Biomedical Engineering Reference
In-Depth Information
0.06
30 V
60 V
0 V
-30 V
-60 V
0.04
0.02
ε
0.00
-0.02
-0.04
-0.06
0
500
1000
1500
2000
t
(day)
(a)
0.04
30 V
60 V
0 V
-30 V
-60 V
0.02
0.00
η
-0.02
-0.04
-0.06
0
500
1000
1500
2000
t
(day)
(b)
FIGURE 4.4
Variation of ε and η with time
t
for several potential differences. (a) ε versus
t;
( b) ε versus
t.
• The values of ε and η against
t
for δ =
a
*
-
a
= 0.001, 0.003, and
0.005 mm are shown in Figure 4.5. It can be seen that both the
inner and the outer surface radii of the bone are reduced after
the pin has been inserted, which will increase the tightness of
fit. A tightly fitted pin can also increase the rate of bone surface
remodeling, which can accelerate the recovery of the injured
bone. On the other hand, as the radius of the pin increases, the
outer surface radius of the bone decreases more significantly
than does the inner surface radius. This results in a decrease
of the bone's cross-sectional area and, hence, in a thinner and
weaker bone structure. Furthermore, if the fit is too tight, the
