A Heterotopic Autoinnervated Urinary Neosphincter

Twenty-six female adult New Zealand white rabbits underwent surgical denervation of a gracilis muscle to study the possibility of developing an autologous neosphincter innervated by the pudendal nerve. The study was conducted in 2 phases. In both Phase I and Phase II, the study group had the motor nerve to the gracilis, a branch of the obturator nerve and the pudendal nerve coapted in the perineum. The control group was left denervated. In Phase I, all muscle flaps were wrapped around the urogenital sinus. In Phase II, the muscle flaps were returned to their anatomic location.With bulbocavernosus reflex testing, 89 percent of the reinnervated group and 60 percent of the denervated group from Phase I and 86 percent of the reinnervated group and none of the denervated group from Phase II had a contractile response in the muscle flap. In Phase II, histologic examination of the gracilis muscle was suggestive of an early change in muscle myofiber physiology from fast twitch to slow twitch in the reinnervated group only.In the rabbit, a transplanted vascularized muscle flap, cross-innervated by the pudendal nerve has a reproducible response to bulbocavernosus reflex testing. This suggests that a transplanted muscle might be able to assume some of the characteristics of the voluntary urinary sphincter. The rabbit is a useful model in which to investigate the potential of the heterotopic neosphincter.