A 28-year-old man presents to the emergency department with pain and swelling in the left forearm following a fall on an outstretched hand. Clinical examination reveals tenderness over the proximal third of the radius and posterior angulation of the elbow. A posterolateral dislocation of the radial head is suspected. Which investigation is the gold standard for confirming the diagnosis of Monteggia fracture-dislocation?

Explanation

## Investigation of Choice for Monteggia Fracture-Dislocation ### Radiographic Diagnosis **Key Point:** Plain radiographs remain the gold standard and first-line investigation for suspected Monteggia fracture-dislocation. The classic triad must be visible on imaging: 1. Fracture of the proximal or middle third of the ulna 2. Anterior dislocation of the radial head (posterolateral in type II) 3. Disruption of the radiocapitellar joint ### Standard Radiographic Views **High-Yield:** The diagnostic protocol includes: - **Anteroposterior (AP) view** — identifies ulnar fracture and radial head alignment - **Lateral view** — best demonstrates radial head dislocation and angulation - **Radial head view** (45° pronation view) — optimizes visualization of the radial head and capitellum relationship ### Why Plain Radiographs Are Sufficient **Clinical Pearl:** Monteggia fracture-dislocation is a clinical and radiographic diagnosis. The fracture of the ulna combined with radial head dislocation is pathognomonic and does not require advanced imaging for diagnosis. Plain films provide: - Clear visualization of fracture lines and displacement - Assessment of radial head position relative to the capitellum - Evaluation of angulation and comminution - Guidance for reduction and surgical planning ### Role of Advanced Imaging **Tip:** CT or MRI are reserved for: - Complex or comminuted fractures requiring surgical planning - Evaluation of associated soft-tissue injuries (ligaments, cartilage) - Assessment of occult fractures or non-union - Post-reduction assessment if plain films are inconclusive They are NOT first-line investigations for initial diagnosis. [cite:Campbell's Operative Orthopaedics 13e Ch 53]