1. Department of Orthopaedic Surgery, National Hospital Organization Okayama Medical Center, 1711-1, Tamasu, Kita-ku, Okayama 701-1192, Okayama, Japan
2. Department of Orthopaedic Surgery, Kameoka Municipal Hospital, 1-1, Shinonoda, Shino-cho, Kameoka 621-8585, Kyoto, Japan