ISSN:0021-9304    

DOI:10.1002/jbm.820231302

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820231303

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe purpose of my column is to provide readers with current information on biomaterials‐related standards produced by both private groups and government agencies, and standards‐related activities. Standards are descriptive documents given official status by their producers and, in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to all members of any and all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.And last, a caveat—since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in January,

ISSN:0021-9304    

DOI:10.1002/jbm.820231304

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractTi4+and V5+ions were studied in two biologically relevant in vitro test systems to determine their effect on hydroxyapatite (HA) formation. System 1 involved direct HA precipitation from solution, and system 2 dealt with the growth of HA seed crystals. The experiments were carried out in a pH‐stat by continuously recording NaOH uptake, which follows HA formation kinetics, at pH 7.4, 37°C, and 0.15 MNaCl. In systems 1 and 2, Ti decreased HA formation kinetics in a dose‐related manner without delaying the onset of HA formation. For V, the rate of HA proliferation decreased in system 1 in a dose‐related manner, but the curves displayed a complicated shape. In system 2, V brought about a decrease in the HA seeded growth rate. Previous work has shown that A1 blocks HA proliferation by adsorbing to active growth sites on the surface of HA crystals. By contrast, in this study V was found not to be adsorbed to the surface of HA. The mechanism of action of V probably involves the poorly understood hydrolysis and solution complex formation chemistry of the metal ion. We have shown here that V ions form V‐PO4complexes in solution in the HA formation systems; undoubtedly these are involved in the mechanism of V inhibition of HA formation. On the other hand, Ti was shown to bind to the surface of HA crystals in this study, which means that the ion may poison active crystal growth sites, as does aluminum. Ti‐6Al‐4V alloy is widely used in cementless total hip implants. Previous studies have shown that Ti concentrations 10 to 100 times higher than used here accumulate in osseous tissues around porous Ti implants in dogs 6 to 12 months after implantation. Ions leaching out over long periods of time into the implant interface could interfere with the normal osteoid mineralization and remodeling processes of bone in that region, which would result in subsequent loosening of the implant. This research suggests that furtherin vitroand animal studies should be carried out to determine the extent of Ti and V ion leaching from implants and their effect on tissue mi

ISSN:0021-9304    

DOI:10.1002/jbm.820231305

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA controlled‐release delivery vehicle for water‐soluble osteogenic proteins from demineralized bone matrix was constructed using purified type I collagen. The water‐soluble proteins were isolated from a 4 M GdnHCl extract of bone matrix. Although the water‐soluble proteins were capable of inducing cartilage formationin vitro, they were incapable of inducing cartilage or bonein vivowhen implanted intramuscularly into mice in the absence of an appropriate delivery vehicle. The collagen‐based delivery vehicle alone was also incapable of inducing osteogenesisin vivo. However, when the water‐soluble proteins were incorporated into the delivery vehicle, the combination was capable of inducing cartilage and bone 76% of the time. These results demonstrate that it is possible to formulate a controlled‐release delivery vehicles for soluble bioactive factors which upon release interact with local res

ISSN:0021-9304    

DOI:10.1002/jbm.820231306

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe usefulness of patent literature for research and development is mostly unknown. Therefore a specific patent retrieval has been carried out concerning calcium phosphate‐containing biomaterials. This research field includes chemical, medical, and engineering problems and is of importance to the development of bioactive materials for bone replacement. The preliminary work includes information on the characteristics and the availability of patent literature as well as about patent classification systems according to which the documents are filed in patent collections. By reading the non‐patent literature searching questions can be formulated. The proper patent retrieval starts with the study of secondary literature especially that inChemical Abstracts, which report on patents since 1907. The structure ofChemical Abstracts, their indexes and sections help to find relevant patents of chemical or chemical engineering contents fast and inspire to read patents of bordering areas. This retrieval fromChemical Abstractsled to 171 patents disclosed 1975–1985 and to 95 patents disclosed in 1986; the latter are listed in a table. The contents of the abstracts inform on the research activity and help to reduce time and effort for a continuation of the retrieval in a patent collections or dat

ISSN:0021-9304    

DOI:10.1002/jbm.820231307

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractClinical failures of central nervous system fluid shunts remain a vexing problem. Attributed largely to infectious and technical etiologies, it has been hypothesized recently that inflammatory mechanisms may play a role in this clinical phenomenon. In order to obtain morphologic evidence for this hypothesis, a study of failed shunts was performed. Twenty‐five of 57 sequentially removed CNS fluid shunt assemblies or components over the course of 18 months contained sufficient intraluminal tissue to allow a histomorphologic assessment. Tissue was removed from either the intraventricular or intraperitoneal portion and examined with routine light microscopical and histochemical techniques to assess the degree of cellularity, composition of the cells, presence of debris, and organisms. Morphologic findings were correlated with the clinical courses and microbiological cultures. Data were analyzed nonparametrically using the χ2test. There was a substantially significant association between repeated failures and non‐infectious obstructions. Eight demonstrated evidence of active inflammatory processes; and although not statistically significant, the presence in 3 cases of giant cells, macrophages, lymphocytes, and eosinophils all suggestive of a hypersensitivity reaction correlated with the occurrence of culture negative clinical failures. These morphologic findings will stimulate further experimental and clinical research into possible inflammatory mediators of shunt fai

ISSN:0021-9304    

DOI:10.1002/jbm.820231308

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractSurfaces of commercial polyurethanes (PUs) were modified by poly(ethylene oxide) (PEO) grafting and/or heparin immobilization for long‐term biomedical applications. PU surfaces were treated with diisocyanate and then reacted with PEO or heparin. The heparin immobilized by various methods on the PU surface was very stable, with concentrations of 1.45–1.84 m̈g/cm2. Surface structure and characteristics of each modified PU were examined by performing the following surface analyses: attenuated total reflection infrared (ATR‐IR), electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM), and dynamic contact angle measurements. The reaction scheme and surface chemical structure of modified PUs were confirmed by ATR‐IR and ESCA, respectively. SEM results showed that the PU‐PEO surface was very smooth and that the smoothness of the heparinized PU surfaces varied, depending upon the solvent and coupling agent used in the process. The hydrophilicity of the surface was significantly increased after PEO grafting or heparin immobilization. Increase in the chain length of the grafted PEO resulted in significant increases in hydrophilicity and surfac

ISSN:0021-9304    

DOI:10.1002/jbm.820231309

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractOrthopaedic internal fracture fixation plates are subjected to combined axial, bending, and torsional loadsin vivowhich can cause screw loosening and implant failure. This paper outlines a relatively simple technique which allows controlled application of combined axial, bending, and torsional loading to examine the loosening rate of cortical screws used to attach these plates. Fiber reinforced polycarbonate rods with a tensile strength similar to that of cortical bone were cut at half their length to simulate fractured tibii. These were compression plated using a standardized technique and placed in a loading fixture. Joint loads at the knee determined from force plate analysis and statics were applied to a plated fixture during testing. The design of the fixture allowed adjustment of the proportion of bending and torsional loads applied to the test samples. It also allowed a reproducible means of applying a predetermined axial, bending, and torsional load. Screw loosening following cyclical loading was evaluated by measuring the amount of angular displacement required to retighten screws to a prescribed torque value. A torque wrench was modified to allow the measurement of these displacements.

ISSN:0021-9304    

DOI:10.1002/jbm.820231310

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe implantable ventricular assist systems currently undergoing clinical readiness testing shuttle the displaced gas between the non‐blood side of the pumping diaphragm and an elastic chamber generally called a “compliance chamber” or variable volume device. The movement of the stored gas allows the pump to fill and empty without compression or expansion of the gas behind the pump diaphragm. The material used for the construction of compliance chambers should be fatigue resistant to withstand the 63 million flexes per year of the blood pump. The material should also be biocompatible and highly impervious to gases. Significant diffusion of gases from the compliance system necessitates external make‐up gases to somehow be added to the internal system. Material selection is complicated by the fact that most fatigue‐resistant elastomers also have high gas permeability. In order to solve this problem, bilayer compliance chambers have been developed using biocompatible and fatigue‐resistant polyolefin rubber comolded with relatively impervious b

ISSN:0021-9304    

DOI:10.1002/jbm.820231311

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY