Presentation
Chronic low back pain
Patient Data
Age: 20 years
Gender: Female
From the case:
Inverted Napoleon hat sign
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Frontal magnification

These radiographs show the "inverted Napoleon hat sign" on the frontal view, indicative of bilateral L5 pars defects and spondylolisthesis.
From the case:
Inverted Napoleon hat sign
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Coronal MIP bone window

CT correlate of the radiographic images
Case Discussion
The "inverted Napoleon hat sign" is a finding on lumbar spine radiographs that indicates bilateral L5 pars defects with anterolisthesis of L5 over S1.