The etiology of spondylolisthesis is multiple according to the type of the vertebral slipping. In fact all the following basic pathological processes may be involved: congenital malformation of the upper sacrum in the dysplastic spondylolisthesis; growth dysplasia of the vertebral arch in the "isthmic spondylolisthesis" where an hereditary background and mechanical stresses play a determining role; degenerative conditions of the intervertebral joints in "degenerative spondylolisthesis" of Newman or the "pseudospondylolisthesis" of Junghanns; infections and benign or malignant tumors destroying the articular bolt maintaining the vertebral line; traumatic lesions such as multiple fractures of the bony hook or much more rarely an isolated bilateral fracture of the pars interarticularis.