Assessing the Influence of PEEK on Tribocorrosion in Metal on Polymer Total Joint Replacement

Tribocorrosion studies have primarily focused on hard-on-hard articulations, with limited research on metal-on-polymer (MoP) configurations despite their clinical relevance. This study investigates the tribocorrosion behaviour of cobalt-chromium (CoCr) alloy against 3D-printed polyetheretherketone (PEEK), conventionally manufactured PEEK, and ultrahigh molecular weight polyethylene (UHMWPE), with UHMWPE as the reference material. Tests were conducted using a reciprocating tribometer under open circuit and potentiostatic conditions in phosphate buffered saline (PBS) and bovine calf serum, with in-situ electrochemical monitoring. The results demonstrated that the presence of serum significantly decreased the charge transfer of the CoCr surface, hence decreasing electrochemical degradation when compared to PBS lubrication. The manufacturing methods for PEEK resulted in different surface characteristics, leading to variations in tribocorrosion behaviour; however, polishing to achieve homogeneous roughness minimized these differences. Furthermore, CoCr exhibited significantly higher charge transfer when slid against all tested PEEKs compared with UHMWPE (at least two-fold higher), suggesting that a PEEK-CoCr tribocouple results in an increase of tribocorrosion and a greater potential for metal ion release than a UHMWPE-CoCr tribocouple.