Long-term fretting corrosion performance of modular head-neck junctions with self-reinforced composite gaskets from PEEK and UHMWPE

Abstract

Soft gasket-like polymer films may provide multiple advantages in inhibiting fretting corrosion between metal-hard surfaces in total joint implants. Self-reinforced composites (SRC's) made from either poly(ether ether ketone), SRC-PEEK, or ultra high molecular weight polyethylene, SRC-PE, were fabricated and tested to investigate their ability to limit or prevent mechanically assisted corrosion in modular taper devices. Hot compaction was used to create nominally 100 μm thick unidirectional composite gaskets. These gaskets were placed on the trunnions of modular head-neck tapers and seated with 4000 N. One million cycle potentiostatic fretting corrosion tests (3000 N, R = 0.1, 15 Hz, −0.05 V) were employed to assess the ability of these SRCs to reduce or prevent fretting corrosion damage in the modular taper junction. Fretting currents and head-neck micromotion were evaluated. The results of testing, along with pull-off tests and optical and scanning electron microscopic analysis showed that SRC gaskets reduced or eliminated fretting corrosion currents, with the SRC-PEEK performing better than the SRC-PE. Fretting currents were low for SRC's compared to metal-metal tapers. No wear through of the gaskets was noted and minimal wear damage was seen in the SRC-PEEK gaskets. SRC-PE gaskets demonstrated greater deformation and damage compared to the SRC-PEEK gaskets. Pull-off loads for the SRC-PEEK were higher than SRC-PE and not statistically different than the control metal-metal junctions. There was evidence of fatigue cracks forming at the high stress concentration junctions for the SRC-PEEK at the thread form corners of the trunnion, but no loss of integrity was observed. SRC-PEEK gaskets show promise as a method to eliminate modular taper fretting corrosion.