title: Repeated metal ion measurements in patients with high risk metal-on-metal hip replacement.
abstract: OBJECTIVE
  Conventional follow-up methods are not sufficient to identify adverse soft tissue reactions in patients with metal-on-metal hip replacements. The national guidelines regarding metal ion measurements are debatable. The aims of our study were to investigate (1) if there is a clinically significant change in whole blood (WB) cobalt (Co) or chrome (Cr) levels in repeated WB assessment in patients operated on with ASR hip replacements, and (2) what proportion of patients has WB Co or Cr level below the previously established safe upper limits (SUL) in the repeated WB metal ion assessment.
  
  
  METHODS
  We identified all patients (n = 254) with unilateral ASR implants who had second blood sample taken eight to 16 months after the first.
  
  
  RESULTS
  WB Co and Cr levels remained below SUL and within their initial values during a mean one-year measurement interval in the majority of patients with a high risk HR device. In contrast to this, 50 % of patients with THRs had metal ion levels exceeding the SUL in the first measurement. WB Co values significantly increased over the measurement interval in the THR group.
  
  
  CONCLUSIONS
  In patients with a high risk HR, repeated metal ion measurement did not provide useful information for clinical decision-making. In patients with a LD MoM THR repeated measurements revealed a large number of patients with metal ion levels exceeding SUL and might thus be clinically beneficial.
authors.affiliation: Coxa Hospital for Joint Replacement, P.O. Box 652, 33101, Tampere, Finland, aleksi.reito@uta.fi.
authors.forename: Aleksi
authors.initials: A
authors.lastname: Reito
authors.forename: Teemu
authors.initials: T
authors.lastname: Moilanen
authors.forename: Timo
authors.initials: T
authors.lastname: Puolakka
authors.forename: Jorma
authors.initials: J
authors.lastname: Pajamäki
authors.forename: Antti
authors.initials: A
authors.lastname: Eskelinen
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D002857:Chromium / Q000097:blood; D003035:Cobalt / Q000097:blood*; D005260:Female; D006621:Hip Joint / Q000601:surgery; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D007477:Ions / Q000097:blood; D008297:Male; D019216:Metals, Heavy / Q000097:blood*; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000097:blood / Q000601:surgery; D011474:Prosthesis Design; D011475:Prosthesis Failure
chemical_list: D007477:Ions; D019216:Metals, Heavy; D002857:Chromium; D003035:Cobalt