Metal hip implants need monitoring annually: MHRA issues guidelines

By Dr. Ananya Mandal, MDMar 1 2012

According to British health regulators people who have a type of all-metal hip replacement should be checked every year for life.

The UK Medicines and Healthcare products Regulatory Agency advised that patients with certain artificial hips need annual tests to check for metal ions and MRIs if they show symptoms. The new guidelines follow reports from doctors of swelling and tissue damage in some patients with metal-on-metal hip implants. The update applies to those in Britain with a hip replacement with a head diameter of 36 millimetres or more. The MHRA said on Tuesday that around 49,000 UK patients with large-head hip implants out of 65,000 with all-metal hips were in a high-risk category.

Before this the MHRA maintained that patients with this type of hip replacement needed to be monitored for a minimum of five years after their operation. The metal implants were developed to be more durable than traditional metal or ceramic in plastic versions. The metal-on-metal implants can last 15 to 20 years.

In most cases, hip implants transform the lives of patients with severe pain and worsening lack of mobility, said Dr. Susanne Ludgate, the group's clinical director. “By monitoring patients every year, any complications will get picked up earlier and more complex surgery on the patient can be avoided”, Ludgate said.

The British advisory does not affect patients in the United States. But the type of all-metal hip covered by it, which used larger ball components than traditional implants, was widely used in the United States for years. While precise figures are not known, it is estimated that many, if not most, of the half a million patients in the United States who received an all-metal hip over the last decade got such devices. In recent years, data from orthopedic registries in Australia and England has shown that all-metal hips are failing prematurely at two to three times the rate of those made from metal and plastic.

Thousands of patients in the United States who received the implants have also been forced to undergo second surgeries to have them replaced within a few years of getting the devices. Hundreds of patients have also suffered crippling injuries because the metallic debris can destroy tissue and muscle surrounding the hip. The debris can come from several sources, including one that appears common to all-metal devices regardless of the model.

Studies have indicated, for example, that the use of the larger ball component increases the amount of torque and motion at the point where that ball and cup are joined, generating debris. In addition, some specific designs produce more debris because of the way the joint’s ball strikes against the implant’s cup.

In a statement, an official with the American Academy of Orthopaedic Surgeons said the organization agreed with “the clinical assessment” made by British regulators. Asked about the British action, a spokeswoman for the Food and Drug Administration, Erica Jefferson, said the agency was maintaining its existing recommendations. Ms. Jefferson said it was not clear if one way to assess tissue damage, testing patient blood for the presence of metallic ions, accurately reflected damage. “We continue to recommend that hip replacement patients undergo regular follow-up with their physicians,” she said.

Tony Nargol, a consultant surgeon at the University Hospital of North Tees told Newsnight/BMJ, “we are seeing patients with 10, 20, 50 times normal levels. I think our highest level is nearly 300”. One all-metal hip device, manufactured by DePuy, a subsidiary of global health giant Johnson & Johnson, called the ASR was recalled in 2010. And the company, which is facing legal action from ASR patients, has set aside $3bn in case they have to pay compensation. But Mr Nargol's research suggests there are also problems with another all-metal hip, made by DePuy, called the Pinnacle, which is still on sale. His hospital tested the nearly 1,000 patients who had been fitted with the all-metal Pinnacle there.

“The trust has brought back all the patients with Pinnacle cups - nearly 1,000 - tested them all, screened them, scanned them, and we know exactly what's happening,” he said. “And we found out that of about 970 patients, 75 failures related to metal debris, which is really quite high.”

Carl Heneghan, Director of the Centre for Evidence-Based Medicine in Oxford, says that the fundamental problem is that artificial hips, breast implants, and other devices which are implanted in patients do not have to face the same rigorous tests new drugs do. He says that whereas drugs have to go through years of clinical trials “you could get a device through with a two or three day literature review and no clinical data requirement at the current time”.