Introduction:
In this retrospective study, we aimed to investigate the possible effects of transitional vertebra anatomy on facet joint tropism and orientation by evaluating lumbar magnetic resonance imaging (MRI) studies performed at our institution.

Material and methods:
We included 84 patients with sacralization of the L5 vertebra and an equal number of patients with a radiology report within normal limits as the control group in our study. We compared facet tropism (FT) and orientation between both groups.

Results:
In both the sacralization group and the control group, the facet orientation angle showed a significant increasing trend from the L1-L2 level to the L5-S1 level (p < 0.001). The orientation angle of the L5-S1 level was higher in the sacralization group compared to the control group (p < 0.01). In the evaluation of FJ orientation between the sacralization and control groups, we found that coronal orientation was significantly more frequent at the L5-S1 level in the sacralization group. When the 2 groups were compared with regard to tropism at each spinal level, the sacralization group had a significantly higher FT frequency at the L5-S1 level (p < 0.001).

Conclusions:
To our knowledge, this is the first study to evaluate the relationship between sacralization and facet joint tropism. However, there were no relationships between facet degeneration, disc degeneration/herniation, and sacralization. Our results indicate that, although patients with sacralization and controls had similar characteristics in most assessments, they demonstrated significant differences at the L5-S1 level in terms of orientation and tropism.