Anterior Interosseous Nerve

All muscle strictly receive nerve supply from anterior interosseous nerve except

A. Pronator quadrates
B. Flexor pollicis longus
C. Flexor digitorum profundus of index finger
D. Flexor digitorum profundus of middle finger

Answer .D. Flexor digitorum profundus of middle finger

·         Flexor digitorum profundus of middle finger is supplied by the ulnar nerve in 20% of the population.

·         Anterior interosseous nerve (AIN),a branch of median nerve, supplies all the deep muscles of the anterior  forearm exceptpart of the flexor digitorum profundus.

·         Flexor digitorum profundus (FOP) gives 4 tendons to the 4 fingers (except finger no. 1 - the thumb!).

·         FDP of Finger no. 2 & 3 are controlled by the AIN and 4 & 5 by the ulnar nerve majority of the population. It is evident that the middle finger is mostly supplied by the AIN.

·         In 20% of the population the ratio is 3:1 (AIN supplying the finger no. 1, 2 & 3, whereas, ulnar supplying only the finger 4). It is evident that even the ring finger is being supplied by AIN here.

·         In 20% of the population the ratio is 1 :3, that is , AIN supplies finger no. 1 and 2, 3, & 4 are supplied by the ulnar nerve. Here it is evident that FDP of middle finger is being supplied by the ulnar nerve.

·         Hence, FDP of middle finger is supplied by the AIN in 80% of the population, but in 20% of the population it is supplied by the ulnarnerve.