Evaluation of failure of a titanium conventional plate in mandibular reconstruction and improve the performance with fibula free flap

Abstract

Maxillofacial extensive defects are caused by various factors such as tumor, osteomyelitis and trauma. Reconstruction of such injuries become a major challenge for maxillofacial surgeons. Clinical experiments indicate that one of the serious problems associated with conventional plate systems is the frequent incidence of complications such as screw loosening, plate exposure and plate fractures. To improve the performance of reconstruction system with new procedure. A 42-year-old male patient suffering from Ameloblastoma tumor in the lateral large defect was selected as case study. Initially, after cutting the cancerous tissue, a titanium conventional plate (TCP) model had been utilized as mandibular reconstruction system which failed due to plate exposure. Patient's CT-scan images were prepared, and geometry and shape of the plate were evaluated using Computer-Aided Design & Computer-Aided Manufacturing (CAD/CAM) and Additive Manufacturing (AM) technology. Then, its effect on the biomechanical performance of the failed system TCP model was investigated by finite element method (FEM). Fibula Free Flap FFF model as alternative and improved reconstruction system was selected. FEM evaluation of two models showed inevitable results which tip the scales in the favor of FFF model. The maximum Von-Mises stress had been exerted at the interface between screw-cortical bone. In TCP model, the peak value of Von-Mises stress exerted at the interface between screw-bone was 110 MPa, which exceeded the yield strength of the cortical bone, while, this factor fell to 68 MPa in FFF model. Furthermore, comparison with TCP model, the sensitivity of the plates and screws to the chewing load variations in FFF model decreased 20%. The results showed that the FFF model was more stable and flexible than the TCP model.