Biomedical Engineering Reference
In-Depth Information
Chapter 9
Thermal Plasma Spray Deposition
of Titanium and Hydroxyapatite on
Polyaryletheretherketone Implants
Pierfrancesco Robotti MS and Gianluca Zappini MS
CFR-PEEK commercialized under the brand Motis
(Invibio Ltd., Thornton, UK) has been released to be
used in arthroplasty applications articulating with
CoCr or ceramic counterfaces (Chapter 16).
All the previously quoted examples need, during
implantation, stable fixation against host bone tissue
in order to ensure clinical success. One possibility to
obtain implant fixation is through its direct osteoin-
tegration. This biological phenomenon takes place
when bone tissues succeed in colonizing an amount
of device surface sufficient to establish a mechanical
constraint limiting any further relative movement.
Another possibility is through indirect osteointegra-
tion. This happens, for example, with inert bioma-
terials when a thin fibrous layer is interposed between
host bone and material. Even without direct bone to
implant contact device, stabilization is achieved with
good clinical performance if the implant
9.1 Introduction
Polyaryletheretherketone (PEEK) is currently
used as a basic material for several medical devices
intended for compromised tissue substitution. As
highlighted in Chapter 13, examples of clinical
applications for PEEK are frequent in spine surgery.
In this field, PEEK spinal cages for intervertebral
disk replacement are commonly employed. These
devices are positioned between two vertebral bodies
with the aim to maintain the correct anatomical
distance during the guided intervertebral fusion
process. Such devices often feature a cavity that may
be loaded with osteoconductive
e
osteoinductive
fillers to promote and accelerate osteosynthesis.
PEEK radiolucency is appreciated, as it allows
clinicians to monitor the fusion status and, more
easily, diagnostic investigations
[1,2]
. PEEK is also
under evaluation as a bearing material in spine
arthroplasty (see also Chapter 13)
[3
e
5]
. Another
example of a clinical application for PEEK is the
Epoch
femoral stem (Zimmer Inc., Warsaw, USA)
(see Chapter 14)
[6]
.
Carbon-fiber-reinforced PEEK (CFR-PEEK) is
another type of PEEK. This composite is used when
structural performance plays a key role in the
medical device. CFR-PEEK has been clinically used
as a bearing material in hip joint replacements
[7,8]
and is under evaluation in unicondylar knee
replacements
[9,10]
. Recently, a specific type of
is sur-
rounded by sufficient hosting bone.
PEEK can be listed among the biocompatible inert
biomaterials and some concerns have been raised about
the inertness of PEEK and limited fixation with bone.
With bioinert materials, if large enough relativemotion
(sometimes also referred to as “micromotion”) takes
place between device and tissues, the fibrotic tissue is
prone to diffuse and grow in thickness, thus enabling
further increased micromotion and potentially loos-
ening of the prosthesis. One possibility for limiting this
vicious circle is by using osteoconductive surfaces.
An osteoconductive surface promotes bone
e
surface
