A Biomechanical Study on the Effect of Premature Fusion of the Frontosphenoidal Suture on Orbit Asymmetry in Unilateral Coronal Synostosis

Objective The coronal ring of patients with unilateral coronal synostosis (UCS) presents premature fusion. This study aims to elucidate whether or not the dynamic behavior of the orbit in response to intracranial pressure (ICP) differs between patients in whom the premature fusion exists only in the frontoparietal suture (FPS) and those in whom the premature fusion extends to the frontosphenoidal suture (FSS). Methods A total of 15 UCS patients were included in the present study. Patients in whom premature fusion was seen inside the FPS and those in whom premature fusion extended to the FSS were categorized as FP Only (4.2 ± 1.4 m/o) and FP + FS groups (4.6 ± 2.2 m/o), respectively. On the basis of computed tomography (CT) data, computer-aided design models were produced. Pressure of 15 mm Hg was applied to the neurocranium of each skull model to simulate ICP. Using the finite element method, the displacements presented by each model's orbits were calculated. Displacements of the two groups were compared. Results The orbit demonstrated greater displacement in the FP Only group than in the FP + FS group, suggesting that premature closure of the FSS disturbs growth of the orbit in response to ICP. Conclusion In performing surgical treatment for UCS, the degree of fusion that the FSS presents should be evaluated carefully. In cases in which the FSS presents premature fusion, it is recommended to release the fusion at an early stage of cranial growth to improve the appearance of the orbital region.