bluuebunny/crossref_metadata_2025_split huggingface dataset:
A simple in vitro screening test for blood compatibility of materials
Authors: Kambic Helen E. , Kiraly Raymond J. , Nosé Yukihiko 
Published: December 2004

AbstractAn in vitro closed‐cell kinetic blood‐coagulation test was developed and used to evaluate the blood compatibility of materials. The test compares the clot formation rate on a test surface to that of a control material, Silastic. This method avoids anticoagulants, blood flow variations, and the exposure to air and other foreign surfaces. Eight pairs of cells are sequentially evaluated as to the weight of thrombus formed, the amount of unclotted blood, and the reduction in platelet count of the blood exposed to both the test materials and the control. These data are used to calculate a relative index whereby materials can be rated quantitatively as to the rate of clot formation on their surface. The order of decreasing clot formation on one group of materials studied was as follows: biolized (Imai et al., Trans. Amer. Soc. Artif. Int. Organs, 17, 6, 1973) poly(ether urethane), segmented polyurethane, formaldehyde‐treated pericardium, Hydron, glutaraldehyde‐treated pericardium, biolized natural rubber, Hexsyn, heparinized natural rubber, Silastic, and natural rubber. Urethane and aldehyde‐treated natural tissue had a lower percentage of red thrombus formation. These results generally correlate with in vivo observations.
Design and biomechanical evaluation of a cementable endosteal blade implant
Authors: Pugh James , Weiss Charles , Weiss Fredric , Malkin David 
Published: December 2004

AbstractA cementable endosteal blade implant has been developed and evaluated. Inherent in the design are the following factors: minimization of stress concentrators, ease of implantation, and high resistance to loosening. Other potential advantages of this design as compared with conventional endosteal blade implants include reduced hazards of postoperative infection and reduced likelihood of metallic corrosion.Six conventional endosteal implants and six cementable implants were installed in steer mandibles using standard dental surgical techniques and Simplexbrand methyl methacrylate bone cement. They were loaded in uniaxial compression at a loading rate of 0.0122 in./min. The stiffness (S), deformation at 900‐lb load (D900), proportional limit (PL), and load at 0.04 in. deformation (L0.04) were calculated for each test.The cementable design showed a twofold increase in stiffness, only 17% of the deformation at 900 lb, more than twice the proportional limit, and at least twice the load at 0.04 in. deformation when compared with similar values for the conventional endosteal implants.This study reveals that, in addition to being unstable in bone, conventional endosteal implants are also unstable when used with acrylic bone cement. The new design should eliminate most of the problems associated with endosteal blade implantation.
Bone growth into porous high‐density polyethylene
Authors: Spector M. , Flemming W. R. , Kreutner A. , Sauer B. W. 
Published: December 2004

AbstractThe purpose of this study was to delineate the process by which bone comes to fill the pores of porous high‐density polyethylene (PHDPE) implants. PHDPE (450μ pore size) pellets 4 mm in diameter and 1 cm long were implanted into the femurs of dogs. A bone biopsy procedure was utilized to obtain PHDPE pellets implanted for periods of 3 days through 8 weeks. A one‐year biopsy specimen taken from the PHDPE coating on the stem of a canine total‐hip prosthesis was also studied. The results demonstrated that significant amounts of bone formed within the PHDPE pellets as early as 14 days after implantation. Bone was identified throughout the specimens after 4 weeks. After 6 weeks, the tissue in the implants consisted of well‐developed lamellar bone spicules and healthy hematopoietic marrow. Scanning electron microscopy was utilized in conjunction with light microscopy and microradiography to study the ultrastructural features of the bone ingrowth process.
Structure and function of the human patella: The role of cancellous bone
Authors: Townsend P. R. , Miegel R. E. , Rose R. M. , Raux P. , Radin E. L. 
Published: December 2004

AbstractTotal joint and other prostheses often require the removal and replacement of considerable quantities of cancellous bone, and often are anchored in place by grouting into cancellous bone. Thus, a possible source of failure or loosening of many types of prostheses may be rooted in the lack of understanding of the structure, properties, and function of this material. In addition, as we have pointed out before, cancellous bone may play an important biomechanical role in the etiology of joint degeneration. With these considerations in mind, the architecture of the cancellous bone in the human patella was studied by serial sectioning and microradiography, using an improved technique developed in our laboratory. Volumes of cancellous bone with apparently different functional roles were identified. Stereological techniques were used to quantify the structural characteristics and geometrical relationships throughout the patella. These results led to a structural model for the cancellous bone of the patella, and a comprehensive picture of the internal architecture.The distribution of mechanical compliance and yield stress was also measured, as a function of location and orientation, by a specially constructed micro‐compression testing machine. The measurements reflected the distribution of trabecular architecture, and both the properties and architecture reflected the gross biomechanical function of the patella. Furthermore, a true structure–function relationship was derived. Patellar contact area studies were performed on fresh cadavers and mapped for various angles of flexion. The variation in contact areas and the spatial variations in stiffness are discussed relative to the biomechanics and clinical aspects of the patella.
The fracture mechanics of fatigue crack propagation in compact bone
Authors: Wright T. M. , Hayes W. C. 
Published: December 2004

AbstractThe purpose of this investigation was to apply the techniques of fracture mechanics to a study of fatigue crack propagation in compact bone. Small cracks parallel to the long axis of the bone were initiated in standardized specimens of bovine bone. Crack growth was achieved by cyclically loading these specimens. The rate of crack growth was determined from measurements of crack length versus cycles of loading. The stress intensity factor at the tip of the crack was calculated from knowledge of the applied load, the crack length, and the specimen geometry. A strong correlation was found between the exprimentally determined crack growth rate and the applied stress intensity. The relationship takes the form of a power law similar to that for other materials. Visual observation and scanning electron microscopy revealed that crack propagation occurred by initiation of subcritical cracks ahead of the main crack.
Preparation and characterization of wear debris of orthopedic materials for biocompatibility studies
Authors: Wagner C. N. J. , Shabaik A. H. , Schurman D. J. , Amstutz H. C. 
Published: December 2004

AbstractIn order to test the biocompatibility of wear debris of orthopedic materials, a method has been developed to produce artificial debris of stainless steel, cobalt–chromium alloy, and high‐density polyethylene. In this process, called the accelerated rubbing process, two cylindrical blocks of the same alloy were held under normal pressure in triply distilled water. One block remained stationary while the other rotated at ∼4000 rpm. The water with the metal debris was recirculated between the rubbing surfaces. To prepare debris from polyethylene, a stainless steel block was rubbed over a polyethylene block submersed in liquid nitrogen.The shape of the metal debris was granular, whereas the polyethylene debris had a shted‐like shape. The size distributions were determined from scanning electron micrographs, and it was found that the particles of the metal debris (stainless steel or cobalt–chrome alloy) ranged in sizes from 0.1–10 μ with 75% of all particles <2 μ in diameter. The size of polyethylene debris, expressed as the volume of an ellipsoid, ranged from 10–20,000 μ3 with 45% of all particles in the range of 400–2500 μ3.The x‐ray diffraction pattern revealed that the debris of stainless steel consisted primarily of the face‐centered cubic (fcc) alloy with small amounts of body‐centered cubic (bcc) alloy and Fe3O4, whereas the cobalt–chrome debris consisted of the fcc alloy with a small amount of Cr2O3.The structure of the polyethylene debris was quite similar to that of the solid sample used in its preparation. The percent crystallinity Pc and the size of the crystalline regions D were slightly smaller in the debris than in the solid sample, i.e., Pc = 52 and 55%, D = 90 and 130 Å, in the debris and the solid, respectively.To test the suitability of the artificial debris for biocompatibility studies, stainless steel debris was implanted into knees of adult female New Zealand rabbits. Bacterial challenge studies indicated prolongation, but not increased susceptibility to infection.
Polymer–ceramic composite for tooth‐root implant
Authors: Greenberg A. R. , Kamel Ihab 
Published: December 2004

AbstractA new polymer–ceramic composite suitable for tooth‐root implants has been developed in this study. This material exhibited the desirable combination of good mechanical properties, controlled porosity, and ease of processing. A thermal processing technique was utilized to polymerize acrylic acid (AA) in the presence of either 0.3 or 0.05 μ alumina particles. Porosity and pore size distribution were influenced by the alumina particle size and the processing technique. For a 50 vol % AA solution, the composite had an average compressive strength of 18,000 psi and 38% porosity when 0.3 μ filler particles were used. In comparison, the 0.05 μ alumina‐filled composite had an average compressive strength of 28,000 psi with a 15% porosity.Data on the physical and structural characteristics of the composite are presented in this study. Based on these results, the composite material shows good potential for use in tooth‐root implants as well as other orthopedic implant applications.
In vitro corrosion of dental amalgam phases
Authors: Marek M. , Hochman R. F. , Okabe T. 
Published: December 2004

AbstractThe effects of corrosion on the major phases of dental amalgam microstructure have been studied in vitro on samples prepared by electroplating mercury on Ag3Sn. Tests were made in synthetic saliva, and samples were examined in a scanning electron microscope before and after the exposure.Simple immersion had little effect on the phases. Contact of amalgam with gold increased the probability of deterioration of the γ2 phase. By anodic polarization beyond the breakdown potential, the γ2 phase was selectively dissolved. Under conditions simulating a crevice, the γ2 phase was dissolved and the γ1 phase suffered morphological changes.
In vivo tissue reactivity of radiation‐cured silicone rubber implants
Authors: Gifford George H. , Merrill Edward W. , Morgan Michael S. 
Published: December 2004

AbstractSilicone rubber implants are clinically used in large numbers and elicit a mild tissue reaction. An occasional patient develops an accentuated reaction, an observation which has stimulated clinicians to try to understand this process more fully. The chemistry of medical silicone implants, including quantitative composition, is reviewed. This in vitro laboratory study show less tissue reaction from radiation‐cured pure silicone polymer, as compared with radiation‐cured silicone with SiO2 filler. A proposed system for fabrication and curing of a silicone implant, with the qualities of strength and diminished tissue reactivity, is discussed.
Poly(glycolic acid) sutures in canine vascular anastomoses
Authors: Watts David R. , Carr Stephen H. , Hohf Robert P. 
Published: December 2004

AbstractPoly(glycolic acid) (Dexon; Davis and Geck Company) canine vascular anastomoses between aorta and synthetic grafts and between severed femoral vessels were compared with comparable anastomoses made with Teflon‐coated Dacron (Tevdek; The Deknatel Company) with respect to clinical performance, morphologic characteristics, and tensile strength. While the Dexon anastomoses performed well and were morphologically superior to Tevdek, their tensile strength was significantly lower. Implications of these findings for vascular wound healing are discussed.
Using the shape recovery of nitinol in the Harrington rod treatment of scoliosis
Authors: Schmerling M. A. , Wilkov M. A. , Sanders A. E. , Woosley J. E. 
Published: December 2004

AbstractNitinol, a metal alloy which is able to remember (and return to with slight heating) the shape it had before it was deformed, is demonstrated to be useful in the Harrington rod treatment of scoliosis. A bent nitinol rod can return to its original straight length, applying both axial and lateral forces to the spine during the operation or postoperatively by means of external heating. A research program using simulated spinal forces in a test fixture and implantation in a cadaver was undertaken to show the feasibility of modifying the existing procedure.
An in vitro model for evaluating neural stimulating electrodes
Authors: Johnson P. F. , Hench L. L. 
Published: December 2004

AbstractA model for in vitro evaluation of materials for use as neural stimulation electrodes is developed. Critical areas of concern in developing an in vitro test model discussed include: selection of environment, choice of material, design of stimulating equipment, and analytical procedures used to evaluate materials response. A method of providing quantitative analysis of materials response to stimulation conditions is presented. Evaluation techniques involve the use of scanning electron microscopy, x‐ray spectroscopy, atomic absorption spectrometry, and potentiographic and dielectric analysis of the test electrodes. A diagnostics matrix is presented which assigns a scale factor to quantify the relative corrosion response of the candidate materials. The corrosion response of Pt electrodes is evaluated in terms of scale factors assigned through use of the diagnostics matrix.
Mechanical properties of bone cements containing large doses of antibiotic powders
Authors: Lautenschlager E. P. , Jacobs J. J. , Marshall G. W. , Meyer P. R. 
Published: December 2004

AbstractThe addition of up to 10 g gentamicin sulfate antibiotic powder to 60 g units of Simplex‐P acrylic bone cement caused gradual, proportional decreases in the bulk mechanical properties of compressive and diametral tensile stengths. Water leaching of the antibiotic from the cement did not significantly decrease these strengths.Scanning electron microscopy (SEM) and energy‐dispersive x‐ray spectroscopy (EDS) showed the antibiotic to reside in the acrylic matrix as discrete particles not usually associated with internal porosity. The surface‐sensitive flexural strength of a proprietary bone cement was lowered immediately by small quantities of antibiotic powder, and continued to decrease as doses of up to 10 g/unit were admixed. Water leaching caused channeling as the antibiotic was removed from the surface, but it did not create further changes in flexural strength.
Subcutaneous implants of polypropylene filaments
Authors: Liebert Timothy C. , Chartoff Richard P. , Cosgrove Stanley L. , McCuskey Robert S. 
Published: December 2004

AbstractExturded filaments of unmodified polypropylene (PP) with and without antioxidant were implanted subcutaneously in hamsters in order to determine their rate of degradation. Specimens were removed periodically during a 5 month test period and analyzed by infrared spectroscopy and dynamic mechanical testing. The analyses show that degradation begins to occur after only a few days. Although the reaction sequence is not known, several factors suggest that the in vivo degradation process is similar to autoxidation which occurs in air or oxygen.The infrared data indicate that the hydroxyl content of the implants increases at a rate of 0.061 mg/g polypropylene per day during the initiation phase of the reaction. An induction time of 108 days was established. Carbonyl bonds appear after an implantation time of 50–90 days and increase thereafter. Mechanical tests indicate a decrease in the dynamic loss tangent, tan δ, during the first month of implantation for unmodified polypropylene. No change in the infrared spectra or tan δ was observed, however, for implants containing an antioxidant.Thus, it is apparent that polypropylene filaments implanted subcutaneously in hamsters degrade by an oxidation process which is retarded effectively by using an antioxidant. While the findings reported are specific to subcutaneous polypropylene implants, they suggest that degradation of other systems may involve similar processes. This notion suggests directions for further research on increasing the in vivo stability of synthetic polymers.Long‐term effects of polymer implantation upon tissue were not studied in this work.
Radiotracer techniques for protein adsorption measurements
Authors: Grant Warren H. , Smith Leslie E. , Stromberg Robert R. 
Published: December 2004

AbstractFactors which contribute to measurement errors associated with the use of radiotracers to measure protein adsorption are considered. Techniques for removal of excess adsorbent solution and for estimation of surface area are described. Artifacts induced by the incorporation of a radio‐label both by specific adsorption of the labeling atom and by changes in the protein are discussed.
Surface characteristics of cardiac prostheses in vivo
Authors: Nosé Yukihiko , Kiraly Raymond J. , Picha George 
Published: December 2004

AbstractThe pseudoneointima (PNI) deposited onto a cardiac prosthesis surface reflects many factors of biocompatibility, surface morphology, flow distribution, design, animal's physiological condition, and duration. In the evaluation of any prosthesis, the PNI is one of the prime considerations from both material and functional standpoints.Historically, Dacron fabric has been used as an internal lining for cardiac prostheses. However, we have observed cracks on the Dacron fibers, fiber fracture, fiber protrusion, and poor attachment to the diaphragm, which can cause potentially disastrous complications. In addition, there are basic differences in the PNI formation on aldehyde‐treated pericardium and natural aortic valves as compared to the Dacron fabric.
Minimal degeneration takes place on the chemically treated natural tissue compared with the fabric surface. Intact cells on the tissue suggest a greater compatibility. In later specimens (13 and 24 days), there is active cell infiltration into the pericardium structure with capillary formation.
The deposits on natural tissue are mostly fibrin, with minimum cellular involvement and a trend toward reduction in thickness.
Fibroblast cells are found on the natural tissue as early as 7 days but were not observed on the Dacron fabrics.
Based on these findings, the Dacron fabric‐covered diaphragm studied was not favorable for use in long‐term implantation of cardiac prostheses.
The reactivity of α‐chymotrypsin immobilized on radiation‐grafted hydrogel surfaces
Authors: Venkataraman S. , Horbett Thomas A. , Hoffman Allan S. 
Published: December 2004

AbstractThe enzymatic activity of α‐chymotrypsin (CT), immobilized on hydrogelcoated polymer film supports, has been investigated. The support was prepared by radiation‐graft copolymerization of 2‐hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAAc) on silicone rubber films. The enzyme was covalently coupled to the carboxylic group of MAAc via the N‐hydroxysuccinimide (NHS) ester active intermediate.Increasing MAAc contents of the hydrogel resulted in increased attachment of CT. The integrity of the CT active site after attachment was assessed by an active site titration with diisopropyl fluorophosphate (DFP). As the MAAc content of the hydrogel was increased, an increasing fraction of the attached CT retained its activity to DFP. A greater fraction of CT was active towards DFP when adsorbed than when coupled.The rates of hydrolysis of some synthetic model substrates by the immobilized CT were also measured. The negative charge on the hydrogel had a large effect on the rates of these hydrolyses. The pH optimum for the hydrolysis of N‐acetyl‐L‐tyrosine ethyl ester (ATEE) by immobilized CT was higher than that of free CT. Increasing MAAc content of the hydrogel resulted in larger shifts in the pH optimum. The maximum rates of ATEE hydroylsis per mg CT declined sharply with increasing MAAc content of the hydrogel. This is probably related to the increasing repulsive force between the ATEE (negatively charged above ⋍ pH 9.5) and the hydrogel with increasing MAAc content. The activity of immobilized CT to ATEE is small compared to that of free CT, partly due to this charge effect. Conversely, the rate of hydrolysis of BAEE, a positively charged substrate, by immobilized CT at pH 11, is almost fourfold greater than that by free CT at its pH optimum.
Perfusion trails with a collagen‐immobilized enzyme in an extracorporeal reactor: Activity, stability, and biocompatibility
Authors: Olanoff L. S. , Venkatasubramanian K. , Bernath F. R. , Joyeuse R. 
Published: December 2004

AbstractThis paper is concerned with the evaluation of the in vivo performance characteristics of reconstituted bovine collagen as an insoluble carrier matrix for therapeutic enzymes. The enzyme that was chosen as a model for this evaluation was E. coli L‐asparaginase, which has been widely investigated as a soluble chemotherapeutic agent for the treatment of acute lymphocytic leukemia in humans (Oettgen et al., Cancer Res., 27, 2619, 1967; Beard et al., Brit. Med. J., 1, 191, 1970; Ohnuma et al., Cancer Res., 30, 2297, 1970). The results presented here were obtained from perfusion trials with a collagen–asparaginase reactor incorporated into an extracorporeal circuit attached to the vascular systems of healthy mongrel dogs. A series of 1–2 hr perfusions were conducted with a single collagen‐asparaginase membrane over a period of 4 months. Serum asparagine levels were reduced by more than 98% after 15–30 min perfusion time. Red blood cell (RBC), hemoglobin, hematocrit, and fibrinogen values remained constant during each perfusion. An average decrease of 48% in white blood cell (WBC) and 24% in platelet levels was observed, but these values began to rise slowly even before cessation of the perfusion. No serious toxic or antigenic reactions or mechanical or clotting difficulties were observed. In vitro activity, when assayed between perfusions, remained constant over a period of 4 months of intermittent use and storage. The potential advantages of collagen–enzyme complexes for the administration of therapeutic enzymes is discussed.