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Analysis of friction of hip joint replacements with modification of surface topography
Němeček, Daniel ; Quinn, Cheney (referee) ; Nečas, David (advisor)
Hip endoprosthesis introduces an effective treatment for patients suffering from advanced stages of hip degeneration. Despite the advancements made in recent years, limited longevity negatively affects the application of this technology in young patients. The main mechanism which causes limited longevity is wear, which depends on the friction and lubrication of the joint. This thesis aims to observe the effect of a textured surface on a UHMWPE polyethylene cup combined with a smooth femoral head as a solution, which may reduce the friction and wear of the contact surfaces. Two textured cups and three smooth femoral heads were used in the experiment (ceramic, metal, oxinium). The results showed that the textured surface has a positive effect on both reducing friction and providing more stability with the use of synovial fluid. A significant reduction in friction is observed for the surface with smaller dimples rather than for the surface with larger ones. Specifically, the combination of a ceramic femoral head and a finely dimpled surface resulted in the reduction of friction by 66 %. Attention was also paid to the effect of the load on the hip. In most cases, the load did not significantly impact the results. It can be assumed that reducing the friction at the joint leads to the reduction of the rate of wear, thus increasing the implant longevity.
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An investigation of lubrication of knee joint replacement
Sýkora, Tomáš ; Horák, Zdeněk (referee) ; Nečas, David (advisor)
This diploma thesis deals with an experimental analysis of knee joint replacement lubrication. The experiments were realized at a knee joint simulator which can apply conditions according to certain standard and survey the phenomena by using fluorescence microscopy. The aim of thesis is to clarify the influence of particular components of synovial fluid on the lubrication process. The intensity of fluorescence expresses dimensionless parameter of a lubrication film thickness. There was a fundamental study with mineral oils before the experiments with the synovial fluid. The study allows to have a look at contact transformation during walk. Results are shown in graphs as dependency of intensity on time, including pictures showing phenomena in the contact zone. Experiment results show that protein -globulin creates a layer on the surface. There is albumin on the layer and it makes the lubricating film thicker. The protein interaction is supported by hyaluronic acid and fosfolipids which stabilizes the created structure. According to lubrication is behaviour of film related to a complex structure of synovial fluid. Thesis gives more information about behaviour of synovial fluid and can be used for future development of knee replacements.
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Friction and lubrication of articular cartilage
Hilšer, Pavel ; Daniel, Matej (referee) ; Vrbka, Martin (advisor)
The main goal of this diploma thesis is to determine the role of hyaluron acid and phospholipids on friction and lubrication of articular cartilage in regard to optimization of viscosupplements. This is carried out by measuring the coefficient of friction of the articular cartilage with several lubricants. Cartilage is lubricated particularly by a conventional viscosuplement, optimized viscosuplementation with phospholipids and model synovial fluid. In order to observe the function of those viscosuplements in the human body, both are mixed with the model synovial fluid, ubiquitous in human joints, in given ratio. Experiments revealed high friction when it comes to convectional viscosupplementation as opposed to low friction of the optimized viscosuplement with phospholipids. The same situation occurs when cartilage is lubricated with those viscosuplements mixed with model synovial fluid which might lead to development of a new, better, viscosupplementation based on hyaluron acid and phospholipids.
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Lubrication of hip joint replacements
Rebenda, David ; Hartl, Martin (referee) ; Vrbka, Martin (advisor)
This thesis deals with the experimental study of lubrication of hip joint replacements. The influence of the synovial fluid composition and the head material to the lubricating film thickness were asssesed by using a pendulum hip joint simulator. Both of these effects were assesed under static and dynamic loading conditions. The experimental results showed that the movement of the head against the cup is unnecessary for the separation of the rubbing surfaces by a layer of adsorbed proteins. Composition of the synovial fluid then significantly influences the thickness of the lubricating film. Two opposite extremes have been observed during tests with two model synovial fluids. The first fluid formed a very strong lubricating film. The second sample almost prevent adsorption of proteins and consequently formed only very thin lubricating film. The influence of the material is noticeable when comparing the results obtained with a metal head and ceramic heads. Metal head formes under the same conditions thicker lubricating film. This evidence may be partly influenced by different diametrical clearances, which were in the case of ceramic heads higher.
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Lubrication of knee joint replacement
Sadecká, Kateřina ; Horák, Zdeněk (referee) ; Vrbka, Martin (advisor)
The work deals with the lubrication of total knee replacement using fluorescence microscopy method, which allows unique insight into the contact between femoral and tibial component. The aim was to determine the effect of composition of synovial fluid (i.e. albumin, -globulin, hyaluronic acid and phospholipids) on film thickness and protein behaviour in contact, and also to determine changes of contact area during rotation. Since this is the first experimental work dealing with a knee replacement lubrication primarily, only simple rotation and load cycles were applied by the knee simulator. The output of the experiments was fluorescence intensity, which corresponds to dimensionless film thickness, over time. Another important output are the images directly showing the fluorescently labelled proteins in the contact area. The results show, there are fundamental differences in lubrication in different positions of rotation, due to changes of position, shape and behaviour of the contact area. The composition of the lubricant is also essential, since the proteins themselves form a relatively strong lubricating film and their mixture leads to a substantial reduction of film thickness, due to significant formation of clusters. Complex fluid, although it does not form the strongest layer, is able to create a quite continuous film.
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The Effect of Synovial Fluid Constituents on Lubrication of Hip Joint Replacements
Nečas, David ; Daniel,, Matej (referee) ; Sawae, Yoshinori (referee) ; Hartl, Martin (advisor)
Dizertační práce se zabývá mechanismy mazání v náhradách kyčelního kloubu. Byla provedena systematická studie formování proteinového filmu při zahrnutí různých materiálů a provozních podmínek. Hlavní pozornost je přitom věnována roli jednotlivých proteinů obsažených v synoviální kapalině při současné přítomnosti dalších proteinů. Jelikož metody aplikované v předchozích studiích neumožňovaly separovat jednotlivé složky maziva, byla vyvinuta optická měřící metoda na principu fluorescenční mikroskopie. Z důvodu verifikace metody byly provedeny dvě nezávislé studie zaměřené na měření tloušťky mazacího filmu a dělení maziva na výstupu mazaného kontaktu. Z důvodu určitých limitací fluorescenční mikroskopie byla dále využita i metoda optické interferometrie, jejíž využití je ilustrováno ve studii zabývající se formováním mazacího filmu v náhradách kyčelního klubu při uvažování reálné konformity třecích povrchů. Závěrečná část práce představuje nový metodologický přístup založený na in situ pozorování kontaktní oblasti umožňující popsat roli jednotlivých proteinů ve vztahu k vývoji tloušťky mazacího filmu. Práce obsahuje originální výsledky, které přináší nové poznání v oblasti biotribologie náhrad kyčelního kloubu vedoucí k dalšímu vývoji implantátů při snaze zabránit jejich selhání v důsledku omezené životnosti.
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Study on flow and viscoelastic properties of laboratory prepared synovial fluids by macrorheological techniques
Veldamonová, Aneta ; Heger, Richard (referee) ; Smilek, Jiří (advisor)
This bachelor thesis deals with preparation and characterization of synthetic synovial fluid. Preparation was focused mostly on finding proper ratios of substances existing in real synovial fluid which have influence on viscoelastic properties. Based on study of literature, these substances are hyaluronic acid, lubricin, phospholipids and proteins. Samples of real synovial fluid from horse hock acquired from University of veterinary and pharmaceutical sciences Brno were tested for comparation with synthetically prepared synovial fluid. Both synthetic and real synovial fluid were characterized by macrorheological techniques. The experimentally obtained data were then compared with data from the patent on which the preparation of synthetic synovial fluid was based on. Thermogravimetry and isothermal thermogravimetry were used as additional method for the study of moisture and water binding of synovial fluids.
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Analysis of THR lubrication with the use of fluorescent microscopy
Tkadlec, Tadeáš ; Daniel, Matej (referee) ; Nečas, David (advisor)
This diploma thesis deals with an experimental analysis of lubrication of total hip joint replacement using fluorescence microscopy, focusing on so-called soft bearing pairs. Experiments were realized using a hip joint simulator, which was modified and refined for fluorescence microscopy. The aim of this diploma thesis was to determine the effect of the individual components of the synovial fluid on the lubrication mechanisms. For this purpose, different model fluids were designed to represent the composition of proteins and other synovial fluid constituents to elucidate the effect of albumin, -globulin and hyaluronic acid on the resulting lubrication performance. The experiments were separate into two categories different in type of load, dynamic (representative walking) and combined (representing standing with short walk). The experimental results were time-dependent fluorescence intensity values, representing dimensionless film thickness parameters. The values were recorded on the graphs and supplemented with fluorescence images taken during the characteristic sections of the measurements. The measured data was subsequently confronted with previously published articles. It was found that the dominant constituent responsible form film thickness is albumin, while -globulin and hyaluronic acid forms thin stable layer enhancing adsorption ability of albumin which contributes to increase of film thickness eventually.
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An investigation of friction and lubrication of coated hip joint replacement
Balcárek, Ondřej ; Horák, Zdeněk (referee) ; Nečas, David (advisor)
The thesis focused on studying the effects of a new hydrogel coating and material combinations on the coefficient of friction and formation of lubricating film in the conformal contact of hip joint replacement. Experiments were conducted using a ball-on-cup configuration with a hip pendulum simulator. The formation of the lubricating film was observed using fluorescence microscopy. The results showed that the application of the coating did not have a clear impact on the coefficient of friction. However, for pairs with a coated cup, there was a reduction in CoF by approximately 20%. Generally, lower friction was observed when using a ceramic joint head. Surprisingly, even more interesting results were obtained in the lubrication analysis, where the use of metal heads led to a reduction in the thickness of the lubricating layer. Ceramic pairs exhibited very stable behavior. In addition to friction and lubrication, the topography of the implants was further evaluated, and their wettability was analysed. Although the polymer coating was expected to be highly hydrophilic, the surface properties were only slightly influenced, which partly explains why there was no significant improvement in the tribological behavior of the replacement. As the coating applied is already patented and its effectiveness in reducing wear has been clearly demonstrated, it is appropriate to investigate this issue further, with more attention being paid to long-term experiments. Based on the obtained data, it appears that the short-term benefits of the coating are practically negligible. However, it is important to highlight that, except for minor exceptions, the application of the coating did not lead to a deterioration of properties, which is a significant outcome of this work.
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Analysis of friction of hip joint replacements with modification of surface topography
Němeček, Daniel ; Quinn, Cheney (referee) ; Nečas, David (advisor)
Hip endoprosthesis introduces an effective treatment for patients suffering from advanced stages of hip degeneration. Despite the advancements made in recent years, limited longevity negatively affects the application of this technology in young patients. The main mechanism which causes limited longevity is wear, which depends on the friction and lubrication of the joint. This thesis aims to observe the effect of a textured surface on a UHMWPE polyethylene cup combined with a smooth femoral head as a solution, which may reduce the friction and wear of the contact surfaces. Two textured cups and three smooth femoral heads were used in the experiment (ceramic, metal, oxinium). The results showed that the textured surface has a positive effect on both reducing friction and providing more stability with the use of synovial fluid. A significant reduction in friction is observed for the surface with smaller dimples rather than for the surface with larger ones. Specifically, the combination of a ceramic femoral head and a finely dimpled surface resulted in the reduction of friction by 66 %. Attention was also paid to the effect of the load on the hip. In most cases, the load did not significantly impact the results. It can be assumed that reducing the friction at the joint leads to the reduction of the rate of wear, thus increasing the implant longevity.
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