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 “We think patients and doctors should be aware of hypersensitivity
or allergy reactions to implanted joints and to monitor for signs
and symptoms,” said Dr. Michelle L. Pinson, one of the authors of
the new paper.
“However, a hypersensitivity reaction to a hip or knee replacement
is not that common, when you look at all the patients who have had
successful and stable joint replacements,” added Pinson, of Wilford
Hall Ambulatory Surgical Center in San Antonio, Texas.
The number of total joint replacements in the U.S. is on the rise,
and so is the number of revisions, according to the authors.
Earlier replacement joints were all-metal and prone to shedding as
the parts rubbed against each other and surrounding tissue.
Cobalt, chromium, molybdenum, tungsten, manganese, titanium,
aluminum, vanadium and nickel are all common metals used in joint
replacements.
According to an unrelated 2010 study in Chemical Research in
Toxicology, up to 17% of women and 3% of men are allergic to nickel.
“For some patients, an allergic reaction to metal in a joint can be
very serious, however many reactions are mild and not too serious,”
Pinson said.
There is no consensus on how to treat that kind of joint failure,
they note, but for minor cases pain may be managed with medications,
physical therapy or steroid injections.
If the joint swells or loosens, it may need to be replaced with
different components, for example non-nickel components if that’s
what causing the trouble.
Pinson and her colleagues included randomized controlled trials,
case studies, observational studies and previous reviews in their
analysis, which was published online June 13 in the Annals of
Allergy, Asthma & Immunology.
Among their conclusions is that it’s still not clear whether metal
joints increase sensitivity to metal, or if existing metal
sensitivity leads to more joint failure after implantation.
Patients who experience new joint pain, rash or hives that don’t
respond to usual treatment within several weeks to a few years after
joint replacement should be considered for an allergy patch test,
Pinson said.
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Most researchers suggest that patients with a history of metal
sensitivity should be tested before undergoing surgery, she said.
“In general, hypersensitivity testing results may guide surgeons to
consider implants with no or minimal amounts of the metals to which
the patient positively reacted, especially in the case of joint
implant revisions,” she said.
Even so, it’s still not entirely clear what a positive result on a
skin or blood metal allergy test means, according to Dr. Jared R.H.
Foran of Golden, Colorado, who was not part of the new study.
Foran is the section editor for joint replacement for the American
Academy of Orthopedic Surgeons.
When a joint replacement fails, allergy may be involved, but it is
far down on the list of possible reasons, he said.
“Also, there are literally millions of patients that have metal
plates or screws in their bodies from other types of orthopedic
work, such as fracture care, etc., yet we rarely diagnose metal
hypersensitivity in these patients,” he told Reuters Health by
email.
There are still many questions to be answered, he said.
“There are plenty of patients that will test positive for metal
allergy, but be perfectly happy with their joint implant,” he said.
“There are many more that will be unhappy with their implant, but
test negative for allergy.”
Total hip replacements tend to be much more successful than knee
replacements, which is almost exclusively where there seem to be
problems with metal allergies, he said.
“The real question is what do we do with the patients that have a
poorly functioning total knee or hip and a positive allergy test,
with no other clear explanation of why they hurt,” Foran said. “We
simply do not have the data in 2014 to make a real strong assessment
of the best course of action for those patients.”
SOURCE: http://bit.ly/1nhZJRu Ann Allergy Asthma Immunol 2014.
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