Posterior open-door laminoplasty secured with titanium miniplates vs anchors: a comparative study of clinical efficacy and cervical sagittal balance
Authors: Li Dongyue , Hai Yong , Meng Xianglong , Yang Jincai , Yin Peng 
Published: November 2019

Abstract
Objective
Posterior open-door laminoplasty (PODL) is a common procedure for treating multilevel cervical spondylotic myelopathy (MCSM). Little information is available regarding the cervical sagittal balance and surgical efficacy of PODL when securing with different methods. Therefore, this study aims to investigate the clinical outcomes and the changes in cervical sagittal parameters and balance associated with PODL secured with titanium miniplates vs anchors.

Method
A retrospective analysis was performed on the clinical data of 79 patients with MCSM who were treated in our institution from January 2015 to December 2016. Among them, 42 patients were treated by PODL secured with titanium miniplates (group A) and 37 patients by PODL secured with anchors (group B). Surgical time, intraoperative blood loss, hospital stay, hospitalized cost, VAS scores of neck pain, JOA scores, neck disability index (NDI), and improvement rate of spinal neurological function (IRNF) were recorded before surgery and at 12 months after surgery. Before surgery, at 1 month and 2 years after surgery, the following radiological parameters were recorded and compared on the lateral cervical X-ray images: the distance from the vertical axis of C2 sagittal plane to 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).

Result
Comparing the two groups, there were no significant differences in surgical time, intraoperative blood loss, hospital stay, VAS, JOA, and NDI scores before surgery (P > 0.05); however, the hospitalized cost of group A were much higher than those of the group B (P < 0.05). At 2 years after surgery in the two groups, there was a significant reduction in VAS and NDI scores (P < 0.05), and JOA scores increased significantly (P < 0.05). In addition, there were no significant differences in VAS, JOA and IRNF between the two groups (P > 0.05); however, NDI scores of group A were better than those of group B (P < 0.05). In radiological parameters, before surgery, the two groups showed no significant differences in C2-7 SVA, C2-7 Cobb angle, and T1 slope (P > 0.05); however, after surgery, C2-7 SVA and T1 slope increased (P < 0.05), while C2-7 Cobb angle decreased (P < 0.05). At 2 years after surgery, the two groups did not differ significantly in C2-7 Cobb angle and T1 slope (P > 0.05), while C2-7 SVA of group A was superior to that of group B (P < 0.05). The difference value of C2-7 SVA measured before and after surgery was correlated negatively with that of NDI scores (P < 0.05).

Conclusion
PODL secured with titanium miniplates or anchors achieved good clinical efficacy in the treatment of MCSM. However, the patients with miniplates feel a better cervical functional status, while those with anchors spend less on hospitalization. Both methods lead to anteversion of cervical spine, but cervical sagittal balance after miniplates is better than that of anchors.