Biomedical Engineering Reference
In-Depth Information
E
D
C
B
A
400
μ
m
Figure 2.6
Backscattered electron micrograph of implanted glass ICIE1Sr10 in
osteoporotic rat femur: A
=
glass, B
=
Si gel layer, C
=
HCA layer, D
=
existing
bone and E
new bone growth into marrow cavity. (Adapted with permission from
[21]. Copyright (2009) Imperial College London.)
=
to the basal level after 19 weeks. There was no elevated concentration
of silicon in the organs (brain, heart, kidney, liver, lung, muscle and
thymus) at 24 weeks. Figure 2.6 shows an electron microscope image
of a strontium-containing bioactive glass cylinder that was implanted in
an osteoporotic rat femur after four weeks. The image nicely shows the
different regions of a bioactive glass that has reacted with blood and
bonded to bone: a silica gel layer formed at the surface of the glass (due
to ion exchange of Na
+
and Ca
2
+
ions from the glass with H
+
from
the blood), with an apatite layer in between this and the existing bone.
This shows evidence of osteointegration with direct bone contact. New
bone has formed and is growing into the defect and marrow cavity area,
indicating osteoconduction.
2.5.2 Human Clinical Studies and Commercial Products
As Larry Hench writes in the Foreword, the first Bioglass product was
a middle ear prosthesis [22]. Although it worked, it was only available
in two sizes of cone-shaped implants and every clinical case was slightly
different, requiring a device that could be shaped by the surgeon. This
limited the commercial success of the device and is also a problem for
all bioceramic implants: surgeons want to be able to shape and/or inject
the device.
