title: Do ion levels in metal-on-metal hip resurfacing differ from those in metal-on-metal THA at long-term followup?
abstract: BACKGROUND
  Metal-on-metal hip resurfacing arthroplasty (MOM HR) has become an established alternative to traditional metal-on-metal total hip arthroplasty (MOM THA) for younger, more active patients. Nevertheless, concerns remain regarding wear and corrosion of the bearing surfaces and the resulting systemic metal ion distribution.
  
  
  OBJECTIVE
  We therefore asked whether (1) serum ion concentrations in patients with MOM HR at the time of long-term followup were higher than concentrations in a control population with no hip implants; (2) the ion concentrations in patients with MOM HR were different from those in patients with MOM THA; and (3) sex would influence ion levels with regard to implant type.
  
  
  METHODS
  The MOM HR and MOM THA groups consisted of 25 patients (evaluated at a minimum of 96 months) and 16 patients (evaluated at a minimum of 106 months), respectively. Forty-eight healthy donors were recruited for reference values. Cobalt, chromium, nickel, and molybdenum were measured by furnace graphite atomic absorption spectrophotometry.
  
  
  RESULTS
  Ion concentrations of cobalt, chromium, and molybdenum in MOM HR were higher than in controls. Chromium and cobalt release were higher in MOM HR than in MOM THA. The sex-based analysis showed the difference was because women had higher concentrations in the MOM HR group than in the MOM THA group, whereas there was no difference between the men in the two groups.
  
  
  CONCLUSIONS
  In MOM HR, high metal ion release persists for the long term. Consequently, it is important to implement strict biomonitoring for patients who have received these implants. The sustained high levels of chromium in females within the MOM HR group are concerning and merits strong consideration when choosing implants in this patient group.
authors.affiliation: Laboratory for Orthopaedic Pathophysiology and Regenerative Medicine, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10, 40136, Bologna, Italy. luciamaria.savarino@ior.it
authors.forename: Lucia
authors.initials: L
authors.lastname: Savarino
authors.forename: Matteo
authors.initials: M
authors.lastname: Cadossi
authors.forename: Eugenio
authors.initials: E
authors.lastname: Chiarello
authors.forename: Nicola
authors.initials: N
authors.lastname: Baldini
authors.forename: Sandro
authors.initials: S
authors.lastname: Giannini
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D002857:Chromium / Q000097:blood*; D003035:Cobalt / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D006621:Hip Joint / Q000601:surgery; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D002857:Chromium; D003035:Cobalt