Changes Of Cervical Spine Sagittal Alignment After Open-door Expansive Laminoplasty And Relationship Between The Changes And Clinical Efficacy

Objective:To explore changes of cervical spine sagittal alignment after open-door expansive laminoplasty（LAMP）for multilevel cervical spondylotic myelopathy and cervical ossification of posterior longitudinal ligament,and relationship between the changes and clinical efficacy.Methods:The clinical and radiological data were analyzed retrospectively for 64 patients undergoing open-door expansive laminoplasty with mini-titanium plate between January2015 and December 2017 and who were followed up for at least 1 year,64patients divided into 2 groups according to diagnosis[multilevel cervical spondylotic myelopathy（mCSM）group:35 patients（20 men and 15 women）,and cervical ossification of the posterior longitudinal ligament（cOPLL）group:29 patients（10 men and 19 women）].All the cervical sagittal parameters including C_O-2Cobb angle,C_2-7Cobb angle,C_2-7 sagittal vertical axis(C_2-7SVA),C₇ slope（C₇S）measured on the standing lateral radiographs of cervical spine were recorded preoperation and at the last follow-up.The correlation between cervical sagittal alignment and clinical outcomes were analyzed by using Pearson correlation analysis.Results:At last follow-up,JOA,NDI and VAS scores in the two groups were improved significantly when compared with the preoperative scores（all P<0.05）.Between preoperative and last follow-up measurements,C_2-7SVA values and C_O-2Cobb angle in both groups slightly increased,but C_2-7SVA values in the cOPLL group increased more significantly（2.5mm vs 1.6mm,P<0.05）.However,the C_2-7Cobb angle decreased by 2.2°in the mCSM group and by 1.2°in the OPLL group（P<0.05）,and the C₇S in the mCSM group decreased and that in the cOPLL group unchanged postoperatively（P<0.05;P=0.184）.There were no correlations between the change in cervical sagittal pa rameters(C_O-2Cobb angle,C_2-7 Cobb angle,C_2-7SVA and C₇S)and the improvements of clinical outcomes（JOA,NDI and VAS）in the two groups（all P>0.05）.Conclusion:This study demonstrated that cervical open-door laminoplasty with mini-titanium plate has less impact on the cervical sagittal alignment in the short term.After surgery,cervical sagittal alignment often tends to kyphotic change.However,the change of cervical sagittal alignment after laminoplasty was not clearly correlated with clinical outcomes.