Reconstruction of anorectal function through end-to-side neurorrhaphy by autonomic nerves and somatic nerve in rats

BackgroundEnd-to-side nerve repair is a new tool in managing certain nerve injuries. In previous studies, it was limited to somatic nerves. Herein, we evaluate the feasibility of anorectal reinnervation after end-to-side coaptation of autonomic nerve to somatic nerve.Materials and methodsForty adult male Sprague-Dawley rats were randomly divided into three groups: end-to-side coaptation group (n = 16), the left L6 and S1 spinal nerves were transected, and the distal stump of L6 ventral root (L6VR) was sutured to L4VR (L4VR) through end-to-side neurorrhaphy; no coaptation group (n = 12), rats received the same operation as the end-to-side coaptation group but without coaptation; and control group (n = 12), rats received the same operation as the end-to-side coaptation group but the L6VR was preserved. At 16 wk, using double retrograde tracing and histomorphological technique and anorectal manometry, morphological and functional properties of regenerated nerve were investigated.ResultsRetrograde tracing indicated that the new neural pathway was established and the main nerve regeneration mechanism was axon collateral sprouting. Histology showed good axonal regeneration with end-to-side neurorrhaphy. The wet weight and morphology of left tibialis anterior muscles appeared no detrimental effect on donor nerve. Anorectal manometry showed good anorectal functional recovery.ConclusionsThese results suggest that the somatic motor axon ingrowth into autonomic nerve could be through collateral sprouting after end-to-side coaptation of autonomic nerve to somatic nerve. Our innovative technique of end-to-side coaptation may be of great value in anorectal reinnervation without functional impairment of the donor somatic nerve.