Utility of Patch Testing and Lymphocyte Transformation Testing in the Evaluation of Metal Allergy in Patients with Orthopedic Implants

Abstract

Total joint arthroplasties are increasingly common orthopedic procedures performed throughout the United States. Implant failure after these procedures occurs due to a number of causes such as infection or mechanical problems, with metal hypersensitivity being an area of growing interest. The nature and mechanism of a causative relationship between metal hypersensitivity and implant failure have been unclear as it is not known whether implant failure occurs due to a previous metal allergy or metal allergy results from secondary sensitization via metal exposure in existing failing implants. Overall, there appears to be growing support and evidence for metal-hypersensitive patients having worse outcomes with regard to total hip and knee arthroplasties. However, there are conflicting recommendations (outside of Nuss procedures) for pre-implant testing for metal hypersensitivity as testing has not consistently been shown to change patient outcomes.

Metal Hypersensitivity in Joint Arthroplasty

“… 10 , 11 It is thought that jewelry is the most common cause of exposure, but patients can be exposed to metal in various ways. 12 This can occur through the skin in the form of cell-phones, clothing fasteners, and leather.…”

“…Skin patch testing is, however, simple with a low cost and an excellent initial test for patients with a metal sensitivity and has a low risk to the patient. 5 , 12 Potential disadvantages include different mechanisms of reactivity than that seen in deep tissues, the cost and time associated with the test, the difficulty to report quantifiable and standardized results, and the process of in vivo patch testing that could induce sensitization in a previously nonsensitized patient, leading to failure due to MH. 5 , 9 In contrast to skin patch testing, lymphocyte transformation test is more sensitive and cannot induce HS, with testing seeing that it is done in vitro.…”

“…The erythematous reactions to the allergen are then rated at 48, 72, and 96 hours or more after placement. 3 , 12 The reactions are categorized as 1+, 2+, or 3+. Patch test reactions rated 2+ or 3+ are more likely to cause implant reactions than 1+ patch testing.…”

Metal allergy after the Nuss procedure for pectus excavatum: a review

“…For the detection of metal hypersensitivity in patients with implants lymphocyte transformation testing is also used. The test uses the measurement of lymphocytes in peripheral blood that are produced in the span of 7 days following allergen exposure [ 18 ]. The ratio of lymphocyte proliferation after allergen challenge to proliferation without the allergen is expressed as a stimulation index [ 16 , 17 ].…”

“…Currently, there is still a debate concerning the need of pre-implant testing in orthopaedic surgery as testing has not consistently been shown to change patient outcomes [ 18 ].…”