Background: Within the spine, mobility and stability are principles that drive anatomic morphology. Based on radiographic measurements, the orientation of cervical facet joints has been proven to change throughout child growth. However, because of the mainly cartilaginous composition of the vertebrae in the young child, the lack of osseous landmarks makes radiograph-based measurements unreliable. The aims of our study were to evaluate the change in the sagittal orientation of the cervical facet joints with age based on magnetic resonance imaging (MRI) of asymptomatic children and to compare it to the changes in vertebral body dimensions.
Methods: Sagittal images passing through the center of the facet joint or through the center of the vertebral body were used to assess facet orientation at every cervical level. Anteroposterior facet orientation was defined as the angle between the superior facet and a line perpendicular to the posterior wall of the vertebral body. Vertical was defined as parallel to the posterior wall; horizontal was defined as perpendicular to the posterior wall. Vertebral body height and anteroposterior diameter were measured as well.
Results: MRI data of the normal cervical spine of 90 children who were 2 months to 18 years of age, obtained for neurologic evaluation, were used for this study. For each level from C3 to C7, there was a positive correlation between facet orientation and age (R = 0.498, p < 0.001). The facet joints were the most vertical at C3 (43.9°) and C7 (49.6°), whereas C5 had the most horizontal facets (39.4°). The greatest rate of change in facet orientation was observed between 6 and 9 years of age.
Conclusions: Our results demonstrate that facets become more vertical as a function of age. However, other parameters than age must be considered to explain the variation of facet orientation. At C3 and C7, the facet orientation was more vertical, which may increase stability. In between, C5 facets were shallower, which may increase mobility and flexion-extension range of motion.