Evonik and Samaplast collaborate to improve performance of polyetheretherketone (PEEK) implants

  • Osteoconductive PEEK biomaterial can be used in injection molding processes
  • Intervertebral fusion cage prototype showcases design diversity

Specialty chemicals company Evonik has collaborated with Swiss high-performance polymer injection molding specialist Samaplast to successfully produce a prototype spinal implant based on osteoconductive polyetheretherketone (PEEK) material through an injection molding process. This achievement integrates the expertise of both parties and verifies the excellent processing performance of the new osteoconductive high-performance polymer VESTAKEEP® Fusion.

Biphasic calcium phosphate accelerates bone healing

To date, injection molding processes have not been able to produce implants containing polymer composites of bioactive components. Because during the injection molding process, a thin polymer film is usually formed on the surface of the implant to wrap the bioactive components and prevent osteoblasts from adhering to the implant. VESTAKEEP® Fusion is different. Thanks to the special configuration of functional biphasic calcium phosphate (BCP) particles and their uniform distribution in VESTAKEEP® i4G, BCP will still exist on the surface of the injection molded part after injection molding, thus promoting bone growth. Integrates fully with the implant.

Marc Knebel, head of the market segment of Evonik Medical Systems, said: “Medical implant manufacturers have been looking for a PEEK material that can fuse with bone cells to accelerate bone healing, such as for bone healing after spinal surgery. Evonik VESTAKEEP ® Fusion is filling this gap in the market and can replace titanium, stainless steel or cobalt-chromium alloy implants.”

Bone conductive PEEK material suitable for injection molding processes

One of the development goals of VESTAKEEP® Fusion was to make it suitable for a variety of production processes. The product is available as semi-finished products such as pellets and profiles, which can be machined, thermoformed, extruded or even injection molded. For the injection molding process, through close cooperation with Samaplast, Evonik has maximized the advantages of VESTAKEEP® Fusion.

Stefan Okle, CEO of Samaplast, said: “We tested VESTAKEEP® Fusion on an injection molding machine in a clean room and found it to be very easy to process. After efficient communication with Evonik, we were able to produce a prototype in ten days.” Previously, Mold development alone takes eight to 10 weeks. Rapid prototyping technology greatly shortens this process.

Intervertebral fusion cage prototype showcases design diversity

Evonik and Samaplast will present the first prototype intervertebral implants, which can be used to fill the intervertebral space that occurs after discs have been removed due to degeneration. “The injection-molded interbody cage contains all the details associated with a spinal implant, such as serrations, threads and holes,” Okle said.

Due to the relatively high design freedom of VESTAKEEP® Fusion injection molding, cages with specific shapes can be produced and customized according to anatomical conditions and different surgical methods (such as PLIF, TLIF and ALIF). These cage models demonstrate the design diversity of locking devices and graft cavities. In addition, the design facilitates the use of guidance tools during surgery and is also suitable for minimally invasive as well as patient-friendly surgeries.

Increase cell proliferation by more than 30%

The launch of VESTAKEEP® Fusion marks the official launch of Evonik’s next-generation PEEK-based implant material product line. VESTAKEEP® Fusion contains a special functional additive, biphasic calcium phosphate, so it has osteoconductive properties, allowing bone cells to adhere to the implant more quickly, and has a positive effect on the fusion of the bone and implant interface (i.e. osseointegration) effects, thus accelerating bone healing and recovery.

In vitro study results demonstrate that VESTAKEEP® Fusion improves cell attachment and cell proliferation by more than 30% compared to pure VESTAKEEP® PEEK. Histological examination during the preclinical phase showed dense concentrations of newly generated osteoblasts at the bone-implant interface. Bone histomorphometry results showed that compared with pure VESTAKEEP® PEEK, the amount of bone deposition increased approximately twice. Pull-out tests showed that implant stability increased more than twofold.

In addition, Evonik’s polymer experts are developing PEEK 3D printing filaments based on VESTAKEEP® Fusion, which will be used in FFF (fused filament fabrication) additive manufacturing technology.

Cell attachment on pure VESTAKEEP® PEEK surfaces

Fusion prototypes produced by injection molding demonstrate design diversity.

About Evonik

Evonik is the world’s leading specialty chemicals company with operations in more than 100 countries. In fiscal year 2020, Evonik’s sales were 12.2 billion euros, and operating profit (adjusted EBITDA) reached 1.91 billion euros. We transcend the boundaries of chemistry to create innovative, profitable and sustainable solutions for our customers. Evonik’s approximately 33,000 employees around the world are working tirelessly to make life better.

Evonik regards the Asia-Pacific region as the main driving force of global economic development and an important source of innovation, and continues to strive to achieve sustained business growth in the region. In fiscal year 2020, Evonik’s sales in the Asia-Pacific region reached 2.84 billion euros, with more than 5,000 employees and more than 50 production bases.