Patch Allergen Testing for Surgical Implants
Hypersensitivity reactions are exaggerated immune responses that occur as a result of exposure to an antigen or allergen. Allergic contact dermatitis (ACD), also known as a type-4 delayed-type hypersensitivity response,1 is a type of reaction that causes an eczematous rash on the skin through undesirable activation of T-cell lymphocytes. In this condition, repeated exposure to a substance results in sensitization, during which CD8+ T cells begin to recognize the substance through the MHC class I peptide complex.2 Following sensitization, the body will react to the substance as an allergen and those primed T cells are recruited to the skin upon re-exposure, introducing inflammatory factors and resulting in the formation of a red, vesicular patch at the location of the exposure.2 ACD is typically difficult to diagnose through process of elimination simply because the reaction takes 48-72 hours to become apparent. Hypersensitivity is an important factor for patients that require surgical implants, and research has led to allergen testing techniques to prevent adverse physiological responses.
Metal hypersensitivity reactions in particular are highly prevalent in the general population. For example, it is estimated that three percent of males and 17 percent of females have a nickel allergy. For cobalt and chromium, this number hovers around 1-3 percent for both genders.3 The high frequency of metal ACD poses a serious problem for patients receiving metal surgical implants. Orthopedic implants can be made from a number of alloys, and typically include nickel, cobalt, chromium, molybdenum, zirconium and/or titanium.4 Should a patient have an existing hypersensitivity to one of these alloys, the surgical site may have difficulty healing, increasing the risk of infection, implant loosening, effusions, and chronic pain.5 It is therefore imperative that allergen testing be performed prior to insertion of metal surgical implants.
In order to identify any potential reactions to implants prior to surgery, a process called patch allergen testing may be performed by a physician. Dermatologists and allergists alike can be trained to perform patch testing. The procedure involves acute placement of a number of possible chemical allergens directly onto the patient’s skin for approximately 48 hours, then subsequent monitoring of the skin for the development of ACD for the next 48-72 hours. Correlations between chemicals and allergic reactions are then evaluated, and patients are typically given resources for allergen avoidance, including product safety lists, allergen fact sheets, and their testing results.
When it comes to patch testing specifically for orthopedic surgery, specific allergens should be considered. Ideally, the patch testing physician should be informed of the type of implant being considered, as well as the chemical makeup. However, in the case that the specific makeup of the implant is not known, certain chemical series are likely to be the most helpful. For example, testing a wide array of metals and bone cements would be relevant for most orthopedic implants.
While patch testing can be a lengthy, involved process, it is far preferable to dealing with the consequences of a hypersensitivity reaction once a surgical implant has already been placed. Severe reactions may result in complications, in some cases ultimately compromising the efficacy of the surgery and requiring re-implantation with an allergen-free alternative. Therefore, it is of utmost importance that orthopedic surgeons consider referring their patients – particularly those with a history of ACD – to receive patch testing prior to the date of their surgery.
References
1. Divkovic, M., Pease, C. K., Gerberick, G. F., & Basketter, D. A. (2005). Hapten-protein binding: from theory to practical application in the in vitro prediction of skin sensitization. Contact dermatitis, 53(4), 189–200. https://doi.org/10.1111/j.0105-1873.2005.00683.x
2. Vocanson, M., Hennino, A., Rozières, A., Poyet, G., & Nicolas, J. F. (2009). Effector and regulatory mechanisms in allergic contact dermatitis. Allergy, 64(12), 1699–1714. https://doi.org/10.1111/j.1398-9995.2009.02082.x
3. Thyssen, J. P., & Menné, T. (2010). Metal allergy–a review on exposures, penetration, genetics, prevalence, and clinical implications. Chemical research in toxicology, 23(2), 309–318. https://doi.org/10.1021/tx9002726
4. Hallab, N., Merritt, K., & Jacobs, J. J. (2001). Metal sensitivity in patients with orthopaedic implants. The Journal of bone and joint surgery. American volume, 83(3), 428–436. https://doi.org/10.2106/00004623-200103000-00017
5. Thomas P. (2014). Clinical and diagnostic challenges of metal implant allergy using the example of orthopaedic surgical implants: Part 15 of the Series Molecular Allergology. Allergo journal international, 23(6), 179–185. https://doi.org/10.1007/s40629-014-0023-3