A patient is brought to the emergency with history of trauma to his right upper limb. Extension of metacarpophalangeal is lost. There is no wrist drop and extension of IP joint is normal. The most likely nerve involved is:
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Posterior-interosseous nerve
Extension of metacarpophalangeal joint:
Extensor pollicis longus, Extensor pollicis brevis
Posterior interosseous branch:
Lies in the lateral part of cubital fossa, where it supplies extensor carpi radialis brevis and supinator muscles. Then it enters into the back of forearm by passing through supinator muscle.
There the nerve supplies abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor digitorum, extensor indicis, extensor digiti minimi and extensor carpi ulnaris.
It ends in a pseudo ganglion, branches of which supply the wrist joint.