Tendency of Tibial Component Placement and Short-Term Outcomes in ROSA-Assisted Unicompartmental Knee Arthroplasty Using the Persona Partial Knee System

Background Robot-assisted unicompartmental knee arthroplasty (UKA) has been introduced to improve component positioning. The ROSA Knee System and Persona Partial Knee (Zimmer Biomet, Warsaw, IN, USA) constitute a relatively new robotic platform with limited data. We aimed to quantify tibial and femoral component alignment and evaluate short-term clinical outcomes. Methods We reviewed 64 consecutive medial UKAs performed with this system. Preoperative planning used computed tomography (CT)-based three-dimensional models. Postoperative component alignment was measured on radiographs and CT. Clinical outcomes were assessed with the 2011 Knee Society Score (KSS) preoperatively and at 1 year; paired analyses were performed in 34 knees with complete preoperative and postoperative KSS data. Results Tibial components were implanted in greater varus and with less posterior slope than planned. The planned tibial coronal angle was 0.0° ± 0.1°, whereas the postoperative CT-based angle was −2.7° ± 2.3°; posterior slope decreased from 7.8° ± 1.4° to 4.5° ± 2.4°. Femoral alignment showed minimal deviation. In the 34 knees with complete KSS data, mean symptom, satisfaction, and functional activity subscores improved from 7.4 ± 4.9, 16.1 ± 6.4, and 47.7 ± 17.2 to 19.4 ± 5.3, 29.8 ± 6.4, and 75.7 ± 14.5, respectively (all P < .0001). Conclusions Medial robot-assisted UKA with this system showed generally accurate component positioning but a consistent tendency toward approximately 2° greater tibial varus and reduced posterior slope relative to the plan. Awareness of this systematic deviation may help optimize tibial placement, and short-term clinical outcomes were favorable.