. 2018 Feb 7;12(1):12–17. doi: 10.4184/asj.2018.12.1.12
Copyright © 2018 by Korean Society of Spine Surgery
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.