Quantifying normal head form and craniofacial asymmetry of elementary school students in Taiwan

Background: Defining three-dimensional (3D) normal craniofacial morphology in healthy children could provide craniofacial surgeons a reference point to assess disease, plan surgical reconstruction, and evaluate treatment outcome. The purposes of this study were to report normal craniofacial form and quantify craniofacial asymmetry of healthy children in Taiwan by implementing the 3D stereophotogrammetry technique. Methods: Healthy Taiwanese elementary school children (n = 652) aged 6–12 years with no known craniofacial anomaly were recruited. After the 3dMD scanning procedure, 32 landmarks were manually placed on the 3D cranial images. Thin plate spline algorithm based on landmarks and closest point matching was applied to deform a symmetric 3D template into the scale of each scanned images. Skull asymmetry and facial asymmetry were calculated using 3dMD vultus and MATLAB. Average head shape models were also presented. Results: Overall, the mean head transverse width, height, anteroposterior length, and circumferences were 163.02, 220.79, 179.07, and 526.55 mm, respectively. On average, the skull asymmetry and facial asymmetry were 2.47 ± 1.26 mm and 0.96 ± 0.53 mm, respectively, with no significant (all p > 0.05) differences found when comparing males and females. In the average head shape model, certain craniofacial areas on the right side were found to be more protruded than those on the left side. Conclusions: This study shows that the baseline craniofacial form of the Taiwanese elementary school children is asymmetric with a tendency of more protrusion of the head on the right side.