Anatomical Study of Sacrum and its Clinical Significance.

ABSTRACT

Background: Sacrum is formed by the fusion of five sacral vertebrae and forms the lower part of Vertebral column. The opening present at the lower end of sacral canal is known as sacral hiatus. Methods: This study was carried out on 75 dry human sacra of unknown sex to study the variations of sacral hiatus. Various shapes of sacral hiatus were observed which included inverted u, inverted v, irregular, dumbbell and bifid. The apex of sacral hiatus was commonly found at the level of 4th sacral vertebra. The mean length of sacral hiatus, the mean anteroposterior diameter of sacral canal was measured. The narrowing of sacral canal at the apex of sacral hiatus was measured. Results: We observed length of Sacral hiatus from apex to midpoint of base – maximum length was found to be 11 – 20 mm in 32 dry sacra. Anteroposterior diameter at the sacral hiatus was found to be 0 – 3 mm. in 35 dry sacra. Base (Transverse diameter) was found to be 11 – 15 mm in 36 dry sacra. Median distance between the level of lower margin of S2 and apex of sacral hiatus was 21 – 30 mm in 25(33%) Sacra. Distance between midpoint of Base to S2 foramen was found to be >40 mm in 52 Sacra and that accounts for 69 %. Conclusion: The knowledge of anatomical variations of sacral hiatus is clinically important for caudal epidural block in Pediatric, Obstetric, Orthopedic, Urologic and Surgical practice. The reliability and success of caudal epidural block depends upon Knowledge of Variations of Sacral hiatus.