To analyze and compare the morphological differences between the unaffected mandibles of the hemifacial microsomia (HFM) patients and the normal children′s mandibles with a geometric morphometric method.

The three-dimensional CT data of 16 HFM patients were collected. The patients were under one year old when admitted to Guangzhou Women and Children′s Medical Center from January 1, 2015 to December 31, 2021, and categorized as type Ⅱ b and type Ⅲ. Normal mandible data of children with the same age were used as the control. Three-dimensional superimposition of CT data was performed, and the unaffected mandible projections on the horizontal and sagittal planes were drawn for geometric morphometric analysis.

Three-dimensional superimposition indicated that the condyles of the unaffected mandibles deviated inward, with inclined posteriorly ramus, slightly abducted body and slightly forward protruded chin. There were significant differences between the patients and the control group in both horizontal (Mahalanobis distance = 6.472 9, P<0.001, Procrustes distance = 0.047 7, P=0.026 2) and sagittal projections (Mahalanobis distance = 6.422 7, P<0.001, Procrustes distance = 0.059 6, P=0.000 6) . The horizontal projection showed that the chin of the patient group deviated to the opposite side, whereas the area between the chin and body was more curved, and the horizonal axis of the condyle rotated outward relative to the body. The sagittal projection showed that the body-ramus curvature of the patient group reduced, and the condyle shortened along the long axis.

The unaffected side of HFM patients′ mandible was statistically different from that of the normal children. Alterations in the mandibles included chin elongation, increased horizontal curvature of the area between the chin and body, decreased sagittal curvature of the body-ramus, rotation of the condylar transverse axis outwardly relative to the body, and shortened condyle along the long axis.