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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    International Journal of Radiation Applications & Instrumentation. Part C, 39 (1992), S. 495-504 
    ISSN: 1359-0197
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 523 (1988), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 523 (1988), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Interposed fibrous tissue at bone–implant interfaces was quantitatively measured in the presence or absence of polyethylene (PE) or alumina particles. Three different conditions of the interface were designed by implanting a pre-polymerized polymethylmethacrylate (PMMA) plug (plug group), a doughy PMMA (injection group) and a hydroxyapatite (HA) plug (HA group) in the hole drilled at the intercondylar notch of rabbit knees. PE (170±18 μm) or alumina particles (88±26 μm) were repeatedly administered into the knee joints at one month intervals (six times). All animals were sacrificed seven months after the implantation. The bone–implant interface was histomorphometrically examined using undecalcified ground sections. In the plug group, the PE particles significantly increased the extent of the interposed fibrous tissue (p 〈 0.05), while the alumina particles showed no effect. In contrast, both particles showed no significant effects in the injection and the HA groups. These results indicate that both particle characteristics and conditions of the bone–implant interface affected particle-induced fibrous tissue interposition. The loose PMMA plug with PE particles induced the greatest amount of fibrous tissue interposition. ©2000 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: To investigate the biological process of aseptic component loosening caused by polyethylene wear debris, nine rabbits were implanted with acrylic cement into the non-weight-bearing intercondylar notch of distal femur. Six animals were administrated the particles of polyethylene into the knee joint repeatedly for 12 weeks. At the bone-cement interface, thin connective tissue was observed, while bone sometimes existed directly next to the acrylic cement. The percentage of the length of interposed fibrous tissue against the total length of bone-cement interface was measured. The percentage was 15.8±10.3 in the polyethylene-injected group and 8.3±7.7 in the control group (no significance). While not significant, the amount was greater in the polyethylene-injected group. Thus it is proposed that the polyethylene particles played a role in bone resorption and fibrous tissue formation at the bone—cement interface. In some specimens, macrophages and foreign body giant cells that surrounded the particles near the articular surface were seen to cause resorption of bone. It is supposed that this phenomenon is similar to the focal osteolysis that is sometimes observed around a prosthetic component.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 8 (1997), S. 11-18 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Wear volume, surface area and coefficient of friction of UHMWPE cup crosslinked with gamma radiation of 0, 50, 75, 100, 125, 150 and 200 Mrad sliding against an alumina ball were measured using a sphere-on-flat reciprocating type tribology testing machine. The effects of gamma radiation were scarcely observed in coefficient of friction. The coefficient of friction under lubricated (distilled water) and non-lubricated testing conditions was 0.08 to 0.12 and 0.20 to 0.25, respectively. The wear volume of UHMWPE with radiation of 50 Mrad, 75 to 150 Mrad, and 200 Mrad was 70 to 80%, 18 to 25%, and 12 to 15%, respectively, in comparison to non-irradiated specimens. Elongation and tensile strength of UHMWPE with radiation of 100 Mrad decreased to 6%, and 50% of that without radiation, respectively. The hardness increased with increase of the radiation dose. From several kinds of tribological findings, mechanical strength tests, and studies of long-term clinical findings, it is concluded that approximately 200 Mrad is the optimum dose of gamma radiation for clinical use in total hip prostheses.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 9 (1998), S. 575-581 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Polyethylene cups and femoral heads of retrieved total hip prostheses (Charnley 22 mm stainless steel ball, Bioceram 28 mm alumina ball and Muller 32 mm Co–Cr–Mo alloy ball) were observed by the naked-eye and scanning electron microscopy. Cross-linked cups irradiated with gamma radiation in heavy high doses of 100 Mrad were included. On the weight-bearing surface of the cups non-gamma irradiated, carpet-like conspicuous fine fibres, scratches and fine crevices for the 22 mm ball, scale-like with rough and fine crevices for the 28 mm ball, and scale-like structures and many scratches for the 32 mm ball, were observed, mainly. On the whole, the number of crevices for the 32 mm ball was fewer than that for the 22 and 28 mm balls. The weight-bearing areas of the gamma-irradiated cups presented a clearly outlined pattern, irregularly lined with smooth ripples of about 0.1 μm. The scratching, flaking and delamination, characteristic of non-gamma irradiated polyethylene, were not observed at all. These findings indicate that wear is very small for gamma-irradiated polyethylene. For references, the weight-bearing surfaces of retrieved total knee prostheses were compared.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 9 (1998), S. 393-401 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The effects of polyethylene cup thickness, femoral head sizes (22, 28 and 32 mm) and fusion defects on wear were investigated on retrieved total hip prostheses. When the cup thickness was less than 9 mm, the larger the femoral head, the higher the linear wear rate; however, when the cup thickness was more than 9 mm, the larger the femoral head, the linear wear rate was lower. When the cup thickness was less than 11 mm, the volumetric wear rate increased with increasing size of the femoral head, and when it was more than 11 mm, the volumetric wear rate of the three kinds of the prosthetic cups approached the same values. The wear rate of the cross-linked cups irradiated by 100 Mrad were very low, with no correlation to cup thickness. When the cup thickness was less than 9 mm, the volumetric wear rate tended to increase with increasing number of fusion defects. Large diameter fusion defects diminished the tensile strength.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 9 (1998), S. 475-478 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The wear rate of the ultrahigh molecular weight polyethylene cups in combination with a 28 mm alumina femoral head was measured on the radiographs of patients without any complications, and on cups retrieved due to slight loosening of the prosthesis or due to late infection between bone and components. The wear rate on the radiographs did not include the initial wear, but the wear rate on the retrieved cups did include the initial wear. The wear rate on the retrieved cups was higher, by 50%, than that measured on the radiographs. In both cases, the thicker the polyethylene cups, the lower was the wear rate measured. The average wear rate of the 7 and 8 mm thick cups was about twice that of cups 10 and 11 mm thick. From these results, we conclude that polyethylene cups more than 11 mm thick should be used.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1996), S. 753-763 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Wear, frictional torque and creep deformity of UHMWPE sockets crosslinked by gamma radiation of 100, 500 and 1000 Mrad in combination with 28 mm alumina heads, were measured using a hip simulator (under constant load 250 kgf with lubrication of saline solution). Hardness and hydrophilic increased and creep deformity decreased as a result of gamma radiation. The initial wear (decrement of the thickness) of the socket with radiation of 0, 100, 500 and 1000 Mrad was, 150 μm, 100 μm, 70 μm and 50 μm, respectively. The time to steady-state wear at 0, 100, 5000 and 1000 Mrad was about 0.15 million, 0.15 million, 0.1 million, and 0.05 million cycles, respectively. The steady-state wear (decrement of the thickness) of the socket without and with radiation was 200 μm/million cycles and less than 20 μm/million cycles, respectively. Rotational torque was under 0.65 Nm in every case. Swing frictional torque at radiation levels of 0, 100, 500 and 1000 MRad were 1.60–2.84 Nm, 3.24–9.02 Nm, 5.23–8.78 Nm, and 2.51–6.79 Nm, respectively.
    Type of Medium: Electronic Resource
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