Robotically-assisted unicondylar knee arthroplasty (UKA) is intended to improve the precision with which the components are implanted, but the impact of alignment using this technique on subsequent polyethylene surface damage has not been determined. Therefore, we examined retrieved ultra-high-molecular-weight polyethylene UKA tibial inserts from patients who had either robotic-assisted UKA or UKA performed using conventional manual techniques and compared differences in polyethylene damage with differences in implant component alignment between the two groups. We aimed to answer the following questions: (1) Does robotic guidance improve UKA component position compared to manually implanted UKA? (2) Is polyethylene damage or edge loading less severe in patients who had robotically aligned UKA components? (3) Is polyethylene damage or edge loading less severe in patients with properly aligned UKA components? We collected 13 medial compartment, non-conforming, fixed bearing, polyethylene tibial inserts that had been implanted using a passive robotic-arm system and 21 similarly designed medial inserts that had been manually implanted using a conventional surgical technique. Pre-revision radiographs were used to determine the coronal and sagittal alignment of the tibial components. Retrieval analysis of the tibial articular surfaces included damage mapping and 3D laser scanning to determine the extent of polyethylene damage and whether damage was consistent with edge loading of the surface by the opposing femoral component.Introduction
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