Spinal nerve composition and innervation of the axillary nerve.

Introduction: The purpose of this study was to evaluate the spinal nerve composition of the axillary nerve and the contribution of each spinal nerve.

Methods: Thirty brachial plexi extracted from Korean adults (15 men, 14 women, 1 unknown; left side, 13; right side, 17) were examined in this study.

Results: The frequency of the contribution of C4 was 13.3%, and it was mainly innervated the deltoid and teres minor muscles. The frequency of inclusion of C7 was 20.0%. C7 fibers were mainly involved in the deltoid and cutaneous branches. The axillary nerve was primarily composed of fibers from C5 and C6 in 66.6%; C4, C5, and C6 in 13.3%; and C5, C6, and C7 in 20.0%.

Conclusions: These findings may be helpful to diagnose damage to axillary nerve structures that occur in such injuries as humerus fractures.