Capitellum fractures are rare elbow injuries accounting for less than one percent of fractures around the elbow. They are more common in females.

Mechanism of injury is usually a fall on the outstretched hand, the radius imparting a shearing force on the capitellum.

According to the Bryan and Morrey classification (with McKee modification), there are four types of capitellum fractures:

• type I (Hahn-Steinthal): large fragment containing substantial subchondral bone
• type II (Kocher-Lorenz): sleeve fracture with minimal bone
• type III: (Broberg-Morrey fracture): comminuted
• type IV: fracture includes a major portion of the trochlea

In this case, it is a type IV fracture. The characteristic finding on the lateral x-ray is the “McKee’s double-arc sign” because of the subchondral bone of the capitellum and lateral part of the trochlea.