Finite Element Analysis Of Contact Pressure Of Artificial Knee Joint Prosthesis With Different Angles Of Force Lines Aligned

With the aging of the population in society,the incidence of knee osteoarthritis is increasing,So that total knee arthroplasty(TKA)surgery is increasing.In total knee arthroplasty,the angle between the anatomical axis and the mechanical axis of the femur is commonly used as the osteotomy Angle of the distal femur to restore the rectangular "flexion gap" of the knee joint.So as to restore the lower limb mechanical shaft force line.After total knee arthroplasty surgery according to 0° force line,there are also some patients who had postoperative joint pain and discomfort and abnormal wear of joint prosthesis,stress shielding of the bone after TKA,prosthesis loosening prosthesis fracture and other problems.To investigate the biomechanical distribution of lower limb alignment in patients with different angles,and to find out appropriate alignment Angle of lower limb line,so seven different lower limb alignment lines were designed with different pronation angles of lower limbs.The experiment uses the international standard of medical picture data(DICOM),and establishes a preliminary knee joint model through software such as Mimics 19.0and Geomagic wrap 2017.The experiment uses Siemens nx 12.0 to establish different femoral prosthesis distal osteotomy models,then the mock prosthesis assembly to be proceed.The use of different angles of femoral prosthesis valgus osteotomy,resulting in varus or valgus of the lower limbs,Thereby,seven situations of alignment of the lower limbs are formed: at 1°,2°,3°,4°,5°,6°varus,at 1°,2°,3°,4°,5°,6°valgu,and the neutral force line is 0° force line.Meshing different models,assigning attributes,then an axial downward load of F(F=65kg×10N/kg×88%×0.5 = 286 N)is applied to the upper end of the femur.Use finite element analysis to simulate the alignment of different lower limbs to assemble knee prostheses,and to simulate surgical osteotomy and prosthesis assembly.The results show that when the neutral line of force is aligned,equivalent stress on the surface of the tibial prosthesis gasket and the osteotomy surface of the femur,and the stress concentration situation is more balanced inside and outside,the equivalent strain energy of the medial and lateral femoral condyles is more uniform on both sides with no significant decreasing or increasing,evenly distributed on both sides.In the case of varus of the lower limbs,the equivalent stress and stress concentration of the tibial prosthesis gasket and the femoral osteotomy surface appear,which is biased to the medial side.In the case of valgus of the lower limbs,the equivalent stress and stress concentration of the tibial prosthesis gasket and the femoral osteotomy surface appear,deviating to the lateral side.When the lower limbs are turned inward,the equivalent strain energy of the medial and lateral femoral condyle appears unevenly distributed.When the lower limbs are turned inward,the equivalent strain energy of the medial and lateral femoral condyles is very unevenly distributed under the condition of the lower limb force line inversion and valgus.The equivalent strain energy of the medial and lateral femoral condyles will increase when the lower extremity line of force is inverted,and the equivalent strain energy of the medial condyle will increase,while the equivalent strain energy of the lateral condyle will decrease.The equivalent strain energy of the medial and lateral femoral condyles When the lower limbs are valgus,the equivalent strain energy of the medial condyle decreases,and the equivalent strain energy of the lateral condyle increases.Through the experiment,we draw the conclusion:1.Establish a three-dimensional model of the knee joint through medical imaging data and finite element analysis related software,and further establish an orthopedic-related surgery model.This method is simple and easy to obtain and has strong operability.It is a good auxiliary tool for orthopedic research.2.In total knee arthroplasty surgery,neutral alignment is still the best reference index for alignment of lower limbs,is the gold standard for knee surgery in neutral position alignment.The uneven distribution of equivalent stress on the surface of the knee joint prosthesis gasket appears in the internal or external deviation of the lower limb force line,and the stress concentration area is internal or external.When the lower limbs are varus or valgus,the equivalent stress distribution on the osteotomy surface of the distal femur appears uneven,and stress concentration appears.When the force line of the lower limbs is varus or valgus,the equivalent strain energy distribution of the femoral medial and lateral condyles appears unbalanced.The above can easily lead to abnormal wear of the patient’s prosthesis gasket,knee joint pain,stress shielding,bone remodeling,osteoporosis,and fractures around the prosthesis.