Chih-Kai Hong1, Wei-Ren Su2,3. 1. Department of Orthopaedic Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng-Li Road, Tainan City, 70428, Taiwan. 2. Department of Orthopaedic Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng-Li Road, Tainan City, 70428, Taiwan. suwr@ms28.hinet.net. 3. Medical Device R & D Core Laboratory, National Cheng Kung University Hospital, Tainan, Taiwan. suwr@ms28.hinet.net.