Some of the nation’s leading orthopedic surgeons have reduced or
stopped use of a popular category of artificial hips amid concerns that
the devices are causing severe tissue and bone damage in some patients,
often requiring replacement surgery within a year or two.
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
"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.”
The limited studies conducted so far estimate that 1 to 3 percent of
implant recipients could be affected by the problem. Given the large
number of people who have received metal devices, that could mean
thousands of patients in the United States. Reports suggest that women
are far more likely than men to be affected.
All the major orthopedics makers sell these devices. Several companies
said in statements that the implants did not pose a significant risk and
that the incidence of metal debris problems was extremely low.
For example, Zimmer
Holdings, one of this country’s biggest producers of artificial
joints, said in a statement that published data "suggests that ion
release levels from Zimmer’s metal-on-metal hip systems are commensurate
with other metal-on-metal systems in the industry, and are not
associated with significant risk to patients.”
But some surgeons are concerned that they may only now be seeing the
leading edge of a mounting problem. The current generation of
metal-on-metal devices is still relatively new, having been used
increasingly over the last decade.
Studies show that the devices can shed atomic-size particles of metals
like chromium and cobalt that can be readily absorbed by tissue or enter
Surgeons at Rush University Medical Center have performed about two
dozen replacement procedures because of metal debris over the last year,
said Dr. Joshua J. Jacobs, the head the orthopedic surgery department
there. A similar number of patients have had metal-on-metal hips
removed at the Mayo Clinic, according to Dr. Daniel J. Berry, Mayo’s
head of orthopedic surgery.
Dr. Berry added that surgeons at the Mayo Clinic had reduced by 80
percent their use of metal-on-metal implants over the last year in favor
of those made from other materials, like combinations of metal and
plastic. Other doctors said that to be cautious they were also scaling
back their use of the all-metal implants until the scientific evidence
It is not clear whether some makers’ devices are more prone to the
debris problem than others. But some experts argue that some
manufacturers, in a rush to meet the demand for metal-on-metal devices,
marketed some poorly designed implants and that some doctors fail to
properly implant even well-designed ones.