Functional, electrophysiologic, and morphometric evaluation of nerve regeneration from coaptation on regenerated nerve fibers: experimental study in rabbits.

The importance of a sufficient number of nerve fibers at a proximal coaptation site is indisputable for the successful repair of nerves; however, the quality of nerve fibers required at this site has yet to be defined. The present study deals with the question of whether it is necessary to trim nerves back to unaffected neuronal tissue or whether the coaptation on recently regenerated nerve fibers, commonly believed to produce a poor quality of repair can, in fact, produce adequate nerve regeneration. Twenty New Zealand White rabbits received a standardized crush lesion on the peroneal nerves of both hind legs. Four weeks later, the nerves of the left hind legs (n = 20) were transected 10 mm distal to the previous crush lesion and coapted to the freshly regenerated nerve fibers. For comparison, on 10 right hind legs, the nerves were transected at the site of previous crushing (Group A, superimposition) or 10 mm proximal to the site of crushing on unscathed nerve fibers (Group B). Eleven weeks later, the quality of nerve regeneration was assessed by the toe-spreading reflex, electrophysiologic data, muscle weight, and histomorphologic evaluation. In the animals of Group A, the quality of nerve regeneration following coaptation on the regrown axons did not differ in any of the examined parameters from the quality of nerve fibers outgrown from the site of the superimposed lesion. Both lesions led to a completely functional reinnervation. Also in Group B, nerve action potential recording and histologic data on both sides did not reveal a significant difference between the number and maturation of nerve fibers equidistant from the suture site, shortly before muscle entrance. With this coaptation model, it could be demonstrated in the peroneal nerve of rabbits, that coaptation to recently regenerated nerve fibers leads to a significant functional regeneration.