In vitro corrosion testing of modular hip tapers

Area of Science:

• Biomaterials Science
• Orthopedic Engineering
• Tribocorrosion

Background:

• Modular hip prostheses are susceptible to fretting and corrosion at the taper interface.
• Understanding the interplay between mechanical loading and electrochemical reactions is crucial for implant longevity.

Purpose of the Study:

• To simulate in vivo fretting behavior of modular hip prostheses.
• To evaluate the effects of material combinations and TiN/AlN coating on fretting and corrosion.
• To determine the role of mechanically assisted crevice corrosion.

Main Methods:

• Simulation of in vivo fretting in modular hip taper couples (similar-alloy, mixed-alloy, coated mixed-alloy).
• Measurement of fretting current, open-circuit potential (OCP), and soluble debris.
• Chemical, mechanical, electrochemical analyses, and microscopic inspection of taper surfaces.

Main Results:

• Fretting and corrosion were indicated by decreases in OCP and increases in fretting current.
• Corrosion continued even after cessation of loading, suggesting established crevice corrosion.
• Coated samples demonstrated superior resistance to fretting and corrosion compared to uncoated ones.

Conclusions:

• Fretting and corrosion behavior of similar- and mixed-alloy tapers are comparable.
• TiN/AlN coating significantly improves resistance to fretting and corrosion.
• Mechanical loading is a critical factor in initiating and propagating crevice corrosion in hip prostheses.