Functional adaptation of the femur has been
investigated in several studies by embedding bone remodelling
algorithms in finite element (FE) models, with simpli-
fications often made to the representation of bone’s material
symmetry and mechanical environment. An orthotropic
strain-driven adaptation algorithm is proposed in order to
predict the femur’s volumetric material property distribution
and directionality of its internal structures within a continuum.
The algorithm was applied to a FE model of the femur,
with muscles, ligaments and joints included explicitly. Multiple
load cases representing distinct frames of two activities
of daily living (walking and stair climbing) were considered.
It is hypothesised that low shear moduli occur in areas
of bone that are simply loaded and high shear moduli in
areas subjected to complex loading conditions. In addition,
it is investigated whether material properties of different
femoral regions are stimulated by different activities. The loading and boundary conditions were considered to provide
a physiological mechanical environment. The resulting
volumetric material property distribution and directionalities
agreed with ex vivo imaging data for the whole femur.
Regions where non-orthogonal trabecular crossing has been
documented coincided with higher values of predicted shear
moduli. The topological influence of the different activities
modelled was analysed. The influence of stair climbing on
the properties of the femoral neck region is highlighted. It is
recommended that multiple load cases should be considered
when modelling bone adaptation. The orthotropic model of
the complete femur is released with this study.