摘要:

AbstractAlthough there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate.The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues.The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, toin vivoambulation. The manufacturing and machining processes showed a statistically significant (P≤ .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock.The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate. © 1993 John Wiley&Sons, I

ISSN:0021-9304    

DOI:10.1002/jbm.820271102

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe Scanning Electrochemical Microscope (SECM) is a nonoptical scanning microscopic instrument capable of imaging highly localized electrical currents associated with charge transfer reactions on metallic biomaterials surfaces. The SECM operates as an aqueous electrochemical cell under bipotentiostatic control with a microelectrode and sample independently biased as working electrodes. Microelectrode current and position is recorded as it is scanned very near a metallurgically polished planar sample surface. To date, the SECM has imaged metallic biomaterials surfaces in oxygen reaction rate imaging (ORRI) and ion release and deposition imaging (IRDI) modes. In ORRI, sample and microelectrode are biased at sufficiently negative potentials to reduce absorbed oxygen. As the microelectrode scans areas of active oxygen reduction, localized diffusion fields with decreased oxygen solution concentrations are encountered and resultant decrements in microelectrode current are observed. In IRDI mode the sample is positively biased and the microelectrode is negatively biased. The microelectrode detects anodic dissolution products with highest currents being observed over the most active areas. Performance of the SECM has been evaluated on Ni minigrids, γ‐1 Hg‐Ag dental amalgam crystals, and sintered beads of Co‐Cr‐Mo alloy which represent significantly different geometries and corrosion processes to help demonstrate the potential of this instrument. The SECM is a valuable tool for imaging microelectrochemical processes on the surfaces of metallurgically polished metallic biomaterials samples and a wide variety of other surfaces of biological interest where charge transfer reactions occur. The SECM allows selective biasing of metallic biomaterials surfaces and Faradaic reactions can be selectively imaged while the surface is in the active, passive, or transpassive state. © 1993 John Wiley&

ISSN:0021-9304    

DOI:10.1002/jbm.820271103

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThere is a need for viable small diameter vascular grafts, the luminal surface of which could be seeded by endothelial cells (ECs) to prevent thrombosis. In order to select candidates for EC seeding before implantation, thein vitrocytocompatibility of three different Pellethanes® (polyetherurethanes) using human ECs was investigated. The methodology included two stages depending on either direct contact between cells and materials or contact between cells and material extracts, obtained under standardized conditions. By the latter method, we observed a cytotoxic effect on cell growth with 2363‐55 D Pellethane extract at a 50% (v/v) concentration in the nutrient medium, likely provoked by leachables and correlated with the lowest levels of tPA, PAI1, and vWF antigens in the supernatants. By the former method, we studied EC attachment and growth. Morphology was studied by classical means and completed by scintigraphy and microautoradiography after111Indium‐labeling of the EC monolayer. Differentiation was determined by the release of vWF antigen and measurement of vWF activity (multimeric organization) after human thrombin stimulation. Despite an inhibition of proliferation for both 55 D and 75 D types (compared to the control), a functional monolayer of ECs was obtained on 75 D. Pellethane 75 D could be the best support forin vitroendothelialization. © 1993 John Wiley&Sons

ISSN:0021-9304    

DOI:10.1002/jbm.820271104

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractImmobilized polyethylene glycol (PEG) reduced the amount of bovine serum albumin (BSA) adsorbed on polyvinyl alcohol (PVA) hydrogel, but did not reduce the platelet reactivity of the hydrogel surface. PEG, molecular weight (MW) 2000 or 5000, with or without a monomethoxy end group, was covalently bound to glutaraldehyde‐crosslinked PVA either through a cyclic acetal or an urethane functional group with a surface coverage of 70% (as measured by x‐ray photoelectron spectroscopy [XPS]). Immobilization of monomethoxy‐PEG via a cyclic acetal reduced BSA adsorption to PVA from 11 ± 2 nmol/m2to 3.9 ± 0.3 nmol/m2and 3.3 ± 0.3 nmol/m2for MW 2000 and 5000, respectively. Similarly, urethane bound PEG reduced adsorption to 3.5 ± 1.6 nmol/m2for MW 2000 and 5.4 ± 1.0 nmol/m2for MW 5000. Whole blood clotting times of PVA (using a Chandler loop) were not affected by covalently linked PEG, although the initial rate of thrombin generation at the surface, measured using a fluorogenic substrate, was marginally reduced; a rate constant of 4.2 ± 0.1 cm/sec and 3.5 ± 0.1 cm/sec were obtained for MW 2000 and 5000, respectively, compared to 5.6 ± 1.0 cm/sec for PVA.Ex vivoevaluation using a canine arteriovenous shunt revealed that the hydrogel, with or without bound PEG, reduced circulating platelet levels by 35‐70% after 4 days. The initial fractional rate of platelet destruction determined from measurement of platelet cyclooxygenase activity, indicated that cyclic acetal or urethane bound PEG of either molecular weight had no effect on platelet consumption produced by PVA. The PEG hypothesis at least as it relates to platelet interactions may need to be evaluated further in the light of these results. © 1993 John

ISSN:0021-9304    

DOI:10.1002/jbm.820271105

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe passive biocompatibility of silicon‐based electrode arrays was studied in feline cortical tissue. Three types of arrays were used: uncoated, coated with polyimide, and coated with polyimide over an adhesion promoter. Fifteen arrays were implanted for 24 h to determine early tissue reaction to the implantation procedure, and twelve arraays were implanted for 6 months to determine structural and material biocompatibility. Edema and hemorrhage were present around the short‐term implants, but involved less than 6% of the total area of the tissue covered by the array. With chronic implants, leukocytes were rarely present and macrophages were found around roughly one‐third of the tracks. Remnants of foreign material from the electrodes could be identified in less than 10% of the tracks. Gliosis was found around all tracks, forming an annulus between 20 and 40 μm thick. A capsule was not always present, and never exceeded a thickness of 9 μm. These results suggest that the implantation procedure produces limited amounts of tissue damage, and that the arrays are biocompatible. However, the arrays insulated with polyimide over a primer had significantly greater involvement of macrophages, gliosis, and capsule formation than uncoated arrays and arrays insulated with polyimide without printer, perhaps indicating a reaction to aluminum oxide in the primer. © 1993 John Wiley&S

ISSN:0021-9304    

DOI:10.1002/jbm.820271106

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractBioactive materials such as hydroxyapatite ceramics (HA) are known to show a stable interfacial bond with tissues (the bone bonding property has been especially well documented). However, the biological phenomenon on the material surface that evoke bone bonding is not well documented. To address this issue, composites of porous HA and rat marrow cells were implanted into ectopic (subcutaneous) sites. At 3 weeks after implantation, active osteoblasts lining the HA surface initiated bone formation, primarily as mature bone (lamellar type). Gene expression study using Northern blot analysis of the composites showed that alkaline phosphatase (ALP) and bone Gla protein (BGP) mRNAs began to appear at 2 weeks and the level of BGP mRNA at 4 weeks was comparable to that of cancerous bone. However, HA implantation without marrow cells did not show bone formation and neither BGP nor ALP mRNA were detected. These results indicate that the HA surface is able to support cell differentiation (osteoblastic phenotype expression of marrow stromal stem cells), as well as cell coordination resulting in mature bone formation that bonds to the HA. © 1993 John Wiley&Sons, Inc

ISSN:0021-9304    

DOI:10.1002/jbm.820271107

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe hydrolytic degradation of poly(DL‐lactic acid) in an aqueous environment in which hydroxyl radicals have been generated has been investigated. Different methods (gel permeation chromatography, differential scanning calorimetry, and scanning electron microscopy) were employed to study the mechanisms of degradation of this amorphous physiologically absorbable polymer. The data indicated that the hydroxyl radical is likely to be a significant factor in the degradation of this polymer. © 1993 John Wiley&Sons, I

ISSN:0021-9304    

DOI:10.1002/jbm.820271108

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractMechanical stimulation has been shown to affect the differentiation and development of mesenchymal tissue. In the present study, we compared the histological and histomorphometric results of tissue ingrowth into micromotion chambers that were moved at 0 cycles per day, 20 cycles once per day, and 20 cycles twice per day over 20–30 sec, for 3 weeks. In each case, a chamber having a 1 × 1 × 5 mm square‐holed groove for tissue ingrowth was used. The total amplitude of motion was 0.75 mm. Histological sections from nonmoved chambers contained extensive trabecular bone, embedded in a fibrovascular stroma. Histomorphometric analysis disclosed that bone comprised a mean of 31 ± 2% (mean ± SEM) of the ingrown tissue. Twenty movements per day appeared to further stimulate bone ingrowth (46 ± 5%). Extensive ingrowth of more immature woven and trabecular bone was noted in a more cellular stroma. In general, increasing the degree of micromotion to 20 movements twice per day resulted in a decreased amount of bone formation (19 ± 7%). In several of these specimens, little or no bone could be found. These experiments have demonstrated that, for the parameters chosen in this study, a short daily period of low frequency, micromotion may facilitate bone ingrowth; however, when the same motion is delivered twice daily, bone ingrowth is depressed. Thus a “window” of externally applied strain appears to exist, which may facilitate or discourage tissue differentiation to bone. © 1993 John W

ISSN:0021-9304    

DOI:10.1002/jbm.820271109

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe aim of this study was to alter the hydrolytic degradation property of synthetic absorbable suture fibers so that their mass loss would occur at a shorter time without significantly compromising their tensile strength loss profile. A two‐step treatment concept (γ‐irradiation followed by Parylene plasma deposition) was introduced for achieving this aim. Vicryl® and Maxon® were used as the model compounds to test this new concept. After the treatment, thein vitrohydrolytic degradation properties of Vicryl and Maxon were evaluated by weight loss, tensile breaking strength, heat of fusion and melting temperature, intrinsic viscosity, surface wettability, and surface morphology.The results suggested that γ‐irradiation at a dosage level between 0.2–2.0 Mrad for Vicryl sutures and about 2.0 Mrad for Maxon sutures were the most effective dosages to accelerate the suture mass loss. The subsequent Parylene plasma deposition treatment statistically significantly improved the retention of tensile strength for both γ‐irradiated Vicryl and Maxon sutures and hence counteracted the undesirable γ‐irradiation induced acceleration of tensile strength loss. However, this second‐step Parylene plasma treatment extended the suture mass loss to longer periods. These findings were consistent with the observed surface wettability, surface morphology, intrinsic viscosity, and thermal properties. A thin hydrophobic Parylene skin layer wrapped around a suture was responsible for the slower rate in mass and strength loss. This outer skin layer acted as a barrier to not only water but also degradation fragments. © 1993

ISSN:0021-9304    

DOI:10.1002/jbm.820271110

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractPolyetherurethanes (PEUs) based on polytetramethylene oxide (PTMO) as the polyol, and derivatized with propyl sulfonate functionality, have previously been shown to possess antithrombotic properties. In this article, the bulk physical properties of sulfonated and nonsulfonated polyurethanes containing either polyethylene oxide (PEO) or PTMO as the soft segment are studied. Thein vitroshape‐change of platelets in contact with these surfaces, and theirex vivobloodcontacting response are also investigated. It was found that PEO‐base was physically weaker than PTMO‐base, which is attributed to a lower degree or phase separation in the former. In the dry state, sulfonation enhanced the physical properties for PTMO‐containing polyurethane (PTMO‐SO3–0.20), but weakened the PEO‐containing polyurethane (PEO‐SO3–0.15).In vitroplatelet spreading studies showed the lowest degree of platelet spreading and also the lowest platelet density on PEO‐base, while platelet spreading and density on the other three materials and polyethylene (PE) was greater. The thromboresistance of these materials was evaluated using a canine arteriovenous series shuntex vivo.It was determined that PTMO‐SO3–0.20 was the least thrombogenic, followed by both PEO‐base and PEO‐SO3–0.15, and that PTMO‐base was the most thrombogen

ISSN:0021-9304    

DOI:10.1002/jbm.820271111

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY