An Anatomic Study of the Sacral Hiatus: A Basis for Successful Caudal Epidural Block

Abstract

An anatomic study of the sacral hiatus using isolated sacra. To clarify the anatomic variations of the sacral hiatus using the bony landmarks of the sacrum for improving the reliability of caudal epidural block (CEB). The CEB has been widely used for the diagnosis and treatment of lumbar spinal disorders. The reliability of CEB is 70%-80% in the literatures. The cause of failure of CEB may depend on anatomic basis. A total of 92 isolated sacra were used in this study. The bony landmarks were sacral hiatus and sacral cornua. Morphologic types of the sacral hiatus were classified using these landmarks. Also, location of the apex of sacral hiatus, diameter of the sacral canal at the apex of sacral hiatus, and the distance between bilateral cornua were measured. Two orthopedic surgeons performed measurements independently. Forty-two percent of the cases have both hiatus and cornu. Four percent of the cases showed the absent hiatus. The apex of sacral hiatus existed at the level of S4 vertebrae in 64% of the cases. The average diameter of the sacral canal was 6.0 +/- 1.9 mm. The average distance of bilateral sacral cornua was 10.2 +/- 0.35 mm. There were closed hiatus in 3% of cases. The sacral hiatus has anatomic variations. Understanding of these variations may improve the reliability of CEB.