Existing and Novel Assessment Methods for Metal Sensitivity in Elective Lower-Limb Arthroplasty—A Scoping Review

Background: Metal sensitivity is a possible cause for revision in elective lower-limb arthroplasty. This scoping review aims to identify and evaluate all existing and novel assessment methods for metal sensitivity in elective lower-limb arthroplasty. Methods: The Cochrane Central Register of Controlled Trials (CENTRAL), Ovid Medical Literature Analysis and Retrieval System Online (MEDLINE), PubMed, and Google Scholar databases were searched for studies published between January 1, 2000, and September 1, 2023. Studies evaluating one or more metal sensitivity assessment method preoperatively, perioperatively, or postoperatively were included. Studies were grouped based on the assessment methods reported and summarized based on the study design, outcome measure, results, and comments on the method’s validity. Results: A total of 1220 results were screened, with 39 results (15 retrospective cohort studies, 11 prospective cohort studies, 6 case reports, 5 randomized controlled trials, and 2 case control studies) included, identifying 12 assessment methods. The most used one was patch testing, featuring in 17 studies (43.6%). Lymphocyte transformation assay/testing featured in 12 studies (30.8%). Plasma/serum concentration of metal ions featured in 6 studies (15.4%). Patient history and serum cytokine testing featured in 7 (17.9%) and 4 (10.3%) studies each. Generalized serum inflammatory markers featured in 3 studies (7.7%). The remaining 6 methods each featured in one or 2 studies. Evidence of the reliability of most metrics was limited. Conclusions: Several assessment methods were identified. However, evidence of any methods reliably predicting and diagnosing the occurrence of metal sensitivity was limited. There is a need for improved metrics of metal hypersensitivity.