| Objective:The segment T12-L2 finite element model of fresh OVCF with different reduction degrees was constructed by modeling software of computer-aided.On the basis of the model,the FEA software was used to simulate the five conditions such as upright,flexion,extension,left/right bending,and the equivalent stress(Von Mises stress value)of spine was obtained.To explore the biomechanical effects of different reduction degrees of fracture vertebral(L1)and adjacent vertebral endplates in the segment T12-L2,which could provide some theoretical guidance for the clinical application of TCM hyperextensive reduction in the treatment of fresh OVCF.Methods:1.CT scans to obtain original image data: A pure osteoporosis patient hospitalized in spine surgery of Affiliated Hospital of Gansu University of Chinese Medicine was selected.Excluding other medical history,the 64-slices CT in affiliated hospital was used to scan from the upper edge of T12 to the lower edge of L2 vertebral body.After obtaining the image,all CT images were saved in Digital Imaging and DICOM format.2.The finite element model of pure osteoporosis vertebral body was established:the three-dimensional finite element model of pure osteoporosis on segment T12-L2 was established by using Mimics 16.0,Geomagic Studio 2013,Solidworks 2017 and Ansys workbench 17.0 software.3.Model validation: 10.0N·M of torque and a compressive load of 150 N were applied to the upper surface of the T12 vertebra to simulate flexion,extension,left/right bending and left/right rotation of the vertebra under loading.The ROM value was measured during each condition,and results were compared with previously published in the literature to validate the rationality of the model.4.Biomechanical analysis of the model: Based on the validated three-dimensional finite element model,the three-dimensional finite element models of fresh OVCF with normal height and 90%,70%,50% and 30% reduction degrees at L1 were established respectively.500 N axial compression and 7.5N·M torque were implemented for upright,flexion,extension,left/right bending at the upper surface of T12 vertebral,the equivalent stress value and stress distribution of the fracture vertebral and the adjacent vertebral endplates under different reduction degrees were calculated.Results:1.The pure osteoporosis finite element model of segment T12-L2 was successfully established.On the basis of the normal model,the fresh OVCF finite element models with normal height and 90%,70%,50% and 30% reduction degrees were simulated,which can be used for biomechanical analysis.2.With the reduction degree decreased,it shown an increasing trend of the maximum Von Mises stress in injured vertebrae of cancellous bone,cortical bone and the same as adjacent vertebral endplates.Stress concentration mainly occurs in the cortical bone at the unfractured area,while in the cancellous bone at the fracture area.Conclusions:1.On the basis of CT images,using the relevant modeling software of computer-aided and the method used in this study,the fresh OVCF finite element models with different degrees of reduction can be well established,which were suitable for biomechanical research.2.The phenomenon of stress concentration in cancellous bone at fracture area may be the reason of low back pain,and the increased stress in adjacent vertebral endplate may lead to an increased likelihood of endplate and vertebral refracture.3.The results of models were given comprehensive analysis,we only consider the trends and magnitude of biomechanical changes,we think that 50% and 70% reduction degrees could be accepted.Of course,a better reduction and the relationship between the degree of reduction and clinical symptoms still need to be further considered. |
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