Joint replacement failure due to component ‘allergy’: more common and treatable than suspected

Published online: August 1, 2021

Joint replacement surgery constitutes the highest in-patient cost for Medicare, and the procedure is rapidly expanding to include younger populations world-wide. Ten percent, however, fail, defined as an implant that does not function properly. Infection or mechanical mismatch with the patient are expected causes, but for some, the reason is elusive. Many implant components are known to cause sensitization (‘allergic’) reactions in other settings and exposures such as metal working, costume jewelry, tattoos, acrylic nails, and skin glue. These common sensitizers include nickel, cobalt, chromium, molybdenum, manganese, and bone cement. It therefore makes sense to look for similar reactions to these materials when used in joint replacements that fail.

Mayer and Pacheco have summarized their results from the MetALLs^® program clinic they established at National Jewish Health to evaluate patients with failed implants for sensitization to implant components and have published these in the August issue of The Journal of Allergy and Clinical Allergy: In Practice. The patients in this study were referred by their orthopedic surgeon for implant failure not explained by infection or mechanical issues. These selection criteria enriched the patient population for implant allergies, as other causes had already been excluded. Patients underwent standardized patch testing to metals and bone cement used in implants, a blood test for nickel allergy developed at the institution, as well as standard blood work and symptom questionnaires. When a patient developed a positive reaction to a metal or bone cement used in their replacement, that information was directly communicated with the orthopedic surgeon, along with recommendations for revision hardware that included components to which the patient did not react in testing. Nine to twelve months later, the authors were able to recontact 64% of the initial group (67/105) to determine outcomes. These included 35 who were sensitized to an implant component, and 26 who were not. The authors were also able to compare outcomes of those revised to those who were not revised in each group.

In this group of patients, rates of sensitization to implant components were high: 59% were allergic to one of more components of their implants, including 33% of the total to a metal, and 37.5% to bone cement. A history of self-reported skin reactions to metal showed low (36%) sensitivity in predicting metal allergy documented by patch test or nickel blood test, suggesting that some developed the allergy after the implant was placed (i.e. with exposure).  The nickel LPT showed moderate sensitivity (60%) and excellent specificity (96%) in comparison to the nickel patch test. A model predicting implant sensitization identified younger age (59.4 years vs 64.2 years), reports of itching, loosening and instability as significant characteristics. Demographics, joint involved, and rates of metal or bone cement positivity did not differ between those who followed up, and those lost to follow-up, suggesting that the follow-up results are representative.  

There are several important conclusions: 1) all patients who were revised did better, but those revised due to implant allergy did significantly better in all symptoms measured, including decreases in pain, swelling, instability, and range of motion; 2) those sensitized to their implants and not revised did not improve with time; and 3) in the group without implant sensitization, the symptom differences between those revised and not revised group were not significant, except for an overall measure of doing better. There are limitations to this study: it was relatively small (n=105), had limited follow-up participation (n=67), and time (9 – 12 months), and was based on patient reported outcome measures without a functional component. Nonetheless, the findings are important indicators of the prevalence of implant ‘allergy’ as a cause of joint replacement failure, demonstrate how to make the diagnosis, and confirm its relevance based on significant improvement in outcome measures.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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