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.