The internal topography of the axillary nerve: an anatomic and histologic study as it relates to microsurgery.

The topography of the fascicular groups of the axillary nerve throughout its course from the posterior cord until its passage through the quadrangular space was studied in dissections of 40 brachial plexuses under x3.5 loupe magnification. Additionally, 10 axillary nerves were excised in toto, and histologic serial sections were done to define fascicular arrangement. In all specimens, the motor fascicular group for the deltoid muscle was located most superiorly at the level of the quadrangular space. This motor portion could be identified as a distinct entity, up to 45 mm proximal to this level. In surgical treatment of axillary nerve repair, one should direct special attention to the correct identification, matching, and alignment of this motor fascicle, to avoid wasteful regeneration of axons into the functionally unrelated fascicles to the teres minor and the lateral shoulder skin.