Radial head and neck fractures

The commonest elbow fracture in adults. The radial head is a secondary stabiliser against valgus and a key stabiliser against posterolateral rotation and proximal migration of the radius. It may be an isolated, simple injury or the visible part of a complex one: elbow dislocation, coronoid fracture (terrible triad), MCL tear, or rupture of the interosseous membrane (Essex-Lopresti).

Mechanism

Fall on the outstretched hand with the forearm pronated and the elbow slightly flexed: axial load drives the radial head against the capitellum, often with a valgus component.

Clinical findings

• Tenderness over the radial head (lateral, just distal to the epicondyle), painful rotation; elbow effusion.
• Test for a mechanical block to rotation after aspirating the haemarthrosis and injecting local anaesthetic.
• Always examine the wrist (DRUJ, interosseous membrane), the MCL and elbow stability.

Imaging

• AP and lateral of the elbow.
• Radiocapitellar (Greenspan) view: lateral elbow with the beam angled 45° towards the shoulder, projects the head free of the coronoid.
• CT for comminuted, displaced or complex injuries; X-rays of both wrists if the DRUJ is painful (Essex-Lopresti).

• AP and lateral of the elbow; a radiocapitellar (Greenspan) view projects the head free of the ulna.
• Undisplaced fractures may show only a positive fat pad sign (sail sign).
• CT when comminution, displacement or associated coronoid injury is in doubt; wrist X-rays of both sides if Essex-Lopresti is suspected.

Classification

2R1A

Extra-articular: neck fractures (A2 simple, A3 multifragmentary).

2R1B

Partial articular head fracture, simple or multifragmentary.

2R1C

Complete articular head fracture, the whole head is separated from the neck.

Mason (Hotchkiss modification)

I undisplaced or minimally displaced (< 2 mm), no block to rotation; II displaced > 2 mm or angulated, repairable, may block rotation; III comminuted, judged not reconstructable; IV (Johnston) with elbow dislocation.

Types shown in 3D

Mason I

Undisplaced or minimally displaced (< 2 mm) partial articular fracture, no block to rotation. Early motion.

Mason II

Partial articular fragment displaced more than 2 mm, tilted and depressed. Fix if it blocks rotation or the elbow is unstable (headless screws).

2R1A2 neck

Simple neck fracture: the whole head tilts (here laterally and backwards) on the shaft. Up to about 30° of tilt is accepted in adults with free rotation; otherwise fixation in the safe zone.

Mason III

Comminuted head (multifragmentary 2R1B or 2R1C): several fragments, often impacted and displaced. When fixation would be unreliable (more than three fragments), radial head arthroplasty.

Mason IV

Radial head fracture with elbow dislocation: the fragment stays near the capitellum while the forearm dislocates posteriorly. Reduce, then fix or replace the head and repair the lateral ligament; look for a coronoid fracture (terrible triad).

Treatment

Mason I and small II fragments without a block

Sling for a few days and early active motion. Aspiration of the haemarthrosis relieves pain. Good outcome in the large majority.

Mason II with a block or part of a complex injury

Open reduction and internal fixation through a lateral approach (Kocher or Kaplan): headless or small countersunk screws for partial articular fragments; a small plate only in the "safe zone" (the 90–110° arc of the head not in contact with the ulna in rotation). Keep the forearm pronated to protect the posterior interosseous nerve.

Mason III and IV

If more than three fragments or the fixation would be unreliable: radial head arthroplasty (modular metal prosthesis; avoid overstuffing). Excision is acceptable only in a stable elbow with an intact interosseous membrane and medial ligament, never in an acute complex injury.

Associated injuries

Address the coronoid and capsule first, then fix or replace the head and repair the lateral ligament complex (terrible triad). Essex-Lopresti: always restore radial length (prosthesis) and stabilise the DRUJ.

Aftercare

Early active motion within a few days; avoid passive stretching. Watch extension and rotation at follow-up.

Complications

• Stiffness (loss of terminal extension, rotation)
• Posterior interosseous nerve injury during exposure
• Missed Essex-Lopresti injury (proximal migration of the radius, wrist pain)
• Hardware impingement outside the safe zone
• Prosthesis overstuffing and capitellar wear
• Heterotopic ossification