Haste press-fit recta versus curva na revisão do componente femoral na ATJ

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TEchMA2020: 3rd International Conference on Technologies for the Wellbeing and Sustainable Manufacturing Solutions: book of abstracts

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Estudo biomecânico da artroplastia do cotovelo com prótese total não-constrangida iBP

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Book of abstracts of the 2nd International Conference of TEMA: mobilizing projects

Based on its Human Capital and Capacities, the Centre for Mechanical Technology and Automation (TEMA) embraces a mission aiming to contribute to a sustainable industry, with specially focus on the surrounding SMEs, and to the wellbeing of society. Sustainable manufacturing aims to contribute to the development of a sustainable industry by developments and innovations on manufacturing engineering and technologies, to increase productivity, improve products quality and reduce waste in production processes. Technologies for the Wellbeing wishes to contribute to the wellbeing of society by the development of supportive engineering systems focusing on people and their needs and intending to improve their quality of life. TEMA intends to maximize its national and international impact in terms of scientific productivity and its transfer to society by tackling the relevant challenges of our time. TEMA is aware of the major challenges of our days, not only confined to scientific issues but also the societal ones, (a strategic pillar of the Horizon 2020 program), at the same time placing an effort to have its research disseminated, in high impact journals to the international scientific community. (...)publishe

Toolpath and machining parameters optimisation of the cavities of a knee prosthesis tibial insert

The main purpose of this paper is to demonstrate the applicability of conventional cutting tools in the machining of a custom tibial insert of a knee prosthesis. This study also aims to reduce the roughness and minimize the production time. In this work the optimisation of cutting strategies and parameters was achieved through the design and construction of a test-part containing the most important complex surfaces of the femoral cavities, the focus of the study. The milling was carried out in accordance with the Design Of Experiment and the Taguchi method and was performed in two stages to reduce the number of analysed factors. The achieved parameters are applied to the machining of a modelled tibial insert made of UHMWPE, using a NC machine with three axes. The initial parameters studied were the cutting method, axial and radial depth of cut, the direction of the feed and the feed rate. Three strategies were studied: two Blend, resulting in radial and spiral toolpaths, and one Parallel. According to the spiral strategy, an arithmetical mean roughness of R a = 1.1 μm was obtained, representing an improvement of 45% relatively to the initial phase value of 2.0 μm, with the Parallel toolpath. An overall improvement of 34% in time efficiency of the finishing operation was achieved after changing the machine settings. This study supports the conclusion that high-speed milling is an expeditious process to produce customized tibial inserts.publishe

Estudo numérico e experimental da biomecânica da prótese do joelho

Doutoramento em Engenharia MecânicaNesta tese foi objectivo estudar os aspectos biomecânicos da prótese do joelho e a problemática da artroplastia do joelho, nomeadamente a sua revisão. Para o efeito, diversos estudos biomecânicos sobre hastes da artroplastia total do joelho foram realizados através de modelos numéricos e experimentais. Foi seleccionada a prótese do joelho P.F.C. Sigma Knee System como elemento para a realização do estudo comparativo das hastes. Foram validados modelos numéricos de elementos finitos através da comparação das defromações-extensões de modelos da tíbia e do fémur sintéticos instrumentados com extensómetros. O estudo referente às hastes usadas na revisão incluiu as cimentadas e press-fit, tendo-se determinando a repartição de carga, deformações nas diferentes interfaces, tensões no manto de cimento e os micromovimentos relativos. Estes parâmetros mecânicos foram determinados de forma individual para a tíbia e para o fémur e foram correlacionados com efeitos clínicos como reabsorção óssea, descolamento e a dor. Os mesmos foram também analisados em conjunto, determinando-se a influência biomecânica que a haste exerce sobre o osso contrário. O estudo foi finalizado com uma avaliação préclínica dum novo conceito de implante de fixação combinada aplicado à haste tibial. Os resultados obtidos evidenciaram que a capacidade de transferência de carga dos componentes condilianos da prótese do joelho é somente efectiva com as hastes cimentadas. No entanto, a estabilidade proporcionada pelas hastes press-fit é superior à proporcionada pelas hastes cimentadas. A haste press-fit induz deformações mais elevadas no osso cortical, na zona da extremidade, podendo estas estarem na origem da dor sentida pelos pacientes. A haste cimentada evidencia um efeito de stress-shielding mais pronunciado na zona vizinha dos componentes condilianos; no entanto, as hastes press-fit originam uma maior extensão deste efeito no osso. Este facto pode ser correlacionado clinicamente com o efeito de reabsorção óssea associada às zonas vizinhas dos componentes condilares. Os resultados permitiram igualmente concluir que a utilização de hastes na tíbia pouco alteram a estabilidade do componente femoral. Já a utilização de hastes no fémur aumentam a instabilidade dos componentes tibiais, levando a aconselhar os cirurgiões à utilização de hastes tibiais sempre que se utilizam hastes no fémur. O novo conceito de haste adaptado à tíbia evidenciou uma estabilidade que se situa entre os dois conceitos convencionais, com uma capacidade efectiva de transferência de carga, minimiza os efeitos de necrose térmica originados pelo cimento e permite um contacto directo entre a haste e o osso, facilitando a osteointegração, e evita a destruição massiva de osso em caso da sua retirada (revisão), quando comparada com as hastes cimentadas.The main objective of this thesis was to study different biomechanical aspects of the knee prosthesis and revision arthroplasty. Finite element and experimental studies were performed concerning the use of stems in revision knee arthroplasty. The P. F. C. Sigma Knee System prosthesis was used within the study. Numerical finite element models were validated by the measurement of principal strains on synthetic tibia and femur models. Press-fit and cemented stems were analyzed and load share, interface strains, cement mantle stresses and relative micromotions were assessed. These mechanical parameters were determined solely for the tibia and for the femur and correlated with clinical effects such as bone resorption, loosening and pain. Same parameters were also assessed considering the tibia and the femur stems as a set and the influence of the stem was analyzed over the other bone structure. Finally, a pre-clinical evaluation of a new combined fixation concept applied to the tibial stem was made. For this, the results evidence that load transfer capacity of the condylar components of the knee prosthesis is only effective for cemented stems. However, press-fit stems provide higher stability. These types of stems induce higher cortical strains in the distal-tip region of cemented stems, and can be responsible for pain referred by patients at this region of the stem. Cemented stem provoke higher stress shielding in the region close to the condylar components. However, this effect is more extensive in bone and can be clinically correlated with the effect of bone resorption in the condylar region. The results also allowed drawing the conclusion that the use of tibial stems does not change the stability of the femoral component. On the contrary, femoral stems raise instability of the tibial components, and therefore it is advisable to use tibial stems if femoral stems are used. The new tibial stem concept evidenced a degree of stability in between the two conventional stems analyzed. The novel stem provokes effective load transfer, minimizes bad effects of thermal necrosis due to cement polymerization and allows direct bone contact, facilitating potential osteointegration. It also minimizes bone destruction in revision, when the stem needs to be taken ou

The role of poroelasticity on the biomechanics of the intervertebral disc : a finite element study

The major goal for the present work is to evaluate a biomimetic Finite Element (FE) model of the Intervertebral Disc (IVD). Recent studies have emphasized the importance of an accurate biomechanical modeling of the IVD, which is a highly complex biphasic medium. A novel biphasic poroelastic model was implemented and coupled with Wilson’s model (2005) for biphasic osmotic swelling behavior. Numerical tests were devoted to the analysis of the time- dependent behavior of the IVD. The results show good agreement with literature experimental data (Heuer et al., 2007 or O’Connell et al., 2011) and also with other numerical studies (Galbusera et al., 2011). In brief, this in-development IVD FE model aims to be a valuable tool to study the biomechanics of the IVD and its pathways for degeneration.Fundação para a Ciência e a Tecnologia (FCT

Biomechanical behaviour of cancellous bone on patellofemoral arthroplasty with journey prosthesis : a finite element study

Isolated patellofemoral (PF) arthritis of the knee is a common cause of anterior knee pain and disability. Patellofemoral arthroplasty (PFA) is a bone conserving solution for patients with PF degeneration. Failure mechanisms of PFA include growing tibiofemoral arthritis and loosening of components. The implant loosening can be associated with bone resorption, or fatigue-failure of bone by overload. This research work aims at determining the structural effects of the implantation of PF prosthesis Journey PFJ (Smith&Nephew, USA) on femur cancellous bone. For this purpose, the finite element (FE) method is considered to perform computational simulations for different conditions, such as well-fixed and loosening scenarios. From the global results obtained, in the well-fixed scenario, a strain decrease on cancellous bone was noticed, which can be related to bone resorption. In the loosening scenario, when the cement layer becomes inefficient, a significant increase of cancellous bone strain was observed, which can be associated with bone fatigue-failure. These strain changes suggest a weakness of the femur after PFA.Fundação para a Ciência e a Tecnologia (FCT

Cell seeding process optimization on polycaprolactone-gelatin-arcade-like-architecture-scaffolds

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A life cycle thinking approach applied to novel micromobility vehicle

While the production of cars has high environmental costs, producing and maintaining micromobility vehicles might consume fewer resources. Likewise, replacing the car with active mobility transportation modes reduces noise and air pollution. The Life Cycle Assessment (LCA) methodology contributes to study such environmentally sustainable solutions. We present a "cradle-to-grave" analysis by tracking the activity from the extraction of raw materials until the product's life ends. The goal is to carry out an LCA of a novel micromobility vehicle under a life cycle thinking perspective. The LCA tool - Good to Go? Assessing the Environmental Performance of New Mobility, developed by the International Transport Forum - was used to model the baseline and alternative scenarios. The vehicle’s materials, primary energy sources for battery charging, use of the vehicle as a shared mobility mode, among other factors, were changed to assess the energy use and greenhouse gases (GHG) emissions during the entire life cycle chain. The LCA results at the baseline scenario for the micromobility device, the Ghisallo vehicle, are similar to the values of other micromobility vehicles. Energy consumption (Mega Joule [MJ]) and GHG emissions (grams of equivalent CO2) per vehicle-kilometer are 0.36 [MJ/v-km] and 29 [g CO2 eq/v-km], respectively. For this personal mobility vehicle, it is a conclusion that most GHG emissions are due to production (42% of the total). Air transport from production to sales site increases the impact by 10%. Finally, we present measures to decrease the energy and GHG emissions impact of a micromobility device life cycle.in publicatio