Radial nerve - posterior interosseous nerve lesions

Causes

  • Entrapment at the radiohumeral joint capsule.
  • Entrapment at the sharp edge of the extensor carpi radialis muscle.
  • Entrapment at the arcade of Frohse (fibrotendineous arch where the nerve enters supinator muscle).
  • Entrapment within supinator muscle (supinator channel syndrome).
  • Compression by brachiocephalic arteriovenous fistula.
  • Compression by tumor, ganglia or cysts.
  • Direct acute or chronic injury.
  • Amyloid neuropathy in multiple myeloma.

Symptoms & signs

  • Supinator muscle is spared.
  • Weakness and atrophy of extensor carpi ulnaris, extensor digitorum, extensor indicis, extensor digiti minimi and abductor pollicis longus and brevis.
  • Difficulty in extending the wrist in ulnar direction.
  • Radial deviation of wrist during extension.
  • Drop-thumb deformity.
  • No sensory deficits.
  • Pain in the dorsal wrist and lateral elbow might exist.