RESUMO
Objective To investigate ISO 7206 standard used as a guidance for clinical selection of total hip prosthesis. Methods Kinematics and dynamics process of normal walking gait was simulated by establishing a numerical musculoskeletal model; the corresponding finite element model of total hip prosthesis was constructed, and gait loads were applied to calculate stress distribution on prosthesis, which were compared with that on ISO finite element model. ResultsPeaks of hip joint reaction forces were achieved at 20% gait and 54% gait during normal walking gait, which were used as gait loads for finite element simulation, and the results showed that the maximum Von Mises stress of prosthesis was reached at 20% gait. The maximum Von Mises stress of prosthesis in loosening model was higher than that in non-loosening model, and some differences existed in the distribution pattern. The maximum stresses of prosthesis both under ISO loads and gait loads by different body weights were analyzed and compared, and the maximum stress of prosthesis under ISO loads was equivalent to that under gait loads by body weight between 108 kg and 142 kg. ConclusionsThe prosthesis that passed ISO test can meet the strength requirement for normal gait loads of 100 kg body weight.
RESUMO
Objective To investigate the effect of mechanical properties of anterior cruciate ligament (ACL) on finite element simulation of knee joint. MethodsA three-dimensional finite element model of knee joint including all the main tissues was reconstructed based on medical images, and the transverse isotropic hyperelasticity of ligament was considered as well. Three groups of ACL material property parameters were acquired by fitting three different experimental stress strain curves based on the same ligament constitutive equation, to compare the influence of different ACL mechanical parameters on the kinematic and biomechanical properties of knee joint. Results Different ACL mechanical properties resulted in different displacements in knee joint. With the change of ACL mechanical properties, the stress and principal strain in ACL changed a lot, while the trend of their distributions were basically the same. Conclusions The selection of different ACL experimental stress-strain curves can influence the simulating result of the finite element analysis. More attention should be paid to the determination of ACL mechanical properties, the reconstruction and validation for the finite element model of knee joint.