By Daniel W Todd, MD
We are seeing an increase in “implant rejections” in recent years. It seems patients are almost “rejecting” or chronically reacting to implants. Clinically this might manifest as a loose joint, chronic effusion, or even a proximal dermatologic reaction. The problem resolves with hardware removal and recurs with replacement. It is often felt to be due to a cell mediated (Gel and Coombs Type IV) reaction to Nickel, Cobalt, Bone Cement, or rarely Titanium. The metals are not allergens, but may act as Haptens. The current literature is limited and contradictory. Allergist, implanting surgeons, and dermatologists are on the forefront of research. It is felt to be a chronic cell mediated (Gel and Coombs Type IV) hypersensitivity reaction. The proximal tissue often demonstrates chronic inflammation, lymphocytosis and often even eosinophil infiltration.
Routine skin or blood testing for IgE mediated disease is not helpful. A Lymphocyte transfomation test (Melisa Test) is still investigational. Patch testing is the current standard of care for these tests, however, this too remains controversial. There are many false positives and false negatives.
In the US we often use the FDA approved “TRU Test”, however, this test lacks relevant metals. Dormer Labs in Canada or the Finn Chamber can offer a relevant metals tray. The metals can be applied to the skin on the initial office visit using CPT 99044 (# of allergens). A nurse reading can be done and photodocumentation given at 48 hours. A follow up physician visit can be made in 72 -96 hours to review the results. Antihistamines are irrelevant, however, steroids may contribute to a false negative.
Due to the fact there are know false positives and false negatives, patients should never be “cleared” for surgery. The patient and surgeon should just be told that the results of the patch test were negative.