Comparison of the performance of chronically versus freshly denervated autograft in nerve repair

Abstract

Purpose: Graft choice is one of the few variables over which the surgeon has control when reconstructing nerve gaps. Because repair of chronically denervated nerves generally yields inferior recovery, we hypothesized that the use of chronically denervated nerve tissue as a graft source may compromise axonal regeneration and clinical results.

Methods: A total of 45 immature female Sprague-Dawley rats underwent transection of one peroneal nerve before being divided into 3 experimental groups: group A (n = 15) had acutely denervated nerve graft, group B (n = 15) had 2-month denervated nerve graft, and group C (n = 15) had 4-month denervated nerve graft. We included 10 additional rats as a sham group. After 2 months, groups A and B underwent removal of 1 cm of the contralateral peroneal nerve. For group A, this section of nerve was immediately sutured back in place to serve as a model for acute denervation. For group B, the defect was repaired with a 1-cm graft from the distal stump of the previously transected (denervated) peroneal nerve. Group C underwent the same procedure as group B, but after an additional 2 months. After 8 weeks of regeneration time, the 3 experimental groups and the sham group underwent testing. We assessed twitch contraction forces of the reinnervated extensor digitorum longus before we harvested the muscle belly for morphologic measurements. Histological nerve tissue evaluation assessed axonal regeneration.

Results: We detected no statistical differences for mean muscle contraction strengths between the experimental groups; nevertheless, the reinnervated extensor digitorum longus muscle bellies from the 4-month denervated nerve graft group were statistically smaller than muscles from the other 2 experimental groups (p < .05). Axon counts decreased, whereas axon diameters increased in direct correlation with the length of time of graft denervation (p < .05). No difference in axon myelination was found between experimental groups.

Conclusions: Prolonged denervation of nerve graft material compromised both axon and reinnervated muscle recovery in this rodent model.