Wikipedia
Retrolisthesis
A retrolisthesis is a posterior displacement of one vertebral body with respect to the adjacent vertebrae to a degree less than a luxation (dislocation). Clinically speaking, retrolisthesis is the opposite of spondylolisthesis ( anterior displacement of one vertebral body on the subjacent vertebral body), and is also called retrospondylolisthesis. Retrolistheses are most easily diagnosed on lateral x-ray views of the spine. Views, where care has been taken to expose for a true lateral view without any rotation, offer the best diagnostic quality.
Retrolistheses are found most prominently in the cervical spine and lumbar region but can also be seen in the thoracic area.