Biomedical Engineering Reference
In-Depth Information
Fig. 7.63 a Anteroposterior postoperative radiograph, with nine months of evolution, showing
consolidated fracture, with clear radiological signs of avascular necrosis of the femoral head [
32
].
b Anteroposterior postoperative radiograph, with twelve months of evolution, after a full hybrid
hip arthroplasty reoperation [
32
]. c Exeter
TM
Femoral Stem V40
TM
irregular nodal distribution presented in Fig.
7.65
a. Notice that the implant domain
is discretized with 1,525 nodes and the support bone with 3,402 nodes.
In this section, all the studied examples consider an initial uniform density
distribution q
max
app
¼ 2
:
1 g/cm
3
and a Poisson ratio t ¼ 0
:
3. For the a and b
parameters ruling the growth and the decrease of the bone tissue it is considered:
a = b = 0.01. Additionally, four distinct medium bone density control values
were
assumed: q
control
app
¼ 1
:
20 g/cm
3
;
q
control
app
¼ 1
:
10 g/cm
3
;
q
control
app
¼ 1
:
00 g/cm
3
and q
control
app
¼ 0
:
90 g/cm
3
.
In the first analysis the model is submitted to the three loads suggested by
Beaupré et al. [
14
,
15
], which can be found in Fig.
7.39
. Since it is being simulated
an intertrochanteric fracture combined with the loss of functionality of the great
trochanter, all the forces applied in the great trochanter are disregarded. Thus, only
the forces applied in the femur head are considered, Fig.
7.65
b. In the present
analysis, the forces suggested by Beaupré and co-workers are applied directly in
the implant following a uniform distribution. The magnitude, the direction and the
number of cycles of each considered load case are presented in Table
7.5
.
Regarding the essential conditions, the model the model is constrained in the
basis, along x and y directions, Fig.
7.65
b.
The mechanical properties of the bone tissue depend on the current apparent
density and are obtained with the considered phenomenological law. The
mechanical properties of the titanium implant stem are: E = 110 GPa and
t ¼ 0
:
32. It was not considered in the analysis a cemented interface between the
implant and the bone tissue.
In order to simulate the permanent natural cortical layer that can be found in the
femur bone, whose function is to provide protection and additional rigidity to the
