1. Department of Orthopedic Surgery, Chung-Ang University, Seoul 140-757, Korea
2. Department of Orthopedic Surgery, Seoul National University, Seoul 140-757, Korea
3. The Catholic University of Korea, Seoul 140-757, Korea
4. Sungkyunkwan University and Samsung Medical Center, Seoul 140-757, Korea
5. Ewha Woman's University Hospital, Seoul 140-757, Korea
6. Life Science Research Center, SK Chemicals, Seoul 140-757, Korea
7. Clinical Trial Center, Clinical Research Institute, Seoul National University Hospital, Seoul 140-757, Korea
8. Department of Preventive Medicine, Seoul National University College of Medicine, Seoul 140-757, Korea