Study On Design And Manufacture Of Porous Structure Implanted Prosthesis For Femur And Tibia

Prosthesis implanting is a main method in the repair of large segmental bone defects,which can directly influence the rehabilitation effect of bones.In clinical treatment,a stress shielding effect is often caused due to the excessive elastic modulus of the implanted prosthesis,thus leading to the bone tissue may be absorbed.The stress shielding effect may cause a decrease in the strength of the connection between the prosthesis and the bone,even the prosthesis detachment.In view of this problem,aiming at designing an implanted prosthesis with a reduced stress shielding effect,a design method of personalized implanted prosthesis was proposed.Based on the structural characteristics of the equivalent bone and the biological properties of the human body,the rapid manufacturing method of the equivalent bone was optimized.In simulating the clinical cases with bone repair defects,the feasibility of using equivalent bone in the clinical repair of bone defects was demonstrated by means of bone reduction,bone defect model establishment and numerical calculation,and the effectiveness and practicability of equivalent bone design were verified by comparing the numerical calculations with animal experiments.The main research contents are as follows:(1)A personalized three-dimensional model of human bones and prostheses was built.The equivalent elasticities of the human femur and tibia were measured by nanoindentation method,and differences between them were analyzed.Based on this,a human skeleton model was constructed in a way of reverse engineering and the deviation was detected,thus a skeletal modeling methodology was proposed,involving the assignment of ten material properties gradients based on bone grayscale,and allowing for realistic depiction of local stress distribution during skeletal loading.(2)The type of porous structures suitable for implanted prostheses was chosen.Numerical analysis techniques were used to analyze the mapping interrelation between various porous structures and their mechanical properties.By comparing the isotropy and equivalent elasticity of the porous structures,the porous structures were selected first.The processability and bone ingrowth of various porous structures were evaluated by establishing an evaluation method with numerical simulation,mechanical experiments and animal experiments.Finally,the type of porous structure suitable for implant design was determined.(3)A equivalent bone designing plan was developed.Firstly,a concept of equivalent bone was proposed,and the functions among the unit mass,equivalent elasticity and structural parameters of the equivalent bone were respectively established and the accuracy of the functions was verified by mechanical experiments.Furthermore,parameters of the implanted prosthesis were optimized and designed by genetic algorithm to establish an optimal design method for equivalent bone.Moreover,the stress distribution of femoral implants in both upright and walking states of the human body was analyzed by numerical calculation methods,and the stress distribution of the prosthesis and its surrounding bones with different equivalent elastic prostheses implanted in the bone was analyzed under both static and dynamic conditions to verify the necessity of using equivalent bone design to repair bone defects.(4)The processing technology is optimized.Considering the structural characteristics of equivalent bone,SLM processing technology was adopted for manufacturing,and the existing processing technology was improved by analyzing the influencing factors like forming direction,heat treatment,and forming parameters during the forming process of titanium alloy equivalent bone.Under the premise of ensuring the forming quality,the equivalent elasticity of the finished product was reduced,making it closer to the equivalent elasticity of human bones.At the same time,the necessity of heat treatment in the equivalent bone processing was affirmed.(5)Numerical analysis and experiment of equivalent bone was launched.Through simulating the treatment of the clinical cases with bone defects caused by the repair of open femoral fractures,and applying the proposed equivalent bone design method,an implant prosthesis with similar profile shape,unit mass and equivalent elasticity to those of the patients in bone properties was built,and the impact of the equivalent bone on the patient’s postoperative rehabilitation was analyzed by numerical calculations to confirm the feasibility of the equivalent bone design method in clinical treatment.The practicability and effectiveness of the equivalent bone design method in this study were analyzed by comparing the numerical calculation with the animal implantation experiment,indicating that the method for the repair of bone defects can effectively reduce the stress concentration and improve the growth rate of surrounding bone tissues.In this study,a design method of prosthesis with porous structure and a evaluation method of the prosthesis structure were proposed by studying the implanted prosthesis.On this basis,a concept of equivalent bone was proposed,and a design method for the optimization of prosthesis structure was established.It may be confirmed through the theoretical calculations and animal experiments that this design method can effectively reduce the stress shielding effect,and the application of this method can provide a theoretical basis and technical support for the rehabilitation of patients and the manufacturing of prostheses by doctors.