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Advisor(s)
Abstract(s)
A locomoção humana carateriza-se pela capacidade de um ser humano conseguir movimentar-se de um local para outro e isto deve-se, principalmente, às articulações. Todas estas articulações constituem o sistema esquelético do corpo humano, sendo a anca uma das maiores e mais importantes articulações. Porém, existem várias doenças articulares que comprometem a mobilidade, como é o caso da osteoartrose. Esta é caraterizada por uma dor intensa assim como perda de funcionalidades, existindo vários tratamentos para ajudar, mas quando este tipo de tratamento deixa de ser eficiente e esta doença começa a agravar-se surge a necessidade de intervenção cirúrgica – a Artroplastia Total da Anca. A Artroplastia Total da Anca corresponde a uma das cirurgias mais bemsucedidas realizadas em ortopedia e carateriza-se pela substituição da anca defeituosa por um componente acetabular artificial e uma cabeça e haste femoral. Esta técnica pode ser cimentada onde é aplicado um elemento de ligação entre o osso e a prótese para fixar a prótese ou pode ser não cimentada onde o encaixe é feito sob pressão. Contudo, como todas as operações cirúrgicas, esta também apresenta algumas complicações, sendo as mais usuais as fraturas, infeções e luxação, levando à falha da prótese. Deste modo, este trabalho consistiu em avaliar a biomecânica das próteses da anca não cimentadas e cimentadas de titânio e cobalto-cromo quando são aplicadas certas cargas, recorrendo ao Método dos Elementos Finitos. Para isto, importou-se modelos 3D do fémur e da prótese no software COMSOL Multiphysics, ajustou-se o posicionamento e encaixe do conjunto, gerou-se uma malha computacional extremamente fina e foram aplicadas cargas estáticas e dinâmicas. Com a geometria e malha definidas, foram gerados resultados e obteve-se diagramas de tensão de von Mises, de deformação e de deslocamento correspondentes ao comportamento de um implante quando sujeito a forças referentes ao pico de um ciclo de marcha. Para além disto, foi feito as mesmas análises, mas para condições dinâmicas como uma caminhada a uma velocidade constante de 5 km/h. Por último, foi avaliado as zonas mais propícias da prótese de titânio a ocorrer falha sob condições de fadiga.
The human locomotion is defined by the ability of a human being able to move from one place to another and is mainly due to the joints. All these joints together form the skeletal system of the human body, and the hip is one of the largest and most important joints. However, there are several joint diseases that compromise mobility, such as osteoarthritis. This disease is characterized by intense pain and loss of functionality, requiring several treatments, but when these treatments are no longer effective and the disease begins to escalate, the need for surgical intervention emerges - Total Hip Arthroplasty. Total Hip Arthroplasty is one of the most successful surgeries performed in orthopaedics and is characterized by the replacement of the defective hip with an artificial acetabular component and a femoral head and stem. This technique can be either cemented, where a connecting element is applied between the bone and the prosthesis to fix the prosthesis, or it can be cementless, where the fitting is done under pressure. However, as in any surgical operation, it also has complications, and the most common are fractures, infections, and dislocations, leading to failure of the prosthesis. Thus, this study aimed to evaluate the biomechanics of uncemented and cemented titanium and cobalt-chromium hip prostheses when certain loads are applied, using the Finite Element Method. To do this, 3D models of the femur and prosthesis were imported into COMSOL Multiphysics software, the positioning and fit of the assembly were adjusted, an extremely fine computational mesh was generated, and static and dynamic loads were applied. With the geometry and mesh defined, results were generated, and von Mises stress, strain, and displacement diagrams were obtained corresponding to the behaviour of an implant when subjected to forces referring to the peak of a walking cycle. In addition, the same analyses were performed but for dynamic conditions such as climbing stairs and walking at a constant speed of 5 km/h. Finally, the most likely areas of the titanium prosthesis to fail under fatigue conditions were evaluated.
The human locomotion is defined by the ability of a human being able to move from one place to another and is mainly due to the joints. All these joints together form the skeletal system of the human body, and the hip is one of the largest and most important joints. However, there are several joint diseases that compromise mobility, such as osteoarthritis. This disease is characterized by intense pain and loss of functionality, requiring several treatments, but when these treatments are no longer effective and the disease begins to escalate, the need for surgical intervention emerges - Total Hip Arthroplasty. Total Hip Arthroplasty is one of the most successful surgeries performed in orthopaedics and is characterized by the replacement of the defective hip with an artificial acetabular component and a femoral head and stem. This technique can be either cemented, where a connecting element is applied between the bone and the prosthesis to fix the prosthesis, or it can be cementless, where the fitting is done under pressure. However, as in any surgical operation, it also has complications, and the most common are fractures, infections, and dislocations, leading to failure of the prosthesis. Thus, this study aimed to evaluate the biomechanics of uncemented and cemented titanium and cobalt-chromium hip prostheses when certain loads are applied, using the Finite Element Method. To do this, 3D models of the femur and prosthesis were imported into COMSOL Multiphysics software, the positioning and fit of the assembly were adjusted, an extremely fine computational mesh was generated, and static and dynamic loads were applied. With the geometry and mesh defined, results were generated, and von Mises stress, strain, and displacement diagrams were obtained corresponding to the behaviour of an implant when subjected to forces referring to the peak of a walking cycle. In addition, the same analyses were performed but for dynamic conditions such as climbing stairs and walking at a constant speed of 5 km/h. Finally, the most likely areas of the titanium prosthesis to fail under fatigue conditions were evaluated.
Description
Keywords
Artroplastia Total da Anca Articulação da anca Fémur Prótese cimentada Prótese não cimentada COMSOL Multiphysics Fadiga Stress Strain Total hip arthroplasty Hip joint Femur Cemented prosthesis Cementless prosthesis Fatigue