Study of adjacent segment degeneration after internal fixation lumbar fusion with pedicle screw

Abstract

Objective To observe the changes of the height of intervertebral discs of the segments adjacent to the fusional and instrumental area after the operation and the relation between the changes of height of intervetebral discs in the adjacent segments and the angle of the pedicle screw.Methods Thirty-one patients who underwent internal fixation from September 2004 to March 2006 were retrospectively analyzed.The intervertebral discs height of adjacent segment was studied.The influence ofSuspensory fixationon the changes of height of adjacent intervertebral discs was compared.The relation between the changes of the height of the upper adjacent intervertebral discs and the angle of pedicle screw was analyzed.Results The mean follow-up period for the patients was 13.5 months(10-16 months).In the operating-group,the height of the adjacent intervertebral disc decreased slightly,but the changes had no statistical significance(P＞0.05).Between the group fixed between L5 and S1 and group fixed between L4and L5,the changes of the height of the upper adjacent intervertebral discs had no obvious difference(P＞0.05).In the group fixed between L4 and L5,there had no obvious difference between the changes of the height of the upper adjacent intervertebral discs and the changes of the height of the lower one(P＞0.05).When the operating-group were divided into two groups according to the angle of pedicle screw (＜6°or＞6°),the changes of the height of the upper adjacent intervertebral discs had no obvious difference(P＞0.05).But there had positive and correlative relation between changes of the height of the adjacent intervertebral discs and the angle of pedicle screw(r=0.373,P=0.039).Conclusion Suspensory fixationhas no different influence on the changes of height of adjacent intervertebral discs.There has no difference on the risk of degeneration between upper and lower segment adjacent to the fusional area.There has positive and correlative relation between the changes of height of the upper intervertebral discs adjacent to the fusional area and the angle of pedicle screw,that is,the bigger the angle is,the more clearly the height of adjacent intervertebral discs will change. Key words: Lumbar vertebrae; Internal fixation; Fusion; Intervertebral disc; Degeneration