The human sacrum is a triangular bone formed by the fusion of five separate vertebras along with the intervertebral discs. Gross morphology of sacrum shows a concave ventral surface, a convex dorsal surface and a triangular sacral canal. The sacral canal consists of an anterior wall formed by the fusion of the posterior aspects of sacral vertebral bodies and the dorsal wall is formed by the fused laminae, spines and ossified ligaments flava. During the routine course of osteology for undergraduates one of the sacrum showed complete absence of the dorsal wall of the sacral canal. Anatomical variations frequently occur around the dorsal wall of the sacral canal especially in relation to sacral hiatus. The variations may be attributed to the dependency of the sacrum to the load related fusion of the bone structure. Knowledge of such variations is of profound importance in spinal injuries, neurosurgeries and caudal epidural anaesthesia.
Keywords: Sacrum, Sacral canal, Agenesis, Caudal epidural anaesthesia