Flowing wax appearance on anterior and posterior borders of vertebrae with normal intervertebral disc space occurring due to ligament calcification is seen in –

Diffuse idiopathic skeletal hyperostosis: DISH (hyperostotic spondylosis, Forestier's disease) is a multifocal entity of older people characterized by "flowing ossifications of the spine" involving four or more contiguous vertebrae and hyperostosis of some ligamentous attachments. The thick, flowing, florid, exuberant corticated plaques are extensive than that seen in degenerative changes producing so-called 'dripping candle wax or flowing candle wax' appearance.