Carbon fiber cannot always reduce the wear of PEEK for orthopedic implants under DPPC lubrication

Excellent wear resistance is an important feature of orthopedic implants. However, although pure polyetheretherketone (PEEK) is outperformed by carbon fiber-reinforced PEEK (CF-PEEK) for stability and durability under laboratory conditions, it is not clear whether CF-PEEK should be preferred in all real-world applications. Results indicate that, under dipalmitoylphosphatidylcholine (DPPC) lubrication, the wear rates of PEEK are 35%–80% lower than the wear rates of CF-PEEK for different implant materials, speeds, loadings, and DPPC concentrations. Molecular dynamics calculations confirm that DPPC self-assembles on the PEEK surface to form an easily adsorbed continuous phospholipid lubricating film. In contrast, the carbon fibers on the CF-PEEK surface hinder the formation of the protective DPPC film and the CF-PEEK surface is thus subject to faster wear.