The Sacrum
They begin to fuse in late adolescence and early adulthood and are usually fully fused by age 30. The sacrum acts as the base of the spinal column, as well as the back “wall” of the pelvis.
Why does the sacrum fuse?
The fusion of the vertebrae and the large size of the sacrum forms an ideal base that allows it to support the weight of the entire body.
At what age does the sacral bones fuse?
Individually, the sacrum and coccyx are composed of smaller bones that fuse (grow into a solid bone mass) together by age 30. The sacrum is made up of 5 fused vertebrae (S1-S5) and 3 to 5 small bones fuse creating the coccyx.
