PSEUDODEFECT OF THE CAPITELLUM - POTENTIAL MR-IMAGING PITFALL

PURPOSE: To describe the pseudodefect of the distal humerus at the junction of the capitellum and lateral epicondyle, which may simulate an osteochondral lesion on axial and coronal magnetic resonance (MR) images. MATERIALS AND METHODS: MR imaging studies of the elbow in 32 patients and 22 asymptomatic volunteers were retrospectively reviewed. Thirty-two human humeri were also examined for normal anatomy of the junction of the capitellum and distal humerus. RESULTS: Twenty-two of the clinical MR examinations and 14 of the studies on volunteers revealed the presence of the pseudodefect. A groove at the junction and the overhanging lateral edges of the capitellum account for the appearance of this pseudolesion. CONCLUSION: Familiarity with the characteristic appearance and location of this pseudodefect will prevent its misinterpretation as an osteochondral fracture of the distal humerus.