Radial nerve

What is it?

Radial Tunnel Syndrome (RTS) is pain arising on the outer-side of the elbow as a result of entrapment of the posterior interosseous (PIN) branch of the radial nerve in the upper part of the forearm just below the elbow.

What Causes it?

RTS is caused by entrapment of the PIN at one of four sites.

  1. Under Extensor Carpi Radialis Brevis
  2. Leash of Henry (arteries that cross the nerve in the upper part of the forearm)
  3. Arcade of Froshe (Fibrous upper border of the supinator muscle)
  4. Lower (distal) border of the supinator muscle

The entrapment can occur as a result of inflammation, oedema, haematoma or space occupying lesions.

How does it present?

RTS presents with a deep ache or burning sensation in the outer aspect of the forearm about 4 to 5cm below the lateral epicondyle (bony prominence on the outer aspect of the elbow).  The onset of symptoms may be associated with overuse, trauma or the use of elbow clasps for the treatment of tennis elbow, but in many cases no obvious trigger can be identified.

Many of the clinical signs of RTS are the same as for tennis elbow and the diagnosis can only be made when everything else had been ruled out as there is no test that is diagnositic.

The diagnosis is suggested by tenderness in the muscles in the line of the radial nerve in the absence of tenderness at the lateral epicondyle.  Pain on resisted middle finger extension, or resisted supination are seen in RTS but also occur in tennis elbow.  In some case the elbow may be stiff.

What tests can be done to make the diagnosis?

There are no good tests to diagnose RTS.  Nerve conduction studies may be positive but if negative do not rule out the diagnosis.  MRI scans may identify oedema, or a space-occupying lesion but are not routinely performed.  Before a diagnosis of RTS is made it is important to rule out other cause of pain in this region;

  • Tennis elbow
  • Radiocapitellar Arthritis
  • Loose body
  • Synovial Plica

What is the Treatment of RTS?

The main treatment of RTS is rest, activity modification, and anti-inflammatory medication.  Splints worn on the wrist may help to relieve symptoms.  Physiotherapy with stretches, massage and neural glide techniques may help.

If the symptoms persist or get worse then surgery can be performed to decompress the nerve.

What does this surgery involve?

Radial tunnel decompression is usually performed under general anaesthetic as a day case procedure.  A cut is made in the upper part of the forearm and the structures passing over the nerve are divided.  The arm can be used immediately after surgery for light activities but the wound should be kept clean and dry until it is healed (7-10 days).  Driving is permitted when the car can be controlled safely.

What are the risks of surgery?

The surgery carries the general risks of anaesthesia, risks of infection, bleeding, nerve injury and ongoing symptoms.