Beheaded Scottish terrier sign is –

Oblique view of spine displays the lamina and articular processes more clearly than the classical anteroposterior & lateral views. The shadow of the neural arch resembles that of Scottish terrier dog. Spondylolysis          → Scotty dog wearing a collar sign. Spondylolisthesis     → (i) Beheaded Scotty dog sign;                                                 (ii) 'Inverted Napoleon's Hat' sign.