The Correlation Study Between Change Of Sagittal Alignment Types And Disc Degeneration In Cervical Spine

Objectives:This study sought to determine whether the sagittal alignment subtype is related to the prevalence of cervical disc degeneration.Backrounds:Cervical spine is a very complex area,not only bears the weight of the head,but also maintains and adjusts the horizontal gaze,due to the complexity of anatomical structure and function of the cervical spine,make it vulnerable to a variety of structural abnormalities and clinical complications.The curvature of the cervical spine is one of the important factors affecting the effective movement and function of cervical vertebra.Cervical malalignment may result in the pathological changes of kinematics and accelerate the degeneration of functional motion unit.However,there is not clear if there is a cause-and-effect relationship between the cervical alignment subtypes and disc degeneration.Methods:From April 2015 to January 2016,120 patients(age 20-80)who presented with cervical disorders were enrolled.patients all received both a cervical MRI and a cervical radiograph(X-ray)during a single visit.We categorized the cervical sagittal alignment into three types: type Ⅰ : lordosis,type Ⅱ : straight,and type Ⅲ: kyphosis.The degree of disc degeneration was graded using T2-weighted images,the discs were then divided into two groups: non-degenerated group(n D:grade0 and grade1)and degenerated group(D:grade2 and grade3).The chi-square test with post-hoc based on adjusted standardized residuals was used to compare the frequency of different disc degeneration degrees across the three spinal subtypes.Results:There was a significant difference among the three subtypes,regardless of disc level.We compared the frequency between the disc degeneration subtypes at each disc level,Significant differences among subtypes were found at C4-5(X2=7.263,p=0.026)、 C5-6(X2=6.582,p=0.037)、C6-7(X2=10.714,p=0.005).We also found that both type Ⅱ and type Ⅲ sagittal alignment subtypes had higher disc degeneration than type Ⅰ.Conclusions:Although each sagittal alignment subtype of cervical may be normal,we believe that normal lordotic alignment of cervical spine is the best。The sagittal alignment subtypes is significantly associated with cervical disc degeneration.The straight alignment is more likely to cause C5-6 disc degeneration,and the degeneration of C4-5 may appear earlier in kyposis alignment.