骨表面再造数值模拟在人工股骨头假体优化设计中的应用

人工股骨头假体植入技术目前存在的主要问题之一是植入假体存在远期松动等并发症,从而导致手术失败.对于引起松动的主要原因,通常人们认为是磨损碎屑和应力遮挡所造成的骨质吸收.因此,对人工股骨头假体植入物的结构进行优化是具有特别重要的意义.本文采用骨再造理论与有限元结合的方法,用计算机模拟人工股骨头假体植入后股骨的再造行为,用截面吸收率和抗弯截面模量损失率定量分析假体所产生的应力遮挡效应.骨再造理论采用应变能密度作控制变量的表面再造理论,有限单元采用二十节点等参数单元.结果表明在所讨论的假体模型中,三种围领形式的假体所产生的骨吸收仅相差4%.三种长度直柄的假体所产生的骨吸收相差近30%,直柄长度的变化对应力遮挡效应有更显著的影响.     

人工股骨置换术后股骨再造预测

以骨截面面积吸收率和抗弯截面模量损失率反应力遮挡效应，采用骨再造理论和有限元(Finite element，FEM)相结合的方法，用计算机模拟人工股骨植换术后股骨的再造行为，从而定量的分析人工股骨头对股骨的应力遮挡效应。骨表面再造采用BRSS97程序。有限元模型采用正常股骨的受力状态为模型一，带颈领的人工股骨头骨水泥固定骨受力状态为模型二。结果表明，人工股骨头对骨产生的应力遮挡，股骨发生骨吸收，人工假体柄中段近端区域骨吸收严重。其骨截面积吸收最大，其截面吸收率最大为31．33％，抗弯截面模量损失率最大为54．58％。     

三面固定槽形加压钢板内固定后股骨表面再造模拟

采用骨再造理论和有限元相结合的方法，用计算机模拟钢板植入后骨的现地造行为，从而定量的分析了钢板对骨的应力遮挡效应。骨再造理论采用Ｃｏｗｉｎ应变适应性弹性理论，有限单元采用狼节点六面全的等参数单元。     

全髋关节置换术对股骨近端骨重建的影响

目的 采用Wolff骨重建理论分析全髋关节置换（total hip arthroplasty,THA）对股骨近端骨重建进程的影响。方法 根据骨重建控制方程,利用Python语言编写骨重建程序。在ABAQUS软件中分别建立术前股骨模型与术后股骨及假体有限元模型。对比THA手术前后骨重建进程,分析假体植入对THA术后中远期股骨力学性能的影响。结果 假体植入后,股骨近端应力持续降低,受力点由股骨头转移到假体,出现明显的应力遮挡现象。应力遮挡区域内骨丢失现象严重。股骨干皮质骨变薄,应力遮挡有所缓解。假体底端内侧受挤压,应力显著高于外侧,此处骨质分布不均。结论 THA术后股骨近端内侧出现明显的应力遮挡,导致骨丢失,造成假体松动;假体底端两侧应力水平存在差异,引起骨质分布不均,导致假体与股骨配合不紧密,造成术后患者大腿中段的疼痛。     

股骨-关节假体之间的界面生物力学分析

骨是一种结缔组织,它既像钢一样坚硬,又像铝一样轻,是典型的层状梯度功能材料.骨的组分结构完全是由其功能决定的近于完美的一种构造.股骨其空心管型层状结构能适应各种不同姿态的人体负荷功能要求.人工假体植入后改变了股骨干的应力分布,不可避免地产生应力遮挡.运用非均质材料弯曲和扭转理论定量分析了单足站立相及坐位起立时股骨干在假体植入前、后的应力分布情况.比较了钴铬钼合金、钛合金、碳纤维聚砜(CRF/PSF)复合材料假体在股骨干峡部横截面的应力分布情况.由于股骨-假体界面两边材料性能不同,产生的较大应力差异可导致界面松动、剥离和损坏.不同假体的弹性模量不同,产生应力遮挡的程度不同.复合材料假体植入后界面两边应力差异最小,应力遮挡率最低.羟磷灰石表面涂层假体能缓和界面层的应力差异.     

分体螺旋式人工股骨头置换后应力分析的对比性研究

目的：论证分体螺旋式人工股骨头置换的合理性。是否符合生物力学原理。方法：利用９具新鲜成入股骨标本,用三种不同人工髋置换后进行实验应力分析和比较。结果：证明分体螺旋式人工股骨头在应力分布、界面应力、应力遮挡车、初始微动等生物力学特性上优于珍珠面假体和钢制人工髋。结论：分体螺旋式人工骨头置换后应力分布合理,固定牢固,具有高度稳定性。     

分体螺旋式人工股骨头置换后应力分析的对比性研究

目的：论证分体螺旋式人工股骨头置换的合理性。是否符合生物力学原理。方法：利用９具新鲜成入股骨标本,用三种不同人工髋置换后进行实验应力分析和比较。结果：证明分体螺旋式人工股骨头在应力分布、界面应力、应力遮挡车、初始微动等生物力学特性上优于珍珠面假体和钢制人工髋。结论：分体螺旋式人工骨头置换后应力分布合理,固定牢固,具有高度稳定性。     

股骨—人工假体之间的界面生物力学分析

目的 对股骨-人工假体之间的界面生物力学进行分析。方法 应用非均质层状材料弯曲和扭转理论计算模型，定量分析了单足站立相及坐位起立时股骨干在不同假体植入前、后的应力分布情况。结果 由于股骨-假体界面两边材料性能不同，产生的较大应力差异是引起界面松动、剥离和损坏的生物力学原因。不同假体的弹性模量不同，产生应力遮挡的程度不同。结论 复合材料假体植入后应力遮挡率最低。羟磷灰石表面涂层假体能缓和界面层的应力差异。     

一种股骨头假体个性化设计方法研究

为解决人工髋关节置换手术后假体无菌松动等并发症,适应假体个性化快速设计和制造的需求,对假体设计方法进行研究.采用医用CT技术、计算机辅助设计和有限元计算分析相结合的方法,依据患者股骨髓腔解剖形状和置换要求设计髋关节假体;用有限元软件ANSYS建立股骨的三维有限元模型,并自主开发计算机程序计算得到股骨的材料参数,在股骨有限元模型中实现股骨材料的非均匀及各向异性描述;用计算机仿真植入了定制髋假体的股骨--假体系统后的接触问题;分析对比股骨在术前术后的应力、应变大小及分布,检验假体设计的合理性;定量地确定股骨在手术后所产生的应力遮挡效应的程度,研究结果表明这种假体设计和分析方法更为合理、可靠,为优化设计假体和评估假体植入后的长期稳定性提供了基本方法.     

影响THA术后股骨近端应力遮挡大小的因素

全髋关节置换术(THA)术后股骨近端的应力遮挡效应是引起假体周围骨丢失的原因之一,在骨水泥和非骨水泥假体中都存在这一现象[1,2],骨丢失可能会引起股骨假体机械性失败、假体松动、假体周围骨折、翻修手术难度增加等一系列的问题[2],因此研究如何减少应力遮挡效应有重要意义.……     

全髋关节置换术中压电股骨重建的边光滑有限元分析

目的 针对传统有限元法(finite element method, FEM)分析全髋关节置换(total hip arthroplasty, THA)后压电股骨重建时精度低的问题,采用边光滑有限元法(edge-based smoothed finite element method, ES-FEM)对植入假体后压电股骨近端的骨重建进行仿真分析。方法 根据自适应骨重建理论,建立假体-压电股骨模型。基于模型的背景网格构建光滑域,引入梯度光滑技术,求解出光滑的重建刺激,进而得到术后压电股骨近端的密度分布。结果 植入假体后,受力点由股骨头转移到假体,出现应力屏蔽现象,股骨内部表观密度的分布发生明显变化。相比于FEM,ES-FEM在一定程度上能软化数值模型,提高仿真精度。在相同的网格下,电势和密度的求解精度分别提高27%和30%左右。结论 采用ES-FEM能够更精确地模拟出THA术后压电股骨近端的骨重建进程,为THA临床研究提供有效的理论依据。     

不同材料人工髋关节假体对骨界面应力分布及生物力学的影响

BACKGROUND: During joint replacement, different materials of prosthesis can be used. Different prosthesis can produce different effects and the stress distribution of bone interface. OBJECTIVE: To explore the effects of different materials on the stress distribution and biomechanics of the bone interface of artificial hip joint. METHODS: The CT scan of the hip was carried out. The image data were saved in DICOM format and processed by MIMICS software. The 3D finite element model of the femur was obtained by ANSYS. A three dimensional finite element model of the femur was made with the material properties of the femur. Three kinds of different replacement prosthesis materials (Co Cr Mo alloy, titanium alloy and composite materials) were selected, and the specific requirements of the actual joint replacement were selected, and different types of prosthesis were designed in CAE software. In the STL format, the prosthesis model was imported into MIMICS, and the femur and prosthesis were assembled. The stress status of different prosthesis was analyzed, and the stress shielding rates of exterior and interior sides of middle and lower parts of the femur, right to and 30 mm below lesser trochanter and right to lesser trochanter of the proximal femur were calculated. RESULTS AND CONCLUSION: Through three-dimensional finite element analysis, a direct and accurate model of the femur and the three-dimensional model of the prosthesis were established. According to the actual situation, material assignment of the femoral three-dimensional finite element model was conducted to obtain the corresponding model. Thus, the properties of different materials of the femur were shown visually. The femoral stress of cobalt chromium molybdenum alloy, titanium alloy, and composite material was simulated after replacement. Results found that the stress shielding rate can decrease in the middle and lower parts of the femur. After replacement, the femoral stress is higher than that of the intact femur. The experimental results show that the stress shielding of the joint was performed after joint replacement with Co Cr Mo alloy, titanium alloy and composite materials. Among them, the composite material is more close to the actual physiological environment of the human body, and it can better reduce the stress shielding effect, and is beneficial to the stress from the prosthesis to the femur.      

肿瘤型膝关节置换后股骨-假体-胫骨复合体生物力学响应

目的研究肿瘤型铰链式膝关节置换术后股骨-假体-胫骨复合体正常站立状态下的生物力学响应,探讨病人术后发生股骨穿孔的原因,为肿瘤型铰链式人工膝关节假体的优化设计与制造提供理论基础。方法兼顾CT及三维光学扫描数据建立股骨远端骨肉瘤瘤段切除肿瘤膝关节置换后的病人股骨-假体-胫骨有限元模型,并进行相关有效性验证,从而进一步分析人体站立状态下股骨-假体-胫骨复合体的应力分布及应力遮挡现象。结果 (1)在站立加载状态下,相对胫骨,股骨的应力明显更大且集中分布趋势显著,股骨前1/3区域应力较大,呈现应力遮挡效应。(2)由于模型基于临床病人几何及骨质特征建立,股骨应力集中位置与临床中病人股骨穿孔位置接近,表明在施加自身重力状态下可能发生与病人病症一致的股骨损伤行为。结论肿瘤型铰链式膝关节假体植入后,由于假体髓针深入骨髓腔,正常站立状态下亦对骨髓腔产生一定的压力;由此产生的应力遮挡效应以及假体髓针与特定骨髓腔的匹配情况均可能引起股骨应力集中,从而将可能引起股骨开裂,甚至穿破,影响手术质量。建议术前优化假体设计以减轻或避免此类现象,从而减少术后患者的并发症发生率。     

骨质疏松股骨转子间不稳定型骨折人工股骨头置换的三维有限元应力分析

BACKGROUND: Artificial femoral head replacement provides a new idea for the repair of unstable intertrochanteric fracture. Artificial prosthesis replacement may affect original femoral biomechanical stability and lead to a variety of adverse consequences.  OBJECTIVE: To analyze the stress distribution of femoral head replacement in the treatment of unstable femoral intertrochanteric fractures with three-dimensional finite element analysis. METHODS: One male old volunteer was randomly selected from population who underwent health examination. The left femur was scanned with spiral CT, and the three-dimensional finite element models of the human femur and prosthesis were established. The three-dimensional finite element model was used to simulate the actual working conditions of human climbing stairs, and the stress distribution of the bone channels around the surface of the femur and the prosthesis was analyzed with three-dimensional finite element analysis. RESULTS AND CONCLUSION: Under normal condition, the stress of the human femur was in a consistent state. Stress changed gradually from the proximal end to the distal end. The stress of the prosthesis was concentrated in the middle section. The prosthesis of inner stress distribution was analyzed to obtain stress distribution of prosthesis and femur cancellous bone interface. The analysis found that stress change trend was consistent. The results suggest that artificial femoral head replacement does not have a significant effect on the overall stress distribution of the human femur, and the overall stress distribution does not change, and the maximum stress region is located in the middle of the whole femur. After the reconstruction, the stress concentration of the femur is not observed.        

人工髋关节置换前后股骨及假体的生物力学分析

目的:研究人工髋关节置换前后股骨及假体的应力分布以及假体设计参数对应力的影响。方法:建立股骨和假体有限元模型,分析在步行峰值关节载荷和主要肌肉载荷作用下,完整股骨和置换后股骨及假体的应力水平。结果:完整股骨中上部内侧受压应力,外侧受张应力,中下部外侧受压应力,内侧受张应力,股骨应力峰值位于中下部;置换后股骨受力总体模式不变,近端应力遮挡显著。随颈干角增加,假体及股骨应力水平降低;柄长对假体应力影响不大,股骨上的应力随柄长增大略有增加。结论:假体设计时可适当增大颈干角,在骨组织条件允许的情况下可适当增加假体柄长,以减轻术后的应力遮挡效应。     

不同力学激励对骨重建数值模拟的影响

目的研究采用应变能密度、等效应力、等效应变3种不同力学激励对骨重建数值模拟结果的影响。方法建立股骨近端的二维有限元模型,基于力学稳态理论的重建控制方程并结合有限元法,分别用3种不同力学激励模拟股骨近端的内部结构及密度分布,并与CT数据计算得到的骨密度值进行定量分析比较。结果 3种力学激励模拟得到的重建结果均能反映出股骨近端的主要特征结构,但采用等效应力作为激励时得到的股骨密度曲线图的趋势和数值都与CT图像数据更为一致。结论在骨重建力学调控机制中,应力可能起主导作用。准确预测和模拟骨重建过程将对矫形外科、骨伤治疗、人工假体的优化和个体化设计等临床实践提供理论依据。     

Effect of amputation level on the stress transferred to the femur by an artificial limb directly attached to the bone

Attachment of an artificial limb directly to the skeleton has a number of potential benefits and the technique has been implemented for several amputation sites. In this paper the transfer of stress from an external, transfemoral prosthesis to the femur during normal walking activity is investigated. The stress distribution in the femur and at the implant–bone interface is calculated using finite element analysis for the 3D geometry and inhomogeneous, anisotropic material properties obtained from a CT scan of a healthy femur. Attachment of the prosthetic leg at three different levels of amputation is considered. Stress concentrations are found at the distal end of the bone and adjacent to the implant tip and stress shielding is observed adjacent to the implant. It is found that the stress distribution in the femur distal to the epiphysis, where the femur geometry is close to cylindrical, can be predicted from a cylindrical finite element model, using the correct choice of bone diameter as measured from a radiograph. Proximal to the lesser trochanter the stress decreases as the femur geometry diverges significantly from a cylinder. The stress concentration at the distal, resected end of the bone is removed when a collared implant is employed. These findings form the basis for appropriate settings of an external fail-safe device to protect the bone from excessive stress in the event of an undue load.     

全髋关节置换前后股骨侧应力的理论分析

采用复合梁基本理论来构建骨水泥和非骨水泥型全髋关节置换前后假体周围骨质应力分布的解析理论模型，通过将假体周围股骨分成等距的11个断层，并将每个断层分成前、后、内、外四个象限，分别计算每个象限的解析解和有限元分析值，做直线回归并相关分析。结果显示解析理论模型能有效的用于全髋关节置换前后力学环境变化的研究，利用该模型不仅有助于理解并解释临床相关的力学问题，而且有助于对全髋关节置换相关的涉及患者自身、假体设计和手术等多方面因素进行规律性研究。