Morphometric Study of Sacral Hiatus in Central Part of Rajasthan & its Correlation with Caudal Epidural Block

Introduction:Sacrum is a triangular bone forming the caudal end of the vertebral column, formed by fusion of five vertebras.Sacral hiatus is the opening present at the caudal end of sacral canal formed by the nonfusion of the lamina of the fifth (occasionally fourth) sacral vertebra.The structures passing through sacral hiatus are a pair of 5th sacral nerves, a pair of coccygeal nerves, filumterminaleexterna. Caudal.epidural block (CEB) is widely used to provide anesthesiafor various clinical procedures. Knowledgeof sacral hiatus anatomy play major role in the success of needle placement for desired results of caudal epidural block. Aim: Morphometric study of sacralhiatus, for caudalepidural block point of view. This knowledge will help foroptimal access into sacral epidural space and to prevent the hazard of Dural sac puncturein population of central partof Rajasthan. Materials and Methods: This study was carried out on 75 dry human sacra to know the variations in morphology of the sacral hiatus. Results: Various shapes of sacral hiatus were observed which included inverted V 32 (42 %), inverted U 23(30.66%), and irregular 10 (13.66%) M shaped 8(10.66%) anddumbbell shape 8(10.66%), Spina bifida 1(1.33%) and complete agenesis of dorsal wall of sacrum was in 1(1.33%). The apex of sacral hiatus was commonly found at the level of 4th sacral vertebra in 54.66% at S3 sacral vertebra in 29(38.66%) and S5 in 4(5.33%) and at S1 levelin only one (1.33%) of the sacral vertebra studied. Base of the hiatus was commonly found at the level of S5 in50 (63.66%) at S4 in 15(20%), C1 level in 9(12%) and at C2 in one (1.33) of sacral vertebra. Length of sacral hiatus ranged between 8.0 mm to 60 mm, breadth at base was 10-25 mm and AP diameter at apex was 3–10 mm. Conclusion:The knowledge of anatomy of sacral hiatus plays importantroleinneedle placement in Extra DuralBlock for various treatment of lumbar spinal disorders and for the management of chronic back pain. Absent sacral hiatus leads to poor outcome of the caudal epidural anesthesia and dorsal agenesis of the sacrum would lead to only partial anesthesia. The formation of equilateral triangle by joining super-lateral sacral crests at S2 and apex of sacral hiatus forms a practical guide in locating sacral hiatus for caudal epidural anesthesia.