A case of glenohumeral joint impingement caused by a giant secondary synovial osteochondromatosis

Introduction and importance: Synovial osteochondromatosis of the shoulder joint is predominantly primary, characterized by multiple osteochondral fragments, with reports of secondary synovial osteochondromatosis being rare. Case presentation: The patient, a 48-year-old male, presented to our hospital with right shoulder pain persisting for several months. While there was no significant restriction in the range of motion, pain was noted during horizontal adduction and external rotation in the dependent position. Radiographs and CT scans revealed an osteochondral loose body in the glenohumeral joint and an osteophyte on the anterior margin of the glenoid cavity. A lidocaine test in the glenohumeral joint was positive, suggesting impingement by the loose body, leading to its surgical removal. Arthroscopically, the loose body was grasped and removed from the anterior aspect of the glenohumeral joint. The osteochondral fragment measured approximately 15 mm, with the total length including soft tissue being about 40 mm. Pathological findings indicated a layered arrangement of synovial cells, consistent with secondary synovial osteochondromatosis. Postoperatively, the shoulder pain improved rapidly, and follow-up was concluded six months after surgery. Clinical discussion: In this case, arthroscopy revealed a Hill-Sachs-like lesion and labral deficiency on the glenoid, suggesting past trauma. However, no bone defect matching the size of the loose body was observed. In secondary synovial osteochondromatosis, small osteochondral fragments can grow with nourishment from the synovium, suggesting the loose body in this case might have similarly enlarged post-trauma. Conclusion: The shoulder pain caused by a giant secondary synovial osteochondromatosis improved by removing the loose body arthroscopically.