Muscular Branch of Axillary Nerve to Deltoid Muscle

Origin

The muscular branch of axillary nerve to deltoid muscle arises from the anterior (and sometimes posterior) branch of axillary nerve. It contains motor neurons which come from the C5 and C6 cervical spinal roots.

Course

The axillary nerve, which originates from the posterior cord of brachial plexus, curves back inferior to the glenohumeral articular capsule, and traverses through the quadrangular space bounded above by subscapularis and teres minor muscles. Here the axillary nerve divides into anterior and posterior branches, which provide motor innervation to deltoid and teres minor muscles (Zhao et al., 2001; Loukas et al., 2009).

The most consistent innervation for the deltoid muscle arises from the anterior branch. It contains all fibers which innervate to the anterior and middle deltoid muscle. This branch curves around the neck of the humerus along with the posterior circumflex humeral vessels, deep to the deltoid. The anterior branch reaches the anterior border of the muscle and innervates the deltoid, before the terminal ramification of the anterior branch into few small cutaneous branches.

In 90% of cases, the posterior aspect of the deltoid muscle receives motor innervation from the posterior branch of axillary nerve, which courses medially and posteriorly along the attachment of the lateral head of triceps. It lies medial to the anterior branch in the quadrangular space and ends by dividing into the nerve to teres minor and the upper lateral cutaneous nerve of the arm, at the lateral edge of the origin of the long head of triceps.

Branches

There are no named branches.

Supplied Structures

The muscular branch of axillary nerve to deltoid muscle provides motor innervation to deltoid muscle.

List of Clinical Correlates

—Axillary nerve lesion

References

Loukas, M., Grabska, J., Tubbs, R. S., Apaydin, N. and Jordan, R. (2009) 'Mapping the axillary nerve within the deltoid muscle', Surg Radiol Anat, 31(1), pp. 43-7.Zhao, X., Hung, L. K., Zhang, G. M. and Lao, J. (2001) 'Applied anatomy of the axillary nerve for selective neurotization of the deltoid muscle', Clin Orthop Relat Res, (390), pp. 244-51.