Relationship of the uterosacral ligament to the sacral plexus and to the pudendal nerve.

We describe the anatomy of the uterosacral ligament with respect to the sacral plexus. In six adult female embalmed cadavers, we identified the uterosacral ligament and its lateral nerve relations. Using the ischial spine as the starting point and measuring along the axis of the uterosacral ligament, we noted that the S1 trunk of the sacral plexus passes under the ligament 3.9 cm [95% confidence interval (CI), 2.1-5.8 cm] superior to the ischial spine. The S2 trunk passes under the ligament at 2.6 cm (95% CI; 1.5, 3.6 cm), the S3 trunk passes under the ligament at 1.5 cm (95% CI; 0.7, 2.4 cm), and the S4 trunk passes under the ligament at 0.9 cm (95% CI; 0.3, 1.5 cm) superior to the ischial spine. The pudendal nerve forms lateral to the uterosacral ligament. Our data demonstrate that the S1-S4 trunks of the sacral plexus, not the pudendal nerve, are vulnerable to injury during uterosacral ligament suspension.