Presacral Space Surgical Anatomy: Piriformis Fascia as Lateral Border

Safe surgery requires an understanding of the anatomic boundaries and neurovascular structures of the presacral space.

The aim of the study was to characterize anatomy of the presacral space applicable to sacrocolpopexy or rectopexy while highlighting cadaveric findings of the lateral border of the space.

Structures and boundaries of the presacral space of 18 unembalmed female cadavers were studied. Anatomic relationships and distances to landmarks were established.

A dense connective tissue layer ≤1 mm thick on the piriformis muscle's medial surface attaches to the anterior sacrum just medial to the sacral foramina, separating the lateral sacral vein and sacral nerves laterally from the presacral space contents medially. Median transverse distance from midsacral promontory to right sympathetic trunk was 19.5 (range, 15-31) mm. Distances from right S1, S2, S3, and S4 foramina to midsacral promontory were 28.8 (22-47.5), 48.3 (38.5-72.5), 65.8 (54.5-89.5), and 80.8 (65-104.5) mm and to midline sacrum were 16.5 (14-22), 15.3 (13-20.5), 13.5 (10.5-19.5) and 13.3 (10.5-19.5) mm, respectively. Transverse communicating veins, measuring 3 (2-4) mm in width, penetrated the piriformis fascia, joining the lateral sacral vein to form the sacral venous plexus. Vertical distance from midsacral promontory to the most cephalad communicating vein was 38.3 (7.5-60.5) mm.

During presacral space surgical procedures, avoiding suture placement and mesh fixation beyond 1.5 cm from the sacrum midline should prevent injury to the sacral sympathetic trunk, sacral nerves, and lateral sacral vein. Transverse communicating vessels of the sacral venous plexus are usually encountered below the S1 foramina level. The piriformis fascia is the lateral boundary of the presacral space over the greater sciatic foramen.