A NEW ANIMAL-MODEL TO INVESTIGATE AXONAL SPROUTING AFTER END-TO-SIDE NEURORRHAPHY

End-to-side neurorrhaphy is a technique that may provide a solution fo r the problem of distal target reinnervation without injury to the ori ginal donor nerve. The technique drew extensive attention after Viterb o reported his experiments in 1992; however, to date, the animal model s used to elucidate the process of lateral axon sprouting had the disa dvantage of substantial injury to the donor nerve, raising questions a bout the origin of axons reinnervating the nerve graft. In this report , a new model in the rat is introduced, in which the donor nerve is no t damaged and an additional target can be innervated via a nerve graft . The saphenous nerve represents the axonal conduit; the proximal end is coapted end-to-side to the sciatic nerve at the site of a perineuri al window. The distal end is passed through the adductor muscles and c oapted distally in an end-to-end fashion with the obturator nerve. In one group, a partial neurectomy was performed at the site of coaptatio n, which led to a lower Sciatic Functional index (SFI). In the second group, the creation of a perineurial window yielded a normal SFI after end-to-side neurorrhaphy. Compared to the partial neurectomy group, t he perineurial window end-to-side neurorrhaphy resulted in significant ly less axons in the graft. The new model has the following advantages : (a) minimal injury to the donor nerve; (b) provision of a single add itional target (gracilis) whose functional recovery can be assessed mo rphologically and behaviorally; (c) an opportunity to understand later al sprouting by providing a non-injury model in which axonal invasion of the graft can originate from nodal axonal outgrowth; and (d) establ ishment of a noninjury model that can have widespread clinical applica tions.