Introduction: Understanding the Anatomical variations of Sacral hiatus using bony land marks impoves the reliability of caudal epidural block. Caudal block is indicated whenever the area of surgery involves lower lumbar and sacral nerve roots.. Hence the present study was made in an attempt to define different parameters to locate the sacral hiatus precisely.

Material and Methods: The study was carried out by using 60 complete & undamaged dry sacrum which were obtained from the department of Anatomy, Mahatma Gandhi Medical College & Research Institute, Puducherry. Various parameters of sacral hiatus were measured using a Vernier caliper with 0.1mm accuracy. The various shapes of sacral hiatus was also observed.`         `

Results: Majority of the bones had a U shaped sacral hiatus (63%), followed by V shaped (30.5%), irregular shape (5.5%) and 1% sacral hiatus agenesis. Position of the apex was most commonly seen at the level of S4 vertebra and the base of sacral hiatus was most seen at the level of S5 vertebra. The other parameters were recorded and tabulated.