Biomedical Engineering Reference
In-Depth Information
3.7 Summary and Conclusions
Gross observations indicated normal muscle tissue
with no signs of infection or adverse tissue response,
and histology showed very few inflammatory cells.
The study also generated wear debris relating to an
investigation into osteotomy fixation in a functional
environment, but these wear particles elicited no
adverse tissue reaction.
Other studies have shown possible stimulatory
benefits in vivo relating to the use of CFR PEEK
polymer materials
[35]
. In these experiments, the
material was shown to be noncytotoxic, and in fact
increased the osteoblast cell protein content in
culture, leading to speculation that the material may
encourage ingrowth of bone around a prosthesis
d
in
this case a hip
d
thus, minimizing joint loosening and
decreasing the potential for revision surgery.
Additional research investigated human osteo-
blast-like cell and macrophage responses to CFR
PEEK polymer in vivo for a low elastic modulus
femoral total hip replacement application
[36]
. Using
disks made from CFR PEEK polymer and titanium
alloy (Ti6Al4V) controls, researchers found that
osteoblast attachment and proliferation were not
significantly different between the two.
It was also reported that while hydrogen peroxide
production by macrophages was raised on com-
posite surfaces, levels of alkaline phosphates
activity
d
Type I collagen production and osteocalcin
production
d
were not significantly different on the
composite surface compared with Ti6Al4V by the
end of the 11-day experimental period.
More recent studies on the use of alternative
materials to titanium
d
conducted on endosteal dental
implants (EDIs)
d
have indicated that modulus
effects and surface phosphonylation support
osseointegration and bone formation on PEEK
polymer and CFR PEEK polymer surfaces
[37,38]
.
They conclude that CFR PEEK polymer, having
surface immobilized calcium ions, should be viewed
as a clinically preferred alternative to titanium alloys.
Histopathology and histomorphometric studies by
the same researchers show no discernible histopath-
ological differences between titanium alloy and CFR
PEEK polymer EDIs, though they did report signif-
icant differences in the level of bone apposition and
osseointegration at 20 weeks. Surface phosphony-
lated CFR PEEK polymer showed 72% bone contact,
whereas titanium alloy showed only a 57% contact
area. They concluded that surface-treated CFR PEEK
polymer is preferred to commercially available tita-
nium alloy EDIs.
In summary, PEEK-OPTIMA polymer may be
enhanced by the introduction of fillers: barium
sulfate fine powder may be added to increase the
radiopacity of the polymer, making it more visible
under X-ray inspection in vivo, and carbon fibers
may be added to increase the strength and stiffness
of the polymer. Fibers may be short or continuous.
Short fiber-reinforced PEEK-OPTIMA compounds
can be injection molded, extruded, and machined,
giving modest increases in stiffness to match that of
bone, whereas continuous fiber-reinforced PEEK-
OPTIMA in the form of ENDOLIGN, with high
strength and stiffness competing with metallic
implantable materials, can be pultruded into rods,
filament wound into tubes, or hot pressed by various
means into flat plates or complex three-dimensional
shapes, for example screws, pins, or contoured bone
plates.
Because of its high strength, toughness, biocom-
patibility, imaging properties, optimal modulus, and
chemical resistance, CFR PEEK-OPTIMA polymer
offers several benefits compared with traditionally
used materials in the development of implantable
medical devices.
Although medical device manufacturers often
limited themselves to metallic alloys for the devel-
opment of high-strength implants, they now have
a superior alternative. With CFR PEEK-OPTIMA
polymer, medical device manufacturers no longer
have to sacrifice biocompatibility, imaging versa-
tility, or physical properties when selecting bioma-
terials
for
the
development
of
load-bearing
implantable medical devices.
References
[1] D.F. Williams, A. McNamara, R.M. Turner,
Potential of PEEK and CFRPEEK in medical
applications, J. Mater. Sci. Lett. 6 (2) (1987)
188
e
190.
[2] J. Wolff, Das gesetz der transformation der
inneren architektur der knochen bei pathologi-
schen veranderngen der ausseren knochenform,
first ed., Berliner Akademie der Wissenschaf-
ten, Reichsdruckerei, Berlin, 1884.
[3] H. Yildiz, S.K. Ha, F.K. Chang, Composite hip
prosthesis design. I. Analysis, J. Biomed. Mater.
Res. 39 (1998) 92
e
101.
