What is Metal Sensitivity?
Metal sensitivity(or metal hypersensitivity) is an allergic reaction triggered by the body’s immune system. Unlike the clear and immediate reaction one might experience to pollen and dust, allergies to metal present in a more delayed fashion. Basically, your body develops a negative memory regarding a specific antigen (i.e. metal) and overreacts when that metal shows up again. It’s not usually an immediate response like a bee sting, but rather, it can take several days or more before the signs begin to appear.
Metal Content in Total Joint Implants
When a patient has a reported allergy to an orthopedic implant, it is usually a reaction to nickel, cobalt, or chromium. The incidence of sensitivity to nickel (usually seen as a skin reaction to cheap jewelry) is 10-15%, but to date, there is not a consensus between this type of reaction and issues with orthopedic implants containing nickel.
What are the Signs of a Metal Allergy?
Common symptoms of a metal allergy condition are:
- skin hives, eczema, redness and itching resulting from skin contact (from cheaper/costume jewelry)
- inflammation and pain associated with a metal orthopedic or dental implant
The signs and symptoms of metal implant sensitivity are not well-defined. While there are a relatively small number of cases scattered around the internet and in clinical case reports of more profound reactions such as skin rash, blistering, significant warmth, and generalized weakness, the findings for deep orthopedic implants are often a diagnosis of exclusion.
How Can You Test for Hypersensitivity?
Patch Testing– involves the incorporation of different potential allergens onto an adhesive grid that is then left in place for 24-96 hours. The skin reaction is recorded from mild-severe. The benefit of this type of test is that its administration is common for trained dermatology and allergy clinics. The drawback is that this is a test of skin reaction to metal and does not assess the reactivity of deeper tissues. Additionally, there is varying standardization reported for this test.
Lymphocyte Transformation Test (LTT)– blood test which tests immune cell responses to different metals. Metal-LTT testing can identify which people are susceptible to metal sensitivity. Metal-LTT testing can also identify which specific metals cause sensitivity responses and which specific metals do not cause excessive immune reactions. The drawback is that this test requires a special kit and is only performed by a small number of laboratories. The benefit is a deeper and more clear assessment of hypersensitivity. See the links below to learn more and order the kit.
Are There Options for Patients with Allergies?
Studies have shown that 20-25% of people with well-performing total joint replacements have a metal hypersensitivity, and 60% of individuals with poorly performing implants have a metal hypersensitivity. While not all patients sensitive to implant-related metals will do poorly, there is a correlation between metal hypersensitivity and decreased post-operative satisfaction.
When a patient has a history of metal hypersensitivity, there may be lower risk implant options for joint replacement, and the patient should discuss these options with their surgeon. Patients with nickel allergies are often treated with implants containing mostly titanium and ceramics. Oxidized zirconium has been proposed as the lowest nickel implant option for knee replacements. Patients must understand that allergies may change the surgical options, and that not all complex procedures can be performed without the potential for using an implant that may incite a response.
Should You Be Tested?
Not every patient needs to be tested for metal allergies because the clinical incidence is relatively rare. If you have had a reaction to jewelry or other metals in the past, you should have a discussion with your surgeon about testing. I prefer the LTT for patients with a metal sensitivity history to confirm my proposed implant choices are safe. When in doubt, talk with your surgeon!
We are happy to assist you in making the best decision, and are here to answer all of your questions. Contact Dr. Werger at The Bone and Joint Center for a consultation and to learn which option may be best for you.
(617) 779-6500
Hallab N, Merritt K, Jacobs JJ. Metal sensitivity in patients with orthopaedic implants. J Bone Joint Surg Am 2001; 83-A: 428-36
Guenther, D., Thomas, P., Kendoff, D. et al. Allergic reactions in arthroplasty: myth or serious problem? International Orthopaedics 2016;40: 239.
