Anal Sphincter Reconstruction Using a Transposed Gracilis Muscle With a Pudendal Nerve Anastomosis: A Preliminary Anatomic Study

PURPOSE: Few studies have demonstrated the feasibility of cross innervating a skeletal muscle neosphincter with the pudendal nerve in an animal model. This study was designed to evaluate in humans the technical feasibility of anastomosing the nerve of the gracilis muscle and the pudendal nerve when the gracilis muscle is transposed around the anus. METHODS: Anatomic assessment was made in 30 cases. The gracilis muscle and its principal neurovascular pedicle were dissected and the nerve to the gracilis divided at its origin. The gracilis muscle, accompanied by its nerve, was then transposed around the anus. The pudendal nerve was dissected in its extrapelvic portion and divided at its termination. Gracilis reinnervation was considered feasible when the proximal end of the nerve to the gracilis muscle and the distal end of the pudendal nerve were able to be placed into tension-free contact. RESULTS: The mean lengths of the nerve to the gracilis and the pudendal nerve were 126.5 ± 20.6 mm and 57.5 ± 16.3 mm. Anastomosing the nerve of the gracilis muscle and the pudendal nerve was possible in 28 cases. There was a total mean surplus nerve length of 25.1 ± 20.9 mm. In 26 cases, the distal end of the pudendal nerve (mean, 3.3 ± 1.1 mm) was similar or larger than the end of the nerve to the gracilis (mean, 3 ± 0.8 mm). CONCLUSIONS: Anal sphincter reconstruction using transposed gracilis muscle with pudendal nerve anastomosis is anatomically achievable in cadavers, and supports the potential applications of this technique for perineal reconstruction in clinical practice.