title: The value of serial metal ion levels in following up patients with metal-on-metal hip arthroplasty.
abstract: BACKGROUND
  The sensitivity of cobalt (Co) and chromium (Cr) ion-levels in detecting poorly performing metal-on-metal hip implants is low. This study proposes that serial changes in ion-levels are a more accurate marker of arthroplasties at risk.
  
  
  METHODS
  Serial metal ion-levels and implant data of 285 patients with ASR resurfacing or replacement were studied. Patient and implant characteristics were analysed using univariate and multivariate analyses.
  
  
  RESULTS
  111 (39%) had revision surgery. Time since index surgery (p<0.001), acetabular inclination (p<0.001), their interaction (p<0.001) and femoral head size (p = 0.01) were significant variables. Head size (≤51 mm) had lower Co and Cr levels (p = 0.01). Cr/Co showed marginal decrease over time in the unrevised group and no decrease prerevision.
  
  
  CONCLUSIONS
  Repeated measurement of ion-levels were higher in the revision group suggesting that serial measurements rather than absolute values may have a role to play in predicting implant failure.
authors.affiliation: Lourdes Orthopaedic Hospital, Kilcreene, Kilkenny - Ireland.
authors.forename: Gavin
authors.initials: G
authors.lastname: McHugh
authors.affiliation: Lourdes Orthopaedic Hospital, Kilcreene, Kilkenny - Ireland.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Merchant
authors.affiliation: School of Mathematical Sciences, University College Dublin, Dublin - Ireland.
authors.forename: Gabrielle E
authors.initials: GE
authors.lastname: Kelly
authors.affiliation: Lourdes Orthopaedic Hospital, Kilcreene, Kilkenny - Ireland.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Bergin
authors.affiliation: Lourdes Orthopaedic Hospital, Kilcreene, Kilkenny - Ireland.
authors.forename: Gerald F
authors.initials: GF
authors.lastname: McCoy
authors.affiliation: Lourdes Orthopaedic Hospital, Kilcreene, Kilkenny - Ireland.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Wozniak
authors.affiliation: Lourdes Orthopaedic Hospital, Kilcreene, Kilkenny - Ireland.
authors.forename: John F
authors.initials: JF
authors.lastname: Quinlan
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D015415:Biomarkers; D002857:Chromium / Q000097:blood; D003035:Cobalt / Q000097:blood; D016208:Databases, Factual; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D061825:Metal-on-Metal Joint Prostheses; D008875:Middle Aged; D015999:Multivariate Analysis; D015207:Osteoarthritis, Hip / Q000097:blood* / Q000000981:diagnostic imaging / Q000601:surgery*; D011237:Predictive Value of Tests; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation / Q000379:methods; D012189:Retrospective Studies; D018570:Risk Assessment; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D002857:Chromium; D003035:Cobalt