Objective:To study the stress distribution of the femoral hip prosthesis after the hip joint replacement.Methods:After the hip joint replacement,when the femur and prosthesis are considered as concentric cylinders wit...Objective:To study the stress distribution of the femoral hip prosthesis after the hip joint replacement.Methods:After the hip joint replacement,when the femur and prosthesis are considered as concentric cylinders with perfectly banded interface,a relatively perfect theoretical model of simulating the interfacial stress transfer is established.Results:The maximum interfacial shear stress occured at Z=0.At the cross-section of the femoral neck,interfacial shear stress decreased exponentially with the increases of the Z.Shear stress became very small at Z>0.1 m,which meant that the shear stress at the far end of the femoral hip prosthesis was very small.In order to avoid the stress concentration and femoral hip prosthesis sinking,interfacial stress must remain constant and balanced with the pressure load at Z=0.The radius of the femoral hip prosthesis changed with interfacial shear stress.The maximum value of the radius occured at Z=0,then it decreased at m.Specially,a=18.2 mm at Z=10 mm,a=5.36 mm at Z=98 mm,these are ideal radius.Conclusion:A theoretical model of simulating the interfacial stress is established when the femur and prosthesis are considered as concentric cylinders.The distributions of the interfacial shear and radial stresses with the axial positions are obtained.A theoretical reference for the design of the prosthesis is provided.展开更多
Objective:To model the stress transfer at the interface of the cemented prosthesis and femur,an axisymmetric model of the interfacial stress transfer was established.Methods: Assuming that the prosthesis,the cement an...Objective:To model the stress transfer at the interface of the cemented prosthesis and femur,an axisymmetric model of the interfacial stress transfer was established.Methods: Assuming that the prosthesis,the cement and the femur were concentric cylinders with linear elastic and isotropic properties,distributions of the axial stresses in the prosthesis,the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction were obtained from the established axisymmetric stress transfer model.Results: Interfacial failure was the main form for the prosthesis/cement/femur structure under external loads. Considering the residual thermal stresses,it was more likely to produce the mixed failure form than the pure shear failure form. Since the cement had a relatively high thermal expansion coefficient,the thermal effect accelerated the interface failure and thus aggravated the stress shielding effect. Due to a relatively high thermal residual temperature difference,the interfacial debonding and femur failure was more likely to occur for the cobalt-chromium alloy prosthesis material than the Ti-6Al-4V alloy prosthesis material.Conclusion: Assuming that the prosthesis,the cement and the femur are concentric cylinders with linear elastic and isotropic properties,distributions of the axial stresses in the prosthesis,the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction was obtained using the basic equations of axisymmetric elastic mechanics when the prosthesis bears the compressive stresses. Interface failure is the main failure form for the prosthesis/cement/femur structure under external loads. The thermal effects accelerate the failure of the prosthesis/cement interface and the cement/femur interface and the relaxation of the prosthesis,and then aggravates the stress shielding effect of the femur. Also,the thermal effects decrease the efficiencies of the interfacial stress transfer to some extent since it alleviates the failure of the interface and the femur,which was confirmed by the clinical results.展开更多
Objective: The biomechanical characters of the bone fracture of the man femoral hip joint under impact loads are explored. Methods:A biosystem model of the man femoral hip joint by using the GE (General Electric) ligh...Objective: The biomechanical characters of the bone fracture of the man femoral hip joint under impact loads are explored. Methods:A biosystem model of the man femoral hip joint by using the GE (General Electric) lightspeed multi-lay spiral CT is conducted. A 3D finite element model is established by employing the finite element software ANSYS. The FE analysis mainly concentrates on the effects of the impact directions arising from intense movements and the parenchyma on the femoral hip joint on the stress distributions of the proximal femur. Results:The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. Conclusion:Effects of the angle δ of the impact load to the anterior direction and the angle γ of the impact load to the femur shaft on the bone fracture are given;δ has larger effect on the stress and strain distributions than the angle γ, which mainly represents the fracture of the upper femur including the femoral neck fracture when the posterolateral femur is impacted, consistent with the clinical results.展开更多
文摘Objective:To study the stress distribution of the femoral hip prosthesis after the hip joint replacement.Methods:After the hip joint replacement,when the femur and prosthesis are considered as concentric cylinders with perfectly banded interface,a relatively perfect theoretical model of simulating the interfacial stress transfer is established.Results:The maximum interfacial shear stress occured at Z=0.At the cross-section of the femoral neck,interfacial shear stress decreased exponentially with the increases of the Z.Shear stress became very small at Z>0.1 m,which meant that the shear stress at the far end of the femoral hip prosthesis was very small.In order to avoid the stress concentration and femoral hip prosthesis sinking,interfacial stress must remain constant and balanced with the pressure load at Z=0.The radius of the femoral hip prosthesis changed with interfacial shear stress.The maximum value of the radius occured at Z=0,then it decreased at m.Specially,a=18.2 mm at Z=10 mm,a=5.36 mm at Z=98 mm,these are ideal radius.Conclusion:A theoretical model of simulating the interfacial stress is established when the femur and prosthesis are considered as concentric cylinders.The distributions of the interfacial shear and radial stresses with the axial positions are obtained.A theoretical reference for the design of the prosthesis is provided.
文摘Objective:To model the stress transfer at the interface of the cemented prosthesis and femur,an axisymmetric model of the interfacial stress transfer was established.Methods: Assuming that the prosthesis,the cement and the femur were concentric cylinders with linear elastic and isotropic properties,distributions of the axial stresses in the prosthesis,the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction were obtained from the established axisymmetric stress transfer model.Results: Interfacial failure was the main form for the prosthesis/cement/femur structure under external loads. Considering the residual thermal stresses,it was more likely to produce the mixed failure form than the pure shear failure form. Since the cement had a relatively high thermal expansion coefficient,the thermal effect accelerated the interface failure and thus aggravated the stress shielding effect. Due to a relatively high thermal residual temperature difference,the interfacial debonding and femur failure was more likely to occur for the cobalt-chromium alloy prosthesis material than the Ti-6Al-4V alloy prosthesis material.Conclusion: Assuming that the prosthesis,the cement and the femur are concentric cylinders with linear elastic and isotropic properties,distributions of the axial stresses in the prosthesis,the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction was obtained using the basic equations of axisymmetric elastic mechanics when the prosthesis bears the compressive stresses. Interface failure is the main failure form for the prosthesis/cement/femur structure under external loads. The thermal effects accelerate the failure of the prosthesis/cement interface and the cement/femur interface and the relaxation of the prosthesis,and then aggravates the stress shielding effect of the femur. Also,the thermal effects decrease the efficiencies of the interfacial stress transfer to some extent since it alleviates the failure of the interface and the femur,which was confirmed by the clinical results.
文摘Objective: The biomechanical characters of the bone fracture of the man femoral hip joint under impact loads are explored. Methods:A biosystem model of the man femoral hip joint by using the GE (General Electric) lightspeed multi-lay spiral CT is conducted. A 3D finite element model is established by employing the finite element software ANSYS. The FE analysis mainly concentrates on the effects of the impact directions arising from intense movements and the parenchyma on the femoral hip joint on the stress distributions of the proximal femur. Results:The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. Conclusion:Effects of the angle δ of the impact load to the anterior direction and the angle γ of the impact load to the femur shaft on the bone fracture are given;δ has larger effect on the stress and strain distributions than the angle γ, which mainly represents the fracture of the upper femur including the femoral neck fracture when the posterolateral femur is impacted, consistent with the clinical results.
