Fifty years ago, Forestier and Rotés-Querol published their fundamental paper on, what they called, senile ankylosing hyperostosis of the spine1—according to today's nomenclature, diffuse idiopathic skeletal hyperostosis (DISH).2 DISH is a systemic non-inflammatory disorder which might be classified as ossifying diathesis of entheses and ligaments. Ossification starts and extends from insertions of skeletal muscles, ligaments, and joint capsules. The most prominent features of DISH appear on the spine as flowing appositions of newly formed ectopic bone along the anterolateral aspect of the spine.

Ossification of the posterior longitudinal ligament of the spine (OPLL), on the other hand, involves the posterior aspect of vertebral bodies and discs, predominantly of the cervical spine.3Systematic studies of OPLL began in Japan 25 years ago. A varying proportion …