| Implant parts prepared by traditional design and manufacturing methods have the problems of large rigidity and heavier self-weight.These problems will lead to stress shielding effect between the implanted part and the host bone,which will cause loosening of the implant and directly lead to the reduction of the part’s implantation life and even the failure of the surgery.This article is based on 3D printing technology,which can break through the limitations of the traditional manufacturing process.Based on the guidance of the part-oriented functional requirements,the modeling method of the porous structural implant parts is studied.Firstly,the animal bone tissue was taken as the research object to analyze the characteristics of its organizational structure to obtain relevant parameters of the bone tissue,which would provide the necessary basis for the construction of the three-dimensional model of the porous implant model.Then the idea was constructed using the solid modeling method,based on computer-aided design technology and related modeling software,a porous implant model with gradient structure is constructed to achieve hierarchical gradient control of the mechanical properties of the implant part model.Using the idea of parametric model construction,a porous structure model was constructed based on a model construction method of an implicit surface function.A biomimetic bone structural porous implant unit model with a linear change characteristic was designed to achieve linear control of the mechanical characteristics of the porous implant part model.Finally,animal implantation experiments were conducted to examine the osseointegration effects of the porous implant components.The main research contents and achievements of the full text include the following aspects:(1)Through processing and analysis of animal bone tissue medical image data,the trabecular bone morphological parameters and mechanical parameters in the internal region of the femoral head were quantitatively analyzed using three-dimensional inverse model construction techniques and finite element simulation analysis techniques.From the measurement and analysis results,it was found that the three-dimensional morphological parameters and mechanical parameters of trabecular bone had significant regional differences.The analysis results showed that the cancellous bone in the bone tissue mainly consists of plateshaped bone trabeculae in the main load-bearing direction,but the cancellous bone is mainly formed by rod-shaped bone trabeculae in the direction of non-main load-bearing.These characteristics determine that the bone exhibits anisotropic mechanical properties along different load directions.The regional difference in mechanical properties,anisotropic properties,and regional differences in trabecular microstructure morphology are all important factors affecting bone performance.The results of the analysis of these types of parameters can serve as important reference data for the design of biomimetic porous bone implants.(2)Using the solid modeling method,the hierarchical gradient porous structure was introduced into the implanted parts.Through the regulation of model construction parameters,the apparent elastic modulus of the surface of porous implant that was in contact with the host bone tissue was similar to that of the bone tissue.The bulk body structure is still a solid structure to ensure the necessary mechanical support.Adding an excessively porous layer between the solid body and the surface pores to form a gradient structure can reduce stress mutations.On one hand,the use of such a gradient porous structure can effectively reduce the stress shielding effect between the implant and the bone tissue,and on the other hand,the porous structure in the implant can provide a specific microenvironment for the growth of bone tissue to achieve biological immobilization.(3)Based on the model construction method of the implicit surface function,a porous structure implant model with a linear change in pore structure was designed.By regulating the pore structure,the porous implant structure is linearly changed from the surface to the inner surface,so the surface elastic modulus of the porous implant in contact with the bone tissue is similar to that of the bone tissue,and the integrated elastic modulus of the implant structure far from the surface layer is gradually increased to ensure that the porous implant achieves the necessary mechanical support.And at the same time,its structural morphology and mechanical properties will not be mutated.This linear structure optimizes the mechanical properties of porous implants,and avoids the stress shielding effect,and can achieve a more ideal implant replacement.(4)The surface of the porous structure parts was modified and then animal implant experiments were performed.The osseointegration effect of the porous implants was analyzed through the stent deployment experiment.It can be inferred from the experimental results that the presence of new bone tissue extending around the surface of the porous implant extends into the medullary cavity in the constructed porous scaffold,and the binding interface between the porous structure implant and the host bone forms an effective osseointegration structure,and the implantation experiment achieves an ideal implantation effect. |
