The effect of vessel holes on fracture behaviour in the femoral neck of the human femur
Abstract: Hip fractures are widely spread in today's society and affect a person's quality of life. Osteoporosis is a bone disease that results in more fragile bones and an increased risk of bone fractures, including hip fractures. A method proposed for assessing the fracture risk is finite element (FE) models of the femur. These FE models proved to be effective in predicting the overall mechanical behavior of human femurs, but are less accurate in predicting localization of stresses or strains. It is proposed that vessel holes in the femoral neck may affect the ability of FE models to predict fracture location, and that they need to be accounted for. There were two main aims for this thesis. The first, was to develop an automatic method for detection and quantification of blood vessel holes present in the proximal human femur. The second, was to investigate whether a micro-FE model, based on micro-CT images including features such as vessel holes, could more effectively identify local high strains as compared to an FE model based on lower resolution clinical CT images. Investigating these issues, the project focused on image analysis developing a method with which blood vessel holes could be quantified in a feasible and accurate way in both micro-CT and clinical CT images. This was done by investigating vessel hole canal structures and by thickness calculation of the cortical bone. The project also focused on developing and validating a finite element model of the femur bone, based on segmentation and mesh generation from micro-CT images. The project resulted in proposed methods for detecting and quantifying vessel holes, both based on micro-CT and clinical CT images. The methods were automatic, and the results showed a 100\% accuracy in the micro-CT, and 60\% accuracy in the clinical CT compared to the micro-CT. Furthermore, a micro-FE model, with a complex surface structure including the detected vessel holes, was developed showing higher accuracy in strain prediction, compared to an FE model based on clinical CT images. The conclusion was that vessel holes could be detected and quantified fully from micro-CT images and the largest vessel holes also in clinical CT images. Also, a micro-FE model generated based on micro-CT images, including the vessel holes in the femoral neck, correlated better than a similar model based on clinical CT images to experimentally measured strains.
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