Multi-scale Study On The Effect Of Prosthesis On Femoral Bone Remodeling

Total hip arthroplasty is considered to be an effective treatment for femoral head necrosis,rheumatoid arthritis,and degenerative hip osteoarthritis,but there is a 10 %risk of prosthesis loosening within 10 years of surgery.Stress shielding caused by implant placement is considered to be the main cause of prosthesis loosening after total hip arthroplasty.In this study,the process of femoral bone remodeling and the osteological properties of the artificial prosthesis after implantation were analyzed at macro and micro scales,hoping to provide theoretical basis and ideas for the improvement and optimization of the traditional total hip arthroplasty prosthesis and the design and preparation of personalized prosthesis with bone trabecula.This study carried out the following work:(1)In the secondary development environment of ABAQUS,the bone remodeling control equation was used to write the bone remodeling program for the numerical simulation of macro bone remodeling of femur after prosthesis implantation.A cantilever beam model is used to verify the algorithm,and the obtained truss structure is consistent with the previous research results,which proves the effectiveness of the self-designed program.(2)Healthy femur model and femur-prosthesis model after total hip arthroplasty were established respectively,and bone reconstruction algorithm was implemented to simulate the process of bone tissue remodeling in the two states.The results showed that after total hip arthroplasty,the maximum stress of proximal femur decreased from osteotomy position to about 2cm along the femoral shaft,decreased by 54.24%,resulting in obvious stress shielding,which may cause the prosthesis to become loose occur in the long term.The medial side of the stem bottom of the prosthesis is squeezed,and the unit stress value is higher than that of the lateral 29.27%.The difference in the stress level of the medial and lateral parts may lead to problems such as the incompact coordination between the prosthesis and the femur.(3)The 3D printed porous titanium alloy scaffold was implanted into the right femoral condyle region of New Zealand white rabbits.The white rabbits without the stent were set as the control group.After 90 days of feeding in the same environment,the femoral samples were sacrificed to obtain,and the samples were scanned by microCT technology.MIMICS and VGStudio Max software were used to compare the bone trabecular images and morphological parameters of the two groups of white rabbits.It was found that a certain number of bone trabeculae were distributed inside the scaffold,indicating that the bone trabeculae were growing endogenous to the porous structure.Although the number of trabeculae on the contralateral side of the femoral condyle and around the scaffolds decreased slightly,the volume fraction,specific surface area,indicating that porous titanium alloy scaffolds were generally beneficial to the growth of trabeculae in the femoral condyle region and promoted the process of femoral bone remodeling.(4)A microscopic finite element model of the femoral condyle region was established to ensure the integrity and authenticity of the internal bone trabecular structure and simulate the mechanical environment of the normal physiological state of the white rabbit for finite element calculation.The results showed that trabecular bone around the front and upper surface of the porous scaffold did not receive enough mechanical stimulation,resulting in stress shielding and significant degeneration of the trabecular bone.The contact stress between the inner axial side and the trabecular bone promotes the adaptive remodeling of the trabecular bone at the contact surface.The trabecular bone around the lower contact surface is subjected to the gravity of the scaffold and can feel the mechanical stimulation to maintain the morphology and structure,which ensures that no stress shielding occurs at this location.