Posterior Cord of the Brachial Plexus, Anterior View

Description

Prominent in the anterior shoulder and axillary region, the posterior cord of the brachial plexus lies posterior to the second part of the axillary artery and forms where the posterior divisions of the superior, middle, and inferior trunks converge. From this cord, the axillary nerve courses laterally toward the quadrangular space, while the radial nerve continues inferiorly and posteriorly toward the arm, typically passing behind the humeral shaft in the radial groove. Shorter branches are also expected near the cord, including the upper and lower subscapular nerves and the thoracodorsal nerve, which run toward subscapularis, teres major, and latissimus dorsi respectively. Surrounding landmarks in this anterior exposure include the clavicle superiorly, the coracoid process and scapular neck laterally, and the pectoralis major and minor forming the anterior muscular plane over the neurovascular bundle. A tight corridor. This anterior perspective matters because it mirrors the surgical and procedural window used to orient the cords relative to the axillary artery during axillary exploration, lymph node dissection, and infraclavicular brachial plexus block. The posterior cord’s position behind the artery explains why posterior cord sparing or incomplete blockade can occur when local anesthetic pools anteriorly, and why aggressive retraction or hematoma in the axilla can preferentially compromise radial and axillary nerve function. Clinically, traction injuries of the plexus and iatrogenic injury during shoulder stabilization procedures often declare themselves through deltoid weakness and loss of sensation over the regimental badge area (axillary nerve) or wrist and finger extension deficits (radial nerve). Use this artwork in gross anatomy and neuroanatomy teaching to map divisions, cords, and terminal branches, and in anesthesia or upper limb surgery resources to illustrate needle target zones and safe tissue planes around the axillary artery. It also fits orthopedic and trauma publications discussing brachial plexopathy patterns, posterior cord lesions, and their motor and sensory findings. Anatomical accuracy verified by SciePro's Medical Advisory Board.