Radial Nerve Compression at the Forearm (Lateral Side)

Anatomy & Terminology

• Superficial branch of radial nerve (SBRN) - purely sensory, runs under brachioradialis
• Posterior interosseous nerve (PIN) - the deep motor branch, enters the radial tunnel and passes through the arcade of Frohse (ligament of Frohse at the leading edge of the supinator muscle)

Sites of Compression (Radial Tunnel - 5 Potential Points)

1. Fibrous bands anterior to the radial head
2. Recurrent radial vessels (leash of Henry)
3. Leading edge of ECRB (extensor carpi radialis brevis)
4. Arcade of Frohse (most common - leading fibrous edge of the supinator)
5. Distal edge of the supinator

Clinical Features

• Lateral elbow/radial forearm pain with no motor or sensory dysfunction
• Point of maximum tenderness several centimeters distal to the lateral epicondyle (differentiates from lateral epicondylitis, which is at the epicondyle)
• Provocative tests: resisted long-finger extension reproduces pain; resisted supination
• Electrodiagnostic tests typically inconclusive

• Weakness or loss of finger extension, thumb extension
• Wrist extends but radially deviates (ECRL is spared, ECRB and EDC are affected)
• No sensory loss
• EMG/NCV confirms denervation pattern

Treatment

Non-Operative (First-Line)

1. Activity modification - avoid repetitive forearm rotation, gripping tasks
2. Splinting - cock-up wrist splint with wrist in neutral or slight extension; keeps elbow slightly flexed and forearm in neutral rotation to reduce tension
3. NSAIDs - to reduce inflammation and pain (short course)
4. Corticosteroid injection - a single injection into the radial tunnel may be tried (evidence is limited but can provide relief in radial tunnel syndrome)
5. Physical therapy - nerve gliding exercises, stretching of the supinator and ECRB
6. Avoidance of compressive activities - watchbands or tight clothing (especially for Wartenberg syndrome)

Non-operative treatment should be prolonged - up to 1 year before considering surgery for radial tunnel syndrome.

Surgical Decompression (If Non-Operative Fails)

• Failure of non-operative treatment after 6-12 months (radial tunnel syndrome)
• Progressive or significant motor loss - PIN syndrome with failure of non-operative treatment
• Confirmed compression on EMG/NCV with progressive decline

• Anterior (Henry's approach) - between brachioradialis and brachialis
• Posterior (Thompson's approach) - between ECRB and EDC
• Transbrachioradialis approach - direct approach through brachioradialis (alternative)
• Endoscopic-assisted decompression is an emerging less-invasive alternative

• Fibrous bands at the radial head
• Leash of Henry (recurrent radial vessels, if compressive)
• Leading edge of ECRB
• Arcade of Frohse (most important decompression point)
• Distal edge of supinator if needed

• PIN syndrome: better, more predictable results
• Radial tunnel syndrome: only 50-80% good-to-excellent outcomes - less predictable, with prolonged postoperative recovery

Summary Algorithm

Radial nerve compression at lateral forearm
          |
    ┌─────┴──────┐
  Pain only    Motor weakness
(Radial Tunnel)   (PIN Syndrome)
    |                  |
Non-op x 6-12 mo    EMG/NCV confirm
(splint, NSAIDs,    |
 activity mod,      Non-op trial
 injection)         (splint, PT)
    |                  |
 Fails?             No improvement or
    ↓               progressive weakness
 Surgical               ↓
decompression      Surgical decompression
(50-80% success)   (more predictable results)

• Campbell's Operative Orthopaedics 15th Ed 2026, pp. 4528+
• Miller's Review of Orthopaedics 9th Ed, pp. 694-695
• Sabiston Textbook of Surgery, p. 2764 (Radial Nerve Compression)
• Harrison's Principles of Internal Medicine 22E, p. 3657
• Mulholland & Greenfield's Surgery, p. 6049
• Systematic review: Hones KM et al., Eur J Orthop Surg Traumatol 2024 [PMID: 38782802] - establishing diagnosis of radial tunnel syndrome