flexor digitorum profundus muscle

If the ulnar nerve lesion occurs more proximally (closer to the elbow), the flexor digitorum profundus muscle may also be denervated.

It then runs between flexor digitorum superficialis and flexor digitorum profundus muscles and enters the hand through the carpal tunnel.

The ulnar nerve also innervates the ulnar (medial) half of the flexor digitorum profundus muscle (FDP).

Injury to the AIN can cause paralysis of the flexor pollicis longus and flexor digitorum profundus muscles to the index finger, resulting in loss of the pinch mechanism between the thumb and index finger.

It innervates the flexor carpi ulnaris muscle, the flexor digitorum profundus muscle to the ring and pinky fingers, and the intrinsic muscles of the hand (the interosseous muscle, the lumbrical muscles and the flexor pollicus brevis muscle).

As might be expected, the symptoms involve weakness in the muscle innervated by the AIN including the flexor digitorum profundus muscle to the index (and sometimes the middle) finger, the flexor pollicis longus muscle to the thumb and the pronator quadratus of the distal forearm.

The deepest of the flexor muscles in the anterior forearm is called the flexor digitorum profundus muscle (FDP); it gives off four tendons that travel through the carpal tunnel into the hand and attach to the distal phalanx in each of the four non-thumb digits.