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INTRODUCTION

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The neural innervations of the upper extremity provide unique opportunities for a wide selection of neural blockade options that can be tailored to the desired outcome needed for anesthesia or analgesia of the extremity.

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GROSS ANATOMY

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The brachial plexus traverses the posterior triangle of the neck and the axilla. It provides complete innervation to the upper extremity. Proximally, the brachial plexus originates from the ventral primary rami of the cervical spinal nerves (C5–T1) (Figs. 2–1 and 2–2) and extends from the cervical spinal roots in the neck to its terminal nerves in the axilla (Fig. 2–3). The C5 and C6 rami unite to form the superior trunk, the C7 rami forms the middle trunk, and the C8 and T1 rami unite to form the inferior trunk (Fig. 2–4). The trunks of the brachial plexus are located in the interscalene groove between the scalenus anterior and the scalenus medius muscles, at the level of the cricoid cartilage (approximate C6 vertebral body level) and deep to the sternocleidomastoid muscle (Fig. 2–5). The anterior tubercle of the C6 vertebra is the most prominent of all the vertebrae (Chassaignac's tubercle), and the C7 transverse process lacks the anterior tubercle. This feature can be used to sonographically identify the C7 nerve root. At the root level, the plexus gives off the dorsal scapular nerve and the long thoracic nerve (Fig. 2–4).

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FIGURE 2–1

Anatomical illustration showing the formation of the brachial plexus. The roots, trunks, and divisions of the brachial plexus have been represented using different colors to illustrate the formation of the cords and the terminal branches of the plexus.

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FIGURE 2–2

A magnetic resonance neurography (MRN) image of the brachial plexus showing the formation of the brachial plexus in a healthy young volunteer.

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FIGURE 2–3

Brachial plexus. Note the formation of the plexus and the relation of the nerve roots to the transverse process of the cervical vertebra.

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FIGURE 2–4

The brachial plexus and relation of its components to the subclavian and axillary artery.

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FIGURE 2–5

Brachial plexus and its relation to the scalene muscles. Note how the brachial plexus is sandwiched between the anterior and middle scalene muscles.

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At the supraclavicular fossa, the trunks of the brachial plexus are superficial and divide into their anterior and posterior divisions and reunite as the cords distal to the clavicle. The trunks and divisions lie above the first rib between the scalenus ...

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