Definition of topographic organization of skull profile in normal population and its implications on the role of sutures in skull morphology

The geometric configuration of the skull is complex and unique to each individual. This study provides a new technique to define the outline of skull profile and attempt to find the common factors defining the ultimate skull configuration in adult population. Ninety-three lateral skull x-ray from the computed tomographic scan films were selected and digitized. The lateral skull surface was divided into 3 regions based on the presumed location of the coronal and lambdoid sutures. Three main curvatures (frontal, parietal, occipital) were consistently identified to overlap the skull periphery. The radius, cord length, and inclination of each curvature were measured. The average values for 3 defined curvatures of the skull profile were recorded. Factor analysis of the measured values produced 3 factors explaining the skull profile. The first factor explained 32% of total variance and was related to the overall size of the head as represented by total length and the radius of the curvature in the vertex and back of the head. The second factor covered 26% of the variance representing the inverse correlation between the angle of the frontal and parietal curves. The third factor revealed the direct correlation of the occipital and parietal angle. In all of these factors, the frontal zone variation was independent or opposite of the parieto-occipital zone. A strong association between the total length of the skull, occipital curve radius, and length with the sex was shown. In conclusion, the skull profile topography has large variation and can be defined mathematically by 2 distinct territories: frontal and parieto-occipital zones. These territories hinge on the coronal suture. Therefore, the coronal suture may play a dominant role in final skull configuration.