Radial Tunnel Syndrome

What is it?

The posterior interosseous nerve is compressed within the radial tunnel at the Arcade of Frohse by repetitive pronation/supination.

Commonly affected: Radial tunnel 3–5 cm distal to lateral epicondyle

How it develops

1. Normal Nerve PathPIN passes freely through supinator fascia
2. Repetitive RotationOccupational or sport-related forearm rotation
3. Nerve CompressionNerve compressed at Arcade of Frohse
4. Deep AcheDeep ache 3–5 cm distal to lateral epicondyle

Symptoms

• Lateral Elbow Ache (distal)Deep ache 3–5 cm distal to lateral epicondyle
• Forearm Rotation PainPain with resisted supination/pronation
• Night PainPain often wakes patient
• Weakness (rare)Finger extension weakness if PIN palsy develops

How it is examined

• Resisted SupinationPain with resisted forearm supination
• Middle Finger Extension TestPain with resisted middle finger extension
• Lateral Epicondyle Non-tenderLateral epicondyle usually non-tender (differs from tennis elbow)
• Radial Tunnel TendernessTenderness 3–5 cm distal to lateral epicondyle

Imaging

Usually normal — rules out bony causes.

• Normal
• Rules out bony impingement

MRI/US identify nerve compression or masses.

• PIN edema/thickening
• Supinator muscle T2 hyperintensity (late)
• Space-occupying mass

When surgery is considered

6-month conservative failure or motor deficit

Procedures that may be discussed

• Radial tunnel decompression
• Arcade of Frohse release

Outlook

Conservative care helps 60–70%; surgical success 70–80%.