Relationship between changes in cervical sagittal parameters and adjacent segment degeneration after cervical microendoscopic laminoplasty for cervical spondylotic myelopathy

English Keywords:Cervical spondylotic myelopathy  Cervical microendoscopic laminoplasty  Sagittal alignment  Adjacent segment degeneration

English Abstract:

  【Abstract】 Objectives: To explore the changes of cervical sagittal parameters after cervical microendoscopic laminoplasty(CMEL) of cervical spondylotic myelopathy(CSM) and their relationship with adjacent segment degeneration(ASD). Methods: The clinical data of CSM patients(n=111) treated with CMEL in our Hospital from January 2019 to June 2023 were retrospectively analyzed. The clinical data(age, gender, number of diseased segments, diabetes mellitus, cervical MRI T2WI spinal cord strong signal, operation time, etc) of patients were collected, and the visual analogue scale(VAS), neck disability index(NDI), Japanese Orthopaedic Association(JOA) of patients before and at 12 months after operation were recorded, and the sagittal parameters [C2-7 Cobb angle, C2-7 sagittal vertical axis(SVA), T1 slope(T1S), thoracic inlet angle(TIA)] of cervical spine were measured before and at 12 months after operation on X-ray images. Pearson analysis was used to analyze the correlation between the difference of cervical sagittal parameters before and after surgery and the difference of JOA, NDI and VAS scores. Patients were divided into ASD group(n=40) and non ASD group(n=71) according to whether ASD occurred during the follow-up period, and the above parameters were compared between the two groups, and the cervical sagittal parameters with statistical differences between the two groups were analyzed by the multivariate logistic regression model, with the correlation classification as the independent variable and the postoperative ASD as the dependent variable according to the triad method. Restricted cubic splines(RCS) model was used to analyze the dose-response relationship between postoperative C2-C7 Cobb angle and T1S and the risk of postoperative ASD. C-Statistics, net reclassification index or improvement(NRI) and integrated discrimination improvement(IDI) were used to evaluate the predictive efficacy of each index for postoperative ASD. Results: There were statistically significant differences in C2-C7 Cobb angle, C2-C7 SVA, JOA score, NDI index and VAS score between before operation and 12 months after operation(P<0.05), but there were no statistically significant differences in T1S and TIA(P>0.05). Pearson analysis showed that C2-C7 Cobb angle difference was positively correlated with JOA score difference(P<0.05), and negatively correlated with NDI and VAS score differences(P<0.05); There was no correlation between C2-C7 SVA, T1S, TIA differences and JOA score, NDI, VAS score differences(P>0.05). There were significant differences in age, T2WI strong signal, preoperative JOA score, preoperative neck pain VAS score, preoperative upper limb pain VAS score, preoperative NDI index, C2-C7 Cobb angle 12 months after operation, and T1S 12 months after operation between ASD group(n=40) and non ASD group(n=40)(P<0.05), and there were no significant differences between groups in gender, BMI, smoking, drinking, diabetes, number of diseased segments, operation time, intraoperative blood loss, preoperative cervical sagittal parameters, C2-C7 SVA 12 months after operation, and TIA 12 months after operation(P>0.05). According to the triad method, 12 months after operation, the C2-C7 Cobb angle<15.30° was divided into Q1 group, 15.30°-18.65° was Q2 group and >18.65° was Q3 group; 12 months after operation, T1S<22.45° was Q4 group, 22.45°-25.60° was Q5 group and >25.60° was Q6 group; With C2-C7 Cobb angle and T1S classification as independent variables and postoperative ASD as dependent variables, multivariate logistic regression analysis showed that after adjusting for confounding factors, the risk of postoperative ASD in group Q3 was significantly lower than that in group Q1(P<0.05), and that in group Q6 was significantly lower than that in group Q4 according to T1S classification(P<0.05). RCS analysis showed that there was a non-linear dose-response relationship between C2-C7 Cobb angle at 12 months after surgery, T1S at 12 months after surgery and postoperative ASD risk(P<0.05). The joint evaluation showed that the prediction ability of cervical sagittal parameters(C2-C7 Cobb angle and T1S at 12 months after operation) was the best, and the results of C-statistics, NRI and IDI were consistent. Conclusions: The C2-C7 Cobb angle increases and C2-C7 SVA shortens in patients with CSM after CMEL; C2-C7 Cobb angle is significantly correlated with the improvement of clinical symptoms. There is a nonlinear dose-response relationship between C2-C7 Cobb angle and T1S and ASD risk 12 months after operation. Cervical sagittal parameters combined with clinical indicators have the best predictive effect on ASD risk.