Research Of The Relationship Between The Fusion Angle Of PLIF And Adjacent Segment Degeneration Of Lumbar Degenerative Disease

With the increasing clinical application of Lumbar interbody fusion,adjacent segment degeneration（Adjacent Segment Degeneration,ASD）has become a major problem after fusion.Up to now,the relationship between adjacent segment degeneration and Lumbar interbody fusion has been discussed in several literatures,but the mechanism of ASD is still unclear,and there is no clear knowledge or data on its risk factors,which may be related to the biomechanical changes of adjacent segments after lumbar fusion.The fusion Angle of the lumbar spine after posterior lumbar interbody Fusion（Posterior lumbar Interbody Fusion PLIF）surgery can affect the postoperative intervertebral disc pressure and intervertebral motion in the adjacent segment,and these biomechanical changes may accelerate the occurrence of adjacent vertebral degeneration.Therefore,the appropriate Angle of fusion can help to reduce the incidence of adjacent segment degeneration.Objective:To explore the relationship between the changes of Cobb Angle and adjacent segment degeneration after PLIF surgery.Method:Retrospective analysis of 68 patients who were explicitly diagnosed with lumbar degenerative disease and underwent lumbar posterior decompression,internal fixation and fusion（PLIF）in our hospital from January 2015 to December 2016,the lesion segment is L_4-5,the fusion angle of postoperative lesion segments is greater than 5°or not is divided into group A（≥5°）and group B（<5°）（n=34）,the fusion Angle of group A was（7.66±2.06）°,and that of group B was（3.59±0.99）°,The operative time,intraoperative blood loss,postoperative drainage volume,preoperative and postoperative JOA score,preoperative and postoperative VAS score,preoperative and postoperative dynamic range of L_3-4,postoperative Lumbar Lordosis,postoperative sagittal vertical axis and other indicators were recorded in detail.the degeneration of adjacent vertebrae was compared between the two groups.Result:There was no significant difference in gender,age and body mass index between the two treatment groups（P>0.05）.Group A:operative time（126.06±17.38）min,intraoperative blood loss（254.38±94.72）ml,postoperative drainage volume（258.62±117.67）ml,preoperative JOA score（15.35±2.23）ml,postoperative JOA score（26.65±1.65）ml,preoperative VAS score（5.21±1.25）,postoperative VAS score（2.71±1.57）,preoperative dynamic range of L_3-4（5.94±1.64）,postoperative dynamic range of L_3-4（7.79±2.30）,postoperative Cobb Lumbar Lordosis（36.62±3.22）°,postoperative sagittal vertical axis（2.23±0.98）cm;Group B:operative time（130.82±18.22）min,intraoperative blood loss（264.65±84.59）ml,postoperative drainage volume（260.88±85.89）ml,preoperative JOA score（14.79±2.29）ml,postoperative JOA score（26.94±1.18）,preoperative VAS score（5.18±1.27）,postoperative VAS score（2.94±1.50）,preoperative dynamic range of L_3-4（5.55±1.90）,postoperative dynamic range of L_3-4（9.11±2.65）,postoperative Lumbar Lordosis（34.84±2.80）°,postoperative sagittal vertical axis（2.71±1.07）cm.There were no significant differences between the two groups in the operative time,intraoperative blood loss,postoperative drainage volume,preoperative JOA score,postoperative JOA score,preoperative VAS score,postoperative VAS score,preoperative dynamic range of L_3-4,postoperative sagittal vertical axis（P>0.05）,while there were significant differences in the Lumbar Lordosis,postoperative dynamic range of L_3-4,between the two groups.The postoperative JOA score,postoperative VAS score and postoperative dynamic range of L_3-4 were compared with postoperative JOA score,postoperative VAS score and postoperative dynamic range of L_3-4 in the two groups.and the difference was statistically significant（P<0.05）.The fusion Angle was negatively correlated with the sagittal vertical axis,and the correlation coefficient was-0.515（P<0.05）,and positively correlated with the postoperative total lumbar Cobb Angle,and the correlation coefficient was0.543（P<0.05）.Three cases of ASD occurred in group A after PLIF surgery,the incidence was 8.82%,the incidence in group B was 10 cases,the incidence was 29.41%.Compared between the two groups,the rate of vertebral degeneration in group B was significantly higher than that in group A,the difference was statistically significant（P<0.05）.Conclusion:For patients with lumbar spinal canal decompression and internal fixation,the fusion angle of the diseased segment is too small to make the adjacent segments more prone to degeneration,and it is easy to cause imbalance of the sagittal plane of the spine and accelerate the occurrence of adjacent degeneration.The clinical efficacy of the patient is reduced,and the fusion angle should be prevented from being too small during the operation,thereby reducing the incidence of degeneration of the collar and improving the prognosis of the patient.