Systems Engineering From 3D Reconstruction In Mimics To FEA In Marc And Its Example

Background:1. Biomechanical study methods were usually to observe clinical cases, test human cadaver or animal experiment ago. Along with the development of computer FEA (Finite Element Analysis) gradually widely apply in biomechanical study, especially orthopedics biomechanical study. FEA is firstly applied in engineering research, but in recent years FEA begin to be applied in medical research. The methos have enormous advantages. It can analyse stress and strain of human inner structure, simulate surgery operation, and analyse times without number. The marerials of human cadaver experiments are difficultly acquired and only used up once, however, FEA is especially predominant.Application of FEA in biomechanical study relates to mathematics, mechanics, medicine, English and computeracy. If FEM (Finite Element Method) is based on researchers personally programme, the most researchers would come up against impassable obstacles about mathematics and computer programme. It is a lucky that business software of FEA had popularized and they have opend doorstep which researchers investigate biomechanics by right of FEA.Business software of FEA of which a large number of people make use have Ansys, Abaqus, Adina and MSC.Marc et al. MSC.Marc software is issued by MSC. Software Corporation of America. The software is very powerful in contact and nonlinear analysis,and can rapidly converge. The support organization of the research used large amount of money to purchase MSC.Marc software several years ago. MSC.Marc software is a large-scale non-linear FEA software which also relates to mathematics, mechanics, medicine, English and computeracy, so its manipulators are hard well up in it. Otherwise, there are few reference books in market, so the software has not adequately used in the support organization of the research and it is wasteful. The support organization of the research has also purchased Mimics software which is provided with powerful three-dimensional reconstruction and simple trimming model. But the function of simple trimming model of Mimics software is insufficient. MSC.Marc software is provided with MSC.Mentat which is a fore-and-aft processing unit of FEA and can plot out entity gridding. But the function of ploting out entity gridding of MSC.Mentat is too weak in the face of complex entity and successful rate is not enough. Mimics software can complete first step of FEA, and MSC.Marc can complete last step of FEA, but they miss middle process such as trimming model and ploting out entity gridding. Not only take into account science research, but also take into account to make the best of resource, it is necessary and impending to set up a systemic and intact path of FEA from 3D reconstruction in Mimics to FEA in Marc. Along with the path, there are many works to complete, such as three-dimensional reconstruction of triangle surface grids partitioning, trimming 3D model, establishing CAD model, geometry meshing on CAD model, setting geometric properties and material properties of elements, setting boundary conditions and load, submitting to FEA, dealing with the results of FEA.2. With the development of fixation instrument and fusion procedures of spine, successful rate of the spine fusion with bone graft and internal fixation has been very high, and the spine fusions with bone graft and internal fixation become the most effective way that cure spinal degeneration, instability and malformation. However, the degeneration of the adjacent segments comes forth after long term follow up.Some scholars and doctors begin to non-fusion spinal operations in place of fusion operation. The artificial disc replacement is one of non-fusion spinal operations. Mamy experts think that non-fusion spinal operations are sure-enough in effect in treat some symptoms, however, there are more problems to solve, and there are not evidences to make sure non-fusion better than fusion at the present time, so more long term researchs could judge advantages and disadvantages of non-fusion.Fusion or non-fusion? Anterior cervical discectomy and fusion with bone graft belongs to spinal fusion. Artificial cervical disc replacement belongs to spinal non-fusion. The two operations are two good comparison objects. If we can find advantages and disadvantages depend on FEA of two operation models, then provide theory for selecting operations of clinic cervical vertebrae indication.Objectives:1. On the basis of making the best of existing resources, to set up a systemic and intact path of FEA from 3D reconstruction in Mimics to FEA in Marc. Along with the path, there are many works to complete, such as three-dimensional reconstruction of triangle surface grids partitioning, trimming 3D model, establishing CAD model, geometry meshing on CAD model, setting geometric and material properties of elements, setting boundary and load conditions, submitting to FEA, dealing with the results of FEA.2. According to "Systems Engineering from 3D Reconstruction in Mimics to FEA in Marc", to construct 3D model of cervical discectomy and fusion with bone graft and artificial cervical disc replacement which are all operations to cure cervical diseases, to find advantages and disadvantages depend on FEA of two operation models, then provide theory for selecting operations of clinic cervical vertebrae indication.Materials and Method:1. Adopt Mimics software to reconstruct three-dimensional triangle surface grids partitioning model of C3, C4, C5 and C6, and make use of "Remesh" to trimming 3D model.2. Adopt Geomagic Studio software to better trimming 3D model of C3, C4, C5 and C6.3. Adopt Geomagic Studio software to constructe 3D model of intervertebral discs, nucleus pulposus and anulus fibrosus between C3 and C4, between C4 and C5, between C5 and C6.4. Firstly adopt Geomagic Studio software to constructe CAD model from 3D model of close triangle surface grids, and then adopt MSC.Patran software which is a fore-and-aft processing software of FEA to mesh tetrahedron on CAD model.5. Set geometric and material properties of all elements, and set boundary and load conditions of entire cervical vertebrae segments model in MSC.Marc software.6. Combine Geomagic Studio, MSC.Patran and MSC.Marc software to constructe 3D tetrahedron model of cervical discectomy and fusion with bone graft and artificial cervical disc replacement.7. Adopt MSC.Marc software to respectively set boundary and load conditions on 3D model of normal, discectomy and fusion with bone graft and artificial cervical disc replacement, and analysis biomechanical characteristics of adjacent segments of three models in the course of anterior flexion 15 degree, extension 15 degree, lateral bending 15 degree and axial rotation 15 degree.8. Adopt MSC.Marc software to post processing the results of FEA.Results:1. The research has constructed many 3D models, including triangle surface grids partitioning models, CAD models and tetrahedron models of C3, C4, C5, C6, and intervertebral discs, nucleus pulposus and anulus fibrosus between C3 and C4, between C4 and C5, between C5 and C6. All 3D models structure is clear and smooth, and meshes are continuous between adjacent models, and enough good to FEA.2. The research comes true from 3D reconstruction to FEA on the basis of combining Mimics, Geomagic Studio, MSC.Patran and MSC.Marc software.3. The maximal stresses of adjacent segment nucleus pulposus of three-dimensional models of normal, discectomy and fusion with bone graft and artificial cervical disc replacement ascend with the rise of degree during anterior flexion 15 degree, extension 15 degree, lateral bending 15 degree and axial rotation 15 degree. The maximal stress of superior and inferior adjacent segment nucleus pulposus of 3D model of artificial cervical disc replacement is less than discectomy and fusion with bone graft's during anterior flexion and extension 15 degree. The maximal stress of superior adjacent segment nucleus pulposus of 3D model of artificial cervical disc replacement is enormous less than discectomy and fusion with bone graft's during lateral bending and axial rotation 15 degree. However, the maximal stress of inferior adjacent segment nucleus pulposus of 3D model of artificial cervical disc replacement is bigger than discectomy and fusion with bone graft's during lateral bending and axial rotation 15 degree.Conclusions:1. The research implements a systems engineering from 3D reconstruction in Mimics to FEA in MSC.Marc on the basis of combining Mimics, Geomagic Studio, MSC.Patran and MSC.Marc software. The path completes three-dimensional reconstruction of triangle surface grids partitioning by Mimics software, trimming 3D model by Geomagic Studio software, establishing CAD model by Geomagic Studio software, geometry meshing on CAD model by MSC.Patran software, setting geometric properties and material properties of elements, setting boundary conditions and load, submitting to FEA, dealing with the results of FEA by MSC.Marc software.2. Summing-up the results of FEA, the maximal stress of inferior adjacent segment nucleus pulposus of 3D model of artificial cervical disc replacement is bigger than discectomy and fusion with bone graft's during lateral bending and axial rotation 15 degree. Stress concentration of adjacent segment maybe result in adjacent segment degeneration after discectomy and fusion with bone graft, and artificial cervical disc replacement is maybe avoidless similarly, and degeneration probability of inferior adjacent segment is bigger than superior adjacent segment.