The upper brachial plexus defect model in rhesus monkeys: a cadaveric feasibility study

To establish a model for nerve grafts and determine the anatomic characteristics of the brachial plexus in rhesus monkeys. Ten specimens of the brachial plexus were obtained from five rhesus monkey cadavers. Anatomic dissection of the brachial plexus was systemically performed. The length of each root, trunk, and each division was measured using a Vernier caliper proximodistally. The anatomic distributions of the suprascapular, axillary, and musculocutaneous nerve were documented. The brachial plexus of rhesus monkeys included the spinal nerves or roots of C5, C6, C7, C8, and T1 (80%, 8/10), with a small contribution from the C4 root (20%, 2/10) occasionally. The upper trunk was not measurable because of their irregular structures. The lower trunk had a mean length of 1.62 (range, 0.96-2.1 mm) and a mean diameter of 2.29 (range, 1.9-2.94 mm). For the upper trunk, the C5 and C6 roots either divided into two very short divisions or sent out very long divisions before they joined together. For the middle trunk, the C7 root had a straight course after leaving the foramen and blended imperceptibly into the middle trunk before dividing into the anterior and posterior divisions. The lower trunk was noted in almost all the specimens (80%, 8/10), which was formed by C8 and T1. The brachial plexus in rhesus monkeys varies from that of humans, and defects can be made at the level of C5 and C6 roots and the C7 root should also be cut off and ligated.