Osborne-Cotterill Lesion: An Osseous Defect of the Capitellum Associated with Instability of the Elbow

OBJECTIVE: Posterolateral rotatory instability of the elbow is a diagnosis largely made by clinical examination; no relevant radiographic signs have been reported. We have seen four patients with an osseous defect and detachment of a fragment of bone in the posterolateral margin of the capitellum. These patients had chronic posterolateral rotatory instability of the elbow. CONCLUSION: An osseous defect of the posterolateral corner of the capitellum is an uncommon finding that in each instance was associated with chronic posterolateral rotatory instability of the elbow. We termed this lesion the "Osborne-Cotterill lesion." We report our findings in these patients; when this lesion is diagnosed, clinicians should consider posterolateral rotatory instability.