The evaluation of maxillary advancement technique using internal distraction osteogenesis in unilateral cleft lip and palate patient with finite element analysis

The aim of this study is to evaluate the parameters that commonly used in mechanical analysis of materials like displacement, strain and von Misses stress distributions after maxillary advancement in unilateral cleft lip and palate (UCLP) patients using distraction osteogenesis. The 3D skull model of a 20-year-old UCLP patient with normal mandibular development (SNB: 79.5o ) and maxillary hypoplasia (SNA: 70.7°) with negative overjet was reconstructed by using the computed tomography (CT) data. The surface mesh of the model was prepared by using the MIMICS software, and then the model was transferred into ANSYS (FE package). 854023 nodes and 623177 elements (Solid92) were used during the analysis. To obtain more realistic model, the maxillary cortical bone was defined as anisotropic. On the other hand the material properties of trabecular bone and callus were selected as linear, isotropic and homogenous. After a LeFort I osteotomy was performed on the model, the maxillary advancement was simulated in 6 steps with 1 mm translation in each step with a total of 6 mm displacement. Non-linear finite element analysis was used due to large deformations. Compared to the similar studies, more elements and nodes were defined especially in maxilla and zygoma. Selection of material properties of maxillary cortical bone has an important role on the calculation of bone strain and deformations during the finite element analysis (FEA). Therefore, the maxillary cortical bone was defined as anisotropic. Asymmetrical displacements and von Misses stresses were found in both right and left half-jaw. The maximum stresses were obtained at foramen infraorbitale and infraorbital margin regions at non-cleft side (mean 350 and 410 MPa, respectively). Relatively high von Misses stresses were found on sutura naso-maksillaris, fronto-nasalis, and zygomaticomaksillaris. Sagittal displacements of anterior nasal spina and point A were found to be 6.24 and 6.65 mm, respectively. The difference in the displacements was due to the asymmetrical anatomical structure in CLP patients. In this study the finite element method has been used to simulate the sagittal maxillary advancement. The simulation results obtained from numerical method show that asymmetrical stresses and displacements in the sagittal plane in UCLP patients reveal the difference in routine patients. Non-invasive methods such as the FEA help us to determine the mechanical response of the skull before any treatment is applied to