Is There a Relation Between High Pelvic Incidence and Sagittal Angle of Posterior Lumbar Facets?

In recent years, several studies have shown the presence of a linear correlation between the pelvic incidence (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 computed tomography (CT) scans were collected. Inclusion criteria included age less than 40 years 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 (SMAIO, Lyon, France), and the facet sagittal angle were evaluated on axial CT images from L1-L2 to L5-S1 using the institution PACS system (GE Centricity, Chicago, IL).

A total of 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 (odds ratio = 2.3). The effect of sex on sagittal angle of facet joints was found to be non-significant compared with 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 sex. It carries the heaviest load in the progression towards sagittally oriented facet joints, which might lead to segmental instability and eventual spinal pathologies.