Simple fractures are often the result of indirect mechanisms, such as a fall onto an outstretched hand, sporting activities, etc. More details about their clinical and radiographic examination see here .
Surgical management of ulnar fractures is generally more straightforward because of the architecture of the ulna and its superficial location.
Simple fractures of the ulna are classified based on the direction of the fracture line, as well as on the possible concomitant involvement of the radioulnar joints.
1. Oblique and spiral fractures
These fractures include:
- Spiral fractures of the ulna (AO/OTA 2U2A1)
- Oblique fractures of the ulna (AO/OTA 2U2A2)
Simple fractures are likely to occur at the middle zone of the diaphysis, where the ulna has thick cortices, a narrow medullary canal, and an approximately triangular cross-section.
These include transverse fractures of the ulna.
These are classified by AO/OTA as 2U2A3.
Ulnar fractures may occur with minimal displacement. If they are misinterpreted as hairline fractures and are not strictly immobilized, there is a risk of delayed union, or pseudoarthrosis.
3. With dislocation of proximal radioulnar joint (Monteggia)
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.