Ossification of the Posterior Longitudinal Ligament of the Cervical Spine Etiology and Natural History

Study Design. Review article. Objective. To review the etiology, natural history, measurement tools, and image diagnosis of ossification of the posterior longitudinal ligament (OPLL) of the cervical spine. Summary of Background Data. OPLL is a well-known disease that causes myelopathy. Genetic factors are very important for development of OPLL. However, the pathogenetic gene and natural history of OPLL have not been clarified. Methods. The authors reviewed studies about the etiology, natural history, measurement tools, and diagnosis of OPLL, which had been performed by the members of the Investigation Committee on the Ossification of the Spinal Ligaments of the Japanese Ministry of Health, Labour, and Welfare. Results. The prevalence of OPLL in the general Japanese population was reported to be 1.9% to 4.3% among people older than 30 years. Genetic factors are important for development of OPLL, and some candidate genes have been reported. Clinical course of OPLL has been clarified by a prospective long-term follow-up study. Some radiographic predictors for development of myelopathy were introduced. Image diagnosis of OPLL is easy by plain radiographs, but magnetic resonance imaging and computed tomography are useful to determine cord compression by OPLL. Conclusion. OPLL should be managed on the basis of the consideration of its natural history. Elucidation of pathogenetic genes of OPLL will introduce a new approach for management of OPLL.