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Simulation and Evaluation of the UHMWPE Surface Wear
Franta, L. ; Jeníková, Z. ; Sieber, D. ; Synková, Hana ; Pražák, Josef ; Suchánek, J.
The goal of this research project is to increase the lifetime of total knee joint replacement. Therefore the “In vitro“ simulation of realistic physiological conditions is important. For the knee joint replacement experiments, a KKK ELO 98001 simulator is used. The simulator enables the combination of rolling and sliding motion of replacement components with sinusoidal loading. During the experiment, a considerable amount of wear particles of the UHMWPE component is produced and the friction surfaces are irreversibly changed. Initially, the irregularities of tibia component are smoothed. Consequently, large amounts of UHMWPE wear are released. The surface changes of specimens were evaluated.
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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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Zbytková deformace v bifurkaci lidské aorty
Adámek, T. ; Horný, L. ; Chlup, Hynek ; Franta, L.
At the present paper we report values of opening angles in human aortic bifurcations. A standard method of opening angle measurement was used. Three aortas were measured. Ten samples were excised from each aorta. Three rings were obtained from abdominal aorta close to the bifurcation, arteria iliaca communis dextra and sinistra and one form the bifurcation. The last one was composed of two rings, left and rignt, which were measured together. The residual strains were occurred in human aortic bifurcations and had different values in the left and the right branch of the bifurcated artery. The results of at the bifurcation can be influenced by fact that the branches of iliac arteries are still intergrown here. Two kinds of the opening angle investigation at the bifurcation were tested, a bifurcation septum fixed method and a circular sector fixed method. But both revealed differences in the opening angle values at the bifurcation.
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Realistic simulations joint replacement human joint
Franta, L. ; Pražák, Josef
Any artificial testing of joint replacement is considered as contribution significant to research in the field of joint replacements. The fundamental parameter, which influeces a length of survival, is an effective coefficient of friction, especially in low mutual speed of friction surfaces of joint replacements.
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