1. Department of Neurosurgery, The Leon Wiltse Memorial Hospital, Anyang, Korea
2. Department of Neurosurgery, Wooridul Spine Hospital, Seoul, Korea
3. Department of Neurosurgery, Seoul St. Mary's Hospital, The Catholic University, Seoul, Korea
4. Department of Orthopeadics, Wooridul Spine Hospital, Seoul, Korea
5. Department of Clinical Research, Wooridul Spine Hospital, Seoul, Korea