Self-reinforced poly(ether ether ketone) and polyethylene composite gaskets for prevention of mechanically-assisted corrosion in modular taper junctions: Seating, micromotion and short-term fretting corrosion

Abstract

Mechanically-assisted crevice corrosion (MACC) is a phenomenon known to cause complications in modular orthopedic implants, particularly at metal-metal taper junctions. Previous studies of the properties and corrosion performance of an interfacial polymeric self-reinforced composite (SRC) gaskets have shown its capability as a high-strength, insulating barrier against oxide abrasion and metal degradation of metal-metal (or metal-hard) contacts in MACC conditions. This study characterizes the short-term tribocorrosion performance of poly (ether ether ketone) SRCs (SRC-PEEK) and polyethylene SRC (SRC-PE) films under in vitro test conditions for head-neck modular junction designs in hip replacement devices. SRC films composed of SRC-PEEK and SRC-PE were seated between 9/10 femoral head bores and stem tapers as thin interfacial gaskets and tested against metal-metal controls under short-term cyclic loading conditions in a custom in vitro test setup. Head-neck seating mechanics were measured, followed by incremental cyclic fretting corrosion testing with monitoring of fretting current, force, and relative micromotion between head and neck components during cyclic loading. SRC-PEEK tapers had a seating subsidence that was approximately three times that of the SRC-PE tapers and nine times that of controls. SRC-PE tapers, likely due to low friction, partially failed to lock during seating resulting in a pushing up of the head on the taper. Average fretting currents were significantly lower for both SRC groups (less than 0.3 μA at 4000 N) compared to control tapers experiencing fretting corrosion currents between 1.7 μA and 32 μA, (p < 0.05). SRC-PEEK gaskets exhibited similar subsidence and micromotion performance as controls while SRC-PE tapers experienced over 240 μm of subsidence during seating and loading conditions. The SRC-PE low-friction properties likely caused insufficient taper locking, which may increase the risk of improper head seating or head disassociation. These results show that SRC-PEEK gaskets, unlike SRC-PE gaskets, can maintain adequate frictional locking at the taper junction and prevent the onset of MACC. SRC-PEEK gaskets improve the performance of modular taper junctions and could be considered as a potential solution to mitigate fretting corrosion.