Objective： To study the stress distribution of the femoral hip prosthesis after the hip joint replacement. Methods： After the hip joint replacement, when the fenmr and prosthesis are considered as concentric cylinde...Objective： To study the stress distribution of the femoral hip prosthesis after the hip joint replacement. Methods： After the hip joint replacement, when the fenmr and prosthesis are considered as concentric cylinders with perfectly banded interface, a relatively perfect theoretical model of simulating the interracial stress transfer is established. Results： The maximum interfaeial shear stress oeeured at Z=O. 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, interracial stress must remain constant and balanced with the pressure load at Z=O. The radius of the femoral hip prosthesis changed with interfacial shear stress. The maximum value of the radius occured at Z=O, then it decreased at m. Specially, a=18.2 mm at Z=10 ram, a=5.36 mm at Z=98 ram, 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 study whether the range of knee flexion （ROF） is affected by geometrical mismatch of the femoral component and the resultant change in the pos- terior condylar offset （PCO） after high-flexion poster...Objective： To study whether the range of knee flexion （ROF） is affected by geometrical mismatch of the femoral component and the resultant change in the pos- terior condylar offset （PCO） after high-flexion posterior-sta- bilized total knee arthroplasty （TKA）. Methods： One hundred osteoarthritic patients （50 males and 50 females） underwent femoral osteotomy by the ante- rior referencing technique. The PCO for each patient was measured from lateral radiographs before, during and 2 years after TKA. The thickness of the joint cartilage was mea- sured by magnetic resonance imaging before TKA and added onto the radiographic measurement. The relationship between changes in the PCO and improvements in the ROF before, during and 2 years after TKA were statistically analyzed. Results： Compared with the preoperative value, the PCO was reduced by （3.45±3.28） mm after TKA, with a significantly larger reduction observed in female patients than male patients （P〈0.05）. When examining the subject popu- lation as a whole, there was a significant positive correla- tion between PCO and ROF improvement during TKA （P〈 0.05）, but this improvement was not maintained 2 years after TKA （P〉0.05）. However, when male and female patients were analyzed separately, there was a significant positive correlation between PCO change and ROF improvement for both sexes at both time points （all P〈0.05）. Conclusions： Restoration of PCO plays an important role in the optimization of knee flexion even after posteriorstabilized TKA. Femoral components based on Caucasian anatomic characteristics could not match the native anatomy of distal femurs in Chinese population especially female Chinese. Rotated resection of distal femur with anterior referencing technique usually leads to a decreased PCO and therefore reduces maximal obtainable flexion.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 fenmr and prosthesis are considered as concentric cylinders with perfectly banded interface, a relatively perfect theoretical model of simulating the interracial stress transfer is established. Results： The maximum interfaeial shear stress oeeured at Z=O. 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, interracial stress must remain constant and balanced with the pressure load at Z=O. The radius of the femoral hip prosthesis changed with interfacial shear stress. The maximum value of the radius occured at Z=O, then it decreased at m. Specially, a=18.2 mm at Z=10 ram, a=5.36 mm at Z=98 ram, 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 study whether the range of knee flexion （ROF） is affected by geometrical mismatch of the femoral component and the resultant change in the pos- terior condylar offset （PCO） after high-flexion posterior-sta- bilized total knee arthroplasty （TKA）. Methods： One hundred osteoarthritic patients （50 males and 50 females） underwent femoral osteotomy by the ante- rior referencing technique. The PCO for each patient was measured from lateral radiographs before, during and 2 years after TKA. The thickness of the joint cartilage was mea- sured by magnetic resonance imaging before TKA and added onto the radiographic measurement. The relationship between changes in the PCO and improvements in the ROF before, during and 2 years after TKA were statistically analyzed. Results： Compared with the preoperative value, the PCO was reduced by （3.45±3.28） mm after TKA, with a significantly larger reduction observed in female patients than male patients （P〈0.05）. When examining the subject popu- lation as a whole, there was a significant positive correla- tion between PCO and ROF improvement during TKA （P〈 0.05）, but this improvement was not maintained 2 years after TKA （P〉0.05）. However, when male and female patients were analyzed separately, there was a significant positive correlation between PCO change and ROF improvement for both sexes at both time points （all P〈0.05）. Conclusions： Restoration of PCO plays an important role in the optimization of knee flexion even after posteriorstabilized TKA. Femoral components based on Caucasian anatomic characteristics could not match the native anatomy of distal femurs in Chinese population especially female Chinese. Rotated resection of distal femur with anterior referencing technique usually leads to a decreased PCO and therefore reduces maximal obtainable flexion.
