Publication: Análisis experimental y numérico de la fractura de fémur humano
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2017-01
Defense date
2017-01-27
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Abstract
La fractura ósea es un traumatismo muy habitual que afecta cada año a un
mayor número de pacientes en el mundo entero. Esto se debe principalmente al
envejecimiento de la población, aunque influyen otros muchos factores. Estos traumatismos
están acompañados de largos tiempos de recuperación, minusvalías o
incluso mortalidad post-cirugía, además del coste social que suponen. Por todo ello
la fractura ósea, y por tanto la fractura de materiales biológicos resulta un campo
de estudio muy interesante a la vez que útil.
Esta tesis doctoral se centra en el ámbito de la mecánica de la fractura elástica
lineal aplicada al tejido óseo. Para modelizar este proceso de fractura mediante
el método de los elementos finitos se ha implementado el método de los Phantom
Nodes. En esta tesis, este método ha sido validado mediante diferentes problemas
de fractura, tanto cuasi-estáticos como de propagación en materiales homogéneos
y heterogéneos. Mediante esta técnica y un criterio de orientación basado en la
heterogeneidad de los materiales es posible la modelización de fracturas en hueso
a una escala microscópica.
Pasando a una escala macroscópica, el hueso humano también es un material altamente
heterogéneo, y por ello también el fémur humano, hueso en el que se centra
este trabajo. Mediante ensayos experimentales se ha medido el comportamiento de
un fémur artificial y dos especímenes reales, tanto en su régimen elástico como en
fractura. La calidad de estos especímenes ha sido analizada en profundidad, para
así_ poder explicar el comportamiento de cada uno de ellos.
Mediante modelos numéricos de ambos fémures ha sido posible la modelización
de los especímenes, tanto en su régimen elástico como en su comportamiento a fractura.
En el proceso de fractura se ha implementado un proceso iterativo que tiene
en cuenta la heterogeneidad del material, mediante el cual es posible reproducir
con un alto grado de similitud los resultados experimentales.
La aplicación de unas propiedades realistas en los modelos numéricos, así como
un criterio adecuado que tenga en cuenta los materiales del espécimen permiten
predecir la fractura del fémur humano. Esto, acompañado de un análisis cualitativo
puede suponer la predicción de un tipo de fractura concreto y realizar un tratamiento
preventivo.
Bone fracture is a common traumatism that affects a large number of patients in the world each year. This is principally due to the aging population, although other factors have also an inuence on it. This traumatism is accompanied by long recovery times, disability or even mortality post-surgery, apart from the social cost that it involves. All these reasons make bone fracture, and therefore the fracture of biological materials, a really important and useful field of study. This dissertation focuses on the field of linear elastic fracture mechanics applied to bone tissue. To model this fracture process through the finite element method, a Phantom Node approach has been developed. This method has been validated with different fracture problems, both in homogeneous and heterogeneous materials. This method makes it possible the fracture modelling in bone at microscopic scale, through an orientation criterion based on the material heterogeneity. Moving on to a macroscopic scale, human bone can be also considered a heterogeneous material. The behaviour of an artificial femur and two real specimens has been recorded by experimental tests, both in elastic regimen and during the fracture process. The quality of these real specimens has been analysed, in order to explain their behaviour. The modelling of the specimens has been carried out, using numerical models of the femur. An iterative process has been developed for the fracture process, in order to take into account the material heterogeneity. This method enables the reproduction of the experimental results with a high degree of concordance. The application of real properties in numerical models as well as an appropriate criterion to take into consideration the different materials in a specimen allows the fracture prediction in a human femur. This can help to predict bone fracture and to carry out a preventive treatment.
Bone fracture is a common traumatism that affects a large number of patients in the world each year. This is principally due to the aging population, although other factors have also an inuence on it. This traumatism is accompanied by long recovery times, disability or even mortality post-surgery, apart from the social cost that it involves. All these reasons make bone fracture, and therefore the fracture of biological materials, a really important and useful field of study. This dissertation focuses on the field of linear elastic fracture mechanics applied to bone tissue. To model this fracture process through the finite element method, a Phantom Node approach has been developed. This method has been validated with different fracture problems, both in homogeneous and heterogeneous materials. This method makes it possible the fracture modelling in bone at microscopic scale, through an orientation criterion based on the material heterogeneity. Moving on to a macroscopic scale, human bone can be also considered a heterogeneous material. The behaviour of an artificial femur and two real specimens has been recorded by experimental tests, both in elastic regimen and during the fracture process. The quality of these real specimens has been analysed, in order to explain their behaviour. The modelling of the specimens has been carried out, using numerical models of the femur. An iterative process has been developed for the fracture process, in order to take into account the material heterogeneity. This method enables the reproduction of the experimental results with a high degree of concordance. The application of real properties in numerical models as well as an appropriate criterion to take into consideration the different materials in a specimen allows the fracture prediction in a human femur. This can help to predict bone fracture and to carry out a preventive treatment.
Description
Mención Internacional en el título de doctor
Keywords
Biomecánica, Análisis numérico, Simulación por ordenador