"Flowing wax" appearance on anterior and posterior borders of veebrae with normal interveebral disc space occuring due to ligament calcification is seen in -

Radiological features of DISH (Diffuse Idiopathic skeletal hyperostosis) : Flowing calcification and ossification along the anterolateral aspect of veebral bodies. - Flowing wax appearance Preserved disc space. Absence of bony ankyosis of facet joints,absence of sacroiliac bony erosion,sclerosis or bony fusion.