• Shunji Matsunaga, Kozo Nakamura, Atsushi Seichi, Toru Yokoyama, Satoshi Toh, Shoichi Ichimura, Kazuhiko Satomi, Kenji Endo, Kengo Yamamoto, Yoshiharu Kato, Tatsuo Ito, Yasuaki Tokuhashi, Kenzo Uchida, Hisatoshi Baba, Norio Kawahara, Katsuro Tomita, Yukihiro Matsuyama, Naoki Ishiguro, Motoki Iwasaki, Hideki Yoshikawa, Kazuo Yonenobu, Mamoru Kawakami, Munehito Yoshida, Shinsuke Inoue, Toshikazu Tani, Kazuo Kaneko, Toshihiko Taguchi, Takanori Imakiire, and Setsuro Komiya.
• Department of Orthopaedic Surgery, Imakiire General Hospital, Kagoshima, Japan. shunji@m.kufm.kaqgoshima-u.ac.jp
• Spine. 2008 Nov 15; 33 (24): 2648-50.

Study DesignA multicenter cohort study was performed retrospectively.ObjectiveTo identify radiographic predictors for the development of myelopathy in patients with ossification of the posterior longitudinal ligaments (OPLL).Summary Of Background DataThe pathomechanism of myelopathy in the OPLL remains unknown. Some patients with large OPLL have not exhibited myelopathy for a long periods of time. Predicting the course of future neurologic deterioration in asyptomatic patients with OPLL is difficult at their initial visit.MethodsA total of 156 OPLL patients from 16 spine institutes with an average of 10.3 years of follow-up were reviewed. Subjects underwent a plain roentgenogram, computed tomography (CT), and magnetic resonance imaging of the cervical spine during the follow-up. The trauma history of the cervical spine, maximum percentage of spinal canal stenosis in a plain roentgenogram and CT, range of motion of the cervical spine, and axial ossified pattern in magnetic resonance imaging or CT were reviewed in relation to the existence of myelopathy.ResultsAll 39 patients with greater than 60% spinal canal stenosis on the plain roentgenogram exhibited myelopathy. Of 117 patients with less than 60% spinal canal stenosis, 57 (49%) patients exhibited myelopathy. The range of motion of the cervical spine was significantly larger in patients with myelopathy than in those of without it. The axial ossified pattern could be classified into 2 types: a central type and a lateral deviated type. The incidence of myelopathy in patients with less than 60% spinal canal stenosis was significantly higher in the lateral deviated-type group than in the central-type group. Fifteen patients of 156 subjects developed trauma-induced myelopathy. Of the 15 patients, 13 had mixed-type OPLL and 2 had segmental-type OPLL.ConclusionStatic and dynamic factors were related to the development of myelopathy in OPLL.

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