Load Bearing Polymers used in Orthopaedic Surgery

One of the major contributions to orthopaedic surgery has been the use of ultra-high-molecular-weight polyethylene in prosthetic joint replacements. The part played by this polymer is set in the context of biomechanical requirements. Work dealing with wear found in components of knee prostheses removed from patients is presented, the main mechanism being cold flow followed by abrasive wear. Surface delamination and the effect of inhomogeneous regions are described. Polyacetals, homo and copoly mers are being used as bearing surfaces and the current position is reported. Work in the author's laboratory to develop carbon fibre reinforced plastics is described briefly. The development of Standards is mentioned.     

Carbon biomedical devices

Isotropic pyrolytic carbon (LTI carbon) offers a unique combination of properties that has made it the material of choice for use in the construction of artificial heart valves. The biocompatibility of LTI carbon, in particular its thromboresistance, together with its resistance to degradation by wear and fatigue in the biological environment, has greatly reduced the incidence of thromboembolic complications and mechanical failures of prosthetic valves. Since 1969, more than 200,000 valves that use LTI carbon have been implanted. The morphological and/or surface chemical characteristics responsible for the compatibility of LTI carbon with blood remain unidentified. Its surface energy, greater than 50 ergs/cm², is unusually high for a thromboresistant material, yet LTI carbon surfaces are able to interface with blood through a weakly adsorbed proteinaceous layer without activating clotting via the intrinsic mechanism.The solid carbons have elastic moduli that are in the range often quoted for bone. Thus, for load-bearing applications in dentistry for endosseous dental implants and in orthopedics for joint replacement, the match of moduli provides biomechanical compatibility which can minimize the stress concentrations that often result when stiffer materials such as metals and ceramics are used in bone. The biochemical compatibility and wear resistance of the silicon-alloyed variety of LTI carbon, together with its strength and elastic match with bone, provide an ideal combination of properties for applications in orthopedics as a joint replacement material.Complex shapes not fabricable from isotropic pyrolytic carbon can be fabricated from metals and then coated with a thin, impermeable layer of carbon by vapor deposition. Flexible materials may be obtained by carbon coating thin polymeric sheets or fabrics by vapor deposition or through the use of glassy carbon fibers. The ability of carbon to perform percutaneously is being utilized, for example, in devices used to gain access to the blood stream for dialysis.     

谈陶瓷轴承的应用及市场前景

陶瓷轴承作为一种重要的机械基础件,由于具有金属轴承所无法比拟的优异性能,近年来,在国计民生的各个领域中得到了日益广泛的应用。随着加工技术的不断进步,工艺水平的日益提高,陶瓷轴承的成本不断下降,陶瓷轴承广泛应用的时代已经到来。根据开拓陶瓷轴承是高技术发展的需要,本文阐述了陶瓷轴承的主要用途和应用领域和陶瓷轴承的主要类别;以及陶瓷轴承的主要性能特点;同时指出了陶瓷轴承的市场广阔前景。     

Ceramic-on-ceramic catastrophic liner failure in total hip arthroplasty: Morphological and compositional analysis of fractured ceramic components

Surface bearing of total hip arthroplasty (THA) still is a strong subject of study due to the relatively high rate of failures caused by a multiplicity of factors including surgical technique, patient's attitude, and type/characteristics of the materials used (metal, ceramics, polyethylene) with their specific risk factors. Fractures of the ceramic components are rare but catastrophic events, with many concerns among the orthopaedic surgeons. Such complication is usually evaluated from a clinical viewpoint; this study provides a materials scientist's complementary perspective and comprehensively evaluates the surface and the mechanism of rupture of the ceramic liner in two cases with different ceramics (Biolox Forte and Biolox Delta) after ceramic-on-ceramic THA. The morphological and compositional analyses of the ceramic components were performed by field-emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS), along with macroscopic pictures. The SEM analysis of the ceramic liner showed many wear signs in all directions, while the EDS revealed the presence of titanium near to the fracture border, which might be interpreted as a consequence of the catastrophic contact between ceramic liner and metal back. Biolox Delta and Biolox Forte ceramic liners showed different patterns of fracture and surface modifications that are illustrated and discussed.     

髋关节整体替代陶瓷材料

许多材料在医学领域应用广泛,例如,整体替换硬组织或软组织的元件(如骨盆、骨头、关节、植牙等)、修补、诊断或矫正仪器(如起搏器、心脏阀等)。这些材料不仅要有好的力学性能,还要保持长期稳定,不能与人体相排斥。由于陶瓷材料在生理环境中具有强度高、生物相容性强和稳定性好的优点,人们研究用陶瓷材料替换骨骼。从20 世纪70 年代起,欧洲人用陶瓷组件置换整个髋关节。这些组件主要由氧化铝和氧化锆单体制成。然而,在有水环境中,氧化锆会发生低温降解。目前人们的研究重点在于提高陶瓷组件的强度和耐磨性,同时缩小其尺寸并延长其使用寿命。研究中使用的材料是氧化锆增韧的氧化铝复合陶瓷和其它氧化铝复合陶瓷,不再是单体陶瓷。另外,还可以使用氧化铝和氧化锆功能梯度复合材料。该梯度材料可以利用电泳沉积法(EPD)制得,其表面为纯氧化铝,中心部分为均匀的氧化铝、氧化锆复合材料,中间过渡部分是呈连续梯度渐变的氧化铝、氧化锆复合材料,烧成后会产生剩余热应力。设计这样的梯度结构是为了使复合材料具有最大表面压应力和最小内部张应力,与纯氧化铝组件相比,提高了强度和耐磨性。     

陶瓷轴承应用开启蓝海 产业竞争发展风头正劲

陶瓷材料具有密度小、弹性模量高、线胀系数小、耐磨、耐高温、耐腐蚀等优良性能,成为制造高速精密轴承的理想材料,并且受到了越来越广泛的应用。根据陶瓷轴承的功能及其应用领域,介绍了陶瓷轴承的主要类型及性能特点,论述了国内外陶瓷轴承的产业及市场前景,指出了陶瓷轴承技术的发展趋势。     

An assessment of in vivo failures of alumina ceramic total hip joint replacements

Several cases of alumina ceramic hip replacement failures are reviewed fractographically. Three main findings are illustrated. Firstly, there is evidence that surgeons can damage the femoral head bore surface during surgery. Secondly, three of the failures described are of extended neck designs which are weaker than those of normal or short length in axial laboratory testing. Under physiological loading, such geometry can lead to levering forces, inappropriate localized contact with the metallic stem and stress concentrations. Delayed failure can ensue, with a fracture pattern quite different from that seen in conventional uniaxial testing. Thirdly, while some failures show head bore surfaces which are clean apart from metallic witness marking, others show brown stains and white deposits suggesting poor conformal contact. We suspect either stems become damaged during surgery before mounting the head or entrapment of debris, pointing to handling care and cleanliness varying between hospitals.     

陶瓷材料凸显优势信息产业引领未来

能源、信息、材料是现代科技的三大支柱,新技术的出现有时很大程度上是材料性能的突破而带来的,这是因为新技术的发展往往依赖于新材料来体现它的新性能。随着我国经济一体化的发展,电子陶瓷行业的经济、技术竞争能力将有更大的提高,电子陶瓷市场的消费环境与拥有现状、消费需求潜力、以及电子陶瓷未来的发展趋势成为企业关注的焦点。针对电子...     

Reduced bacterial adhesion on ceramics used for arthroplasty applications

Orthopaedic-implant-related infections are challenging for clinicians: despite progresses in surgical procedures, the mortality rate of patients experiencing periprosthetic joint infections still ranges from 10 to 18%. Generally, infection starts when planktonic bacteria arising from surgery escape immunological surveillance adhering onto implant surface. Bacterial adhesion depends mainly on material’s intrinsic surface features depending on its chemical and physical properties. This study compares materials used for bearings of total hip arthroplasty, advanced ceramics (alumina and zirconia-platelet toughened alumina composites), metals (cobalt–chromium–molybdenum alloy) and polymers (highly cross-linked polyethylene), in terms of wettability and protein adsorption. Materials were infected with Staphylococcus aureus and Staphylococcus epidermidis biofilm for 24 or 48 h. Bacterial adhesion properties were evaluated by means of biofilm viability, morphology, and thickness, in a worst-case surface roughness condition. Thanks to selective protein adsorption, bioceramics reduced bacterial adhesion and subsequent biofilm formation more effectively in comparison with metal and polymer surfaces.     

Joining of Silicon Carbide/Silicon Carbide Composites and Dense Silicon Carbide Using Combustion Reactions in the Titanium–Carbon–Nickel System

A new ceramic joining technique has been developed that utilizes an exothermic combustion reaction to simultaneously synthesize the joint interlayer material and to bond together the ceramic workpieces. The method has been used to join SiC/SiC composites and dense SiC ceramics using TiC-Ni powder mixtures that ignite below 1200°C to form a TiC-Ni joining material. Thin layers of the powder reactants were prepared by tape casting, and joining was accomplished by heating in a hot-press to ignite the combustion reaction. During this process, localized exothermic heating of the joint region resulted in chemical interaction at the interface between the TiC-Ni and the SiC ceramic that contributed to bonding. Room-temperature four-point bending strengths of joints produced by this method have exceeded 100 MPa.     

Insights on Ceramics as Dental Materials. Part I: Ceramic Material Types in Dentistry

Ceramics are widely used biomaterials in prosthetic dentistry due to their attractive clinical properties. They are aesthetically pleasing with their color, shade and luster, and they are chemically stable. The main constituents of dental ceramic are Si-based inorganic materials, such as feldspar, quartz, and silica. Traditional feldspar-based ceramics are also referred to as “Porcelain”. The crucial difference between a regular ceramic and a dental ceramic is the proportion of feldspar, quartz, and silica contained in the ceramic. A dental ceramic is a multiphase system, i.e. it contains a dispersed crystalline phase surrounded by a continuous amorphous phase (a glassy phase). Modern dental ceramics contain a higher proportion of the crystalline phase that significantly improves the biomechanical properties of ceramics. Examples of these high crystalline ceramics include lithium disilicate and zirconia.     

骨科髋膝关节置换术临床路径实施体会

目的总结临床路径在骨科髋膝关节置换术中的实施体会。方法选取我院2009年11月至2010年12月收治的102例实施髋膝关节置换术的患者,按入院的先后顺序随机分为对照组和实验组,对照组仅采用传统模式,实验组在传统模式基础上实施临床路径。统计2组在住院天数、医疗费用、术后首次下床时间、术后首次功能锻炼时间、并发症发生情况以及患者满意度方面的相关数据,并比较其差异。结果所有方面的数据显示,实施临床路径的实验组明显比对照组有优势。结论骨科髋膝关节置换术实施临床路径的效果显著,值得在临床中加以推广应用。     

Determination of Nickel(II) Oxide in Ceramic Pigments by In Situ X-ray Diffraction Quantitative Analysis

Nickel(II) oxide (NiO) still is extensively used as a raw material for the synthesis of traditional ceramic pigments, despite the fact it is potentially carcinogenic. One of the reasons is that, unfortunately, no widely accepted methods exist for its determination in ceramics so far (the main reason being experimental difficulties). Quantitative phase analysis via powder X-ray diffractometry, for example, may fail because of the presence of glass and because NiO diffraction peaks overlap those of spinel in spinel-based pigments. This communication elucidates how to address these experimental difficulties and determine free NiO in the case of black ceramic pigments.     

陶瓷轴承的特性与制造

对工程陶瓷，轴承钢等材料的重要性能进行了对比分析，对陶瓷轴承的生产工艺，检测手段，应用前景进行了介绍，论证了将工程陶瓷用于轴承制造的可行性和重要性。     

氮化硅陶瓷在四大领域的研究及应用进展

氮化硅陶瓷不仅具有较高的力学性能还具有良好的透波性能、导热性能以及生物相容性能,是公认的综合性能最优的陶瓷材料。作为轴承球的致密氮化硅陶瓷广泛应用在机械领域;作为透波材料的多孔氮化硅陶瓷广泛应用在航空航天领域;随着对氮化硅陶瓷材料的深入研究,其在导热性和生物相容性方面的优异特性逐渐被科研工作者认识并得到开发和应用。本文详细阐述了氮化硅粉体的制备方法,并综述了氮化硅陶瓷作为结构陶瓷在机械领域和航空航天领域的研究进展,此外还介绍了其作为功能陶瓷在半导体领域、生物制药领域的研究和应用现状,最后对其未来发展进行了展望。     

Carbon in medical devices

The variability of the crystalline structure of carbon allows a correspondingly wide range of possible properties. By controlling the structure of carbon through processing, as for example in the deposition of carbon in a fluidized bed, it is possible to produce deposits with unique combinations of properties. Certain of these carbons have been found to be extremely useful in prosthetic devices. The isotropic carbons deposited at relatively low temperatures (below about 1500°C), often called LTI carbons, are blocompatible in the broadest sense. They do not induce thrombosis or hemolysis or otherwise affect either the formed or molecular element of blood. They have exceptional wear and fatique properties which are not degraded by the body environment. Accordingly, these carbons are widely used in the construction of prosthetic heart valves.The modulus of elasticity of LTI carbon is unusually low for a material of such strength and falls within the limits reported for the elasticity of bone. This property, together with its ability to interface with both soft and hard tissue without eliciting a foreign body response, makes it possible to produce orthopedic joint replacements that can attach directly to bone without using polymethylmetacrylate bone cement.Using special vacuum deposition techniques, it is possible to deposit thin, impermeable isotropic carbons that mimic the structure and properties of the LTI carbon. Materials such as polymers and fabrics can be coated with such carbons and these coatings are finding use on vascular grafts, heart valve sewing rings, percutaneous access devices, and tendon and ligament replacements.Other forms of carbons, e.g. fibers and fiber composites, are currently being used clinically in orthopedic surgery. The impact of carbon on current replacement surgery and some possibilities for future applications will be described.     

氮化硅陶瓷的应用和酸腐蚀研究进展

综述了氮化硅陶瓷的三种工业应用,即氮化硅陶瓷轴承球、氮化硅涡轮转子、铝冶金氮化硅陶瓷部件,以及氮化硅在H2SO4,HN03,HCl,HF等酸溶液及高温SO2和HCl气体中的腐蚀行为,对其腐蚀机理进行总结,并提出今后提高氮化硅陶瓷抗腐蚀性能的研究重点。     

含钾砂页岩除铁提质及陶瓷应用试验研究

分析了含钾砂页岩中铁的赋存状态,开展含钾岩石除铁提质试验,并对除铁粉料应用于陶瓷原料进行试验研究。结果表明,采用磁选-酸浸工艺,在磨矿细度为-74 μm占50%(质量分数),磁场强度为190 mT,盐酸浓度为20%(质量分数),浸出温度为90 ℃的最佳条件下,除铁粉料中全铁含量可降低为0.13%(质量分数),K₂O和Na₂O总含量提高至11.00%(质量分数),含量符合陶瓷用钾长石Ⅰ级品要求。除铁粉料在陶瓷胚体成型试验中易于成型,烧成温度范围宽,成品率高,可替代长石作为陶瓷原料使用,开拓了含钾砂页岩作为陶瓷原料使用的新方向。     

Preparation and properties of ceramics from a zirconia nanopowder

The possibilities of preparing ceramics from a zirconia nanopowder have been investigated. A ceramic material with a fine-grained (of the order of 2–3 μm) structure is synthesized. A ceramic material with zircon predominant is produced using a silica nanopowder (tarkosil). The properties of the initial nanopowder and the ceramic material synthesized are investigated using transmission electron and scanning electron microscopies. The microhardness and strength of the ceramics are determined.     

Evaluation of Silicon-Nitride Ceramic Valves

Silicon-nitride ceramic valves can improve the performance of both light- and heavy-duty automotive engines because of the superior material properties of silicon nitrides over current metal alloys. However, ceramics are brittle materials that may introduce uncertainties in the reliability and durability of ceramic valves. As a result, the lifetime of ceramic valves are difficult to predict theoretically due to wide variations in the type and distribution of microstructural flaws in the material. Nondestructive evaluation (NDE) methods are therefore required to assess the quality and reliability of these valves. Because ceramic materials are optically translucent and the strength-limiting flaws are normally located near the valve surface, a laser-scatter method can be used for NDE evaluation of ceramic valves. This paper reviews the progress in the development of this NDE method and its application to inspect silicon-nitride ceramic valves at various stages of manufacturing and bench and engine tests.