Structural comparison of hemifacial microsomia mandible in different age groups by three-dimensional skeletal unit analysis

Purpose: The goal of this study was to understand the three-dimensional (3D) structural characteristics of hemifacial microsomia (HFM) mandible in terms of skeletal units, especially to locate the underdeveloped skeletal regions for treatment. Another goal was to compare the HFM structure of different age groups to understand growth potential relevant to treatment scheduling. Materials and methods: We reconstructed 3D mandibles from computed tomographic images of French and Korean patients with HFM (N = 28; group II) and normal subjects (N = 27; group I). Each mandible was classified by Pruzansky's HFM types I, II and III, and by age group (child, adolescent, and adult). The mandible was divided into skeletal units, and geometrical representation by skeletal unit line was performed, including the condylar, body, coronoid, and angular units. Their length and angulations were measured and statistically analyzed. Results: The results showed that the affected condylar unit in type II HFM and the condylar/coronoid unit in type III were smaller in young age groups than were other units. The angulation between the skeletal units in type II, though not type III, tended toward normalcy with age, but not to the normal degree of angulations in group I. Conclusion: Our study shows the major involvement of condylar unit and minor involvement of body unit for HFM, improving with age in type II. The mandibular skeletal unit analysis seems to be a useful tool for individualized diagnosis, allowing identification of the major etiopathogenic area and treatment planning, including a simulation to set up a regimen for successful reconstruction of HFM.