Torsion Wear Behavior of PEEK-on-UHMWPE as an All-Polymer Joint Combination in Total Knee Replacement

Abstract

Polyether ether ketone (PEEK) has been considered as an alternative material to cobalt chrome in the femoral component of a total knee replacement. In this article, the experimental simulation of torsion wear for a PEEK and CoCr femoral head against an ultra-high-molecular-weight polyethylene (UHMWPE) tibial pad was carried out using a two-station knee simulator. The testing results showed that T-θ curves of torsion wear for PEEK-on-UHMWPE bearing couples showed three types of morphological characteristics, such as linear, elliptical, and parallelogram shapes. With an increase in torsion angular displacement, T-θ curves changed from the linear to the parallelogram type, and the relative motion state changed from the partial slip regime coordinated by the elastic deformation to the slip regime with plastic deformation. With an increase in normal load, the T-θ curve changed from the parallelogram to the elliptical type, and the relative motion state changed from the slip regime to the mixed slip regime. Under intermediate torsion wear conditions, the wear factors of UHMWPE were 11.25 ± 2.08 × 10−6 mm3/C and 14.65 ± 2.49 × 10−6 mm3/C against PEEK and CoCr. Under high torsion wear conditions, the wear factors were 20.51 ± 3.23 × 10−6 mm3/C and 23.26 ± 3.01 × 10−6 mm3/C, respectively. The wear surface of UHMWPE against PEEK showed slight adhesive wear and plastic deformation in the center, and abrasive wear with local fatigue spalling was found at the edges. The wear topographies presented characteristics similar to the CoCr bearing combination.