Morphological survey of the cervicothoracic junctional region

Vertebral morphology of the cervicothoracic junctional region was studied using the C6 to T4 vertebrae from 51 disarticulated skeletons (26 males and 25 females). Orientation of the facet joint pair relative to the plane of the superior endplate and the sagittal reference was recorded. A vertebral index was developed to compare the superior endplate surface area with the posterior vertebral body height. Vertebral morphometry was recorded for comparison with the limited published data for this region. The disc-facet angle was measured using a zygapophysial endplate protractor and the facet angle recorded from computer-aided digitizing of photographs of each segment. Vertebral dimensions were measured using Mitutoyo digital calipers. A marked change in disc-facet angle from C6 to T1 was recorded, with the incidence of right versus left asymmetry highest at the T1 level. The incidence of facet angle asymmetry greater than 10 degrees was 24% at C6, 18% at C7, and 16% at T1. The vertebral index indicated no significant gender difference. Consistent with other junctional regions of the spine, the cervicothoracic transition has significant morphological variations.