The Study Of Related Factors And Mechanisms Of Adjacent Segment Degeneration After Lumbar Fusion

Part I Analysis of related factors of Adjacent segment degeneration after lumbar fusionObjective:To comprehensively analyze the main related factors of adjacent segmental degeneration after lumbar fusion.Methods:Three hundred and twenty four patients who underwent lumbar fusion from January 2013 to January 2019 were retrospectively reviewed.Patients were divided into two groups,the group of ASD were 54 patiens and the other group were 270 patients.Genders,age,operational methods,posterior ligament complex,fusional segments,preoperative adjacent intervertebral disc degeneration and postoperative adjacent segment intervertebral disc height,and lumbar lordosis angle(LL)were recorded and compared.Univariate analysis of ASD incidence and multivariate Logistic regression analysis of ASD incidence were performed.Results: Univariate analysis results showed that age,surgical methods,posterior ligament complex,number of fusion segments,preoperative adjacent segment disc degeneration,postoperative adjacent segment intervertebral disc height abnormalities,and postoperative lumbar lordosis abnormalities were closely related to the occurrence of ASD in patients with lumbar fusion(P<0.05).Multivariate Logistic regression analysis showed that more than 2 surgical segments,preoperative disc degeneration of adjacent segments and postoperative LL angle abnormality were independent risk factors for postoperative ASD(P<0.05).Conclusion : The number of fusion segments,age,surgical methods,posterior ligament complex,preoperative Adjacent segment degeneration and the height of the adjacent segment intervertebral disc,and lumbar lordosis angle anomaly were closely related to the adjacent segment degeneration after lumbar fusion.And multiple segmental fusion,preoperative adjacent segment disc degeneration and postoperative lumbar lordosis abnormalities were independent risk factors of ASD.Part Ⅱ Biomechanical study on the influence of different fixed segments of lumbar spine on the mobility of adjacent segmentsObjective:The present study was conducted to explore and analyze the influence of different fixed segments of lumbar spine on the mobility and stability of the adjacent segments.Methods : Fifteen goat spine specimens of appropriate length(T12-S1)were randomly divided into three groups: A(single-segment fixation group),B(double-segment fixation group),and C(triple-segment fixation group).Motion in different directions,including anterior flexion,posterior extension and lateral bending,were tested using a spinal motion simulation test system with the loading of five different external forces(45N,75 N,105N,135 N,and 165N)and measurement of the transverse displacement,forward-backward displacement and vertical displacement of the upper and lower adjacent segments was recorded.Results:As the external load increased,the displacements of the upper and lower adjacent segments increased.In comparison of group A with group C,when the pressure was less than or equal to 75 N,there was no statistically significant difference in the displacement of the upper and lower adjacent segments(P>0.05).Significant differences were found when the external force was greater than or equal to 105N(P<0.05).And the displacement of the upper adjacent segment was statistically different from the displacement of the lower adjacent segment(P<0.05).In comparison of group A with group B,there was no statistical difference in the displacement of adjacent segments(P>0.05).Conclusion : The displacement of adjacent segments increases with the increasing numbers of fixed lumbar segments,and the range of motion of adjacent segments of upper position was greater than the range of motion of adjacent segments of lower position.Increased mobility in adjacent segments leads to destabilization of adjacent segments and accelerates the degeneration of adjacent discs.Part Ⅲ The expression and significance of autophagy factors Beclin1 and P62 in the degeneration of intervertebral discs of the adjacent segments after lumbar fusionObjective : To study the expression of autophagy-related factors of Beclin1 and P62 in degenerated intervertebral discs of adjacent segments after lumbar fusion,and to find the mechanism and significance of autophagy of nucleus pulposus cells in adjacent segments after lumbar fusion.Methods : From October 2018 to January 2021,Forty eight lumbar intervertebral disc specimens of patients who were re-operated at the People’s Hospital of Guangxi Zhuang Autonomous Region due to adjacent segment lesions after lumbar fusion were collected.The Pfirrmann grades were III,IV,and V,being divided into three groups: A,B,and C,according to the level of degeneration,with 16 cases in group A,17 cases in group B,and 15 cases in group C;and 8 cases of lumbar burst fracture patients who underwent anterior operation of normal intervertebral disc specimens were collected,fifteen lumbar intervertebral disc specimens were collected in the control group(group D),the Pfirrmann grade of the discs were level I.PCR and Western Blotting were used to detect the m RNA expression and protein expression levels of Beclin1 and P62,and immunohistochemical method to analysis the positive expression rate of Beclin1 and P62 in the nucleus pulposus tissue of the observation group and the control group.Results: PCR and WB results showed that the normal intervertebral disc nucleus pulposus tissue and the adjacent segment degenerated intervertebral disc nucleus pulposus tissue both expressed autophagy-related factors of Beclin1 and P62 to varying degrees.The expression of Beclin1 in m RNA and protein levels in the groups A,B,and C was lower than that of group D(P<0.01),and decreased with the increasing degree of intervertebral disc degeneration,and the difference was statistically significant(P<0.01);while the expression of P62 in m RNA and protein levels in groups A,B,and C were higher than that in group D(P<0.01),and increased with the increasing degree of intervertebral disc degeneration(P<0.01);the results of immunohistochemistry showed that the positive rate of expression of Beclin1 in the tissues(groups A,B,C)was lower than that of the control group(group D)(P<0.01).The positive rate of expression of P62 was significantly higher in the degenerated nucleus pulposus tissues(groups A,B,C)in adjacent segments than that of the control group(group D),and the difference was statistically significant(P<0.01).Conclusion : Autophagy factors of Beclin1 and P62 are expressed in varying degrees in the degeneration of the intervertebral disc in the adjacent segment after lumbar fusion.As the degree of degeneration of the intervertebral disc increases,the expression of Beclin1 decreases,and the expression of P62 increases with the increasing degree of intervertebral disc degeneration.The autophagy effect of nucleus pulposus cells in the adjacent segment of the intervertebral disc degeneration grade III and above after lumbar fusion decreases with the increasing of the degree of intervertebral disc degeneration.