Facet orientation and tropism: Associations with facet joint osteoarthritis and degeneratives

Study Design. Cross-sectional study. Objective. To evaluate the association between lumbar spine facet joint orientation, facet joint tropism, and facet joint osteoarthritis (OA) and degenerative spondylolisthesis (DS) identified by multidetector computed tomography in the community-based Framingham Heart Study. Summary of Background Data. The association between lumbar facet joint OA, DS, and facet orientation and tropism remains unclear. Methods. This study was an ancillary project to the Framingham Heart Study. A sample of 3529 participants of the Framingham Heart Study aged 40 to 80 underwent multidetector computed tomography imaging to assess aortic calcification. One hundred eighty-eight individuals were consecutively enrolled in this ancillary study to assess radiographic features associated with low back pain. Facet joint OA was evaluated at the L3-L4, L4-L5, and L5-S1 spinal levels, using a 4-grade scale. The association between facet joint OA, DS, and facet orientation, and tropism was examined using multiple logistic regression models adjusting for age, sex, and body mass index. Results. At each spinal level the facet joints with OA were more sagittally oriented than those without OA, but the difference was statistically significant only at L4-L5 spinal level (P = 0.0007). Facet tropism did not show an association with facet joint OA at any spinal level. Facet orientation was significantly associated with DS (0.89 [0.84-0.94]), however, facet tropism showed no association with DS. ConclusionS. The current study confirms a significant association between sagittal orientation and OA of the lumbar facet joints at L4-L5 and DS. Facet tropism was not associated with occurrence of facet joint OA or DS. Additional, longitudinal studies are needed to understand the causal relationship between facet joint morphology and OA.