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Allergy to medical implants on the rise

Allergy to medical implants on the rise

Biomedical implants are becoming more and more common in today’s world of modern medicine. For instance, roughly one-million knee replacement surgeries were done in the U.S. last year. With these numbers, it’s not a surprise that allergic reactions to the implants is also increasing.  Diagnostic features of metal hypersensitivity to an implant include: rash developing in the skin overlying the implant, generalized skin rash beginning weeks to months after the implant, unexplained pain and/or failure of the implant, positive patch test to the metal used in the implant and complete resolution of symptoms after removal/replacement of the offending implant.

The most common causes of metal hypersensitive reactions are orthopedic devices. Next most common are dental-related metals. Much less common are vascular stents, cardiac pacemakers and gynecologic implants, such as intrauterine devices (IUDs).  The metal type causing the most problems is stainless steel — which contains nickel, cobalt and chromium – all known potential allergens. Less troublesome are titanium alloys and zirconium.

The most common allergic symptom seen with cardiovascular stents is rapid re-stenosis of the “stented” artery. In the case of pacemakers/internal defibrillators, it is a rash in the skin overlying the device. Unfortunately, there are no standardized test kits for metal testing. Currently, skin-patch testing with a small piece of the implant metal, and a blood test to see if white blood cells react are in use, but results can vary from lab to lab. Most vexing is the fact that the allergy can develop after the implant. However, any implant candidates with previous allergic issues with the proposed metal should undergo pre-testing — including reactions to piercings, tattoo ink, jewelry or metal snaps.

Internal medical devices: Reactions spotlight metal allergy

Internal medical devices: Reactions spotlight metal allergy

Dear Dr. K: Do you have anything to share from your recent trip to the Southeastern Allergy meeting?
The meeting was excellent. The presentation I found most provocative was on allergy to medical devices. Unfortunately, this is becoming a more common source of allergic difficulty.  The spectrum of reactions has included allergy to joint replacements, fracture-stabilizing metals, spine-straightening rods, cardiac pacemakers, defibrillators and their wires, coronary and other arterial stents and dental products, including implants and orthodontic materials.
Although some reactions are to glues and adhesives, it seems that metal allergy is the primary cause for these reactions. The reaction to metals is found more commonly in people who already have known metal allergy, such as nickel allergy to earring materials. In fact, nickel allergy is the most common metal allergy, followed by chromium and cobalt allergies.
People who have multiple body piercing sites have a greater likelihood of developing metal allergy. The American Academy of Allergy recommends avoiding ear or other piercings until age 10 to lessen the chance for developing metal allergy.  It was once thought that titanium was allergenically inert but, unfortunately, allergic reactions are occurring to some titanium alloys.
The most common manifestation of the allergic reaction is a rash in the skin surrounding the implant site, or in the mucous membranes in the mouth in the case of dental allergy. In some patients there can also be sites of remote rash and other systemic symptoms, such as achiness and pain.
A special scenario can exist with arterial stent allergy. Sometimes the only manifestation is what is called rapid re-stenosis. That is, the artery that was reopened with the stent quickly closes again due to the allergic inflammation.
If someone has a known metal allergy and needs an implanted material, it is recommended that a patch test be done with the material prior to its being used.  Unfortunately, there are not yet any standardized test kits, so the approach is more seat-of-your- pants in nature. Usually a small piece of the to-be implanted metal can be obtained and a patch test carried out. In some very special cases, instead of a patch test, the test metal is actually surgically placed in a superficial pocket below the skin for several weeks to see if an allergy develops.  Obviously, this more invasive test is only undertaken in special high-risk cases.