Least helpful for the diagnosis of spondylolisthesis -: (A) AP x-ray of spine, (B) Lateral x-ray of spine, (C) MRI, (D) CT
Answer is A. All the given radiological investigations are used for spondylolisthesis. However, AP x-ray of spine is least helpful as in low grades of spondylolisthesis it may be normal.
On the other hand lateral x-ray, CT and MRI (sagittal view) diagnose even the mildest degree of spondylolisthesis.
It is worth noting that spondylolysis (not spondylolisthesis) may be missed on lateral x-ray and MRI. CT scanning is more sensitive in diagnosing spondylolysis.