Biomechanicalanalysis On Knee Joint Ligament And Meniscus

Objective1.To construct a three-dimensional finite element model of a normal knee joint with computationaltechnology and validate its finite element model.2.By taking medial collateral ligaments and meniscus of a knee as an example,and through a simulation of aknee joint valgus experiment and a meniscus subluxation experiment,the biomechanical nature of the stress and strain were analyzed,and the maximum stress position was judged,this wouldprovideinformation of theoretical basis for soft tissue injury.Method1.Construction of finite element model forknee jointThe MRI tomographic image data of normal human knee joints were selected and imported into MIMICS-20 in DICOM format.In Mimics software,the "3D magnetic lasso(3D LiveWire)" was functionedto build the mask of bony tissue,and the "dynamic regional growth(dynamic region growing)" tool was functioned to build the soft tissue mask.The 3D model of each organwas constructed by "Calculate 3D".Each part of the knee joint model was imported into Geomagic Studio-12.0 by STL format,and a better model was obtained by smoothing,Boolean operation and so on.Hypermesh-14.0 is introduced into the grid division by IGES format.The final model is executed by Abaqus-6.14 in InP format,where assignment of the model material and definition of boundary conditions are carried out.The axial load of 700N is loaded vertically on the femur superiorlyas to simulate human body initially,and the subsequent experimental design is carried out on this basis.2.Knee joint model validationOn the basis of the initial model,the back of the knee was loaded by applying 134N on the front end of the femur to calculate the displacement of the femur and the stress of the anterior cruciate ligament.The results of the model were compared with the other literatures to validate of the model.3.Knee joint valgus testOn the basis of the initial model,the rotation load of 1° to 9°of the femur was loaded respectively,andincreased by 1°each time,totally 9 groups of models were set up to simulate different angles of the knee joint.The stress distribution and changes of medial collateral ligament and the gapof the medial knee joint(mm)were analyzed.4.The Meniscus subluxation experimentThe meniscus subluxation model is constructed by changing the X axis displacement of the meniscus.In addition to the finite element model of the knee joint,4 3D-models were established according to the displacement of the meniscus subluxation(from 1mm to 3mm,1 mm per model).The stress magnitude and distribution of the medial and lateral meniscus,the femoral cartilage and tibial cartilage in the medial meniscus subluxation of knee joint were calculated and analyzed.Result1.The 3D model of the knee joint was successfully constructed,including the femur,tibia,femur cartilage,tibial cartilage,anterior cruciate ligament,posterior cruciate ligament,medial collateral ligament,lateral collateral ligament and medial meniscus,and lateral meniscus.2.The results of the finite element model validation showed that the posterior displacement of the femur was 21,42mm,and the maximum stress of the anterior cruciate ligament was 27.3Mpa.By comparison with the results of the correlation studies,the results are similar,and the stress distribution trend is consistent.Therefore,the validity of the finite element model of knee joint can be verified.The results of ectropion experiment:the stress of medial collateral ligament(MCL)was concentrated at the attachmentpoint to the bony tissue.With the increase of the angle,the stress of medial collateral ligament increased gradually.When the knee joint valgus was 1°～5°,the extension of the medial gap<3mm is classified as Idegree injury;when ectropion reaches 6°～8°,the degree of the medial gapis 3-5mm,is classified as MCL injury Ildegree;when the knee joint is more than 8 degrees,the degree of the medial gap>5mm is classified MCL injuryllldegree.3.The experimental results of meniscus subluxation:With the increase of the medial meniscus dislocation,the stress of each part increased gradually,the stress of the femur cartilage and the lateral meniscus changed little.The stress of the tibial cartilage and the medial meniscus increased obviously when the medial meniscus displacement was 3mm.Conclusion1.The simulativeexperiment of knee valgus presented,that the junction between the medial collateral ligament and the femur arethus considered to be the most vulnerable.When the valgus is greater than 8°,the medial collateral ligament injuryis severe enough for operation.2.During the meniscus subluxation experiments,When the displacement value of medial meniscus reached 3mm,the wear of meniscus and cartilage could be accelerated.In clinical diagnosis and treatment,MRI examination should be carried out as early as possible to confirm the wear of meniscus and corresponding treatment.