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VOLUMETRIC WEAR ANALYSIS OF HIP JOINT IMPLANTS BY OPTICAL METHODS
Ranuša, Matúš ; Bryant, Dr Michael (referee) ; Dr Prashant K. Sharma (referee) ; Vrbka, Martin (advisor)
Predložená dizertačná práca sa zaoberá analýzou opotrebenia totálnych bedrových endoprotéz za použitia optických metód. V práci bol predstavený nový prístup hodnotenia objemového úbytku materiálu pomocou 3D optického skeneru. Tento nový prístup je časovo efektívny, poskytuje veľké množstvo snímaných bodov na povrchu implantátu. Množstvo bodov umožňuje presnejšiu rekonštrukciu pôvodnej geometrie a prípadné rekonštrukcie nežiaducich poškodení polyetylénovej vložky pri extrakcii. Predstavené metóda bola validovaná za pomoci štandardizovanej gravimetrickej metódy v súlade s ISO 14242. Následne bol optická skenovacia metóda použitá v troch štúdiách zameraných na analýzu opotrebenia, mechanické zmeny artikulujúceho povrchu a mikroštruktúrne zmeny v dôsledku zlyhania implantátu. Analýza 23 extrahovaných polyetylénových vložiek typ Bicon - plus s rozšíreným použitím v Českej republike poukázala na niektoré problémy spojené so zlyhaním implantátu. Adhezívno - abrazívne opotrebenie bolo identifikované v oblasti penetrácie femurálnej hlavice a následné poškodenia ako delaminácia materiálu , plastické deformácie a pitting boli pozorované v okolí tejto oblasti. Analýza materiálových vlastností poukázala na degradáciu mechanických a chemických vlastností, čo bolo prevažne závislé od rozsahu opotrebenia implantátu. U implantátov boli pozorované výrazné plastické deformácie , nárast oxidačného indexu a nižší pomer tvrdosti voči modulu elasticity, v porovnaní s novými vzorkami. Tečenie materiálu a plastické deformácie, ktoré vykazovali všetky extrahované vzorky boli analyzované v závere predloženej dizertačnej práce, na základe testov na nových implantátoch v zábehovom cykle. Cieľom práce je uviesť nový prístup analýzy opotrebenia polyetylénových vložiek za pomoci optických skenovacích metód a preukázať jeho použiteľnosť na analýze súboru extrahovaných implantátov. Výsledky získané pomocou tejto metódy sa ukázali ako vhodné a môžu viesť k lepšiemu pochopeniu procesov opotrebenia a zlyhávania implantátov.
Effect of synovial fluid composition and surface topography modification on lubrication of joint replacements
Hekrle, Pavel ; Vampola, Tomáš (referee) ; Vrbka, Martin (advisor)
The main objective of this diploma thesis is to determine the influence of synovial fluid compodition and the influence of surface microtextures on lubrication of hip join replacements. For all experiments, hip joint simulator based on the pendulum principle was utilized. Metal heads (CoCrMo) manufactured by B Braun company and and tailor made acetabular cups from optical glass were used as contact couples. Acetabulum dimensions were fabricated according to dimensions of real implants. Experiments with surface microtextures simulated walking cycle for 210 s and development of lubrication film over time was observed.Results have shown that all types of tested structures improved lubrication of contact area, where the best results were obtained for square and triangle shapes respectively. Second set of experiments was based on the fact, that the composition of synovial fluid of healthy people differs from the composition of patients with various stages of osteoarthritis. Therefore, experiments with different model fluids were compared, which in their composition correspond to different groups of patients. For the model fluid that corresponds to the largest number of cases, experiments with individual components and combinations thereof were subsequently performed to provide a more detailed description of how these components affect the film-forming mechanism. The results show, that a change in fluid composition of patients with osteoarthritis can have a major negative effect on fluid formation process within the pair.
Generation of Energy Using Renewable Resources
Vrbka, Martin ; Langerová, Petra (referee) ; Froehling, Kenneth (advisor)
Tato bakálářská práce se zaměřuje na výrobu elektrické energie za pomoci obnovytelných zdrojů. Existuje nespočet faktorů vztahůjících se k obnovitelné energii. Nicméně na tyto aspekty je většinou pohlíženo spíše individuálně, než jako na celek. Tudíž se tato práce pokouší obsáhnout většinu významných aspektů jež jsou spojeny s výrobou energie za pomoci obnovitelných zdrojů a organizuje je v jeden logický celek. To je uskutečněno představením obecného popisu technologie jako takové stejně jako výsledných dopadů použitých systémů.
Educational exercises for finite element method lectures
Sovadina, František ; Vrbka, Martin (referee) ; Nečas, David (advisor)
This work is concerned with mapping of exercises for teaching Finite Element Method (FEM) at Czech as well as foreign universities. The first part reviews exercises on FEM in use at Czech and foreign universities, which might be used for teaching FEM at the Faculty of Mechanical Engineering in Brno in the future. Based on the analyzed material, the aim of the second part of this work was to create a new assignment of an exercise together with its model calculation in ANSYS. The results were then proved through an experiment on a physical model.
Design of parts of tribometer with reciprocating motion
Dražka, Ondřej ; Vrbka, Martin (referee) ; Čípek, Pavel (advisor)
The bachelor thesis deals with design of parts of tribometer with reciprocating motion. Several conceptual solutions are made on base of existing studies from which the best solution for given application is selected. The tribometer will be used for experimental measuring on real cartilage which should lead to better understanding of friction and lubrication processes in synovial joint. The outcome of this thesis are component parts along with the manufacturing drawings.
Design of knee joint simulator
Polnický, Vojtěch ; Čížek, Petr (referee) ; Vrbka, Martin (advisor)
The diploma thesis is focused on the design and realization of an experimental device. The purpose of device is the simulation of dynamic and kinematic conditions of knee replacement during the walking cycle. The simulator will be used to study the formation of the lubricating film in contact of the femoral component and the polyethylene spacer, and to the cyclic wear tests for knee replacements. First part of thesis is focused on the description of working parameters of knee replacements and analysis of knee joint simulators. The description of conceptual design and selection of the final variation follows. The final design allows simulation of dynamic and kinematic conditions of ISO 14 243-3. Creation of lubricating film is analyzed by the non-contact optical fluorescence microscopy method. The work includes complete drawing documentation, wiring diagram, verification of the functionality of the device and detailed operating instructions.
Experimental study of friction in articular cartilage
Praus, Tomáš ; Vrbka, Martin (referee) ; Rebenda, David (advisor)
This thesis deals with the experimental study of friction in articular cartilage. After the introduction to biotribology, there are described a principle of measurment on the Mini-Traction Machine and a brief description of machine itself. After that, there is a propose for a preparation and storage of cartilage samples, construction of the adapter into the MTM and research of the friction coefficient. The results of experimental research showed the negative effect of storing the samples in the refrigerator. On the other hand, the measurement of the friction coefficient of the samples stored in the freezer showed the preservation of the mechanical properties of cartilage. Even load and speed of loading have a big effect on friction. When the speed increases, the coefficient of the friction increases too. There is an extreme increase of the friction at higher speeds. But with increasing load the friction coefficient decreases.
Design of hip joint simulator
Žonda, Peter ; Čížek, Petr (referee) ; Vrbka, Martin (advisor)
The master's thesis is concerned with design and execution of an experimental acetabulofemoral joint simulator. Its primary use is the study of lubrication film thickness in hip implants. The work first describes available hip joint simulators, which simulate particular joint positions. Next, the thesis proposes author’s own designs and solutions. The result is a produced device allowing for dynamic change of load in simulation of hip joint flexion and extension as set by ISO standard. Contact is recorded by an optical apparatus composed of a high-speed camera and a microscope. The work also includes the initial testing experiment and the complete design documentation of the device including electrical wiring diagrams.
Wear analysis of extracted polyethylenes of total hip replacements using optical methods
Přikryl, Adam ; Morovič, Ladislav (referee) ; Vrbka, Martin (advisor)
An experimental methodology for wear assessment of extracted polyethylene hip implants was designed in this diploma thesis. Methodology uses optical 3D scanner and optical profilometer for analysis of wear. Designed methodology for wear analysis was validated by gravimetric method. The results of validation were in good agreement with the increase of wear rate. Validation results show that the methodology is not suited for wear assessment of metal and ceramic implants which have small wear rates. On the other hand the methodology is more than useful for wear assessment of polyethylene implants. Designed methodology for wear assessment was applied on the set of thirteen extracted polyethylene hip implants. Results of the wear analysis were wear volumes and linear wear noted in the wear maps. Roughness of the surface was measured on explanted cups and results were noted in the roughness map. On articulating surface of the cups different areas were observed for measured roughness. Those areas were described as area with machining marks from manufacturing process, polished area from combination of abrasive and adhesive wear, polished area from micro-contact fatigue and area including plastic deformation.
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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2 Vrbka, Marek
1 Vrbka, Michal
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