Radial tunnel syndrome

What is radial tunnel syndrome?

Radial tunnel syndrome is a painful condition due to compression neuropathy of the posterior interosseous nerve. There is no sensory or motor deficit.

Anatomy of the Radial Tunnel

Radial tunnel refers to a region extending from the radiocapitellar joint to past the proximal origin of the supinator. 

Potential sites of compression (mnemonic "FREAS")

• Fibrous band anterior to the radiocapitellar joint
• Recurrent vessels (Leash of Henry)
• ECRB medial edge
• Arcade of Frohse (aponeurotic edge of supinator)
• Supinator distal edge

Presentation

• Deep aching pain in the proximal dorsoradial forearm
  • made worse by forearm rotation and lifting

• The following provocative tests may reproduce the symptom but they are not specific enough and may be confused with lateral epicondylitis
  • Passive pronation with wrist flexion
  • Resisted supination with elbow/wrist in extension
  • Resisted long finger extension

• The most reliable sign is perhaps the exact location of maximal tenderness. In radial tunnel syndrome, the tender point is more distal than that of lateral epicondylitis (tennis elbow). The former is maximally tender at 3-5cm distal to the lateral epicondyle while the latter is maximally tender directly over or at 1cm distal to the lateral epicondyle. Both conditions however co-exist.

Investigations

• MRI is used for exclusion of structural anomalies around the nerve. This is typically normal in radial tunnel syndrome.
• NCS/EMG are also typically normal.

Treatment

Nonoperative

• Activity modification & painkillers
• This is the mainstay of treatment 

Operative

• Radial tunnel release/decompression 

Key Message

• Radial tunnel syndrome is essentially a pain syndrome while PIN palsy is associated with motor deficit