| Objective:Based on the problem of the high incidence of long-term aseptic loosening and limited lifespan of the current rotary hinge knee prosthesis,establish a finite element model for the coupling analysis of kinematics and contact mechanics of the new spherical motion axis rotary insert hinge knee prosthesis.Develop a numerical calculation method for the wear of hinged knee joint prostheses.Compare and analyze the influence of different prosthesis designs on the wear performance of hinged knee joint prostheses.Compare and analyze the influence of different daily activity gaits on the wear of hinged knee joint prostheses.Methods:1.Establishment of the finite element model of the spherical motion axis rotary insert hinge knee prosthesis.Import the prosthesis into the finite element software,perform material assignment,mesh division,set contact attributes,apply boundary conditions,establish contact relationships,etc.Through the simulation of the mechanical environment under the force control of ISO 14243-1 2009,the internal and external rotation of the prosthesis was predicted,and the contact mechanics of the prosthetic joint surface during the entire gait cycle was analyzed.2.Establishment of wear model of knee joint prosthesis with spherical motion axis rotary insert hinge knee prosthesis.Based on the previously finite element mechanical analysis,the kinematics of each component were output,the contact stress of each wear surface of the polyethylene component was extracted,and the relative motion,sliding distance and alternation were calculated.Cross-shear ratio,based on the numerical calculation model of alternating shear wear of ultra-high molecular weight polyethylene,calculate the wear depth for each node of the surface,modify the node coordinates of the polyethylene component according to the wear depth,and then modify the prosthesis geometry and perform the finite element analysis again,and output kinematics and contact mechanics to realize the automatic iteration of wear calculation.According to ISO,complete 5 million cycles of wear numerical simulation,and finally output the results of wear volume,wear area,wear distribution,etc.Then the method of wear calculation of hinged knee joint prosthesis was established.3.Comparative analysis of the wear performance of different structural designs of hinged knee joint prostheses.refer to the wear model of the hinged knee joint prosthesis with the spherical motion axis rotating gasket,establish the wear calculation model of the biaxial rotating hinge type prosthesis,and compare the prostheses of different structural designs.The difference between the results of kinematics,contact mechanics,and wear reveals the effect of prosthesis design on kinematics,contact mechanics and wear;as the wear process evolves,explore the effects of geometric changes of polyethylene components on kinematics and contact mechanics Influence,clarify the interaction between kinematics,contact mechanics,and wear.4.Comparative analysis of the wear of hinged knee joint prosthesis under different daily activity gaits:Based on the ISO 14243 walking gait wear simulation,predict the kinematics of the spherical motion axis hinged knee joint prosthesis in the upstairs and downstairs gait.Contact mechanics and wear,and analyze the influence of gait differences on the kinematics,contact mechanics and wear of the prosthesis.Results:1.Finite element model:A method of coupling analysis of kinematics and contact mechanics was established.Under the condition of ISO 14243-1:2009force-controlled gait,the kinematics and kinematics of the spherical motion axis rotation pad hinge knee prosthesis were established.Simultaneous prediction of contact mechanics shows that the rotation range of the tibial tray prosthesis is as high as 22°,and the rotation range of the liner is 1.2°.The upper and lower surfaces of the polyethylene liner obtain a larger contact area and lower contact stress due to the high matching design.There is a brief contact between the bushes.2.Wear numerical calculation model:Based on the above finite element results,a numerical calculation model for the wear of the knee joint prosthesis with the spherical motion axis rotating pad hinge is established,and 5 million cycles of wear are completed under the ISO14243-1:2009 force-controlled gait.Numerical Simulation.Results After five million cycles,the volume wear rate of the upper surface of the liner was 10.02 mm/~3,the volume wear rate of the lower surface was 14.86 mm/~3,and the volume wear rate of the ball bushing was 0.04 mm/~3.3.Comparative analysis of different structural design prostheses:Coupling analysis of kinematics,contact mechanics,wear numerical calculations on the rotating hinge type II distal femoral tumor prosthesis,and further comparison with the ball axis spherical motion axis rotating pad hinge knee joint prosthesis,the results show that:rotating hinge Type II distal femoral tumor prosthesis liner has a rotation range of only 3°.The upper surface of the polyethylene liner of this prosthesis wears 0.73 mm~3/mc,and the wear of the inner surface of the inner and outer shaft sleeves is 0.51 mm~3/mc and 0.54 mm~3/mc.4.Comparative analysis of the influence of different daily activity gaits on the wear of the spherical motion axis rotation pad hinge knee joint prosthesis,the results show that:in the stair gait,the tibial tray rotation range is 26.8°,the pad rotation is 0.4°,and the pad is on The volume wear rate of the surface is 9.85 mm~3,the volume wear rate of the lower surface is 29.2 mm/~3,and the volume wear rate of the ball bushing is 0;in the downstairs gait,the tibial tray rotation range is 31.15°,the liner rotates 0.3°,the liner The volume wear rate of the upper surface is 9.62 mm/~3,the volume wear rate of the lower surface is 23.8 mm~3,and the volume wear rate of the ball bushing is 0.Conclusions:1.Spherical motion axis rotation pad hinge knee joint prosthesis tibial tray has a large internal rotation and external rotation motion range,which is conducive to stress transmission at the bone-prosthesis interface;the high matching design of the rotation pad and the femur leads to a large contact area and small contact stress.The dynamic contact performance is good,and there is a short contact between the ball shaft and the bushing.2.Knee prosthesis with spherical motion axis rotating pad hinged knee joint prosthesis wears slightly larger than the surface knee prosthesis,but within a reasonable range,the main reason is that the wear includes the upper and lower surfaces of the polyethylene liner,and the upper and lower surfaces are rubbed against the pair.The surface is of high matching design,the contact area is large,and the wear in the numerical model is proportional to the contact area;at the same time,the wear of polyethylene is proportional to the alternating shear,and the large amplitude of internal rotation and external rotation further leads to a large wear volume rate.3.The rotating hinge type II distal femoral tumor prosthesis has a small amplitude of internal and external rotation and small alternating shear under the phase synchronization state;the shaft and sleeve are unidirectional rotation with alternating shear rate It is zero;only the upper surface of the polyethylene liner and the tray constitute a friction pair,and the friction surface is less.Therefore,the calculated wear volume is smaller than that of the spherical motion axis rotating liner hinged knee prosthesis.The difference in mechanics and wear is significant.4.Compared with ISO walking,the range of internal and external rotation of the tibial tray increases,the liner hardly rotates,the wear volume rate of the bottom surface of the liner increases,and the overall wear rate increases.In the process of going up and down the stairs,the ball axis There is no contact with the bushing,no wear,and the gait has a significant influence on the wear of the prosthesis. |
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