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Two-Level Skip Fusion Superior to Three-Level Fusion

Skipping unaffected cervical level reduces stress on spine while preserving motion segment

THURSDAY, March 24 (HealthDay News) -- Fusion of the cervical spine across three levels for treatment of nonadjacent disease shows a marked increase in strain compared to a two-level fusion, which skips the unaffected level, according to a study published online March 15 in Spine.

Michael A. Finn, M.D., of the University of Utah School of Medicine in Salt Lake City, and colleagues examined the biomechanical forces that are exerted on intermediate and adjacent spinal segments after a two- and three-level fusion for treatment of noncontiguous levels. Range of motion and strain were tested in seven human cadaveric cervical segments in two settings. In the first, C4-C5 and C6-C7 diskectomies were performed, and fused with rigid cervical plates and interbody spacers. In the second setting, a three-level fusion from C4 to C7 was performed.

The researchers found that increased biomechanical stress on a skip segment is not additive and is less than that of contiguous segments of a three-level fusion. In the three-level fusion construct, there was a significant or nearly significant increase in motion in all moments at the infra- and supra-adjacent levels compared to the intact and the two-level noncontiguous fusion (72 percent increase). In the skip fusion construct, the range of motion was modestly increased (35 percent) in the intermediate and adjacent levels.

"In comparison to a three-level fusion, a two-level noncontiguous fusion preserves an additional motion segment and all preserved motion segments see less stress. It is, therefore, reasonable to consider performing a noncontiguous fusion when confronted with nonadjacent disease," the authors write.

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