Background: Sacrum is an important bone of the human skeleton. It contributes in the formation of the pelvic girdle. It has many clinical applications. So this study was performed to demonstrate the different dimensions and measurements of the sacrum to make it easy for identifying sex and performing caudal epidural block.
Material and Methods: An anatomical study on 50 adult Egyptian dry complete undamaged sacra was performed in the Human Anatomy and Embryology department, Faculty of Medicine, Zagazig University, Egypt. The parameters used in this study were the different dimensions of the sacrum including the morphology of the sacral hiatus, the extensions of the auricular surface, the sacral index and the auricular index. All the measurements were performed by using a Vernier digital caliper with accuracy of 0.1mm. The measurements were recorded and their mean and standard deviations were calculated.
Results: It was found that the mean values of sacrum width and height, transverse diameter of the wing and the base of sacrum were more in males than females. While auricular surface length, sacral and auricular indices were higher in females than in males. Also the mean values of width and height of the sacral hiatus were more in males than females.

Conclusions: The sacral index and the maximal sacral length and width were the most significant of all the parameters used for sex identification. Also, the determination of the anatomical variations of the sacral hiatus may be helpful in increasing the success rate of caudal epidural anaesthesia.