1. Joint Reconstruction Center, Seoul National University, Bundang Hospital, 300, Gumidong, Bundanggu, Seongnamsi, Gyunggido, Korea.
2. Department of Orthopaedic Surgery, Seoul National University, Hospital, 28 Yeongongdong, Chongnogu, Seoul, Korea.
3. Department of Statistics, Korea University, 5-1, Anamdong, Seongbukgu, 136-701 Seoul, Korea.