1. Department of Orthopaedic Surgery, Otsu Red Cross Hospital, Nagara 1-1-35, Otsu 520-0046, Japan
2. Department of Orthopaedic Surgery, Kyoto University, Kyoto, Japan
3. Division of Material Chemistry, Faculty of Engineering, Kyoto University, Kyoto, Japan
4. Nippon Electric Glass Co. Ltd., Otsu, Japan