Company insight
Unique: An osteoconductive PEEK for injection moulding VESTAKEEP Fusion was developed with a view to processing different manufacturing technologies. It can be milled, compression moulded, extruded and even injection moulded. For the latter, Evonik has optimised the compound in close cooperation with Samaplast in St. Margarethen, Switzerland. Until now, it has been virtually impossible to manufacture implants from compound plastics with bioactive particles by injection moulding, because a thin polymer layer usually forms on the surface that overlays the particles and thus prevents the implant from growing in. With VESTAKEEP Fusion, the functional BCP additives are also available on the surface of injection- moulded components. This is ensured by the specially configured microparticles and their homogeneous distribution. For manufacturers of implants,
VESTAKEEP Fusion offers the added value of fully preserving the osteoconductive function during injection moulding. With this unique combination of material and processing properties, osteoconductive plastic implants can now be manufactured in just one production step. There is no need to additionally coat them with titanium or other expensive processes. This saves costs and improves product quality.
Demonstrates the design diversity The ability to process VESTAKEEP Fusion by injection moulding expands the range of applications for osteoconductive implants, particularly in spinal surgery. Until now, spinal implants made of PEEK have mainly been milled. There are a variety of designs and sizes on the market, often produced in small quantities. And this is precisely where there is great potential for injection-moulding osteoconductive PEEK implants with VESTAKEEP Fusion: different modules can be produced with one basic mould. “We tested VESTAKEEP Fusion on injection moulding 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
Left, cells in normal VESTAKEEP biomaterial; right, cells in VESTAKEEP fusion.
ten weeks. With rapid prototyping, this process can be shortened considerably.
Rapid prototyping: Four weeks from the idea to the sterile- packed implant
“The original geometry is available. We can build the mould for injection moulding within ten to twelve days. Customers only have to supply us with the design, then they get the sterile-packaged implant within four weeks,” continues Okle. This results in several advantages for medical device suppliers: they receive an original component that has passed a strict quality management system very quickly from a single source. Unlike implants, which consist of components from several manufacturers, the supply chain here remains short and manageable. Samaplast also offers OEMs design support if required.
Evonik and Samaplast are
demonstrating what is possible with the first prototypes of intervertebral implants, known as cages, which are used to stiffen the spine in cases of 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.
Sometimes it is only during surgery that it is decided which type of implant can be used, depending on the nature of the patient’s bone substance. Thanks to the design freedom in injection moulding of VESTAKEEP Fusion, specific cage variants can be produced – tailored to the anatomical conditions and different surgical techniques, such as PLIF, TLIF and ALIF. “With our cage models, we show the design diversity in the interlocks and
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in the cavities for ossification. In addition, the design facilitates instrument guidance during surgery and also enables minimally invasive, patient-friendly surgical techniques,” explains Okle.
Proven functionality in injection moulding
Under the scanning electron microscope, it can be clearly seen that there is no film formation on the surface during injection moulding of VESTAKEEP Fusion. In addition, images of a VESTAKEEP iC4800 injection-moulded screw show a comparable distribution density of calcium phosphate particles inside the screw and on its surface. This is also confirmed by energy dispersive X-ray spectroscopy (EDX analysis). The comparison of milled and tip-cast components made of VESTAKEEP Fusion shows no statistically significant deviations in cell proliferation and adhesion of osteoblasts. The first product from the VESTAKEEP Fusion line, VESTAKEEP iC4800, is currently available as granules for injection moulding and extrusion, and as solid rods for milling. With VESTAKEEP Fusion Select, Evonik is going to offer its customers the development of exclusive, customised materials with bioactive properties. The next milestone is already emerging in processing technologies: Evonik is currently developing a 3D-printable filament that can be processed in additive manufacturing using fused filament fabrication (FFF) technology. This will make patient- specific implants available even faster in the future. ●
https://medical.evonik.com/en 113
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