In this chapter, the authors discuss the macro- and microanatomy of the
brachial plexus cords below the clavicle. The area below the clavicle is defined, for the
purposes of this discussion, as the area from just below the clavicle - the proximal
infraclavicular area, to the lateral border of the major pectoral muscle and the
deltopectoral groove – the distal infraclavicular area. In the proximal infraclavicular
area, the three cords are situated lateral to the axillary artery and vein and all three cords
are in a communal circumneural (paraneural) sheath. As the cords track more distally,
they spread out around the artery so that the three cords are apart and each is in its own
circumneural sheath. The lateral cord is now anterolateral, the medial cord is
anteromedial, and the posterior cord is posterior to the axillary artery.
Keywords: Ansa pectoralis, Axillary artery, Axillary vein, Brachial plexus, Brachial
plexus sheath, Circumneural sheath, Deltopectoral groove, Epineurium,
Infraclavicular block, Lateral cord, Lateral pectoral nerve, Macroanatomy, Major
pectoral muscle, Marti-Gruber, Medial cord, Medial pectoral nerve, Microanatomy,
Minor pectoral muscle, Paraneural sheath, Posterior cord, Secondary block.
