Biomedical Engineering Reference
In-Depth Information
O
Y
Z
X
X
X
Y
O
Y
O
Z
Z
Region
Head
LC-1
LC-2
LC-3
Muscles
Glut. Min.
Glut. Med.
Glut. Max.
Ant.
Med.
Post.
Figure 2.8
Spatial distribution of load cases.
posterior regions. The insertion points and the directions of the application of
loadings follow the study presented by Dostal and Andrews [56], whereas the load
values follow the observations of Pedersen
et al
. [55] in which 25% of the BM is
considered for the gluteus maximus and medius and 12.5% of the BM for the
gluteus minimus.
In contrast with the model presented by Bagge [18], which used 10 load cases,
this model considers only three load cases obtained from the average of the 10
cases mentioned above (this simplification provides a significative reduction in the
computational cost of the next step in which interfacial nonlinear conditions are
included). The weighting factors related to each load case (1, 2, and 3) are 20%,
60%, and 20%, respectively.
The loads applied (Table 2.1) must be equilibrated by the reaction forces of the
knee joint, which in this model are imposed through a clamped condition on the
external ring of the femoral diaphysis. The coordinate system is oriented so that
the
x
axis is in the lateral-medial direction, the
y
axis is in the anterior-posterior
direction, and the
z
axis in the upper-lower direction.
The solution of the optimization problem with the volume constraint of 50% is
given in Figure 2.9. In this case, it is possible to see the formation of the layers
of cortical bone with high density along the diaphysis. Also, the formation of
a low-density medullary canal, the formation of metaphyseal cortical plates, low
density in the Ward's triangular region, and the complex distribution of density in
