History of Research -- Epidemiology -- Overview of Epidemiology and Genetics -- OPLL: Disease Entity, Incidence, Literature Search, and Prognosis -- Genetic Susceptibility to OPLL -- Pathology and Pathogenesis -- Overview of Etiology and Pathogenesis -- Etiology and Pathogenesis -- Contribution of Metabolic Conditions to Ossification of the Posterior Longitudinal Ligament of the Spine -- Review of Histopathological Studies on OPLL of the Cervical Spine, with Insights into the Mechanism -- Pathology of Ossification of the Ligamentum Flavum -- Possible Roles of Bone Morphogenetic Proteins and Transforming Growth Factor-?s in the Pathogenesis of OPLL and OLF -- Pathology of Spinal Cord Lesions Caused by Ossification of the Posterior Longitudinal Ligament -- Tiptoe Walking (ttw) Mouse -- Study of Ligament Ossification and Abnormal Glucose Tolerance in the Zucker Fatty Rat -- Experimental Murine Model of Ossification of Spinal Ligaments Induced by Bone Morphogenetic Protein-2 -- Spinal Cord Lesions in Spinal Hyperostotic Mouse (twy/twy) Simulating Ossification of the Posterior Longitudinal Ligament of the Cervical Spine -- Diagnosis of OPLL and OYL -- Diagnosis of OPLL and OYL: Overview -- Clinical Manifestation of Cervical OPLL -- Clinical Manifestations of Thoracic OPLL and OLF -- Diagnostic Imaging of Cervical Ossification of the Posterior Longitudinal Ligament -- Imaging Diagnosis of Thoracic OPLL and OLF -- Electrophysiological Diagnosis of Cervical OPLL Myelopathy -- Treatment of OPLL and OLF -- Overview of Treatment for Ossification of the Longitudinal Ligament and the Ligamentum Flavum -- Pharmacotherapy for Ossification of the Spinal Ligaments: Clinical Trial of Disodium (1-Hydroxyethylidene) Diphosphonate to Inhibit Progression of Ossification of the Posterior Longitudinal Ligament in the Cervical Spine after Posterior Decompression Surgery -- Conservative Treatment of Ossification of the Posterior Longitudinal Ligament in the Cervical Spine -- Choice of Surgical Procedure -- Expansive Laminoplasty -- Expansive Open-door Laminoplasty for Ossification of the Posterior Longitudinal Ligament of the Cervical Spine: Surgical Indications, Technique, and Outcomes -- Double-door Laminoplasty by Splitting Spinous Processes -- Anterior Cervical Decompression for Cervical Myelopathy Caused by Ossification of the Posterior Longitudinal Ligament -- Treatment of OPLL and OLF of the Cervical Spine: Long-Term Results -- Choice of Surgical Procedures for Thoracic Ossification of the Posterior Longitudinal Ligament -- Anterior Decompression and Fusion for Ossification of the Posterior Longitudinal Ligament of the Thoracic Spine: Procedure and Clinical Outcomes of Transthoracic and Transsternal Approaches -- Circumspinal Decompression with Dekyphosis Stabilization for Thoracic Myelopathy due to Ossification of the Posterior Longitudinal Ligament -- Posterior Extensive Cervicothoracic Laminoplasty -- Anterior Decompression Through Posterior Approach for Thoracic Myelopathy Caused by OPLL: Ohtsuka Procedure -- Surgical Treatment for Ossification of the Posterior Longitudinal Ligament of the Thoracic Spine: Outcomes of One-Stage Posterior Decompression with Corrective Fusion Surgery -- Surgery for Ossification of the Ligamentum Flavum -- Computer-Aided Surgery for Ossification of the Spinal Ligaments -- Surgical Treatment of Thoracic Ossification of the Posterior Longitudinal Ligament: Intraoperative Spinal Cord Monitoring -- Intraoperative Ultrasonography for Patients with Ossification of the Posterior Longitudinal Ligament.