Biomechanics Of Rigid Internal Fixation In Simple Displaced Fracture Of Zygoma Through3D FEM Simulation

Objective:This study was designed to observe the stress distribution of the simple displaced fracture of zygoma under different rigid internal fixation(RIF)methods by developing a three-dimensional finite-element method(3D FEM).Methods:1.To establish the zygoma and the fixed-system3D finite element model: Choose a healthy adults as the research object.CT scan technology, the finite element software Mimics and UGNX6.0were used to establish the human zygoma and the fixed-system3D finite element models. Based on this model, the RIF models on the fracture model was established in three different ways.2.Stress and deviation distributions analysis in the finite element model:software MSC.Marc was used to observe the stress distribution of different methods. The three fixation ways were1.one point fixation at zygaomaticomaxillary butterss(ZMB)with L-type Titanium plate.2.three points fixation at zygaomaticomaxillary butterss and zygomaticofrontal suture and inferior orbital rim(ZMB+ZF+IOR) titanium plate.3.one point fixation at zygaomaticomaxillary butterss with absorbable plate.Results:1.The zygoma reconstruction of three-dimensional models had good mechanical geometric similarity.It is the finite element analysis of the three-dimensional finite element basis.2.3D finite element models of zygomatic fractures under different rigid internal fixation were constructed. One titanium plate fixation system finite element model consists of21339nodes and85720units;the three-point titanium plate fixation system finite element model consists of28613nodes and113655units; the absorbable plate fixation system finite element model consists of of32837nodes and129,206units.3.The vons-Mises stress distribution:the highest stress concentrated in the middle of the titanium plate in the L-type titanium plate fixation and the figures were30.32MPa (INC),98.84MPa (ICP),58.50MPa (RMOL) and63.39MPa (LMOL), while in the three titanium plates fixation. The vons-Mises figures69.73MPa,135.43MPa,103.14MPa and108.74MPa. In the absorbable plate fixation, the biggest stress concentrated in the middle of the top plate, in proper occlusion, the figures were23.51MPa,93.97MPa,56.69MPa and60.56MPa.4.Fracture mobility:fracture mobility was calculated for bite forces applied on incisors, fracture side and non-fracture side. In the L-type titanium plate fixation, the furthest mobility is0.121mm; in the three titanium plates fixation, the furthest mobility is0.061mm;while in the absorbable plate fixation, the furthest mobility is0.0926mm.Conclusions:1.3D FEM was a reliable way of analyzing the simple displaced fracture of zygoma. It could be used for a variety of finite element analysis of working conditions.2.Simulated the contraction of the masseter muscle over the functional occlusion. The vons-Mises stress distribution and fracture mobility were calculated from the3D finite element models of zygomatic fractures.3.The results showed that the three titanium plates fixation was more stable than the L-type titanium plate fixation.But the L-type titanium plate fixation could also provide sufficient stability for the zygoma fracture.4.The absorbable plate fixation had the similar effect as the L-type titanium plate fixation.