This week: FDA Panel Meeting to review Metal-on-Metal Hip Replacements

The ball section of an artificial hip removed during surgery at Massachusetts General Hospital.

Once promoted by industry and doctors as an innovative orthopedic breakthrough, the devices have failed prematurely in thousands of cases, causing many patients to undergo repeat surgeries and producing crippling injuries in some of them. As they wear, the devices shed tiny particles of metallic debris that can damage a patient’s muscle and tissue.

Experts caution that definitive answers are not likely to emerge from the hearing. And they add that neither government, industry nor the medical profession appear eager to address the fundamental issue raised by the episode: Why were these devices implanted in 500,000 people without adequate testing?

“There was not enough data to support” their widespread use, said Dr. Henrik Malchau, an orthopedic surgeon at Massachusetts General Hospital in Boston.

Under F.D.A. rules, orthopedic implant makers did not have to run clinical trials of the hips before marketing them, nor were they required to follow patients afterward to see how they fared. Doctors embraced the implants without evidence they were better or more durable than existing ones.

Many doctors say they adopted the devices believing they would help reduce a complication of hip replacement — the possibility of implant dislocation.

The use of all-metal hips has fallen sharply in recent years. Still, the failure to put safeguards in place before their sale has also complicated efforts to assess dangers, said Dr. Malchau and other experts.

For example, while the F.D.A. took the unusual step in May 2011 of ordering five producers of all-metal hips to undertake studies to examine how patients were faring, the agency has so far approved the study plan of only one manufacturer, Biomet.

The agency rejected initial proposals from four other companies, including the two industry leaders, the DePuy division of Johnson & Johnson and Zimmer. Representatives of those companies and others said they were working with the F.D.A. to resolve its concerns.

However, the simple fact that the agency is now debating study designs with device manufacturers nearly a decade after these products were first sold is deeply troubling, said one expert, Dr. Art Sedrakyan of Cornell-Weill Medical Center in New York.

Also, as it turns out, at least one major manufacturer, DePuy, has clinical data in hand about two all-metal implants that it has yet to release.

In an interview, Dr. Ivan M. Tomek of Dartmouth-Hitchcock Medical Center in Lebanon, N.H., said he was an investigator on a study started in 2006 in which patients received one of two metal hip models made by DePuy — either a model known as the ASR or a model known as the Pinnacle.

Dr. Tomek said the study enrolled about 250 patients nationwide and that patients were followed for about two years. He added, however, that DePuy had never publicly released the study’s data.

DePuy recalled the ASR in 2010 but continues to maintain that the all-metal Pinnacle is safe. The company faces hundreds of patient lawsuits involving both products.

Asked about the trial, a DePuy spokeswoman, Mindy Tinsley, said the company was still analyzing follow-up data from patients enrolled in 2009, the study’s last year.

Generally speaking, nearly all models of all-metal hips have higher failure rates than traditional implants made from a combination of materials like metal and plastic. The rates of early failure vary between different models, with the highest failure rate associated with the DePuy ASR.

Getting a fix on specific failure rates is difficult because this country, unlike Britain and Australia, for example, does not have an orthopedic registry that follows patient outcomes.

For doctors and patients, one of the biggest problems with metal hips is detecting whether the metallic debris generated by an implant is damaging a patient’s tissue or muscle or how to best monitor for such problems. In recent months, device producers have not been providing new information, Dr. Tomek said. “There has not been much coming from the implant companies,” he said.

Also, regulators in Britain have taken a more aggressive approach than their counterparts in the United States in setting guidelines about how the devices should be monitored. F.D.A. officials said that they had questions about the validity of the tests used to make such recommendations.

For example, agency officials said that they had concerns about the accuracy of blood tests to measure the level of metallic ions in a patient’s blood as well as about the reliability ofmagnetic resonance imaging scans used to detect tissue damage. At the F.D.A. meeting, experts will be asked to make recommendations about the use of such tests.

There seems to be little current appetite, said experts like Dr. Malchau of Massachusetts General to address the bigger issues of whether such implants should be required to undergo clinical testing before being sold or only be used initially in small groups of closely monitored patients.

In addition, he and other experts wonder whether most orthopedic surgeons have embraced the lesson of the all-metal fiasco or whether they will simply jump at the next “innovation” offered by industry.

In either case, he said, future patients need to better protect themselves by demanding that their surgeon provide data showing that the implant they are recommending has a long, proven track record.

“If you are buying a new refrigerator or appliance, you go to Consumer Report,” he said. “The data is out there.”