Applied anatomy of the axillary nerve for selective neurotization of the deltoid muscle.

Morphologic and internal topographic features of the axillary nerve were studied in 40 cadaveric shoulders to provide anatomic data for selective neurotization of the deltoid muscle in axillary nerve injury. The axillary nerve can be divided into three segments. Proximal to the subscapularis muscle, the axillary nerve is a single nerve trunk. Nerve fascicles to the deltoid muscle are identified at its lateral part. In front of the subscapularis muscle, the axillary nerve forms into the lateral and medial fasciculi groups. Distal to the subscapularis muscle, the nerve divides into anterior and posterior branches, which are continuations of the lateral and medial fasciculi groups, respectively. The anterior branch contains all fibers that innervate to the anterior and middle deltoid muscle. In 90% of cases, the posterior branch contains part or all nerve fibers to the posterior deltoid muscle. Nerve fibers to the teres minor and cutaneous sensory fibers are found in the posterior branch. In neurotization of the deltoid muscle, the best approach is to match the donor nerve to the lateral fasciculi group, which will give the highest percentage of reinnervation of the deltoid muscle.