Ultrasound-guided ulnar nerve block at the elbow is useful in the management of the pain subserved by the ulnar nerve. This technique serves as an excellent adjunct to brachial plexus block and for general anesthesia when performing surgery below the elbow. Ultrasound-guided ulnar nerve block at the elbow with local anesthetic may be used to palliate acute pain emergencies, including postoperative pain, pain secondary to trauma, and cancer pain, while waiting for pharmacologic, surgical, and antiblastic methods to become effective.

Ultrasound-guided ulnar nerve block can also be used as a diagnostic tool when performing differential neural blockade on an anatomic basis in the evaluation of upper extremity pain as well as in a prognostic manner to determine the degree of neurologic impairment the patient will suffer when destruction of the ulnar nerve is being considered or when there is a possibility that the nerve may be sacrificed during surgeries in the anatomic region of the ulnar nerve at the level of the elbow. This technique may also be useful in those patients suffering symptoms from compromise of the ulnar nerve at the elbow due to compression of the ulnar nerve by the cubital tunnel retinaculum or anomalous anconeus epitrochlearis muscle (Figs. 54.1 and 54.2). Ultrasound-guided ulnar nerve block at the elbow may also be used to palliate the pain and dysesthesias associated with stretch injuries to the ulnar nerve in this anatomic region.

The key landmark when performing ultrasound-guided ulnar nerve block at the elbow is the ulnar artery in the forearm, which lies in proximity to the ulnar nerve (Fig. 54.3). Arising from fibers from the C8 to T1 nerve roots of the medial cord of the brachial plexus, the ulnar nerve lies anterior and inferior to the axillary artery in the 3:00 o’clock to 6:00 o’clock quadrant as it passes through the axilla. As the ulnar nerve exits the axilla, it passes inferiorly adjacent to the brachial artery. At the middle of the upper arm, the ulnar nerve turns medially to pass between the olecranon process and medial epicondyle of the humerus. Continuing its downward path, the ulnar nerve passes between the heads of the flexor carpi ulnaris moving radially along with the ulnar artery. At a point ˜1 inch proximal to the crease of the wrist, the ulnar nerve divides into the dorsal and palmar branches. The dorsal branch provides sensation to the ulnar aspect of the dorsum of the hand and the dorsal aspect of the little finger and the ulnar half of the ring finger (Fig. 54.4). The palmar branch provides sensory innervation to the ulnar aspect of the palm of the hand and the palmar aspect of the little finger and the ulnar half of the ring finger.

The benefits, risks, and alternative treatments are explained to the patient and informed consent is obtained. The patient is then placed in the supine position with the arm in the modified bathing beauty position (Fig. 54.5). The ulnar artery is palpated (Fig. 54.6). With the patient in the above position, a high-frequency linear ultrasound transducer is placed in a transverse position over the dorsal surface of the forearm, and an ultrasound survey scan is taken (Fig. 54.7). The ulnar artery is then identified as is the ulnar nerve lying just next to the artery. The ulnar nerve will have a triangular, hyperechoic honeycomb appearance (Fig. 54.8). Color Doppler can help identify the ulnar artery and other vasculature in the area (Fig. 54.9). After the ulnar nerve has been identified adjacent to the ulnar artery, the ultrasound transducer is slowly moved proximally. The ulnar nerve will be seen to move away from the ulnar artery, which moves deeper into the forearm as it approaches the antecubital fossa (Fig. 54.10). After identification of the ulnar nerve is confirmed, the skin overlying the area beneath the ultrasound transducer is prepped with antiseptic solution. A sterile syringe containing 4.0 mL of 0.25% preservative-free bupivacaine and 40 mg of methylprednisolone is attached to a 1½-inch, 22-gauge needle using strict aseptic technique. The needle is placed through the skin ˜0.5 cm lateral to the lateral aspect of the ultrasound transducer and is then advanced using an in-plane approach through the flexor carpi ulnaris muscle with the needle trajectory adjusted under real-time ultrasound guidance so that the needle tip ultimately rests in the hyperechoic fascial cleft between the flexor carpi ulnaris and flexor

digitorum profundus muscles. This will place the needle tip proximity to the ulnar nerve just below the antecubital fossa (Fig. 54.11). When the tip of needle is thought to be in satisfactory position, after careful aspiration, a small amount of local anesthetic and steroid is injected under real-time ultrasound guidance to confirm that the needle tip is in the proper position. After proper needle tip placement is confirmed, the remainder of the contents of the syringe is slowly injected. There should be minimal resistance to injection.