Specialty chemicals company Evonik and Samaplast, a Swiss high-performance polymer injection company, have successfully produced a prototype spinal implant based on osteoconductive polyetheretherketone (PEEK) through the injection molding process. This achievement integrates the expertise of both parties and verifies the excellent processing performance of the new bone conduction high-performance polymer VESTAKEEP® Fusion.
Biphasic calcium phosphate accelerates bone healing
So far, the injection molding process has not been able to be used to produce implants of polymer composites containing biologically active ingredients. Because during the injection molding process, a thin polymer film is usually formed on the surface of the implant to wrap the bioactive ingredients and prevent 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, BCP will still exist on the surface of the injection molded part after injection, thereby promoting bone Fully fused with the implant.
Marc Knebel, head of Evonik’s medical system market segment, said: “Medical implant manufacturers have been looking for a PEEK material that can fuse with bone cells to accelerate bone healing, for example, 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 conduction PEEK material suitable for injection molding process
One of the development goals of VESTAKEEP® Fusion is to make it suitable for a variety of production processes. The product is provided in the form of semi-finished products such as pellets and profiles, which can be processed by machining, hot pressing, extrusion and even injection molding. Regarding the injection molding process, through close cooperation with Samaplast, Evonik has maximized the advantages of VESTAKEEP® Fusion.
Samaplast CEO Stefan Okle said: “We tested VESTAKEEP® Fusion on an injection molding machine in a clean room and found that it was very easy to process. After efficient communication with Evonik, we produced a prototype within ten days.” It takes eight to ten weeks for mold development alone. Rapid prototyping technology greatly shortens this process.
Prototype of intervertebral fusion cage shows design diversity
Evonik and Samaplast will show the first batch of prototype intervertebral implants, which can be used to fill the intervertebral space that occurs after the degeneration of the intervertebral disc is removed. Okle said: "The intervertebral fusion cage produced by the injection molding process contains all the details related to the spinal implant, such as serrations, threads and holes."
Because the design freedom of VESTAKEEP® Fusion injection molding is relatively high, it is possible to produce special shaped fusion cages, which can be customized according to anatomical conditions and different surgical methods (such as PLIF, TLIF and ALIF). These cage models show the design diversity of locking devices and bone graft cavities. In addition, this design facilitates the use of guiding tools during surgery, and is also suitable for minimally invasive surgery and patient-friendly surgery.
Cell proliferation increased by more than 30%
The launch of VESTAKEEP® Fusion marks the official launch of Evonik's PEEK-based next-generation implant material product line. VESTAKEEP® Fusion contains a special functional additive biphasic calcium phosphate, so it has bone conduction properties, allowing bone cells to attach to the implant more quickly, and has a positive effect on the fusion (ie osseointegration) between the bone and the implant interface. Affect, thereby accelerating bone healing and recovery.
The results of in vitro studies proved that compared with pure VESTAKEEP® PEEK, the cell attachment and cell proliferation of VESTAKEEP® Fusion exceeded 30%. The results of histological examination during the pre-clinical research stage showed that there were dense newly formed osteoblasts at the bone-implant interface. The results of bone tissue morphometry show that compared with pure VESTAKEEP® PEEK, the amount of bone deposition has increased by about two times. The pull-out test showed that the stability of the implant was more than doubled.
In addition, Evonik’s polymer experts are developing PEEK 3D printing filaments based on VESTAKEEP® Fusion, which will be used in FFF (Fuse Manufacturing) additive manufacturing technology.