Two-step cluster analysis based on three-dimensional CT measurements of craniofacial structures in severe craniofacial microsomia.

Background: The Pruzansky-Kaban and OMENS classifications do not provide additional details on temporomandibular joint deformities. The aim of this study was to classify and quantitatively define severe forms of craniofacial microsomia based on three-dimensional maxillofacial measurements, focusing on deformities in the zygomatic, temporal, and mandibular bones.

Methods: Maxillofacial computed tomography (CT) scans of children with severe types of craniofacial microsomia (CFM) from 2010 to 2020 were collected. Three-dimensional measurements of zygomatic arch length, height of mandibular ramus, height of maxilla, and occlusal cant were performed. A two-step cluster analysis was conducted based on zygomatic arch continuity, occlusal cant, and the ratio of the affected side to the unaffected side (A/U ratio) for zygomatic arch length, mandibular ramus height, and maxillary height.

Results: Fifty patients (32 male, 18 female) were included in the study. They were classified into 2 clusters through cluster analysis. Cluster 1 comprised subjects (44% of patients) with continuous zygomatic arches. Cluster 2 comprised subjects (39% of patients) with discontinuous zygomatic arches. The zygomatic arch A/U ratio in cluster 1 was greater than that in cluster 2, with statistical significance observed. Additionally, the maxilla height A/U ratio in cluster 1 was lower than in cluster 2, also with statistical significance. There was no statistically significant difference observed in the ramus height A/U ratio and occlusal cant between clusters 1 and 2.

Conclusions: Based on craniofacial measurements, severe CFM can be categorized into two types: continuous zygomatic arch and discontinuous zygomatic arch. This cluster analysis complemented the OMENS classification and could assist in the selection and design of prosthetic joints for patients with CFM.