The structural implications of a unilateral facial skeletal cleft: a three-dimensional finite element model approach.

Objective: For children born with a unilateral facial skeletal cleft, oral motor function is impaired and skeletal development and growth are asymmetrical with regard to the midsagittal plane. This study was designed to verify that a unilateral skeletal cleft and its dimensions (i.e., depth and width) affect the severity of the asymmetric stress and strain distribution within the maxilla.
Methods: A three-dimensional finite element model of a normal maxilla was developed from pediatric, subject-specific computerized tomography scan data. A clefting pattern then was introduced to simulate varying degrees of deformity in geometry, with the bone properties and boundary conditions held constant. The asymmetric index was introduced to quantify the asymmetrical stress and strain distribution within the maxilla with regard to the midsagittal plane.
Results: The unilateral skeletal cleft led to a nonuniform, asymmetric stress and strain distribution within the maxilla: intensified on the noncleft side and weakened on the cleft side. As the depth of the unilateral cleft increased, the stress and strain distribution became increasingly asymmetric as measured by the asymmetric index. In contrast, the width of the cleft had minimal effect on the asymmetrical stress and strain distribution.
Interpretation/conclusion: These results implied that a child born with a unilateral cleft would be expected to have an asymmetric skeletal development between the noncleft and the cleft sides as a consequence of an asymmetric functional loading pattern.