Biomedical Engineering Reference
In-Depth Information
Chapter 11
Bioactive Polyaryletherketone Composites
Ryan K. Roeder Ph.D. and Timothy L. Conrad B.S.
11.1 Introduction
commercial success of PAEK spinal implants in the
1990s, have led to growing interest in bioactive
PAEK composites over the last decade (
Table 11.1
),
which will be reviewed in this chapter.
Therefore, the objective of this chapter is to
introduce a paradigm for the design of bioactive
PAEK composites for biomedical devices (
Figs 11.1
and 11.2
) while reviewing the work to date within the
framework of that paradigm (
Table 11.1
). The design
of bioactive PAEK composites is considered within
the framework of processing
e
structure
e
property
relationships common to materials science and
engineering
[10]
. The processing, structure, and
properties of the materials used in a biomedical
device have great influence on the device perfor-
mance (
Fig. 11.1
). Of course, the device design is
also of great importance, but the materials are often
chosen “off the shelf” from known commodities
without designing the materials for optimal device
performance. The policies and practices of the US
Food and Drug Administration (FDA) pose limita-
tions to the introduction of new materials, but in this
case, PAEK and most calcium phosphates are well
known to the FDA. The “simple” combination of
PAEK and calcium phosphates offers wide ranging
As discussed in detail in previous chapters of this
topic, the clinical and commercial success of poly-
aryletherketone (PAEK) implants in interbody spinal
fusion was enabled by several advantageous proper-
ties. PAEK polymers are generally biocompatible,
bioinert, and radiolucent; PAEK polymers also
exhibit a high strength and similar compliance to
bone
[1
e
3]
. However, a potential clinical disadvan-
tage is that PAEK alone is not bioactive. In spinal
fusion, for example, autograft or recombinant human
bone morphogenetic protein (e.g., rhBMP-2) is
required for osteointegration and, ultimately, the
formation of a bony fusion
[2]
. Another potential
disadvantage of PAEK polymers is a limited ability
to tailor mechanical properties for a particular
implant design or to match peri-implant tissue.
Calcium phosphate reinforcement particles can be
used to simultaneously address both disadvantages
by providing (1) bioactivity and (2)
tailored
mechanical properties.
The addition of calcium phosphates
d
such as
hydroxyapatite
(HA),
b
-tricalcium phosphate
(
-TCP), and bioglass
d
to polymers offers a robust
system to engineer implant biomaterials with tailored
biological, mechanical, and surgical function
[4,5]
.
The historical design rationale has been to reinforce
a tough, biocompatible polymer matrix with a stiff,
bioactive filler. This concept was first conceived and
investigated by Bonfield and coworkers in the 1980s
with the development of HA-reinforced high-density
polyethylene (HDPE), which found clinical use
under the trade name HAPEX
b
PERFORMANCE
DEVICE
MATERIALS
PROCESSING
PROPERTIES
STRUCTURE
in non-load-bearing
otologic and maxillofacial implants
[6
e
9]
. The
superior mechanical properties of PAEK relative to
polyethylene,
Figure 11.1
Schematic diagram illustrating the mate-
rials science and engineering paradigm of proces-
singestructureeproperty relationships and their
influence on the performance of biomedical devices.
combined with the
clinical
and
