Osteoarthritis of Proximal Radioulnar Joint: Computed Tomography-Based Assessment and Associations with Clinical Findings.

Background: Although many studies have focused on the degenerative changes of the ulnohumeral and radiohumeral joints in osteoarthritis (OA) of the elbow, the proximal radioulnar joint (PRUJ), which facilitates the pronation and supination motions of the forearm, has not been comprehensively evaluated. Purpose: To assess the prevalence of PRUJ OA in patients diagnosed with OA of the elbow using computed tomography (CT) images and to establish an association between the CT findings and clinical manifestations. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Between 2010 and 2022, a total of 85 consecutive patients who were scheduled to undergo osteocapsular arthroplasty for OA of the elbow and had undergone preoperative CT imaging were included in the study. As a control group, 85 patients who underwent CT scans of the elbow for reasons other than OA of the elbow were selected and matched to patients in the OA group. CT findings of OA in the PRUJ, including osteophytes, joint space narrowing, subchondral cysts, and loose bodies, were evaluated. Inter- and intraobserver agreement analyses for CT findings were performed. The relationship between the CT findings of OA in the PRUJ and OA of the elbow classification systems (Broberg-Morrey, Hasting-Rettig, and Kwak) as well as clinical manifestations (range of motion [ROM], Mayo Elbow Performance Score, and visual analog scale for pain) were evaluated. Results: Patients in the OA group showed osteophytes in the radial notch (81.2%), osteophytes in the radial head (45.9%), joint space narrowing (54.1%), loose bodies (25.9%), and subchondral cysts (23.5%) involving the PRUJ. Both the interobserver (κ = 0.866) and intraobserver agreements (κ = 0.933) for CT findings of PRUJ OA were almost perfect. The CT findings of PRUJ OA were associated with the severity of OA of the elbow in Cochran-Armitage Trend analysis (with Brogberg-Morray, Conclusion: PRUJ OA could be identified using CT imaging and showed radial notch osteophytes, joint space narrowing, loose bodies within the joint space, and subchondral cysts. PRUJ OA was related to overall OA of the elbow and may contribute to reduced ROM in the elbow joint. Therefore, preoperative evaluation of PRUJ OA can aid in the surgical planning of osteocapsular arthroplasty for OA of the elbow.