Segmental Stiffness Achieved by Three Types of Instrumented Fixation for Unstable Lumbar Spondylolytic Motion Segments

Spondylolysis is a defect in the vertebral pars interarticularis. Its cause may be developmental or due to mechanical etiologies such as trauma. Most childhood and adolescent spondylolisthesis (defined as a slip of one vertebrae relative to another) is associated with spondylolysis of the pars interarticularis at the L5–S1 motion segment.