bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly‐(2‐hydroxyethyl methacrylate) particles for preoprative endovascular occulusion of extensive angiodysplasias
Authors: Horák Daniel , Švec František , Adamyan Arnold A. , Titova Mariya I. , Dan Vasilii N. , Trostenyuk Nadezhda V. , Voronkova Olga S. , Gumargalieva Klara Z. 
Published: May 2005

AbstractThe application of superselective endovascular occlusion in vascular radiology has broadened the scope of possible radical surgery of giant angiodysplasias by reducing considerably the risk of severe haemorrhage during the surgery. Occlusion was performed on 229 patients using spherical and cylindrical particles of porous poly(2‐hydroxyethyl methacrylate). The treatment of a patient suffering from angiodysplasia of the pelvis is described as an example. The first day following endovascular occlusion a hypercoagulation reaction developed, with a decrease of both the level of fibrinolysis and of anticoagulant factors. This was mainly due to a decrease of the level of antithrombin III and activation of the factor XIII indicating a strong tendency of intravascular thrombosis. During the third day, the hypercoagulation reaction increased. However, on the fifteenth day, parameters of the haemostasis system were close to normal values. Only the activity of the factor XIII remained high suggesting the stabilization and the organization of fibrin clot in the embolized blood vessel territory. © 1993 John Wiley & Sons, Inc.
A comparison of peripheral nerve repair using an absorbable tubulization device and conventional suture in primates
Authors: Tountas Chris P. , Bergman Ronald A. , Lewis Terry W. , Stone Harold E. , Pyrek Janine D. , Mendenhall H. Vince 
Published: May 2005

AbstractMedian nerve regeneration was studied in 30 adult primates after repair by microsurgical suture or tubulization with a nonwoven, bioabsorbable, polyglycolic acid device. The two methods were compared electrophysiologically and histologically 6 and 12 months after repair. The electrophysiology included recording of electrically evoked compound action potentials and subsequent determination of threshold, conduction velocity, amplitude, and area above the baseline for each component. Measurements were obtained before nerve transection and at the time of biopsy by stimulating both proximal and distal to the transection site. Analysis of all electrophysiological parameters revealed no statistically significant differences (p < 0.05) between the two repair techniques. Histopathology included examination of cross sections proximal and distal to the repair sites and longitudinal sections through the coaptation site. End organs (Meissner's and Pacinian corpuscles and muscle) were sectioned to determine the degree of reinnervation. No significant differences between the repair techniques were observed by histological analysis of these sections. These evaluations indicated that the tubulization repair technique produced results comparable to that of the suture technique. © 1993 John Wiley & Sons, Inc.
Testing method for mechanical properties of fibrin glue
Authors: Duda Georg N. , Chao Edmund Y. S. , Grabowski John J. , Taswell Howard F. 
Published: May 2005

AbstractA testing method was developed to evaluate the mechanical properties of a fibrin adhesive in an effort to correlate mechanical strength to fibrinogen content. Autologous fibrin adhesives with varying fibrinogen content were loaded to failure in shear using a mechanical testing machine. The method developed was capable of distinguishing a mechanical strength difference among the three fibrin sample lots used in the study. A number of parameters were evident that could lead to testing variability. The development of a more sophisticated component delivery system would greatly reduce the variability of these parameters and thus, the product reliability. Ultimately, the information gathered from the current and future studies will form a type of quality control standard to directly correlate the percentage of fibrinogen in a particular sample to its adhesive performance. © 1993 John Wiley & Sons, Inc.
Characterization of polyesterurethane degradation products
Authors: Luu H.‐M. D. , Biles J. , White K. D. 
Published: May 2005

AbstractMicrothane foam, a poly(ester)urethane, used as a covering of some breast implants (Meme or Replicon by Surgitek) degrades readily in phosphate buffer pH 7.4 producing multiple unknown products in addition to 2,4 and 2,6 toluenediamine (TDA). The cumulative weight loss of the foam in buffer was 1.5% at 1 week and 2% at 2 weeks. Multiple peak molecular weights from 105 to 665 000 were found in the aqueous foam extracts following 2 weeks of incubation at 37°C using size exclusion chromatography (SEC). TDA was measured in the foam buffer extracts by high pressure liquid chromatography (HPLC) and confirmed by gas chromatography/mass spectroscopy (GC/MS). The total cumulative levels of 2,4 TDA and 2,6 TDA measured were 3 ± 0.65 μg/g of foam and 1.13 ± 0.19 μg/g of foam following 36 days of incubation at 37 °C. Higher amounts, 8.96 μg/g of 2,4 TDA and 3.3 μg/g of 2,6 TDA, were obtained at 50 °C. The cumulative release of TDA in aqueous extracts was found to correlate linearly with time suggesting a slow but continuous production of TDA under neutral conditions. However, less than 0.2 μg/g of TDA was detected as residual TDA in the methylene chloride extracts following up to 60 days at 37 °C. PU foam extracted with methylene chloride under similar conditions showed higher foam weight loss, 4.4 and 5% at 1 and 2 weeks, respectively. The results presented in this study provide further evidence that Microthane undergoes hydrolysis under neutral conditions in aqueous solutions producing TDA and other unknown low molecular weight components and oligomers. © 1994 John Wiley & Sons, Inc.
A method for transmission electron microscopy investigation of the osteoblast/hydroxyapatite interface
Authors: Garvey Brian T. , Bizios Rena 
Published: May 2005

AbstractNeonatal rat calvaria osteoblasts were cultured on hydroxyapatite (as received or relatively‐rough surface and mechanically polished to a 0.3‐m̈m finish) and on glass (reference material) in Dulbecco's Modified Eagle Medium supplemented with 10% fetal bovine serum, 50 μg/mL ascorbic acid, and 10 mM β‐glycerophosphate under standard, sterile, cell‐culture conditions for 1, 3, 7, 14 and 21 days. At the end of the prescribed time periods, the cells were fixed and embedded in resin before removing the material substrates by exposure to acid solutions. Transmission electron microscopic examination of stained, ultrathin sections of the biological structures revealed osteoblast monolayers at 1 day of culture but multilayered cell structures at later time periods (14 and 21 days). The osteoblasts exhibited continuous contact and intimate apposition on polished hydroxyapatite and on glass; in contrast, osteoblasts on as received or rough hydroxyapatite made contact with discrete high points, spanned low regions of the material surface, and did not conform to all substrate contours. An electron dense layer (composed of mucopolysaccharides and proteins) was observed on all substrates tested after 7 days of culture. Collagen fibrils were seen interspersed among the osteoblasts as early as 3 days of culture; at later culture times, (i.e., 21 days) mineralized loci were observed in the extracellular matrix. © 1994 John Wiley & Sons, Inc.
Phosphonated polyurethanes that resist calcification
Authors: Joshi Ravi R. , Frautschi Jack R. , Phillips Richard E. , Levy Robert J. 
Published: May 2005

AbstractCardiovascular implant mineralization involving bioprosthetic materials, such as glutaraldehyde cross linked porcine aortic valves or synthetic materials such as polyurethanes, is an important problem that frequently leads to clinical failure of bioprosthetic heart valves, and complicates long‐term experimental artificial heart device implants. Novel, proprietary, calcification resistant polyetherurethanes (PEU) as an alternative to bioprosthetic materials were the subject of these investigations. A series of PEU was derivatized through a proprietary reaction mechanism to achieve covalent binding of 100 to 500 nM/mg of bisphosphonate (2‐hydroxyethane bisphosphonic acid, HEBP). The stability of HEBP (physically dispersed or covalently bound) verified by studying the release kinetics in physiological buffer (pH 7.4) at 37°C, demonstrated the covalent binding reaction to be stable, efficient, and permanent. Surface (FTIR‐ATR, ESCA, SEM/EDX) and bulk (solubility, GPC) properties demonstrated that the covalent binding of HEBP occurs in the soft segment of the PEU, reduces surface degradation, and does not affect the original material properties of the PEU (prior to derivatization). In vitro calcium diffusion of the derivatized PEU showed a decrease in calcium permeation as the concentration of HEBP covalent binding was increased. In vivo properties of underivatized and derivatized PEU (containing 100 nM of covalently bound HEBP) were studied with rat subdermal implants for 60 days. Explants demonstrated calcification resistance due to the covalently bound HEBP without any side effects. It is concluded that a PEU containing HEBP might serve as a calcification resistant candidate material for the fabrication of a heart valve prosthesis and other implantable devices. © 1994 John Wiley & Sons, Inc.
Physical properties of hyaluronic acid and hydroxypropylmethylcellulose in solution: Evaluation of coating ability
Authors: Silver Frederick H. , LiBrizzi Joseph , Pins George , Wang Ming‐Che , Benedetto Dominick 
Published: May 2005

AbstractHyaluronic acid (HA) and hydroxypropylmethylcellulose (HPMC) in buffered saline are “viscoelastics” used in ophthalmic surgery to prevent mechanical damage to delicate eye structures and to form a protective coating over corneal endothelium.HA is a high molecular weight polysaccharide that exhibits decreasing viscosity at increased shear rates. HPMC is a cellulose derivative that exhibits low surface tension. This study examines the physical properties of HA and HPMC solutions and attempts to correlate these properties with the ability of those macromolecules to coat and protect ocular structures.Results presented in this article suggest mixtures of HA and HPMC exhibit low surface tension and ease of aspiration characteristics that are desired in viscoelastic materials. For this reason a blend of these two macromoleculars offers handling advantages over each of these individual macromolecules. © 1994 John Wiley & Sons, Inc.
Processing and characterization of absorbable polylactide polymers for use in surgical implants
Authors: Andriano Kirk P. , Pohjonen Timo , Törmälä Pertti 
Published: May 2005

AbstractAbsorbable fibers of linear poly‐α‐hydroxy acids have been used successfully in providing temporary scaffolds for tissue regeneration. In some surgical applications, degradation rates for poly(glycolide) (PGA) are too high, but implants of poly(L‐lactide) (PLLA) fibers may degrade too slowly for optimal function. Polymers produced by copolymerization of L‐lactide with varying amounts of D‐lactide may offer an alternative choice for absorbable fiber based implants. Poly(L/D‐lactide) stereocopolymers with L/D lactide molar ratios of 95/5, 90/10, and 85/15 were considered. Melt‐spun/hot‐drawn fibers with L/D molar ratios of 90/10 and 85/15 and draw ratios ranging from 3.0 to 8.9 were further evaluated by mechanical testing, differential scanning calorimetry, birefringence, x‐ray diffraction, and in vitro exposure to pH 7.4 phosphate buffered saline at 37°C. Fabrication was reproducible and results indicated that tensile strength, modulus, and birefringence all increased with increasing draw ratio up to a draw ratio of 6.7 and declined thereafter; elongation to failure decreased for the entire range studied. For fibers with a draw ratio of 6.7, there was a 10% relative difference in crystallinity between the 90/10 and 85/15 lactide fibers (90/10 was higher). Wet strength retention after 12 weeks in vitro exposure was approximately 10% for the 90/10 fibers and 30% for the 85/15 fibers. The intermediate wet strength retention of lactide stereocopolymer fibers when compared to reported values for PGA and PLLA fibers, suggests these materials may be useful in absorbable surgical implants for tissue repair and regeneration. © 1994 John Wiley & Sons, Inc.
Six bioabsorbable polymers: In vitro acute toxicity of accumulated degradation products
Authors: Taylor M. S. , Daniels A. U. , Andriano K. P. , Heller J. 
Published: May 2005

AbstractBioabsorbable polymer implants may provide a viable alternative to metal implants for internal fracture fixation. One of the potential difficulties with absorbable implants is the possible toxicity of the polymeric degradation products especially if they accumulate and become concentrated. Accordingly, material evaluation must involve dose–response toxicity data as well as mechanical properties and degradation rates. In this study the toxicity and rates of degradation for six polymers were determined, along with the toxicity of their degradation product components. The polymers studied were poly(glycolic acid) (PGA), two samples of poly(L‐lactic acid) (PLA) having different molecular weights, poly(ortho ester) (POE), poly(ϵ‐caprolactone) (PCL), and poly(hydroxy butyrate valerate) (5% valerate) (PHBV). Polymeric specimens were incubated at 37°C in 0.05 M Tris buffer (pH 7.4 at 37°C) and sterile deionized water. The solutions were not changed during the incubation intervals, providing a worst‐case model of the effects of accumulation of degradation products. The pH and acute toxicity of the incubation solutions and the mass loss and logarithmic viscosity number of the polymer samples were measured at 10 days, 4, 8, 12, and 16 weeks. Toxicity was measured using a bioluminescent bacteria, acute toxicity assay system. The acute toxicity of pure PGA, PLA, POE, and PCL degradation product components was also determined. Degradation products for PHBV were not tested. PGA incubation solutions were toxic at 10 days and at all following intervals. The lower molecular weight PLA incubation solutions were not toxic in buffer but were toxic by 4 weeks in water. The other materials did not produce toxic responses during the 16‐week exposures. The degradation products components in order from most toxic to least toxic are: lactic acid (PLA), ϵ‐caproic acid (PCL), glycolic acid (PGA), cyclohexane dimethanol (POE), propionic acid (POE), 1,6 hexane diol (POE), pentaerythritol dipropionate (POE), and pentaerythritol (POE). © 1994 John Wiley & Sons, Inc.
Creep behavior of hand‐mixed simplex P bone cement under cyclic tensile loading
Authors: Verdonschot Nico , Huiskes Rik 
Published: May 2005

AbstractAcrylic cement, used for the fixation of total hip replacements and other orthopedic implants, is a subject of renewed scientific interest as a result of recent hypotheses about dynamic, longterm mechanical failure mechanisms suspected to play a role in prosthetic loosening. Little is known, however, about the long‐term mechanical behavior of cement. In this study, the dynamic creep deformation of hand mixed acrylic cement was examined in laboratory tests. Strain patterns found represented the familiar creep process consisting of a primary, a secondary, and a tertiary creep phase. Specimens dynamically loaded with a maximum stress of 3 MPa from 0 were subject to creep of about 50% of the elastic strain after 250 000 loading cycles. A linear relationship between the logarithmic values of the creep‐strain and the number of loading cycles was found. Specimens exposed to higher loads showed significantly higher creep‐strains. No relationship could be established between the strain levels and the porosity of the specimens. Specimens dynamically loaded with a maximal stress of 7 or 11 MPa from 0 failed during the tests. The number of loading cycles to failure was similar to fatigue strength data reported in earlier literature. © 1994 John Wiley & Sons, Inc.
Torsional properties of healed canine diaphyseal defects grafted with a fibrillar collagen and hydroxyapatite/tricalcium phosphate composite
Authors: Zardiackas Lyle D. , Teasdall Robert D. , Black R. John , Jones G. Scott , St. John Kenneth R. , Dillon Lance D. , Hughes James L. 
Published: May 2005

AbstractThe need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFT15), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFT15 material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFT15 had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFT15. The final conclusion is that in this model, grafting with COLLAGRAFT15 provided torsional properties at one year postoperatively at least equivalent to autogenous bone. © 1994 John Wiley & Sons, Inc.
Fretting corrosion accelerates crevice corrosion of modular hip tapers
Authors: Brown S. A. , Flemming C. A. C. , Kawalec J. S. , Placko H. E. , Vassaux C. , Merritt K. , Payer J. H. , Kraay M. J. 
Published: May 2005

AbstractThe use of multiple‐component systems in orthopedic surgery gives the surgeon increased flexibility in choosing the optimal implant, but introduces the possibility of interfacial corrosion. Such corrosion could limit the longevity of prostheses due either to tissue reactions to corrosion products, or to device failure. The incidence and nature of corrosion of modular total hips was evaluated in a consecutive series of 79 retrieved implants from University Hospitals of Cleveland. Surfaces were examined with stereo‐ and scanning electron microscopy. Several laboratory studies were undertaken to examine mechanisms that might contribute to the initiation of corrosion. The first set of experiments investigated the effect of head neck extension; the second study looked at the effect of material combinations on fretting corrosion and crevice corrosion. Analysis of retrieved implants demonstrated that fretting corrosion played a major role in the initiation of interface corrosion, and that a correlation existed between corrosion and length of neck extensions. Laboratory studies showed that longer head neck extensions may be more susceptible to fretting corrosion because of an instability at the interface. Short‐term mixedmetal corrosion studies demonstrated that the coupling of cobalt and titanium alloys did not render the interface more susceptible to corrosion. It is hypothesized that fretting corrosion contributes to the initiation of modular interface corrosion, and that the problem can be reduced by design changes that increase the stability of the interface. © 1995 John Wiley & Sons, Inc.
Fibroblast seeding and culture in biodegradable porous substrates
Authors: Rivard Charles‐Hilaire , Chaput C. J. , DesRosiers E. A. , Yahia L'H. , Selmani A. 
Published: May 2005

AbstractA natural poly(hydroxybutyrate‐co‐9% hydroxyvalerate) copolyester was processed into a three‐dimensional porous foam structure by salt leaching/solvent casting with previously sieved sodium chloride salts. Laboratory‐built P(HB‐9% HV) foams and commercial collagen sponges were cut into small rectangular specimens, sterilized, and prewetted using ethanol, rinsed with Dulbecco's minimum essential medium + 10% serum culture media, and seeded with fibroblasts isolated from canine anterior cruciate ligaments. The fibroblast cultures into such porous substrates were performed from 0 to 35 days by incubation (5% CO2) at 37°C. It demonstrated that the P(HB‐HV) sustained a cell proliferation rate similar to that observed in collagen sponges, up to at least 35 days, with a maximal cell density on the day 28 in culture. On the other hand, the P(HB‐HV) materials kept their structural integrity during the culture period while the collagen foams contracted greatly. Further, the total protein production after 4 weeks in culture was found to be twice as high (190 ± 10%) in the P(HB‐9% HV) foam than in the collagen foam. Porous P(HB‐HV) materials appear to be adequate polymeric substrates for cell cultures. However, further evaluations are still required to confirm such preliminary results. © 1995 John Wiley & Sons, Inc.
Innovations in acrylic bone cement and application equipment
Authors: Kindt‐Larsen Ture , Smith Daniel B. , Jensen Jørgen Steen 
Published: May 2005

AbstractA new bone cement was developed with the purpose of reducing the adverse biological effects during cementation of implants. This bone cement is characterized by lower exotherm, low release of monomer, low residual content of monomer, and retained physical properties. The essential innovation was substitution of half of the methylmethacrylate (MMA) in the monomer with long chain, high molecular weight, less volatile, and less soluble methacrylates (n‐decylmethacrylate, isobornyl‐methacrylate), as well as alteration of the accelerator system to a mix of dihydroxypropyl‐p‐toluidine and N,N‐dimethyl‐p‐toluidine. The powder contains butyl‐methacrylate‐MMA copolymers. These measures lower the glass‐transition temperature, and permit more complete mixing in an integrated package, mixing, and delivery system consisting of a vacuum packed, double chamber pouch. The porosity was reduced to about 2% and the largest voids measured 0.1 mm. The polymerization exotherm was reduced to 58 °C. The compressive strength was 82 MPa, the four‐point bending strength 55 MPa, the flexural modulus 2.24 GPa, the tensile strength 32 MPa, and the shear strength 36 MPa. The fracture toughness was 0.89 MPa √cm. These mechanical properties together with the fatigue life were on level with manually mixed, conventional PMMA bone cements. © 1995 John Wiley & Sons, Inc.
Effects of sublethal metal ion concentrations on osteogenic cells derived from bone marrow stromal cells
Authors: Thompson Gary J. , Puleo David A. 
Published: May 2005

AbstractIons released from implant surfaces are suspected of playing some role in osteolysis surrounding metal prostheses. To understand how ions may affect osteogenesis, previous work exposed osteogenic cells to metal ions to study acute cytotoxic responses. The purpose of this study was to assess the long‐term effects of sublethal ion concentrations on osteogenic cell proliferation and function. Bone marrow stromal cells were harvested from juvenile rats and exposed to solutions of ions associated with Co‐Cr‐Mo and Ti‐6Al‐4V implants. Cells were cultured for up to 4 weeks and assayed for total protein, alkaline phosphatase, osteocalcin, and calcium. Other than V+5, none of the ions affected cell proliferation, indicating that the chosen concentrations were sublethal as desired. V+5 elicited delayed gross toxicity not previously observed during acute experiments. At the chosen concentrations, Co+2, Cr+6, Mo+6, and Co‐Cr‐Mo alloy elicited little effect on cell proliferation and moderate effects on matrix mineralization. Cultures exposed to Ti+4, Al+3, and Ti‐6Al‐4V alloy also showed no decrease in cell number, but did show near total suppression of osteocalcin secretion and matrix mineralization. These results suggest that ions released from Ti alloy implants may interfere with osteoblastic cell differentiation, contributing to periprosthetic osteolysis by impairing normal osteogenesis. © 1995 John Wiley & Sons, Inc.