Biomedical Engineering Reference
In-Depth Information
(a)
(b)
Figure 12.8
(a) Low and higher magnification images showing histology of a solid PEEK sample after 12 weeks
implantation. (b) Porous PEEK histological sections at low and high magnification showing implantebone interface.
properties in more depth, “small” and “large” pore
variants of porous PEEK were manufactured. Small
pore material of average pore size 70
m
m was man-
ufactured as described in case study 1. The larger
pore samples were manufactured by blending fine
developmental grade PEEK-OPTIMA powder
(Invibio, UK) with 2000
m
m diameter particles of
soluble sodium phosphate bioglass, followed by
compression molding. It should be noted that if
PEEK is combined with certain traditional alkaline
bioglasses, they can cause an adverse reaction. This
is described in patent US2010/0168798
[38]
. The
selection and use of suitable bioglasses that do not
cause a reaction with PEEK is described in another
patent WO2010/043900, and it includes the ability to
use the group of soluble sodium or calcium phos-
phate bioglasses as controlled release agents and
porogens
[39]
. The different-sized porous material
samples were compared with each other and a bovine
trabecular bone control, using high-resolution micro-
computed X-ray analysis (energy
average pore size of 678
m
m and a connective
density of 7 mm
3
, with a total porosity of around
80% (
Figs 12.10 and 12.11
). For the porous PEEK
samples, the “small” pore samples had a mean
pore size of 70
m
m and a connective density of
1400 mm
3
with a total porosity of around 45%.
Although some porosity is present for these smaller
pore samples, the size and interconnectivity are very
different from those of trabecular bone. This
difference may not be too detrimental to the ability
of the material to permit bone ingrowth as was
previously observed in case study 1 and indeed
creates a porous material more similar to that of the
porous polyethylene on the marketplace for use in
CMF application. However, while creating a mate-
rial that may have suitability for some applications,
it does not mimic the architecture of trabecular
bone, which is examined here. The larger pore
variant possessed a pore size of 636
m
mand
a connective density of 87 mm
3
with a total
porosity of around 75%. While the connectivity was
still not as good as the trabecular bone control, the
pore size and percentage porosity were very similar
to those observed for the trabecular bone controls.
¼
45 kV, intensity
¼
176
m
A).
The results have been previously reported
[40]
.
The bovine trabecular bone control samples had an
