Estudo da interface osso-cimento na artroplastia cimentada

Abstract

Atualmente, a interface cimento-osso é um dos assuntos com mais investigação na área da biomecânica. Apesar de existirem alguns estudos, pouco se sabe ainda sobre os fenómenos que acontecem a nível microscópico. Estudos experimentais e numéricos feitos anteriormente verificaram que é nesta interface que ocorrem as maiores deformações quando sujeitas a forças de compressão e tração. Assim, este estudo teve como objetivo estudar o comportamento da interface osso-cimento, numérica e experimentalmente, quando sujeita a ensaios equivalentes aos esforços que atuam a nível da anca. De forma a avaliar a influência da densidade de osso esponjoso e dos diferentes níveis de penetração de cimento no osso, foram desenvolvidos modelos numéricos e experimentais de forma a realizar os ensaios. Verificou-se experimentalmente que quanto maior é a densidade do osso, maior é a resistência da interface cimento-osso, ou seja, a resistência desta interface é dependente do osso e não do cimento. Numericamente conclui-se que para penetrações de cimentos mais elevadas, menores são as tensões e as deformações na interface. Por último, realizaram-se micro-Cts a duas das amostras resultantes dos ensaios de forma a calcular o volume de osso esponjoso removido durante os ensaios de tração e os níveis de penetração, no entanto este último objetivo não foi atingido.

Currently, the cement-bone interface is one of the most studied domains in the area of biomechanics. Even though some studies have been conductud regarding the subject, information about the phenomenons that occur at a microcopic level is still scarce. Previous experimental and numerical studies concluded that this interface is the one in which the most relevant deformations occur when subjected to compression and traction forces. Thus, the present study aimed to understand the behaviour of the cement-bone interface, both numerically and experimentally, when subjected to tests that mimic the forces that have an impact on the hip. To access the influence of density of trabecular bone and of diferent levels of cement penetration on the bone, numerical and experimental models were developed in order to perform the tests. Experimentally, the results demonstrated that the resistance between the cement-bone interface is proportional to the bone density, meaning the resistance is greater with higher densities. Therefore, the interface depends on the bone and not on the cement when applying the same force. Numerically, the results indicate that for deeper cement penetration, lower are the tensions and deformations displayed, whilst using the same force. Lastly, micro-CTs were performed in two of the samples that resulted from the tests, in order to find the volume of trabecular bone removed during the tests of traction and the levels of penetration, even though the latest was not achieved. Currently, the cement-bone interface is one of the most studied domains in the area of biomechanics. Even though some studies have been conductud regarding the subject, information about the phenomenons that occur at a microcopic level is still scarce. Previous experimental and numerical studies concluded that this interface is the one in which the most relevant deformations occur when subjected to compression and traction forces. Thus, the present study aimed to understand the behaviour of the cement-bone interface, both numerically and experimentally, when subjected to tests that mimic the forces that have an impact on the hip. To access the influence of density of trabecular bone and of diferent levels of cement penetration on the bone, numerical and experimental models were developed in order to perform the tests. Experimentally, the results demonstrated that the resistance between the cement-bone interface is proportional to the bone density, meaning the resistance is greater with higher densities. Therefore, the interface depends on the bone and not on the cement when applying the same force. Numerically, the results indicate that for deeper cement penetration, lower are the tensions and deformations displayed, whilst using the same force. Lastly, micro-CTs were performed in two of the samples that resulted from the tests, in order to find the volume of trabecular bone removed during the tests of traction and the levels of penetration, even though the latest was not achieved.