By his early 60s, Michael Stieler had worn out the cartilage in his right hip with a lifetime of running, hang gliding and carpentry work. Surgery to replace the hip in 2007 provided enormous relief for the Sonora man – for a year.

"And then all heck broke loose," said Stieler, now 68. "It hurt. I couldn't even walk on it."

He and his wife, Darlene, weren't surprised when a notice arrived last September from the company that manufactured his artificial hip, DePuy Orthopaedics: His all-metal hip was being voluntarily recalled because of its early failure rates as well as its potential for shedding high levels of cobalt and chromium into the bloodstream.

Now the U.S. Food and Drug Administration has ordered all 21 companies that produce so-called "metal on metal" hips to monitor recipients, assessing how they react to the implant. And thousands of artificial hip recipients are wondering if they're at risk from their new hips.

"We've seen some of these implants fail very early and exhibit metal ion release," said Dr. Thomas Blumenfeld, an orthopedic surgeon at Sutter Orthopaedic Institute in Sacramento. "But the vast majority of implants will do well."

Hip replacement surgery, first performed in the 1960s, has revolutionized old age – and now middle age – for millions of Americans who otherwise would be crippled with arthritis and broken hips. More than 250,000 hip replacements are performed in the United States annually, according to the American Academy of Orthopaedic Surgeons.

As many as 30 percent of them involve "metal on metal" bearing surfaces, in which both the ball and socket lining are made of a cobalt chromium alloy. (A variety of other materials, such as ceramics and plastics, can be used in the construction of the hips' bearing surfaces, where the ball of the femur rubs against the socket.)

With "metal on metal" bearings, the ordinary wear and tear of movement can cause microscopic amounts of the alloy to enter the bloodstream, and tiny particles of metallic debris can damage the tissue surrounding the hip, making the implant loosen and become painful.

The new FDA action results from consumer complaints that the metal bearings, which should last up to 15 years, are at particular risk of early failure – and worse, concerns that long-term exposure to the devices' toxic metals can lead to renal problems and cancer.

"The issues around this are fairly complex," said AAOS spokesman Dr. Joshua Jacobs, orthopedic surgery department chairman at Chicago's Rush University Medical Center. "The symptom that patients become aware of is pain. They should not ignore hip pain. It could be caused by bursitis or referred pain from the spine. Or it could be an adverse local tissue response."

And when metals leach into the tissues, the resulting bone loss and tissue damage can make revision surgery a rougher proposition.

Like many artificial hip recipients, Carmichael resident Noreen Rademacher doesn't have any idea what her hips – both replaced in the late 1990s – are made of, or who manufactured them. It's likely she doesn't really need to, because she has had no pain.

"I've been very fortunate," said Rademacher, an energetic 85-year-old widow and retired kindergarten teacher who regularly attends exercise classes at Mission Oaks Community Center. "I know that hip replacements don't last forever, but I'm hoping I don't have to go through surgery again."

Medical experts and FDA officials say that in the absence of complications, most hip implant patients – including people who have received "metal on metal" devices – should not be concerned about their artificial hips. The FDA review of the "metal on metal" hips will include assessment of how the devices are performing as well as recipients' blood tests and imaging.

"The paradigm for joint replacement has been, come back if you're in pain," said Blumenfeld. "But this is a man-made device going into the human body. It has to be followed."

Sacramento County Adult and Aging Commission chairman Pam Flohr – who's had both hips replaced – thinks not rechecking hip implants regularly places too great a responsibility on elderly patients. "It puts too much burden on older patients in particular to decide for themselves," said Flohr, 66. "The general older person is not a medical expert."

Michael Stieler didn't have to be an expert to know something was wrong. His new hip made a clicking noise when he walked, and it began to hurt so much that he had to use crutches. Eventually, he was in so much pain that he couldn't even turn over in bed, said his wife.

Then came the recall letter and the realization that he would have to undergo another surgery to replace the defective part. Blood tests also showed abnormally high levels of cobalt and chromium in his system.

"I thought it was pretty crappy, but I had to do the surgery anyway, because the hip hurt so bad," said Stieler.

Now, a little more than three months after the revision surgery, he's just beginning to walk again without crutches. He can also pedal on his stationary bike for short periods. "I'm a very active person, and this is hard for me," he said. "I worked for Habitat for Humanity before, and now I can't. The doctor told me not to lift more than 20 pounds. My Skil saw weighs more than that."

He's still adapting to his new hip – and his new life.

"He'll have limits," said Darlene Stieler. "But we're hopeful he won't have pain."

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