ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

environment in comparison to fixed boundary models [9]. The use of a single load case
is limiting when describing the complex mechanical environment the whole femur is
subjected to physiologically. Inclusion of more load cases for a variety of activities
allows for a more accurate prediction of the distribution of the mechanical properties
and associated orientations by creating a loading envelope more representative of the
loading environment in vivo [6, 8].
Previous work by the authors [10] introduced a 3D bone remodelling algorithm with
bone modelled as a strain-adaptive continuum with local orthotropic material properties.
This approach showed promising results, with stiffness distribution and bone structure
directionality being physiologically predicted for a coronal plane of the proximal femur,
under simplified loading.
This study describes the algorithm’s application to a more physiological model and
loading configuration of the femoral construct. Predictions for the proximal femur and
condyles compare well with previous clinical observations of material property and
directionality distributions. This indicates that the loading conditions modelled are
closer to those experienced in vivo in comparison to fixed boundary condition models.
Consideration of multiple activity load cycles was show to be critical in bone
optimisation simulation; indicating that attempt to model more frames for each load
case and more extreme load cases should be included in order to achieve a more
accurate material property distribution.
3. METHODS
A 3D orthotropic bone remodelling algorithm [10] was applied to a free boundary
condition model of the femur [9] modified at the patella-femoral, tibio-femoral and hip
joints, undergoing many loading configurations corresponding to different instances of
three daily activity cycles.
3.1 Model
Figure 1 - Frontal and side view of the model (left) and of the tibio-femoral joint structure (right).