Finite Element Analysis of Conventional and Patient-Specific Fixation Systems in Large Maxillary Repositioning

This study evaluated the biomechanical performance of 3 fixation systems-L-shaped miniplates, prebent plates, and a single-piece patient-specific plate (PSP)-for maxillary stabilization following Le Fort I osteotomy using finite element analysis. A three-dimensional finite element model of the maxilla was constructed from computed tomography data of a patient with maxillary deficiency. Simulated Le Fort I osteotomies included 5 mm maxillary advancement and 6 mm downgrafting, with iliac bone grafts placed between the segments. Fixation was achieved using 4 L-shaped miniplates, 2 prebent plates, or a single-piece PSP. Vertical (500 N) and oblique (250 N) masticatory loads were applied. Von Mises stress on plates and screws, maximum principal stress in bone and graft, and total segment displacement were assessed. The prebent plate model exhibited the highest von Mises stress on fixation plates under vertical loading (135.596 MPa). The single-piece PSP demonstrated the lowest displacement values in all directions, indicating superior segmental stability. Although slightly higher screw (88.379 MPa) and bone stress (14.835 MPa) values were observed in the PSP model, all stresses remained below physiological and material safety thresholds. Graft stress values were comparable to those of surrounding bone under both oblique (6.229-6.621 MPa) and vertical loading (8.385-9.127 MPa). All fixation systems provided adequate mechanical performance; however, the single-piece PSP showed more favorable stress distribution and stability, supporting its use as a biomechanically advantageous fixation option in orthognathic surgery.