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
目的探讨老年国人股骨近端生物力学特点以及股骨粗隆间骨折内固定方式的选择。方法选取老年国人尸体股骨标本64根,在环股骨颈基底部、环股骨粗隆间、环股骨小粗隆基底部表面选取力学测量标志点,测量0.5、1.0、1.5、2.0、2.5 k N压应力...目的探讨老年国人股骨近端生物力学特点以及股骨粗隆间骨折内固定方式的选择。方法选取老年国人尸体股骨标本64根,在环股骨颈基底部、环股骨粗隆间、环股骨小粗隆基底部表面选取力学测量标志点,测量0.5、1.0、1.5、2.0、2.5 k N压应力下的应力值。制作股骨粗隆间骨折(Evans-Jensen分型)PFNA和LCP内固定模型,PFNA组在螺旋刀片前段上方定位M点,在螺旋刀片和主钉连接位置上方定位P点;LCP组在股骨头内最上方螺钉前段上方定位M点,在螺钉和钢板结合部定位P点;测量0.5、1.0、1.5、2.0 k N压应力下的M点及P点的应力值。结果老年国人环股骨颈基底部、环股骨粗隆间、环股骨小粗隆基底部表面的应力值随着压应力增加而增加,M点与P点的应力值均随着压应力的增加而增加,差异有统计学意义(P<0.05)。相同压应力下,PFNA组Ⅱ型与Ⅲ型骨折M点应力值差异无统计学意义(P>0.05),而Ⅳ型骨折应力值大于Ⅲ型骨折,Ⅴ型骨折大于Ⅳ型骨折。在0.5、1.0 k N压应力下,PFNA组Ⅱ型与Ⅲ型骨折P点应力值差异无统计学意义(P>0.05);在1.5、2.0 k N压应力下,PFNA组Ⅲ型骨折P点应力值大于Ⅱ型骨折(P<0.05)。相同压应力下,PFNA组Ⅳ型骨折P点应力值大于Ⅲ型骨折,Ⅴ型骨折大于Ⅳ型骨折。相同压应力下,LCP组Ⅲ型骨折M点、P点应力值大于Ⅱ型骨折,Ⅳ型骨折大于Ⅲ型骨折,Ⅴ型骨折大于Ⅳ型骨折。结论老年股骨粗隆间骨折可根据Evans-Jensen分型选择合理的内固方式,而术中恢复内、外侧骨皮质的连续性对维持良好应力传导、避免内固定失败有重要作用。展开更多
Background Ceramic bearing surfaces have been introduced to prevent osteolysis after total hip arthroplasty （THA）,but little is known about the difference in clinical and radiological results between pure alumina an...Background Ceramic bearing surfaces have been introduced to prevent osteolysis after total hip arthroplasty （THA）,but little is known about the difference in clinical and radiological results between pure alumina and sandwich alumina bearings.The purpose of this study was to analyze the results obtained with third-generation alumina-on-alumina THA with two different designs both in liner and femoral stem fixation after a minimum follow-up of 4.2 years.Methods The results of 195 primary alumina-on-alumina THAs in 167 patients were evaluated.The procedures were performed between January 1998 and October 2006.Three patients died and 11 patients were lost to follow-up,leaving a total of 153 patients （181 hips） available for study.In the 88 group A patients,107 hips were implanted using pure alumina bearings with cementless femoral stems.These patients were followed for （6.84±1.49） years.In the 65 group B patients,74 hips were implanted using sandwich alumina ceramic bearings with cemented femoral stems.These patients had a follow-up period of （7.73±1.60） years.Patients in both groups were evaluated clinically and radiographically.Results One ceramic liner fracture occurred in group A and five took place in group B （P 〈0.05）,four of them revised for liner fracture.In each group,one acetabular shell migration happened without liner breakage and two hips developed deep infections,and all these six hips received revisions.Nine femoral components loosened in group B,with seven undergoing revisions.Kaplan-Meier survivorship at 5 years for revision of any component for any reason in group A was 96.26% compared to 90.54% in group B （P 〈0.05）.Better function was determined in group A （average Harris hip scores：92.13±2.85） than in group B （average Harris hip scores：86.03±4.21） and the difference was significant （P 〈0.05）.Squeaking was not recorded in either group.Conclusions The sandwich design of the acetabular bearings can not reduce the migration rate in ceramic bearings but increase the liner fracture rate compared to pure ceramic liners.The high loosening rate in fluted and taped designed cemented stems with sandwich liners warrant caution to their use.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.
文摘目的探讨老年国人股骨近端生物力学特点以及股骨粗隆间骨折内固定方式的选择。方法选取老年国人尸体股骨标本64根,在环股骨颈基底部、环股骨粗隆间、环股骨小粗隆基底部表面选取力学测量标志点,测量0.5、1.0、1.5、2.0、2.5 k N压应力下的应力值。制作股骨粗隆间骨折(Evans-Jensen分型)PFNA和LCP内固定模型,PFNA组在螺旋刀片前段上方定位M点,在螺旋刀片和主钉连接位置上方定位P点;LCP组在股骨头内最上方螺钉前段上方定位M点,在螺钉和钢板结合部定位P点;测量0.5、1.0、1.5、2.0 k N压应力下的M点及P点的应力值。结果老年国人环股骨颈基底部、环股骨粗隆间、环股骨小粗隆基底部表面的应力值随着压应力增加而增加,M点与P点的应力值均随着压应力的增加而增加,差异有统计学意义(P<0.05)。相同压应力下,PFNA组Ⅱ型与Ⅲ型骨折M点应力值差异无统计学意义(P>0.05),而Ⅳ型骨折应力值大于Ⅲ型骨折,Ⅴ型骨折大于Ⅳ型骨折。在0.5、1.0 k N压应力下,PFNA组Ⅱ型与Ⅲ型骨折P点应力值差异无统计学意义(P>0.05);在1.5、2.0 k N压应力下,PFNA组Ⅲ型骨折P点应力值大于Ⅱ型骨折(P<0.05)。相同压应力下,PFNA组Ⅳ型骨折P点应力值大于Ⅲ型骨折,Ⅴ型骨折大于Ⅳ型骨折。相同压应力下,LCP组Ⅲ型骨折M点、P点应力值大于Ⅱ型骨折,Ⅳ型骨折大于Ⅲ型骨折,Ⅴ型骨折大于Ⅳ型骨折。结论老年股骨粗隆间骨折可根据Evans-Jensen分型选择合理的内固方式,而术中恢复内、外侧骨皮质的连续性对维持良好应力传导、避免内固定失败有重要作用。
文摘Background Ceramic bearing surfaces have been introduced to prevent osteolysis after total hip arthroplasty （THA）,but little is known about the difference in clinical and radiological results between pure alumina and sandwich alumina bearings.The purpose of this study was to analyze the results obtained with third-generation alumina-on-alumina THA with two different designs both in liner and femoral stem fixation after a minimum follow-up of 4.2 years.Methods The results of 195 primary alumina-on-alumina THAs in 167 patients were evaluated.The procedures were performed between January 1998 and October 2006.Three patients died and 11 patients were lost to follow-up,leaving a total of 153 patients （181 hips） available for study.In the 88 group A patients,107 hips were implanted using pure alumina bearings with cementless femoral stems.These patients were followed for （6.84±1.49） years.In the 65 group B patients,74 hips were implanted using sandwich alumina ceramic bearings with cemented femoral stems.These patients had a follow-up period of （7.73±1.60） years.Patients in both groups were evaluated clinically and radiographically.Results One ceramic liner fracture occurred in group A and five took place in group B （P 〈0.05）,four of them revised for liner fracture.In each group,one acetabular shell migration happened without liner breakage and two hips developed deep infections,and all these six hips received revisions.Nine femoral components loosened in group B,with seven undergoing revisions.Kaplan-Meier survivorship at 5 years for revision of any component for any reason in group A was 96.26% compared to 90.54% in group B （P 〈0.05）.Better function was determined in group A （average Harris hip scores：92.13±2.85） than in group B （average Harris hip scores：86.03±4.21） and the difference was significant （P 〈0.05）.Squeaking was not recorded in either group.Conclusions The sandwich design of the acetabular bearings can not reduce the migration rate in ceramic bearings but increase the liner fracture rate compared to pure ceramic liners.The high loosening rate in fluted and taped designed cemented stems with sandwich liners warrant caution to their use.
