Surgical anatomy of the presacral area

Abstract

Objective: L5-S1 instabilities can be fixated using minimally invasive presacral approach. The close relationship between the sacrum and neurovascular as well as intestinal structures may complicate the procedure during this approach. This requires knowledge regarding the normal anatomy of the presacral area to avoid the iatrogenic injuries. The aim of this study was to measure the distance between the sacrum and the structures anterior to it.

Materials and methods: The measurements were performed on ten cadavers fixed with formaldehyde and ten MR imaging studies on individuals without any pathology in the presacral area. The distances between the sacrum and the presacral structures (i.e., middle and lateral sacral arteries, sympathetic trunks, internal iliac arteries and veins, and colon/rectum) were measured.

Results: Cadaver study showed that the middle sacral artery was located on the right side in 55.0%, on the left side in 31.7%, and on the midline in the 13.3% of cases. The distance between the sacral midline and middle sacral artery was found to be 8.0 +/- 5.4, 9.0 +/- 4.9, 8.7 +/- 6.0, 8.6 +/- 6.4, and 4.7 +/- 5.0 mm at the levels of S1-2, S2-3, S3-4, S4-5, and S5-coccyx, respectively. The distance between the sacral midline and the sympathetic trunk ranged between 22.4 +/- 5.8 and 9.5 +/- 3.2 mm in different levels between S1 and coccygeal level. The study also showed that the distance between the posterior wall of the intestine (colon/rectum) and the ventral surface of the sacrum can be as close as 11.44 +/- 7.69 mm on MR images.

Conclusion: This study showed that there was close distance between the sacral midline and the structures anterior to it. The close relationships, as well as the potential for anatomical variations, require the use of sacral and presacral imaging before presacral approach.