  Bone adapts in response to its mechanical environment. This evolution of bone
density is one of the most important mechanisms for developing fracture
resistance. A finite element framework for simulating bone adaptation, commonly
called bone remodelling, is presented. This is followed by a novel method to
both quantify fracture resistance and to simulate fracture propagation. The
authors' previous work on the application of configurational mechanics for
modelling fracture is extended to include the influence of heterogeneous bone
density distribution. The main advantage of this approach is that
configurational forces, and fracture energy release rate, are expressed
exclusively in terms of nodal quantities. This approach avoids the need for
post-processing and enables a fully implicit formulation for modelling the
evolving crack front. In this paper density fields are generated from both (a)
bone adaptation analysis and (b) subject-specific geometry and material
properties obtained from CT scans. It is shown that, in order to correctly
evaluate the configurational forces at the crack front, it is necessary to have
a spatially smooth density field with higher regularity than if the field is
directly approximated on the finite element mesh. Therefore, discrete density
data is approximated as a smooth density field using a Moving Weighted Least
Squares method. Performance of the framework is demonstrated using numerical
simulations for bone adaptation and subsequent crack propagation, including
consideration of an equine 3rd metacarpal bone. The degree of bone adaption is
shown to influence both fracture resistance and the resulting crack path.
