Fretting corrosion testing of acetabular modular tapers for total hip replacements: A comparison of two designs.

Abstract

Acetabular components (DePuy Pinnacle (A) and Stryker Trident (B), Ti-6Al-4V shellsand CoCrMo liners) with varying geometries were assembled under a 4 kN seating load. Liner-displacement was recorded. Cyclic compression to 4 kN, R = 0.01, 9 Hz was applied for three million cycles to evaluate fretting corrosion currents (n = 5). Fretting currents, load-displacement, ion dissolution, and disassembly loads were used to compare device performance. Data were analyzed using ANOVA with Tukey post hoc comparisons (p < 0.05). Liner seating displacements were not significantly different between groups. Fretting currents averaged over the initial 10 h and over three million cycles were 0.17 μA (A) and 0.55 μA (B) and 0.05 μA (A) and 0.17 μA (B), respectively(p = 0.19). No variation in ion averages between A and B (0.23and 0.45 ppm for Ti [p = 0.21], 0.63and 0.85 ppm for Co [p = 0.47]) existed. Average push-out forces, -2.41(A) and -2.42 kN (B), were not significantly different (p = 0.97). SEM and EDS showed some titanium and metal oxide transfer from the shell to the liner in both designs. Overall, both implant designs exhibited very minor MACC in these experiments. This study demonstrates quantitative measures of in vitro fretting corrosion over the course of threemillion cycles and the minimal degree of acetabular taper damage. Clinical Significance: Retrieval studies show dual mobility acetabular shell-liner tapers with metal-on-metal contacts are susceptible to fretting corrosion in vivo.