Abstract
BACKGROUND: Adjacent segment degeneration and/or disease is known to occur after a lumbar spinal fusion. It is a complex process encompassing multiple radiographic findings, including spondylolisthesis. Accurate characterization of the spondylolisthesis is important for the optimization of surgical treatment. OBSERVATIONS: A 56-year-old patient, whose medical history was significant for a posterior L4-S1 fusion performed about a decade earlier, presented with severe, refractory mechanical low back pain and lumbar radiculopathy for 1 year. Lumbar spine magnetic resonance imaging (MRI) revealed mild L3-4 spondylolisthesis. Standing radiographs of the lumbar spine revealed marked worsening of the spondylolisthesis on neutral views, without significant change on flexion or extension. However, there was no spondylolisthesis present on computed tomography (CT) of the lumbar spine that revealed chronic bilateral pars defects. Dynamic instability was noted by comparison of the sagittal alignment of recumbent MRI and CT versus standing radiography in the neutral position. The patient was taken to the operating room for surgical stabilization, with resolution of symptoms. LESSONS: Comparison of sagittal alignment between standing radiography and recumbent MRI and CT of the lumbar spine revealed dynamic instability of the lumbar spondylolisthesis that was not otherwise fully appreciated on dynamic standing radiographs of the lumbar spine with flexion and extension views alone. https://thejns.org/doi/10.3171/CASE24555.