Biomechanical changes at adjacent-level segments after anterior cervical discectomy and fusion

It is well documented that there is significant motion in the unfused segments above and below a fused segment during anterior cervical discectomy and fusion but exact nature of this motion is not well known. The current finite element study showed that likelihood of adjacent segment degeneration is higher in a two level fusion than a one level fusion. Also, the analyses showed that two level fusion at upper cervical levels more likely to degenerate above and below than two level fusion at lower cervical levels.