No description available.

No description available.

Osteoarthritis and cartilage deterioration are favored by meniscetomy, which is the ablation of the meniscus from the knee joint. Meniscectomy can be partial or total. This procedure is performed when meniscus lesions and tears or the degeneration of the meniscus caused by its natural dehydration occur. There is a peak of meniscal lesions observed between 20 and 29 years old. Alternative methods such as sutures fail in that they present a short term solution which is ideal for a less active, older generation. A long term solution is needed for a younger population to reduce the number of surgical procedures over the lifetime of this active group. There is a crucial need for a functional implant designed in the image of the native meniscus. Blends of poly (vinyl alcohol) PVA and poly (vinyl pyrrolidone) (PVP) present a potential solution. PVA has shown similar characteristics to soft tissues. PVP further stabilizes the hydrogel network. This work is the mechanical characterization of PVA/PVP (99:1) hydrogels under physiological conditions. Equilibrium swelling in a medium replicating the ionic and the osmotic content of the synovial fluid was investigated during 35 days. The mass retention of hydrogels was characterized using data obtained from the swelling study and was examined as a function of the cross link density and the polymer content. The modulus of hydrogels was obtained in unconfined compression, first at a strain rate slow enough to ignore fluid flow in and out of the gels, and subsequently at a physiological strain rate of walking. Results indicate that PVA/PVP hydrogels volume swelling ratio and weight swelling ratio show no significant difference for most formulations by the 14th day of immersion. A few hydrogels would reach equilibrium by day 21. Additionally, percentage polymer mass retention increases with the cross link density. However, there is no consistent trend with the polymer content. All formulations with 10% wt of polymer show the highest mass retention while 15% wt show the lowest. Interestingly, the mechanical characterization of hydrogels at 100%/min strain rate shows that 15% wt is the only formulation whose compressive modulus falls within the targeted range whereas 10% wt proves to not be stiff enough. 20% wt and 25% wt are always too stiff. Results obtained from unconfined compression at the physiological strain rate, that is 1920%/min, are rather inconclusive. There is not enough consistency in the literature to narrow the results down to one successful candidate formulation. The modulus range obtained at physiological strain rate encompasses the range obtained at 100%/min strain rate. The highest modulus value obtained is 10 times higher at physiological strain rate than the modulus of a real human meniscus obtained at 100%/min strain rate. It is not reasonable at this time to make a choice of a formulation at physiological strain rate due to high variability of the modulus of a human meniscus as a result of its intrinsic anisotropy. All formulations tested would be considered successful candidates, which is irrational considering the difference in their stiffness. / Mechanical Engineering

Knee osteoarthritis (OA) is a debilitating disease affecting the entire knee joint by inducing pathological changes to the cartilage and menisci. Currently, the etiology of OA is not completely understood. However, altered gait mechanics, specifically increased joint loading, of OA patients have a clear association with both symptomatic and structural OA progression. Non-surgical intervention tools, such as variable stiffness shoes (VSS), have been developed as a way to decrease loading within the knee joint. However, with external moments being surrogate measures for knee loading, it is unclear if changes in knee moments with the footwear are sufficient to result in a clinical benefit. Therefore, this project’s purpose was to investigate whether a VSS intervention can alter knee joint loading and menisci function in a knee OA population. We used gait analysis, musculoskeletal modeling, and finite element (FE) analysis to determine the effect of VSS on gait mechanics, knee joint contact force, and menisci stress and strain, compared to a control shoe. We found knee moments did not decrease with the VSS intervention. Furthermore, participants who did experience a decrease in knee adduction moment did not always experience a decrease in medial compartment contact force. However, results from our FE modeling of the tibiofemoral joint indicate significant changes in knee joint contact force can influence stress placed on the menisci. Results from this study suggest knee contact forces and tissue stress, not only external moments, should be considered when investigating if VSS can positively impact an OA population.

Denna rapport presenterar det examensarbete som gjorts i samarbete med företaget Artimplant. Syftet med arbetet är att ta fram en prototyp av ett meniskimplantat i trikåteknik. Det kräver stickning av en given form och att prototypen ska inneha vissa egenskaper.Ämnesområden som berörs under arbetets gång är textiltillverkning med inriktning mot väfttrikå samt medicinsk textil. Förutom textila ämnesområden tas även ämnen som knäledens anatomi och meniskens uppbyggnad, funktion och skador upp. Kunskaper inom dessa områden krävs för att på bästa sätt ta fram prototyper av meniskimplantat.Att sticka det triangulära tvärsnittet och den böjda formen som krävs för ett meniskimplantat har varit ett arbete som pågått under hela projektet. För att åstadkomma detta och erhålla egenskaper som krävs för en prototyp av ett meniskimplantat har diskussioner förts med produktutvecklare och tekniker, både på Artimplant och på Textilhögskolan för att diskutera möjligheter och utformning. Även möte med ortoped och en av initiativtagarna till Artimplant har givit värdefull information kring hur en prototyp till ett meniskimplantat bör utformas. Dessutom diskuteras och analyseras frågor kring industrialisering av processen och framtagning av kravspecifikation samt hur prototyper förhåller sig till den framtagna kravspecifikationen.Varje enskild prototyp granskas efter framtagning och utvalda prototyper genomgår tester där resultaten jämförs mellan dessa samt enligt kravspecifikation. Detta tillvägagångssätt möjliggör ständiga förbättringar för varje prototyp som tas fram.En slutlig prototyp av ett meniskimplantat har tagits fram och dess egenskaper och utformning möter den framtagna kravspecifikationen. Dess grepp och känsla är liknande en naturlig menisk då den är töj- och formbar, elastisk samt har en slät yta. Formbarheten på prototypen möjliggör anpassning av storlek och positionering vilket medför bra integration till ledytorna. Ytterligare likheter som prototypen har med en naturlig menisk är dess förmåga att stå emot deformation vid kompression.This report presents the thesis that was executed at the company Artimplant. The purpose of this work is to produce a prototype of a meniscus implant in knitted technology. It demands knitting a specific shape and that the prototype shall possess certain properties.The subjects that the report covers are textile manufacturing with focus on weft knits and medical textile. Besides subjects concerning textile technology there are also subjects as the anatomy of knee joint and the meniscus structure, function and damage. Knowledge in these areas is required to develop a prototype of a meniscus implant in the best way as possible.Knitting the triangular cross section and getting the curved shape that a meniscus implant requires have been under constant development during the project. To achieve this design and to obtain required properties for a prototype of a meniscus implant have discussion been held with product developer and technicians, both at Artimplant and at the Swedish School of Textile, to discuss the opportunities and design. Meetings with an orthopaedic, who also was one of the initiators of Artimplant, have provided valuable information regarding the design of a prototype of a meniscus implant. Furthermore, issues related to industrialization of the process, composing a requirement specification and how prototypes are related to the requirement specification are discussed and analyzed.Each produced prototype is analyzed and thereafter prototypes are selected for further tests. The results from the tests are compared between the selected prototypes and according to the requirement specification. This line of action allows continuous improvement for each produced prototype.A final prototype of a meniscus implant has been developed and its properties and design fulfil all of the criteria in the requirement specification. Its hand is similar to a natural meniscus because of its stretchability, elasticity, flexibility and the surface smoothness. The flexibility of the prototype allows adjustments of size and positioning which results in good integration to the knee-joint. Further resemblance is the prototype’s ability to resist deformation during compression. / Program: Textilingenjörsutbildningen

Nous étudions expérimentalement le comportement d'un film liquide, dit de Landau-Levich, lorsqu'il s'évapore dans une atmosphère constituée uniquement de sa vapeur.La dynamique de ce type de film est un paramètre-clef qui gouverne le fonctionnement des caloducs oscillant (en anglais PHP - Pulsating Heat Pipes). Les PHP sont des liens thermiques de forte conductance. Les recherches récentes leur attribuent un pouvoir de refroidissement très élevé, ce qui les rend particulièrement convoités par l'industrie. Leur géométrie est simple : il s'agit d'un tube capillaire enroulé en plusieurs branches entre une partie froide (condenseur) et une partie chaude (évaporateur). Le tube est rempli d'un fluide pur diphasique, c'est-à-dire présent sous la forme d'une succession de bulles de vapeur et de bouchons de liquide. Lorsque la différence de température entre l’évaporateur et le condenseur dépasse un certain seuil, les bulles et bouchons commencent à osciller dans le tube, entre les deux parties, ce qui permet au PHP de transférer la chaleur.Notre installation expérimentale représente un PHP dans sa configuration la plus simple, à branche unique. Une interface liquide-vapeur oscille dans un tube de section rectangulaire, et dépose un film liquide à chaque passage. Nous nous intéressons au mécanisme qui permet l'entretien de l'oscillation de l'interface, et fixe sa fréquence. L'équation de mouvement obtenue prend en compte la dissipation visqueuse engendrée par un écoulement oscillant. Dans les modèles actuels de PHP, l'hypothèse d'un écoulement de type Poiseuille est formulée. Or, notre approche montre que l'hypothèse d'un écoulement faiblement inertiel est mieux adaptée, conduit à une dissipation deux fois supérieure.Le dispositif expérimental permet l'observation du film. Une combinaison originale de méthodes optiques permet également de mesurer sa longueur et son épaisseur, et de reconstruire son profil 3D à chaque instant. Nous pouvons suivre l'évolution du film tout au long de sa durée de vie, et ainsi analyser son comportement dynamique. Le film est presque plat (pente inférieure à 0,1°). Sur toute sa longueur, qui est de quelques centimètres, cela correspond à une variation de son épaisseur de moitié, la valeur moyenne étant de 50 microns. Sous l'effet du chauffage, le film se rétracte progressivement. Dès le début de son évaporation, un bourrelet de démouillage est formé sur le pourtour du film, près de la ligne triple. L'apparition de ce bourrelet est caractéristique d'un démouillage visqueux sous conditions de non-mouillage. Ce comportement est surprenant, dans la mesure où nous avons choisi un fluide mouillant parfaitement la paroi en conditions isothermes. A l'échelle nanométrique, au plus près de la ligne triple, l'angle de contact entre le liquide et la paroi est donc très faible. Nous mesurons cependant un grand angle apparent (c'est-à-dire visible à l'échelle millimétrique), qui augmente avec la surchauffe de la paroi. Dès l'augmentation de cet angle, le bourrelet de démouillage se forme, et le film se rétracte. Ce phénomène est expliqué par l'évaporation à l'échelle microscopique. Les résultats expérimentaux sont en accord quantitatif avec la théorie développée par d'autres chercheurs. / We experimentally study the behavior of liquid films - so called Landau-Levich films - when they evaporate in their pure vapor atmosphere.The dynamics of this film is a key parameter that rules out the functioning of Pulsating Heat Pipes (PHPs). PHPs are high conductive thermal links. Their heat transfert capability is known to be extremely high. For this reason they are promising for numerous industrial applications. Their geometry is simple. It is a capillary tube bent in several branches that meander between a hot part (called evaporator) and a cold part (called condenser), and filled up with a pure two-phase fluid. When the temperature difference between evaporator and condenser exceeds a certain threshold, gas bubbles and liquid plugs begin to oscillate spontaneously back and forth inside the tube and PHP starts transferring the heat.Our experimental setup features the simplest, single branch PHP. A liquid/vapor interface oscillates in a tube. It deposits a liquid film at each passage. We focus first on the mecanism which makes possible self-sustained interface oscillations and defines its frequency. The obtained motion equation accounts for the viscous dissipation caused by oscillatory flow. In existing PHP modelling, a laminar flow is supposed. Yet, our approach shows that the assumption of weakly inertial flow is preferable and leads to a dissipation rate twice larger that the Poiseuille flow.The experimental setup allows the film visualization. An original combination of optical measurement techniques lets us measure the film length, thickness and 3D-profile at all times. The film evolution has been measured during its whole lifetime. The film is nearly flat (its slope is smaller than 0,1°). The film length is of several centimeters, and the average thickness is 50 microns. Thus, along the total length, its thickness decreases by half. Under heating conditions, the film gradually recedes. A dewetting ridge is formed, near the triple contact line. Such a behavior is typical under non-wetting conditions. At the nanometric scale the contact angle between the liquid and the solid wall is very low. However, we measure a large apparent contact angle (visible at the millimetric scale) which increases with the wall superheating. Once this angle increases, the dewetting ridge is formed and the film recedes. The large apparent contact angle is explained by evaporation in the microscopic vicinity of the contact line. The measured apparent contact angle value agrees quantitatively with theoretical results obtained by other researchers.

Orientador: Bruno Watanabe Minto / Resumo: O presente estudo objetiva estabelecer padrões elastográficos normais das principais estruturas da articulação femorotibiopatelar (joelho) de cães saudáveis, em diferentes faixas etárias. Foram examinados 30 cães (60 articulações) da raça Beagle sem alterações musculoesqueléticas, os quais foram distribuídos em três grupos: jovens, adultos e idosos. Realizou-se elastografia ARFI do ligamento patelar, menisco medial, ligamento cruzado caudal e ligamento cruzado cranial de cada articulação. Análises qualitativas e quantitativas detectaram correlação positiva da velocidade de cisalhamento, ou seja, da rigidez das estruturas, com a idade dos cães. O ligamento patelar apresentou aumento gradual de sua rigidez em relação à idade; já o menisco e os ligamentos cruzados mostraram-se mais rígidos nos filhotes do que nos adultos, mas também revelaram suas maiores rigidezes nos animais idosos. Avaliou-se também a diferença de elasticidade das estruturas de acordo com o gênero e a condição reprodutiva dos animais. As fêmeas apresentaram todas as estruturas mais rígidas que os machos, com velocidades de cisalhamento diferindo entre 0,30 e 0,36 m/s dentre os dois gêneros; e apenas o menisco medial não se mostrou mais rígido nos animais castrados em relação aos inteiros, sendo a diferença daquele de apenas 0,02 m/s e a dos ligamentos de 0,40 a 0,47 m/s entre os grupos. Já quanto ao peso, não houve significância estatística em relação à elasticidade das estruturas. Tais achados corroboram os ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study is to establish normal elastographic patterns of the main knee structures of healthy dogs in different age groups. Thirty Beagles (60 joints) without musculoskeletal diseases were divided into three groups: young, adult and elderly. We performed ARFI elastography of the patellar ligament, medial meniscus, caudal cruciate ligament and cranial cruciate ligament. Qualitative and quantitative analyzes were performed, detecting a positive correlation of the shear velocity (rigidity of the structures) and the age of the dogs (p = 0.012). The patellar ligament showed a gradual increase in its rigidity in relation to age; the meniscus and the cruciate ligaments were more rigid in the pups than in adults, but also showed greater rigidity in elderly animals. The difference in elasticity of structures according to sex and reproductive condition was also evaluated. The females had all the structures more rigid than the males, with shear velocities differing between 0.30 and 0.36 m / s between the two groups. Only the medial meniscus did not appear to be more rigid in castrated animals. There was no statistical significance regarding the elasticity of the structures, according to weight. ARFI elastography is feasible technique in canine knees, not only as a method for the early diagnosis of ligament and meniscal alterations, but also to evaluate repercussion of instability in the contralateral limb and the impact of surgical and physiotherapeutic treatments. It is be... (Complete abstract click electronic access below) / Mestre

Disease and degeneration of articular cartilage and fibrocartilage tissues severely compromise the quality of life for millions of people. Although current surgical repair techniques can address symptoms in the short term, they do not adequately treat degenerative joint diseases such as osteoarthritis. Thus, novel tissue engineering strategies may be necessary to combat disease progression and repair or replace damaged tissue. Both articular cartilage and the meniscal fibrocartilage in the knee joint are subjected to a complex mechanical environment consisting of compressive, shear, and tensile forces. Therefore, engineered replacement tissues must be both mechanically and biologically competent to function after implantation. The goal of this work was to investigate the effects of oscillatory tensile loading on three dimensional engineered cartilaginous tissues in an effort to elucidate important aspects of chondrocyte and fibrochondrocyte mechanobiology. To investigate the metabolic responses of articular chondrocytes and meniscal fibrochondrocytes to oscillatory tensile loading, various protocols were used to identify stimulatory parameters. Several days of continuously applied tensile loading inhibited extracellular matrix metabolism, whereas short durations and intermittently applied loading could stimulate matrix production. Subpopulations of chondrocytes, separated based on their zonal origin within the tissue, differentially responded to tensile loading. Proteoglycan synthesis was enhanced in superficial zone cells, but the molecular structure of these molecules was not affected. In contrast, neither total proteoglycan nor protein synthesis levels of middle and deep zone chondrocytes were substantially affected by tensile loading; however, the sizes of these new matrix molecules were altered. Up to 14 days of intermittently applied oscillatory tensile loading induced modest increases in construct mechanical properties, but longer durations adversely affected these mechanical properties and increased degradative enzyme activity. These results provide insights into cartilage and fibrocartilage mechanobiology by elucidating cellular responses to tensile mechanical stimulation, which previously had not been widely explored for these tissues. Understanding the role that mechanical stimuli such as tension can play in the generation of engineered cartilaginous tissues will further the goal of developing successful treatment strategies for degenerative joint diseases.

No description available.

Post-traumatic osteoarthritis (PTOA) of the knee is a complication resulting from direct injury to the joint, such as anterior cruciate ligament and meniscus tears, and accounts for approximately 12% of all OA cases. The economic and clinical impact of PTOA is also greater than idiopathic OA, as patients are younger and often more active, requiring treatments for symptomatic OA over a greater fraction of their lifetime. A common strategy to manage pain and inflammation associated with PTOA is the intraarticular administration of corticosteroids. However, these injections are limited due to the requirement of high-doses imposed by synovial joint clearance rates and their resulting systemic side effects. In addition, currently used broad-spectrum corticosteroids are palliative and not curative, stemming from incomplete knowledge of specific mechanisms that drive cartilage degeneration and other joint pathologies. Thus, most patients with PTOA eventually undergo surgical procedures such as osteochondral graft transplantation for focal defects and in more severe cases, total knee arthroplasty. As such, the studies presented in this dissertation (i) offer specific insights into mechanisms by which traumatic injury can drive joint degeneration and (ii) present novel strategies to modulate joint responses to pathological factors by leveraging sustained drug-delivery platforms. In Part I, mechanistic assessments of human cartilage and synovium responses to insults are conducted to identify novel pathways that may lead to impaired joint homeostasis. First, a direct consequence of traumatic injury, hemarthrosis, is explored as a potential contributor to the development of PTOA specifically through contributions by red blood cells. We demonstrate for the first time the differential roles of erythrocytes in their intact and lysed states through measures of oxidative stress and changes to metabolomic profiles in the context of ferroptosis. Furthermore, we demonstrate the therapeutic potential of Ferrostatin-1, a lipophilic radical scavenger in inhibiting pathological changes to cartilage and its crosstalk with the neighboring synovium in an in vitro model of hemophilic arthropathy. Second, a strategy to prevent an indirect consequence of traumatic injury, arthrofibrosis, is presented in an in vitro model of joint contraction. Fibrosis and the presence of hyperplastic synovium are implicated in the progression of OA through pathological shifts in tissue composition as well as secreted factors that promote cartilage degeneration and the maintenance of a pro-inflammatory joint environment. A type I transforming growth factor beta-1 receptor inhibitor, SB-431542, is encapsulated in polymeric microspheres for the prophylactic treatment of arthrofibrosis through sustained low-dose drug delivery to circumvent the challenges associated with resident joint clearance rates. Utilizing human-based in vitro models of cartilage and synovium pathology, we present novel mechanisms and therapeutic strategies to prevent pathological changes following traumatic joint injury that may contribute to the development of PTOA. In Part II, the sustained delivery platform introduced in Part I is extended to the treatment of PTOA. Osteochondral graft transplantation is currently the clinical gold standard for large focal cartilage lesions. However, allograft procedures are limited due to the lack of available donor tissues and autografts are associated with complications due to donor-site morbidity. In both cases, grafts are subject to failure, potentially in part due to the continual presence of pro-inflammatory factors following surgical procedure. In this section, we present cellular agarose hydrogels embedded with dexamethasone-releasing microspheres that are integrated with a titanium base as a functional tissue-engineered alternative to native osteochondral allografts. These allogenic tissue-engineered grafts were assessed in an in vivo preclinical canine model in their ability to maintain clinical function and to modulate the inflammatory response over the course of 12 months. We successfully demonstrated the feasibility of using engineered grafts by comparing clinical measures of range of motion, function, lameness, and pain, as well as modified cartilage graft scores, against native osteochondral allograft controls. In addition, improvements in the histopathological scoring of neighboring synovial and meniscal tissues indicate the therapeutic capacity of dexamethasone released from within the joint to modulate the inflammatory response up to one-year post-implantation. Taken together, the studies presented in this dissertation identify novel mechanisms behind pathological changes to the cartilage and synovium that may contribute to the development of PTOA following injury. Potential therapeutic targets, inhibitory compounds, and delivery strategies are also assessed using human-based in vitro models of disease and further validated in an in vivo canine model through a clinically relevant timeframe. Ultimately, we demonstrate for the first time, the use of dual-function tissue-engineered grafts in a weight-bearing region of the knee joint to circumvent limitations associated with the clinical gold standard for the treatment of large focal cartilage defects.