In recent years, several studies have shown the presence of a linear correlation between the PI and spondylolisthesis . However, no study has attempted to investigate a potential association between facet sagittal angle and spinopelvic parameters, especially PI in the normal population. Abdominopelvic CT scans were collected. Inclusion criteria included age less than 40 and CT done for non-orthopedic diagnostic purposes. All cases with any spinal pathology were excluded. Spinopelvic and lumbar spinal parameters were collected using the KEOPS software, while the facet sagittal angle were evaluated on axial CT images from L1-L2 to L5-S1 using the institution PACS system. 450 patients' imaging were analyzed, with a mean age of 31.3 years (±4.9). Facet sagittal angle was found to be significantly correlated to an increase in PI but only at the L5-S1 level (OR = 2.3). The effect of gender on sagittal angle of facet joints was found to be non-significant compared to high PI. Finally, at the L5-S1 level, facet tropism was associated with a higher PI but was not found to play a direct role in the angle of facet joints. The PI seems to be correlated to the other spondylolisthesis risk factors: facet tropism and female gender. It carries the heaviest load in the progression towards sagittally oriented facet joints, which might lead to segmental instability and eventual spinal pathologies.
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