title: No association between pseudotumors, high serum metal-ion levels and metal hypersensitivity in large-head metal-on-metal total hip arthroplasty at 5-7-year follow-up.
abstract: OBJECTIVE
  The relationship between metal wear debris, pseudotumor formation and metal hypersensitivity is complex and not completely understood. The purpose of this study was to assess the prevalence of pseudotumor formation in a consecutive series of metal-on-metal (MoM) total hip arthroplasty (THA) and to investigate its relationship to serum metal-ion levels and hypersensitivity to metal.
  
  
  METHODS
  Forty-one patients (31 males), mean age 52 (28-68) years, with a total of 49 large-head MoM THA participated in a 5-7-year follow-up study. Patients underwent ultrasonography, serum metal-ion concentrations were measured, metal allergy and atopic dermatitis were evaluated, and the questionnaires of the Oxford Hip Score (OHS), Harris Hip Score (HHS) and the Short-Form Health Survey (SF-36) were completed.
  
  
  RESULTS
  Pseudotumors were found in eight patients, but they were asymptomatic and their serum metal-ion levels were similar to those observed in patients with no pseudotumors (p > 0.36). The capsule-stem distance of mean 8.6 mm (SD 3.82, 95% CI: 5.40-11.79) was wider (p = 0.02) in patients with pseudotumours than in patients without pseudotumors of mean 5.6 mm (SD 2.89, 95% CI: 4.68-6.58). Positive patch test reactions were seen in three patients. Higher serum metal-ion levels of chromium and cobalt were significantly correlated with steeper cup inclination and smaller femoral head sizes, and were associated with female gender (p < 0.04).
  
  
  CONCLUSIONS
  We found no association between pseudotumor formation, serum metal-ion levels, metal patch test reactivity, and atopic dermatitis. However, clinicians should be aware of asymptomatic pseudotumors, and we advise further exploration into the mechanisms involved in the pathogenesis of pseudotumors.
authors.affiliation: Department of Orthopaedics, Aarhus University Hospital, Tage-Hansens Gade 2, 8000, Aarhus C, Denmark. mettehh20@gmail.com.
authors.forename: Mette Holm
authors.initials: MH
authors.lastname: Hjorth
authors.affiliation: Department of Orthopaedics, Aarhus University Hospital, Tage-Hansens Gade 2, 8000, Aarhus C, Denmark. maiken.stilling@ki.au.dk.
authors.forename: Maiken
authors.initials: M
authors.lastname: Stilling
authors.affiliation: Department of Orthopaedics, Aarhus University Hospital, Tage-Hansens Gade 2, 8000, Aarhus C, Denmark. kjeld@soballe.com.
authors.forename: Kjeld
authors.initials: K
authors.lastname: Soballe
authors.affiliation: Department of Radiology, Aarhus University Hospital, Tage-Hansens Gade 2, 8000, Aarhus C, Denmark. larshans@rm.dk.
authors.forename: Lars Hans
authors.initials: LH
authors.lastname: Bolvig
authors.affiliation: Department of Dermato-Allergology, Gentofte Hospital, University of Copenhagen, Hellerup, Copenhagen, Denmark. jacob.p.thyssen@regionh.dk.
authors.forename: Jacob Pontoppidan
authors.initials: JP
authors.lastname: Thyssen
authors.affiliation: Department of Orthopaedics, Aarhus University Hospital, Tage-Hansens Gade 2, 8000, Aarhus C, Denmark. inger.mechlenburg@ki.au.dk.
authors.forename: Inger
authors.initials: I
authors.lastname: Mechlenburg
authors.affiliation: Department of Orthopaedics, Aarhus University Hospital, Tage-Hansens Gade 2, 8000, Aarhus C, Denmark. stig.jakobsen@ki.au.dk.
authors.forename: Stig Storgaard
authors.initials: SS
authors.lastname: Jakobsen
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation / Q000706:statistics & numerical data; D015984:Causality; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006104:Granuloma, Plasma Cell / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology*; D006622:Hip Prosthesis / Q000706:statistics & numerical data*; D006801:Humans; D006967:Hypersensitivity / Q000097:blood* / Q000453:epidemiology*; D007477:Ions / Q000097:blood; D008137:Longitudinal Studies; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000706:statistics & numerical data*; D008670:Metals / Q000097:blood*; D008875:Middle Aged; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity
chemical_list: D007477:Ions; D008670:Metals
keywords: Large-head MoM THA; Metal hypersensitivity; Pseudotumor; Serum metal-ion levels; Ultrasonography