1Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
2Department of Orthopaedic Surgery, National Hospital Organization, Kyushu Medical Center, 1-8-1 Jigyouhama chuo-ku, Fukuoka, Fukuoka 811-1395, Japan
3Product Research Department, Kamakura Research Laboratories, Chugai Pharmaceutical Co., Ltd., 200 Kajiwara, Kamakura, Kanagawa 247-8530, Japan