In a Monteggia fracture, which of the following is the MOST common associated injury?

Explanation

## Monteggia Fracture: Definition and Associated Injury **Key Point:** A Monteggia fracture is defined as a fracture of the proximal or middle third of the ulna combined with **anterior dislocation of the radial head**. This is the pathognomonic association. ### Anatomical Basis The anterior angulation or fracture of the ulna disrupts the normal relationship between the radial head and the capitellum of the humerus. The radial head, no longer restrained by the intact ulna, displaces anteriorly. The interosseous membrane and annular ligament are stretched but typically remain intact. ### Classification (Bado) | Type | Ulna Fracture Location | Radial Head Dislocation | Mechanism | |------|------------------------|-------------------------|----------| | I | Proximal/middle third | Anterior | Fall on outstretched hand (FOOSH) with pronation | | II | Middle/distal third | Anterior | FOOSH with supination | | III | Metaphyseal (near growth plate) | Anterior | Direct blow or fall | **High-Yield:** Type I (anterior dislocation) accounts for ~60% of Monteggia fractures. Posterior dislocation is rare and occurs only in atypical variants. ### Clinical Pearl The radial head dislocation is often **missed on initial radiographs** if the examiner does not specifically look for it. Always draw an imaginary line through the radial shaft — it should pass through the center of the capitellum on all views. If it does not, suspect radial head dislocation. **Mnemonic:** **MORAD** = **MO**nteggia = **RAD**ial head dislocation (anterior). [cite:Rockwood & Green's Fractures in Adults Ch 24]