Severe angulation and/or shortening of one of the forearm bones can be accompanied by fracture of the other bone or dislocation of a radioulnar joint.
In a Monteggia fracture-dislocation, the ulnar fracture is associated with a dislocation of the radial head, at the proximal radioulnar joint and the radiocapitellar joint.
These are classified by AO/OTA, according to the morphology of the ulnar fracture, with qualifier (m). For example, the illustration shows a 2U2A3(m).
In most such cases, the radial head dislocates anteriorly or laterally; rarely is the dislocation posterior.
Simple fractures are often the result of indirect mechanisms, such as a fall onto an outstretched hand, sporting activities, etc. Surgical management of ulnar fractures is generally more straightforward because of the architecture of the ulna and its superficial location.