title: Hydroxyapatite coating does not improve uncemented stem survival after total hip arthroplasty!
abstract: OBJECTIVE
  It is still being debated whether HA coating of uncemented stems used in total hip arthroplasty (THA) improves implant survival. We therefore investigated different uncemented stem brands, with and without HA coating, regarding early and long-term survival.
  
  
  METHODS
  We identified 152,410 THA procedures using uncemented stems that were performed between 1995 and 2011 and registered in the Nordic Arthroplasty Register Association (NARA) database. We excluded 19,446 procedures that used stem brands less than 500 times in each country, procedures performed due to diagnoses other than osteoarthritis or pediatric hip disease, and procedures with missing information on the type of coating. 22 stem brands remained (which were used in 116,069 procedures) for analysis of revision of any component. 79,192 procedures from Denmark, Norway, and Sweden were analyzed for the endpoint stem revision. Unadjusted survival rates were calculated according to Kaplan-Meier, and Cox proportional hazards models were fitted in order to calculate hazard ratios (HRs) for the risk of revision with 95% confidence intervals (CIs).
  
  
  RESULTS
  Unadjusted 10-year survival with the endpoint revision of any component for any reason was 92.1% (CI: 91.8-92.4). Unadjusted 10-year survival with the endpoint stem revision due to aseptic loosening varied between the stem brands investigated and ranged from 96.7% (CI: 94.4-99.0) to 99.9% (CI: 99.6-100). Of the stem brands with the best survival, stems with and without HA coating were found. The presence of HA coating was not associated with statistically significant effects on the adjusted risk of stem revision due to aseptic loosening, with an HR of 0.8 (CI: 0.5-1.3; p = 0.4). The adjusted risk of revision due to infection was similar in the groups of THAs using HA-coated and non-HA-coated stems, with an HR of 0.9 (CI: 0.8-1.1; p = 0.6) for the presence of HA coating. The commonly used Bimetric stem (n = 25,329) was available both with and without HA coating, and the adjusted risk of stem revision due to aseptic loosening was similar for the 2 variants, with an HR of 0.9 (CI: 0.5-1.4; p = 0.5) for the HA-coated Bimetric stem.
  
  
  CONCLUSIONS
  Uncemented HA-coated stems had similar results to those of uncemented stems with porous coating or rough sand-blasted stems. The use of HA coating on stems available both with and without this surface treatment had no clinically relevant effect on their outcome, and we thus question whether HA coating adds any value to well-functioning stem designs.
authors.affiliation: Department of Orthopaedics , Institute of Surgical Sciences, Uppsala University Hospital, Uppsala , Sweden.
authors.forename: Nils P
authors.initials: NP
authors.lastname: Hailer
authors.forename: Stergios
authors.initials: S
authors.lastname: Lazarinis
authors.forename: Keijo T
authors.initials: KT
authors.lastname: Mäkelä
authors.forename: Antti
authors.initials: A
authors.lastname: Eskelinen
authors.forename: Anne M
authors.initials: AM
authors.lastname: Fenstad
authors.forename: Geir
authors.initials: G
authors.lastname: Hallan
authors.forename: Leif
authors.initials: L
authors.lastname: Havelin
authors.forename: Søren
authors.initials: S
authors.lastname: Overgaard
authors.forename: Alma B
authors.initials: AB
authors.lastname: Pedersen
authors.forename: Frank
authors.initials: F
authors.lastname: Mehnert
authors.forename: Johan
authors.initials: J
authors.lastname: Kärrholm
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D002484:Cementation / Q000379:methods*; D020099:Coated Materials, Biocompatible / Q000627:therapeutic use*; D015331:Cohort Studies; D003718:Denmark; D005260:Female; D006618:Hip Dislocation, Congenital / Q000601:surgery; D006801:Humans; D006882:Hydroxyapatites / Q000627:therapeutic use*; D053208:Kaplan-Meier Estimate; D007873:Legg-Calve-Perthes Disease / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009664:Norway; D015207:Osteoarthritis, Hip / Q000601:surgery*; D016016:Proportional Hazards Models; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections; D012042:Registries; D012086:Reoperation / Q000706:statistics & numerical data; D013548:Sweden; D016896:Treatment Outcome
chemical_list: D020099:Coated Materials, Biocompatible; D006882:Hydroxyapatites