Using computed tomography, we studied twenty-nine patients who had
thirty-one fractures of the posterior margin of a vertebra in the lumbar
spine. Based on our findings, these fractures were classified
morphologically into three types: a simple separation of the entire margin;
an avulsion fracture of some of the substance of the vertebral body,
including the margin; and a more localized fracture. In this series,
twenty-two of the thirty-one fractures were associated with a defect
involving the affected end-plate. This fact suggests that the pathogenesis
of these fractures may be the fragility of the end-plate.