Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Biodegradable, osteo-inductive and tailor-made: a new generation of implants is on the advance

20.05.2010
Research scientists at the Fraunhofer Institute for Laser Technology ILT have developed a laser shaping technique for the manufacture of biodegradable implants under the RESOBONE project funded by the German Federal Ministry of Education and Research (BMBF). The additive manufacturing method makes it possible to adapt the implant to the specific damage to the patient’s bone structure. The interconnective pore system enhances ingrowth of blood vessels and connective tissue cells in the implant and thus also ensures good biodegradability.

The regenerative ability of bones is limited. If they are too badly damaged, e.g. by a tumor or an accident, they have to be replaced by implants. At present surgeons mainly use permanent titanium implants. To improve their ingrowth behavior and compatibility, research scientists at the Fraunhofer ILT have developed a method for the manufacture of porous titanium-alloy implants.

The implants are made by selective laser melting (SLM), an additive laser manufacturing process which was developed back in the early 1990s by the research scientists in Aachen and which has been tailored more specifically to the needs of the medical sector. At the St. Johannes Hospital in Duisburg, Germany, the first hip prosthesis made using SLM was successfully implanted in a patient in 2008. Because of an extreme deformation of the hip, the 35-year-old woman needed a customized implant, which it was possible to produce thanks to the innovative technique. The project partner is now producing 30-40 implants annually using the SLM process.

Often it is not necessary and can even be detrimental for implants to retain their original shape in the patient’s body. Particularly in pediatric surgery, permanent implants are a problem because they soon become too small in relation to the child’s growing skeleton and have to be removed or replaced in a further operation. A need therefore exists in medicine for biodegradable implants with osteo-inductive properties: implants that degrade at the same rate as bone growth which at the same time they specifically stimulate. After a time they should be completely replaced by native bone tissue and thus accelerate the healing process. What’s more, the implant should be individually adapted to the damaged bone structure and exhibit best-possible compatibility in the body. A great advantage of using degradable implants is that in the case of disease-associated bone damage the patient only has to undergo one surgery.

Ultra-fine channels enhance degradability

The research scientists at the Fraunhofer ILT took up this challenge in cooperation with Aachen University Hospital and RWTH Aachen University’s Institute of Mineral Engineering and Department of Dental Materials and Biomaterials Research. In the RESOBONE project they developed a process for the manufacture of biodegradable implants on the basis of their experience with permanent implants produced by means of the SLM method. This production process makes it possible to individually adapt the macrostructure of biodegradable implants to the patient’s specific bone damage prior to surgery. The precisely defined microstructure of the implant ultimately determines its porosity, which is crucial for the implant to be resorbed by the body over time. For this to happen the implant needs to have channels running through it so that blood and cells can completely penetrate. “Creating this sponge-like lattice structure was the biggest challenge of process development,” says Simon Höges, project manager at the Fraunhofer ILT. “Previous types of implant could only be penetrated by native cells to a limited extent. The new technique enables us to generate porous channels with a diameter of 500 to 1000 µm to an accuracy of 100 µm. The material used to manufacture the implants is also of decisive importance in this respect.” β-tricalciumphosphate (β-TCP) is a suitable material for making biodegradable implants because as a natural constituent of human bone it encourages optimal ingrowth behavior in the body. Owing to its chemical structure, however, β-TCP cannot be directly processed by melting. It is therefore only limitedly suitable for processing by means of the SLM method. “We therefore had to find an additive that can be mixed with the pulverized β-TCP to combine its advantages with better meltability. We ultimately found this material in polylactide (PLA), a degradable polymer,” explains Höges. PLA melts at a temperature below 200 °C and is excellent for use in SLM processing. This composite material made it possible to finally produce the biodegradable implant. It is based on β-TCP, but the PLA additive makes the material easier to shape.

Layer by layer to a personal implant

The first step in the manufacture of the degradable implant involves making a CT scan image of the existing bone structure. The contours of the implant are then defined using a virtual technique on the basis of the recorded image data. A software model is then used to integrate the desired pore structure in the virtual implant. The result is a precise template for the microstructure and macrostructure of the implant to be produced. The actual production process can now begin: A laser beam melts a thin layer of the powdered material by local application of heat, following the structural outlines and contours of the virtual model. Then a further layer of powder is added and fused to the first layer with micrometer accuracy. By repeating this procedure, the tailor-made implant is built up layer by layer from the powder material. None of the material is wasted, because any excess powder is recycled and reused. The result is a biodegradable implant with a porous structure produced in a single integrated process.

On the basis of the knowledge and experience gained in this project, SLM is now available as a reproducible shaping process with considerable potential as a means of manufacturing tailor-made biodegradable implants with a defined pore structure. The process is suitable both for the one-off production of personalized implants and for use in low-volume batch production. The range of applications is wide: SLM can be used to make non-load-bearing bone implants as well as biomedical products such as biodegradable stents, which after performing their task are completely resorbed by the body. The technique can also be used in oral surgery, to reconstruct defects in the jaw bone. In cooperation with the partners from the Department of Dental Materials and Biomaterials Research, Höges and his team are currently testing further materials for the production of implants in order to optimize their ingrowth behavior.

Simon Höges will be presenting the conclusive results from the RESOBONE project at a seminar to be held in Aachen University Hospital on July 14, 2010. Lectures on the subject by project partners are also planned. Further information about this event is available at www.ilt.fraunhofer.de in the Events / Trade Fairs section.


Contacts at the Fraunhofer ILT
If you have any questions our experts will be pleased to assist:
Simon Höges
Rapid Manufacturing
Phone +49 241 8906-360
simon.hoeges@ilt.fraunhofer.de
Dr. Wilhelm Meiners
Rapid Manufacturing
Phone +49 241 8906-301
wilhelm.meiners@ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology ILT
Steinbachstrasse 15
52074 Aachen
Phone +49 241 8906-0
Fax +49 241 8906-121

Axel Bauer | idw
Further information:
http://www.ilt.fraunhofer.de;

More articles from Process Engineering:

nachricht Dresdner scientists print tomorrow’s world
08.02.2017 | Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS

nachricht New technology for mass-production of complex molded composite components
23.01.2017 | Evonik Industries AG

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Microhotplates for a smart gas sensor

22.02.2017 | Power and Electrical Engineering

Scientists unlock ability to generate new sensory hair cells

22.02.2017 | Life Sciences

Prediction: More gas-giants will be found orbiting Sun-like stars

22.02.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>