Presentation
Motorcyle accident. Limited range of motion of the left elbow.
Patient Data
Radiographs revealed a capitellum fracture. Loss of the articular surface congruency is noted on the frontal view. On the lateral view, the double-arc sign is noted, indicating a fracture that involves the capitellum and extends beyond the lateral trochlear ridge to include a part of the trochlea.
(See annotated image below)
Annotated double-arc sign of a coronal shear fracture of the distal humerus.
The double-arc sign is characterized by two separately visible arcs representing the displaced capitellum and the trochlea.
Case Discussion
Capitellum fractures are rare distal humerus fractures, the latter are usually caused by falls from standing height onto the elbow or motor vehicle collisions.
In the present case, the double-arc sign is noted, which indicates a coronal shear fracture of the distal humerus.