Accuracy of Realigned K-line for Predicting Surgical Outcomes After Laminoplasty in Patients With Degenerative Cervical Myelopathy

Qifei Duan; Guoyan Liang; Chong Chen; Yongyu Ye; Xiaoqing Zheng; Changxiang Liang; Yunbing Chang

doi:10.1177/21925682221150908

Accuracy of Realigned K-line for Predicting Surgical Outcomes After Laminoplasty in Patients With Degenerative Cervical Myelopathy

Global Spine J. 2023 Jan 10:21925682221150908. doi: 10.1177/21925682221150908. Online ahead of print.

Authors

Qifei Duan^{1

2}, Guoyan Liang², Chong Chen², Yongyu Ye², Xiaoqing Zheng², Changxiang Liang², Yunbing Chang^{1

2}

Affiliations

¹ The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China.
² Department of Spine, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China.

PMID: 36626180
DOI: 10.1177/21925682221150908

Abstract

Study design: A prospective cohort study.

Objectives: To report a new index, the realigned K-line, for predicting surgical outcomes after laminoplasty in patients with degenerative cervical myelopathy (DCM).

Methods: One hundred twenty-eight patients with DCM undergoing laminoplasty were enrolled from January 2018 to April 2021 in our department. A realigned K-line was defined as the line connecting the midpoints of the spinal cord between C2 and C7 on realigned T1-weighted magnetic resonance imaging. The minimum interval between the anterior compression factors of the spinal cord and the realigned K-line (INT_rea), and the modified K-line (INT_mod) were measured. A logistic regression analysis was performed to identify factors associated with unsatisfactory surgical outcomes. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) was applied to evaluate the reliability of the multivariate logistic regression model.

Results: Univariate analysis showed that the score for the bladder function section of the Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire, numeric rating scale scores for arm pain, and INT_rea might be related to the Japanese Orthopaedic Association (JOA) recovery rate (RR) not achieving the minimal clinically important difference (MCID) (P < .05). Only INT_rea (odds ratio = .744, P < .05) was an independent preoperative factor related to the JOA RR not achieving the MCID (area under the curve, .743). A cutoff of 5.0 mm for INT_rea had an accuracy of 71.9% and specificity of 80.3% for predicting the JOA RR not achieving the MCID.

Conclusions: INT_rea is an independent preoperative risk factor related to the JOA RR not achieving the MCID in patients with DCM. A cutoff point of 5.0 mm is most appropriate for alerting spine surgeons to a high likelihood of the JOA RR not achieving the MCID.

Keywords: anterior compression of the spinal cord; degenerative cervical myelopathy; laminoplasty; modified k-line; postoperative clinical outcomes; realigned k-line.