Human craniofacial sphericity: A simultaneous analysis of frontal and lateral cephalograms of a Japanese population using geometric morphometrics and partial least squares analysis

Abstract

Objectives The aim of this paper was to test Enlows morphological predictions of the “balloon model” of cranial head form patterns. This model predicts specific suites of morphological features in relation to basicranial flexure and skull globularity. Design 2D geometric morphometrics and partial least squares analysis (PLS) were used for simultaneous analysis of lateral and frontal X-rays of 41 adult males and females of a Japanese population with geometric morphometrics and partial least squares analysis. Results Reduction of the relative distance between basion and the posterior face, either because of basicranial flexure or overall basicranial re-orientation, was significantly related to increase of relative upper facial and dental arcade widths and a forward shift of the mandibular symphysis. These changes were unrelated to facial variations in height. Conclusions In this population some aspects of Enlow's balloon model are supported while others should be modified, which challenges the balloon model of overall integration and cranial sphericity. This study suggests that variation in the posterior part of the cranium including the petrosals is unrelated to variation in facial and anterior basicranial regions. Partial least squares analysis is a useful tool for investigating craniofacial problems that require combining different X-ray views of the same individuals.