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Radial head and neck fractures are common elbow injuries caused most often by a fall on an outstretched hand that transmits axial force through the forearm to the elbow. In adults, radial head fractures are typically intra-articular and are classified using the Mason classification, with treatment ranging from early mobilization for minimally displaced fractures to open reduction, fixation, or radial head replacement for displaced or comminuted injuries. In children, fractures usually occur at the radial neck because the radial head is largely cartilaginous, and they are commonly classified by the Judet system based on angulation. Management in paediatric cases is mainly conservative for angulation less than 30°, while larger deformities may require closed reduction or minimally invasive fixation. Early diagnosis and appropriate management are important to prevent complications such as elbow stiffness, loss of forearm rotation, avascular necrosis, and radioulnar synostosis.
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Radial head fractures are the most common fractures about the elbow in adults, accounting for approximately 33% of all elbow fractures. They occur most commonly from a fall onto an outstretched hand (FOOSH), during which axial compression transmits force from the wrist through the forearm to the radiocapitellar joint, fracturing the radial head as it impacts the capitellum. The Mason classification (1954), modified by Johnston (1962), Broberg and Morrey (1987), and Hotchkiss (1997), is the universal system for describing radial head fracture morphology and guides management — from conservative treatment for simple undisplaced fractures to arthroplasty for severely comminuted fractures.
| Mason Type | Fracture Description | Displacement | Forearm Rotation Block | Management |
|---|---|---|---|---|
| Type I — Undisplaced | A non-displaced or minimally displaced fracture of the radial head or neck; the fracture may be partial articular (marginal fragment) or a fissure fracture; the articular surface is intact or nearly so; displacement is <2 mm | <2 mm displacement; no significant articular step-off | NO mechanical block to forearm rotation — the undisplaced fragment does not interfere with pronation/supination; if forearm rotation is painful but free of mechanical block, the injury is a Type I | NON-OPERATIVE — aspiration of the elbow haemarthrosis (under LA) + sling for comfort for 1–2 weeks → early mobilisation (within 1 week); the haemarthrosis is the primary source of pain and stiffness; aspiration provides immediate pain relief and allows earlier motion; excellent functional outcomes with early mobilisation; do NOT immobilise for more than 2 weeks (joint stiffness risk) |
| Type II — Partial articular, displaced | A partial articular fracture involving part of the radial head (marginal fracture — one sector of the radial head is fractured); the fragment is displaced >2 mm; the fracture is fixable with standard fragment-specific techniques (the fragment is large enough to accept a screw); impaction of articular cartilage ± mechanical block to forearm rotation may be present | >2 mm displacement; articular step-off; the fragment may be tilted, displaced, or impacted | MAY have a MECHANICAL BLOCK to forearm rotation from the displaced fragment impinging on the proximal ulna or the capitellum; clinical test: `block test` — after aspiration and LA instillation, active or passive forearm rotation is assessed; if smooth full rotation is possible → no block → conservative management may be appropriate; if there is a block to rotation → ORIF or excision of the fragment | ORIF if: (1) mechanical block to forearm rotation; (2) displacement >2 mm (3 mm in some systems); (3) fragment >25–30% of the radial head (a fragment this size significantly affects joint mechanics and bears load); technique: Herbert screws or mini-fragment screws placed in the `safe zone` (posterolateral 90° arc — the non-articulating zone); elbow is approached via the Kocher (anconeus-ECU) or Kaplan (EDC-ECRB) approach; non-operative for undisplaced or asymptomatic Type II with no block (selected cases) |
| Type III — Comminuted, non-reconstructable | A COMMINUTED fracture of the entire radial head with multiple fragments; the fracture is NOT amenable to fixation (too many fragments, all <3 mm, no adequate surface for screw purchase); the radial head is essentially shattered; the fracture cannot be reconstructed by ORIF — the individual fragments are too small and comminuted for individual fixation | Extensive comminution; no single fixable fragment; the radial head is in multiple pieces | Mechanical block is invariably present from the comminution and displaced fragments; the radial head has lost its structural integrity; simple excision will create a mechanical block-free forearm but creates instability (particularly in the Essex-Lopresti pattern or with associated MCL injury); replacement with a metallic radial head prosthesis is preferred | METALLIC RADIAL HEAD ARTHROPLASTY — the radial head prosthesis restores forearm length, provides valgus stability, and prevents proximal radial migration; do NOT perform radial head EXCISION WITHOUT replacement in the terrible triad or Essex-Lopresti patterns (catastrophic instability will result); the prosthesis is placed in the `safe zone` (posterolateral); assess the DRUJ and MCL intraoperatively after arthroplasty |
| Type IV — With elbow dislocation (Johnston addition) | ANY Mason Type (I, II, or III) radial head fracture associated with an ELBOW DISLOCATION; the Johnston modification (1962) added this category to acknowledge that the combination of radial head fracture + elbow dislocation creates a distinct and more complex injury pattern; the combination is equivalent to the `terrible triad` if a coronoid fracture is also present | Variable displacement depending on underlying Mason Type; the elbow dislocation adds ligamentous and soft tissue injury to the bony fracture | The elbow dislocation has torn the lateral collateral ligament complex (and often the MCL) in addition to fracturing the radial head; even a Mason Type I fracture with an elbow dislocation requires careful reassessment of elbow stability after reduction; the terrible triad (posterior dislocation + radial head fracture + coronoid fracture) is a specific and serious form of Type IV injury | Reduce the elbow dislocation FIRST (closed reduction); reassess the radial head fracture and elbow stability after reduction; manage the radial head fracture according to its Mason type (I → conservative if stable; II → ORIF; III → arthroplasty); repair the LUCL and coronoid as part of the terrible triad protocol (see Article 150) |
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