title: Aspirin versus low-molecular-weight heparin for extended venous thromboembolism prophylaxis after total hip arthroplasty: a randomized trial.
abstract: BACKGROUND
  The role of aspirin in thromboprophylaxis after total hip arthroplasty (THA) is controversial.
  
  
  OBJECTIVE
  To compare extended prophylaxis with aspirin and dalteparin for prevention of symptomatic venous thromboembolism (VTE) after THA.
  
  
  METHODS
  Multicenter randomized, controlled trial with a noninferiority design based on a minimal clinically important difference of 2.0%. Randomization was electronically generated; patients were assigned to a treatment group through a Web-based program. Patients, physicians, study coordinators, health care team members, outcome adjudicators, and data analysts were blinded to interventions. (Current Controlled Trials: ISRCTN11902170).
  
  
  METHODS
  12 tertiary care orthopedic referral centers in Canada.
  
  
  METHODS
  778 patients who had elective unilateral THA between 2007 and 2010.
  
  
  METHODS
  After an initial 10 days of dalteparin prophylaxis after elective THA, patients were randomly assigned to 28 days of dalteparin (n = 400) or aspirin (n = 386).
  
  
  METHODS
  Symptomatic VTE confirmed by objective testing (primary efficacy outcome) and bleeding.
  
  
  RESULTS
  Five of 398 patients (1.3%) randomly assigned to dalteparin and 1 of 380 (0.3%) randomly assigned to aspirin had VTE (absolute difference, 1.0 percentage point [95% CI, -0.5 to 2.5 percentage points]). Aspirin was noninferior (P < 0.001) but not superior (P = 0.22) to dalteparin. Clinically significant bleeding occurred in 5 patients (1.3%) receiving dalteparin and 2 (0.5%) receiving aspirin. The absolute between-group difference in a composite of all VTE and clinically significant bleeding events was 1.7 percentage points (CI, -0.3 to 3.8 percentage points; P = 0.091) in favor of aspirin.
  
  
  CONCLUSIONS
  The study was halted prematurely because of difficulty with patient recruitment.
  
  
  CONCLUSIONS
  Extended prophylaxis for 28 days with aspirin was noninferior to and as safe as dalteparin for the prevention of VTE after THA in patients who initially received dalteparin for 10 days. Given its low cost and greater convenience, aspirin may be considered a reasonable alternative for extended thromboprophylaxis after THA.
  
  
  BACKGROUND
  Canadian Institutes of Health Research.
authors.affiliation: Dalhousie University, Halifax, Nova Scotia, Canada. david.anderson@cdha.nshealth.ca
authors.forename: David R
authors.initials: DR
authors.lastname: Anderson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dunbar
authors.forename: Eric R
authors.initials: ER
authors.lastname: Bohm
authors.forename: Etienne
authors.initials: E
authors.lastname: Belzile
authors.forename: Susan R
authors.initials: SR
authors.lastname: Kahn
authors.forename: David
authors.initials: D
authors.lastname: Zukor
authors.forename: William
authors.initials: W
authors.lastname: Fisher
authors.forename: Wade
authors.initials: W
authors.lastname: Gofton
authors.forename: Peter
authors.initials: P
authors.lastname: Gross
authors.forename: Stephane
authors.initials: S
authors.lastname: Pelet
authors.forename: Mark
authors.initials: M
authors.lastname: Crowther
authors.forename: Steven
authors.initials: S
authors.lastname: MacDonald
authors.forename: Paul
authors.initials: P
authors.lastname: Kim
authors.forename: Susan
authors.initials: S
authors.lastname: Pleasance
authors.forename: Nicki
authors.initials: N
authors.lastname: Davis
authors.forename: Pantelis
authors.initials: P
authors.lastname: Andreou
authors.forename: Philip
authors.initials: P
authors.lastname: Wells
authors.forename: Michael
authors.initials: M
authors.lastname: Kovacs
authors.forename: Marc A
authors.initials: MA
authors.lastname: Rodger
authors.forename: Tim
authors.initials: T
authors.lastname: Ramsay
authors.forename: Marc
authors.initials: M
authors.lastname: Carrier
authors.forename: Pascal-Andre
authors.initials: PA
authors.lastname: Vendittoli
mesh_terms: D000328:Adult; D000925:Anticoagulants / Q000009:adverse effects / Q000627:therapeutic use*; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D001241:Aspirin / Q000009:adverse effects / Q000627:therapeutic use*; D017985:Dalteparin / Q000009:adverse effects / Q000627:therapeutic use*; D004334:Drug Administration Schedule; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D010975:Platelet Aggregation Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D054556:Venous Thromboembolism / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants; D010975:Platelet Aggregation Inhibitors; D001241:Aspirin; D017985:Dalteparin