Retrospective Study
Copyright ©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Feb 6, 2022; 10(4): 1172-1181
Published online Feb 6, 2022. doi: 10.12998/wjcc.v10.i4.1172
Sequential sagittal alignment changes in the cervical spine after occipitocervical fusion
Ce Zhu, Lin-Nan Wang, Tai-Yong Chen, Li-Li Mao, Xi Yang, Gan-Jun Feng, Li-Min Liu, Yue-Ming Song
Ce Zhu, Lin-Nan Wang, Xi Yang, Gan-Jun Feng, Li-Min Liu, Yue-Ming Song, Department of Orthopedics Surgery and Orthopedics Research Institute, West China Hospital of Sichuan University, Chengdu 610041, Sichuan Province, China
Tai-Yong Chen, Department of Orthopedics Surgery, The Second Affiliated Hospital of Zunyi Medical University, Zunyi 563000, Guizhou Province, China
Li-Li Mao, Department of Ultrasound, Hospital of Traditional Chinese Medicine Affiliated to Southwest Medical University, Luzhou 646000, Sichuan Province, China
Author contributions: Zhu C and Wang LN conceptualized and designed the study, and drafted the initial manuscript; Chen TY and Mao LL carried out the initial analyses, and reviewed and revised the manuscript; Yang X, Feng GJ, Liu LM, and Song YM coordinated and supervised the data collection, and critically reviewed and revised the manuscript for important intellectual content; Zhu C and Wang LN contributed equally to this work; all authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.
Supported by The Key Research and Development Project of Science & Technology Department of Sichuan Province, No. 2017SZ0046, No. 2017SZDZX0021, and No. 2021YFG0240.
Institutional review board statement: The study was reviewed and approved by the Ethics Committee of West China Hospital, Sichuan University (No. 2019762).
Informed consent statement: Written informed consent was obtained from the patients for publication of this case report and any accompanying images.
Conflict-of-interest statement: The authors declare they have no conflicts of interest to disclose.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Xi Yang, MD, Associate Professor, Department of Orthopedics Surgery and Orthopedics Research Institute, West China Hospital of Sichuan University, No. 37 Guoxue Road, Chengdu 610041, Sichuan Province, China. formosa88@163.com
Received: September 6, 2021
Peer-review started: September 6, 2021
First decision: October 29, 2021
Revised: November 13, 2021
Accepted: December 31, 2021
Article in press: December 31, 2021
Published online: February 6, 2022
Abstract
BACKGROUND

There are few studies regarding sequential changes in the sagittal alignment of the upper and lower cervical regions of the spine after occipitocervical fusion (OCF). In addition, no comparisons of cervical sagittal alignment (CSA) between patients with craniocervical junction disorders (CJDs) and normal populations have been reported.

AIM

To compare the CSA of patients with CJDs with that of normal controls and investigate the sequential changes in the CSA of the upper and lower cervical spine after OCF.

METHODS

Eighty-four patients who underwent OCF (OCF group) and 42 asymptomatic volunteers (control group) were included. Radiographic parameters, including the occipital to C2 angle (O-C2a), occipital and external acoustic meatus to axis angle (O-EAa), C2–7 angle (C2-7a), and pharyngeal inlet angle (PIA), were measured and compared pre- and postoperatively. The correlations among the parameters were analyzed using Pearson’s correlation test.

RESULTS

The O-C2a and PIA of the OCF group were smaller than those of the control group, while their O-EAa and C2-7a values were larger than those of the normal controls. There were no significant differences in O-C2a, C2-7a, or PIA in the OCF group at baseline, 1 mo, or the final follow-up after surgery. The Pearson’s correlation results showed that there were significant correlations between the O-C2a and C2Ta, C2-7a, C2-7 sagittal vertical axis (SVA), and PIA at 1 mo after OCF surgery and between O-C2a and O-EAa, C2Ta, C2-7a, C2-7 SVA, and PIA at the final follow-up.

CONCLUSION

Patients with CJDs have a more kyphotic upper CSA and a more lordotic lower CSA than normal controls. The effectiveness of OCF surgery in restoring CSA may be limited by the realignment of the craniocervical junction being neglected. The reduction in O-C2a after OCF surgery may increase C2-7a and decrease PIA.

Keywords: Sagittal alignment, Occipitocervical fusion, Craniocervical disorders, Cervical spine, Dysphagia

Core Tip: Patients with craniocervical junction disorders had a more kyphotic upper cervical sagittal alignment (CSA) and a more lordotic lower CSA than normal controls: The decreased lordosis of the upper cervical spine caused by the weakness of paraspinal muscles and ligaments (OC2a↓) led to the gravity center of the cranium moving forward (C2Ta↑). To maintain horizontal gaze and normal C2-7 sagittal vertical axis, the lordosis of the lower cervical spine was increased (C2-7a↑). Moreover, the restoration of CSA after occipitocervical fusion (OCF) may be limited by neglecting the realignment of craniocervical junction. The reduction of the O-C2a after OCF would increase the C2-7a and decrease the pharyngeal inlet angle and lead to postoperative dysphagia.