Understanding Radial Tunnel Syndrome
Radial tunnel syndrome occurs when the posterior interosseous nerve (PIN), a branch of the radial nerve, becomes compressed as it passes through the radial tunnel in the forearm. This tunnel is formed by muscles and fibrous bands just below the elbow.
The most common compression site is the arcade of Frohse - a fibrous arch in the supinator muscle. Unlike tennis elbow, which affects the tendon attachment, radial tunnel syndrome is a nerve compression problem that causes deep, aching forearm pain.
This condition is frequently misdiagnosed as "resistant tennis elbow" because the pain is in a similar location. Approximately 5% of patients diagnosed with lateral epicondylitis actually have radial tunnel syndrome, either alone or in combination.
Symptoms & Signs
Radial Tunnel vs Tennis Elbow
These conditions are often confused. Here's how to tell them apart:
- Pain 3-4 cm below lateral epicondyle
- Worse with middle finger extension test
- No numbness typically
- Deep, aching pain in forearm
- Pain directly at lateral epicondyle
- Worse with wrist extension
- Tender at bone attachment
- Usually responds to standard treatments
Important Clinical Clue
If tennis elbow treatment fails after 3-6 months, consider radial tunnel syndrome. Up to 5% of "resistant tennis elbow" cases are actually nerve compression.
Diagnostic Tests
Middle Finger Extension Test
Pain with resisted extension of middle finger
Resisted Supination Test
Pain with forearm supination against resistance
Point Tenderness
Maximum tenderness 3-4 cm distal to lateral epicondyle
MRI
May show nerve swelling or muscle changes
EMG/NCS
Often normal; helps rule out other conditions
Diagnostic Injection
Local anesthetic relief confirms diagnosis
Treatment Approach
- Activity modification - avoid aggravating movements
- Wrist splinting in neutral position
- NSAIDs for pain and inflammation
- Physical therapy focusing on nerve gliding
- Ergonomic modifications at work
- Forearm stretching and strengthening
- Diagnostic/therapeutic nerve block
- Ultrasound-guided injection
- Prolotherapy in some cases
- Release of compression sites (arcade of Frohse)
- Can be done open or endoscopically
- Often combined with tennis elbow release
- Success rate: 70-90%
- Recovery: 6-12 weeks