| Knee osteoarthritis is one of the common geriatric diseases,and its incidence has risen sharply with the aging of the social population.Total knee arthroplasty(TKA),as an important medical means to solve knee joint diseases,has received great attention in the field of medical research.However,stress shielding is a common problem after implantation,which increases the risk of prosthesis loosening.With the development of computer aided design,3D printing titanium alloy porous scaffolds as a new structure have been used in orthopaedic implants.3D printing technology has a controllable and precise manufacturing process that provides individualized implants for patients.Titanium alloy porous implants can reduce the stress shielding effect by adjusting the porosity to match the structure of human cancellous bone.At the same time,there is enough space on the surface of the implant to promote bone tissue growth and enhance the stability of the bone-prosthesis interface.At present,scholars have designed and manufactured 3D printed titanium alloy prostheses for jaw,hip and other parts,but there are few studies on the design and analysis of knee joint prostheses by finite element method.The main contents of this paper as follows: A finite element model of normal human knee joint is established based on MRI image,appling 1150 N axial compression load to the reference point of human kinematic,verified the validity of the model.Three types of unit cell,cube,tcube,ocatahedal,were selected to establish a single structure of porous structure.Displacement loads were applied to simulate mechanical compression experiments on the upper surface of the porous structure,the influence of unit cell geometry on the strength and stiffness of porous structure of titanium alloy was studied by finite element method.Simulating the osteotomy,implantation and positioning of total knee arthroplasty,the geometric models of four total knee arthroplasty prostheses(femoral prosthesis,tibial prosthesis,ultra-high molecular-weight polyethylene(UHMWPE))were established.That is,four different tibial prosthesis structures(including a metal prosthesis stem and three porous metal prosthesis stems)to investigate the effects of different porous structures on the stress shielding of bone tissue around the tibial prosthesis stem in TKA model.The analysis results show that the maximum von Mises stress in the proximal tibia of all porous TKA models is reduced by approximately 66.71%.Compared with the solid structures,which greatly reduces the stress shielding.The maximum compressive stress of UHMWPE is less than 1 MPa,which reduces the wear between metal prosthesis and UHMWPE,and improves the service life of the prosthesis.In the octahedral TKA prosthesis model,the porous segments of tibial prosthesis stem bear the greatest stress,which can better transmit the load of the knee joint.Compared with the cubic and tcube porous structures,the maximum von Mises stress of the bone around the stem of octahedral porous tibial prosthesis was reduced by 3.9% and 7.7%,respectively.The stress shielding phenomenon was alleviated,effectively reducing postoperative pain and the possibility of loosening of the prosthesis.In this study,four models of total knee arthroplasty were established and simulated for finite element analysis to investigate the influence of the geometric structure of porous segment element of tibial prosthesis stem on the mechanical behavior of proximal tibia.It provides a theoretical basis for the design of TKA prosthesis,and provides a reference value and scientific guidance for the feasibility of porous titanium alloy knee prosthesis and TKA operation. |
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