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Updated: Jan 23, 2026

In Vitro Application of a Wireless Sensor in Flexion-Extension Gap Balance of Unicompartmental Knee Arthroplasty
Published on: May 5, 2023
Tendency of Tibial Component Placement and Short-Term Outcomes in ROSA-Assisted Unicompartmental Knee Arthroplasty
Daichi Ishimaru1, Kazuki Sohmiya1, Nobuo Terabayashi1
1Department of Orthopaedic Surgery, Gifu Seiryu Hospital, Gifu, Japan.
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.
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