title: Effect of hydroxyapatite coating on risk of revision after primary total hip arthroplasty in younger patients: findings from the Danish Hip Arthroplasty Registry.
abstract: BACKGROUND
  The effect of hydroxyapatite (HA) on implant survival in the medium and long term is uncertain. We studied the effect of HA coating of uncemented implants on the risk of cup and stem revision in primary total hip arthroplasty (THA).
  
  
  METHODS
  Using the Danish Hip Arthroplasty Registry (DHR), we identified patients less than 70 years old who had undergone uncemented primary THA during 1997-2005. 4,125 HA-coated and 7,737 non-HA-coated cups and 3,158 HA-coated and 4,749 non-HA-coated stems were available for analysis. The mean follow-up time was 3.4 years for cups and 3.2 years for stems. We estimated the relative risk (RR) of revision due to aseptic loosening or any cause, and adjusted for possible confounders (age, sex, fixation of opposite implant part, and diagnosis for primary THA) using multivariate Cox regression analysis.
  
  
  RESULTS
  The adjusted RRs for revision of HA-coated cups and stems due to aseptic loosening were 0.89 (95%CI: 0.37-2.2) and 0.71 (95%CI: 0.27-1.9) with up to 9 years of follow-up, compared to non-HA-coated implants. When taking all causes of revision into consideration, the risk estimates were 0.85 (95%CI: 0.68-1.1) and 0.81 (95%CI: 0.61-1.1) for HA-coated cups and stems, respectively.
  
  
  CONCLUSIONS
  In this medium-term follow-up study, the use of HA-coated implants was not associated with any clearly reduced overall risk of revision compared to non-HA-coated implants.
authors.affiliation: Department of Orthopaedic Surgery, Odense University Hospital, University of Southern Denmark, Denmark. akselpaulsen@gmail.com
authors.forename: Aksel
authors.initials: A
authors.lastname: Paulsen
authors.forename: Alma B
authors.initials: AB
authors.lastname: Pedersen
authors.forename: Søren P
authors.initials: SP
authors.lastname: Johnsen
authors.forename: Anders
authors.initials: A
authors.lastname: Riis
authors.forename: Ulf
authors.initials: U
authors.lastname: Lucht
authors.forename: Søren
authors.initials: S
authors.lastname: Overgaard
mesh_terms: D000328:Adult; D000367:Age Factors; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods; D020099:Coated Materials, Biocompatible; D003718:Denmark; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D006882:Hydroxyapatites; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation; D012307:Risk Factors
chemical_list: D020099:Coated Materials, Biocompatible; D006882:Hydroxyapatites