PSEUDODEFECT OF THE CAPITELLUM - POTENTIAL MR-IMAGING PITFALL

PURPOSE: To describe the pseudodefect of the distal humerus at the jun ction of the capitellum and lateral epicondyle, which may simulate an osteochondral lesion on axial and coronal magnetic resonance (MR) imag es. MATERIALS AND METHODS: MR imaging studies of the elbow in 32 patie nts and 22 asymptomatic volunteers were retrospectively reviewed. Thir ty-two human humeri were also examined for normal anatomy of the junct ion of the capitellum and distal humerus. RESULTS: Twenty-two of the c linical MR examinations and 14 of the studies on volunteers revealed t he presence of the pseudodefect. A groove at the junction and the over hanging lateral edges of the capitellum account for the appearance of this pseudolesion. CONCLUSION: Familiarity with the characteristic app earance and location of this pseudodefect will prevent its misinterpre tation as an osteochondral fracture of the distal humerus.