1. Spine Center and Department of Orthopaedic Surgery, Seoul National University College of Medicine and Seoul National University Bundang Hospital, Seongnam, Korea.
2. Department of Orthopedic Surgery, Korea University Ansan Hospital, Ansan, Korea.
3. Department of Emergency Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea.
4. Department of Orthopaedic Surgery, Soonchunhyang University Bucheon Hospital, Bucheon, Korea.
5. Department of Statistics and Actuarial Science, Soongsil University, Seoul, Korea.