Sensory supply: Dorsum of hand. The nerve descends from the axilla, winding posteriorly around the humerus. The deep branch - the posterior interosseous nerve - lies in the posterior compartment of the forearm behind the interosseous membrane.
Extensor carpi radialis longus Extensor carpi radialis brevis
Extensor digitorum Extensor digiti minimi Extensor carpi ulnaris Abductor pollicis longus
. Extensor pollicis longus Extensor pollicis brevis Extensor indicis
- Fractures of the humerus.
- Prolonged pressure
(Saturday night palsy).
- Intramuscular injection.
- Lipoma, fibroma or neuroma.
- Systemic causes. Results in:
- Weakness and wasting of muscles supplied, characterised by wrist drop with flexed fingers (weak extensors). Sensory loss on dorsum of hand and forearm. Loss of triceps reflex (when lesion lies in the axilla) and supinator reflex.
The posterior interosseous branch of the radial nerve can be compressed at its point of entry into the supinator muscle. The clinical picture is similar to a radial nerve palsy, only brachioradialis and wrist extensors are spared. Examination shows weakness of finger extension with little or no wrist drop.
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