Correlation Between Facet Tropism and Ossification of the Posterior Longitudinal Ligament in the Cervical Spine.

Study DesignRetrospective cohort study.ObjectivesTo explore the correlation between Facet Tropism (FT) and OPLL in cervical spine.MethodsOne-hundred patients with OPLL of cervical spine and one-hundred normal participants without OPLL or cervical disc herniation were included in this study, the patients were matched to the normal participants respectively based on the same sex and similar age (±5). For patients, the cervical levels with and without OPLL were categorized into "OPLL group" and "patient control group," respectively. Bilateral facet joint angles at C2/3-C6/7 were measured on sagittal, coronal, and axial planes on CT.ResultsOn every planes at the level of C2/3-C6/7,the mean difference between left and right facet angles and FT incidence in the most levels of the OPLL group were significantly greater than those in the control groups (P < 0.001). At the most cervical levels, there was no significant difference in mean difference of facet angles and FT incidence between the 2 control groups. On the axial plane, the incidence of FT in segmental type OPLL patients was significantly higher than that in continuous type OPLL patients (P = 0.036). On the coronal plane, the incidence of FT in segmental type OPLL was significantly higher than that in the other OPLL types (P < 0.001), and local type OPLL had a higher incidence of FT compared to mixed type OPLL (P = 0.016). On the sagittal plane, the incidence of FT in segmental type OPLL was higher than that in continuous type OPLL (P = 0.019) and mixed type OPLL (P = 0.036).ConclusionsThere is a significant correlation between OPLL of cervical spine and FT. There are significant differences in the incidence of FT among different cervical OPLL types.