Objectives: Spondylolisthesis is the forward displacement of a lumbar vertebra relative to the adjacent vertebra, occurs as result degeneration or surgery and is a special type of lumbar instability. There is no consensus about which radiologic modality or findings truly reflect the lumbar instability and the exact incidence after single level disk surgery is unknown.
Methods: In this prospective study, we have included 90 patients who were operated by the same surgeon with single level disk herniation. We aimed at evaluating the post-operative lumbar spondylolisthesis, with flexion and extension lateral radiographs in addition to standard magnetic resonance imaging (MRI).
Results: We have seen spondylolisthesis in six of 90 cases with standing lateral flexion-extension radiographs, which were undefinable with MRI. Pain intensity and functional-economic rating scale (Prolo scale) were unremarkable.
Discussion: We have concluded that standing flexion-extension radiographs should be routinely combined in patients with failed back surgery syndrome and even if lumbar instability is clinically suspected, especially when conventional MR examination is normal. When the MR examination showed spondylolisthesis, standing flexion-extension radiographs could not give additional information.