The metal alloys used in artificial joints are subject to corrosion when they come in contact with the body. This process can lead to metal ions being released into the blood and surrounding local tissue, causing a reaction to soft tissue and bone. Although most knee replacement results are excellent, this type of immune response occurs in about 10% of the general population and can result in knee revision surgery.1 Just like typical food and air sensitivities, reactions to metals can also change over time. If you already have a metal implant in your body, the rate of a hypersensitive response will increase to 20%1, and if you are experiencing complications or issues with your knee replacement, you could be part of the 60% of the population who shows sensitivity to metals.1 It is important to know that although there are tests to determine if you may be sensitive to metals, there is no current blood level that would indicate or conclude that a person has a sensitivity or reaction.1
Here’s what you should know about metal sensitivity:
- Implant related reactions are considered type IV Delayed Type Hypersensitivity (DTH) which is different from food-related reactions/allergens.2
- Common metals and metal alloys found in implants can trigger a response in the body, however what levels that will trigger a response in not known1
- 10-15% of patients are affected by reactions to metals such as cobalt, nickel, and chrome; common metals used in joint implants1
- Delayed Hypersensitivity reactions can include: implant loosening, warmth or swelling around knee, skin rash2
If you experienced a reaction to jewelry, metal belts or previous implants, you should discuss with your doctor if you are a candidate for alternative implant options and if testing for metal hypersensitivity is right for you.
1 Hallab N, Merrit K, Jacobs J, Metal Sensitivity in Patients with Orthopaedic Implants, J Bone Joint Surg. Am. 2001; 83A 428-36
2 Mihalko W, Goodman S, Hallab, N, Jacobs J. Skin Patch Testing and Associated Total Knee Outcomes. AAOS Now. September 2012
CHART Hallab NJ, Anderson S, Stafford T, Gant T, Jacobs JJ. “Lymphocyte responses in patients with total hip arthroplasty.” J Orthop Res 2005; 232:384e91.