Three-Dimensional Evaluation of Facial Asymmetry in Patients with Hemifacial Microsomia

We hypothesize that the three-dimensional asymmetry analysis as postulated by Katsumata et al will reveal more diagnostic information for individuals with HFM than traditional cephalometric analyses. We further hypothesize that there will be a direct relationship between mandibular asymmetry values and the corresponding Pruzansky-Kaban score. The objectives in this study are to: evaluate HFM in three-dimensions using an asymmetry index classification system, determine which mandibular segments are more affected, and compare this new classification approach to established descriptive classification systems. The experimental group consisted of 16 individuals with diagnosed HFM that had initial CBCT scans. Established cephalometric landmarks were indentified on the images and three-dimensional measurments were gathered. These measurments were then inserted into an equation to calculate the asymmetry index value for each landmark. Bilateral linear measurements of the mandibular body and ramus were compared. Finally, mandibular asymmetry values were compared to the corresponding Pruzansky-Kaban score. All skeletal landmarks were found to have significantly(p<0.05) larger asymmetry values when compared to unaffected controls. The mandibular body and ramus on the affected side were significantly(p<0.001) smaller than the unaffected side. A positive correlation(p=0.008) was found between the mandibular asymmetry value and Pruzansky-Kaban score. The study showed that individuals with HFM have asymmetry in the maxilla, mandibular body, and mandibular ramus. The study also introduced a new method for classifying HFM quantitatively.