A 28-year-old male laborer presents to the emergency department following a fall on his outstretched left hand while working at a construction site. On examination, he has swelling and tenderness over the proximal forearm with visible deformity. X-rays reveal a fracture of the proximal third of the ulna with anterior angulation and an associated anterior dislocation of the radial head. What is the most likely diagnosis?

Explanation

## Diagnosis: Monteggia Fracture ### Definition **Key Point:** A Monteggia fracture is a fracture of the proximal or middle third of the ulna with an associated anterior dislocation of the radial head. ### Clinical Presentation The patient presents with: - Swelling and deformity of the proximal forearm - Pain on pronation and supination - Visible anterior angulation of the ulna - Radial head dislocation (anterior in classic type) ### Monteggia Classification (Bado) | Type | Ulnar Fracture Location | Radial Head Direction | Mechanism | Frequency | |------|-------------------------|----------------------|-----------|----------| | I (Classic) | Proximal/middle third | Anterior | FOOSH, fall on flexed elbow | 60% | | II | Proximal/middle third | Posterior | Direct blow to posterior forearm | 25% | | III | Metaphyseal (distal ulna) | Anterior | Fall on outstretched hand | 10% | | IV | Proximal radius + ulna | Anterior | Rare, high-energy trauma | 5% | **High-Yield:** Type I (anterior dislocation) is the most common presentation and occurs from a fall on outstretched hand with the elbow flexed. ### Mechanism of Injury 1. Fall on outstretched hand with elbow flexed 2. Hyperpronation force applied 3. Proximal ulna fractures with anterior angulation 4. Radial head is pulled anteriorly by the annular ligament ### Diagnostic Imaging - **AP and lateral forearm X-rays:** Essential to visualize both the ulnar fracture and radial head position - **Key radiographic sign:** Draw a line through the radial shaft on lateral view—it should pass through the capitellum. If it doesn't, radial head dislocation is present. **Clinical Pearl:** The radial head dislocation is often missed on initial radiographs if the lateral view is not carefully examined. Always check the relationship of the radial head to the capitellum on the lateral view. ### Management 1. **Closed reduction** of the radial head (usually reduces spontaneously once the ulna is reduced) 2. **ORIF of the ulna** with plate fixation (compression plating preferred) 3. Post-operative immobilization in supination for 3-4 weeks 4. Early mobilization to prevent stiffness **Warning:** Missed radial head dislocation leads to chronic instability, loss of pronation/supination, and poor functional outcomes.