Metal Ion Levels Predict Metal-on-Metal Hip Implant Failure, Study Suggests

Metal_Ion_Level_ Predict_Hip_Implant_FailureA study published in The Journal of Bone & Joint Surgery found that levels of metal ions in the blood were associated with failure rates of metal-on-metal hip implants.

Metal-on-metal hip resurfacing and total hip arthroplasty have been under fire in recent years due to evidence that the devices can release metal particles into the body when the surfaces of the implant grind together. Research suggests that this can lead to a number of health problems, such as inflammation, bone damage, metallosis, pseudotumors and other issues. A number of metal hip makers have recalled their devices because too many patients have had to undergo a revision surgery to remove or replace the faulty hip implant.

The study, which was published on July 2nd, aimed to assess whether or not blood metal ion levels could help predict implant failure. Researchers analyzed data from 597 patients who received a unilateral Articular Surface Replacement (ASR) implant at least one year prior. They compared blood metal ion levels between patients with failed implants and non-failed implants. Any implant that was associated with revision, plans to revise or poor patient-reported hip function was considered to be a failure.

Findings revealed significantly higher levels of cobalt and chromium ions in patients with failed arthroplasty compared to those who did not have a failed arthroplasty and blood cobalt ions were disproportionately high in patients with failed arthroplasty compared to those with a failed resurfacing implant. There was no significant difference in blood chromium levels between patients with failed resurfacing implants and failed arthroplasty.

The authors concluded that “Raised levels of blood metal ions were associated with failed metal-on-metal hip resurfacings and total hip arthroplasties.” The study was correlational and does not prove a causal relationship.

Many metal hip implant recipients have filed lawsuits alleging that the devices have caused injuries. These lawsuits have been filed against multiple manufacturers, including Johnson & Johnson, Biomet and Stryker. J&J received the most attention over the devices when it globally recalled its ASR hip implants in 2010 due to a higher failure rate.

In March, a $56 million Biomet metal hip implant settlement was approved by federal judge Robert L. Miller Jr. The settlement is to resolve a multidistrict litigation that involves two devices, the Biomet M2a-38 and M2a-Magnum hip implants that needed to be revised. More than 1,200 lawsuits have been filed into the MDL.

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