Use Of Digital Tomosynthesis For The Evaluation Of Sagittal Balance Of Cervical Spine After Double-segment Operation Of Cervical Spondylotic Myelopathy

ObjectiveNormal cervical spine sequence plays a vital role in maintaining the stability and normal activity of cervical spine biomechanics.Especially for patients with cervical spondylotic myelopathy(CSM),sagittal curvature after cervical spine surgery has an important correlation with neck pain,neurological improvement and health-related quality of life score(HRQOL).Therefore,the correct measurement of cervical sagittal parameters before and after surgery is of great significance for the reasonable correction of cervical curvature and the evaluation of postoperative effects.Most of the previous studies adopted plain radiograph to measure and analyze the cervical sagittal parameters.However,due to the special anatomical structure of the cervicothoracic junction and the shielding of shoulder joints and cervical soft tissues,it is difficult to accurately measure the sagittal parameters of the cervicothoracic junction.Digital Tomosynthesis(DTS)can continuously shoot through multiple angles to clearly display vertebral images such as C7 and T1,which can accurately measure the cervical sagittal parameters.In this study,DTS was used to take images of patients with spinal cervical spondylosis who underwent anterior cervical discectomy and with fusion to measure the sagittal parameters of the cervical spine before and after operations,and compare and explore the relationship between parameter changes and functional recovery.MethodA total of 76 patients who underwent double-segment surgery at the First Affiliated Hospital of Zhengzhou University due to Cervical Spondylotic Myelopathy between January 2018 and December 2018 were collected.Patients were followed up regularly at 1,3,6,and 12 months after surgery,and all patients underwent shooting DTS images of cervical spine and clinical evaluation before and after each follow-up.The parameters and indicators were measured before surgery and at the last follow-up.The clinical evaluation indicators involve VAS,NDI and JO A.The image measurement parameters include Cobb’s O-C2 angle(CobbO-C2),C2～C7 Sagittal vertical axis(C2-7SVA),Cobb’s C2-7 angle(CobbC2-7),Thoracic inlet angle(TIA),T1 slope(T1S)and Neck tilt(NT).Calculate the median value of T1S measured before surgery and divide patients into 2 groups based on the value:High T1S group is greater than its median and low T1S group is less than its median.Use paired t test and Pearson correlation coefficient to compare the differences and correlations between pre-and post-operative measurement results and clinical evaluation indicators in the two groups.ResultsAmong the parameters evaluated before surgery and at the last follow-up,except for TIA,which had no statistically significant difference(P>0.05),the remaining parameters including CobbO-C2,CobbC2-7,C2-7SVA,T1S,NT,T1S and clinical evaluation indicators JOA,VAS and NDI had statistical differences(P<0.05).Postoperative parameters including CobbO-C2,TIA,JOA improvement rate and VAS had no statistical difference between the high T1S group and the low T1S group(P>0.05).However,there were significant differences in CobbC2-7,C2-7SVA,T1S,NT and NDI between the two groups(P<0.05).In terms of correlation,there is a positive correlation between △O-C2 and the improvement rate of JOA(r=0.405);There is a correlation between △C2-7SVA and △T1S,△VAS and △NDI,The r values were-0.222,0.274 and 0.200,respectively;There was a positive correlation between △VAS and △NDI(r=0.558).Conclusion1.The cervical spine lateral images taken using Digital Tomosynthesis can accurately measure the parameters of the cervical sagittal position,which has a unique advantage over ordinary X-rays.2.Sagittal parameters of cervical spine in patients with double-segment cervical spondylotic myelopathy changed significantly after anterior surgery.The cervical lordosis was significantly larger than that before surgery,and all clinical evaluation indexes were improved.3.CobbO-C2 and C2-7SVA is closely related to the clinical symptoms,suggesting that the influence of head weight must be fully considered when formulating the cervical spine surgery plan,which can help surgeon reasonably reconstructed the cervical curvature during the operation.