Morphometric Study of Sacral Hiatus in Dry Adult Human Sacra: Its Clinical Relevance in Caudal Epidural Block

Abstract

INTRODUCTION: Correct localization of the sacral hiatus is essential for administering a successful caudal epidural block. The present study was undertaken to find out the anatomical variations of sacral hiatus by metrical method, so that it could help anaesthesiologists in the clinical field. MATERIALS AND METHODS Study was performed on 140 (83 male and 57 female) adult human sacra of known sex. Various parameters of sacrum studied were as follows; the shape of hiatus, length of sacral hiatus, transverse width at the base and anteroposterior diameter at the level of apex. For each parameter, the mean value (calculated in mm), standard deviation, range and percentage of bones identified correctly were calculated. RESULTS Various shapes of sacral hiatuses were observed, including inverted ‘U’ in 73 (52.14%), inverted ‘V’ in 33 (23.57%), irregular in 10 (7.14%), elongated in 10 (7.14%) and dumbbell shaped in 12 (8.57%). Absent sacral hiatus was observed in 2 (1.43%) specimens. The mean value for length of sacral hiatus from apex to midpoint of base was found to be 23.26 mm in males and 22.38 mm in females. However, the parameter was found to be statistically not significant. The mean value for transverse width at base of hiatus was found to be 14.19 mm in males and 13.54 mm in females. The mean value for anteroposterior diameter of sacral canal at apex was found to be 4.57 mm in males and 4.32 mm in females. Both the above parameters were found to be statistically not significant. SUMMARY AND CONCLUSION: The anatomical knowledge of sacral hiatus and its variations are important in caudal epidural anaesthesia, and it may improve the success rate of caudal epidural anaesthesia.