Engagement of the Radial Head in Posterior Capitellum Fracture: Defining the Critical Point.

Introduction: Elbow dislocation is usually treated conservatively with a good outcome. When there is associated injury to the capitellum, "Osborne-Cotterill Lesion," then the clinical course is less predictable and controversial. In this article, we attempt to define the critical point on the capitellum surface that, when breached, forebodes potential engagement of the radial head in the defect and imminent dislocation. Case Report: We present two cases of fracture and fracture dislocation of the elbow with "Osborne-Cotterill lesion." They were treated with fracture reduction and fixation. In the first case, a posterior plate was utilized for the olecranon, and in the second case, cannulated screws were employed for the capitellum fracture. In both cases, a posterior humeral plate was applied to counteract the "Osborne-Cotterill lesion" with bone grafting of the defect. Conclusion: When the critical point of the capitellum is breached (roughly a quarter of the capitellar articular surface or less when the radial head is injured),we recommend bone grafting the defect and plating the posterior capitellum to impede potential dislocation.