ABSTRACT
Spondylolisthesis describes the condition when a vertebra shifts forward on the underlying vertebra. The shifting of vertebrae can be produced by specific and quite rare situations, such as tumours of the posterior arch or traumatic injuries as listed in the aetiological classification of Wiltse1
(Table 91.1). However it usually happens under two principal
pathologies:
● by degenerative erosion of the articular surface leading to degenerative spondylolisthesis;
● by a fatigue fracture of the posterior arch occurring in the pars interarticularis. The pars fracture without displacement is named spondylolysis, and if the vertebra shifts, spondylolisthesis by isthmic lysis.
