1. Department of Neurosurgery, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, Korea.
2. Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Spine Hospital, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Neurosurgery, Spine and Spinal Cord Institute, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.