Relationship between facial morphology and cervical vertebral shape: a radiographic investigation.

Aim: The aim of this study was to investigate the relationships between the characteristics of cervical vertebrae and craniofacial morphology using a global mathematical method.
Methods: Several cephalometric measurements and the outlines of the second (C2) and fourth (C4) cervical vertebrae were obtained from 45 head films (32 females aged 20-40 years; 13 males aged 21-37 years). Vertebral outlines were mathematically obtained by Fourier series, and the morphological distance between each outline and a reference one was computed. Linear correlations were run between cephalometric variables and morphological distances.
Results: Significant correlations (P<0.05) were found between anterior cranial base length (sella-nasion) and the morphological distance of C4 (subjects with a longer cranial base differ more from the reference vertebral outline), and between maxillary length and the morphological distance of C2 (subjects with a shorter maxilla differ more from the reference vertebral outline). The relationship between mandibular base length (Go-Me) and the morphological distance of C2 (subjects with a shorter mandible differ more from the reference vertebral outline) was nearly significant. Within each subject, the two analyzed vertebrae had independent relationships with the reference outlines.
Conclusion: A significant but limited relationship between craniofacial structures and vertebral morphology was found: at the best, 10% of the differences between the individual vertebral morphology and the reference one may be explained by craniofacial cephalometric measurements. The differences found between C2 and C4 morphologies may show a different effect of suboccipital muscles and of neck muscles within the theories of the functional matrix hypothesis.