Influence of the Ratio of C2-C7 Cobb Angle to T1 Slope on Cervical Alignment After Laminoplasty

Xiang-Yu Li; Chao Kong; Xiang-Yao Sun; Ma-Chao Guo; Jun-Zhe Ding; Yi-Ming Yang; Shi-Bao Lu

doi:10.1016/j.wneu.2018.12.181

Influence of the Ratio of C2-C7 Cobb Angle to T1 Slope on Cervical Alignment After Laminoplasty

World Neurosurg. 2019 Apr:124:e659-e666. doi: 10.1016/j.wneu.2018.12.181. Epub 2019 Jan 14.

Authors

Xiang-Yu Li¹, Chao Kong², Xiang-Yao Sun¹, Ma-Chao Guo¹, Jun-Zhe Ding¹, Yi-Ming Yang¹, Shi-Bao Lu³

Affiliations

¹ Department of Orthopedics, Xuanwu Hospital, Capital Medical University, Beijing, China.
² Department of Orthopedics, Xuanwu Hospital, Capital Medical University, Beijing, China; National Clinical Research Center for Geriatric Diseases, Beijing, China.
³ Department of Orthopedics, Xuanwu Hospital, Capital Medical University, Beijing, China; National Clinical Research Center for Geriatric Diseases, Beijing, China. Electronic address: spinelu@163.com.

PMID: 30654159
DOI: 10.1016/j.wneu.2018.12.181

Abstract

Purpose: To assess the relationship between the ratio of C2-C7 Cobb angle to T1 slope (CL/T1S) and cervical alignment changes after laminoplasty.

Methods: 78 consecutive patients with cervical myelopathy who underwent laminoplasty were enrolled. All patients with preoperative and follow-up cervical spine lateral x-ray images available for review were recruited in this study. Imaging data included C2-C7 Cobb angle, T1 slope, and cervical sagittal vertical axis (cSVA). All patients were classified into low-ratio group (bottom 25% of CL/T1S), fair-ratio group (middle 50% of CL/T1S), and high ratio group (top 25% of CL/T1S) according to CL/T1S ratio. The recovery rate was calculated based on the Japanese Orthopedic Association score.

Results: The preoperative C2-C7 Cobb angle had significant correlations with the T1 slope (r = 0.528). Kyphotic alignment changes in the group with a high ratio of CL/T1S was greater than that of the other 2 groups (P < 0.001). The incidence of postoperative kyphosis in the group with a low ratio of CL/T1S was higher than that of the other 2 groups (P < 0.001). There was no postoperative kyphosis in the fair-ratio group. The surgical outcome in the low-ratio CL/T1S group and the high-ratio CL/T1S group was poorer than that in the fair-ratio CL/T1S group (P = 0.005).

Conclusions: The cervical alignment was kept well in the mid-range CL/T1S ratio group after laminoplasty. Patients with a high CL/T1S ratio were more likely to present with kyphotic alignment changes. Patients with a low CL/T1S ratio were more likely to have postoperative kyphosis.

Keywords: Cervical spondylotic myelopathy; Kyphotic alignment change; Laminoplasty; Sagittal alignment; Sagittal balance.