Koper, Maarten C.Maarten C.KoperMathijssen, Nina M. C.Nina M. C.MathijssenVan Ravenswaay Claasen, H. H.H. H.Van Ravenswaay ClaasenWitt, FlorianFlorianWittVehmeijer, Stephan B. W.Stephan B. W.VehmeijerMorlock, MichaelMichaelMorlock2024-03-112024-03-112014-03-12JBJS Case Connector 4 (1): e25 (2014)https://hdl.handle.net/11420/46341Multiple studies have been published on high revision rates for metal-on-metal (MoM) total hip arthroplasty as a result of early failures and pseudotumor formation1–4. The use of MoM articulations has decreased dramatically, and other hard-on-hard bearings have been promoted. The pathogenesis of pseudotumor formation is unknown, although this adverse local tissue reaction has demonstrated histologic features thought to reflect a hypersensitivity response (metallosis) to cobalt and/or chromium particles1,5–8. High serum levels of these metals are positively correlated with the angle of inclination of the acetabular component, presumably due to the resultant edge loading and high wear9–12. We report a case of massive pseudotumor formation in a patient who had undergone bilateral ceramic-on-metal (CoM) total hip arthroplasty. The patient was informed that data concerning the case would be submitted for publication, and she provided consent.en2160-325120141Medicine, HealthEngineeringJournal Article10.2106/JBJS.CC.M.00209Journal Article