Nerve transfer to deltoid muscle using the nerve to the long head of the triceps, part I: an anatomic feasibility study.

PURPOSE: To experimentally evaluate the feasibility of restoring the motor function of the deltoid muscle in patients with complete C5-C6 root injury (upper brachial plexus injury) by transferring the nerve to the long head of the triceps to the anterior branch of the axillary nerve through a posterior approach.

METHODS: The study was performed on shoulder girdles of 36 formalin-embalmed cadavers. The number, diameter, and length of the branches of the axillary nerve at the level of the quadrilateral space were noted. The length and diameter of the nerves to the long head and to the lateral head of triceps at the level of triangular space were recorded. The distances from the acromion angle to the bifurcation of the anterior branch of the axillary nerve, to the origins of the nerve to the long head, and to the origin of the lateral head of the triceps were recorded as well. Nerve biopsy specimens of the axillary nerve and the nerve to the long head of the triceps were obtained from 6 fresh cadavers for histomorphometric evaluation.

RESULTS: The average length of the anterior branch of the axillary nerve in this study, measured from the quadrilateral space to the innervating site, was 44.5 mm (range, 26-62 mm), and the average length of the nerve to the long head of triceps, measured from its origin to the innervating site, was 68.5 mm (range, 30-69 mm). The average diameter of the anterior branches of the axillary nerve and the nerve to the long head of the triceps were 2.1 and 1.1 mm, respectively. The average number of axon fibers in the anterior branch of the axillary nerve was 2,704 and in the nerve to the long head of the triceps was 1,233.

CONCLUSIONS: Using the acromial angle as the landmark, the combined length of the two 2 nerves was longer than the distance between them. The diameter, the number of axons, and the anatomic proximity of the nerve to the long head of the triceps make it a potential source for reinnervation of the anterior branch of the axillary nerve by direct nerve transfer without nerve grafting through posterior approach for the management of upper brachial plexus injuries.