Allergy to implants is an emerging topic in orthopedic literature, yet its prevalence in non-weight-bearing prostheses is poorly documented, with only 3 cases described in the literature for trapeziometacarpal arthroplasty. The objective of this study was to evaluate the clinical outcomes following the removal of trapeziometacarpal prosthesis in suspected cases of metal allergy.

This retrospective cohort study spans from 2004 to 2024. We included all cases of trapeziometacarpal implant failure suspected to be due to metal allergy. Criteria analyzed included type of prosthesis, clinical signs of allergy (pain, itching, local dermatitis), radiological signs (bone lysis or aseptic loosening), skin patch tests (positive for prosthesis components), intraoperative findings, histological status, treatment, and outcomes after implant removal or replacement. Exclusion criteria included signs of infection, implant malposition, or a history of trauma.

Nineteen women and two men were included, with a follow-up period of 23 months. There were 9 Electra®, 7 Rubis II®, 5 Camargue®, and 2 Moovis® implants. All cases exhibited persistent, non-mechanical pain. Swelling was observed in 5 cases and dermatitis in 3 patients. All trapeziometacarpal joints remained flexible, unlike in cases of algoneurodystrophy. Radiologically, 12 cases of bone lysis were observed, with significant aseptic loosening in 4 cases, while no pathological findings were noted in 10 patients. Skin patch tests were conducted on 18 patients, with positive results for at least one component of the prosthesis in each patient (14 cobalt, 2 chrome-cobalt, 3 nickel, and 1 titanium). Intraoperatively, synovitis was observed in all patients, with macroscopic metallosis particularly evident in metal-on-metal prostheses, and bone lysis and loosening in half of the patients but no histological signs of metallosis were found. In all cases, symptoms either diminished or disappeared following prosthesis removal or replacement.

Although rare, implant allergy should be considered in cases of persistent, unexplained symptoms. Management should include full disclosure about the uncertain nature of this condition. The only way to confirm a diagnosis of metal allergy may be the resolution of symptoms after implant removal. In our experience, revision or replacement surgeries are prone to complications and are often more complex than the initial surgery. Therefore, in cases with a history of dermal metal allergy or allergy to other orthopedic materials, we recommend the use of hypoallergenic prostheses as a first option.

Metal implant allergy remains a diagnosis of exclusion, with no guidelines for either diagnosis or treatment. It is essential to investigate this condition thoroughly.