Facet Tropism is an asymmetry of the zygapophyseal joints and has been long thought to be related to intervertebral disc degeneration and back pain.
In a research article in The European Spine Journal, Wang et al. looked at how the degree of angle difference between the facets relates to disc bulge and back pain.
(Tropism comes from the Greek root (trope) which means to turn. In the embryological development of the vertebrae, some facets turn more than others and then in turn can have an affect on the overall biomechanics of the spine.)
In the research article (FULL TEXT) titled: “The relationship between degree of facet tropism and amount of dynamic disc bulge in lumbar spine of patients symptomatic for low back pain” , these researchers used Dynamic MRI to evaluate disc bulge and tropism by categorizing tropism into three distinct categories.
- less than 6 degree difference = no tropism
- 6-11 degree difference = mild tropism
- greater than 11 degree difference = severe tropism
What they found was that severe facet tropism was associated with disc bulge in only a subset of older patients.
Dynamic Disc Designs is a spine modeling company that highlights important research topics like facet tropism, and develops models that showcase natural anatomical details. Many of our models demonstrate facet tropism because they include real human variations.