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UHMWPE failure in knee joint component
Franta, L. ; Jeníková, Z. ; Pražák, Josef ; Suchánek, J.
A simulation of realistic tribologic conditions in tests “in vitro”contributes significantly to the research in the field of joint replacements. Motion under low relative velocities of friction surfaces of knee joint replacements is studied. The simulator enabled combination of rolling and sliding motion of replacement components. During the experiment, numerous debris of UHMWPE component ares produced and the friction surface is irreversibly changed. Initially, the irregularities of tibial component are smoothed. Consequently, large amount of UHMWPE debris is released. Specimens were loaded for 15.105 cycles with dry or distilled water lubrication. The surface changes of specimens were evaluated.
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Simulace a vyhodnocování otěrových procesů pro UHMPE elementů náhrady kolenního kloubu
Franta, L. ; Jeníková, Z. ; Sieber, D. ; Synková, Hana ; Pražák, Josef ; Suchánek, J.
The demands on artificial knee joint replacement are steadily increasing. Major motivation of this research project, is to increase the lifetime of present prosthesis designs .The main problem of the commonly used UHMWPE / Steel–Implants is the appearance of polyethylene wear which leads to aseptic loosening and therefore to long-term prosthesis failing. In vitro simulations can be an important instrument to predict the wear behavior of new prosthesis designs and materials. ISO 14243 has been developed to obtain comparable results testing on different in vitro simulators. The aim of this study is to verify, how the simplifications made by the in-vitro simulations influence the simulation results and how today’s prosthesis testing can be made more realistic.
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Tribologické metody testování materiálů umělých kloubních náhrad
Pražák, Josef ; Chlup, Hynek ; Franta, L.
In order to achieve a high functional quality of the total artificial joints (TAJ), a special attention must be paid to the selection of suitable materials for the construction (Dumbleton; 1981, O´Kelly; 1979). Nowadays, it seems that the metal parts of the assembly (femoral part for the knee joint) do not pose any problem, but problems of the “soft” parts (tibial part) persist. A careful tribologic testing of considered materials is necessary, consequently. On the other hand, a relevant tribologic testing in a conventional way is extremely time-consuming (a simulation of a 5 km/day for 10 years activity represents a 150 day test approx.). The application of an accelerated testing method is desirable, therefore. Such a method consisting of an application of a special experimental set-up and of an optical evaluation was developed. It was used for a study concerning the lubrication of artificial joints (Pražák; 2000).
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Lubrication of artificial joints -an essentially interdisciplinary problem
Pražák, Josef
The contemporary prevailing practice in the artificial joints application assumes implicitly a sufficient lubrication of the hoint surfaces by the spontaneous effusion fouid of the body liquids. The latter assumption is not apparently universally found and in many cases probably substantially limits the replacement usefulness. One assumes namely that the main cause of the definitive unstable fixation of endoprostheses in the bone structure is caused by the immunobiological reaction of the organism.
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