Tomohiko Moteki1, Takashi Yanagawa2, Kenichi Saito1. 1. Department of Orthopaedic Surgery, Gunma University Graduate School of Medicine, 3-39-22, Showa, Maebashi, Gunma, 371-8511, Japan. 2. Department of Orthopaedic Surgery, Gunma University Graduate School of Medicine, 3-39-22, Showa, Maebashi, Gunma, 371-8511, Japan. Electronic address: tyanagaw@gunma-u.ac.jp.