Optimized Contraleteral C7 Transfer: An Experimental Study

The authors' experimental work has shown that contralateral C7 can be used to neurotize more than one recipient nerve due to its abundant number of nerve fibers. The objective of this reported study was to determine which are the optimal neurotization combinations.

One hundred five adult Sprague-Dawley rats were randomized into seven groups. Total brachial plexus root avulsion was created on the left side. Contralateral C7 transfer was done using several novel surgical designs. These included using a pedicled ulnar nerve as a graft and splitting the proximal end of the nerve into two bundles, suturing one to the median nerve and the other to the musculocutaneous nerve or radial nerve. The other combinations included using both pedicled ulnar nerve and two cables of sural nerve to bridge the contralateral C7 to the recipient nerves, viz., the median and musculocutaneous nerves, or the median and radial nerves. Conventional contralateral C7 transfer to a single nerve served as control. Postoperative evaluations were conducted at 2, 3, and 6 months. Electromyography, muscle physiologic testing, muscle histology, and neuromorphometry were carried out to measure maximum amplitude of compound muscle action potentials (CMAPs), twitch, and tetanic tensions of the target muscles, cross-sectional area, and wet weight of the target muscles, and the number of regenerating myelinated nerve fibers.

As for the median nerve, favorable recovery was seen, in descending order, when the median nerve was neurotized with the musculocutaneous nerve via both ulnar nerve and sural nerve grafts; when the median nerve was neurotized with the musculocutaneous nerve via ulnar nerve graft only; and when the median nerve was neurotized with the radial nerve. As for the musculocutaneous nerve, results were better when the nerve was neurotized with the median nerve via both ulnar nerve and sural nerve grafts than when it was neurotized with the median nerve via ulnar nerve graft only. As for the radial nerve, no difference was found when it was neurotized with the median nerve via both ulnar nerve and sural nerve grafts or via ulnar nerve graft only. Recovery of the radial nerve was slightly inferior to that of the median nerve or the musculocutaneous nerve.

The contralateral C7 can neurotize two nerves simultaneously. The best combination and design is C7 transfer to the median nerve and the musculocutaneous nerve via both ulnar and sural nerve grafts.