Definition: Spondylolisthesis is a condition that occurs when there are bilateral defects of the pars interarticularis of the spine, most commonly the lumbar spine. In this situation, the vertebral bodies are not properly held in place, and prone to "slip" forward over the vertebral body below itself.
Treatment of spondylolisthesis depends on two factors: how significant the slip is, and how quickly it is progressing. Mild cases of this condition can be managed conservatively, similar to spondylolysis; however, more significant cases will need operative stabilization. Most often the affected segments are fused in place. In the most serious cases, the vertebral body is returned to its normal anatomic position ('reduced') and subsequently fused.
