The repair technology of peripheral nerve injuries has made great progress, but the simultaneous repair and promotion of nerve regeneration in multiple distal nerves remains a challenging task. The current cylindrical nerve conduits are unsuitable for nerve transposition repair. This study aims to assess the effect of conical chitosan conduits (different inner diameters at both ends) on nerve transposition repair, in conjunction with methylcobalamin (MeCbl).

In this study, a conical chitosan conduit was used to bridge a 2 mm defect between the proximal common peroneal nerve and distal tibial nerve and common peroneal nerve in rats. Additionally, we administered MeCbl at various concentrations to evaluate post-surgical adjuvant treatment effect. At 16 weeks post-surgery, gait analysis, electrophysiology testing, transmission electron microscopy (TEM) observation, toluidine blue staining, immunofluorescence staining, muscle wet weight determination and Masson’s trichrome staining were performed to assess nerve regeneration and reinnervation of gastrocnemius.

Gross observations did not reveal the formation of neuromas after bridging the distal nerves in each group. In terms of motor function (**p < 0.01), compound muscle action potential (CMAP) amplitude and latency (**p < 0.01), the quantity of regenerated nerve fibers, muscle fiber morphology and other parameters (**p < 0.01), 200 μg/kg MeCbl administration as a supplementary treatment had a significant positive impact compared to the chitosan conduit+normal saline (Chi/NS) group.

Our findings demonstrated that conical chitosan conduits combined with MeCbl can effectively promote nerve transposition repair following multiple distal nerve injuries.