POLYMER-BASED TOTAL KNEE ARTHROPLASTY WITH A PEEK (POLY-ETHER-ETHER-KETONE)-UHMWPE ARTICULATION: BIOMECHANICAL AND BIOTRIBOLOGICAL ASPECTS

Total knee arthroplasty (TKA) is a treatment for degenerative joint disease, but complications can arise from polyethylene wear particles and metal ions like chromium, cobalt, and molybdenum. PEEK (poly-ether-ether-ketone) is an alternative to CoCr28Mo6, avoiding metal ion release and improving patient satisfaction due to its similar Young's modulus to bone, reducing stress shielding and bone resorption. Studies have examined PEEK's wear performance against UHMWPE in basic material tests and in standardized wear simulation. To fully analyze PEEK's capabilities as a TKA material, more clinically realistic wear testing is necessary to evaluate the robustness of this innovative articulation. This study compares the wear characteristics of a PEEK femoral component to a CoCr28Mo6 knee implant under a highly demanding activities wear simulation. Method: Four femoral components based on the VEGA System ® PS design (Aesculap AG) were made from PEEK-OPTIMA TM (Invibio Ltd.). For the control group, four femoral components from CoCr28Mo6 were selected. UHMWPE gliding surfaces were used in both groups. Wear simulation was performed on an EndoLab knee simulator capable of reproducing loads and movement of highly demanding activities measured in vivo on 8 patients and normalized to a patient weight of 100 kg. The load profiles were applied for 5 million cycles, including stairs up and down, level walking, chair raising, and deep squatting. The gliding surfaces were evaluated for wear and roughness analysis throughout the test. An optical analysis of the femoral cam was conducted to detect cracks or deformation. The average wear rate for the UHMWPE in the PEEK group was 2.6 ± 0.8 mg/million cycles, compared to 5.6 ± 1.2 mg/million cycles in the CoCr28Mo6 group, aligning with previous studies. The UHMWPE gliding surface roughness was similar in both groups, showing comparable wear patterns. The PEEK femoral components' roughness slightly increased by the end of the test, with minor scratches observed. No cracks or deformations were detected in the PEEK femoral cam. The wear rate of the UHMWPE gliding surfaces against the PEEK femoral components was substantially lower in comparison to the CoCr28Mo6 implant and was in the range of clinically successful implants. The PEEK femoral cam showed no failure, indicating stability during high flexion activities. In conclusion, the PEEK component shows promising wear results and is a potential alternative for future metal-free primary TKA solutions.