Relationship Between T1 Slope And Sagittal Alignment Parameters Of The Upper Or Subaxial Cervical Spine In Patients With Cervical Lordotic And Kyphotic Curvature

Objectives:The objective of the present study was to identify associations between T1 slope and sagittal alignment parameters of the upper or subaxial cervical spine in patients with lordotic and kyphotic curvature.Methods:610 patients(309 men and 301 women)with no-specific neck pain without neurogenic symptoms were included,with an average age of 42.18 years(range,18-76 years).The sagittal radiographic parameters,including Chin brow vertical angle(CBVA),McGregor’s slope,slope of light of sight(SLS),C0-C1 Cobb,C1-2 Cobb,C2-C7 Cobb,C2-C7 SVA,and T1 slope minus cervical lordosis(TS-CL)were evaluated.According to C2-C7 Cobb,the patients were divided into two groups: lordotic and kyphotic groups.The correlations among radiographic variables were collected and analyzed with the Pearson correlation coefficient and Linear regression analysis.The One-way analysis of variance(ANOVO)was used to compare the difference of different cervical alignment types(lordosis and kyphosis).Results:610 patients were included in this study.507 patients(83.1%: 256 men,251 women)maintained horizontal gaze with lodortic cervical alignment,with a mean age 43.38±13.88 years(18-76 years);while the remained 103 patients(16.9%;49 men,54 women)with kypotic cervical alignment,with a mean age 36.23 years(18-68 years).Intra-observer agreement with kappa values ranging from 0.91 to 0.93 was “excellent”among the 2 observes.Inter-observer agreement with kappa values ranging from 0.79 to 0.80 was “substantial”.Significant differences were observed in C0-C1 angle(P<0.01),C1-C2 angle(P<0.01),C0-C2 angle(P<0.01),C2-C7 SVA(P<0.01)and TS-CL(P<0.01)between two groups,but there were no differences in T1S(P=0.367).Among two groups,C2-C7 SVA has significant linear correlation with T1S(r2=0.712 vs r2=0.467)and TSCL(r2=0.810 vs r2=0.248).Conclusions:This study showed that two cervical alignment types(lordosis and kyphosis)have different compensatory mechanisms.And subaxial cervical lordosis plays an important compensatory role in maintaining total cervical balance and horizontal gaze.Additionally,TS-CL mismatch may significantly impact lordotic cervical alignment in lordotic group.