1. Department of Neurosurgery, Konyang University Hospital, Konyang University College of Medicine, Daejeon, Korea.
2. Department of Neurosurgery, Spine Center, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
3. Department of Orthopaedic Surgery, Spine Service, New York Presbyterian Hospital, Columbia University College of Physicians and Surgeons, New York, USA.