| Maxillofacial region locates in the exposed part of human body,rendering it being prone to outside impact.In addition,the maxillofacial region is next to the brain;as a result,concomitant craniocerebral injury in the case of being impacted is the most commonly seen concomitant injury of maxillofacial impact injury.With the rapid development and popularization of automobile industry in recent years,maxillofacial injuries that accompanying with craniocerebral injuries caused by traffic accidents occur frequently.How to improve the successful rescue rate of maxillofacial impact injury(MII)accompanying with craniocerebral injury becomes the challenge for maxillofacial surgeons.Therefore,understanding the rules and characteristics of MII towards craniocerebral injury is the key to solving the challenge.Finite element method(FEM)is widely applied in the fields of engineering and biomechanics as a result of its good repeatability as well as its capacity to substitute lots of animal experiment.We had successfully simulated the dynamic simulation process of bullet wound and explosion injury in swine lower mandible in the earlier stage,and it had been verified through animal experiment,fully proving the feasibility of FEM in analogue simulation in biomechanics.The research conducted dynamic simulation of the MII to simulate the stress conduction and distribution in the base of skull after facial impact,collected simulation result data for analysis,and explored the rule of facial impact injuries in various sites towards injuries in the base of skull through constructing 3D finite element model of craniomaxillofacial bone tissue and utilizing finite element analysis simulation software such as Hypermesh and LS-DYNA.The research also attempted to conduct biomechanics experiment verification of the maxillofacial region through 3D printing skull,and consequently probed the feasibility of 3D printing model into finite element biomechanics analysis and verification.Methods:Analogue simulation of the MII: imported the collected data of digital imaging and communications in medicine(DICOM)obtained through computed tomography(CT)scanning of the craniomaxillofacial region of the volunteer into the Mimics 15.0 software for 3D reconstruction,conducted volume meshing in the Hypermesh software,completed construction of 3D finite element model of the craniomaxillofacial region,set impact conditions as well as all parameters in the LS-DYNA software and calculated the injury process of impact.Relevant data were obtained for analysis.Analogue simulation of the MII: imported the collected data of digital imaging and communications in medicine(DICOM)obtained through computed tomography(CT)scanning of the craniomaxillofacial region of the volunteer into the Mimics 15.0 software for 3D reconstruction,conducted volume meshing in the Hypermesh software,completed construction of 3D finite element model of the craniomaxillofacial region,set impact conditions as well as all parameters in the LS-DYNA software and calculated the injury process of impact.Relevant data were obtained for analysis.Results:1.A 3D finite element model that had the consistent height of contour with the craniomaxillofacial bone of the volunteer had been successfully constructed,with the mesh quantity of 72962.2.Dynamic simulation of the impact injury in the right maxilla,left infraorbital margin and left zygoma in the maxillofacial region was conducted,with the impactor being a rigid cylinder of 3cm in basal diameter,and 5kg in mass,and at an impact velocity of 8.6m/s.Distinct fracture and displacement of the fracture fragment occurred in the right maxilla and zygoma when the right maxilla was impacted,while local comminuted fracture occurred when the infraorbital margin and the zygoma were impacted.3.Obtained the craniomaxillofacial stress nephograms when the three impact sites were impacted,as well as the stress-time variation curves of all cranial basal landmarks through finite element analysis and calculation.Compared the stress size of all cranial basal landmarks at the same moment,and the time needed for all cranial basal landmarks to achieve the maximum stress value during impact.4.Conducted facial load test with 3D printing skull,and measured the strain values of all cranial basal landmarks to compare with those obtained through steady simulation in ANSYS WORKBENCH.5.Comparative analysis of the strain values of all cranial basal landmarks measured in WORKBENCH steady simulation and load test indicated that there was high consisitency.Conclusion:1.From the perspectives of geometrical and mechanical properties,reconstructing a 3D model of human craniomaxillofacial bone through CT scanning data and Mimics software had extensive application prospect because of its high level of similarity and relatively mature technology.2.Finite element application software such as HYPERMESH and LS-DYNA could simulate the dynamic process after the maxillofacial region was impacted,and the distribution of fracture line,together with the displacement of fracture fragment was basically consistent with the typical injury conditions in the teaching materials.3.Simulation of maxillofacial impact injury could demonstrate the stress conduction and distribution in the base of skull,and typical region of stress concentration in the base of skull after various facial sites were impacted could be discovered through data analysis,providing theoretical foundation for the prevention and protection of MII.4.The results of load test on 3D printing craniomaxillofacial bone model were consistent with those in finite element ANSYS steady simulation.Analogue simulation that verifies MII with 3D printing craniomaxillofacial bone can be attempted in the next step. |
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