title: The Nordic Arthroplasty Register Association: a unique collaboration between 3 national hip arthroplasty registries with 280,201 THRs.
abstract: OBJECTIVE
  The possibility of comparing results and of pooling the data has been limited for the Nordic arthroplasty registries, because of different registration systems and questionnaires. We have established a common Nordic database, in order to compare demographics and the results of total hip replacement surgery between countries. In addition, we plan to study results in patient groups in which the numbers are too small to be studied in the individual countries.
  
  
  METHODS
  Primary total hip replacements (THRs) from 1995-2006 were selected for the study. Denmark, Sweden, and Norway contributed data. A common code set was made and Cox multiple regression, with adjustment for age, sex, and diagnosis was used to calculate prosthesis survival with any revision as endpoint.
  
  
  RESULTS
  280,201 operations were included (69,242 from Denmark, 140,821 from Sweden, and 70,138 from Norway). Females accounted for 60% of the patients in Denmark and Sweden, and 70% in Norway. Childhood disease was the cause of 3.1%, 1.8%, and 8.7% of the operations in Denmark, Sweden, and Norway, respectively. Resurfacing of hips accounted for 0.5% or less in all countries. The posterior approach was used in 91% of cases in Denmark, 60% in Sweden, and 24% in Norway. Cemented THRs were used in 46% of patients in Denmark, in 89% of patients in Sweden, and in 79% of patients in Norway. Of the 280,201 primary THRs, 9,596 (3.4%) had been revised. 10-year survival was 92% (95% CI: 91.6-92.4) in Denmark, 94% (95% CI: 93.6-94.1) in Sweden, and 93% (95% CI: 92.3-93.0) in Norway. In Denmark, 34% of the revisions were due to dislocation, as compared to 23% in Sweden and Norway. Replacement of only cup or liner constituted 44% of the revisions in Denmark, 29% in Sweden, and 33% in Norway.
  
  
  CONCLUSIONS
  This unique common Nordic collaboration has shown differences between the countries concerning demographics, prosthesis fixation, and survival. The large number of patients in this database significantly widens our horizons for future research.
authors.affiliation: The Norwegian Arthroplasty Register, Department of Orthopaedic Surgery, Haukeland University Hospital, Bergen, Norway. leif.havelin@helse-bergen.no
authors.forename: Leif I
authors.initials: LI
authors.lastname: Havelin
authors.forename: Anne M
authors.initials: AM
authors.lastname: Fenstad
authors.forename: Roger
authors.initials: R
authors.lastname: Salomonsson
authors.forename: Frank
authors.initials: F
authors.lastname: Mehnert
authors.forename: Ove
authors.initials: O
authors.lastname: Furnes
authors.forename: Søren
authors.initials: S
authors.lastname: Overgaard
authors.forename: Alma B
authors.initials: AB
authors.lastname: Pedersen
authors.forename: Peter
authors.initials: P
authors.lastname: Herberts
authors.forename: Johan
authors.initials: J
authors.lastname: Kärrholm
authors.forename: Göran
authors.initials: G
authors.lastname: Garellick
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000592:standards*; D002648:Child; D016208:Databases, Factual; D003718:Denmark; D005260:Female; D005271:Femur Head Necrosis / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D009664:Norway; D015207:Osteoarthritis, Hip / Q000601:surgery; D017063:Outcome Assessment, Health Care; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation; D013548:Sweden; D055815:Young Adult