Definition:
'Spondylolisthesis' is the anterior or posterior displacement of a vertebra or the vertebrae column in relation to the vertebrae below. It was first described in 1782 by Belgium obstetrician, Dr. Herbinaux. These "slips" (aka "step-offs") occur most commonly in the lumbar spine. A ''hangman's fracture'' is a specific type of spondylolisthesis where the cervical vertebra is displaced anteriorly relative to the C3 vertebra due to fracture (bone)s of the C2 vertebra's pedicle of vertebral arch.