Wetenschapsforum

Immune response to implants is commonly reported in the literature and can include hypersensitivity related to pacemakers, dental implants, and orthopedic hardware. Furthermore, up to 13% of people are sensitive to nickel, cobalt, or chromium.The development of metal sensitivity after implantation of orthopedic hardware is common. Metal sensitivity is also correlated with osteolysis and aseptic loosening of implanted metal hardware. However, statistical reviews of cases involving adverse reactions after implantation of metal hardware demonstrate that metal sensitivity can be proven causative in less than 0.1% of cases in which sensitivity reactions exist. Therefore, the clinical significance of metal sensitization remains a question.

Nonetheless, the orthopedic surgeon must be aware of the potential problem, and when other more common causes of implant failure have been excluded, the possibility of allergic reaction to the metal must be considered, evaluated, and treated. According to Huber et al, the presence of corrosion products and a hypersensitivity reaction in patients suggests that there is a relationship between corrosion and implant-related hypersensitivity. In 11 cases in which periprosthetic tissue contained corrosive elements (solid chromium orthophosphate corrosion products) after aseptic loosening of articular implants, immune-response tissue reactions were identified in all 11 cases.This issue of the clinical significance of sensitization to implanted metals has long been a matter of debate in the literature. While some studies have shown that sensitization to metal implants is prevalent. Others refute these data and have concluded that not only does hypersensitivity fail to develop ; but patients with metal hypersensitivity prior to implantation actually become desensitized and anergic after implantation. Some authors have further suggested that metal hypersensitivity may be associated with bone loss and aseptic loosening of implanted devices, while other authors have concluded that even if a metal allergy exists, no adverse effects occur.

These contradicting studies make it difficult for the orthopedic surgeon to make the diagnosis of symptomatic metal allergy with confidence. The confusion could be the result of the presence of different metals in the implants, different manufacturing methods, small numbers of patients in the studies, and difficulty in achieving adequate diagnosis. More research is clearly needed. In the meantime, the diagnosis must be made with caution. Infection, nonunion, aseptic loosening, other inflammatory conditions, mechanical failure of the implant, and malalignment issues must be excluded first before assuming the problem is an allergic reaction.

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