Abstract: Objective To investigate clinical efficacy and cervical sagittal balance after posterior open-door laminoplasty with mini-plate and anchor.Methods From January 2016 to December 2017, 61 patients with multilevel cervical spondylotic myelopathy were retrospectively studied in our department. According to the different fixation methods, all patients were divided into cervical posterior open-door Centerpiece fixation group(group A, 29 cases)and cervical posterior open-door anchor fixation group(group B, 32 cases).The important clinical data were recorded, including operation time, intraoperative bleeding volume, Visual Analogue Score (VAS) of cervical pain, Japanese Orthopaedic Association (JOA) score, improvement rate of spinal nerve function and Neck Disability Index (NDI) of cervical spine at pre- and post-operation of 12 months. This parameters were compared at pre-operation, 3 days and 12 months after surgery, which were the distance between the vertical axis of C2 sagittal plane and the posterior superior edge of C7 (C2-7 SVA), the inclusion angle of tangent between C2 and C7 trailing edge (C2-7 Cobb angle), and the intersection angle between the upper edge of T1 and the horizontal line (T1 Slope).Results The age, disease duration, VAS, JOA score and NDI score were no statistical difference between the two groups before operation(P>0.05). There were no significant difference in operation time and bleeding volume between the two groups(P>0.05). After surgery, the VAS and NDI score in the two groups were significantly lower than those before operation, but the JOA score was higher. At 12 months after surgery,the NDI score in group A was better than that in group B(P<0.05), while there was no statistical difference in the others between the two groups (P>0.05).In radiological parameters, compared with pre- and post-operation, C2-7 SVA and T1 Slope in both groups increased, while the C2-7 Cobb angle decreased(P<0.05). But there were statistical differences in C2-7 SVA at 12 months after operation(P<0.05), while other parameters were no differences (P>0.05). Before and 12 months after operation, C2-7 SVA difference was negatively correlated with NDI score difference (P<0.05). Conclusion Both surgical methods caused anteversion of cervical spine, but cervical sagittal balance and function after mini-plate is better than that of anchor.

Key words: posterior open-door laminoplasty, mini-plate, anchor, cervical spine, sagittal balance