An osteological study on morphometry, anatomical variations and applied importance of sacral hiatus and sacral canal in the state of West Bengal

Introduction: Sacral hiatus is the opening present at the posterior aspect of lower end of sacral canal. It is formed due to non-fusion of laminae of fifth sacral vertebrae. Caudal epidural anaesthesia is accessed through sacral hiatus but anatomical variations of sacral hiatus can result in problems. Present study was done to find out the anatomical variations of sacral hiatus which could help anaesthesiologists in the clinical field. Aim and Objectives: To study different morphological and morphometric variations of sacral hiatus. Materials and Methods: A cross sectional, observational, osteological study was performed on 100 (final sample size 87) dry, adult, human sacra of West Bengal state. Various parameters were studied like shape of sacral hiatus, level of apex of sacral hiatus, level of base of sacral hiatus, length of sacral hiatus, anteroposterior depth of sacral hiatus, transverse width of sacral hiatus. All measurements were taken using Vernier calipers of 0.2 mm accuracy. Results: In the present study most common shape of sacral hiatus was inverted U shape (51.7%). Most frequently occurring level of apex of sacral hiatus was opposite S4 body (46%) and base of sacral hiatus was typically located opposite S5 body (92%). Length of sacral hiatus had a mean of 2.36 cm and standard deviation of 0.93 cm. Mean of anteroposterior diameter of sacral hiatus was 0.65 cm with a standard deviation of 0.22 cm. Transverse diameter of sacral hiatus had a mean of 1.49 cm and standard deviation of 0.30 cm. Conclusion: Inverted U shape of sacral hiatus which is most common in our study makes caudal epidural anaesthesia easier. Knowledge of anatomical variations of sacral hiatus improves success rate of caudal epidural anaesthesia and helps in avoiding complications.