The forward slipping movement of the body of one of the lower lumbar vertebrae on the vertebra or sacrum below it is known as

The forward slipping movement of the body of the lower lumbar vertebrae on the vertebra or sacrum below it is known as spondylolisthesis. The vertebrae at the base of the spine is slipped in this process. Both or one of the vertebra's wing-shaped structures are fractured in spondylolisthesis. The person with spondylolisthesis may experience lower back pain, tightness in the hamstring muscles, pain and tenderness in the back along with excessive curvature of the spine.

Hence, the answer is 'spondylolisthesis'.

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.