Introduction and indications: The posterior approach to the roots of the brachial plexus was originally described by Kappis¹ in 1923, who argued that a posterior approach was safest because the carotid, internal jugular, vertebral vessels, sympathetic ganglia, phrenic, and recurrent laryngeal nerves are located anterior to the brachial plexus. Studies by Sandefo et al.² and Pere et al.³ showed an overall success rate of 97%, including 100% block of the axillary and radial nerves, 97% block of the median and musculocuTaneous nerves, and 68% block of the ulnar nerve. They also showed a 0.5% phrenic nerve block compared to the near 100% rate of phrenic nerve block with the lateral approach and only a 7% superior sympathetic ganglion block. The technique was little used before it was revised by Pippa et al.⁴ in 1990 and again by Boezaart⁵ in 2003 with modifications to make it less painful by directing the needle between muscle groups. The block is used for surgery of the shoulder and proximal arm when an indwelling catheter disTant from the surgical site is desired.

Anatomy: The brachial plexus is composed of the ventral roots of spinal nerves C5-T1. The roots exit the lateral foraminal spaces and pass between the anterior and middle scalene muscles to innervate the upper limb (Fig. 15.1). At the root level, the fascicles are surrounded by dura/perineurium. Within the perineurium, there is little or no stroma, so care must be taken to not position the needle within the nerve root itself. For this reason, the authors recommend using an 18G Tuohy needle even for single-injection techniques. The carotid artery and jugular vein should be identified as well to prevent their puncture (Fig. 15.2).

Patient position: Sitting or lateral decubitus.

Transducer: Linear (25 or 38 mm) oscillating at 13 MHz. Curved (11 mm) oscillating at 10 MHz.

Transducer orientation: Transverse, over the sternocleidomastoid at the level of the thyroid cartilage.