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 cem...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-6A1-4V 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
目的建立健康志愿者、髋关节发育不良(development dysplasia of the hip,DDH)患者手术前后股骨-骨盆-腰椎模型,研究弧形髋臼截骨术对腰椎生物力学影响。方法利用CT扫描获取4名DDH患者手术前后以及1名健康志愿者股骨-骨盆-腰椎DICOM数据...目的建立健康志愿者、髋关节发育不良(development dysplasia of the hip,DDH)患者手术前后股骨-骨盆-腰椎模型,研究弧形髋臼截骨术对腰椎生物力学影响。方法利用CT扫描获取4名DDH患者手术前后以及1名健康志愿者股骨-骨盆-腰椎DICOM数据,构建三维有限元模型。在Geomagic中采用偏移命令划分皮质骨与松质骨,在SolidWorks中添加腰椎软骨、骶髂关节、耻骨联合等软骨,在ANASYS中对模型进行有限元分析,步态为慢走中的单腿支撑中期相。分析对比DDH患者手术前后腰椎生物力学变化,将患者术后腰椎生物力学数据与健康志愿者进行对比。结果建立了4组患者和1组健康志愿者股骨-骨盆-腰椎模型,模型在各工况下结果均在所参考的文献范围内,证明模型有效。患者术后腰椎、股骨颈、纤维环与髓核所受应力远小于患者术前的状态,患者术后腰椎、股骨颈、纤维环与髓核所受应力与健康志愿者相近。结论弧形髋臼截骨术在治疗DDH后会显著降低腰椎、椎间盘所受应力,纤维环与髓核受力也更加均匀,说明弧形髋臼截骨术会将患者调整到健康状态。研究结果为临床治疗DDH提供了生物力学依据,有助于优化手术方案。展开更多
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-6A1-4V 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.
文摘目的建立健康志愿者、髋关节发育不良(development dysplasia of the hip,DDH)患者手术前后股骨-骨盆-腰椎模型,研究弧形髋臼截骨术对腰椎生物力学影响。方法利用CT扫描获取4名DDH患者手术前后以及1名健康志愿者股骨-骨盆-腰椎DICOM数据,构建三维有限元模型。在Geomagic中采用偏移命令划分皮质骨与松质骨,在SolidWorks中添加腰椎软骨、骶髂关节、耻骨联合等软骨,在ANASYS中对模型进行有限元分析,步态为慢走中的单腿支撑中期相。分析对比DDH患者手术前后腰椎生物力学变化,将患者术后腰椎生物力学数据与健康志愿者进行对比。结果建立了4组患者和1组健康志愿者股骨-骨盆-腰椎模型,模型在各工况下结果均在所参考的文献范围内,证明模型有效。患者术后腰椎、股骨颈、纤维环与髓核所受应力远小于患者术前的状态,患者术后腰椎、股骨颈、纤维环与髓核所受应力与健康志愿者相近。结论弧形髋臼截骨术在治疗DDH后会显著降低腰椎、椎间盘所受应力,纤维环与髓核受力也更加均匀,说明弧形髋臼截骨术会将患者调整到健康状态。研究结果为临床治疗DDH提供了生物力学依据,有助于优化手术方案。
