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BACKGROUND:With social progress,the incidence rate of knee osteoarthritis is getting higher and higher in the face of the rapidly developing aging problem in the social population,and the number of total knee replacement operations is gradually increasing. OBJECTIVE:To study the relationship between prosthesis size and stress shielding by improving the tibial prosthesis base. METHODS:A female patient with severe knee osteoarthritis was selected.Based on Mimics,through extracting the bone structure of the knee joint and simulating the total knee replacement surgery,osteotomy,positioning,and implantation operations were carried out to establish the geometric modeling of the total knee replacement prosthesis(including the femoral prosthesis,tibial bracket,and tibial pad),and improve the design of the tibial prosthesis base,analyze the effect of different tibial prosthesis bases on stress shielding of surrounding bone tissue. RESULTS AND CONCLUSION:(1)Compared with single-stem tibial intramedullary stem prosthesis,the design of four-post tibial intramedullary stem prosthesis created a certain degree of stress shielding around the short stem.However,compared with a thicker single long stem,this stress shielding effect was significantly reduced,and the load was evenly distributed among the four short stems,so there was no stress concentration at the bottom of the pile.(2)The design with a rectangular hole in the middle not only provided relatively good stability,but also helped to reduce stress shielding of cancellous bone to a certain extent,with a reduction rate of 77.5%.(3)Compared with a single-stem tibial intramedullary stem prosthesis,both the four-post tibial intramedullary stem prosthesis and the four-post tibial intramedullary stem prosthesis with a hole in the middle have good stability,which can reduce stress shielding to a certain extent without causing stress concentration,providing theoretical guidance for the design of the tibial intramedullary stem.
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Objective Few studies are reported on the construction of a finite element model of human complex knee joint using multimodality CT and MRI images.In this study, we developed a finite element model of the knee joint for total knee arthroplasty (TKA) using matched and fused CT and MRI data, hoping to provide a useful tool for the simulation study of knee joint biomechanics of TKA.Methods The CT and MRI image data about an intact knee of a 26-year-old male volunteer were imported into the Mimics software for the establishment of 3D models of bony and soft-tissue structures.A complete knee model was developed following the registration and fusion of the constructed 3D models based on the external landmarks.After the simulated implantation of TKA components, a finite element model of the TKA knee was constructed with the Hypermesh software.Then the finite element model was analyzed following the definition of its material behavior, boundary conditions and loading.Results The finite element model of the TKA knee, which was composed of bones, ligaments, components, polyethylene insert and bone cement, was developed from CT-MRI image registration and fusion and maintained its important spatial relationship among different structures in the TKA knee.The results obtained from the finite element analysis showed the characteristics of stress distribution in the TKA knee.Conclusion The finite element model of the knee joint for TKA can be established by matching and fusing CT and MRI image data, which can be employed as a useful tool for the study of knee joint biomechanics of TKA.
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Objective To evaluate the reversion possibility of hVEGF165 and TGF?1 to intervertebral disc degeneration by gene method. Methods The hVEGF165cDNA obtained from plasmid pcDNA3(+)-hVEGF165 was subcloned into the packaging plasmid pSNAV of AAV by molecular clone ways. The recombinant plasmid pSNAV-hVEGF165 was identified by restriction enzymes analysis and sequencing analysis, and then transfered to the HEK293 cell and VEC by lipofectamine mediated gene transfer method. The protein hVEGF165 was detected by immunofluorescence for immunocytochemistry and explored the influence to the proliferation of vascular endothelial cell by MTT. Whereafter the AAV-hVEGF165 was packaged by Benyuan Zhengyang Company. AAV-hVEGF165 and AAV-TGF?1 were cotransfected into annulus fibrosus cell of intervertebral disc, then the expression of hVEGF165 and TGF?1, and the change of collagen Ⅰin annulus fibrosus cell were detected by Western blot. Results The recombinant pSNAV-hVEGF165 was completely constructed and confirmed by restriction enzymes analysis and sequencing analysis. The protein hVEGF165 was detected by immunofluorescence for immunocytochemistry in experimental group, and hVEGF165 could promote the proliferation of vascular endothelial cell. The bioactive AAV-hVEGF165 was successfully constructed. The expression of AAV-hVEGF165 and AAV-TGF?1 were manifested in degenerative annulus fibrosus cell by Western blot, and the expression of collagen Ⅰin annulus fibrosus cell cotransfected by AAV-hVEGF165 and AAV-TGF?1 was markedly more than that of the monogenic transfected cell. Conclusion hVEGF165 could cooperate with TGF?1 to promote the expression of collagen Ⅰ.