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

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 mu m 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.

Automated summary

Soft gasket-like polymer films can inhibit fretting corrosion in total joint implants. Self-reinforced composites made from SRC-PEEK or SRC-PE show promise in limiting or preventing mechanically assisted corrosion. The use of SRC gaskets reduces fretting corrosion currents, with SRC-PEEK performing better than SRC-PE, and there is minimal wear damage.