Anterior epidural fat as a diagnostic marker on magnetic resonance imaging for differentiating isthmic and degenerative lumbar spondylolisthesis: a retrospective study

STUDY DESIGN: Retrospective study. PURPOSE: To investigate the diagnostic utility of anterior epidural fat (EF) for distinguishing isthmic from degenerative lumbar spondylolisthesis. OVERVIEW OF LITERATURE: Isthmic and degenerative lumbar spondylolisthesis must be distinguished accurately for appropriate clinical decision making. However, magnetic resonance imaging (MRI) often fails to detect pars defects; thus, additional imaging markers are needed. METHODS: We retrospectively analyzed lumbar spondylolisthesis in 274 patients, of whom 129 had isthmic disease and 145 had degenerative disease. We assessed the presence and structure of anterior EF on midsagittal MRI, calculated diagnostic performance metrics, and used multivariable logistic regression to identify independent predictors of isthmic spondylolisthesis. RESULTS: Anterior EF was observed in 95.3% of isthmic cases and 28.3% of degenerative cases (p