Dissertations / Theses on the topic 'Orthopedic implants – Materials'

Thesis (M.S.)--University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 30, 1981) Includes bibliographical references.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 128-138). Also available in electronic version. Access restricted to campus users.

Orientador: William Dias Belangero
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas
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Resumo: Este estudo teve como objetivo avaliar o desempenho in vivo, de implantes cilíndricos com altura e diâmetro de 5mm formados por cerâmica ß-tricálcio fosfato (ß-TCP) ou polietileno de ultra-alto peso molecular (PEUAPM) todos recobertos com hidrogel de poli (2-hidroxi etil metacrilato) - poli(metacrilato de metila-co-ácido acrílico) (75:25) (pHEMA/poli (MMA-co-AA)) para preencher defeitos osteocondrais nos joelhos direito e esquerdo de cães. Foram operados treze cães machos com peso entre 15 e 25 kg fornecidos pelo Canil do Centro Multi Institucional de Bioterismo da Unicamp, sem raça definida, em bom estado de nutrição, vacinados após período prévio de quarentena. Cinco cães foram utilizados como controle e oito foram seguidos por nove meses após a colocação dos implantes. Os implantes de cerâmica foram colocados no sulco troclear do joelho direito e os de polietileno no joelho esquerdo. Foram realizadas análises da superfície do implante macroscópica (in vivo e in vitro), mecânica e microscópica, com a finalidade de avaliar a formação de tecido sobre o implante, o seu desgaste, o se desempenho viscoelástico e a interface formada entre o implante e o tecido ósseo. Os implantes de cerâmica apresentaram desempenho inferior ao polimérico, em todos os critérios avaliados. Embora não tenha havido desgaste significativo na superfície do hidrogel os dois implantes estudados produziram abrasão na superfície da patela
Abstract: This study had the purpose of evaluating ¿in vivo¿ the performance of ß-TCP ceramic or extreme high molecular weight polyethylene cylindrical implants, with height and diameter of 5mm, all covered with poly(2-HEMA) ¿ poly(methyl methacrilate-co-acrilic acid) hydro gel (polyHEMA/poly(MMA-co-AA) (75:25) in order to fill in bone defects in both the right and left knees of dogs. Thirteen male dogs weighting between 15 and 25kg, supplied by UNICAMP¿s Centro Multi Institucional de Bioterismo, were operated. All the dogs were well nourished, vaccinated and the operation took place after a previous quarantine period. Five dogs were used as control and eight were followed for nine months after putting the implants. The ceramic implants were placed in the right knees and the polyethylene ones in the left knees. Macroscopic, mechanic and microscopic analyses of the implant surface, (both in vivo and in vitro) were performed, in order to evaluate the tissue formation on the implant, the wearing off of the implant, the viscoelastic performance and the interface between the implant and the bone tissue. The ceramic implants presented an inferior performance when compared to the polymeric ones, in all of the evaluated aspects. Although there was no significant degradation on the hydro gel surface, both studied implants produced erosion on the kneecap surface
Mestrado
Cirurgia
Mestre em Cirurgia

The currently used biomaterials for surgical implantation include stainless steel, titanium and its alloys. However, due to the non-degradability and the mismatch of the mechanical properties between these metallic implants and human bone, there maybe a long-term adverse effect of inflammation or stress shielding effect. This may lead to bone loss which brings with a higher risk of implant failure. To avoid this problem, implants made of biodegradable materials are the alternatives. Due to the poor mechanical properties of biodegradable polymer especially for load-bearing area, biodegradable metal is used instead. Magnesium is the potential candidate since it is degradable with mechanical properties similar to human bone whilst magnesium ion is an essential element to human bodies. With the advantages of using magnesium for implantations, it can be potentially used for fracture fixation implant and bone substitutes. However, its rapid degradation and release of hydrogen gas may inhibit its use. Hence, modification is required. In this project, plasma immersion ion implantation and deposition (PIII&D) using aluminium oxide as the plasma source was conducted on the magnesium alloys. The corrosion resistance properties of the plasma-treated magnesium alloy were found to display significant improvement in immersion test especially at early time points. The plasma-treated sample was compatible with osteoblasts. Cells attached and grew on the treated sample but not the untreated sample. The animal study showed consistent results with the cell study, and there was a significant increase in bone formation around the treated sample when compared to the untreated sample. The other potential application of magnesium is its usage as a bone substitute. Due to the limitations of autografts and allografts, synthetic bone substitutes are developed. The ideal bone substitutes should have similar properties to those found with autografts. However, no such bone substitutes presently exist; hence, a novel hybrid material is fabricated in this project through the addition of magnesium granules into a biodegradable polymer polycaprolactone (PCL). The immersion test showed that an apatite layer composed of magnesium, calcium, phosphate and hydroxide was formed on the hybrids but not on pure PCL, which suggested that the hybrids were osteoinductive and osteoconductive. The compression test showed that the mechanical properties were enhanced with the incorporation of magnesium granules into pure PCL and were still maintained after 2 months of immersion. Osteoblasts grew well on the PCL-Mg hybrids. The addition of smaller amounts of magnesium granules (0.1g PCL-Mg) resulted in higher ALP activity and up-regulation of different bone markers when compared to the pure PCL. Finally, the animal studies showed that more new bone formation was found around the 0.1g PCL-Mg hybrids especially at early time points, which suggested that the healing time could be shortened. In conclusion, fracture fixation implants and novel bone substitutes based on magnesium were developed in this project. The aluminium oxide coating was able to improve the corrosion resistance properties of magnesium alloy by suppressing the release of magnesium ions. The PCL-Mg hybrids were found to be biodegradable, biocompatible, osteoconductive, osteoinductive and mechanically matched to human bone properties.
published_or_final_version
Orthopaedics and Traumatology
Doctoral
Doctor of Philosophy

Polyetheretherketone (PEEK), a polymer with mechanical strength comparable to human bone, is gaining popularity in the orthopedic field because it can potentially relieve the clinical complications, such as stress shielding effect and inevitable implantation failure, which are caused by the mismatch of the mechanical strength between the current metallic implants and the implantation sites. However, it is bio-inert and requires supplementary modification. Plasma immersion ion implantation (PIII) has been well documented that it is a good way to improve the bioactivity of a biomaterial. It is a method that introduces new elements to the biomaterial, generating bio-functional groups on the material surface without altering its mechanical properties. Hence, the aim of this study is to improve the bioactivity of PEEK by modifying its surface chemistry with the use of water (H2O) and ammonia (NH3) plasma immersion ion implantation (PIII) without altering its mechanical properties. After PIII treatment, a series of surface characterization tests that provide information about the surface properties, such as surface energy, roughness, surface chemical composition and crystallinity of PIII-treated PEEK were carried out. Results show that both H2O PIII and NH3 PIII-treated PEEK had significantly higher surface energy and roughness than untreated PEEK. There was also no significant change in the crystallinity of the PIII-treated PEEK, indicating that PIII treatment will not alter the mechanical properties of PEEK. Improvement in wetting properties of PEEK samples suggest the formation of polar functional groups on the PIII-treated PEEK materials, while the increased in surface roughness may be due to the energetic bombardments of plasma ions on the material surface. The in vitro bioactivity of plasma-treated PEEK was investigated and confirmed with hMSC-TERT. Initial cell attachment, cell spreading area, cell proliferation and differentiation were studied. Cell adhesion and cell spreading were enhanced on PIII-treated PEEK, and higher cell viability was observed on PIII-treated PEEK. Moreover, cell proliferation was promoted on early time point and cell differentiation was also enhanced particularly on day 7 by measuring the alkaline phosphatase activity. Therefore, H2O-PIII and NH3-PIII treatments were able to promote the bioactivity of PEEK samples.
published_or_final_version
Orthopaedics and Traumatology
Master
Master of Philosophy

Cell adhesion to the extracellular matrix through cell-surface integrin receptors is essential to development, wound healing, and tissue remodeling and therefore represents a central theme in the design of bioactive surfaces that successfully interface with the body. This is especially significant in the areas of integrative implant coatings since adhesion triggers signals that regulate cell cycle progression and differentiation in multiple cellular systems. The interactions of osteoblasts with their surrounding extracellular matrix are essential for skeletal development and homeostasis and the maintenance of the mature osteoblastic phenotype. Our objective was to engineer integrin-specific bioactive surfaces that support osteoblastic differentiation and promote osseointegration by mimicking these interactions. We target two specific integrins essential to osteoblast differentiation the type I collagen receptor alpha2beta1 and the fibronectin receptor alpha5beta1. The central hypothesis of this project was that the controlled presentation of type I collagen and fibronectin binding domains onto well-defined substrates would result in integrin-specific bioadhesive surfaces that support osteoblastic differentiation, matrix mineralization, and osseointegration. We have demonstrated that these biomimetic peptides enhance bone formation and mechanical osseointegration on titanium implants in a rat tibia cortical bone model. We have also shown that the presentation of multiple integrin-binding ligands synergize to enhance intracellular signaling and proliferation. Finally, we demonstrate the advantage of the short biomimetic peptides over the native ECM proteins. This research is significant because it addresses current orthopaedic implant limitations by specifically targeting cellular responses that are critical to osteoblastic differentiation and bone formation. This biomolecular approach provides a versatile and robust strategy for developing bioactive surfaces that enhance bone repair and osseointegration of orthopaedic implants.

Nacre from mollusc shells has a complex hierarchical structure composed of an organic-inorganic composite, and exhibits remarkable mechanical properties. In addition, nacre is biocompatible and bioactive making it an excellent candidate for biological coatings for orthopaedic applications. The bioprocessing of nacreous coatings on conventional orthopedic materials via biomineralization of abalone shells was examined in this thesis. The animal reaction to the materials was evaluated by the coating surface morphology, thickness and coating-implant interface, which were characterized using SEM, EDS, XRD and Raman spectroscopy. In the first test, poly(methyl methacrylate) (PMMA), high density polyethylene (HDPE), and titanium (Ti) substrates were implanted separately on the growth surface of abalone shells to examine the effect of different materials on mineral growth. The abalones were under restricted diet. PMMA and HDPE implants resulted in thicker coatings and were able to achieve the desired nacre structure (thickness of 38.1 ± 28.8 μm and 38.7 ± 22.2 μm, respectively). The titanium implants showed thin and sparse coating and were not able to achieve nacre (thickness of 5.3 ± 3.4μm). In the second test, the effect of Ti surface modification (micro-porous, nano-porous and smooth surface) was examined. The substrates were implant together on one location of the shell and were under normal feeding conditions. Thick nacreous coatings, 50 to 280 µm, were formed on the Ti surfaces. There was no apparent trend between the type of Ti surface and the coating formed; however, it appeared that coatings on the implants were similar within the same animal. Thus, this indicates that feeding conditions and location of implantation may play a role in coating mineralization. In addition, two new unique features were found in the implants that have not been reported in literature before: vaterite and alternating bands of nacre towers and aragonite grains across the coating surface. The findings in this thesis therefore suggest that nacreous coatings can be processed on both polymeric and metallic implant materials as long as proper abalone culturing conditions are maintained. The biofabrication techniques developed in this project can be applied to the development of new classes of surface coatings for biomedical implants.

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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

This thesis refers to Fe-based biodegradable materials and their potencial aplications in medicine, especially as temporary bone implants. This work generaly summaries aplications of biomaterial in medicine with more interest kept on biodegradable materials and their in-vivo corrosion. The experimental part refers to conduction of porous Fe-based materials with silica addition. The structure of prepared specimens is identified by EDX and XRD analysis. The imersion test and electrochemical studies were conducted to observe corrosion behaviour with respect to different concentration of silica. Potenciodynamic curves were obtained to determine corrosion potencial and corrosion current density of prepared samples.

Mestrado em Materiais e Dispositivos Biomédicos
Zircónia e alumina são biocerâmicos bastante conhecidos, e são usados principalmente em aplicações ortopédicas. Estes materiais têm sido aplicados em implantes de anca e joelho graças à reduzida taxa de desgaste e à excelente biocompatibilidade que apresentam. No entanto, estes cerâmicos apresentam também algumas limitações: a fragilidade da alumina ao impacto e a sensibilidade da zircónia ao envelhecimento. Devido a estas limitações, o objectivo passou por desenvolver implantes mais resistentes e com uma resposta inflamatória menos intensa. Surgiram, então, estudos de compósitos de zircónia e alumina. Neste estudo, foram desenvolvidas três diferentes composições de Alumina reforçada com Zircónia (ZTA) com 80 wt% a 90 wt% de alumina, e três composições de Zircónia reforçada com Alumina (ATZ) com 80 wt% a 90 wt% de zircónia. Foram usados dois tipos diferentes de zircónia estabilizada: zircónia estabilizada com 3 mol% de yttria (3YSZ) que foi usada nos compósitos ATZ, e zircónia estabilizada com 2 mol% de yttria (2YSZ) aplicada nos compósitos ZTA. A composição ATZ com o melhor conjunto de propriedades foi também testada com a zircónia 2YSZ, de forma a produzir um compósito com melhores propriedades mecânicas e uma resistência à degradação semelhante à apresentada pelo compósito ATZ, com a zircónia 3YSZ. Foram seleccionados dois aditivos, óxido de lântanio e pentóxido de tântalo, que foram depois adicionados aos compósitos ATZ e ZTA com o melhor conjunto de propriedades (composição 80:20), com o objectivo de melhorar a resistência ao envelhecimento e as propriedades mecânicas dos materiais produzidos. Após uma etapa de moagem, os pós compósitos foram obtidos por atomização, a partir de suspensões estabilizadas, com uma distribuição de tamanho de partícula nanométrica controlada. Estes pós foram caracterizados através de várias técnicas tais como microscopia electrónica de varrimento, difracção de raios-X, fluorescência de raios-X, densidade real, e área superficial específica. De forma a aumentar a densidade dos corpos em verde, foram efectuadas duas diferentes prensagens, prensagem uniaxial e prensagem isostática a frio (CIP). Foram obtidos cerâmicos com uma elevada densidade (com densidade relativa entre 97% e 99%) a uma baixa temperatura de sinterização (1400ºC). O tamanho de grão das amostras sinterizadas foi observado por SEM e, de forma a verificar as fases cristalográficas presentes, foi realizada difracção de raios-X. Em todos os compósitos foi obtida uma microestrutura dispersa, com um tamanho de grão nanométrico (abaixo dos 500 nm). Este conjunto de etapas de produção aplicado levou à obtenção de compósitos com propriedades mecânicas melhoradas. Foram estudadas a dureza de Vickers, a tenacidade à fratura e resistência à flexão das amostras sinterizadas. Os compósitos ATZ atingiram os melhores valores de tenacidade à fractura e resistência à flexão (acima de 5 MPa.m1/2 e 1394 MPa respetivamente), enquanto os compósitos ZTA apresentaram os melhores valores de dureza (acima de 1846 HV). Como era esperado, o compósito ATZ com zircónia 2YSZ apresentou melhores propriedades mecânicas, tendo sido obtidos 7.94 MPa.m1/2 de tenacidade à fratura e 1498 MPa para a resistência à flexão. A aplicação dos dopantes nos compósitos ZTA e ATZ induziram alterações nas suas propriedades. A adição de Ta2O5 melhorou, com sucesso, as propriedades mecânicas dos dois tipos de compósitos. Foi verificado um aumento dos valores de dureza, tenacidade à fratura e resistência à flexão em relação às amostras sem dopantes. A adição de La2O3 não levou a melhorias nas propriedades mecânicas mas, no entanto, também não teve um efeito prejudicial, o que levou à sua preservação. Foram realizados testes de envelhecimento de acordo com a norma ISO13356 (2008) em todos os compósitos produzidos. A quantidade de zircónia monoclínica, indicador de degradação, foi determinada por difracção de raios-X após 5,12,24,48 e 96 horas de testes de envelhecimento. Foi determinado que os compósitos ZTA não dopados, não apresentaram zircónia monoclínica após 96 horas em ambiente agressivo. Para os compósitos ATZ, apesar de a quantidade de zircónia monoclínica aumentar proporcionalmente ao conteúdo de zircónia presente no compósito, foi verificado que a extensão da degradação foi mínima, e relegada apenas para a superfície do material. Esta evidência permitiu que as propriedades mecânicas se mantivessem durante todo o período dos testes de degradação. Como era esperado, o compósito com a zircónia menos estável, o ATZ com a zircónia 2YSZ, apresentou o conteúdo mais elevado de zircónia monoclínica. No entanto, o facto de as propriedades mecânicas se manterem ao longo dos testes de degradação, confirmou que a degradação, mais uma vez, não se expandiu para o interior do material. A adição dos dois dopantes levou a melhorias na resistência à degradação dos compósitos ATZ, que apresentaram um conteúdo de zircónica monoclínica menor em comparação com as amostras não dopadas, após 96 horas de testes de degradação. No entanto, a adição de Ta2O5 teve um efeito desestabilizador na zircónia 2YSZ presente no compósito ZTA, sendo que foi detectada 10% de zircónia monoclínica após as 96 horas de testes de degradação. De novo, foi confirmado que esta degradação esteve presente apenas à superfície do material, visto que as propriedades mecânicas se mantiveram após estes testes. Foi também testada a biocompatibilidade destes compósitos. Células MG63 foram cultivadas nas amostras sinterizadas e foram realizados ensaios MTT e ensaios de atividade da fosfatase alcalina. Para todos os compósitos produzidos foi verificado que a viabilidade/proliferação celular aumentou significativamente desde o dia 1 para o dia 4. Os compósitos ZTA, que possuíam um maior número de locais de adesão, apresentaram uma maior adesão e proliferação celular, em comparação com os compósitos ATZ. A adição de La2O3 e Ta2O5 não induziu diferenças significativas na viabilidade celular dos compósitos ATZ. No entanto, no compósito ZTA, a adição de Ta2O5 levou a um pior desempenho devido à sua verificada hidrofobicidade. O presente estudo mostra que podem ser obtidas composições óptimas destes compósitos, com excelentes propriedades mecânicas, resistência à degradação e biocompatibilidade satisfatória.
Zirconia and alumina are well known bioceramics, used in the field of orthopedics. These materials have been used as hip and knee bearings thanks to their reduced wear rate and excellent biocompatibility. However, these ceramics presented some limitations: the brittleness of alumina and the aging sensitivity of zirconia. The aim became to develop long-lasting hip implants, with less inflammatory response and better designs. Zirconia alumina composites were then studied. In this study, three different grades of alumina toughened zirconia composites (ATZ) from 80 wt% to 90 wt% of zirconia, and three grades of zirconia toughened alumina (ZTA) from 80 wt% to 90 wt% of alumina were developed. Two different types of stabilized zirconia were used: 3 mol% yttria stabilized zirconia (3YSZ) was applied on the ATZ samples, and a 2 mol% yttria stabilized zirconia (2YSZ) on the ZTA samples. The ATZ with the best set of properties (80Z20A) was also tested with the 2YSZ, in order to produce a composite with improved mechanical properties and similar aging resistance to the ATZ with 3YSZ. Two selected additives, lanthanum oxide and tantalum pentoxide were added to the best ATZ and ZTA composite (80:20 composition) with the aim of enhance the aging resistance and mechanical properties of the produced materials. After a wet milling stage, the composite powders were achieved by spray-drying, from stabilized suspensions with a controlled nanometric particle distribution. The obtained composite powders were characterized through several techniques, such as scanning electron microscopy, X-ray diffraction, X-ray fluorescence, true density and specific surface area. Two stages of pressing, uniaxial pressing and cold isostatic pressing, were performed in order to improve the density of the green pieces. High density ceramics (with a relative density between 97% and 99%) were achieved with a low sintering temperature (1400ºC). The grain size of the sintered pieces was determined by SEM, and X-ray diffraction was performed in order to verify the present crystallographic phases. A disperse microstructure was obtained for all composites, with a nanometric grain size (under 500 nm). This set of producing stages, lead to the obtention of composites with enhanced mechanical properties. The Vickers Hardness, fracture toughness and flexural strength of the sintered samples were evaluated. Higher values of fracture toughness and flexural strength were achieved for the ATZ samples (up to 5 MPa.m1/2 and 1394 MPa respectively), while ZTA samples presented higher values of hardness (up to 1846 HV). As expected, the ATZ with 2YSZ presented enhanced mechanical properties, with an outstanding fracture toughness of 7.94 MPa.m1/2, and 1498 MPa of flexural strength. The addition of the two dopants to both ZTA and ATZ composites induced changes in their properties. The addition of Ta2O5 successfully improved the mechanical properties of both composites. In comparison with the undoped ATZ and ZTA composites, improvements of the hardness, fracture toughness and flexural strength were verified. The addition of La2O3 did not lead to an enhancement of the mechanical properties; however, it did not led to a deleterious effect either, and these properties were maintained. Accelerated aging tests were made on all produced composites, accordingly to ISO13356 (2008). The amount of monoclinic zirconia, which is an indicator of degradation on these composites, was quantified by X-ray diffraction analysis for 5,12,24,48 and 96 hours of aging tests. It was determined that, the undoped ZTA samples did not present monoclinic zirconia after 96 hours on an aggressive environment. Regarding the ATZ composites, even though the monoclinic zirconia content increased proportionally to the zirconia content present in the composite, it was found that the extent of degradation was minimal, since it was relegated to the material surface. This fact allowed the maintaining of the mechanical properties of the material throughout all the duration of the aging tests. As expected, the less stable composite, the ATZ with 2YSZ, presented the highest content of monoclinic zirconia. Nonetheless, the mechanical properties tested on the aged composite confirmed that the degradation did not expand to the material bulk. The addition of both dopants, successfully improved the aging resistance of the ATZ composite, presenting a lower amount of monoclinic zirconia after 96 hours of aging tests in comparison with the undoped ones. However, the addition of Ta2O5 destabilized the 2YSZ present on the ZTA composites, and 10% of monoclinic zirconia was detected after 96 hours of aging tests. Still, the mechanical properties were maintained on all the doped composites, which again confirmed the presence of degradation only at the material surface. The biocompatibility of these composites was also tested. MG63 cells were seeded on the sintered samples and MTT and alkaline phosphatase activity (ALP) assays were performed. The cell viability/proliferation increased significantly from day 1 to day 4 for all the produced composites. The ZTA composites, with more anchorage sites, presented higher cell adhesion and proliferation in comparison with the ATZ composites. The addition of La2O3 and Ta2O5 did not induced significant changes on the cell viability of the ATZ composites. However, the addition of Ta2O5 on the ZTA composite led to a poor performance, due to its verified hydrophobicity. The present study shows that optimal compositions of these composites can be achieved, with improved mechanical properties, hydrothermal degradation resistance and satisfactory biocompatibility.

La durabilité à long terme des prothèses articulaires repose sur leur résistance vis-à-vis de la corrosion et leur comportement à l'usure. Quels que soient les matériaux utilisés, des produits de dégradation (ions métalliques et débris d’usure) se forment, du fait de la corrosivité des fluides corporels et de la biomécanique des articulations. Généralement, ces produits sont associés aux complications post-opératoires et en conséquence, leurs effets constituent des préoccupations cliniques critiques. A cet égard, la tribocorrosion est une considération sérieuse dans la performance des prothèses articulaires. Ce travail vise à contribuer à l'amélioration de la compréhension des mécanismes de dégradation d’un alliage de CoCrMo, utilisé en tant que prothèse articulaire, en appréhendant le couplage de charges mécaniques et l’activité cellulaire. Cette thèse a été entreprise selon une approche itérative, qui débute par l’étude du comportement électrochimique du milieu physiologique simulé, propice à la culture cellulaire (le RPMI-1640). L’alliage métallique et les cellules ont successivement été ajoutés au système d’étude. Les essais ont révélé que l'oxydation du CoCrMo est accélérée en présence d'espèces carbonées et de composés organiques, et que les cellules interviennent sur la libération d’ions métalliques. Un dispositif de biotribocorrosion a été développé dans le but d’évaluer l’influence des produits de dégradation sur le métabolisme cellulaire. Cette étude multidisciplinaire exhaustive a combiné des techniques expérimentales d’électrochimie, de biologie et de tribologie, afin de souligner l'importance de la chimie de surface du biomatériau sur sa résistance à la tribocorrosion et son caractère cytotoxique. Finalement, une méthodologie expérimentale a été proposée dans ce travail, en vue de mieux comprendre l’interaction entre les fluides physiologiques simulés et les biomatériaux
The long-term durability of joint replacements is based on their corrosion resistance and wear behavior. Whatever the materials used, degradation products (metal ions and wear debris) are formed due to the aggressiveness of body fluids and the biomechanics of the joints. Generally, these products are associated with post-operative complications and, as a result, their effects are critical clinical concerns. In this respect, tribocorrosion is a serious consideration in the performance of joint replacements. This work aims to contribute to the improvement of the understanding of the degradation mechanisms of a CoCrMo alloy, used as a joint prosthesis, by understanding the coupling of mechanical loads and cellular activity. This thesis has been structured according to a progressive approach, which begins with the study of the electrochemical behavior of a simulated physiological environment conducive to cell culture (RPMI-1640). Metal alloys and cells were successively added to the study system. The tests revealed that the oxidation of CoCrMo is accelerated in the presence of carbonaceous species and organic compounds, and that the cells are involved in the release of metal ions. A biotribocorrosion device has been developed to evaluate the influence of degradation products on cellular metabolism. This comprehensive multidisciplinary study combined experimental techniques from electrochemistry, biology and tribology to highlight the importance of biomaterial surface chemistry on tribocorrosion resistance and cytotoxicity. Finally, an experimental methodology was proposed in this work, in order to better understand the interaction between simulated physiological fluids and biomaterials