ABSTRACT
Since the 1980s, spinal fusion using a pedicle screw system has widely been implemented all over the world, yet many cases with postoperative adjacent segment degeneration have been reported (1-3). An accelerated degenerative change caused by increased motion or load on the motion segments adjacent to the fixed vertebrae is considered to lead to such adjacent segment degeneration (4,5). Changes in adjacent motion segments, such as degeneration of the intervertebral disc and facet joint and segmental instability, occur at the early stage, and failures including spinal canal stenosis, spondylosis, spondylolisthesis, and fracture of the vertebral body are observed at the progressive stage (6).
