A 32-year-old man presents to the emergency department after a fall on an outstretched hand with pronation. Radiographs reveal a fracture of the proximal third of the radius with anterior angulation, and a posterior dislocation of the radial head at the radiocapitellar joint. Regarding the management and anatomy of Monteggia fractures, all of the following are true EXCEPT:

Explanation

## Monteggia Fracture Classification and Anatomy **Key Point:** A Monteggia fracture is a fracture of the proximal or middle third of the ulna combined with anterior dislocation of the radial head. The direction of radial head dislocation varies by fracture location and mechanism. ### Radial Head Dislocation Direction by Fracture Type | Monteggia Type | Ulnar Fracture Location | Radial Head Dislocation | Mechanism | |---|---|---|---| | Type I (60%) | Proximal/middle third | **Anterior** | Hyperpronation | | Type II (15%) | Distal third | **Posterior** | Fall on flexed elbow | | Type III (20%) | Metaphyseal | Anterior | Axial loading | | Type IV (5%) | Proximal radius + ulna | Anterior | Axial loading | **High-Yield:** The stem describes a **proximal third fracture with posterior dislocation of the radial head**. This is **NOT a classic Type I Monteggia**—it is actually a **Type II pattern** (distal ulnar fracture with posterior radial head dislocation). The statement "The radial head dislocation is typically anterior in Monteggia fractures of the proximal third" is **FALSE** because: - Proximal/middle third ulnar fractures → **anterior** radial head dislocation - Distal third ulnar fractures → **posterior** radial head dislocation The patient's presentation (proximal ulnar fracture + posterior radial head dislocation) is a **rare variant or misclassification**, but the option as written is incorrect for a proximal third fracture. ### Management Principles **Key Point:** Closed reduction is first-line for most Monteggia fractures. The radial head usually reduces spontaneously once the ulnar fracture is reduced. 1. **Closed reduction technique:** - Reduce the ulnar fracture first (usually by manipulation) - Supinate the forearm to relocate the radial head - Immobilize in supination in a long-arm cast or splint 2. **Indications for open reduction internal fixation (ORIF):** - Displaced or angulated ulnar fracture - Irreducible radial head dislocation - Comminuted fractures - Associated injuries **Clinical Pearl:** Persistent radial head dislocation after closed reduction of the ulna is a red flag for: - Interposed soft tissue (annular ligament, capsule) - Associated fractures of the radial neck - Need for open reduction ### Surgical Anatomy and Nerve Risk **High-Yield:** The **anterior interosseous nerve (AIN)** is a branch of the median nerve that is at risk during: - **Henry (volar) approach** to the radius—passes between flexor pollicis longus and flexor digitorum superficialis - **Thompson (dorsal) approach** to the radius—between extensor carpi radialis longus and extensor carpi radialis brevis AIN injury causes loss of thumb IP flexion and index finger DIP flexion (loss of flexor pollicis longus and flexor digitorum profundus to index). ### Functional Consequences of Missed Radial Head Dislocation **Key Point:** Failure to reduce the radial head dislocation leads to: - Loss of pronation and supination - Chronic pain and instability - Early degenerative changes at the radiocapitellar joint - Functional disability This is why careful imaging and reduction verification are essential.