The Osborne-Cotterill lesion: a Radiographic analysis of morphology & clinical Impact.

HYPOTHESIS: The Osborne-Cotterill lesion (OCL) is an osseoligamentous injury of the posterolateral capitellum associated with elbow instability. Its contribution to instability remains unclear, and evidence guiding management is limited. This study aimed to quantify the incidence and anatomy of OCLs and to correlate these findings with patterns of elbow instability, treatment, and outcome.

METHODS

A database of acute elbow instability cases was reviewed. After application of exclusion criteria, 181 elbow computed tomography scans were available for analysis. A standardized method was developed to reconstruct scans in the plane of the distal humerus. Data were collected on injury pattern, surgical intervention, and complications. A circle-of-best-fit technique was applied to sagittal cross sections to template normal capitellar anatomy. Measurements were oriented to the anterior humeral line to describe the OCL. Variables recorded included area of bone loss, angle of involvement, anterior and posterior exit points, and lesion width.

RESULTS

An OCL was identified in 120 elbows (66%), whereas 61 elbows (34%) demonstrated no bone loss consistent with an OCL. By instability pattern, OCLs were present in 61 of 85 posterolateral rotatory instability cases (72%), 25 of 35 posteromedial rotatory instability cases (71%), 25 of 39 axial instability cases (64%), and 9 of 22 valgus instability cases (41%). The incidence was significantly lower in valgus injuries (P = .046). OCLs were most commonly located in the posterolateral capitellum. Relative to the anterior humeral line, 3 anatomic patterns were identified: anterior (1.7%), intermediate (11.7%), and posterior (86.6%). Two pathologic subtypes were defined by morphology: impaction (93.3%) and avulsion (6.7%). Overall, 114 cases were treated surgically, of which 9 OCLs (7 avulsion, 2 impaction) underwent operative treatment directed at the lesion itself. There were 17 complications, including recurrent instability in 7 patients. No complications were directly attributable to an untreated OCL.

CONCLUSION

This is the first study to quantify the incidence and morphologic characteristics of OCLs in a large cohort. Based on these findings, 3 anatomic patterns (anterior, intermediate, and posterior) and 2 pathologic subtypes (avulsion and impaction) are proposed. Most OCLs were posterior impaction lesions treated nonoperatively. Avulsion lesions, and OCLs located anteriorly or intermediately, were less common but appeared more strongly associated with instability and may warrant consideration for surgical treatment.