J Orthop Sci 2020 Dec 14. Epub 2020 Dec 14.
Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Aichi, Japan; Japanese Organization for the Study for Ossification of Spinal Ligament (JOSL), 1-5-45 Yushima, Bunkyo-ku, 113-8519, Tokyo, Japan. Electronic address: