The Stress Effect Of Simulating Defect On Medial Femoral Condyle Cartilage To Cartilage And Meniscus

BackgroundWith the improvement of the quality of living standards of people, cartilage lesions are more prevalent than previously, the pathophysiology of cartilage injury has been made in a wide range of understanding, but few studies focus on explicate the quantitative change of knee joint biomechanics after cartilage defect on the femoral condyle weight-bearing area. With the development of digital simulation model techniques and finite element analysis, the traditional biomechanical experimental method is being replaced by finite element analysis, which have achieved a lot. Therfore, based on clinical epidemiological studies in recent years on the cartilage injury, the research established the three-dimensional digital geometry model and finite element model of the total knee reasonably and accurately, and studied the effects on meniscus and cartilage and biomechnical factors after articular cartilage defects, which is the common injury on the femoral condyle, with the dimensional finite simulation element analysis. it could provide a new means for the repair and reconstruction of the knee articular cartilage biomechanics research.ObjectiveTo establish the three-dimensional finite element model of knee which had articular cartilage defects utilized three-dimensional digital reconstruction technique and reverse engineering technology. And simulation research on the stress distribution characteristics of the normal knee articular cartilage and meniscus at different flexion angles, and finite element simulation study on the impact of cartilage defect on the weight-bearing area of femoral condyle cartilage to meniscus and cartilage.Methods 1. One healthy adult volunteer was chosen, whose right knee was scanned by magnetic resonance imaging with interval of1.0millimeters. Based on this continuous image data, the piont clond data of various knee structures were obtained by Mimics14.11and Geomagic Studio2012software. From this data, a there-dimensional digital model was reconstructed with the software included distal femur, proximal tibia, articular cartilage, ACL, PCL, meniscus, quadriceps femoris and fibula. Outcome was saved in format of STL, and then STL data was imported into Geomagic Studio2012software to fix and fitting surface. Finally, the surface was converted to3-D geometry model by Pro/Engineer software and there-dimensional finite element modle by ABAQUS6.9software.2. By means of ABAQUS software the there-dimensional finite element modle were post-processing. After the models were recorded in material mechanical characteristics, restrained boundary conditions and loaded, the stress nephograms of meniscus and cartilage at different flexion angles were conducted claculation and analyzed to explore the biomechanical characteristics. Then by means of reverse engineering techniques, we builded a3D finite element model of total knee, which diameter was8mm size of defect on the weight-bearing area of femoral condyle cartilage. Finally, the stress nephograms of meniscus and cartilage during knee flexion and analyzed the changes of meniscus and cartilage biomechancis at different flexion angles. The result provided theory instruction for cartilage repair in clinics.Results1. Based on MRI scan image, the total knee three dimensional geometry model and three dimensional finite element model were set up rapidly and efficiently using Mimicsl4.11、Geomagic Studio2012、Pro/Engineer5、ABAQUS software, which composed of bone, cartilage, meniscus, ligament. the models were characterized by the higher geometric similarity, the accuracy of the structure and efficient meshing, high-quality element, which was beneficial to finite element analysis of all structures in the knee and estiblashed biomechanical analysis platform of healthy knee jionts in our courtry. 2. Based on the three-dimensional finite element model which had been constructed, to virtual establishment of three dimensional finite element model which diameter was8mm size of defect at femoral condyle weight-bearing cartilage utilizing three-dimensional digital reconstruction technique. And finite element analysis of the stress of articular cartilage and the meniscus under0°,30°,60°,90°lexion angle of knee, the results showed:the stress of articular cartilage and meniscus had significantly increased when the medial femoral condyle cartilage had defect, the stress on the lateral and medial cartilage of femur condyle, lateral and medial cartilage of the tibia plateau, lateral and medial meniscus had increased under flexion angle of0°, respectively by64.8%,70.9%,83.6%,109.5%,16.3%; under flexion angle of30°respectively by75.8%,95.9%,58.6%,58%,72.1%,30.5%; under flexion angle of30°respectively by90.9%,67.6%,76.0%,75.9%,140.9%,24.7%; when under90°flexion angle, the difference of the stress was not statistically significant.Conclusion1.3-D finite element model of medial femoral condyle cartilage defect which was established virtually could accurately quantify the biomechanical change tendency of articular cartilage and meniscus after weight-bearing area of the femoral condyle cartilage had defected.2. The peak stress force of medial femoral condyle cartilage, medial tibial plateau cartilage and lateral meniscus were greater than the peak stress force of lateral femoral condyle cartilage, lateral tibial plateau cartilage and medial meniscus.3. When5zone of medial femoral condyle cartilage defect which diameter was8mm, the stress of articular cartilage and meniscus significantly increased under0°,30°,60°flexion angle of knee.