Specificity of motor axon regeneration: a comparison of recovery following biodegradable conduit small gap tubulization and epineurial neurorrhaphy.

Functional recovery is often unsatisfactory after lesions in the peripheral nervous system despite the strong potential for regeneration and advances in microsurgical techniques. Axonal regeneration in mixed nerve into inappropriate pathways is a major contributing factor to this failure. In this study, the rat femoral nerve model of transection and surgical repair was used to evaluate the specificity of motor axon regeneration as well as functional and morphological recovery using biodegradable conduit small gap tubulization compared to epineurial neurorrhaphy. 12 weeks after nerve repair, the specificity was assessed using the retrograde neurotracers TB and DiI to backlabel motor neurons that regenerate axons into muscle and cutaneous pathways. To evaluate the functional recovery of the quadriceps muscle, the quadriceps muscle forces were examined. The quadriceps muscle and myelinated axons were assessed using electrophysiology and histology. The results showed that the specificity of motor axon regeneration (preferential reinnervation) was significantly higher when the nerve transection was treated by biodegradable conduit small gap tubulization and there was no significant difference between the two suture methods with respect to the functional and morphological recovery. This study demonstrated that the quicker and easier biodegradable conduit small gap tubulization may get more accurate reinnervation than traditional epineurial neurorrhaphy and produced functional and morphological recovery equal to traditional epineurial neurorrhaphy.