The association between metal allergy, total knee arthroplasty, and revision: study based on the Danish Knee Arthroplasty Register.

BACKGROUND AND PURPOSE: It is unclear whether delayed-type hypersensitivity reactions against implanted metals play a role in the etiopathogenesis of malfunctioning total knee arthroplasties. We therefore evaluated the association between metal allergy, defined as a positive patch test reaction to common metal allergens, and revision surgery in patients who underwent knee arthroplasty.

PATIENTS AND METHODS: The nationwide Danish Knee Arthroplasty Register, including all knee-implanted patients and revisions in Denmark after 1997 (n = 46,407), was crosslinked with a contact allergy patch test database from the greater Copenhagen area (n = 27,020).

RESULTS: 327 patients were registered in both databases. The prevalence of contact allergy to nickel, chromium, and cobalt was comparable in patients with and without revision surgery. However, in patients with 2 or more episodes of revision surgery, the prevalence of cobalt and chromium allergy was markedly higher. Metal allergy that was diagnosed before implant surgery appeared not to increase the risk of implant failure and revision surgery.

INTERPRETATION: While we could not confirm that a positive patch test reaction to common metals is associated with complications and revision surgery after knee arthroplasty, metal allergy may be a contributor to the multifactorial pathogenesis of implant failure in some cases. In cases with multiple revisions, cobalt and chromium allergies appear to be more frequent.