A 32-year-old male labourer presents to the emergency department following a fall on his outstretched left hand while working at height. He reports severe pain in the proximal forearm and inability to supinate the forearm. On examination, there is swelling over the proximal third of the forearm with a palpable anterior angulation. X-ray of the left forearm shows a fracture of the proximal third of the ulna with anterior displacement of the radial head. 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 (FOOSH) or direct blow to the forearm. ### Clinical Presentation - Severe pain and swelling in the proximal forearm - Loss of supination (due to radial head dislocation) - Visible anterior angulation of the ulna - The radial head dislocation is often missed on initial examination if the fracture is the focus ### Radiological Features | Feature | Monteggia | Galeazzi | |---------|-----------|----------| | **Bone fractured** | Ulna (proximal/middle third) | Radius (distal third) | | **Associated dislocation** | Radial head (anterior) | Distal radioulnar joint (dorsal) | | **Mechanism** | FOOSH, direct blow | Fall on extended wrist | | **Loss of function** | Supination impaired | Pronation impaired | **High-Yield:** The key to diagnosis is recognizing that ANY ulnar fracture in the proximal or middle third MUST be accompanied by careful assessment for radial head dislocation. The radial head dislocation can be subtle on AP views and may only be apparent on lateral radiographs. ### 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 (rare):** Fracture of both radius and ulna + anterior radial head dislocation **Clinical Pearl:** The injury mechanism in this case (FOOSH with proximal forearm trauma) is classic for Type I Monteggia. The anterior radial head dislocation explains the loss of supination, as the biceps (primary supinator) cannot function effectively when the radial head is displaced anteriorly. ### Management - Closed reduction under general anesthesia (reduce radial head first, then align ulnar fracture) - Percutaneous pinning of the ulna if unstable - Long-arm cast for 6-8 weeks - Early mobilization after union to prevent stiffness **Mnemonic:** MONTEGGIA = **Ulna fracture + Anterior Radial head dislocation** (remember: "Monteggia = ulna + radial head") [cite:Rockwood & Green's Fractures in Adults Ch 30]