In recent years, such devices, known as "metal on metal" implants, have been used in about one-third of the approximately 250,000 hip replacements performed annually in this country. They are used in conventional hip replacements and in a popular alternative procedure known as resurfacing.
The devices, whose ball-and-socket joints are made from metals like cobalt and chromium, became widely used in the belief that they would be more durable than previous types of implants.
The cause and the scope of the problem are not clear. But studies in recent years indicate that in some cases the devices can quickly begin to wear, generating high volumes of metallic debris that is absorbed into a patient's body. That situation can touch off inflammatory reactions that cause pain in the groin, death of tissue in the hip joint and loss of surrounding bone.
Doctors at leading orthopedic centers like Rush University Medical Center in Chicago and the Mayo Clinic in Rochester, Minn., say they have treated a number of patients over the last year with problems related to the metal debris.
Artificial hips, intended to last 15 years or more, need early replacement far more frequently for reasons like dislocation than because of problems caused by metallic debris. But surgeons say that when metal particles are the culprit, the procedures to replace the devices can be far more complex and can leave some patients with lasting complications.
"What we see is soft-tissue destruction and destruction of bone," said Dr. Young-Min Kwon, an orthopedic surgeon at Massachusetts General Hospital in Boston.
A recent editorial in a medical journal for orthopedic surgeons, The Journal of Arthroplasty, urged doctors to use the metal-on-metal devices only with "great caution, if at all."
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