Frequently Asked Questions About Metal Allergy and Joint Implants Made of Metal
I'm having a lot of pain and swelling in my knee (but no rash) following my joint implant surgery. Could this be an allergy to the metal implant?
While this has been reported, it's considered rare, especially if there is no rash overlying the joint.
I'm starting to see more patients who have this concern. As more and more people in the United States undergo joint replacement surgery, I'm seeing a lot more questions about allergic reactions. Specifically, can an allergic reaction explain ongoing joint pain and swelling?
While this has been reported, it is considered rare, especially in the absence of a rash. Some joint implants are made of stainless steel that contains nickel, or an alloy (mixture of metals) that contains nickel. Many people in the United States (close to 20% by some estimates) are allergic to nickel. Although many people are allergic to nickel, we're not seeing the same rates of allergy to nickel-containing joint implants.
Other implants use metals such as cobalt and chromate, which are other types of metals that some people can become allergic to.
What happens if you are allergic to nickel, and you were to receive a joint implant that contains nickel?
The answer to that depends on the individual. We suspect that in many cases, probably nothing will happen. In other cases, the patient may develop a rash overlying the site of the surgery. If a patient has a known metal allergy prior to the surgery, many surgeons will choose to avoid that particular metal. Of course, this depends on the particular surgery planned. Some joint materials are better than others in certain situations, and the decision on which implant material to use will depend on an informed conversation between you and your surgeon.
What if you had a joint implant surgery, and now have redness and swelling of the joint area? Should you have allergy testing to see if you might be allergic to the implant?
This is a very difficult question to answer. In most cases (although not always) allergy to a joint implant will show up as a rash overlying the site of the surgery. In some cases, this rash may spread to other areas of the body. If the patient undergoes patch testing, and is found to be allergic to nickel, cobalt, or chromate, and that particular metal was used in the implant, then it is possible that allergy to the implant is causing the rash. If the rash is localized, and not too severe, then all efforts are made to treat the rash (without any surgical procedures). If these efforts do not work, then the patient may choose to have a discussion with their surgeon and ask if it would be worthwhile to remove the current implant and replace it with one made of a different material. Since this is a major surgery, all the pros and cons of this decision must be discussed with your surgeon.
If the patient has no rash at all, and is only experiencing redness and swelling of the joint, then this is a much more difficult question to answer. Research in this area has found that there is no clear answer.
In some cases, patients have been allergic to a metal that is used in their implant. However, even though the patient is allergic, this does not necessarily mean that the allergy is causing the joint symptoms. In some reported cases, removing the implant and replacing it with a different material has improved the symptoms. In other reported cases, this has NOT improved the symptoms. There are no predictive tests at this time to know what will happen.
This is why I call testing for metal allergy in patients who are experiencing joint pain or swelling (without any rash in the area) following implant surgery a "long shot". If you are allergic to a metal such as nickel, and nickel was used in your implant, and you undergo another major surgery to replace the implant, your symptoms still may or may not improve.
There are major limits in the information we can provide to help you predict what will happen in your case. In other words, we can inform you if your patch testing shows an allergy to nickel, cobalt, or chromate, but we cannot predict what would happen with your symptoms even if you undergo another major surgery to replace the implant.