversions on survivorship, early complications, patient-reported outcomes, and postoperative rehabilitation milestones.

Material and methods: This retrospective cohort study included 67 patients who underwent UKA to TKA conversion between 2019 and 2023. Patients were categorized into robotic-assisted (n=17) and non-robotic (n=50) groups. Primary outcomes included survivorship, revision rates, and 90-day complications. Secondary outcomes evaluated operative time, intraoperative blood loss, patient-reported outcome measures (PROMs), range of motion (ROM), radiographic alignment, and time to full weight-bearing. Statistical analyses included Mann-Whitney U tests for continuous variables, Chi-square and Fisher’s exact tests for categorical variables, and Kaplan-Meier survival analysis with log-rank testing.

Results: Baseline characteristics, including age (p=0.052), BMI (p=0.851), ASA score (p=0.3933), and gender distribution (p=0.1402), were similar between groups. Overall survivorship was 82% (95% CI: 56-100), with no significant difference between robotic-assisted and non-robotic groups (86% vs. 98%; p=0.093). Revision rates (p=1.000) and 90-day complications (p=0.639) were comparable between groups.

Operative time was significantly longer in the robotic-assisted group (138.3 ± 50.2 min vs. 110.7 ± 27.7 min, p=0.0386), though tourniquet time (p=0.644) and postoperative ambulation distances (p=0.1542) were not significantly different. Patient-reported outcomes (KOOS Jr, VR12, LEAS, and pain scores) showed no significant differences at baseline or one-year follow-up.

Discussion and conclusion: Robotic-assisted UKA to TKA conversion does not provide significant early clinical advantages over non-robotic techniques in terms of patient outcomes, revision rates, or short-term survivorship. However, robotic-assisted procedures were associated with longer operative times, which did not translate into differences in early rehabilitation metrics. While robotic assistance may improve alignment precision, its impact on long-term outcomes, implant longevity, and functional recovery remains uncertain. Further prospective studies are necessary to assess whether the increased surgical precision offered by robotic systems leads to better survivorship and reduced re-revision rates in the long term.