[1] Nagoya Univ, Grad Sch Med, Dept Orthopaed Surg, Showa Ku, 65 Tsurumai Cho, Nagoya, Aichi 4668550, Japan
[2] Japanese Org Study Ossificat Spinal Ligament JOSL, Bunkyo Ku, 1-5-45 Yushima, Tokyo 1138519, Japan
[3] Keio Univ, Sch Med, Dept Orthopaed Surg, Shinjuku Ku, 35 Shinanomachi, Tokyo 1608582, Japan
[4] Tokyo Med & Dent Univ, Dept Orthopaed Surg, Bunkyo Ku, 1-5-45 Yushima, Tokyo 1138519, Japan
[5] Chubu Rosai Hosp, Dept Orthopaed Surg, Minato Ku, 1-10-6 Komei, Nagoya, Aichi 4558530, Japan
[6] Niigata Univ, Med & Dent Gen Hosp, Dept Orthopaed Surg, Chuo Ku, 1-757 Asahimachidori, Niigata 9518510, Japan
[7] Tokai Univ, Sch Med, Dept Orthopaed Surg, Surg Sci, 143 Shimokasuya, Isehara, Kanagawa 2591193, Japan
[8] Wakayama Med Univ, Kihoku Hosp, Dept Orthopaed Surg, 219 Myoji,Katsuragi Cho, Wakayama 6497113, Japan
[9] Wakayama Med Univ, Dept Orthopaed Surg, 811-1 Kimiidera, Wakayama 6418509, Japan
[10] Jichi Med Univ, Dept Orthopaed Surg, 3311-1 Yakushiji, Shimotsuke, Tochigi 3290498, Japan
[11] Natl Hosp Org Okayama Med Ctr, Dept Orthopaed Surg, Kita Ward, 1711-1 Tamasu, Okayama 7011192, Japan
[12] Imakiire Gen Hosp, Dept Orthopaed Surg, 4-16 Shimotatsuocho, Kagoshima 8928502, Japan
[13] Hyogo Coll Med, Dept Orthoped Surg, 1-1 Mukogawacho, Nishinomiya, Hyogo 6638501, Japan
[14] Saiseikai Kawaguchi Gen Hosp, Dept Orthopaed Surg, 5 Chome 11-5 Nishikawaguchi, Kawaguchi, Saitama 3328558, Japan
[15] Hamamatsu Univ Sch Med, Dept Orthopaed Surg, Higashi Ward, 1 Chome 20-1 Handayama, Hamamatsu, Shizuoka 4328580, Japan
[16] Univ Yamanashi, Dept Orthopaed Surg, 1110 Shimokato, Chuo, Yamanashi 4093898, Japan
[17] Hirosaki Univ, Grad Sch Med, Dept Orthopaed Surg, 5 Zaifu Cho, Hirosaki, Aomori 0368562, Japan
[18] Univ Tokyo, Dept Orthopaed Surg, Bunkyo Ku, 7-3-1 Hongo, Tokyo 1138655, Japan
[19] Shiga Univ Med Sci, Dept Orthopaed Surg, Seta Tsukinowa Cho, Otsu, Shiga 5202192, Japan
[20] Tokyo Med Univ, Dept Orthopaed Surg, Shinjuku Ku, 6-1-1 Shinjuku, Tokyo 1608402, Japan
[21] Tokyo Med Ctr, Dept Orthopaed Surg, Meguro Ku, 2-5-1 Higashigaoka, Tokyo 1528902, Japan