1. Department of Orthopaedic Surgery, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
2. Department of Neurosurgery, CHA University School of Medicine, CHA Bundang Medical Center, Seongnam-si 13496, Republic of Korea
3. Department of Orthopedic Surgery, School of Medicine, Tokai University, 143 Shimokasuya, Isehara 259-1193, Japan