Biomechanics Characteristic Research Of Human Lower Limb Joint System

The most important part of human body is the lower limb,which is the main support in the human movement. There are many pathological joint mechanics osteoarthritis and accidental damage which affect the daily grind. Joint replacement is the final method to cure severe arthropathy. But the situations like asepsis loosing, prostheses break and osteolysis destroy the recuperate outlook of patient and the doctor can not solve these problems. This is the scientific research trying to find out the reasons of prostheses disabled and prostheses design based on the biomechanical theory. This paper makes some research on this aspect and gets some useful data. The first step, develop the mathematics modeling of human lower limb and calculate the kinematics parameters. Measure the human lower limb gait cycle data by NDI's Optotrak Certus system. It is important to get the DICOM images in order to create mechanical model of human lower limb. The lower limb system model should be developped by inverse engineer theory based on images data. The clinic total hip replacement (THR) is created with charnly prostheses. All the models opened in the finite element software and get the mechanical charactertics data. The analysis conclusion has the useful results directing the prostheses design and clinic operation.Some conclusions were obtained according the experimental and theoretical researching, as below:The displacement function can be got based on the anthropometry through 15 marks paste on the connor body. The angle velocity and angle acceleration are obtained through Euler angle transformation. Human lower limb dynamic equations can be got through Lagrange and Hamilton theory.The Optotrak Certus system that made in NDI company is used in motion experiment. The conner consists of healthy body and implanted body. Markers should be pasted on the human body in order to get the gait data under the same criterion. During the gait cycle, the conners do the same action with sneaker and bare foot. It has been shown that implanted patient has the different gait curve with healthy body and the joint deformation magnitude bigger than healthy body's. The conner with sneaker has much less joint deformation magnitude than bare one. It has been known that the joint cartilage has the important function in decreasing the impact loading.Create the model that can be used to calculate the stress and deformation is the key step. The human lower limb anatomy data can be got through CT scan. The human lower limb skeleton map will create from DICOM image data by professional software based on inverse engineering theory. The model consists of lower limb skeleton and joint cartilage. The Charnley hip prosthesis is assemble with femur under simulation operation.Joint replacement is a useful operation to avoid ache from patient for the severity arthropathy. But joint ache, asepsis loosing, prostheses break and osteolysis could appear after operation that can induce the operation destruction. The stress distribution and deformation magnitude of replacement part are the important data to understand the reasons causing the operation destruction. The finite element method (FEM) is the effective tool to get this information. Open the models in the FEM software and mesh the grid with 10 nodes four areas solid element. Create the contact pairs in joint, set the boundary condition and loading based on different motion. Some results as follow are shown after finite element calculation. The stress assemble in implanted part and stress value increase after operation; Bone cement fixation type has lower stress value than biology fixation type that is wonderful to prevent artificial joint loosing caused by osteolysis; Impact loading has more affection than static loading and destroy position comprise femur neck and shaft of femur near lesser trochanter.