A prospective double-blinded randomized controlled trial comparing conventional jig-based versus robotic arm-assisted medial unicompartmental knee arthroplasty

Abstract

Aims This study reports the interim outcomes of a randomized controlled trial comparing the accuracy of component positions, early functional outcomes, patient-reported outcome measures, and complications in conventional jig-based unicompartmental knee arthroplasty with navigational control (CO UKA) with robotic arm-assisted unicompartmental knee arthroplasty (RO UKA) for patients who have medial compartment knee osteoarthritis (OA). Methods In total, 107 patients with symptomatic medial compartment OA were prospectively randomized to undergo CO UKA (n = 52) or RO UKA (n = 55), representing the currently available recruited cohort. Patients in both treatment groups had CT-based surgical planning. All procedures were completed using the medial parapatellar approach, and all patients received a standardized postoperative rehabilitation programme. Predefined study outcomes were recorded at regular intervals for two years after surgery. Results RO UKA was associated with increased accuracy in executing the planned femoral (p < 0.001) and tibial (p < 0.001) component positions compared with CO UKA. RO UKA was associated with reduced inpatient pain scores (p < 0.001), decreased inpatient opioid analgesia consumption (p = 0.008), and shorter length of hospital stay (p = 0.004) compared with CO UKA. There were no differences between the treatment groups in the Oxford Knee Score (p = 0.299), Knee Injury and Osteoarthritis Outcome Score (p = 0.261), and Western Ontario and McMaster Universities Arthritis Index (p = 0.281) at two-year follow-up. RO UKA was associated with improved Forgotten Joint Score (FJS) at six-month (p = 0.002) and two-year (p = 0.021) follow-up. Patient recruitment declined during the trial as an increasing proportion of eligible patients expressed a preference for RO UKA, and operating surgeons experienced reduced clinical equipoise between the treatment groups. Conclusion The interim results of this study show that RO UKA was associated with increased accuracy in achieving the planned femoral and tibial component positions, improved early functional recovery, and decreased length of hospital stay compared with CO UKA. RO UKA was associated with higher FJSs compared with CO UKA at short- to mid-term follow-up. Cite this article: Bone Joint J 2026;108-B(9):1113–1120.