Evonik Industries AG

The specialty chemicals company Evonik and the Swiss plastics specialist Samaplast are combining their expertise in the development of an osteoconductive PEEK biomaterial for injection molding. As part of the collaboration, both partners are demonstrating and documenting the outstanding processing properties of the new osteoconductive high-performance polymer VESTAKEEP® Fusion using the first prototypes of spinal implants.

BIPHASIC CALCIUM PHOSPHATE ACCELERATES HEALING
Until now, it has been virtually impossible to manufacture implants from polymer compounds with bioactive particles by injection molding, because a thin polymer layer usually forms on the surface that overlays the particles, preventing the implant from growing in. But with VESTAKEEP® Fusion, the functional BCP additives (biphasic calcium phosphate) are also available on the surface of injection-molded components. This is ensured by the specially configured microparticles and their homogeneous distribution.

"Implant manufacturers were missing a PEEK material that fuse with bone cells and thus accelerates healing, for example after spinal surgery," says Marc Knebel, Head of the Medical Systems Market Segment at Evonik. "We are closing this gap in the market with VESTAKEEP® Fusion and offering an alternative to titanium, stainless steel or cobalt-chromium implants right away."

OSTEOCONDUCTIVE PEEK BIOMATERIAL FOR INJECTION MOLDING
VESTAKEEP® Fusion was developed with a goal to process in different manufacturing technologies and is initially offered as granules and semi-finished products. It can be milled, compression molded, extruded-and even injection molded. For the latter, Evonik has optimized the compound in close cooperation with Samaplast AG.

"We tested VESTAKEEP® Fusion on injection molding machines in the clean room and found that it was very easy to process," confirms Samaplast CEO Stefan Okle. "Thanks to the excellent exchange with Evonik, we were able to produce a prototype within ten days." Previously, tool development alone had taken eight to ten weeks. With rapid prototyping, this process can be shortened considerably.

CAGE PROTOTYPE DEMONSTRATES THE DESIGN DIVERSITY
Evonik and Samaplast are demonstrating what is possible with the first prototypes of intervertebral implants, known as cages or spacers, which are used to fill the disc space in the spine following its removal due to disc degeneration. "We have produced a cage that contains all the details, such as serrations, threads, and apertures, that are relevant for spinal implants," explains Okle.

Thanks to the design freedom in injection molding of VESTAKEEP® Fusion, specific cage variants can be produced - tailored to the anatomical conditions and different surgical techniques such as PLIF, TLIF and ALIF. The cage models show the design diversity in the interlocks and in the cavities for ossification. In addition, the design facilitates instrument guidance during surgery and also enables minimally invasive, patient-friendly surgical techniques.

OVER 30 PERCENT HIGHER CELL PROLIFERATION
With VESTAKEEP® Fusion, Evonik is introducing a new product line of next-generation PEEK-based implant materials. The osteoconductive properties of the new PEEK material were achieved by using a special functional additive - biphasic calcium phosphate - and allow bone cells to adhere to implants more quickly, thus positively influencing fusion, so called osteointegration, at the boundary between the bone and the implant. This, in turn, will accelerate bone fusion and convalescence.

In vitro studies document over 30 percent increased cell attachment and cell proliferation. In preclinical tests, histological examination reveals a dense network of newly formed osteoblasts at the bone-implant interface. Bone histomorphometry shows an approximately twofold increase in bone apposition. And pull-out tests demonstrate a more than twofold increase in implant fixation.

Evonik's polymer experts are also developing a 3D-printable VESTAKEEP® Fusion filament that could be processed in additive manufacturing using fused filament fabrication (FFF) technology.

Evonik has developed a new 3D-printable PEEK biomaterial for medical technology. With VESTAKEEP® Care M40 3DF, the specialty chemicals company is launching a polyether ether ketone filament for medical applications with body contact up to 30 days. The high-performance polymer can be processed in common extrusion-based 3D printing technologies such as fused filament fabrication (FFF) or fused deposition modeling (FDM). With the product launch, Evonik is expanding the possibilities for individual treatment of patients using additive manufacturing.     

BIOMATERIALS FOR INDIVIDUAL PATIENT TREATMENT
The new PEEK filament is the latest addition to Evonik’s "Care Grade" line based on the high-performance polymer VESTAKEEP® Care M40. The product impresses with its biocompatibility, excellent temperature and chemical resistance, very good sterilizability, and easy handling. The range of possible applications extends from patient-specific hearing aids to filigree prostheses and orthoses to surgical drilling aids for dentistry or individual surgical instruments.  

With a diameter of 1.75 mm, VESTAKEEP® Care M40 3DF is supplied in natural color on 500-gram spools that can be used directly in standard FFF/FDM 3D printers for PEEK materials. The filament is manufactured under cleanroom conditions and then subjected to strict quality management for medical materials. 

REVOLUTIONIZING MEDICAL TECHNOLOGY
"Following the commercial success of our VESTAKEEP® i4 3DF filament for 3D printing long-term permanent implants, we are now expanding the possibilities of modern medical technology for the individual treatment of patients with this new Care product," says Marc Knebel, head of the Medical Devices & Systems market segment at Evonik. "In order to open up further medical applications for even better quality of life, a broad material landscape is needed. We have our fingers on the pulse with our portfolio of 3D biomaterials and are consistently developing it further. Doing so, this year we plan to launch an innovative PEEK-based filament with osteoconductive properties allowing bone cells to adhere to implants more quickly. Our goal is to revolutionize medical technology by offering innovative material solutions."

For more than 20 years, Evonik has been the world’s leading manufacturer of high-performance polymers and additives used in additive manufacturing. The specialty chemicals company offers the industry’s most extensive portfolio of GMP-grade biomaterials used in the 3D printing of medical device parts designed for temporary and permanent body contact. In addition to VESTAKEEP® i4 3DF and VESTAKEEP® Care M40 3DF, the portfolio includes the RESOMER® line of bioresorbable filaments, powders and granules for implantable medical devices.