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Metal Ion Hypersensitivity in Metal-on-Metal Hip Arthroplasty

Y.-S. Park, Y.-W. Moon and S.-J. Lim Download here

Total hip arthroplasty with use of metal-on-metal bearings has been reintroduced as an alternative to metal-on-polyethylene bearings because of theoretical advantages such as reduced wear and a lower prevalence of osteolysis. However, we have observed early osteolysis in nine patients (ten hips) out of 165 patients (169 hips) who had been managed with total hip replacements using a contemporary metal-on-metal hip design and investigated the possible etiologic role of metal hypersensitivity.

The nine patients who had an osteolytic lesion had a significantly higher prevalence of hypersensitivity to cobalt, as determined by patch testing, when compared to nine controls (p = 0.031). The retrieved periprosthetic tissues from the two revised hips showed no evidence of metallic staining, but microscopic analysis revealed a perivascular accumulation of CD3-positive T-cells and CD68-positive macrophages, and an absence of both particle-laden macrophages and polymorphonuclear cells.

Immunohistochemical analysis demonstrated that potent bone-resorbing cytokines such as IL-1β and TNF-α were produced mainly by infiltrated lymphocytes and activated macrophages.

These findings raise the possibility that early osteolysis in this second-generation metal-on-metal hip replacement is associated with abnormalities consistent with delayed-type hypersensitivity to metal.

In conclusion, our findings raise the possibility that early osteolysis in patients with this second-generation metal-on-metal hip replacement is associated with a delayed-type hypersensitivity to metal, mainly cobalt. As a result of our findings, we are reluctant to implant modern metal-on-metal bearings in patients who have a history of allergic reaction to a metal implant or metallic wear.

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