Although not a common complication of hip, knee and other metal implants, the number of allergic reactions is growing, partly the number of joint replacements is growing, according to a presentation at the annual meeting of the American Academy of Dermatology. Nickel is the most common contact allergen.
About 10% of people in the United States will receive a medical implant sometime in their lives, and increasingly dermatologists are seeing patients who have a skin reaction associated with the metals used in those implants, according to a presentation today at the annual meeting of the American Academy of Dermatology Association in New Orleans.
The metals used, particularly nickel, are the most common culprits of allergic contact dermatitis, said presenter Golara Honari, M.D, clinical associate professor of dermatology at Stanford School of Medicine. “Cases in which patients are inquiring about a metal allergy as it relates to their metal implants — including joint replacements, rods, pins, screws, plates, and certain neurological and cardiac devices such as pacemakers, and dental devices — are becoming more prevalent as medical implants become more common.” Honari said that it is not clear what proportion of patients develop these reactions, although they are relatively uncommon.
“Cutaneous reactions can be localized. Occasionally, they can be systemic, and they also can have other morphologies,” she noted.
The use of metal implants is growing. The U.S. medical device market was $177.06 billion in 2021 and is projected to be $255.14 billion in 2029, Honari said in her presentation. Joint replacement surgeries continue to grow about 5% annually with a market value of $19 billion in 2021. In the United States, there are about 450,000 hip replacements annually, and this is projected to increase to 572,000 a year by 2030. There are about 790,000 knee replacements annually in the United States and this is expected to grow to 3.48 million 2030. Additionally, more than 2 million vascular stents are implanted in the United States.
Implanted devices can sometimes corrode, and chemicals can leak into the body. This can cause an immune response, but interactions between the materials and the body are complex, Honari said. Reactions can include hypersensitivity, chronic inflammation, immune suppression, immunostimulation and autoimmunity.
For hip and knee replacements, cutaneous and systemic reactions can occur within weeks to months of the implantation. Most common are localized reactions that present as dermatitis affecting the skin over the site of the implant.
Nickel is the most common contact allergen, and the incidence, especially among children tested in the United States, has almost quadrupled over the last three decades. Chromium is the third most common allergen in the population. Titanium is generally considered biocompatible but can cause a rare reaction. Honari said that she has seen allergic reactions to the bone cement that sometimes used in surgeries.
Honari recommends that patients who have a history of metal allergies consider patch testing prior to surgery. After surgery, she recommends ruling out inflammation if a patient presents with an allergic reaction. “However, if an allergic reaction is suspected, the first line of treatment may be topical and/or oral medications, like anti-inflammatories, which can relieve pain, reduce inflammation, and bring down a high temperature,” she said.