Cranial Implant manufactured with Laser Sintering using EOS Additive Manufacturing in PEEK Plastic

1. Customer reference
Multidisciplinary team puts its heads together
to create first laser-sintered cranial implant
Now that knee and hip replacement have become increasingly routine, the next challenge in artificial
human bone is certainly the skull. Whether through birth defect, accident or disease, any defect of
the cranium jeopardizes the fragile brain and needs fixing as quickly as possible. The reconstruction
of such a large-scale head injury, called cranioplasty, also helps restore the contours of the skull. Yet,
since every patient’s injury is unique, replacing that lost bone must be done on a case-by-case basis.
Laser-sintering technology enables the economic production of parts with a batch size of one. But
the benefits for the patient due to the exact fit made possible by the customized design of each implant
are much more significant.
Industry Medical
Application Mass customisation
Short project profile
The Custom-IMD project was
partially funded by the European
Commission and involved 22
partners from seven European
countries. The goal was to achieve
supply chain integration of fully
customizable implants, with
cranial, dental and spinal appli-
cations.
Challenge
Manufacturing of a patient-
specific cranioplasty with a
highly-complex structure that
promotes bone ingrowth into
the implant.
Solution
Speedy manufacturing of indivi-
dual skull implants made of PEEK
on an EOSINT P 800 from EOS.
Results
• Comfortable: fewer side effects
due to patient-specific manu-
facturing and use of PEEK
• Osseointegrative: Design and
polymer filling promote bone
ingrowth
• Biocompatible: PEEK is non-
cytotoxic, non-haemolytic, non-
pyrogenic, non-irritant and
causes no sensitization response.
• Economic: reduced production
costs due to fewer labour and
material expenses
• Integrated: automated design
and manufacturing within a
few hours
Further information
www.customIMD.com
Image source: EOS GmbH
rature-conductive after implan-
tation. This can lead to long-term
issues with fit and comfort in the
skull. More recently, the focus has
turned to plastic cranial implants
made from polyetheretherketone
(PEEK). PEEK’s lighter weight,
strength and biocompatibility
make it an attractive alternative
to titanium. As this high-perfor-
Challenge
Titanium-plate cranial implants
have been the most-used solution
to date. But the material and the
machining methods approved to
produce them can be expensive
and time-consuming. Furthermore,
although biocompatible, titanium
is relatively stiff compared to bone
and in some forms can be tempe-
mance polymer can be processed
on a laser-sintering system, the
freedom of design that this tech-
nology offers allows the produc-
tion of individualized implants
with highly complex lattice struc-
tures that promote the ingrowth
of bone into the implant structure.
FACTS

2. EOS GmbH Electro Optical Systems
Robert-Stirling-Ring 1
D-82152 Krailling/Munich
Phone +49 89 893 36-0
Fax +49 89 893 36-285
www.eos.info • info@eos.info
Solution
The first ever laser-sintered PEEK
cranial implant prototype has now
been created by a team of doctors,
design engineers and materials
specialists working together in a
European Union-funded research
project called Custom-IMD. Pre-
requisite for the design of the
cranioplasty was the planning
software of the London-based
company Within Technologies. It
is based on an algorithmic pro-
cedure that defines the internal
structure of an object. On the one
hand it imitates nature, more pre-
cisely the fibre composite struc-
ture of the bone and, on the other
hand, it relies on deterministic
principles of structural enginee-
ring. That controls not only the
design of the internal lattice
(resolution, strut thickness and
topology), but also the width of
the part’s walls or skin in a fluid
and continuous fashion.
A rim was added around the edge
of the implant to give it a solid
border for optimum fit to existing
skull bone. “With this version we
saw no stress peaks in the struc-
ture at all,” says Jörg Lenz, EOS
Collaborative Projects Coordinator.
“FEA simulations, and then mecha-
nical testing to confirm that our
boundary conditions and other
assumptions were correct, showed
that we had come up with a
strong, functional implant design.”
The implant prototype could with-
stand greater than 100 MPa of
pressure with minimal deflection,
and any stress at impact dissipated
quickly without being transferring
to the brain.
Conventionally machined or moul-
ded implants made of either tita-
nium or PEEK can include holes
to accommodate the tendency for
bone ingrowth. But because laser-
sintering is an additive layer manu-
facturing process, it can produce
much more intricate structures.
And this complexity is essential
to promote osseointegration — the
infiltration of a patient’s own bone
cells (osteoblasts) into the struc-
ture of an implant over time. To
further promote bone growth, the
finished structure was infiltrated
with a bioabsorbable polymer filled
with fifty percent hydroxylapatite*.
The rough surface produced by
laser-sintering promotes the firm
connection of the implant with
this polymer. The osteoblaths are
expected to infiltrate the polymer,
connect with the implant itself, and
eventually replicate many charac-
teristics of the original bone.
Due to the rapid production turn-
around times of the EOSINT P 800,
prototypes of PEEK cranioplasties
can now be produced within just
a few hours.
Results
Dr. Siavash Mahdavi, stakeholder
and Within Technologies’ mana-
ging director, explains: “Now that
both custom implant design and
rapid manufacturing can be done
automatically, we envision a future
where any surgeon in the world can
simply send the MRI scan of their
specific cranial implant require-
ments to a single computer that
creates the CAD design, prepares
an FEA validation report, then
sends the data to an additive
manufacturing machine where
the cranioplasty is quickly built
and then returned to the doctor.
From a technical point of view,
everything is there.”
Besides the defined process chain,
Lenz sees additional benefits in the
material itself: “PEEK is mechanically
flexible and translucent to CT, x-ray
“With precise customization and better fit, such implants would require less time in surgery and
provide greater comfort to the patient. Besides labour and material savings, implants can improve
health gain.”
Jörg Lenz, Collaborative Projects Coordinator at EOS GmbH
“We’ve been working with additive manufacturing in metal spine, hip and other implant geometries
for a few years now. So I was already fully convinced of the value of laser-sintering for producing
cranioplasties from the start.”
Dr. Siavash Mahdavi, Stakeholder and Managing Director at Within Technologies
and MRI scans and its chemical
stability and the high melting point
accommodate all methods of ste-
rilization,” he says. Biocompatibility
testing proved the implant to be
non-cytotoxic, non-haemolytic,
non-pyrogenic, non-irritant and
causing no sensitization response.
The socioeconomic benefits of
future laser-sintered PEEK implants
could be considerable, Lenz
believes. “With precise customi-
zation and better fit, such implants
would require less time in surgery
and provide greater comfort to the
patient,” he notes. “There are labour
and material savings as well as
potential improved health gain.”
Mahdavi adds: “We’ve been working
with additive manufacturing in
metal spine, hip and other implant
geometries for a few years now.
This Custom-IMD cranial implant
research was our first PEEK design,
but I was already fully convinced
of the value of laser-sintering for
producing patient-specific implants
with optimized characteristics
designed right in.”
* Hydroxylapatite is a calcium-phosphate complex that is the primary mineral component of natural bones and teeth and gives them their rigidity.
Customer reference
Status 01/2012. Technical data subject to change without notice. EOS®, EOSINT® and e-Manufacturing™
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