Medical Imaging-Based Prediction Of The Mechanical Microenvironment After Knee Arthroplasty

UKA and TKA are considered effective treatments for advanced osteoarthritis of the knee.However,there is a certain risk of complications that can lead to failure of the procedure.How to reduce the probability of post-operative complications is a problem to be addressed in the current study.In this study,the process of tibial bone reconstruction and the mechanical microenvironment after knee arthroplasty are analysed in both simulation and experiment,in the hope that this will provide data to support the reduction of the probability of postoperative complications and provide a reference for the selection of the appropriate surgical procedure for the patient,and therefore the following work is:The bone reconstruction control equations proposed by Weinans were implemented using the Python scripting language and the bone self-optimisation equations based on strain energy density theory were written as a bone reconstruction program using the secondary development environment of ABAQUS for the numerical simulation of bone reconstruction after implantation of different model prostheses.Using a real-time high-speed six-dimensional dynamic tracking system,the tibial anteversion angle of 11° and the valgus angle of 9° were measured in the standing condition of the volunteer’s legs,and the direction of the applied load was determined for the subsequent finite element simulation and experimental study of the tibia.A 3D model of the healthy tibia was established based on CT images of the left lower limb of the volunteer,and a 3D model of the postoperative tibia was established by osteotomy of the healthy tibia.At present,most of the studies on bone reconstruction are done based on 3D models,and the number of units in 2D models is small.The magnitude of the loads was calculated from the load magnitude of the 3D finite element model.Sawbones 4th generation artificial composite bone was selected for the experiments.The same load was applied to it as the 3D healthy tibia finite element model,and the strain data of its corresponding regions were measured by digital image technique and compared with the finite element results.It was found that the difference between the medial tibial ankle was 1.6% and the lateral ankle was 2.2%,and the difference between the results of both regions was small,which can indicate that the finite element model of this study is reliable.A 3D bone reconstruction program was run on the 3D model to simulate the bone reconstruction process and to obtain the stress distribution and density distribution of the 3D model bone.The results showed that compared to the healthy tibia,the mean stress and mean density of the lateral ankle of the UKA were basically unchanged at the beginning and tended to decrease and then increase,while the mean density and mean stress of the medial ankle were reduced by 37%.increased by 16% and 21%respectively.A 2D bone reconstruction program was run on the 2D model to obtain the stress distribution and density distribution of the 2D model bone.The results showed that compared to the healthy tibia,the mean stress in the UKA lateral ankle was basically unchanged but tended to increase,with a 2% increase in mean density and a 13% and 11% decrease in mean density and mean stress in the medial ankle,respectively.the mean density and mean stress in the TKA lateral ankle and the mean density and mean stress in the medial ankle decreased by 1.5%,14%,1.4% and 19%,respectively,and the mean density and mean stress at the end of the prosthesis stress increased by 10%and 15% respectively.The stress distribution and density distribution results show that the UKA implant side and both sides of the TKA prosthesis produced significant stress masking,which may have been the main cause of postoperative prosthetic loosening;the increased stress at the end of the TKA prosthesis may have led to the failure of the TKA;the average stress on the non-replacement side of the UKA increased as the bone reconstruction progressed,which may have led to worsening osteoarthritis on the contralateral side of the UKA in the medium to long term.By comparing the results of the 3D and 2D models,it was found that the calculations were significantly faster and more efficient when using the 2D model due to the smaller number of units.The data fluctuations in the results using the 3D model are greater,which is more beneficial to the analysis of the results.The magnitude of stress variation and density variation were also closer using the 3D model,indicating that it is more reasonable to build a 3D model when performing finite element analysis on the tibia.