The role of facet joint tropism and facet angle in disc degeneration.

In this study, the relationship between facet geometry (joint angle and tropism) and disc degeneration was analyzed. Magnetic resonance imaging and computed tomographic scans of 46 subjects less than 50 years of age were evaluated. Magnetic resonance imaging was used to determine disc degeneration, and computed tomography was used to measure facet joint angles and determine tropism. Subjects with tropism had a significantly higher prevalence of disc degeneration at all three lumbar levels examined (L3-4, L4-5, L5-S1). The average facet angles increased from L3-4 to L4-5 and further to the L5-S1 level. There was no statistically significant relationship between the magnitude of the angle and the presence of disc degeneration at any of the three levels. It was concluded that the risk of disc degeneration is increased in the presence of facet joint tropism.