A Novel Patient-Specific Instrument Design Can Deliver Robotic Level Accuracy in Unicompartmental Knee Arthroplasty

Background: A previous randomised controlled trial (RCT) by our group found that robotic assisted unicompartmental knee arthroplasty (UKA) surgery was significantly more accurate than conventional instrumentation. The aim of this study was to determine whether a low-cost novel PSI design could deliver the same level of accuracy as the robot in a more time efficient manner. Methods: Thirty patients undergoing medial UKA took part. Tibial component position was planned using a low dose CT-scan, and compared to a day 1 postoperative CT-scan to determine the difference between the planned and achieved position. Operations were performed by one expert surgeon using PSI (Embody, London, UK). Oxford knee scores (OKS) and EQ-5D-5L were collected preoperatively and at 12 months postoperatively. Results: The mean absolute difference between planned and achieved tibial implant position using PSI was 2 (sd 1) in the coronal plane, 1.8 (sd 1.5) in the sagittal plane, and 4.5 (sd 3.3) in the axial plane. These results were not significantly different to the thirteen historical robotic cases (mean difference 0.5, 0.5, and 1.7, p=0.1907, 0.2867 and 0.1049 respectively). PSI mean operating time was on average 62 min shorter than the robotic group (p<0.0001). There was a significant increase in mean OKS (p<0.0001) and EQ-5D-5L index (p<0.0001). No complications were reported. Conclusions: In conclusion, this clinical trial demonstrates that for tibial component positioning in UKA, a novel design PSI guide in the hands of an expert surgeon, can safely deliver comparable accuracy to a robotic system, whilst being significantly faster.