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Findings: AP (1) and lateral (2) views of the forearm are obtained. These views demonstrate a comminuted fracture involving the proximal one third of the ulna with anterior angulation. The radial head is dislocated anterior.

Diagnosis: Monteggia Fracture-Dislocation (Type 1).

Discussion: Monteggia Fracture-Dislocation usually is a result of forced pronation of the forearm during a fall or from a direct blow onto the posterior aspect of the ulna. An isolated radial head dislocation in adults without a fracture would be quite rare. There are four types of these injuries. This is the Bado classification. Type I is a fracture of the proximal and middle thirds of the ulna with anterior angulation associated with an anterior dislocation of the radial head. Type II is a fracture of the proximal ulna with posterior angulation and posterior or posterolateral dislocation of the radial head. Type III is a fracture of the proximal ulna with lateral or anterolateral dislocation of the radial head. Type IV are fractures of both the proximal ends of the radius and ulna with an anterior dislocation of the radial head. This is the least common.

References:
Greenspan A. Orthopedic Radiology. Gower, 1992.

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