Background The acetabular teardrop is often used to guide acetabular component placement in total hip arthroplasty （THA）.Placing the lower acetabular component aspect at the same level as the lower teardrop edge was...Background The acetabular teardrop is often used to guide acetabular component placement in total hip arthroplasty （THA）.Placing the lower acetabular component aspect at the same level as the lower teardrop edge was assumed to restore the hip center of rotation.Here we radiographically analyzed the relationship between cup center and normal contralateral acetabulum center height on unilateral THA using this placement method.Methods A total of 106 unilateral THA cases with normal contralateral acetabula were reviewed and the vertical and horizontal distances in relation to the lower acetabular teardrop edge from both hip joint centers,cup inclination,and anteversion were measured radiographically.The paired t-test was used to compare left and right hip center heights.Scatter plots and Pearson＇s correlation coefficients were used to evaluate differences in hip center heights,cup anteversion,inclination angles,and medialized cup center distance compared to the contralateral hip joint.Results Cup center height was significantly greater （P ＜0.01） than contralateral hip joint center height （93.4％ in the 0-5 mm range,6.6％ ＞5 mm）.There was a weak correlation between hip center height difference and inclination （r=0.376,P ＜0.01） and between difference and anteversion （r=0.310,P ＜0.01） but no correlation between difference and outer cup diameter （r=0.184,P=0.058） or difference and medialized cup center distance （r＝-0.098,P=0.318）.Conclusions Although this method did not exactly replicate anatomic hip center height,the clinical significance of cup center height and anatomic hip center height differences is negligible.This acetabular component placement method has high simplicity,reliability,and stability.展开更多
Firstly, in view of the respective defects of existing self-centering devices for vehicle suspension height, the design scheme of the proposed mechanical self-centering device for suspension height is described. Takin...Firstly, in view of the respective defects of existing self-centering devices for vehicle suspension height, the design scheme of the proposed mechanical self-centering device for suspension height is described. Taking the rear suspension of a certain light bus as a research example, the structures and parameters of the novel device are designed and ascertained. Then, the road excitation models, the performance evaluation indexes and the half-vehicle model are built, the simulation outputs of time and frequency domain are obtained with the road excitations of random and pulse by using MATLAB/Simulink software. So the main characteristics of the self-centering suspension are presented preliminarily. Finally, a multi-objective parameter design optimization model for the self-centering device is built by weighted sum approach, and optimal solution is obtained by adopting complex approach. The relevant choosing-type parameters for self-centering device components are deduced by using discrete variable optimal method, and the optimal results are verified and analyzed. So the performance potentials of the self-centering device are exerted fully in condition of ensuring overall suspension performances.展开更多
文摘Background The acetabular teardrop is often used to guide acetabular component placement in total hip arthroplasty （THA）.Placing the lower acetabular component aspect at the same level as the lower teardrop edge was assumed to restore the hip center of rotation.Here we radiographically analyzed the relationship between cup center and normal contralateral acetabulum center height on unilateral THA using this placement method.Methods A total of 106 unilateral THA cases with normal contralateral acetabula were reviewed and the vertical and horizontal distances in relation to the lower acetabular teardrop edge from both hip joint centers,cup inclination,and anteversion were measured radiographically.The paired t-test was used to compare left and right hip center heights.Scatter plots and Pearson＇s correlation coefficients were used to evaluate differences in hip center heights,cup anteversion,inclination angles,and medialized cup center distance compared to the contralateral hip joint.Results Cup center height was significantly greater （P ＜0.01） than contralateral hip joint center height （93.4％ in the 0-5 mm range,6.6％ ＞5 mm）.There was a weak correlation between hip center height difference and inclination （r=0.376,P ＜0.01） and between difference and anteversion （r=0.310,P ＜0.01） but no correlation between difference and outer cup diameter （r=0.184,P=0.058） or difference and medialized cup center distance （r＝-0.098,P=0.318）.Conclusions Although this method did not exactly replicate anatomic hip center height,the clinical significance of cup center height and anatomic hip center height differences is negligible.This acetabular component placement method has high simplicity,reliability,and stability.
基金supported by Youth Technological Phosphor Project of Shanghai City (No.04QMX1474).
文摘Firstly, in view of the respective defects of existing self-centering devices for vehicle suspension height, the design scheme of the proposed mechanical self-centering device for suspension height is described. Taking the rear suspension of a certain light bus as a research example, the structures and parameters of the novel device are designed and ascertained. Then, the road excitation models, the performance evaluation indexes and the half-vehicle model are built, the simulation outputs of time and frequency domain are obtained with the road excitations of random and pulse by using MATLAB/Simulink software. So the main characteristics of the self-centering suspension are presented preliminarily. Finally, a multi-objective parameter design optimization model for the self-centering device is built by weighted sum approach, and optimal solution is obtained by adopting complex approach. The relevant choosing-type parameters for self-centering device components are deduced by using discrete variable optimal method, and the optimal results are verified and analyzed. So the performance potentials of the self-centering device are exerted fully in condition of ensuring overall suspension performances.
