1. Department of Orthopaedic Surgery, Faculty of Medicine; University of Tsukuba; Tsukuba Ibaraki Japan
2. Department of Orthopaedic Surgery and Rehabilitation; Tsukuba Gakuen Hospital; Tsukuba Ibaraki Japan
3. Department of Orthopaedic Surgery; Tsukuba Central Hospital; Ushiku Ibaraki Japan
4. Kenpoku Medical Center Takahagi Kyodo Hospital, Kamitezuna; Takahagi Ibaraki Japan
5. Biomaterials Unit, National Institute for Materials Science; Tsukuba Ibaraki Japan