You have your MoM's ions
Public release date: 9-Mar-2010
Study finds elevated levels of cobalt
and chromium in offspring of patients with metal-on-metal
hip implants
Hip replacement patients with metal-on-metal (MoM)
implants (both the socket and hip ball are metal) pass metal
ions to their infants during pregnancy, according to a new
study presented today at the 2010 Annual Meeting of the
American Academy of Orthopaedic Surgeons (AAOS). Data showed
there is a correlation between cobalt and chromium levels in
the mother and those in her infant at the time of delivery.
"Although the affects of metal ions in maternal and fetal
subjects are unknown, the fact that the placenta is not a
complete barrier to the transport of these metals is
noteworthy," said Joshua J. Jacobs, MD, Professor and
Chairman of Orthopaedic Surgery at Rush University Medical
Center in Chicago. "As metal-on-metal implants increase in
popularity and use, especially among young, active patients,
women of child-bearing age and their doctors should be aware
of these findings when considering their hip replacement
implant options."
Researchers evaluated three patients who had either a
unilateral (only on one hip) MoM primary total hip
arthroplasty or unilateral MoM hip resurfacing joint
replacement and no other metal implant in the body. The
implant group's metal ion levels were compared within the
group, between mothers and their infants, and to those of a
Control Group comprising seven women of child-bearing age
(mean age of about 32 years) who did not have any metal
implants and their infants.
For all subjects, maternal and umbilical cord blood was
obtained at the time of delivery and tested for blood serum
concentrations of titanium, nickel, cobalt and chromium
using inductively coupled plasma mass spectrometry (ICP-MS),
a highly sensitive technique that can detect trace amounts
of metals in biological samples.
The data found:
-
Mothers with MoM implants and their offspring had
elevated Chromium and cobalt levels compared to the
cohort without metal implants.
-
A correlation existed between maternal and infant
cobalt and chromium levels in the Implant Group, while
the Control Group showed no correlation.
-
Offspring of women with MoM implants had about half
the levels of cobalt in their bloodstream as their
mothers and approximately 15 percent of their mother's
chromium levels, while there was no significant
difference among ion levels between mothers and infants
in the Control Group.
-
There was no statistically significant differences
in levels of titanium or nickel among any of the
cohorts.
Dr. Jacobs noted that because the cobalt and chromium
levels of the infants did not increase to those of their
mothers, the data suggests the placenta does modulate the
transfer of metal ions to the fetus.
"The next step is to find out what, if any affect metal
ions have on fetal or infant development," he said. "The
best way to do that would be through the establishment of a
national joint registry by which clinicians could input and
access long-term data."
He added that, in the meantime, medical device companies
are feverishly working to develop new technologies that will
reduce the release of ions through improvements in wear and
corrosion properties of metal implants. "Any advancements in
this area will directly benefit patients," he said.
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