[Morphology and anteroposterior body equilibrium in spondylolisthesis L5-S1].

The authors have studied standard radiographs of 200 patients with lumbosacral spondylolisthesis, 52 of whom had been treated operatively. The radiographic technique is described. It allows measurement of pelvic retroversion and its influence on the appearance of slipping. The shape of the sacrum is not a consequence of the position of the pelvis but can alter during growth. Trunk imbalance may lead to increased stress with fracture of the pars interarticularis. Observation of these features makes it possible to follow the development of the deformity and to adopt appropriate treatment.