Classification of Monteggia fractures were given by Bado. Initially Bado described four types of this lesion.
Type I
Fracture of the ulnar diaphysis at any level with anterior angulation at the fracture site and an associated anterior dislocation of the radial head.
Type II
Fracture of the ulnar diaphysis with posterior angulation at the fracture site and a posterolateral dislocation of the radial head.
Type III
Fracture of the ulnar metaphysis with a lateral or anterolateral dislocation of the radial head.
Type IV
Fracture of the proximal third of the radius and ulna at the same level with an anterior dislocation of the radial head.
After Bado, four different subgroups of the posterior Monteggia lesion [type II] were suggested by Jupiter et al. These subgroupings were based on the location of the ulnar fracture.
Type IIA
The ulnar fracture involves the distal olecranon and coronoid process.
Type IIB
The ulnar fracture is at the metaphyseal and diaphyseal juncture, distal to the coronoid.
Type IIC
The ulnar fracture is diaphyseal.
Type IID
The ulnar fracture extends along the proximal third to half of the ulna.
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