Long-Term X-ray Findings After Spinal Fusion
Many studies have shown increased degenerative changes in the spine after spinal fusion. Most of the research has focused on changes in the next vertebral segment up from the fused segment. This site is called the adjacent segment. The changes are referred to as adjacent segment degeneration (ASD).
In this study, researchers in Spain look at the effects of spinal fusion at other levels. They ask the questions: are there changes in other levels? Are the changes caused by the fusion? Or is there a general pattern of degeneration going on?
They analyzed unfused lumbar segments from 62 patients. Everyone had a posterior, instrumented lumbar spinal fusion. Posterior means the surgery was done from the back of the spine. Instrumented refers to a metal plate and screws used to hold the spine in place until the fusion was solid.
Computer analysis of X-rays taken before and after surgery was the primary measure used in this study. The authors found no difference in disc height before and after surgery. This was true for the first, second, and third segments above the lumbar fusion. Disc collapse or narrowing of the disc space was the same at all levels above the fusion.
The authors conclude that disc narrowing and loss of disc height are not caused by the fusion. These changes were not linked with the length of fusion, fusion level, or the distance away from the fusion. These do not appear to be factors in ASD. The high rate of ASD after spinal fusion is probably the result of normal aging processes.
Ferran Pellisé, MD, PhD, et al. Radiologic Assessment of All Unfused Lumbar Segments 7.5 Years After Instrumented Posterior Spinal Fusion. In Spine. March 1, 2007. Vol. 32. No. 5. Pp. 574-579.