title: Delineating the impact of obesity and its relationship on recovery after total joint arthroplasties.
abstract: OBJECTIVE
  The primary aim of this study was to determine the impact of obesity in predicting short and long-term pain relief and functional recovery in total joint arthroplasty (TJA) either as an independent risk factor or a factor mediated by two chronic conditions associated with obesity-cardiac disease and diabetes mellitus.
  
  
  METHODS
  A prospective observational study of 520 patients with primary joint arthroplasties. Pain and functional outcomes were evaluated with the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index within a month of surgery and then 6 months and 3 years post-operatively. Obesity, cardiac disease and diabetes mellitus were examined as potential risk factors for poor recovery. Patients were classified into four groups based on body mass index (BMI): (normal<25.0 kg/m(2); overweight 25.0-29.9 kg/m(2); obese Class 1 30.0-34.9 kg/m(2); severe obese Class 2&3 35.0 ≥ kg/m(2)). Linear mixed models for each joint type (hip and knee arthroplasty) were developed to examine the pattern of recovery and the effect of obesity.
  
  
  RESULTS
  Ninety-nine (19%) patients were severely obese, 127 (24%) had cardiac disease and 58 (11%) had diabetes mellitus. Baseline pain and functional scores were similar regardless of BMI classification. Severe obesity was a significant risk factor for worse pain and functional recovery at 6 months but no longer at 3 years following total hip and knee arthroplasty. Cardiac disease predicted a slower recovery after hip arthroplasty. No significant interactions existed between obesity and cardiac disease or diabetes mellitus.
  
  
  CONCLUSIONS
  Severe obesity is an independent risk factor for slow recovery over 3 years for both hip and knee arthroplasties.
authors.affiliation: School of Public Health, University of Alberta, Edmonton, AB, Canada T6G 2G4. cajones@ualberta.ca
authors.forename: C A
authors.initials: CA
authors.lastname: Jones
authors.forename: V
authors.initials: V
authors.lastname: Cox
authors.forename: G S
authors.initials: GS
authors.lastname: Jhangri
authors.forename: M E
authors.initials: ME
authors.lastname: Suarez-Almazor
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000534:rehabilitation*; D019645:Arthroplasty, Replacement, Knee / Q000534:rehabilitation*; D015992:Body Mass Index; D048909:Diabetes Complications; D005260:Female; D006331:Heart Diseases / Q000150:complications; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D015207:Osteoarthritis, Hip / Q000150:complications / Q000601:surgery; D020370:Osteoarthritis, Knee / Q000150:complications / Q000601:surgery; D010147:Pain Measurement / Q000379:methods; D010149:Postoperative Pain / Q000209:etiology; D011379:Prognosis; D011446:Prospective Studies; D020127:Recovery of Function; D012307:Risk Factors; D016896:Treatment Outcome