title: Metal release and metal allergy after total hip replacement with resurfacing versus conventional hybrid prosthesis.
abstract: BACKGROUND
  Metal-on-metal (MOM) total hip arthroplasties were reintroduced because of the problems with osteolysis and aseptic loosening related to polyethylene wear of early metal-on-polyethylene (MOP) arthroplasties. The volumetric wear rate has been greatly reduced with MOM arthroplasties; however, because of nano-size wear particles, the absolute number has been greatly increased. Thus, a source of metal ion exposure with the potential to sensitize patients is present. We hypothesized that higher amounts of wear particles result in increased release of metal ions and ultimately lead to an increased incidence of metal allergy.
  
  
  METHODS
  52 hips in 52 patients (median age 60 (51-64) years, 30 women) were randomized to either a MOM hip resurfacing system (ReCap) or a standard MOP total hip arthoplasty (Mallory Head/Exeter). Spot urine samples were collected preoperatively, postoperatively, after 3 months, and after 1, 2, and 5 years and tested with inductively coupled plasma-sector field mass spectrometry. After 5 years, hypersensitivity to metals was evaluated by patch testing and lymphocyte transformation assay. In addition, the patients answered a questionnaire about hypersensitivity.
  
  
  RESULTS
  A statistically significant 10- to 20-fold increase in urinary levels of cobalt and chromium was observed throughout the entire follow-up in the MOM group. The prevalence of metal allergy was similar between groups.
  
  
  CONCLUSIONS
  While we observed significantly increased levels of metal ions in the urine during the entire follow-up period, no difference in prevalence of metal allergy was observed in the MOM group. However, the effect of long-term metal exposure remains uncertain.
authors.affiliation: Department of Orthopaedics , Aarhus University Hospital.
authors.forename: Klas
authors.initials: K
authors.lastname: Gustafson
authors.forename: Stig S
authors.initials: SS
authors.lastname: Jakobsen
authors.forename: Nina D
authors.initials: ND
authors.lastname: Lorenzen
authors.forename: Jacob P
authors.initials: JP
authors.lastname: Thyssen
authors.forename: Jeanne D
authors.initials: JD
authors.lastname: Johansen
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: Bonefeld
authors.forename: Maiken
authors.initials: M
authors.lastname: Stilling
authors.forename: Thomas
authors.initials: T
authors.lastname: Baad-Hansen
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D002857:Chromium / Q000009:adverse effects / Q000652:urine; D003035:Cobalt / Q000009:adverse effects / Q000652:urine; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D006967:Hypersensitivity / Q000209:etiology*; D008213:Lymphocyte Activation; D008297:Male; D008670:Metals / Q000009:adverse effects* / Q000652:urine; D008875:Middle Aged; D053758:Nanoparticles / Q000009:adverse effects; D010014:Osteolysis / Q000209:etiology; D010328:Patch Tests; D020959:Polyethylene / Q000009:adverse effects; D011475:Prosthesis Failure / Q000009:adverse effects* / Q000209:etiology; D011795:Surveys and Questionnaires; D014025:Titanium / Q000009:adverse effects / Q000652:urine
chemical_list: D008670:Metals; D002857:Chromium; D003035:Cobalt; D020959:Polyethylene; D014025:Titanium