胫骨假体的构型与材料对胫骨骨重建行为影响的数值仿真研究

发布时间：2018-05-31 03:35

本文选题：骨重建算法 + 有限元分析　；参考：《吉林大学》2017年硕士论文

【摘要】：全膝关节置换术是治疗膝关节疾病的有效手段,随老年人口的日益增多,在未来将有更多患者接受全膝关节置换术的治疗。然而,胫骨假体植入后会造成应力遮挡与应力集中,从而诱发胫骨骨量分布异常,导致病人术后疼痛并增大假体松动的风险。因为假体的构型以及材料等设计因素会直接影响胫骨的应力遮挡与应力集中情况,所以假体的设计因素一直备受关注。本文通过数值仿真的方法,研究胫骨假体的构型与材料对胫骨骨重建行为的影响。研究分为以下两个部分:本文第一部分建立了三维胫骨和假体的有限元模型,结合骨重建算法定量地研究了非骨水泥型胫骨假体柄的材料与长度对胫骨骨重建行为的影响。采用柄的长度有三组,分别为110 mm、60 mm和30 mm,每组长度采用四种材料,分别为钛合金(Ti)、理想骨材料和两种功能梯度材料(FGM),FGM的组分分别为Ti和胶原-羟基磷灰石(FGM I),及Ti和生物玻璃(FGM II)。从胫骨骨密度分布、von Mises应力分布、柄与胫骨接触面切应力三方面研究柄的几何长度与材料对应力遮挡、应力集中,以及假体稳定性的影响。本文的研究结果表明:在长度方面,长柄会比短柄造成更严重的应力遮挡与应力集中,但是长柄造成的接触面切应力更小,会为假体提供更好的稳定性;在材料方面,与Ti相比,FGM I可以减小宿主胫骨的应力遮挡与应力集中情况,并提供更小且更均匀的接触面切应力,减小假体松动的风险;此外,当柄的材料属性接近骨的材料属性时,它的弹性模量变化才会对应力遮挡情况产生显著影响;最后,与柄的长度相比,材料对胫骨近端骨重建的影响更为显著。鉴于假体长度往往受限于假体的固定方式和病人胫骨的解剖结构,从材料方面对柄进行改进更具灵活性与可行性。从微创手术的角度考虑,应减小假体对胫骨骨组织的破坏;另外,考虑到胫骨结构以及生理载荷的非对称性,应设计体积分数较小的非对称假体结构用于全膝关节置换术。本文第二部分将拓扑优化理论与有限元分析相结合,对骨水泥型胫骨假体柄与加强肋区域进行优化设计。以设计域的高中低三种体积分数(分别为70%、50%和30%)为约束条件,结构的最大刚度为目标函数,分析所得结构对胫骨力学环境的影响,并得出理想的假体构型。结果表明:当松质骨区域与胫骨托盘距离小于20 mm时,拓扑优化后的三组假体均可以减缓应力遮挡情况;当该距离为30 mm-40 mm时,拓扑优化后的假体可以显著地减轻应力集中情况,其中以70%体积分数为约束的假体减缓应力遮挡效应最为明显。因此胫骨假体以较高的体积分数(70%左右)为约束时,获得的拓扑优化构型更为合理。分析原始的与优化后的假体构型差异发现,去除加强肋以及柄的前外侧区域,有助于减缓胫骨前外侧区域的应力遮挡,以及底端的应力集中情况。本文先将骨重建算法与有限元分析相结合,研究了非骨水泥型胫骨假体柄的材料与长度对胫骨骨重建过程的影响;然后建立了骨水泥型胫骨假体与胫骨的有限元模型,结合拓扑优化理论,探究体积分数优化后的假体结构对胫骨力学环境的影响。为胫骨假体的设计提供了理论依据,有助于提高胫骨假体使用寿命,并减轻病人疼痛。
[Abstract]:Total knee arthroplasty is an effective method for the treatment of knee joint diseases. With the increasing population of the elderly, more patients will be treated with total knee replacement in the future. However, the tibial prosthesis will cause stress occlusion and stress concentration, which leads to the abnormal distribution of the bone mass of the tibia, causing postoperative pain and increasing the prosthesis of the patients. The risk of loosening. Because the configuration of the prosthesis and the design factors such as material will directly affect the stress occlusion and stress concentration of the tibia, the design factors of the prosthesis have been paid much attention. In this paper, the effects of the configuration of the tibial prosthesis and the material on the tibial bone reconstruction are studied by numerical simulation. The study is divided into two parts. Part 1: in the first part of this paper, a finite element model of three dimensional tibia and prosthesis was established. The effect of the material and length of the non bone cement type tibial prosthesis on the reconstruction behavior of tibia was quantitatively studied with the bone reconstruction algorithm. The length of the shank was three groups of 110 mm, 60 mm and 30 mm respectively. The length of each group adopted four kinds of materials, respectively titanium alloy. (Ti), ideal bone material and two functional gradient materials (FGM), FGM components are Ti and collagen hydroxyapatite (FGM I), and Ti and bioglass (FGM II). From the tibial bone density distribution, von Mises stress distribution, and the shank contact surface shear stress three aspects of the geometric length of the handle and material corresponding force occlusion, stress concentration, and prosthesis The results of the study show that the length, the long handle causes more severe stress occlusion and stress concentration than the short handle, but the long handle has smaller contact stress, which provides better stability for the prosthesis; in the material aspect, FGM I can reduce the stress occlusion and stress concentration of the host tibia compared with the Ti. A smaller and more uniform contact surface shear stress is provided to reduce the risk of prosthesis loosening; in addition, when the material property of the handle is close to the material property of the bone, the change of its modulus of elasticity will have a significant effect on the force occlusion; finally, the effect of the material on the proximal bone reconstruction of the tibia is more significant compared with the length of the handle. The length of the prosthesis is often limited to the fixation of the prosthesis and the anatomical structure of the tibia of the patient. It is more flexible and feasible to improve the handle from the material. From the point of view of minimally invasive surgery, the damage to the bone tissue of the tibia should be reduced. In addition, the volume fraction should be designed considering the dissymmetry of the tibial structure and the physiological load. The smaller asymmetric prosthesis is used for total knee arthroplasty. In this second part, the second part combines the topology optimization theory with the finite element analysis to optimize the bone cement type tibial stem and stiffening ribs. The maximum three volume fractions (70%, 50% and 30% respectively) of the design domain are constrained, and the maximum stiffness of the structure is The objective function is used to analyze the effect of the structure on the tibia mechanical environment and obtain the ideal configuration of the prosthesis. The results show that when the distance between the cancellous bone area and the tibial tray is less than 20 mm, the three components of the topology optimized can reduce the stress occlusion. When the distance is 30 MM-40 mm, the prosthesis after topology optimization can be significantly reduced. In the stress concentration condition, the 70% volume fraction of the prosthesis is most obvious in reducing the stress shielding effect. Therefore, the topologically optimized configuration of the tibial prosthesis is more reasonable when the higher volume fraction (about 70%) is restricted. Analysis of the original and optimized configuration differences of prostheses is found to remove the stiffeners and the anterolateral area of the stem. In this paper, the bone reconstruction algorithm and finite element analysis are combined to study the effect of the material and length of the non bone cement type tibial prosthesis on the reconstruction of the tibia, and then the finite element model of the bone cement type tibial prosthesis and the tibia is built. In combination with topological optimization theory, the effect of the structure of the prosthesis on the tibial mechanical environment is explored, which provides a theoretical basis for the design of the tibial prosthesis, which helps to improve the service life of the tibial prosthesis and reduce the pain of the patients.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R318.08;R68

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