Changes Of Cervical Sagittal Balance After Cervical Expansive Open-door Laminoplasty

Objective: To investigate the changes of cervical sagittal balance after cervical expansive open-door laminoplasty,to analyze the correlation between sagittal balance parameters and JOA improvement rate,and to provide a reference for the prediction of clinical efficacy.Methods:48patients(28 men and 18 women)with cervical spondylotic myelopathy or cervical ossification of the posterior longitudinal ligament admitted into the First Affiliated Hospital of Chongqing Medical University from March2016 to March 2018 underwent cervical expansive open-door laminoplasty.Compare preoperative and postoperative JOA improvement rate and cervical sagittal parameters including C0-C2 Cobb angle,C2-C7 Cobb angle,C2-C7 SVA and T1-Slope,and explore the correlation between sagittal balance parameters and JOA improvement rate.The median number was calculated according to the T1-Slope value measured by the X-ray of the patient's preoperative lateral position.According to the median value,it was divided into high T1-Slope group and low T1-Slope group.Calculate JOA improvement rate,and compare the changes of C2-C7 Cobb.Results:The follow-up period was 2-18 months,with an average follow-up of 11.1 mouths.The postoperative JOA score was 14.22 points,and the preoperative JOA score was 11.98 points,the value changes were statistically significant(P < 0.01),and the JOA improvement rate was 44.6%.At the last follow-up,C0-C2 Cobb angle,C2-C7 SVA and T1-Slope were significantly higher than those before surgery(P < 0.01).The average value of C2-C7 Cobb angle at the last follow-up was 14.97°,and the preoperative was 16.86°,which was not statistically significant(P=0.175).The increase of C2-C7 SVA was positively correlated with the increase of C0-C2 Cobb angle(r=0.309,P=0.036),and also positively correlated with the increase of T1-Slope(r=0.402,P=0.006).The preoperative JOA score was negatively correlated with C2-C7 SVA(r=-0.397,P=0.006).There was no significant correlation between postoperative JOA score and C2-C7 SVA(P=0.071).The preoperative C2-C7 Cobb angle was positively correlated with T1-Slope(r=0.433,P=0.003),but not correlated with C2-C7 SVA(P=0.995).The postoperative JOA improvement rate was 37.69% in the high T1-Slope group and 55.50% in the low T1-Slope group,the value changes were statistically significant(P < 0.01).the C2-C7 in the high T1-Slope group and the low T1-Slope group both were lower than that before surgery,but it was not statistically significant(P>0.05).Conclusion:Cervical expansive open-door laminoplasty has a significant effect on cervical postoperative sagittal balance.Most of the patients arecharacterized by cervical anterior tilt and compensatory extension of the upper cervical spine.Preoperative T1 S value provides a reference for postoperative outcome.When preoperative T1-Slope is high,the tendency of cervical curvature loss after surgery is greater,which may cause sagittal imbalance of the cervical spine and affect postoperative nerve,so patients with preoperative cervical sagittal imbalance are not suitable for laminoplasty.In this case,anterior surgery can be better than laminoplasty.C2-C7 SVA can be used for the evaluation of preoperative patient symptoms,but not for the evaluation of postoperative neurological function.During the operation,attention should be paid to protecting the posterior muscle ligament complex,which is beneficial to maintain the sagittal balance of the cervical spine after operation.