title: Characterization of metal-wear nanoparticles in pseudotumor following metal-on-metal hip resurfacing.
abstract: Biopsies from a typical case of pseudotumor following metal-on-metal hip resurfacing (MoMHR) were analyzed using light and transmission electron microscopy, backscatter scanning electron microscopy and energy dispersive x-ray spectrometry (EDS). Heavy macrophage infiltration was observed in all black pigmented specimens. Metal nanoparticles (NPs) were observed exclusively within phagosomes of living macrophages and fragments of dead macrophages. Although dead fibroblasts were found to be juxtaposed with dead and disintegrated macrophages, the NPs were not seen within either live or dead fibroblasts. Chromium (Cr) but not cobalt (Co) was the predominant component of the remaining wear NPs in tissue. The current study finding suggests that corrosion of Co in phagosomes of macrophages and resultant Co ion release lead to tissue necrosis and adverse soft tissue reactions (pseudotumors). Further studies are required to elucidate the precise mechanism of intracellular corrosion of metal NPs and the long-term toxicity of the Cr remaining in the peri-prosthetic tissues.
  
  
  BACKGROUND
  In this study of metal-on-metal hip resurfacing-related tissue necrosis and pseudotumor formation, corrosion and decomposition of metallic cobalt in phagosomes of macrophages and resultant cobalt ion release were demonstrated to be the key elements of pathogenesis.
authors.affiliation: Centre for Nanohealth, School of Medicine, Swansea University, Singleton Park, Swansea, United Kingdom. z.xia@swansea.ac.uk
authors.forename: Zhidao
authors.initials: Z
authors.lastname: Xia
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Kwon
authors.forename: Shahid
authors.initials: S
authors.lastname: Mehmood
authors.forename: Clive
authors.initials: C
authors.lastname: Downing
authors.forename: Kerstin
authors.initials: K
authors.lastname: Jurkschat
authors.forename: David W
authors.initials: DW
authors.lastname: Murray
mesh_terms: D000328:Adult; D002857:Chromium / Q000009:adverse effects*; D003035:Cobalt / Q000009:adverse effects*; D003343:Corrosion; D005260:Female; D006615:Hip / Q000473:pathology* / Q000601:surgery*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000473:pathology; D053768:Metal Nanoparticles / Q000009:adverse effects*; D010587:Phagocytosis; D011475:Prosthesis Failure
chemical_list: D002857:Chromium; D003035:Cobalt