Prevalence, Concomitance, and Distribution of Ossification of the Spinal Ligaments

Study Design. Cross-sectional study. Objective. To investigate the prevalence, concomitance, and distribution of various types of ossification of the spinal ligaments in healthy subjects using computed tomography (CT). Summary of Background Data. CT has better diagnostic accuracy for ossification of the spinal ligaments compared to plain radiography. Currently there is no study that examines the prevalence of ossification of the spinal ligaments using whole spine CT scans. Methods. One thousand five hundred Japanese patients (888 men and 612 women) who underwent positron emission tomography and CT (PETCT) in a private health check center between 2006 and 2013 were included. This PETCT was performed on self-paying participants as a preventive cancer screen. Existence of ossification of the posterior longitudinal ligament (OPLL), ligamentum flavum (OLF), anterior longitudinal ligament (OALL), diffuse idiopathic skeletal hyperostosis (DISH), and nuchal ligament (ONL) was examined. Results. The prevalence of spinal ligament ossifications was found to be 6.3% in cervical OPLL (8.3% in men and 3.4% in women), 23% in ONL (33% in men and 8.8% in women), 1.6% in thoracic OPLL (1.4% in men and 2.0% in women), 12% in thoracic OLF (15% in men and 7.7% in women), 37% in thoracolumbar OALL (45% in men and 26% in women), and 12% in DISH (16% in men and 6.2% in women). Thirteen percent of patients with cervical OPLL had thoracic OPLL, 34% of cervical OPLL had thoracic OLF, 45% of cervical OPLL had ONL, and 36% of cervical OPLL had DISH. The most common level was C5 for cervical OPLL, T1/2 for thoracic OPLL, T11 for thoracic OLF, and T8/9 for OALL. Conclusion. Accurate prevalence of various types of ossification of the spinal ligaments evaluated by CT was revealed. High concomitance was observed in each classification of spinal ligament ossification. Level of Evidence: 3