Biomedical Engineering Reference
In-Depth Information
the bone resorption. Conversely, the more flexible the prosthesis, the higher the
shear strain in the interface/prosthesis region, hindering bone formation.
To evaluate the influence of this parameter on the model response, two simu-
lations were carried out: one around a Ti alloy shaft (
E
=
120 GPa) and another
around a CrCo shaft (
E
200 GPa).
In Figures 2.13 and 2.14, it can be observed that the Ti preserves a greater
quantity of bone mass than the CrCo shaft. An hypertrophy was noted in the distal
part of the femur, with a tendency toward a filling of the medullary canal and more
pronounced bone resorption in the proximal part of the femur in the case of the
CrCo prosthesis. A loss in bone mass of 9.2% for the CrCo prosthesis and 5.79%
for the Ti prosthesis was noted.
For the interfacial region, the bone growth is sparse, in both cases. This situation
is consistent with many clinical outcomes showing that bone ingrowth occurs
only in a small portion of porous surface. In both cases, bone resorption in the
proximal part produces a weak mechanical support and, consequently, conditions
nonfavorable to bone ingrowth at these points (Figure 2.15).
Comparing the results of both cases, it is verified that with the Ti prosthesis the
bone ingrowth occurs in a smaller region of the porous coating, as expected for a
more flexible stem.
=
Density
(Avg : 75%)
+1 . 000e + 00
+9 . 003e
−
01
+8 . 005e
−
01
+7 . 008e
−
01
+6 . 010e
−
01
+5 . 013e
−
01
+4 . 015e
−
01
+3 . 018e
−
01
+2 . 020e
−
01
+1 . 023e
−
01
+2 . 506e
−
03
3
2
1
(a)
(b)
(c)
Figure 2.13
(a) Bone density distribution postoperatively.
(b) Bone remodeling for CrCo prosthesis. (c) Bone remodel-
ing for Ti prosthesis.
