Bone conduction PEEK biomaterial can be used in injection molding process

Fusion cage prototype showcases design diversity

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

Biphasic calcium phosphate accelerates bone healing

To date, the injection molding process has not been possible to produce implants containing polymer composites of biologically active ingredients. Because during the injection molding process, a thin polymer film usually forms on the surface of the implant, wrapping the bioactive ingredient and preventing osteoblasts from attaching to the implant. Unlike VESTAKEEP® Fusion, thanks to the special configuration of functional biphasic calcium phosphate (BCP) particles and their uniform distribution in VESTAKEEP® i4G, after injection molding, BCP will still exist on the surface of injection molded parts, thereby promoting bone Fully fused with the implant.

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

Bone conduction PEEK material for injection molding

One of the development goals of VESTAKEEP®Fusion was to make it suitable for a variety of production processes. The product is available in the form of 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 takes the advantages of VESTAKEEP®Fusion to the extreme.

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 produced a prototype within ten days." Previously, Mold development alone takes eight to ten weeks. Rapid prototyping technology greatly shortens this process.

Fusion cage prototype showcases design diversity

Evonik and Samaplast will present the first prototype intervertebral implant, a cage that can be used to fill the intervertebral space created by the removal of a degenerated intervertebral disc. "The fusion cage produced by the injection molding process contains all the details associated with spinal implants, such as serrations, threads and holes," Okle said.

Cell proliferation increased by more than 30%

The launch of VESTAKEEP® Fusion marks the launch of Evonik's next-generation PEEK-based implant material product line. VESTAKEEP® Fusion contains a special functional additive, biphasic calcium phosphate, and thus possesses osteoconductive properties that allow osteocytes to attach to the implant more rapidly, positively contributing to the fusion of the bone and implant interface (i.e. osseointegration) effects, thereby accelerating bone healing and recovery.

In vitro results demonstrated that VESTAKEEP® Fusion exhibited more than 30% greater cell attachment and cell proliferation compared to pure VESTAKEEP® PEEK. Histological findings at the preclinical stage revealed dense new osteoblasts at the bone-implant interface. Bone histomorphometry results showed an approximately twofold increase in bone deposition compared to pure VESTAKEEP® PEEK. The pull-out test showed that the implant stability more than tripled.

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.