Normative Measurements of L1-S1 Neuroforaminal Dimensions derived from Plain Film Radiography, Computed Tomography, and Magnetic Resonance Imaging

Abstract

Study Design. retrospective cohort Objective. To report normative measurements of L1-S1 lumbar neuroforamina on plain film radiography (PFR), computed tomography (CT), and magnetic resonance imaging (MRI), accounting for patient sex and ethnicity. Summary of Background Data. Quantitative criteria for diagnosis of neuroforaminal stenosis (NFS) remains unknown. Acquiring a thorough understanding of normative foraminal dimensions is a key step in formulating objective parameters for NFS. Methods. We measured 988 images from 494 patients between 18 and 35 years-old without spinal pathology who received PFR, CT, or MRI within one year of each other. Neuroforaminal measurements were defined as the height, area, and sagittal and axial widths. Statistical analyses were performed to assess relationships among PFR-, CT-, and MRI-derived neuroforaminal measurements as well as the influence of patient sex and ethnicity. Results. 330 PFR, 377 CT, and 281 MRI were measured. Of these, 213 PFR and CT, 117 PFR and MRI, and 164 MRI and CT intrapatient images were compared. Statistically significant differences were observed among PFR, CT, and MRI measurements across all levels L1-S1. PFR measurements were larger compared to those derived from CT and MRI. Weak-to-moderate correlations were observed between PFR and CT, PFR and MRI, and CT and MRI, with the magnitude of correlation decreasing caudally from L1-S1. Variations in neuroforaminal anatomy were observed based on sex and ethnicity. Conclusion. This study reports 25,951 measurements of normal L1-S1 neuroforaminal anatomy assessed by PFR, CT, and MRI. The values reported in this study may be used as normative reference measurements of the lumbar neuroforamina. PFR measurements of the neuroforamina are larger compared to those derived from CT and MRI across all levels from L1-S1. There is poor correlation among PFR, CT and MRI when measuring the lumbar neuroforamina. Differences in neuroforaminal anatomy are evident based on patient sex and ethnicity.