Anatomy and clinical significance of sacral variations: a systematic review

The sacrum is a large trilateral bone located at the base of the vertebral column serving to transfer the body weight from the trunk to the pelvis and lower extremities. Over the years, an abundance of sacral anatomical divergences has been reported, including numerical and/or morphological variations of sacral entities. The majority of these anatomical alternations has been incidentally identified during radiological investigations, surgical procedures or discovered in anatomical, anthropological and forensic research studies. Throughout international literature, however, there is a scarcity of an integrative recording of all known anatomical variations of the sacrum in a single study. This constitutes the objective of the present paper: to provide an exhaustive systematic review of the relevant literature, as well as to thoroughly describe all the recognized deviations of the sacrum structure, while highlighting the aspects of their clinical significance.