Congenitally Fused Cervical Spine Is Associated With Adjacent-Level Degeneration in the Absence of Cervical Spine Surgery.

Taken together, our data suggest that congenitally fused cervical spinal segments at C4-C5 and C5-C6 are associated with adjacent-level degeneration independent of fixation instrumentation. This study design removes surgical factors that might contribute to adjacent-level degeneration.