【作者】 何荣新；

【导师】 杨迪生；

【作者基本信息】 浙江大学 ， 外科学， 2004， 博士

【摘要】 全髋置换的最主要的目的是疼痛消失，建立一个良好的关节活动度的稳定的关节。造成关节不稳定失效的原因为在股骨与髋臼处表现为无菌性松动以及在头臼联结处表现为脱位。股骨侧与髋臼侧无菌性松动不论近期还是远期均与全髋关节置换术后应力改变有关，无论是骨水泥型还是非骨水泥型，临床和放射学上均发现术后股骨侧存在着骨的生长与改建，特别是近端，可出现严重的骨质丢失，引起关节的不稳定。松动的部位尤以髋臼侧更常见，与聚乙烯内衬所受应力有关。脱位是全髋置换术后第二大并发症，是关节不稳定的主要表现。因此，该课题从以下四部分研究关节的稳定性。 第一部分 全髋置换前后股骨应力变化的有限元分析 一：研究背景 全髋关节术后股骨侧不论近期还是远期关节稳定性均与全髋关节置换术后应力改变有关，无论是骨水泥型还是非骨水泥型，临床和放射学上均发现术后股骨侧存在着骨的生长与改建，特别是近端，可出现严重的骨质丢失，引起股骨侧不稳定。全髋关节置换以后，股骨的应力方式发生了很大的变化。假体的植入将承载一定比例的负荷，引起剩余骨质的部分区域应力水平出现下降，这种现象被称为应力遮挡。而基于Wolff定律骨质改建定律说明骨质将随着机械力学微环境的变化作出股骨近端骨质的改进，在应力遮挡区域即出现一定的骨吸收。这种骨吸晰卜大母博*母位份大收被认为和假体的松动有一定的关系，特别是在年轻的置换者中，上述现象更加明显。因此应力遮挡的严重程度成为假体设计的重要指标之一，因此对假体置换的应力遮挡出现了很多的研究方法，其中包括利用尸体关节的应力应变测试，尸体标本的定量分析以及体内定量cT测定、双能X线骨密度测定法等，近年来随着计算机技术的不断发展，出现了基于数值微积分计算为基础的有限元素分析法。定量CT测定、双能X线骨密度测定法和有限元分析均为非侵袭性研究手段，而前两者的限制在于无法准确的定量分析，而有限元分析却可以弥补上述研究的不足，因此近年来备受重视而广泛应用。本研究利用计算机三维有限元分析来研究骨水泥假体和非骨水泥假体在全散关节置换前后的股骨应力分布。二:目的 研究骨水泥型和非骨水泥型全敌置换后股骨应力分布的变化，采用我院最常用的改良的Charnley Elite骨水泥假体和Sullunit的非骨水泥假体作为代表假体，来分析和观察两种不同固定方式的假体带来的应力模式和应力水平的变化。三:方法 根据正常股骨层厚lmfnCT扫描数据和图像轮廓处理技术建立股骨的三维有限元模型，并根据Depuy公司的Charnley Elite和Sumfnit假体形态建立三维有限元模型，并加载步行时足跟着地时的关节合力以及相关肌肉的肌力负荷，分析两种假体植入前后全长股骨总体应力水平并对股骨近端进行分前后内外四象限和基于假体为参照的近段、中段、远段和末段分区，并对假体周围区域骨质应力分布和应力大小进行分区量化研究。四:结果 无论骨水泥型还是非骨水泥型假体的植入并没有显著改变全长股骨的总体应力模式，股骨内侧均以压应力为主，而外侧则以张应力为主，股骨的应力峰值区域仍位于股骨干的中远段区域，股骨应力峰值在置换后有所降低，Sulnlnit非骨水泥置换峰值下降较EI ite骨水泥型更明显。股骨近端假体周围骨质应力分布出现了很大变化，置换后股骨距区域的高应力分布消失，出现了显著的应力遮挡，各晰卜大母博士母位伦人相应象限和区段的应力水平均出现下降，应力下降程度Sununit近端多孔非骨水泥型假体要高于Elite骨水泥型假体。五:结论 两种假体植入后均在股骨近端形成显著的应力遮挡，并可因此造成基于wo 1 ff定律的骨吸收改建，是造成假体周围骨质术后骨质疏松并引起假体松动的重要原因之一。股骨近端于假体末端水平是假体周围骨质应力最高的区域，并存在假体和骨质间的模量差，该应力模式是引起该区域术后易于出现假体周围骨折和大腿中段疼痛的力学基础。两种固定方式的假体均需通过进一步改进以减少应力遮挡。第二部分:全敌置换后聚乙烯内衬应力的有限元分析一:研究背景 人工艘关节置换术后造成关节不稳定失效的原因为无菌性松动，松动的部位尤以散臼侧更常见，与聚乙烯内衬所受应力有关。聚乙烯内衬原因的全艘失败是假体关节置换后失败的最大的原因，包括内衬的破坏和磨损，其中磨损引起的无菌性松动被认为是需要翻修手术的最主要的原因，因其聚乙烯磨损微粒可以引起假体周围骨溶解而引起松动。所以聚乙烯内衬的设计上通过改变承重面的特性和材质的改进来增加聚乙烯磨损抵抗，其目的都是为了减少聚乙烯的磨损而延长假体的寿命。除了聚乙烯内衬本身的改进，外科技术的合适运用以及假体的慎重选择和患者本身的一些注意也可以同样减少聚乙烯相关的失败而延长人工关节的寿命。而引起聚乙烯内衬磨损的根本原因是聚乙烯承重引起的关节面的应力，通过双滑距有限元模型的计算公式可以根据聚乙烯表面的应力水平来估算内衬的磨损。许多研究表明聚乙烯内衬的应力水平更多还原

【Abstract】 The main objective of the THA is pain relief and constructing a steady joint with satisfactory activity. The causes leading to surgical failure of instability lie in aseptic loosening around the femur and the acetabular cup and dislocation around the head-cup connection. There is a close relevance between aseptic loosening around the femur and the acetabular cup and the stress change after THA whether in the near future or in the long run. It turns out to be the postoperative growth and reconstruction around the femur clinically and radiologically whether it is cemented or not. There may be severe loss of the bone matrix, especially proximal, which will result in the joint instability. The loosening will be more commonly seen around the cup which relates to the stress of the polyethelene insert. The hip dislocation after THA is a severe and common complication, it is the mostly behave to the joint instability Consequently, we will discuss the joint stability through four aspects as follows:Section 1: Finite element analyses of changes infemoral stresses after total hip arthroplasty1: Summary of Background DataThe stress distribution in the femur wether near period or the long-term joint stability all has something to do with Total Hip Arthroplasty(THA), wether is a bone cement type or not bone cement type. It is clinical and radialization to all discovery the bone growth and rebuild in the femur side especially near carry after THA can appear the serious bone substance to lose, causing a femur side unsteady. The natural stress distribution in the femur is significantly altered after total hip arthroplasty. Whenan implant is introduced, it will carry a portion of the load, causing a reduction of stress in some regions of the remaining bone. This phenomenon is commonly known as stress shielding. In response to the changed mechanical environment the shielded bone will remodel according to Wolff’s law, resulting in a loss of bone mass through the biological process called resorption. Resorption can , in turn, cause or contribute to loosening of the prosthesis. The problem is particularly common among younger. So reducing stress shielding is an important standard of prosthesis design and clinicians and patients will benefit if accurate methods of predicting and monitoring bone strength in-vivo are available. Except for in vitro experiment research based on cadaver, non-invasive tools suitable for proximal femoral strength prediction include quantitative computed tomography (QCT) and dual energy X-ray absorptiometry (DXA). They provide regional bone density evaluations for specific portions of the proximal femur, and can estimate bone size, which has been related to bone resorption after total hip arthroplasty. But previous studies evaluating femoral remodeling after total hip arthroplasty have used QCT and DXA. Limitation of these techniques make it impossible to quantify the magnitude of bone loss in terms of cortical thinning and cortical bone area and bone mineral density changes. In these years, developed with compute technique and mathematic calculus, the three dimension finite element analysis was inducted into biomechanical study. Using excellent quantify calculation ability, finite element analysis method explained further precision than QCT and DXA models. And three-dimensional finite element models become a promising method for predicting bone remodel after total hip arthroplasty. In this study, we explain the changes of femurs stresses after a cemented prosthesis and a cementless prosthesis replacement using finite element analysis method, and make quantity analysis to femoral stresses after THA.2: ObjectiveTo determine the variation in femoral stresses after inserted a cemented and aproximal porous cemnentless femoral prostheses. Using Charnley Elite cemented prosthesis and Summit cementless prosthesis design, we quantify the stress level and stress distribution models after the two different prostheses replacements.3: MethodsConsidering the complex geometry更多还原