Morphological and morphometric features of sacral hiatus and its clinical significance in caudal epidural anaesthesia.

Abstract

Caudal epidural block (CEB) failure or complications are not unheard even among experienced anaesthesiologists and are usually due to sacral hiatus (SH) anatomy variations. The aim of the present study is to observe, record and analyse important anatomical features of SH and correlate them with potential CEB limitations. The SH of 155 complete and undamaged Greek adult dry sacra of known sex were included in the study. Three non-metric (shape of SH and location of hiatal apex and base in relation to level of sacral/coccygeal vertebra) and five metric parameters (height of the SH, transverse width of the SH at the base, anteroposterior diameter of the SH at the level of its apex and the distance from the sacral apex and base to the upper border of S2 foramina) were evaluated. Inverted U (34.83%) and inverted V (26.45%) were the commonest shapes. Hiatal apex and base were most commonly related to the level of S4 (78.70%) and S5 vertebra (89.03%), respectively. Mean height, depth and intercornual distance were 19.05 ± 8.65 mm, 5.39 ± 1.84 mm and 12.41 ± 3.16 mm, respectively, whereas mean distance between the upper border of S2 foramen and the apex and base of the SH were 46.34 mm and 63.48 mm, respectively. Anatomical variations of SH that might be responsible for CEB failure, such as elongated SH, absence of SH, complete dorsal wall agenesis of sacral canal and narrowing (< 3 mm) at the apex of SH were found in 17.43% of sacra (male 10.94% and female 25.22%). This study suggests a potential risk of failure of CEB in Greek patients, especially in females, which should be kept in mind while giving caudal epidural anaesthesia.