Metal ion levels: how can they help us?
1Ortho Carolina Hip & Knee Center Charlotte, North Carolina.
The Journal of Arthroplasty
|March 25, 2014
Summary
Elevated metal ion levels in patients with metal-on-metal hip implants may indicate abnormal wear. A threshold of 4.5 ppb for chromium or cobalt ions suggests further investigation with MARS MRI, not immediate revision surgery.
Area of Science:
- Orthopedic Surgery
- Biomaterials Science
- Diagnostic Imaging
Background:
- Metal-on-metal hip articulations can lead to abnormal bearing surface function and increased wear.
- Blood ion levels are indicators of implant wear but require careful interpretation.
- Current guidelines suggest a nuanced approach to revision surgery decisions for these implants.
Purpose of the Study:
- To evaluate the utility of blood ion levels in predicting abnormal wear in metal-on-metal hip implants.
- To establish a threshold for ion levels that warrants further diagnostic investigation.
- To inform risk stratification strategies for patients with metal-on-metal hip implants.
Main Methods:
- Analysis of blood ion levels (chromium and cobalt).
- Correlation of ion levels with implant function and wear.
- Evaluation of Magnetic Resonance Imaging (MARS MRI) as a diagnostic tool.
- Development of risk stratification protocols.
Main Results:
- Blood ion levels reliably predict abnormal bearing surface function and increased wear.
- An ion level threshold of 4.5 parts per billion (ppb) for chromium (Cr) or cobalt (Co) may indicate abnormal wear.
- This threshold is suggested as a trigger for Magnetic Resonance Imaging (MARS MRI) scans.
Conclusions:
- Blood ion levels should not be the sole factor in deciding on revision surgery for metal-on-metal articulations.
- A threshold of 4.5 ppb for Cr or Co ions suggests abnormal wear and warrants further investigation with MARS MRI.
- Risk stratification incorporating ion levels and imaging is crucial for patient management.
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