Atomic Scale Origin of Metal Ion Release from Hip Implant Taper Junctions.

Shanoob Balachandran,Alfons Fischer,David Mayweg,Dierk Raabe,Michael Herbig,Markus A Wimmer,Zita Zachariah

doi:10.1002/advs.201903008

Abstract

Millions worldwide suffer from arthritis of the hips, and total hip replacement is a clinically successful treatment for end‐stage arthritis patients. Typical hip implants incorporate a cobalt alloy (Co–Cr–Mo) femoral head fixed on a titanium alloy (Ti‐6Al‐4V) femoral stem via a Morse taper junction. However, fretting and corrosion at this junction can cause release of wear particles and metal ions from the metallic implant, leading to local and systemic toxicity in patients. This study is a multiscale structural‐chemical investigation, ranging from the micrometer down to the atomic scale, of the underlying mechanisms leading to metal ion release from such taper junctions. Correlative transmission electron microscopy and atom probe tomography reveals microstructural and compositional alterations in the subsurface of the titanium alloy subjected to in vitro gross‐slip fretting against the cobalt alloy. Even though the cobalt alloy is comparatively more wear‐resistant, changes in the titanium alloy promote tribocorrosion and subsequent degradation of the cobalt alloy. These observations regarding the concurrent occurrence of electrochemical and tribological phenomena are vital to further improve the design and performance of taper junctions in similar environments.

Highlights

Millions worldwide suffer from arthritis of the hips, and total hip replacement chronic pain or severely limited mobility, Total Hip Arthroplasty (THA) is widely is a clinically successful treatment for end-stage arthritis patients
For patients with femoral head and titanium alloy (Ti-6Al-4V) femoral stem coupled via a Morse taper junction[14] to utilize the superior wear
Recognizing that changes in the subsurface play a role during fretting, we investigate here the nano-scale structure and near-atomic scale 3D elemental distribution of the subsurfaces of a cobalt-titanium alloy couple that was subjected to in-vitro gross-slip fretting in bovine calf serum with 3 mm H2O2

Summary

Introduction

Millions worldwide suffer from arthritis of the hips, and total hip replacement chronic pain or severely limited mobility, Total Hip Arthroplasty (THA) is widely is a clinically successful treatment for end-stage arthritis patients. Fretting and corrosion at this junction can cause release of wear particles and metal ions from the metallic implant, leading to local and systemic tion improving their quality of life.[3,4,5,6] During THA, the diseased hip is replaced with a ball-and-socket joint designed to mimic the biomechanics of the hip. The “ball” in the affected by 2040.[1] Hip and knee osteoarthritis has been ranked ball-and-socket joint is made of a cobalt alloy (Co–Cr–Mo) as the 11th highest cause of global disability.[2] For patients with femoral head and titanium alloy (Ti-6Al-4V) femoral stem coupled via a Morse taper junction[14] to utilize the superior wear

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