1. Department of Orthopedic Surgery, Asan Medical Center, Seoul, Korea.
2. Department of Orthopedic Surgery, Seoul National University Bundang Hospital, Seongnam, Korea.
3. Office of Health Services Research, National Evidence-Based Healthcare Collaborating Agency, Seoul, Korea.
4. Department of Information Statistics, Andong National University, Andong, Korea.
5. Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul, Korea.
6. Medical Research Center, Seoul National University, Seoul, Korea.