Proximal ulnar osteochondroma as a potential risk factor for radial head dislocation: A retrospective analysis.

Background: Hereditary multiple osteochondromas (HMO) affecting the proximal radius and ulna represent a rare condition with limited documentation in the clinical literature. This study aims to describe a rare presentation of HMO involving the proximal forearm and discusses potential implications for management. Methods: We retrospectively reviewed patients with HMO treated at our center between 2010 and 2021. Radiographic measurements included the presence or absence of osteochondromas in the entire forearm, radial head status, degree of ulnar bow, and ulnar length percentage. Radiographic measurements were compared using a Brown-Forsythe and Welch test with Tamhane's T2 post hoc analysis. Results: A total of 12 patients with 14 forearms were included in the study. At the final follow-up, all patients with proximal ulnar tumors who did not undergo resection developed subluxation or dislocation. In contrast, all patients with proximal tumors limited in the radius remained free of subluxation or dislocation of the radial head throughout the follow-up period. The mean ulna length percentage in the Located group was 1.07 ± 0.05, while 1.09 ± 0.03 in the Subluxation group and 0.98 ± 0.09 in the Dislocated group. The mean ulna bow in Located group was 12° ± 7°, while 9° ± 6° in Subluxation group and 15° ± 8° in Dislocated group. No significant differences were observed. Conclusions: Proximal osteochondromas from the lateral side of the ulna may be a high-risk factor leading to radial head dislocation. Therefore, surgical excision of the proximal ulnar tumor could serve as a potential intervention to reduce the risk of radial head dislocation in affected patients.