β-磷酸三钙/聚左旋乳酸骨折内固定材料的体外降解性能研究

骨折内固定材料是骨修复中不可或缺的重要材料.为了避免二次手术,可降解的骨折内固定材料越来越受到重视.本文采用溶液成膜/热压成型的方法制备了不同比例的β-TCP/PLLA骨折内固定复合材料,将不同比例的复合材料分别浸入SBF中进行体外降解,之后进行GPC、IR、吸水率分析及抗弯、抗压强度的测定,筛选出β-TCP与PLLA的最佳比例.结果表明:降解初期聚乳酸分子量下降较快,3周后下降减缓;降解后,复合材料表面形成了HCA.含20%、30%β-TCP的材料抗弯抗压下降缓慢,而40%的下降较快,初步显示30%为最适的β-磷酸三钙/聚左旋乳酸复合比例.     

一种新型肱骨大结节解剖锚钉锁定钢板的设计及骨折模型开发

目的:探索用于治疗肱骨大结节骨折的新型内固定方法,并开发用于力学实验的骨折模型.方法:基于肱骨大结节的解剖形态和骨折分型设计一种用于肱骨大结节骨折内固定的解剖锚钉锁定钢板,并基于Sawbones仿骨材料开发肱骨大结节骨折模型.结果:本文设计的解剖锚钉锁定钢板切迹低、服帖性好,相较于现有的内固定技术具有骨折块复位精度高、对骨折块压迫小以及对血运破坏少等优点.开发的肱骨大结节骨折模型为不同内固定方法的力学测试提供了高度一致且成本低廉的实验样本.结论:本文设计开发的锁定钢板和骨折模型相比现有肱骨大结节骨折内固定技术和实验模型具有一定的优势.     

用于骨折内固定板的可吸收聚合物及其复合材料

综述了骨折内板材料的最新研究进展,阐述了可吸收聚合物（如聚乳酸,聚乙醇酸等）,自增强可吸收聚合物复合材料及碳纤维增强可吸收聚合物复合材料的机械性能及生物相容性,碳纤维增强可吸收聚合物复合材料是最有前途的内固定板材料。     

超高分子量聚-DL-乳酸及其骨折内固定系统的研究进展

聚乳酸类可生物降解材料是基础的生物医学材料,它在医学上的用途主要有两个方面:一是作为药物控制释放的载体材料,这类新的药物剂型国外已有十多种产品上市,我国现有控制释放剂型领域还是空白,因此市场前景非常好。二是用作可吸收医疗器械。国外现有的可吸收医疗器械主要有:可吸收缝线,可吸收骨折内固定器,可吸收导管,可吸收膜,可吸收齿科材料等。 近年来,骨创伤事故频繁发生,我国每年大约有近百万的骨折病人需要通过手术对骨折进行治疗。因此,骨内固定技术是骨科中治疗骨折、骨创伤的不可缺少的重要手段。目前在骨内固定手术中使用的内固定器,如骨板、螺钉、棒、针等多是由不锈钢或     

CMPw/PLLA骨折内固定材料的制备及强度性能研究

为了提高骨折内固定材料聚乳酸的力学强度及承载能力,通过玻璃结晶化方法制备得到长径比为30～50的偏磷酸钙晶须(CMPw),将CMPw与左旋聚乳酸(PLLA)复合,制得抗压强度为80MPa,抗弯强度为40MPa,断裂强度达到170MPa的复合材料.探讨了热处理温度、萃取条件、晶须含量、粉体粒径对偏磷酸钙产物形貌和复合材料强度的影响.     

卵磷脂改性β型偏磷酸钙晶须研究

利用卵磷脂(PC)良好的生物相容性对β型偏磷酸钙晶须(β-CMP)进行表面改性,可得到具有较高强度的骨折内固定材料.通过测定接触角评价了改性β-CMP晶须的亲/疏水性,结果表明,经5%(wt)卵磷脂改性后晶须的疏水性优于未处理的晶须.研究了卵磷脂改性前后β-CMP晶须的形貌,表明引入表面改性剂可以提高晶须在PLLA中分散性能.材料的抗压强度测试结果显示改性后的β-CMP/PLLA材料强度比未改性材料提高了近33%.     

基于DFAD-FBS的自适应前臂骨折外固定护具设计

目的 针对前臂骨折外固定护具实时贴合性差的问题,进行自适应前臂骨折外固定护具产品设计研究。方法 将自适应设计方法（DFAD）与功能-行为-结构模型（FBS）相结合,构建自适应前臂骨折外固定护具设计方法,并基于形状记忆聚合物的仿生设计研究,进行自适应前臂骨折外固定护具产品设计。结果 基于DFAD-FBS设计方法对前臂骨折外固定护具进行分析,将仿生蜂窝结构的形状记忆聚合物应用于自适应前臂骨折外固定护具产品设计,并通过有限元分析和贴合度试验验证了产品设计的可行性。结论 DFAD-FBS设计方法为解决前臂骨折外固定护具的实时贴合问题提供了新的方向,并验证了形状记忆聚合物用于解决前臂骨折外固定护具贴合性的可行性,对产品的适应性设计问题提供了有意义的参考。     

角蛋白在生物材料中的应用

结合角蛋白自身特殊的结构及其性能,介绍了角蛋白的提取方法,如机械法、酸碱法、还原法、氧化法和金属盐法等;重点综述了角蛋白及其改性产品在生物材料中的应用,如角蛋白可以作为骨折内固定棒、人工腱、烧伤敷料、注射生物复合填充材料等;最后展望了角蛋白的应用前景和发展方向.     

碳纤维增强聚乳酸(C/PLA)复合材料的力学性能(Ⅰ)

对新型骨折内固定材料碳纤维增强聚乳酸(C/PLA)复合材料的力学性能进行了评价.重点研究了纤维体积分数(Vf)和硝酸表面处理对C/PLA复合材料力学性能的影响规律.研究表明,随着Vf的增加,复合材料的弯曲强度、弯曲模量、冲击强度和剪切强度均先增加,达峰值后又减小.硝酸表面处理可明显提高复合材料的界面结合强度,从而使其力学性能明显提高.     

经伤椎短节段内固定治疗骨质疏松性胸腰椎骨折的三维有限元分析

本文在CT扫描数据的基础上通过逆向建模构建人体脊柱T11-L3椎段三维几何模型,去除L1椎体下部的骨质模拟爆裂性骨折,然后建立经伤椎短节段内固定有限元模型,赋予各个组织材料属性,在模型上施加不同的载荷模拟人体胸腰椎前屈、后伸、左侧弯、右侧弯、左轴向旋转、右轴向旋转六种生理运动状态.通过有限元仿真计算经伤椎短节段内固定方式治疗骨质疏松性胸腰椎骨折时,椎体活动度(range of motion,ROM)以及内固定系统的应力.     

Cauchy problems of Laplace's equation by the methods of fundamental solutions and particular solutions

The Cauchy problems of Laplace's equation are ill-posed with severe instability. In this paper, numerical solutions are solicited by the method of fundamental solutions (MFS) and the method of particular solutions (MPS). We focus on the analysis of the MFS, and derive the bounds of errors and condition numbers. The analysis for the MPS can also be obtained similarly. Numerical experiments and comparisons are reported for the Cauchy and Dirichlet problems by the MPS and the MFS. The Cauchy noise data and the regularization are also adopted in numerical experiments. Both the MFS and the MPS are effective to Cauchy problems. The MPS is superior in accuracy and stability; but the MFS owns simplicity of algorithms, and earns flexibility for a wide range of applications, such as Cauchy problems. These conclusions also coincide with [37]. The basic analysis of error and stability is explored in this paper, and applied to the Cauchy data. There are many reports on numerical Cauchy problems, see the survey paper in [12]; most of them are of computational aspects. The strict analysis of this paper may, to a certain degree, fill up the existing gap between theory and computation of Cauchy problems by the MFS and the MPS. Moreover, comprehensive analysis and compatible computation are two major characteristics of this paper, which may enhance the study of numerical Cauchy problems forward to a higher and advanced level.     

An optimization technique using the characteristics of genetic algorithm

Optimization problems could happen often in discrete or discontinuous search space. Therefore, the traditional gradient‐based methods are not able to apply to this kind of problems. The discrete design variables are considered reasonably and the heuristic techniques are generally adopted to solve this problem, and the genetic algorithm based on stochastic search technique is one of these. The genetic algorithm method with discrete variables can be applied to structural optimization problems, such as composite laminated structures or trusses. However, the discrete optimization adopted in genetic algorithm gives rise to a troublesome task that is a mapping between each strings and discrete variables. And also, its solution quality could be restricted in some cases. In this study, a technique using the genetic algorithm characteristics is developed to utilize continuous design variables instead of discrete design variables in discontinuous solution spaces. Additionally, the proposed algorithm, which is manipulating a fitness function artificially, is applied to example problems and its results are compared with the general discrete genetic algorithm. The example problems are to optimize support positions of an unstable structure with discontinuous solution spaces.     

Boundary element method for thermoelastoplastic problems

In this paper, we present the boundary integral formulation for inelastic stationary thermoelasticity including thermally induced non-homogeneity. Generally, the unique BEM formulation for crack problems is achieved by using the traction boundary integral equations which are now considered in a non-singular form. Both the two- and three-dimensional boundary value problems are analysed simultaneously. Numerical examples for 2-D problems are presented, in order to illustrate the suitability of this boundary element approach in the inelastic thermoelasticity.     

Advanced Kantorovich method for biharmonic problems

In this paper a method for solving biharmonic problems involving a mixed numerical-analytical approach is described. The algorithm of this method is given and the efficiency of its application for the solution of biharmonic problems is discussed. The recommendations about an application of this method for solving stationary three-dimensional problems in the theory of elasticity are given.     

Tuned test problems for numerical methods in engineering

When numerical methods are applied in engineering, verification is essential. Test problems can help in meeting this requirement. This is especially so when these problems are tuned to the application at hand. Unfortunately, in practice such tuned test problems are not always directly available. For these cases, this paper describes an approach for constructing tuned test problems. The approach may be used on ordinary or partial differential equations, be they linear or non-linear. This is demonstrated on a number of applications drawn from dynamics, solid mechanics, and fluid mechanics. © 1997 John Wiley & Sons, Ltd.     

GEOMETRIC PROGRAMMING WITH SEVERAL DISCRETE VARIABLES: ALGORITHMS EMPLOYING GENERALIZED BENDERS' DECOMPOSITION

Geometric programming problems in which several of the variables are restricted to assume either integer values or one of a set of standard sizes are known as Semi-Discrete Geometric Programming problems. In this paper several variations of Generalized Benders' Decomposition are described for these problems and some computational experience is presented.     

Boundary Integral Equation for Eddy-Current Problems with Dirichlet Boundary Condition

A boundary integral equation (BIE) is developed for the eddy-current (EC) problems with Dirichlet boundary condition by considering the difference between the field without cracks and the one with cracks. Once the field and its normal derivative are given for the structure in the absence of cracks, normal derivative of the scattered field on the surface can be calculated by solving this integral equation numerically. For infinite-domain problems, this equation is more efficient than the conventional BIE due to a smaller computational region needed. Four kinds of two-dimensional EC problems have been solved using this integral equation. The surface impedance for different cases is presented in this paper. Numerical results are compared with analytical solutions and published numerical results. There are good agreements between them. Also, this concept can be extended to three-dimensional problems with other boundary conditions.     

Approaches for Discrete Alternative Multiple Criteria Problems for Different Types of Criteria

In this paper we address two classes of sdiscrete alternative multiple criteria decision making problems: problems in which ordinal and cardinal criteria are simultaneously involved and problems in which only cardinal criteria are involved. We suggest variations of our previously developed ordinal criteria approach [5] and we test the approaches on randomly generated problems. Our evaluation criteria are: the capability of the approach to find a highly preferred alternative and the amount of information required of a decision maker.     

A finite element model for nonlinear shells of revolution

A finite element model for symmetrically loaded shells of revolution is described. The nonlinear geometric effects are accounted for by incrementing loads and iterating for equilibrium. The iteration process also allows for nonlinear materials. The shell model accounts for large strains, large rotations and shear deformation. Three example problems demonstrate the ability of this model to solve linear problems. Also, three example problems demonstrate the versatility and accuracy of this model for nonlinear problems. These nonlinear example problems are an axially loaded cylinder and an internally pressurized spherical shell that have large membrane strains, and a cylinder that deforms into a spherical shape, having large rotations.     

Advanced mesh generation and update methods for 3D flow simulations

Advanced mesh generation and update methods for parallel 3D computation of complex flow problems are presented. The complexities of the class of problems targeted include complex geometries, unsteady behavior, and moving boundaries and interfaces, such as those encountered in fluid-object interactions. Parallel 3D simulation of 1000 spheres falling in a liquid-filled tube, and other computations, are presented in this paper to demonstrate the challenges involved in this class of flow problems and the methods developed to address these challenges.