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 Orthopaedic Surgery, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
3. Department of Orthopaedic Surgery, College of Medicine, Yonsei University, Seoul, Korea.
4. Department of Orthopaedic Surgery, Keimyung University Dongsan Hospital, Keimyung University School of Medicine, Daegu, Korea.
5. Department of Orthopaedic Surgery, Yeson Hospital, Bucheon, Korea.