Immune response in adverse reactions to metal debris following metal-on-metal total hip arthroplasty.

<bold>Background: </bold>The purpose of the present study was to determine whether T cell-mediated type IV hypersensitivity reactions could be a major cause of adverse reaction to metal debris (ARMD) after metal-on-metal total hip arthroplasty (THA).<bold>Methods: </bold>Thirteen patients (1 man and 12 women; mean age 68 years, age range 60 to 83 years) with ARMD underwent revision surgery following metal-on-metal THA (15 hips). Lymphocyte stimulation testing was conducted. Periprosthetic tissue specimens underwent immunohistochemical studies.<bold>Results: </bold>Lymphocyte stimulation testing showed that five patients were nickel-sensitive, and one patient was also cobalt-sensitive. Immunohistochemical studies showed that T cells were dominant in five hips, and B cells were dominant in 10 hips. In four of the five patients with a positive lymphocyte stimulation test, the dominant lymphocytes were T cells, suggesting type IV hypersensitivity. The major cause of ARMD was not type IV hypersensitivity in the remaining nine patients.<bold>Conclusion: </bold>Metal hypersensitivity does not appear to be the dominant biological reaction involved in the occurrence of ARMD. [ABSTRACT FROM AUTHOR]