What is it about?

Total hip arthroplasty using modular implants helps millions of patients suffering from advanced stages of arthritis. Metal on metal (MoM) and polymer (MoP) implants based on a titanium alloy stem and cobalt alloy head were widely used for this surgery. Degradation of these metal parts by tribological loading and associated wear-metal ion toxicity might cause local or systemic side effects. This is a major concern, hence alerts were issued on the usage of MoM implants by various agencies. Yet, the degradation mechanisms are poorly understood. We did an in-vitro analysis on this biomedical alloy couple simulating the human gait cycle and body fluid conditions. Near atomic-scale characterization after these tests reveals how a sub-surface modification in titanium alloy leads to metal ion release from cobalt alloys.

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Why is it important?

Combining characterization techniques such as atom probe tomography and transmission electron microscopy, we attempted to resolve the complex mechanisms of fretting wear of biomedical alloys under body fluids.


We found a coupled mechanism in Ti and Co alloy surfaces at a near atomic scale, which potentially gives insights to the metal ion release when mechanically coupled systems like MoM implants fail.

Shanoob Balachandran

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This page is a summary of: Atomic Scale Origin of Metal Ion Release from Hip Implant Taper Junctions, Advanced Science, January 2020, Wiley,
DOI: 10.1002/advs.201903008.
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