Differences in the fretting corrosion of metal–metal and ceramic–metal modular junctions of total hip replacements

Abstract

The use of modular interlocking components is a central design feature of total joint replacements. In this investigation we hypothesized that clinically available ceramic-metal modular connections used in total hip arthroplasty release more metal through fretting corrosion than traditional metal-metal modular connections. This was investigated using an in vitro comparison of ceramic (zirconia, Z r 0 2 ) and metal (Co-alloy) femoral-head fretting upon Co-alloy stem components. In vitro fretting corrosion testing consisted of potentiodynamic monitoring and analysis of metal release from zirconia and Co-alloy 28 mm femoral heads with similar surface roughnesses (Ra = 0.46 p n ) on identical Co-alloy stems at 2.2 kN for 1 x 10' cycles at 2 Hz. In contrast to our original hypothesis, we found greater metal release (approximately I 1-fold increase in Co and Mold increase in Cr) and potentiodynamic fretting of metal-metal modular junctions when compared to ceramic-metal. Potentiodynamic testing demonstrated that lower initial voltages (-266 < 153 mV), greater maximum voltage changes ( I 16 > 56 mV, p < 0.05, t-test) and voltage variability (3 > 0.5 mV, p < 0.05, t-test) were associated with the open circuit potentials of Co-alloy on Co-alloy junctions when compared to zirconia on Co-alloy junctions. In this study of a single total hip replacement stem and head design, zirconia heads mated with Co-alloy stems produced less fretting than Co-alloy heads mated with Co-alloy stems. Although further studies are necessary with a variety of implant designs and under different experimental conditions, the evidence presented here should, in part, alleviate concerns of increases in fretting corrosion at modular junctions of ceramic-metal coupled components.

Metal release and corrosion effects of modular neck total hip arthroplasty

“…The literature unequivocally demonstrates that design-and material-related parameters influence micro-motion and [8,9,11,13,15]. However, no differences in total titanium release were found for the implant designs tested here.…”

Effect of impact assembly on the fretting corrosion of modular hip tapers

“…Recent work showed this result in comparing metal-on-metal to ceramic-on-metal taper connections in vitro. 20 Our results indicate that assembly load and environment both play a role in the initial stability of modular hip taper connections. While further testing is necessary to determine how these assembly variables affect long-term performance of modular hip tapers, our results suggest that initial conditions may affect the extent of clinical fretting corrosion.…”

What is the Trouble With Trunnions?

“…In metal-on-polyethylene (MoP) hips, increased corrosion has been shown in 36-mm metal femoral heads compared with 28-mm heads [16]. Another contributing factor to tribocorrosion in MoP and MoM THAs is the dissimilar alloy pairings of a cobalt-chrome femoral head taper and a titanium trunnion [26], and ceramic femoral heads have been shown to decrease taper tribocorrosion compared with cobalt-chrome heads (CoCr) [20,25,31].…”