Presentation
Worsening elbow pain.
Patient Data
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The capitellum is irregular in contour and flattened, with mild fragmentation of the articular surface.
A well-defined ossific structure is observed centrally within the olecranon fossa, measuring approximately 15mm in diameter, with multiple small ossific fragments adjacent to it that are more irregular in appearance.
The anterior fat pad is not elevated.
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The blue arrow indicates the abnormal articular surface of the capitellum, and the blue dotted line outlines the expected shape of the capitellum in a normal elbow.
The yellow arrow points to the ossicle, which appears to represent a normal-variant ossicle, however the other two osseous fragments (open white arrows) suggest this is degenerative (secondary) synovial osteochondromatosis.
Case Discussion
The most striking finding in this study is the ossicle in the olecranon fossa, which is easy to call an os supratrochleare dorsale as a knee jerk reaction. However, synovial osteochondromas also like to find a home in the olecrenon fossa and are much more common, so must be considered if other supportive findings are present such as degenerative joint disease, or in this case osteochondritis dissecans. The other ossific fragments adjacent to the larger ossicle strongly tilt the diagnosis in favor of synovial osteochondroma over a normal variant ossicle in this case. It is not impossible that they had the ossicle as a normal variant first and then subsequently developed OCD, but that would be quite unlikely.
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