Finite element analysis of the biomechanical behavior of three different fixation systems used for maxillary downward repositioning in Le Fort I osteotomy

Gündüz Can Gürlek, Finite Element Analysis of the Biomechanical Behavior of Three Different Fixation Systems Used for Maxillary Downward Repositioning in Le Fort I Osteotomy, Başkent University Institue of Health Sciences PhD Programme of Oral and Maxillofacial Surgery, PhD Thesis, 2025 Aim: The aim of this study was to evaluate, by finite element analysis, the biomechanical behavior of three different fixation types used for fixation of the maxilla following downward repositioning in Le Fort I osteotomy. Materials and Methods: This finite element analysis was conducted in collaboration with Başkent University and Tinus Technologies. A standard human skull model was created in a computer environment (Altair Evolve, USA), and three different fixation systems—single-piece plate, Lplate, and prebent plate—were modeled. An iliac bone graft was fixed between the bony segments, and the biomechanical evaluation was performed by finite element analysis. Results: In all three fixation systems, stresses in plates and screws, segment displacements, and compressive and tensile stresses around the iliac graft and the adjacent screws were measured. The single-piece plate system exhibited the lowest segment mobility, whereas the prebent plate system showed the highest. Likewise, Von Mises stresses in plates and screws were lowest in the single-piece plate fixation. The highest Pmax value in the cortical bone adjacent to the screws was observed in the prebent plate system and the lowest in the Lplate system; Pmin values were highest with the Lplate. Regarding graft stresses, the lowest Pmin values were found in the singlepiece plate system. 9 Conclusion: Among the three systems, the singlepiece plate demonstrated the lowest values for segment stability and screw and plate stresses. Although it produced the highest compressive stresses in the graft, these values did not reach levels known to induce bone resorption; nevertheless, caution is advised when using cortical bone grafts. Keywords: patient spesific plates; orthognatic surgery; relapse This study was approved by Baskent University Institutional Review Board and supported by Baskent University Research Found (Project no: D-KA22/19).