Spondylolisthesis
Spondylolisthesis is a spinal condition in which the vertebrae may slip forward or backward. A forward slip of the vertebrae is called anterolisthesis. A backward slip of the vertebrae is called retrolisthesis. This altered positioning (slippage) of the vertebrae may cause compression of the nerves down the central spinal canal as well as the nerve openings on each side of the vertebrae.