A metallic biomaterial tribocorrosion model linking fretting mechanics, currents, and potentials: Model development and experimental comparison

J Biomedical Materials Res

2021

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Fretting corrosion in modular orthopedic implants is a well‐documented process that may be associated with adverse local tissue reactions, pain, and revisions. Engineering modular junction interfaces to withstand applied fretting motion without surface abrasion could prevent implant degradation and surface damage. Previous work on geometrically modified Ti‐6Al‐4V/CoCrMo interfaces with increased compliance showed reduced fretting currents and surface damage during short term, variable‐load in vitro testing. This study assesses the same interfaces under long‐term conditions using an in vitro pin‐on‐disk fretting corrosion test apparatus. Preliminary variable‐load frequency testing of typical control pin geometries showed a frequency‐dependent current response, with underlying contact conditions of metal–metal interfaces that remained unchanged. One‐million‐cycle testing showed diminished fretting currents in all groups by 5 × 105 cycles, but consistently lower currents in the high‐compliance group. Corresponding fretting currents and work of fretting measurements of high‐compliance pins confirmed that minimal fretting was experienced at the interface, with elastic bending of the pin accounting for almost all applied displacement. Debris generated during testing were composed of titanium and chromium oxides, small amounts of cobalt and molybdenum oxides, and sodium and phosphate originating from the surrounding test solution. Post‐test analyses of sample surfaces revealed substantially more surface damage on CoCrMo disks than Ti‐6Al‐4V pins, thought to be a result of adhesive wear of mixed oxide debris on the pin and abrasion of the disk by the oxide debris layer. Surface damage to high‐compliance pins suggests some abrasion is unavoidable with geometric modifications.

Section: Discussionsupporting

confidence: 92%

Section: Post-test Analysismentioning

confidence: 99%

Interfacial compliance, energy dissipation, frequency effects, and long‐term fretting corrosion performance of Ti‐6Al‐4V/CoCrMo interfaces

Smith

J Biomedical Materials Res

2021

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“…Six data points (taken 1111 s apart) of current during one 50,000 cycle segment, 5 points during loading/unloading, and 10 min after the system returned to rest at −2 kN (Figure 2) were recorded. The frequency of 9 Hz was chosen based on prior literature that shows that fretting currents are approximately linearly proportional to the loading frequency up to 9 Hz but beyond this frequency fretting currents plateau as there is insufficient time for complete repassivation to take place before the next oxide disruption event 7,16 …”

Section: Methodsmentioning

confidence: 99%

“…This may result in loosening, loss of mechanical integrity, and patient health issues 13,15 . The oxide film repassivates within milliseconds and is detected as fretting currents 16 …”

Section: Introductionmentioning

confidence: 99%

“…13,15 The oxide film repassivates within milliseconds and is detected as fretting currents. 16 The goal of this work was to use an implant performance test that focused on mechanically assisted crevice corrosion (MACC) within acetabular modular tapers that is a simplified, yet representative model to test the response of two different commercial designs fretting corrosion mechanisms including fretting current measurements, posttest ion analysis, and microscopy.…”

Section: Introductionmentioning

confidence: 99%

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

Mace

Goodwin

Journal Orthopaedic Research

2023

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Acetabular components (DePuy Pinnacle (A) and Stryker Trident (B), Ti-6Al-4V shells and 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 0.55μA (B) and 0.05μA (A) and 0.17μA (B), respectively (p = 0.19). No variation in ion averages between A and B (0.23 and 0.45 ppm for Ti [p = 0.21], 0.63 and 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 three million 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.

Low cycle fretting and fretting corrosion properties of low carbon CoCrMo and additively manufactured CoCrMoW alloys for dental and orthopedic applications

Mace

2023

J Biomed Mater Res

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Additive manufacturing (AM) of CoCrMo metallic implants is growing in the orthopedic and dental fields. This is due to the traditional alloy's excellent corrosion resistance and mechanical properties. AM processes like selective laser melting (SLM) require less time, materials, and waste than casting or subtractive manufacturing complex‐geometry structures (bridges, partial dentures, etc.). The objective of this work was to investigate the low cycle tribological and tribocorrosion characteristics of AM CoCrMoW alloys compared to wrought LC CoCrMo (ASTM F‐1537) to assess this AM alloy's performance. Fretting and tribocorrosion testing was performed in air (wear only), PBS (wear + corrosion), and PBS with 10 mM H2O2 (wear + corrosion + inflammation) by a single diamond asperity. No variation between alloys in volume of material removed (p = .12), volume of plastic deformation (p = .13), and scratch depth (p = .84) showed that AM was substantially similar in wear resistance to LC in air and PBS. AM exhibited significantly higher fretting currents (p < .01) at loads up to 100 mN (IAMPBS = 57 nA and IAMH2O2 = 49 nA) than LC CoCrMo (ILCPBS = 30 nA) and (ILCH2O2 = 29 nA). In PBS, wear track depth linearly correlates to fretting current, averaged over 100 cycles. Additionally, fretting currents of both alloys were significantly lower in simulated inflammatory conditions compared to PBS alone. AM alloy has generally similar wear and tribocorrosion resistance to wrought LC CoCrMo and would be ideal for patient specific dentistry or orthopedics where precise, complex geometries are required.