Metal sensitivities can lead to failure of replacement joints, and patients should be carefully evaluated for a possible reaction after the surgery, according to a new review of past research.
“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 second surgeries, called “revisions,” to correct problems with the first replacement, according to the authors.
In joint replacement surgery, an existing joint with arthritis or otherwise damaged cartilage is replaced with a prosthetic version.
Hip and knee replacements are most common, with more than a million performed in the U.S. in 2010, according to the Centers for Disease Control and Prevention. They usually consist of a metal ball that fits into a sturdy plastic socket, according to the American Academy or Orthopedic Surgeons.
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 percent of women and three percent 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 is published in the Annals of Allergy and 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 talk to their doctors and consider having an allergy patch test, Pinson said.
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.”