Applied anatomy for upper limb nerve blocks

The brachial plexus derives from C5, C6, C7, C8 and T1 nerves. It is made up of five roots, between the scalene muscles, three trunks (upper, middle and lower) lying in the posterior triangle, each of which divide into anterior and posterior divisions behind the clavicle to form lateral, medial and posterior cords in the upper axilla. The plexus gives rise to the definitive motor and cutaneous nerve supply to the upper limb. The plexus can be blocked by local anaesthetic infiltration at its root/trunk level in the fascial sheath compartment between the scalenes, or as it crosses the first rib. Block can also be performed around the axillary artery. Peripherally, the nerves may be blocked at the elbow, wrist or finger level.