Anatomic Variations of the Upper Extremity: Effects on Ultrasound-Guided Peripheral Nerve Blockade

Peripheral nerve blockade provides many advantages in the perioperative period for surgery on the shoulder, elbow, wrist, or hand. Aberrant anatomic structures or anomalous courses of nerves may create challenging conditions for use of ultrasound to accurately guide needles for nerve blocks. This paper presents a review of such anomalies affecting the conduct of various peripheral nerve blocks in the upper extremity. A comprehensive literature review was performed, utilizing the PubMed and Embase databases. Variations of anatomy of the brachial plexus and associated structures are described, as well as aberrancies of distal nerves in the upper extremity. These include descriptions of anatomic variations at the sites of interscalene, supraclavicular, infraclavicular, and axillary brachial plexus blocks, as well as nerve blocks at the level of the elbow and forearm. Understanding variant anatomy is essential for those providing upper extremity ultrasound-guided peripheral nerve blockade.