Ex vivo radius fracture prediction using numerical simulation including realistic boundary conditions ; Prédiction de fracture ex vivo de radius par simulation numérique intégrant des conditions de chargements réalistes

Fragility fractures represent a public health problem for elderly. The assessment of the bone strength and of the risk of fracture by the gold standard method (Dual X-ray Absorptiometry - DXA) has certain limitation. Other methods such as specific finite element modeling have shown good prediction of bone strength, but it is not possible to confirm that they do better than the density measured by DXA to estimate the risk of fracture. Thus, the aim of this thesis was to evaluate whether some numerical parameters (such as meshing, boundary conditions, imaging, areas of interest, material law, failure criterion) could improve fracture prediction. The entire work was based on previous ex vivo experiments on 30 left radii reproducing as faithfully as possible a fall and leading to two distinct groups: the fractured and the unfractured. Then, the predictive ability of a micro-finite element model on a 9 mm section of the distal radius created using the High Resolution peripheral Quantitative Computed Tomography (82 µm isotropic) was evaluated by a sensitivity analysis. Different loading conditions were simulated, and no significant improvement was found on the fracture risk prediction. The area of interest was then enlarged to an 8 cm section of bone from a lower resolution scanner (150 µm isotropic). On these homogenized finite element models, different material laws as well as different fracture criteria were tested. No significant improvement was once again found on the fracture prediction compared to DXA. This study provides original data on the creation of numerical models dedicated to further improvements of fracture risk prediction. ; Les fractures de fragilité représentent un problème de santé publique pour les personnes âgées. L'évaluation de la résistance osseuse et du risque de fracture par la méthode de référence (absorption biphotonique à rayons X, DXA) présente certaines limites. D’autres méthodes comme la modélisation spécifique en éléments finis a montré de bonnes prédictions de la résistance osseuse, ...