| Hip joint is one of the important joints to maintain the daily activities of the human body.At the same time,it is relatively easy to damage and cause disease.At present,hip replacement is an effective method for treating hip joint diseases.As patients gradually become younger,how to prolong the service life of hip joint prostheses is a hot topic in recent years.The rapid development of computer aided design(CAD)and three-dimensional printing(3D printing)has provided new technical support for the optimal design of hip joint prostheses.3D printing technology has a precise and controllable manufacturing process for tiny pores,which can be used to design individualized prostheses for patients.The porous structure can be obtained by orderly stacking the unit cell structure in a three-dimensional space.Designing the interior of the hip joint prosthesis as a porous structure can enhance the stability of the prosthesis,alleviate its stress shielding phenomenon,and extend its service life.The main contents of this dissertation are as follows: first of all,four different unit cell structures are selected,i.e.the cube,the diagonal,the cylindrical octahedron,and the body-centered cube.The pillar diameter of the unit structure is set between 700-1000μm,the pore size is designed as 600μm,and the porosity is designed to be 49%.Four different porous structures of titanium alloy were obtained by arranging four different cell structures in three-dimensional space.Four geometric models of porous structure and corresponding finite element models are established.Finite element analysis was performed by simulating compressive mechanical test to explore the differences in mechanical properties of different porous structures.Subsequently,3D printing technology was used to create the porous structure model corresponding to finite element models.Porous structures were analyzed for morphological parameters and surface topography,and the mechanical properties of different porous structures can be acquired through compression experiments.The differences in mechanical properties of different porous structures were explored through finite element analysis and compression experiment.Finally,the porous structures were put into the hip joint prosthesis to establish a dense hip joint prosthesis model and four different porous hip joint prosthesis models.Finite element analysis was performed to apply a displacement load on the top of the hip joint prosthesis to simulate a bending test to investigate the effects of different types of porous structures on the mechanical properties of hip joint prosthesis.The results show that the porous structure can reduce the elastic modulus of the structure compared with the dense structure,and can match the mechanical properties of the human skeleton(The elastic moduli of the four porous structures are in the range of those of the cancellous and cortical bones of the human body,i.e.between 0.05-20GPa).The cubic porous structure has higher yield strength and strength limit than the other three porous structures,and its mechanical properties are superior.The porous structure was placed in the hip joint prosthesis.And the results show that the four porous hip joint prostheses can effectively reduce the bending strength of the prosthesis and relieve the stress around the prosthesis compared with the dense hip joint prosthesis.Among them,the cubic hip joint prosthesis performs better,its stress distribution is more uniform compared with the other porous hip joint prostheses,and its bending stiffness is 4422N/mm.It can more effectively reduce the risk of loosening of prosthesis after surgery and prolong the service life of hip joint prosthesis.This study shows that designing a porous structure inside the hip joint prosthesis can reduce the bending stiffness of the prosthesis,reduce the stress shielding phenomenon around the prosthesis,enhance its stability,and extend its service life.This dissertation provides the basis for the design and research of clinical hip prosthesis,and provides scientific guidance and reference for the feasibility of porous hip prosthesis and hip replacement. |
