Prediction of fracture propagation in human femur using the Finite Element Method

Sammanfattning: Hip fractures constitute a major problem, both in terms of a lower life quality for the people affected and socio-economical factors. Osteoporosis is a medical condition, defined by decreased bone mass, which results in a more fragile bone structure and a higher risk for fractures. Osteoporosis accounts for a cost of € 1.5 billion each year in Sweden alone, and the costs are increasing. In order to prevent fractures from occurring, new robust methods for fracture risk assessments are needed. The majority of the computational methods available today show promising results, but do not account for the individual bone geometry or materials and are often not able to capture the complicated mechanical response of bone fractures. In this project, a subject-specific FE modeling method was combined with a PUFEM-based code that worked on homogeneous materials. A convergence study was performed in order to find a suitable step-size in the solution method, as well as a material parameters study to confirm the accurate mechanical response of the models. The goal of the material parameter study was also to assess the influence in terms of location of fracture initiation point and fracture pathway. At the current state, several models have been produced and tested, both homogeneous and heterogeneous models. In the homogeneous models, identical material parameters were used for cortical and trabecular bone, whereas in the heterogeneous models different stiffnesses were used for cortical and trabecular bone tissues. With these models, it was possible to calculate crack initiation and crack path as well as e.g. the stress distribution. To conclude, subject-specific FE-models showed promising result as a method to predict fractures and could lead to an improved understanding of the mechanical responses of bone.