1. Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
2. Department of Neurosurgery, Spine and Joint Research Institute, Guro Cham Teun Teun Hospital, Seoul, Republic of Korea
3. Department of Neurosurgery, Spine and Spinal Cord Research Institute, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea