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Finding Causes of Spine Slippage in Kids

Two concerning spine problems affect children and teens. Spondylolysis is a crack or tiny fracture in the bony ring that protects the spinal nerves. Spondylolisthesis occurs when the vertebra slips forward on the one below it. What causes this slippage?

Until the bones are fully developed in children, there's a separation at the end of the bone where bone meets cartilage. This is called the growth plate. Until that cartilage hardens and becomes bone at the end of growth, the growth plate is visible on X-ray. Scientists wondered if slippage occurs if the bone and cartilage separate.

Japanese researchers used rat models to test this idea out. They were looking for the cause of slippage in spondylolisthesis. Part of each rat spine was cut away to make it unstable. X-rays were taken and the cells studied under a microscope to find out what happens after surgery.

Researchers found no slippage before day five. Most cases of forward slippage occurred around day seven. There was no sign of disc degeneration. The results showed that growth plate separation was the reason for slippage in the immature spine. The extra stress of the spondylolisthesis breaks the growth plate. The cartilage separates from the bone and the bone slips forward.

The authors say this makes sense because slippage doesn't occur when the growth plate disappears at maturity. Future studies are needed to find out what biologic events occur leading up to point that the growth plate gets weak and comes apart.

References: Koichi Sairyo, MD, PhD, et al. Vertebral Forward Slippage in Immature Lumbar Spine Occurs Following Epiphyseal Separation, and Its Occurrence Is Unrelated to Disc Degeneration. In Spine. March 1, 2004. Vol. 29. No. 5. Pp. 524-527.

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