Anatomic variations of the pelvic floor nerves adjacent to the sacrospinous ligament: a female cadaver study.

Our objective was to document variations in the topography of pelvic floor nerves (PFN) and describe a nerve-free zone adjacent to the sacrospinous ligament (SSL). Pelvic floor dissections were performed on 15 female cadavers. The course of the PFN was described in relation to the ischial spine (IS) and the SSL. The pudendal nerve (PN) passed medial to the IS and posterior to the SSL at a mean distance of 0.6 cm (SD = +/-0.4) in 80% of cadavers. In 40% of cadavers, an inferior rectal nerve (IRN) variant pierced the SSL at a distance of 1.9 cm (SD = +/-0.7) medial to the IS. The levator ani nerve (LAN), coursed over the superior surface of the SSL-coccygeus muscle complex at a mean distance of 2.5 cm (SD = +/-0.7) medial to the IS. Anatomic variations were found which challenge the classic description of PFN. A nerve-free zone is situated in the medial third of the SSL.