Ultrasound-guided radial nerve block at the elbow is useful in the management of the pain subserved by the radial nerve. This technique serves as an excellent adjunct to brachial plexus block and for general anesthesia when performing surgery at the elbow or below. Ultrasound-guided radial nerve block at the elbow with local anesthetic may be used to palliate acute pain emergencies, including postoperative pain, pain secondary to traumatic injuries of the radius, and cancer pain, while waiting for pharmacologic, surgical, and antiblastic methods to become effective (Fig. 52.1).

Ultrasound-guided radial 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 radial nerve is being considered or when there is a possibility that the nerve may be sacrificed during surgeries in the anatomic region of the radial nerve at the level of the humerus. This technique may also be useful in those patients suffering symptoms from compromise of the radial nerve due to compression of the radial nerve by tumor, ganglion, or aberrant muscles or fascial bands. Ultrasound-guided radial nerve block at the elbow may also be used to palliate the pain and dysesthesias associated with stretch injuries to the radial nerve.

The key landmark when performing ultrasound-guided radial nerve block at the elbow is the point at which the radial nerve is just above the point within the substance of the brachioradialis muscle where the radial nerve bifurcates (Fig. 52.2). Arising from fibers from the C5-T1 nerve roots of the posterior cord of the brachial plexus, the radial nerve passes through the axilla lying posterior and inferior to the axillary artery. As the radial nerve exits the axilla, it passes between the medial and long heads of the triceps muscle and then curves across the posterior aspect of the humerus, giving off a motor branch to the triceps muscle. Continuing its downward path, the radial nerve gives off a number of sensory branches to the upper arm as it travels in the intermuscular septum separating the bellies of the brachialis and brachioradialis muscles (Fig. 52.3). The nerve passes into the substance of the brachioradialis muscle, and at a point just above the lateral epicondyle, the radial nerve divides into deep and superficial branches; the superficial branch continues down the arm along with the radial artery to provide sensory innervation to the dorsum of the wrist and the dorsal aspects of a portion of the thumb and index and middle fingers, and the deep branch provides the majority of the motor innervation to the extensors of the forearm (Figs. 52.4, 52.5 and 52.6).

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 elbow flexed to about 100 degrees and the forearm resting comfortably across the patient’s abdomen (Fig. 52.7). The physician stands at the side of the patient. With the patient in the above position, at a point ˜2½ inches above the lateral epicondyle, a highfrequency linear ultrasound transducer is placed in a transverse position over the lateral aspect of the humerus, and an ultrasound survey scan is taken (Fig. 52.8). The hyperechoic margin of the humerus is then identified with the radial nerve lying adjacent to the humerus (Fig. 52.9). After the radial nerve has been identified in proximity to the humerus, the ultrasound transducer is slowly moved inferiorly toward the antecubital fossa. The radial nerve will be seen to move away from the humerus and into the substance of the brachioradialis muscle (Fig. 52.10). The skin overlying the area beneath the ultrasound transducer is then prepped with antiseptic solution. A sterile syringe containing 3.0 mL of 0.25% preservative-free bupivacaine and 52 mg of methylprednisolone is attached to a 1½-inch, 22-gauge needle using strict aseptic technique. The needle is placed through the skin just below the inferior border of the transducer and is then advanced using an in-plane approach with the needle trajectory adjusted under real-time ultrasound guidance so that the needle tip ultimately rests in proximity to the radial nerve as it lies within the substance of the brachioradialis muscle (Fig. 52.11). When the tip of the

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 are slowly injected. There should be minimal resistance to injection.