A Monteggia lesion is a combination of an ulnar deformity or fracture (often distal to the coronoid) and a dislocation of the radial head. This is an unstable fracture pattern.
The fracture of the proximal ulna may be a torus/buckle deformity, an incomplete (‘greenstick’), or a complete fracture.
The dislocation of the radial head may be either dorsal or lateral. If the radial head has spontaneously reduced following injury, it may be unstable and redislocate during rehabilitation.
Monteggia lesion with oblique fracture of the ulna
Monteggia lesion with proximal (metaphyseal) ulnar fracture