Deep branch of ulnar nerve

At a glance

English

Deep branch of ulnar nerve

Latin (TA2)

Ramus profundus nervi ulnaris

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the deep branch of ulnar nerve

The ulnar nerve enters the hand on the front of the flexor retinaculum, passing through the ulnar canal (Guyon's canal), a fibro-osseous tunnel between the pisiform medially and the hook of the hamate laterally. Within or just beyond the canal it divides into a superficial branch, mainly sensory, and a deep branch, which is almost entirely motor. The deep palmar branch of the ulnar artery travels with the deep branch.

From its origin the deep branch dives deeply between abductor digiti minimi and flexor digiti minimi brevis, then pierces opponens digiti minimi and curves round the hook of the hamate. It then turns laterally across the palm in the concavity of the deep palmar arch. Here it lies on the interossei and the metacarpals, deep to the long flexor tendons and the lumbricals, and it ends in the thenar region.

Along this curve it supplies, in order, the three hypothenar muscles, all the palmar and dorsal interossei, the third and fourth lumbricals, adductor pollicis, and the deep head of flexor pollicis brevis. Articular twigs from it reach the wrist joint, in keeping with the rule that a nerve to muscles acting on a joint also supplies the joint.

Because it controls the fine movements of the fingers, injury to this branch weakens spreading and closing the fingers and pinching. Compression in Guyon's canal, for example from cycling or a ganglion, can affect it alone. Then the hand muscles waste while the skin of the little finger feels normal, unlike a higher ulnar lesion. Weakness of adductor pollicis shows as Froment's sign, flexion of the thumb tip when the patient tries to grip paper between thumb and index finger.

Course and supply

Arises from

The ulnar nerve, as one of its two terminal branches at the ulnar canal beside the pisiform (fibres from C8 and T1).

Ends in

Ends in the thenar region in adductor pollicis and the deep head of flexor pollicis brevis.

Supplies

Motor to the hypothenar muscles, all the interossei, the third and fourth lumbricals, adductor pollicis and the deep head of flexor pollicis brevis; articular to the wrist joint.