1. Department of Orthopaedic Surgery, Kohnodai Hospital, National Center for Global Health and Medicine , 1-7-1 Kohnodai, Ichikawa city, Chiba 272-8516 , Japan
2. Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University , 1-8 Inohana, Chuo-ku, Chiba city, Chiba 260-0856 , Japan