Sacral vertebrae: There are 5 sacral vertebral bones. They are represented by the symbols S1 through S5 and are situated between the lumbar vertebrae and the coccyx (the lowest segment of the vertebral column).The sacral vertebrae are normally fused to form the sacrum.hey are represented by the symbols S1 through S5 and are situated between the lumbar vertebrae and the coccyx (the lowest segment of the vertebral column).