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Fusion's Effect on Nearby Discs

Spinal fusion is becoming more common all the time. But there's one thing still puzzling doctors. If two vertebral bones are fused together, and the next disc down looks bad, should that adjacent segment be fused too? If it isn't fused, will it cause problems? This was the focus of doctors at the Vanderbilt University Spine Center in Tennessee. They suspected the worst. However, they were pleasantly surprised by the results of their study.

Two groups of patients totaling 25 people had lumbar fusion for degenerative instability. This means the discs were damaged, thin, and dried out, leaving the spine at that level loose and unstable. MRI scans were used to see the discs on either side of the fusion site. Patients were divided into normal (NL) or degenerative disc disease (DDD) based on MRI findings. The researchers thought the DDD group would have a worse result than the NL group. As it turns out, there was no difference between the two groups. In fact, the DDD group actually did slightly better.

Measures used in this study included pain, general health, social functioning, and mental health. The patients were followed for two years. The authors think problems at the degenerated level may occur later. Increased load from the fusion site may transfer to the level above or below. So they plan to follow this group for a longer period of time. They also suggest that a larger study be conducted.

References: Thomas W. Throckmorton, MD, et al. The Impact of Adjacent Level Disc Degeneration on Health Status Outcomes Following Lumbar Fusion. In Spine. November 15, 2003. Vol. 28. No. 22. Pp. 2546-2550.

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