Osteochondritis dissecans of the humeral capitellum in identical twins
17-year-old identical male twins had been actively playing ice-hockey for 7 years at a national level. During the last 18 months both patients had pain and occasional locking of the right elbow. The clinical history was unremarkable, as there were neither medical records nor history of previous major trauma to the elbow. Both were right-handed players, so more valgus stress on the right capitellum was created. On clinical examination, a slight extension deficit up to 5° of the affected elbow was present in both. There were no other clinical abnormalities.\nRadiographs (Figs. and ) showed some flattening and subchondral lucencies of the articular surface of the capitellum in both patients. Also, multiple loose bodies in the joint space were seen. Twin B had a small osteochondral lesion at the anterior part of distal capitellar surface, and osteophytes at the medial aspect of the elbow as an early sign of arthrosis was seen as well. Joint effusion was present in both patients.\nMRI was performed 3 months later using a 1.5T scanner (Siemens Symphony, Siemens Medical Solutions, Erlangen, Germany) with a standard flexible surface coil. Imaging was performed with the elbow in maximal extension. Coronal, axial, and sagittal T2 (TR 3000–5690/TE 107–110) and proton density (PD) (TR 3000–5690/TE 21–37) weighted spin-echo (SE) sequences with fat saturation were obtained with additional coronal T2 and PD SE sequences without fat saturation. Imaging matrix was 320 × 192–245, field of view ranged from 12 × 9 cm to 14 × 12.6 cm.\nTwin A (Fig. ) had cartilage defects, bone marrow edema, and osseous changes in the capitellum. Joint effusion and intra-articular loose bodies were also present. This twin had also osteophytes at the medial aspect of the elbow as an early sign of arthrosis.\nTwin B (Fig. ) had joint effusion and intra-articular loose bodies. There were cartilage and osseous defects with surrounding edema in the capitellum. On the cartilage surface there was a small loose cartilaginous particle, as a hyperintense rim extending to the articular space on T2-w images surrounded it.\nThe right elbow arthroscopy was performed in lateral decubitus position with the forearm hanging freely over a bar. The anterior compartment was first examined through anterolateral and anteromedial portals, followed by posterior compartment viewing through posterolateral and posterior portals.\nAt arthroscopy, Twin A had a mild synovitis, and loose bodies were detected (Fig. ). The articular surface of capitellum was soft without unstable cartilage or visible subchondral bone. There was fraying of the articular cartilage of the radial head but it was otherwise normal. Superficial damage was also seen on the articular cartilage of trochlea.\nTwin B also had mild synovitis and loose bodies (Fig. ). There was softening of the cartilage on the articular surface of capitellum. Articular cartilage of the radial head was normal.