A 28-year-old male presents to the emergency department following a fall on his outstretched left hand while playing cricket. He reports severe pain in the proximal forearm and inability to pronate/supinate the forearm. On examination, there is swelling over the proximal third of the ulna with a palpable deformity. X-ray of the left forearm shows a fracture of the proximal third of the ulna with anterior angulation, and the radial head appears dislocated anteriorly on the lateral view. What is the most likely diagnosis?

Explanation

## Diagnosis: Monteggia Fracture-Dislocation **Key Point:** A Monteggia fracture-dislocation is defined as a fracture of the proximal or middle third of the ulna combined with anterior dislocation of the radial head. This is a classic injury pattern from a fall on an outstretched hand or direct blow to the forearm. ### Clinical Presentation - **Mechanism:** FOOSH (fall on outstretched hand) or direct blow to forearm - **Location:** Proximal or middle third ulnar fracture - **Associated injury:** Anterior radial head dislocation (most common) - **Symptoms:** Severe pain, swelling, loss of pronation/supination ### Imaging Findings | Feature | Monteggia | Galeazzi | |---------|-----------|----------| | **Primary fracture** | Ulna (proximal/middle third) | Radius (distal third) | | **Associated dislocation** | Radial head (anterior) | Distal radioulnar joint (DRUJ) | | **Mechanism** | FOOSH, direct blow | FOOSH with wrist extension | | **Pronation/Supination** | Loss due to radial head dislocation | Preserved initially | ### Monteggia Classification (Bado) 1. **Type I (60%):** Anterior angulation of ulnar fracture + anterior radial head dislocation 2. **Type II (15%):** Posterior angulation of ulnar fracture + posterior radial head dislocation 3. **Type III (20%):** Metaphyseal ulnar fracture (near growth plate) + anterior radial head dislocation 4. **Type IV (5%):** Fracture of both radius and ulna + anterior radial head dislocation **High-Yield:** The radial head dislocation in Monteggia is often missed on initial radiographs if the lateral view is not carefully examined. Always compare both forearms and look for loss of the radiocapitellar line alignment. **Clinical Pearl:** The "radiocapitellar line" should pass through the center of the capitellum on all views. Disruption of this line indicates radial head dislocation. **Mnemonic:** **MONU** = **M**onteggia = **U**lna fracture + radial head dislocation (anterior) ### Management 1. Closed reduction of radial head dislocation first 2. Reduction and fixation of ulnar fracture (ORIF with plate preferred) 3. Post-reduction imaging to confirm alignment 4. Early mobilization after fixation **Warning:** Missing the radial head dislocation leads to chronic instability, loss of pronation/supination, and poor functional outcomes.