Biomedical Engineering Reference
In-Depth Information
Chapter 1
An Overview of PEEK Biomaterials
Steven M. Kurtz Ph.D.
1.1 Introduction
biomaterials flourished and is expected to continue to
advance in the future
[10]
.
Numerous studies documenting the successful
clinical performance of PAEKs in orthopedic and
spine patients continue to emerge in the literature
[11
e
16]
. Recent research has also investigated the
biotribology of PEEK composites as bearing mate-
rials and flexible implants used for joint arthroplasty
[17
e
20]
. Because of the interest in further improving
implant fixation, PEEK biomaterials research has
also focused on compatibility of the polymer with
bioactive materials, including hydroxyapatite, either
as a composite filler or as a surface coating
[21
e
25]
.
As a result of ongoing biomaterials research, PEEK
and related composites can be engineered today with
a wide range of physical, mechanical, and surface
properties, depending upon their implant application.
The purpose of this
Handbook
is to introduce
PEEK as an established member of the biomaterials
armamentarium to students, engineers, and surgeons.
Our aim is to cover the terminology, history, and
recent advances related to its use in implantable
devices for trauma, spine, and orthopedics. We hope
that this monograph will serve two useful purposes.
Our primary objective is to provide biomaterials
researchers with a timely synthesis of the existing
literature for PEEK, to help stimulate further
studies to fill existing gaps in knowledge and expe-
rience. Our second goal is to provide the surgical
community with state-of-the-art information about
PEEK to facilitate accurate communications with
patients.
In this introductory chapter, we begin with the
basics about polymers and PEEK. This chapter
reviews basic information about polymers in general
and describes the structure and composition of
PEEK. The concepts of crystallinity and thermal
Following confirmation of its biocompatibility
two decades ago
[1]
, polyaryletherketone polymers
(PAEKs) have been increasingly employed as
biomaterials for orthopedic, trauma, and spinal
implants. Polyaryletheretherketone, commonly
referred to as PEEK, is a member of the PAEK
polymer family that has been used for orthopedic and
spinal implants. Historically, the availability of PEEK
arrived at a time when there was growing interest in
the development of “isoelastic” hip stems and fracture
fixation plates, with stiffnesses comparable with bone
[2]
. Although neat (unfilled) PEEK biomaterials can
exhibit an elastic modulus ranging between 3 and 4
GPa, the modulus can be tailored to closely match
cortical bone (18 GPa) or titanium alloy (110 GPa) by
preparing carbon fiber-reinforced (CFR) composites
with varying fiber length and orientation
[2]
.Inthe
1990s, researchers characterized the biocompatibility
and in vivo stability of various PAEK materials, along
with other “high-performance” engineering poly-
mers, such as polysulfones and polybutylene tere-
phthalate
[3]
. However, concerns were raised about
the stress-induced cracking of polysulfones by lipids
[4]
, and the use of these polymers in implants was
subsequently abandoned.
By the late 1990s, PEEK had emerged as the
leading high-performance thermoplastic candidate
for replacing metal implant components, especially
in orthopedics
[5,6]
and trauma
[7,8]
. Not only was
the material resistant to simulated in vivo degrada-
tion, including damage caused by lipid exposure, but
starting in April 1998, PEEK was offered commer-
cially as a biomaterial for implants (Invibio Ltd.,
Thornton Cleveleys, United Kingdom)
[9]
. Facili-
tated by a stable supply,
research on PEEK
