Spondylolisthesis

Spondylolisthesis is the anterior or posterior displacement of a vertebra or the vertebral column in relation to the vertebrae below. It was first described in 1782 by Belgian obstetrician, Dr. Herbinaux. He reported a bony prominence anterior to the sacrum that obstructed the vagina of a small number of patients. The term “spondylolisthesis” was coined in 1854 from the Greek σπονδυλος = "vertebra" and "ὁλισθος" = "slipperiness," "a slip." The variant "listhesis," resulting from misdivision of this compound word, is sometimes applied in conjunction with scoliosis. These "slips" (aka "step-offs") occur most commonly in the lumbar spine.

A hangman's fracture is a specific type of spondylolisthesis where the C2 vertebra is displaced anteriorly relative to the C3 vertebra due to fractures of the C2 vertebra's pedicles.