title: Periprosthetic femoral fracture within two years after total hip replacement: analysis of 437,629 operations in the nordic arthroplasty register association database.
abstract: BACKGROUND
  We used the Nordic Arthroplasty Register Association database to evaluate whether age, sex, preoperative diagnosis, fixation, and implant design influence the risk of revision arthroplasty due to periprosthetic fracture within two years from operation of a primary total hip replacement.
  
  
  METHODS
  Included in the study were 325,730 cemented femoral stems and 111,899 uncemented femoral stems inserted from 1995 to 2009. Seven frequently used stems (two cemented stems [Exeter and Lubinus SP II] and five uncemented stems [Bi-Metric, Corail, CLS Spotorno, ABG I, and ABG II]) were specifically studied.
  
  
  RESULTS
  The incidence of revision at two years was low: 0.47% for uncemented stems and 0.07% for cemented stems. Uncemented stems were much more likely to have this complication (relative risk, 8.72 [95% confidence interval, 7.37 to 10.32]; p < 0.0005). Age had no consistent influence on the risk for revision of cemented stems, but revision in the uncemented group increased with increasing age. A cemented stem was associated with a higher risk in male patients compared with female patients (hazard ratio, 1.95 [95% confidence interval, 1.51 to 2.53]; p < 0.0005), whereas an uncemented stem was associated with a reduced risk in male patients compared with female patients (hazard ratio, 0.74 [95% confidence interval, 0.62 to 0.89]; p = 0.001). The risk for revision due to early periprosthetic fracture increased during the 2003 to 2009 period compared with the 1995 to 2002 period both before and after adjustment for demographic factors and fixation (relative risk, 1.44 [95% confidence interval, 1.18 to 1.69]; p < 0.0005). The hazard ratio for the Exeter stem was about five times higher than that for the Lubinus SP II stem (hazard ratio, 5.03 [95% confidence interval, 3.29 to 7.70]; p < 0.0005). Of the five uncemented stems, the ABG II stem showed an increased hazard ratio of 1.63 (95% confidence interval, 1.16 to 2.28) (p = 0.005), whereas the Corail stem showed a decreased hazard ratio of 0.47 (95% confidence interval, 0.34 to 0.65) (p < 0.0005) compared with the reference Bi-Metric design.
  
  
  CONCLUSIONS
  The shape and surface finish of the femoral stem and its fixation could be related to the increased risk of some prosthetic designs. Even if the incidence of early periprosthetic fracture in general is low and other reasons for revision must be considered, specific attention should be given to the choice of fixation and stem design in risk groups.
  
  
  METHODS
  Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Institute of Clinical Sciences, The Sahlgrenska Academy, University of Göteborg, Box 426, 40530 Göteborg, Sweden. E-mail address for T.M. Thien: truike.thien@capio.se.
authors.forename: Truike M
authors.initials: TM
authors.lastname: Thien
authors.affiliation: Institute of Clinical Sciences, The Sahlgrenska Academy, University of Göteborg, Box 426, 40530 Göteborg, Sweden. E-mail address for T.M. Thien: truike.thien@capio.se.
authors.forename: Georgios
authors.initials: G
authors.lastname: Chatziagorou
authors.affiliation: Institute of Clinical Sciences, The Sahlgrenska Academy, University of Göteborg, Box 426, 40530 Göteborg, Sweden. E-mail address for T.M. Thien: truike.thien@capio.se.
authors.forename: Göran
authors.initials: G
authors.lastname: Garellick
authors.affiliation: The Norwegian Arthroplasty Register, Department of Clinical Medicine, University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway. E-mail address for O. Furnes: ove-furnes@helse-bergen.no. E-mail address for L.I. Havelin: leif.havelin@helse-bergen.no.
authors.forename: Ove
authors.initials: O
authors.lastname: Furnes
authors.affiliation: The Norwegian Arthroplasty Register, Department of Clinical Medicine, University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway. E-mail address for O. Furnes: ove-furnes@helse-bergen.no. E-mail address for L.I. Havelin: leif.havelin@helse-bergen.no.
authors.forename: Leif I
authors.initials: LI
authors.lastname: Havelin
authors.affiliation: Department of Orthopaedics and Traumatology, Turku University Hospital, P.O. Box 52, 20521 Turku, Finland. E-mail address: keijo.makela@tyks.fi.
authors.forename: Keijo
authors.initials: K
authors.lastname: Mäkelä
authors.affiliation: Institute of Clinical Research, University of Southern Denmark, Sdr. Boulevard 29, 5000 Odense, Denmark. E-mail address: soeren.overgaard@ouh.regionsyddanmark.dk.
authors.forename: Søren
authors.initials: S
authors.lastname: Overgaard
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Alle 43-45, 8200 Aarhus, Denmark. E-mail address: abp@dce.au.dk.
authors.forename: Alma
authors.initials: A
authors.lastname: Pedersen
authors.affiliation: The Coxa Hospital for Joint Replacement, Box 652, 33101 Tampere, Finland. E-mail address: antii.eskelinen@coxa.fi.
authors.forename: Antti
authors.initials: A
authors.lastname: Eskelinen
authors.affiliation: Department of Public Health, University of Helsinki, Box 41, 00014 Helsinki, Finland. E-mail address: pekka.pulkkinen@tyks.fi.
authors.forename: Pekka
authors.initials: P
authors.lastname: Pulkkinen
authors.affiliation: Institute of Clinical Sciences, The Sahlgrenska Academy, University of Göteborg, Box 426, 40530 Göteborg, Sweden. E-mail address for T.M. Thien: truike.thien@capio.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Kärrholm
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D016208:Databases, Factual; D005260:Female; D005264:Femoral Fractures / Q000209:etiology*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D057068:Periprosthetic Fractures / Q000601:surgery; D011183:Postoperative Complications; D011474:Prosthesis Design; D012042:Registries; D012086:Reoperation