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 profileThe 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.

ChallengeManufacturing of a patient-

specific cranioplasty with a

highly-complex structure that

promotes bone ingrowth into

the implant.

SolutionSpeedy 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:Designand

polymer filling promote bone

ingrowth

• Biocompatible:PEEKisnon-

cytotoxic, non-haemolytic, non-

pyrogenic, non-irritant and

causes no sensitization response.

• Economic:reducedproduction

costs due to fewer labour and

material expenses

• Integrated:automateddesign

and manufacturing within a

few hours

Further informationwww.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-

ChallengeTitanium-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

EOS GmbH Electro Optical SystemsRobert-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

SolutionThe 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.

ResultsDr. 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™ are registered trademarks of EOS GmbH. EOS is certified according to ISO 9001.