Three-dimensional fetal cephalometry.

Craniofacial growth has been the subject of numerous studies in which different techniques have been elaborated aiming to model this dynamic phenomenon in a rational manner. One of the methods employed is cephalometric analysis applied to the fetus. Generally, however, these studies are confined to the exploration of a single spatial plane (sagittal plane), whose orientation is never defined in a rigorous and perfectly reproducible manner. Thus, none of these analyses offers a formal growth model. This has led us to propose a new method of fetal cephalometric study taking into account criteria for proper reproducible analysis: spatial exploration of the head performed through three-dimensional tomodensitometric images and precise location of landmarks and reproducibility of the orientation of each image, which is assured by reference to the vestibular orientation (based on the external semicircular canals), as has been described by Girard and Perez and further developed by Fenart. When the labyrinth is developed, this orientation does not change during the growth stages of the head, even with craniofacial deformities. This permits application of this orientation on fetuses and the superposition of images of different subjects. The methodology is presented using two normal human fetuses, and the advantages of this computerized tool are discussed.