The influence of facet joint orientation in the lumbar spine segment on the intervertebral disc bulge.

Purpose: Due to the growing percentage of degenerative spinal diseases among the population, it is extremely important to assess how the orientation of the articular facets affects the changes in the intervertebral disc. Therefore, the aim of this study was to assess the effect of the orientation of the articular facets on the changes occurring in individual layers of the annulus fibrosus of the intervertebral disc under the influence of the load causing extension.

Methods: Numerical simulations were performed for five configurations of the functional spinal units: physiological, with moderate tropism, severe tropism, and segments in which non-physiological orientation was modelled of both processes with different ranges.

Results: It can be concluded that severe tropism causes more significant changes in intervertebral disc bulging on the physiological side of the orientation of the articular facets. Furthermore, the value of stress on articular processes increases tenfold on the side of severe tropism compared to the physiological facet joint orientation.

Conclusion: Facet joint orientation plays an important role in the transfer of loads by the spine and the posterior column provides important support for the spine during extension.