Least useful for diagnosing spondylolisthesis

D i.e. X ray spine AP view Spondylolisthesis is a forward slip of one veebrae upon another; so it is best viewed (or seen earliest) in sagittal images of spine i.e. lateral and oblique X rays of spine and saggital & axial views of CT & MRIQ. AP views of X ray can only be used to demonstrate indirect evidences (eg. inveed Napoleon's hat sign) of late/ severe spondylolisthesis. Oblique view of spine display the lamina and aicular processes more clearly than the classical anteroposterior & lateral views. The shadow of neural arch resembles that of Scottish terrier dogQ. Spondylothesis is forward slip of one veebrae upon another. Majority of cases are due to stress fracture of pars interaicularis leading to broken neck or presence of collar on the Scottie doe. More displacement will lead to Beheaded (without head) Scottie terrier sign(2. Spondylolisthesis : ventral slipping or gliding of all or pa of one veebrae on a stationary veebra beneath it. Most common is between L5 - S1 and between L4 -- L5. "Inveed Napoleon's HatQ" sign: A severe degree of spondylolisthesis at L5 - Si can be identified on A-P view by ventrocaudal displacement of L5 over sacrum and creates curvilinear densities.