Radial Nerve

Anatomy

  • Terminal branch of the posterior cord, C5 to T1
  • Passes through the triangular interval with profunda brachii
  • Spiral groove between lateral and medial triceps heads
  • Pierces the lateral intermuscular septum in the distal third of the arm
  • Supplies brachioradialis and ECRL above the elbow
  • Divides into superficial radial nerve and PIN at the elbow
  • PIN passes under the arcade of Frohse through supinator
  • EIP is the last muscle to recover

Clinical Features

  • Palsy in around one in ten humeral shaft fractures
  • Distal third spiral fracture (Holstein-Lewis)
  • Most are neurapraxias and recover spontaneously
  • PIN syndrome gives painless finger and thumb extension weakness without sensory loss
  • Wrist extends with radial deviation as ECU is weak
  • Arcade of Frohse is the commonest compression site
  • Other sites are radiocapitellar bands, leash of Henry, ECRB edge and distal supinator
  • Intact tenodesis effect excludes extensor tendon rupture
  • Radial tunnel syndrome is pain without weakness, with mobile wad tenderness
  • Pain on resisted supination and resisted middle finger extension
  • Wartenberg syndrome, superficial radial nerve compression between brachioradialis and ECRL

Investigations

Radial Nerve, the suprascapular, axillary and radial nerves, gray’s anatomy plate 818
The suprascapular, axillary and radial nerves, Gray’s Anatomy plate 818. Image by Henry Vandyke Carter, Wikimedia Commons, Public domain.
  • EMG at 6 to 12 weeks if no recovery
  • Brachioradialis is the first muscle to recover
  • Nerve conduction usually normal in radial tunnel syndrome
  • MRI or ultrasound for a mass in PIN syndrome

Management

  • Observe closed fractures with primary palsy, using a wrist splint and passive motion
  • Explore if no recovery at 3 to 6 months
  • Early exploration for open fractures, penetrating or vascular injury
  • Nerve transfers, FDS to ECRB, FCR or palmaris longus branch to PIN
  • Tendon transfers, pronator teres to ECRB, FCR to EDC, palmaris longus to EPL
  • PIN syndrome decompression if no recovery
  • Radial tunnel syndrome managed nonoperatively first

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.