Correlation Between The Changes Of Cervical Sagittal Balance Parameters And Adjacent Segment Degeneration After Anterior Cervical Spine Surgery

Objective:To measure the cervical sagittal balance parameters in patients with adjacent segment degeneration（ASD）after anterior cervical discectomy and fusion,analyze its correlation with ASD,and explore the related risk factors affecting disease progression.Methods:The imaging and clinical data of 65 patients who underwent anterior cervical single-level discectomy and fusion（ACDF）at Department of Spinal Surgery,the Third Affiliated Hospital of Shanxi Medical University from January 2017 to December 2022were retrospectively analyzed.Among them,26 patients had adjacent segment degeneration as the degeneration group,accounting for 40.00%;There were 39 patients without adjacent segment degeneration（60.00%）in the non-degeneration group.The general data such as sex,age,BMI,and surgical segment were compared between the two groups.Four sagittal balance parameters including C_2-7sagittal vertical axis(C_2-7SVA),C_2-7Cobb Angle,surgical segment Cobb Angle,and T₁Slope（T₁S）were measured before operation and at the last follow-up.Three scores including The Japanese orthopaedic association（JOA）score,visual analogue score（VAS）and neck disability index（NDI）were recorded before operation,3 months after operation and at the last follow-up.Results:A total of 65 patients were included in this study,including 26 patients in the degeneration group and 39 patients in the non-degeneration group.The ratio of surgical fusion segments between the two groups was statistically significant（P<0.05）.In the degeneration group,38.46%（10/26）patients had T₁S<19.5°and 17.95%（7/39）in non-degeneration group,the difference between the two groups was statistically significant（P<0.05）,the relative risk was 1.953.The C_2-7Cobb Angle increased from（10.12±7.65）°preoperatively to（14.58±7.12）°at the last follow-up;The Cobb Angle of operated segment increased from（6.14±5.12）°to（9.55±5.93）°;The C_2-7SVA increased from（18.92±8.18）°to（24.43±10.27）°;The T₁S increased from（20.55±6.18）°to（25.97±9.56）°,the differences were statistically significant（P<0.05）;At the last follow-up,the C2-7 Cobb Angle（14.58±7.12）°and the Cobb Angle of operated segment（9.55±5.93）°in the degeneration group were smaller than those in the non-degeneration group,and the difference was statistically significant（P<0.05）.At the last follow-up,the JOA score of the degenerative group changed from（14.59±2.57）at three months after operation to（7.31±3.19）.The VAS score changed from（0.11±0.23）at three months after operation to（3.13±2.02）.The NDI score changed from（25.17±9.89）%at three months to（50.05±10.22）%,and the difference was statistically significant（P<0.001）.There was a positive correlation between C_2-7Cobb Angle and T₁S in the degeneration group at the last follow-up（r=0.568,P<0.05）;C_2-7Cobb Angle was negatively correlated with the change of NDI index（r=-0.259,P<0.05）;C2-7 Cobb Angle was positively correlated with the change of JOA score（r=0.236,P<0.05）.Conclusion:Cervical sagittal balance parameters have extremely important clinical application value in the prevention and treatment of adjacent segment degenerative disease after anterior cervical surgery.The C_2-7Cobb Angle should be fully restored during anterior cervical spine surgery.ASD is more likely to occur in patients undergoing C5/6segmental ACDF surgery and patients with T₁S<19.5°.There was a positive correlation between C_2-7Cobb Angle and T₁S,C_2-7Cobb Angle were correlated with clinical efficacy score.