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Radial tunnel syndrome

Radial tunnel syndrome (RTS) is a compressive neuropathy (without any motor deficits) affecting one of the terminal branches of the radial nerve, the posterior interosseous nerve (PIN), as it passes through the radial tunnel.


The concept is that the radial nerve becomes irritated and/or inflamed from friction caused by compression by muscles in the forearm.


Sometimes categorized into radial tunnel syndrome and PIN syndrome:
RTS: Painful condition without motor deficits
PIN syndrome: PIN motor neuropathy
Significant overlap in many cases, making some question the differentiation.

Radial tunnel syndrome anatomy
Radial tunnel syndrome anatomy

Symptoms

  • There is gradual onset of exercise induced pain around the elbow that typically radiates distally.
  • Heaviness in upper forearm
  • Occasional vague dorsal wrist pain
  • Increase in symptoms with repetitive activities such as forearm rotation, elbow extension, and maximum wrist flexion-extension
  • Acute: Pain usually absent at rest, provoked by powerful grasping and lifting activities, worse at end of the day
  • The symptoms are diffuse, not well defined, overlap those of the much more prevalent lateral epicondylitis.


Clinical Findings


There is a much overlap between lateral epicondylitis and radial tunnel syndrome exam findings.


  • Tenderness to palpation over the radial tunnel - 4 fingerbreadths distal to the lateral epicondyle rather than at the common extensor origin on the lateral epicondyle in case of lateral epicondylitis.
  • There is pain around the elbow on resisted extension of the middle finger Tinel’s sign is positive.
  • Nerve conduction test may be positive.


Note: PIN syndrome is distinct from RTS in that patients with PIN syndrome have a significant motor deficit. This includes loss of finger and thumb extension and radial deviation of the wrist during extension because of the consistent PIN innervation of the extensor carpi ulnaris as opposed to the extensor carpi radialis longus (which is usually innervated by the radial nerve proper).

Treatment

Nonoperative treatment

  • Anti-inflammatory medications, rest, and avoidance of provocative activities
  • A splint can be used to maintain forearm supination and wrist extension.
  • Physical therapy focused on ergonomic retraining, stretching, and eventual strengthening of the extensor-supinator group. Many sports can be maintained.
  • Running, cycling and swimming are good alternatives to keep up general fitness.