内骨架一体化小腿假肢的生物力学研究

一体化假肢是以聚合物为材料从接受腔到假腿一体成型的新型下肢假肢，它比传统型假肢更经济、美观、轻便，具有较大的应用前景。目前的相关研究主要集中在设计与制作及少量的临床研究方面。由于一体化假肢与传统型假肢在结构上的差异，有必要对其进行应力分析。本研究的目的是开展内骨架一体化假肢的生物力学研究，本研究基于内骨架一体化小腿假肢的真实几何构型，建立三维有限元模型，计算该模型在模拟Heel OH步态时相的载荷作用下的应力分布；在保持该模型的几何形状不变的情况下，建立了三个不同壁面厚度的一体化小腿假肢的有限元模型，分析壁面厚度对一体化小腿假肢应力分布的影响；通过分别赋予模型四种不同高分子聚合物的材料力学特性值，分析不同材料的一体化假肢的应力分布特点；分别对模型施加与正常步态的五个典型时相对应的载荷，分析一体化小腿假肢在各步态时相的应力分布特点。本研究结果对一体化假肢设计有指导价值。     

一体化小腿假肢的三维有限元应力分析

建立一体化小腿假肢和残肢的三维模型，应用有限元分析方法，计算此模型在模拟Mid—Stance步态时相的载荷作用下各节点的应力，从而得到此模型内外表面的应力分布，为一体化假肢设计的CAD＼CAM系统提供理论依据。计算结果表明，接受腔的应力值较小，假腿的应力值较大，高应力区出现在假腿下端及接受腔与假腿的交界区域。     

小腿假肢接受腔的三维有限元分析

通过建立三维非线性有限元模型来分析小腿假肢接受腔与残肢之间的载荷分布。此模型基于残肢,骨头,软套和接受腔的三维几何形状,考虑界面摩擦滑动条件和软组织的大变形等非线性因素。模型可以预测不同外载下残肢和接受腔之间的压力,剪切力和相对滑动情况。并分析了不同的接受腔形状对载荷分布的影响。     

个体化下肢小腿假肢接受腔设计的生物力学评价技术研究

作为传递体重、固定假肢的部件 ,接受腔对于小腿假肢使用的舒适性和方便程度有决定性的作用。本研究建立了基于有限元应力分析的小腿假肢生物力学评价技术平台 ,实现了小腿残端 /接受腔 3D几何建模与信息交互、三维有限元自动建模及应力分析。 3D模型与信息交互的实现基于得到广泛支持的OpenGL技术 ,有限元模型的构建采用了专门针对小腿残端 /接受腔结构特点的自动建模方法 ,通过构建档案数据库系统作为整个系统的操作平台。该技术平台可与现有的CAD/CAM系统相结合 ,为接受腔的个体化设计提供生物力学定量化依据。其临床应用将改善传统的设计流程 ,提高设计效率。同时 ,它也是未来构建接受腔设计专家 /智能系统的基础。     

小腿残肢与接受腔的非线性有限元分析

目的研究残肢与接受腔生机界面力学特性及残端应力情况,为设计和优化小腿接受腔结构、提高其佩戴舒适性提供理论依据。方法针对释压稳定(compression-release stabilization,CRS)接受腔,采用有限元软件ABAQUS分析残肢与CRS接受腔界面应力分布情况,软组织采用非线性超弹性材料Mooney-Rivlin本构模型,得到静止站立中期残肢与CRS接受腔接触界面正应力和剪切应力分布情况,并相应建立髌韧带承重(patellar tendon bearing,PTB)小腿接受腔三维有限元模型,将两者结果进行比较。结果残肢与CRS接受腔界面应力主要分布在胫骨内侧、胫骨外侧和后肌群等承重区,与PTB接受腔模型主要受力区域相似,CRS接受腔残肢末端平均界面应力较PTB接受腔高19 kPa。结论 CRS接受腔具有较好的透气性且应力分布较合理,接受腔形状的不同可改变残肢与接受腔生机界面应力分布,优化其设计有助于提高假肢穿戴舒适性。     

小腿假肢接受腔计算机三维模型的构建

背景:假肢接受腔作为截肢患者肢体残端和假肢之间载荷传递的惟一通道,是影响假肢适配性的重要部件。假肢接受腔的三维建模是接受腔实用性的关键,可以在测量时得到更准确的数据。目的:建立假肢接受腔计算机三维模型,为接受腔有限元分析提供数据基础,为加工制造接受腔提供可靠的参数。方法:选择1例32岁右侧小腿截肢的男性患者,髋关节各肌力正常,髋18°屈曲挛缩,其他关节活动度正常。根据患者CT和核磁共振扫描图像,采用Mimics10.0软件处理数据,构建假肢接受腔计算机三维模型,准确模拟残肢和接受腔的结构。结果与结论:建立的小腿残肢和接受腔计算机三维模型比较准确地反映了接受腔和残肢的几何特征和外部轮廓。假肢接受腔三维模型的建立有助于提高制作的成功率,从根本上改变传统依靠手工设计、测量、取型、修型等落后的生产模式。     

基于三维有限元静态分析的人体足部生物力学研究

目的:建立一个基于健康人体的、系统的、具有高度几何相似性的足部三维有限元模型,并用此模型静态地分析人体双足站立相时的足部内部的生物力学特性,量化足部内部的应力/应变状况、足部内侧纵弓变化等。方法:基于志愿者右足的3维CT层切数据,对足踝系统相关组织进行几何重建及其网格划分,建立完整的有限元模型并对人体站立状态进行了静态模拟。结果:站立姿态下的足底表面接触压力分布、内部软组织应力分布以及内侧足弓的变形等人体足部生物力学特性被量化。结论:本研究中创建的三维有限元足部模型,经验证是一个正确、可靠的模型,可以帮助临床医生和其他研究人员更好的理解足部内部的许多生物力学特性。     

足部三维有限元建模方法及其生物力学应用

目的探讨建立足部三维有限元模型的方法,应用模型模拟分析研究鞋垫设计参数,不同软组织刚度和受力情况下对足部的生物力学影响。方法建立基于解剖结构,包括软组织,韧带和腱膜,考虑材料的非线性和关节接触的足部三维有限元模型。有限元模型的可靠性利用模拟足踝关节在不同病理、手术和鞋垫矫治情况下的生物力学反应来验证。结果有限元分析结果表明,定制型鞋垫的形状比鞋垫材料的刚度对减少足底最大压力有更重要影响。软组织刚度的增加引起足底接触面积的减小,从而会导致足底跖骨区最大压力增加。部分和完全松解足底腱膜都会降低足弓高度,并增加足底韧带的张力和增加中足和跖骨的应力。体重增加和跟腱拉力增加都将成倍足底筋膜的拉力。结论所建足部有限元模型能预测足底压力分布和足内部骨骼软组织应力、应变情况,可以成为设计鞋垫和研究足部各种临床状况提供有力的分析工具。     

有限元法建立髋关节三维模型及正立位下的应力分析

目的:建立髋关节的三维有限元模型,并分析正立位下的生物力学分布特点。方法:选取1名志愿者,以髋部CT扫描图像为数据源,导入软件Mimics 14.0进行三维重建,将所建模型再导入Ansys13.0中,建立有限元模型,计算正立位下髋关节的力学分布特征。结果;成功建立了髋骨、股骨上段的三维几何模型和有限元模型。模拟体质量负荷,获得髋骨股骨的应力分布云图,集中在髋骨的弓状线,髋臼后上方,股骨颈内、外侧。结论:利用Mimics、Ansys建立的髋关节有限元模型仿真性高,可以进行生物力学分析;分析结果可信,对预防、治疗髋关节损伤等具有重要意义。     

假肢接受腔设计及界面应力的有限元分析

文题释义： Mimics 10.0软件：作为专业的三维图像处理软件,能将CT图像转化为残肢的三维模型,计算机生成的三维模型与患者的实际尺寸基本无差别。 有限元分析：是利用数学近似的方法对真实物理系统(几何和载荷工况)进行模拟的方法。 背景：残肢-接受腔界面生物力学特性不仅对假肢的适配性有着直接影响,而且也是对接受腔结构进行优化设计的基础。将数字化设计技术与康复工程结合在一起,将有效地提髙假肢接受腔的制作效率和质量。 目的：采用逆正向结合的建模方法,对小腿截肢患者进行定制式的接受腔模型设计,评估残肢与接受腔的界面应力,对接受腔进行迭代设计,优化后的模型采用3D打印制作,以改善传统手工制作接受腔方法。 方法：选择2例内蒙古自治区荣誉军人肢残康复中心的小腿截肢志愿者,根据患者残肢的CT扫描图像,采用Mimics进行图像处理,然后经过Geomagic和UG逆向得到残肢的几何模型。通过使用计算机辅助设计软件Fusion360,根据残肢各个部位的组织结构不同的承受能力作为修型原理对接受腔进行正向建模设计。选用Mooney-Revlin超弹性模型定义软组织的材料特性,对残肢-接受腔界面应力进行有限元分析,并根据结果反馈指导对接受腔进行迭代设计,对再次修型后的接受腔模型进行评估。3D打印制作出接受腔,并进行实验测量。 结果与结论：①对迭代设计后的接受腔与残肢界面的应力进行分析,得到残肢各区域的应力值均低于疼痛阈值,符合设计标准,能较好实现功能传递性和安全舒适性;②此2例患者穿戴3D打印制作的接受腔适配性、稳定性良好,步行对称性相比手工制作接受腔均有显著改善,满足残肢生物力学要求;③试验建立了完整的假肢接受腔的设计、评估及制造系统。 ORCID: 0000-0002-8570-9689(王晓辉) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

A numerical approach to evaluate the fatigue life of monolimb

Monolimb refers to a transtibial prosthesis with the prosthetic socket and the shank being molded into one piece of thermoplastic material. Shank flexibility of a monolimb can improve gait and comfort. However, fatigue failure of monolimbs under cyclic walking load is an important concern. This study is to evaluate the fatigue life of a monolimb designed for a transtibial amputee, based on finite element analysis, the statistical Miner's rule and reliability analysis. Stress uncertainty due to modeling error and the scatter in fatigue test data were considered. Results indicated that the accuracy of fatigue life evaluation of monolimb depends significantly on the precision of stress estimation. In addition, relationship between fatigue failure probability and the number of walking steps was suggested providing a reference for clinicians to determine the interval of the inspection for the monolimb.     

惯性载荷对截肢患者残肢/接受腔界面应力的影响研究

接受腔/残肢界面压力分布特征是假肢优化设计的基础,传统的有限元模型只限于静态分析,不符合实际情况。本文以小腿截肢患者为研究对象,建立了三维非线性有限元模型,给出了一个步态周期内残肢界面压力的变化规律,并对惯性载荷的影响进行了定量比较。结果表明:界面压力主要分布在髌韧带、胫骨内外侧和窝区,一个平地正常速度行走的步态周期内,站立相压力变化呈双峰蝶形,惯性载荷引起的平均压力幅值变化为8.4%;而在摆动相压力幅值变化高达20.1%,并且变化规律相反。行走过程中惯性载荷的影响不能忽略。     

A robust design procedure for improvement of quality of lower-limb prosthesis

Lower-limb prostheses are used to restore amputee's walking. Monolimb is one of the designs referring to socket and the shank being molded into one piece of thermoplastic material. Appropriate shank flexibility of a monolimb can improve gait of an amputee. However, during the fabrication, the variations of design variables are inevitably produced which may lead the unexpected shank deflection and directly influence on gait efficiency of an amputee. This paper presents a robust design procedure for improvement of quality of the monolimb by simultaneously minimizing performance variations caused by variations in design variables and bringing the mean value of performance on target. The robust design procedure embodies the integration of response surface methodology with genetic algorithms. Response surface models are developed for the responses of monolimb as functions of design variables over the region of interest and genetic algorithms are employed to find the robust solution. A robust design of monolimb is performed for an amputee subject and the results show that the robust design can design a "robust" monolimb which provides specified performance targets that are minimally sensitive to the variations of design variables. This indicates that robust design may have the potential application in improving the quality of the prescribed prosthesis.     

Spherical center axial hinge knee prosthesis causes lower contact stress on tibial insert and bushing compared with biaxial hinge knee prosthesis

BackgroundMotion axial system may affect contact stress of hinge knee prosthesis. However, it is unclear which axial system provides the better biomechanical effect. Therefore, the aim of this study was to compare the contact stress and stress distribution on the tibial insert and the bushing of hinge knee prostheses with a biaxial (BA) system and a spherical center axial (SA) system during a gait cycle.MethodsThree-dimensional finite-element (FE) models of the prostheses with different motion systems were included. The comparisons between experimental tests and FE analyses were performed to verify the models. Dynamic implicit FE analyses were performed to investigate the peak contact stresses and stress distributions on the tibial insert and the bushing.ResultsThe peak contact stresses on the tibial insert and the bushing of the BA prosthesis were higher than those of the SA prosthesis during most gait cycles. The contact time on the bushing is short in the SA prosthesis. The stress distributions on the superior surface of the tibial insert in the BA prosthesis were at the posterior side, but of the SA prosthesis were not fixed.ConclusionThe SA prosthesis has a lower peak contact stress on tibial insert and bushing than the BA prosthesis; in addition, the SA prosthesis has a ‘self-adjustment’ mechanism which could disperse high stress on the tibial insert to decrease the risk of wear and damage. The comparison could help designers and surgeons to better understand the future design of rotating hinge knee prostheses which should be able to achieve multiaxial motion and complete weight bearing by the tibial condylar to transmit the axial force better.     

Finite element analysis of the dental implant using a topology optimization method

In recent years, many attempts have been made to optimize the shape of dental implants. The purpose of this study took advantage of the topology optimization in the finite element (FE) method to look for redundant material distribution on a dental threaded implant and redesigned a new implant macrogeometry with the evaluation of its biomechanical functions. Three-dimensional FE models were created of a first molar section of the maxilla and embedded with an implant, abutment and a superstructure by using the commercial software ANSYS 11.0. The final design of a new implant was shaped by topology optimization, and four FE models namely traditional implants with bonded (TB) and contact (TC) interfaces, and new implants with bonded (NB) and contact (NC) interfaces, were established. Material properties of compact and cancellous bone were modeled as fully orthotropy and transversely isotropy respectively. Oblique (200-N vertical and 40-N horizontal) occlusal loading was applied on the central and distal fossa of the crown. The FE model estimated that the volume of the new implant could be reduced by 17.9% of the traditional one and the biomechanical performances were similar, such as the stress of the implant, stress of the implant-bone complex, lower displacement, and greater stiffness than the traditional implant. The advantages of the new implant increased the space to allow more new bone ingrowth or assist in fusing more bone graft into the bone sustaining the implant stability and saved material. Its disadvantage was higher stress level compared with that of the traditional implant.     

髋关节置换的三维有限元分析

目的本文建立股骨髋关节置换有限元模型，并进行了静力学模拟计算，寻求假体的材料属性对髋关节置换后产生的的影响。方法运用逆向工程与有限元的基本概念和理论，采用医学专用的建模软件mimics读取原始的股骨CT图片的dicom格式，完成股骨二维重建，然后根据股骨髓腔几何解剖状态应用CAD软件设计个性股骨假体。在ansys中对两个模型进行有限元装配，进行接触耦合分析!结果建立了精确的股骨模型和设计了个性假体。利用MIMICS基于灰度值进行赋材质，实现股骨有限元模型材料正确的非均匀及各向异性描述。成功模拟了三种假体材料置换后股骨的应力。结论三种材料中复合材料假体更接近人体生理环境，减弱了假体的应力遮挡，有利于力由假体传到到股骨上。为改进人工髋关节的设计、置换和提高人工髋关节寿命提供了一些有益的依据。研究结果表明这种假体设计和分析方法更为合理、可靠。     

Effects of liner stiffness for trans-tibial prosthesis: a finite element contact model

The socket liner plays a crucial role in redistribution of the interface stresses between the stump and the socket, so that the peak interface stress could be reduced. However, how the peak stress is affected by various liner stiffnesses is still unknown, especially when the phenomenon of the stump slide within the socket is considered. This study employed nonlinear contact finite element analyses to study the biomechanical reaction of the stump sliding with particular attention to the liner stiffness effects of the trans-tibial prosthesis. To validate the finite element outcomes, experimental measurements of the interface stresses and sliding distance were further executed. The results showed that the biomechanical response of the stump sliding are highly nonlinear. With a less stiff liner, the slide distance of the stump would increase with a larger contact area. However, this increase in the contact area would not ensure a reduction in the peak interface stress and this is due to the combined effects of the non-uniform shape of the socket and the various sliding distances generated by the different liner stiffnesses.     

Optimization design of thumbspica splint using finite element method

De Quervain’s tenosynovitis is often observed on repetitive flexion of the thumb. In the clinical setting, the conservative treatment is usually an applied thumbspica splint to immobilize the thumb. However, the traditional thumbspica splint is bulky and heavy. Thus, this study used the finite element (FE) method to remove redundant material in order to reduce the splint’s weight and increase ventilation. An FE model of a thumbspica splint was constructed using ANSYS9.0 software. A maximum lateral thumb pinch force of 98 N was used as the input loading condition for the FE model. This study implemented topology optimization and design optimization to seek the optimal thickness and shape of the splint. This new design was manufactured and compared with the traditional thumbspica splint. Ten thumbspica splints were tested in a materials testing system, and statistically analyzed using an independent t test. The optimal thickness of the thumbspica splint was 3.2 mm. The new design is not significantly different from the traditional splint in the immobilization effect. However, the volume of this new design has been reduced by about 35%. This study produced a new thumbspica splint shape with less volume, but had a similar immobilization effect compared to the traditional shape. In a clinical setting, this result can be used by the occupational therapist as a reference for manufacturing lighter thumbspica splints for patients with de Quervain’s tenosynovitis.