Research Indicates CFR PEEK Polymer May Provide Lower Wear On-Metal In Orthopedic Implants
Rome – Invibio, a provider of biomaterial solutions to the medical device market, presented findings from research investigating wear rates of carbon fiber-reinforced (CFR) PEEK polymer used in conjunction with BIOLOX Forte and BIOLOX Delta ceramic counterfaces.
The research, presented in a poster session at the 11th International BIOLOX Symposium, indicates that orthopedic implants developed with CFR PEEK polymer may produce less wear compared to those implants developed using conventional UHWMPE-on-metal material combinations.
"The wear rates of bearing materials are an increasing concern in the orthopedic implant market, especially as younger patients are becoming candidates for joint replacement surgery," said Dr. John Devine, Senior Product Development Scientist, Invibio. "As a result, there have been many advances in the wear performance of materials selected for total joint replacement, and engineers continue to search for new materials to reduce wear in order to increase implant lifespan and decrease the potential for osteolysis."
Materials and Methods
Four different material combinations were tested on a four-station device that applied both reciprocation and rotational motion. Samples of CFR-PEEK (PAN based fibers) and samples of CFR-PEEK (Pitch based fibers) were tested against BIOLOX Forte and BIOLOX Delta plates, supplied by Ceramtec. A 40N load was applied to each station, which resulted in a contact stress of approximately 2MPa. The lubricant used was 24.5 % bovine serum (protein content: 15 gl-1), which was heated to 37°C. The wear was assessed gravimetrically and each test completed 2 million cycles.
Results
The combination of CFR PEEK materials against ceramic counterfaces produced significantly lower wear factors than those of UHMWPE/metal wear couples (1.1 x 10-6 mm3N-1m-1). The lowest wear factor (0.153 x 10-6 mm3N-1m-1) was found for pitch-based carbon fiber PEEK bearing against BIOLOX Forte. If a stronger PAN-based reinforced material is required, the preferred counterface was BIOLOX Delta (wear factor 0.180 x 10-6 mm3N-1m-1). It was also observed that in general the surface of the machined polymeric pin becomes smoother (Sa ˜ 0.1µm) and more negatively skewed during the test, without a significant breaking in period.
Recently 54mm diameter alumina-on-CFR PEEK prostheses have been investigated in a hip simulator to 10 million cycles. These joints demonstrated a wear rate of 1.08mm3/million cycles, which was significantly lower than the wear rate of ceramic-on-UHMWPE joints at 38.6mm3/million cycles.
A study performed by Howling et. al. assessed the biological response to CFR-PEEK wear particles and compared it to UHMWPE particles1. These experiments demonstrated that CFR-PEEK wear particles had no cytotoxic effects on cells in culture.
SOURCE: Invibio