1 Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Japan; Department of Orthopedic Surgery, Niigata City General Hospital, Niigata City, Japan.
2 Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Japan. Electronic address: masayuki-ohashi@ksh.biglobe.ne.jp.
3 Department of Orthopedic Surgery, Nagaoka Chuo General Hospital, Nagaoka City, Japan.
4 Department of Orthopedic Surgery, Niigata Prefectural Central Hospital, Joetsu City, Japan.
5 Spine Center, Department of Orthopedic Surgery, Niigata Central Hospital, Niigata City, Japan.
6 Department of Orthopedic Surgery, Niigata City General Hospital, Niigata City, Japan.
7 Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Japan.