Radial Neck Fracture

Radial neck fracture is a fracture of the proximal radial metaphysis just distal to the radial head. It is mainly a paediatric injury, with a peak at 9 to 10 years, and makes up about 5 to 10% of paediatric elbow fractures. In adults the injury usually involves the radial head, and the neck is less often fractured alone.

In children most are Salter-Harris type II or metaphyseal fractures. Angulation of the head on the neck grades severity: under 30 degrees, 30 to 60 degrees, and over 60 degrees.

The mechanism is a fall on the outstretched hand with a valgus load that drives the radial head against the capitellum. Associated injuries are elbow dislocation, olecranon fracture, medial epicondyle fracture, and injuries of the medial collateral ligament.

Complications are loss of forearm rotation (the most common), radial head overgrowth, avascular necrosis and premature physeal closure (both more likely after severe displacement or open reduction), proximal radioulnar synostosis, nonunion, and posterior interosseous nerve injury during surgery.

Pathophysiology.

The radial head is tilted by the valgus force, and the neck fractures at the weak metaphyseal physeal junction. The blood supply to the head enters through the periosteum around the neck, so periosteal stripping at open reduction risks avascular necrosis.

Children remodel better than adults. Angulation up to 30 degrees (up to 45 degrees in children under 10) usually remodels, whereas translation over 3 mm or 50% of neck width limits rotation.

There is lateral elbow pain and swelling, tenderness over the radial head, and pain at the extremes of pronation and supination, with limited rotation. Flexion and extension may be preserved.

Examine the wrist and distal radioulnar joint for tenderness suggesting an Essex-Lopresti injury in older patients. Test the posterior interosseous nerve (finger and thumb extension at the metacarpophalangeal joints) and the rest of the neurovascular examination. Look for associated medial elbow tenderness.

• Radiographs: anteroposterior, lateral and radiocapitellar views. The radiocapitellar line (through the radial shaft and neck) should cross the capitellum on every view. Measure head angulation and translation.
• Fat pad signs with a normal radiograph suggest an occult fracture in a child. Ultrasound or MRI shows the cartilaginous neck in the young child.
• Imaging of the whole forearm and wrist when pain extends distally.

Differential diagnosis.

• Radial head subluxation (pulled elbow) and radial head fracture (adults).
• Monteggia fracture dislocation and elbow dislocation.
• Supracondylar fracture and lateral condyle fracture.
• Olecranon fracture and Essex-Lopresti injury.

By angulation (children).

• Under 30 degrees (up to 45 degrees in children under 10 with translation under 3 mm): long arm cast or collar and cuff sling for 2 to 3 weeks, then early movement. Prolonged immobilisation worsens stiffness.
• 30 to 60 degrees: closed reduction under sedation or general anaesthesia. In the Patterson method an assistant holds the elbow extended and applies a varus force with the forearm supinated, while the surgeon presses on the radial head. In the Israeli method the elbow is flexed 90 degrees with the forearm pronated, and the thumb presses the head back.
• Failed closed reduction or over 60 degrees: percutaneous reduction with an intramedullary elastic nail (usually 2.0 mm titanium) inserted at the distal radial metaphysis, advanced to the neck and rotated to lever the head upright. This is preferred over open reduction.
• Open reduction with minimal soft tissue stripping, only after failure of closed methods. Fix with smooth Kirschner wires or a small absorbable implant, never across the capitellum.
• Cast for 2 to 3 weeks after reduction, then active movement.

Adults. Undisplaced fractures: sling for 1 to 2 weeks, then early movement. Displaced fractures with a block to rotation: open reduction and fixation with a mini fragment plate in the safe zone, or radial head replacement for comminution. Check the distal radioulnar joint.

Analgesia.

• Paracetamol 15 mg/kg orally every 4 to 6 hours as needed for up to 5 days (maximum 75 mg/kg daily and not exceeding 4 g daily); reduce the dose and extend the interval in hepatic impairment or malnutrition.
• Ibuprofen 10 mg/kg orally every 6 to 8 hours with food for up to 5 days (maximum 40 mg/kg daily and not exceeding 2400 mg daily), from 3 months of age; avoid with dehydration, NSAID-sensitive asthma or renal impairment.
• Adults: paracetamol 1 g orally every 6 hours for up to 5 to 7 days (maximum 4 g daily; 3 g daily when weight is under 50 kg or in hepatic impairment) and ibuprofen 400 mg orally every 8 hours with food for up to 5 days (maximum 1200 mg daily; avoid with eGFR under 30 mL/min/1.73 m2).

Reduction under sedation. Ketamine 1 to 2 mg/kg intravenously over 1 to 2 minutes as a single dose (a further 0.5 to 1 mg/kg after 10 minutes if needed; 4 to 5 mg/kg intramuscularly without access), given by a clinician skilled in paediatric airway care with continuous oximetry and capnography, after fasting. Avoid with raised intracranial pressure, psychosis or acute upper airway infection.

Monitoring. Radiographs at 1 week, 2 to 3 weeks and 6 weeks. Forearm rotation at 6 weeks, 3 months and 6 months. Annual review to skeletal maturity when growth disturbance or head overgrowth appears. Watch for avascular necrosis and synostosis.

Referral and escalation. Refer all angulation of 30 degrees or more, any translation over 3 mm, and every injury after failed manipulation to paediatric orthopaedics the same day. Urgent referral for an associated dislocation, neurovascular deficit, open injury or a forearm that stays swollen and tense.

Special groups.

• Young children: the cartilaginous neck can hide the injury, so use ultrasound or MRI when pain with rotation persists after a normal radiograph.
• Adults: Essex-Lopresti injuries need forearm and wrist assessment.
• Kidney impairment: avoid ibuprofen.