OPLL: Disease Entity, Prevalence, Literature Research, and Growth

Abstract

Ossification of the spinal ligament is an ectopic bone formation of the spine. This hyperostotic condition was recognized by rheumatologists or radiologists in the nineteenth century. After a report of an autopsy case in 1960, ossification of the posterior longitudinal ligament (OPLL) became to be known as one of the causes of myelopathy. A pathological characteristic of OPLL is endochondral and intramembranous ossification despite mild disc degeneration. Radiographically, cervical OPLL was found from 1.9 to 6.3% in Japanese. Similarly, the prevalence of cervical OPLL was approximately 5% in Korean or Asian Americans. In Caucasian Americans, the prevalence of cervical OPLL was 1.3%. Various types of spinal ossification coexist in patients with hyperostosis. Thirty six percent of the patients with cervical OPLL had diffuse idiopathic skeletal hyperostosis (DISH). In Japanese, the prevalence was from 1.6 to 1.9% for thoracic OPLL, 12% for thoracolumbar DISH, and 23% for ossification of the nuchal ligament.