Optimization of postoperative unicompartmental knee arthroplasty radiography using a phantom-based ray-summation positioning sheet

Achieving accurate positioning in postoperative unicompartmental knee arthroplasty (UKA) radiography is challenging, often necessitating increased exposure and examination time. We developed a positioning assistance sheet based on ray-summation images simulating rotation, flexion, and extension, and validated its efficacy in reducing exposure. We retrospectively analyzed 115 knees imaged between January 2024 and February 2025. A knee phantom was scanned to generate ray-summation images, which were used to design the assistance sheet. The mean number of exposures was compared before and after implementation, with a significant decrease from 3.26 to 2.37 (P = 0.03). The reduction was particularly pronounced among radiology technologists with < 5 years of experience. Furthermore, no significant differences were observed between left and right knees post-implementation (P = 0.30), confirming the sheet’s bilateral applicability. Consequently, the positioning assistance sheet significantly reduced the number of exposures required for postoperative UKA radiographs and proved effective regardless of technologist experience or laterality.