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Formed by C8 and T1 nerve roots and five rise to the medial cord of the brachial plexus.
The ulnar nerve passes medially to the axillary artery and pierces the intramuscularly septum halfway down the arm, passes over the medial head of the triceps, around the posterior aspect of the medial epicondyle and enters the forearm between the flexor carpi ulnaris heads, it then sends branches t the flexor carpi ulnaris and the ulnar half of the flexor digit rum profundus, then it enters the Guyon’s canal.
Passes through the wrist via Guyon’s canal and provides sensation to the small finger and the ulnar side of the ring finger.
Ulnar nerve
The ulnar nerve runs near the ulna bone.
The ulnar collateral ligament of the elbow joint is in relation with the ulnar nerve.
Because it is the largest unprotected nerve injury is common.
It innervates the little finger, and the adjacent half of the ring finger, the palmar aspect of these fingers.
It originates from C8, T1 branch from Medial cord.
Innervates the:
flexor carpi ulnaris
flexor digitorum profundus
lumbrical muscles
opponens digiti minimi
flexor digiti minimi
abductor digiti minimi
interossei
adductor pollicis
When hitting the medial epicondyle of the humerus, with the elbow flexed, an electric shock like sensation occurs.
The ulnar nerve originates from the C8-T1 nerve roots , and descends medial to the brachial artery, up until the insertion point of coracobrachialis muscle.
The ulnar nerve pierces the medial intermuscular septum and enters the posterior compartment of the arm, accompanied by superior ulnar collateral vessels.
Running posteromedially of the humerus, it passes behind the medial epicondyle at the elbow, where it can be palpated.
The ulnar nerve enters the anterior compartment of the forearm between the two heads of flexor carpi ulnaris, lie along the lateral border of the flexor carpi ulnaris.
It runs between the flexor digitorum superficialis, laterally, and flexor digitorum profundus medially.
It run superficial to the flexor retinaculum of hand, but is covered by volar carpal ligament to enter the hand.
In the forearm it has following branches:
Muscular branches of ulnar nerve – supplies one and a half muscles (flexor carpi ulnaris and the medial half of flexor digitorum profundus.l
Palmar branch of ulnar nerve, that arises from the middle part of the forearm and supplies the skin over the hypothenar eminence.
The dorsal branch of ulnar nerve – arises from 7.5 cm above the wrist, winds backwards to supplies the skin of the proximal part of the ulnar one and half fingers and the adjoining area between the fingers.
Articular branches are given off to the elbow joint.
It enters the palm of the hand via the Guyon’s canal, superficial to the flexor retinaculum and lateral to the pisiform bone.
At the palm it gives off:
Superficial branch of ulnar nerve – supplying the palmaris brevis and gives digital branches to the medial one and a half fingers.
The deep branch of ulnar nerve accompanies the deep branch of the ulnar artery, and passes backwards between the abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi, supplying all the three muscles, and lying on the hook of hamate bone.
It supplies the 3rd and 4th lumbricals and all the palmar interossei muscles and dorsal interossei of the hand, and terminates by supplying the adductor pollicis.
The ulnar nerve also sensory innervates the fifth digit and the medial half of the fourth digit, and the corresponding part of the palm:
The palmar branch of ulnar nerve supplies cutaneous innervation to the anterior skin and nails.
The dorsal cutaneous branch of ulnar nerve supplies cutaneous innervation to the dorsal medial hand and the dorsum of the medial 1.5 fingers.
The ulnar nerve and its branches innervate the following muscles in the forearm and hand:
In the forearm, via the muscular branches of ulnar nerve:
Flexor carpi ulnaris
Flexor digitorum profundus (medial half)
In the hand, via the deep branch of ulnar nerve:
Hypothenar muscles
Opponens digiti minimi
Abductor digiti minimi
Flexor digiti minimi brevis
The third and fourth lumbrical muscles
Dorsal interossei
Palmar interossei
Adductor Pollicis
Flexor pollicis brevis , deep head
In the hand, via the superficial branch of ulnar nerve:
Palmaris brevis
The ulnar nerve can suffer injury between its origin of the brachial plexus to its distal branches in the hand.
The ulnar nerve is most commonly injure around the elbow.
It is commonly injured by local trauma or by being pinched.
Injury to the ulnar nerve at different levels manifested specific motor and sensory deficits.
The ulnar nerve is commonly injured by local trauma or a pinched nerve.
Injury of the ulnar nerve at different levels causes specific motor and sensory deficits:
At the elbow mechanisms of injury include: Cubital tunnel syndrome, fracture of the medial epicondyle of the humerus, and fracture of the lateral epicondyle of the humerus.
Motor deficits include weakness in flexion of the hand at the wrist, loss of flexion of ulnar half of digits, or the 4th and 5th digits, loss of ability to cross the digits of the hand.
Motor deficit is absent or very minor in cubital tunnel syndrome as the ulnar nerve is compressed in the cubital tunnel, and not transacted.
Presence of a claw hand deformity when the hand is at rest, due to hyperextension of the 4th and 5th digits at the metacarpophalangeal joints, and flexion at the interphalangeal joints.
Sensory deficit: Loss of sensation or paresthesiae in ulnar half of the palm and dorsum of hand, and the medial 1½ digits on both palmar and dorsal aspects of the hand.
Injury at the wrist,
Common mechanism: penetrating wounds, Guyon canal cyst.
Motor deficits with such injury include: Loss of flexion of ulnar half of digits, or the 4th and 5th digits, loss of ability to cross the digits of the hand, presence of a claw hand deformity when the hand is at rest, due to hyperextension of the 4th and 5th digits at the metacarpophalangeal joints, and flexion at the interphalangeal joints.
The claw hand deformity is a prominent with injury at the wrist as opposed to a lesion higher up in the arm, as it pulls the distal interphalangeal joints of the 4th and 5th digit into a more flexed position, producing a more deformed claw.
Wrist injury sensory deficit: Loss of sensation or paresthesiae in ulnar half of the palm, and the medial 1½ digits on the palmar aspect of the hand, with dorsal sparing.