Some vagaries of the olecranon.

The maturing olecranon of the ulna is readily prone to misinterpretation because its normal radiographic characteristics may closely resemble those of fractures, for the following reasons: (1) just prior to ossification of the olecranon epiphysis, a straight sclerotic edge develops in the associated metaphysis on the proximal part of the ulna; (2) ossification of the olecranon begins in two or more centers that commonly fuse with each other before fusing with the parent bone and that may be separated widely from the metaphysis in the early stages; and (3) the physis of the olecranon frequently migrates distally into the joint and may simulate a fracture line. Features distinguishing the normal olecranon from a fracture are discussed in this paper.