The spine normally consists of 33 vertebrae. The coccyx can consist of 5 or 6 vertebrae instead of the common 3 or 4 vertebrae. In addition, cervical ribs and lumbar ribs may be identified. The borders between the spinal column regions may shift cranially whereby L5 is absorbed in the sacral bone (sacralisation or pelvis-assimilation). The borders between the spinal column regions can also shift caudally and S1 may be separated from the sacral bone (lumbalisation). The atlas may fuse with the occipital bone (atlas-assimilation).
