Longitudinal Changes in Facial and Basicranial Integration in the Mediolateral Axis

Steven F. Miller; Andrew Welling; Nathan E. Holton

doi:10.1096/fasebj.2018.32.1_supplement.639.2

Objectives Many studies over the past decade have employed morphological integration as a framework for understanding the interaction of the facial and basicranial skeleton in humans, the great apes, and our fossil lineage. Fewer studies, however, have examined morphological integration in the facial and basicranial portions of the skull in a true longitudinal sample. Most of these longitudinal studies have focused primarily on lateral cephalograms. While useful, these datasets only examine shape and morphological integration from the lateral aspect, limiting the types of questions that can be explored, primarily in the mediolateral axis. To rectify this gap in the data, we set out to study aspects of both symmetric and asymmetric shape variation in a longitudinal postero‐anterior (PA) celphalometric dataset in order to ascertain how patterns of morphological integration change in the mediolateral plane as a function of growth. Methods PA cephalograms from a total of 55 individuals from the longitudinal Iowa Facial Growth Study were digitized using 13 coordinate landmarks across the mandible, face, and cranial base to capture patterns of integration and modularity. This data was collected at three time points per patient: age 4, age 11, and in adulthood. Data were submitted to MorphoJ for a Two‐Block Partial Least Squares (2‐B PLS) analysis of both the symmetric and asymmetric shape components in order to examine morphological integration between the face and cranial base. Results 2‐B PLS results for the symmetric shape component show that integration between the face and cranial base decrease (becoming more modularized) from age 4 (RV=0.41, p<0.001), to age 11 (RV=0.25, p<0.001) before increasing again at the adult time point (RV=0.35, p<0.001). For the asymmetric component, however, levels of integration between the face and basicranium decrease consistently from age 4 (RV=0.59, p<0.001) to adult (RV=0.47, p<0.001). These results indicate that while levels of cranial integration tend to decrease throughout growth, this decrease is only consistent in the asymmetric shape component, potentially indicating that modularity of the face and cranial base has a strong mediolateral (side‐to‐side) component. Conclusion These results show that while overall trajectories of facial/cranial base integration show a similar trend toward modularity as individuals grow, this pattern of modularity is only a linear when examining the asymmetric shape component. This aspect of shape has been largely overlooked in the integration literature to date and warrants further study. This is from the Experimental Biology 2018 Meeting. There is no full text article associated with this published in The FASEB Journal.

Longitudinal Changes in Facial and Basicranial Integration in the Mediolateral Axis

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