Fibula reconstruction and small titanium plate fixation for repair of mandibular body defects：a three-dimensional finite element analysis / 中国组织工程研究

ABSTRACT

BACKGROUND: In clinic,the mechanical study about fibula reconstruction for the repair of mandibular bone defect is unrealistic; the finite element analysis, however, provides a new approach for the biomechanical study of mandibular reconstruction. OBJECTIVE: To establish the three-dimensional finite element model of mandibular body defect under fibula reconstruction and smal titanium plate fixation, and to analyze the biomechanical features. METHODS:The three-dimensional model of mandibular body defect under fibula reconstruction and internal fixation was established. 100 N bite force was loaded on the anterior teeth, contralateral first molar and contralateral second molar, respectively. The maximum stress and maximum displacement before and after model reconstruction, the stress of bone tissues around the titanium plate and titanium screw holes under anterior and posterior loading, and the maximum displacement of the front and rear ends of the fibula under anterior and posterior loading were observed. RESULTS AND CONCLUSION:The maximum stress of the normal mandible concentrated in the condylar neck. In the reconstructed models, the maximum stress concentrated in the contralateral condylar neck. Under the same bite force, the maximum stress value of the reconstructed mandibular model was greater than that of the normal mandible. The maximum stress value of the anterior teeth was greater than that of the posterior teeth. The stress value was maximal between two screw holes inside each titanium plate and almost concentrated in the mandibular angle. The maximum stress of the residual titanium screw of the mandible concentrated in the first titanium screw over the mandibular defect under loading, while the maximum stress of the titanium screw of the fibular end concentrated in the titanium screw below the mesial segment of the fibula. The cortical bone around the screw holes located at the residual end of the mandible near the defect area and the upper plate of the mesial segment of the fibula was the maximum stress concentrated site, and the maximum stress of anterior tooth loading was greater than that of the posterior tooth loading. The displacement values of the fibula gradualy reduced from the upper edge to the lower edge in the X-axis, from the anterior and posterior ends to the middle part in the Y-axis, as wel as from the anterior end to the posterior end in the Z-axis. The maximum displacement values of the anterior and posterior ends of the fibula were at the Z-axis and Y-axis, respectively. The maximum displacement value under anterior tooth loading was greater than that under posterior tooth loading. These results show that the titanium plate over the mandibular angle that is most easy to break should be reinforced. If the stress of titanium screw tip and neck is relatively large, double cortical titanium screw is preferred; if the stress of titanium screw and titanium plate at the fibula end and residual end of the mandible is relatively large, we should pay attention to their stability and fixation; if the stress of anterior tooth occlusion is greater than that of posterior tooth occlusion, anterior tooth occlusion should be avoided after repair.