]> 2026-07-31T07:52:10+00:00 WBR0550 0 en A Point A indicates Erb’s point, the union of the C5 and C6 roots of the brachial plexus. B Point B represents the posterior cord of the brachial plexus, which gives rise to the axillary and radial nerves. While posterior cord injury would cause weakness of the deltoid muscle through loss of axillary nerve fibers, the patient would most likely exhibit additional symptoms arising from loss of radial nerve function, such as wrist drop. C Point C represents the axillary nerve, which is classically injured in fractures near or at the surgical neck of the humerus. The axillary nerve innervates the deltoid muscle, which is responsible for abduction of the arm beyond 15 degrees. D Point D represents the radial nerve. The radial nerve can be injured in conditions such as “Saturday night palsy”, in which the patient typically exhibits weakness of the wrist extensors. E Point E represents the union of the C8-T1 roots of the brachial plexus. This area can be injured in Klumpke palsy, causing a total claw deformity of the hand due to lumbrical dysfunction. Anatomy C Musculoskeletal/Rheumatology 2020-10-28T00:56:07Z 2459150.5389699 WBR0550