Biomedical Engineering Reference
In-Depth Information
4
3
Optimized
Totally
coated
Optimized
Half
coated
Initial
2
1
Figure 10.13
Initial and optimized stems. Minimization of remodeling function
f
r
.
coated prostheses. In Figure 10.13 it is possible to observe that optimized shapes
are similar for both coating lengths.
The optimized shapes tend to be minimal invasive hip prostheses, as shown
in Figure 10.13. In fact, minimal invasive prostheses are less stiff and reduce the
stress shielding effect. In these results, the distal half stem is very small in order to
increase proximal load transfer. In the proximal part, sections are thin (parameter
b
)
and there is also no elbow to obtain a more favorable load transfer. Comparative
contact stresses presented in Figure 10.14 show an increase in stress on proximal
region. However, the stress in distal tip is almost zero for minimal invasive optimal
shapes. In summary, with the remodeling cost function stem geometries with more
proximal load transfer were obtained in order to reduce the stress shielding effect.
< 10 MPa
< 20 MPa
0 MPa <
10 MPa <
20 MPa <
Initial
Optimized
Initial
Optimized
Totally coated
Half coated
Figure 10.14
Normal contact stress in stem-bone interface
for the initial and the optimized shape obtained for the
minimization of remodeling function
f
r
(load case 1).
