A Long Peripheral Nerve Autograft Model in the Sheep Forelimb

Background Autologous nerve grafts remain the only proven means of bridging lengthy gaps in peripheral nerve. However, there is very little literature on a reliable long (> 5 cm) nerve autograft animal model. Objective To establish a reproducible long nerve gap and autograft animal model that is clinically relevant but not cost prohibitive. Methods The extent of nerve regeneration and electrophysiological recovery after segmental repair of a long nerve defect was evaluated with a sheep model. Thirteen Suffolk sheep were used. An 18-cm segment of radial sensory nerve was harvested from the forelimb, trimmed, divided into 2 equal segments of 7 cm each, and microsurgically repaired to a surgically created defect of 5 cm in the median nerve within the same forelimb. Electrophysiological studies were performed on 6 sheep at 6 months and 6 sheep at 9 months. Samples of the grafted segments were obtained for histology, immunohistochemistry, and morphometric analyses. Electric studies were also performed on an uninjured median nerve of a control animal in tissue that was similarly harvested and processed. Results At 6 and 9 months, all sheep had recordable robust nerve action potentials. Nerve conduction velocity and amplitude were slightly decreased compared with control, but the difference was statistically insignificant. Histomorphometric assessment demonstrated that the autografts contained a large number of regenerating axons through graft fascicles in all animals. Conclusion The median nerve in the sheep forelimb is a reproducible and reliable model for assessing regeneration through long peripheral nerve grafts.