Ulnar Nerve Block

Ulnar nerve blocks have various clinical indications. Blockade of the ulnar nerve is not limited to providing anesthesia and analgesia in the acute pain setting, but it also extends to the field of chronic pain. Although many factors contribute to the success of the block, the benefit of understanding the dermatomal, myotomal, and osteotomal supply of the nerve is of paramount importance.

Ulnar nerve block can provide a rescue for incomplete brachial plexus blocks, especially with the interscalene approach. A prospective, randomized, observer-blinded study found that concomitant ulnar, median, and radial nerve blocks in conjugation with infraclavicular blocks accelerate anesthesia onset time and improve block consistency. ^{[1, 2, 3, 4]}

When the surgical procedure also includes the ring or the middle finger, median nerve block should be performed because it supplies the lateral half of the ring finger as well as the dorsum of the last 2 phalanges of the ring and middle finger.

Surgical block for creation of arteriovenous fistula can be achieved when ulnar nerve block is combined with median nerve block.

The block is frequently used in the emergency room. Liebmann et al described the feasibility of ultrasound-guided radial, median, and ulnar nerve blocks in the emergency department. ^[5] Recently, Stone et al described draining a fifth-finger abscess and palmar cellulitis under ultrasound-guided surgical ulnar nerve block. ^[6]

In chronic pain, ulnar nerve neuropathy and failed ulnar nerve transposition can be managed by insertion of a peripheral stimulator. ^[6] A diagnostic ulnar nerve block is recommended before proceeding to implantation of an electrode.

General contraindications include patient refusal and infection at block site. Also, block of the nerve should not be performed for cases of long tourniquet time. Unless done for diagnostic purposes, blocking the nerve in patients with ulnar nerve neuropathy is not advocated.

The ulnar nerve is the continuation of the medial cord of the brachial plexus. The nerve receives fibers from the C8 and T1 roots. Often, the nerve carries nerve fibers from the C7 root as well. The nerve runs distally through the axilla between the axillary artery and vein. At the mid-level of the arm, it pierces the medial intermuscular septum and inclines in front of the medial head of the triceps toward the space between the medial epicondyle and olecranon. At the elbow, it lies in a groove on the dorsal surface of the medial epicondyle (sulcus ulnaris). The nerve then runs anterior to the flexor digitorum profundus.

In the forearm, the nerve runs medial to the ulnar artery. It then ends by dividing in superficial and deep terminal branches. The ulnar nerve sends articular branches to the elbow joint and muscular branches to the flexor carpi ulnaris and flexor digitorum profundus. The superficial terminal branch supplies the skin of the lateral third of the palm and both the little finger and medial half of the ring finger.

The deep terminal branches supply the intercarpal, carpometacarpal, and intermetacarpal joints. ^[7] The ulnar nerve and its branches provide innervation to the medial half of the dorsum of the hand, little, ring, and middle finger, except for the terminal 2 phalanges of the middle and ring fingers. They also provide motor supply to the 3 hypothenar muscles, adductor pollicis, and flexor pollicis brevis, all interosseous muscles, and the last 2 lumbrical muscles.