Study Links Metal-on-Metal Hip Replacements and Pseudotumors

A new study indicates that individuals who received metal-on-metal hip replacements may be at an increased risk of suffering severe inflammations that resemble tumors, adding to the existing concerns for individuals who received one of the implants in recent years. 

In a report published this month in the Journal of Bone & Joint Surgery, researchers found that larger diameter metal hip replacement heads are linked to the development of inflamed areas known as pseudotumours.

The study comes just weeks before an FDA advisory committee is set to meet and discuss the mounting safety issues surrounding metal-on-metal hip replacement systems, which are known to release microscopic shavings of metal into the body as the metal parts rub against each other. The FDA panel is expected to review the failure rates with metal-on-metal hips, determine whether testing should be recommended for metal ion blood poisoning and evaluate the risk of potentially systemic complications that may be associated with the implants.

In this latest study, researchers from the Netherlands looked at data on 119 patients who received metal-on-metal total hip replacement systems with large diameter femoral heads between January 2005 and November 2007. They found that 42 patients developed pseudotumours, also known as peri-articular soft-tissue masses. Revision surgery to a polyethylene small-diameter head was necessary for 13 of the patients.

The data also revealed that patients who had high levels of metal ions in their blood, a sign of metal blood poisoning known as metallosis, were four times as likely to develop these pseudotumours.

Metallosis, which occurs when high levels of cobalt and chromium from the metal hip components are released into the body, has been linked to a number of health concerns, including soft tissue damage, nerve damage and a risk of the implant loosening within a few years after surgery.

According to a study published last month in the Journal of Arthroplasty, researchers confirmed that metal-on-metal hip replacements corrode faster than other types of artificial hip implants and indicated that the corrosion may be linked to an increased risk of local tissue reactions that require revision or removal of the implant.

Concerns over problems with metal-on-metal hip replacements have increased in recent years, after national registries in the U.K. and Australia identified higher-than-expected failure rates with several of the implants.

Since these newer metal hip designs were introduced over the past 10 years, they quickly grew to account for a large share of the market for artificial hips, resulting in hundreds of thousands of people who currently have a metal-on-metal hip in their body and could face a risk of future complications.

In August 2010, a DePuy ASR metal-on-metal hip recall was issued after the manufacturer acknowledged that about one out of eight implants were failing within five years.  By the time the recall had been issued, more than 93,000 of the ASR components were implanted worldwide before the recall, with about 40,000 sold in the United States.

A growing number of metal-on-metal hip replacement lawsuits have been filed by individuals who have experienced complications. More than 6,000 individuals have filed a DePuy ASR hip lawsuit after receiving one of the recalled implants, but hundreds of complaints have also been filed over other products, including the DePuy Pinnacle hip, Wright Conserve hip and Biomet M2A-Magnum hip.