Safe, simple, and valid position for obtaining flexion-extension radiographs to assess instability in patients with lumbar spondylolisthesis: one specific instruction can make a difference

In lumbar spondylolisthesis, conventional standing flexion-extension radiography can yield varying results depending on the patient's effort and cooperation. Previous research suggested that assisted flexion radiography provides larger flexion with a significantly greater change in lumbar lordosis (ΔLL) and increased sagittal translation (ST), posterior opening (PO), segmental angulation (SA), and instability detection rates. In this study, the authors aimed to identify a safe, simple, and valid position for obtaining functional radiographs to evaluate abnormal instability in lumbar spondylolisthesis.