Kazuaki Suzuki1, Junichirou Hamada2, Yoshihiro Hagiwara3. 1. Department of Orthopedic Surgery, Sendai Hospital of East Japan Railway Company, 1-1-5 Itsutsubashi, Aoba-ku, Sendai, Miyagi, 980-8508, Japan. 2. Department of Orthopaedic Surgery, Kuwano Kyoritsu Hospital, 2-9-18 Shima, Koriyama, Fukushima, 963-8034, Japan. Electronic address: i-hamada@koriyama-h-coop.or.jp. 3. Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8574, Japan.