Copyright © 2020 by the Korean Spinal Neurosurgery Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/).
Except where otherwise noted, this item's license is described as Copyright © 2020 by the Korean Spinal Neurosurgery Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/).