Dr. Peter Thomas and team of Ludwig-Maximilians-University Munich reported that abrasive wear of implants produces metal particles. Metal particles come into contact with the surrounding tissue causing granulomatous foreign-body reaction, which in turn can lead to bone resorption and loosening of the implants.

Although the metal-to-metal implant approach has greatly reduced such events, still there may be risk of allergy. The researchers collected studied tissue and blood samples from 16 patients who had had revision surgery because of factors including pain, osteolysis and loosening of the stem. Periprosthetic lymphocyte-dominated inflammation was present in all patients.

Metal sensitivity was demonstrated in 3 patients (81%) and metal allergy on patch testing was seen in 11 patients (69%). Sensitivity to cobalt was shown by 7 patients, 7 patients for chromium and 4 patients for nickel. In all, 5 of the patients had a history of cutaneous metal allergy, and atopy was seen in 4. According to researchers, the 25% atopy rate, however, is similar to that seen in the general central European population.

Cutaneous metal allergy, particularly to nickel, told Dr. Thomas, is frequently found in the general population. Among those patients with failure of arthroplasty and peri-implant lymphocytic infiltration, there seems to be a high incidence of metal allergy.

Thus, he concluded, future research, including our team, will help to better characterize individuals at risk of allergy-related implant failure.