Report Slams Response to Metal Hip Troubles

By John Gever, Senior Editor, MedPage Today

Published: February 28, 2012


Regulators on both sides of the Atlantic were slow to inform patients and their doctors about problems with metal-on-metal hip implants and relied on industry officials and consultants in crafting their responses, the BMJ charged.

According to a report appearing online in BMJ, regulators in the U.K., the U.S., and elsewhere should have prevented "a whole class of failing hip implant [sic] from being used in hundreds of thousands of people globally."

The report is based on an investigation commissioned by the journal and the BBC's Newsnight program.

BMJ investigations editor Deborah Cohen reported that the U.K.'s Medicines and Healthcare Products Regulatory Agency (MHRA) first became aware of problems with metal-on-metal implants in 2006, but it was not until 2010 that the agency issued a formal warning to physicians and the public. Complications included high failure rates and possible systemic effects from elevated metal ion levels in the blood.
 

In the U.S., the FDA took no steps to inform the public about such concerns until February 2011.

The BMJ-BBC investigation also found that regulators asked few questions when manufacturers began redesigning their metal-on-metal hip implant models, clearing them for sale without demanding new safety and efficacy studies.

"And so a whole new class of implant -- with the potential to release high concentrations of toxic ions -- was launched onto the U.S. and European markets without the need to conduct clinical trials and without any long term post-marketing studies," Cohen wrote.

Her report also noted that, when the MHRA assembled an ad hoc advisory committee on metal-on-metal implants in 2006, three of its eight members had relationships with industry.

One was director of product development for Smith & Nephew, and two were consultants for Johnson & Johnson's DePuy unit, both of which are prominent makers of metal-on-metal implants.

Many of the report's charges were echoed in a companion BMJ editorial by Carl Heneghan, DPhil, of the University of Oxford in Oxford, England, and colleagues.

They suggested, for example, that device regulations in general are slanted toward industry.

"Guidelines from the EU for manufacturers state: 'The depth and extent of clinical evaluations should be flexible and not unduly burdensome.' This seems curious given the potential risks associated with some medical devices," Heneghan and colleagues wrote.

They also criticized the current registry-based data collection system on hip implants, in which revision surgery is usually the first adverse outcome to be recorded.

"Thus the patient has to develop symptoms and present them to an orthopaedic surgeon, who has to investigate these symptoms and then consider revision," the researchers indicated.

"Only when that joint is removed will the information reach the registry offices. There is a further considerable time lag before data are analyzed and finally presented. In fact, in some cases there is confusion about how 'revision surgery' is defined."

Heneghan and colleagues recommended that the 510(k) system in the U.S. and its European equivalent be reformed, with "an independent system for post-marketing analysis for implantable medical devices."

Neither Cohen nor the editorialists mentioned that orthopedic surgeons began turning away from metal-on-metal implants years ago, spurred by journal publications and meeting presentations that highlighted problems with the devices.

It's estimated that metal-on-metal products now account for no more than 5% of the hip-implant market, down from about 30% a decade ago.

Earlier this month, at the American Academy of Orthopaedic Surgeons' annual meeting, discussions on metal-on-metal implants focused primarily on what to do about patients who already have them, rather on whether the devices should continue to be used.

There was little consensus on whether revision should be considered in the absence of clear symptoms of device failure. For example, in one presentation, David Langton, MRCS, of University Hospital of North Tees in Stockton, England, one of Heneghan's co-authors on the BMJ editorial, suggested that high serum levels of metal ions were a reliable indicator of impending failure.

But William L. Griffin, MD, of OrthoCarolina Hip and Knee Center in Charlotte, N.C., presented data on 90 patients who still underwent revision surgery despite having low ion levels. He said there was no cutoff for ion levels that produced useful positive or negative predictive values.

Moreover, analysis of Kaiser Permanente's large patient database indicated that failure of metal-on-metal implants was still the exception rather than the rule. About 98% of metal-on-metal implants in Kaiser members were still in place after five years, virtually identical to the rate seen with metal-on-highly crosslinked polyethylene.