1. Department of Orthopaedic Surgery, Seoul National University Children’s Hospital, 28 Yongon-dong Chongno-gu, Seoul 110-744, Korea.
2. Department of Orthopaedic Surgery, University of Ulsan College of Medicine, Asan Medical Centre, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea.