Anatomical basis of the variable aspects of injuries of the axillary nerve (excluding the terminal branches in the deltoid muscle)

The course of the axillary n. is complex with three points of angulation that may be used to delineate four segments and a fifth segment that corresponds to the intramuscular ending of the nerve in the deltoid m. The purpose of this study was to determine the precise anatomy of the nerve and of its branches, and some morphologic features for each segment. Thirty-two shoulders from embalmed adult cadavers have been studied. The axillary n. was divided in five segments: from its origin to the inferior border of the subscapularis m.,from the subscapularis m. to the anterolateral border of the tendon of the long head of the triceps brachii m.,from the triceps to the posteromedial part of the surgical neck of the humerus,from the humerus to the entry into the deltoid m.,the intramuscular distribution of the nerve in the deltoid m.