CD24 Case series: pitfalls of implanted metals

Abstract

Orthopaedic metal implant rates are increasing with the rising age of the population and higher functional demands of an increasingly active ageing society. Estimates suggest an increase in the frequency of joint replacements of between 300% and 600% by the year 2030. While relevant allergy to metallic implants is rare, it is important to be aware that reactions can occur. We present three cases of confirmed allergy to metal prostheses on patch testing. The cases include cobalt allergy from a shoulder prosthesis, cobalt allergy from a knee prosthesis associated with elevated serum cobalt levels, and titanium allergy from a metal plate in the lower leg. In all three patients, an eczematous rash was present over the affected metal prostheses, which eventually completely resolved on removal of the metalware. In the case with elevated serum cobalt levels, there was additionally a widespread eczematous rash, together with nonspecific symptoms of dizziness and lethargy. The serum cobalt levels normalized approximately 1 year after implant revision. The timing of the rashes over the implants varied from occurring days after their insertion to > 9 months. It is important to be aware of the common and atypical presentations of metal implant allergy. Interpretation of patch test results to metal haptens comes with great consequences, given that the determination of allergy generally requires removal of the metal implant. Given that metals can be irritating on patch testing, it is our practice to always perform duplicate patch testing of metal haptens in this situation.