We all know the basic anatomy of the elbow with the humerus, radius, and ulna. However, as emergency physicians it is important to recognize the elbow ossification centers that develop during childhood in order to accurately interpret radiographs of the joint. These ossification centers can be mistaken for fractures if one is not careful. There are six ossification centers which develop in a predictable order at somewhat predictable ages. The mnemonic for this is CRITOE.

The Capitellum is first, then the Radial head, followed by the Internal or medial epicondyle. T is for Trochlea, then Olecranon, and E is for the External or lateral epicondyle.

There are normal age ranges during which these will develop, and girls often develop them at slightly younger ages than boys, usually 6-12 months ahead of their male counterparts. In general, an ossification center develops approximately every two years starting with the capitellum around the age of two. Nonetheless, knowledge of the order in which these develop is really what is crucial to help identify fractures from normal ossification centers.

Radiographic Pearls

Alignment

When reviewing imaging of the elbow, one should look for appropriate joint alignment. This involves evaluating two specific markers of alignment. The first is the anterior humeral line. An imaginary line drawn along the front of the humerus should intersect the middle to anterior third of the capitellum. If it does not, a supracondylar fracture should be suspected.