title: Effect of Body Mass Index on Complications and Reoperations After Total Hip Arthroplasty.
abstract: BACKGROUND
  High body mass index (BMI) is associated with increased rates of complications after total hip arthroplasty. Studies to date have evaluated risk mainly as a dichotomous variable according to BMI thresholds. The purpose of this paper was to characterize the risk of complications and implant survival according to BMI as a continuous variable.
  
  
  METHODS
  Using prospectively collected data from our institutional total joint registry, we analyzed 21,361 consecutive hips (17,774 patients) treated with primary total hip arthroplasty between 1985 and 2012 at a single institution. The average BMI at the time of surgery was 28.7 kg/m(2) (range, 15 to 69 kg/m(2)). Estimates of revision surgery and common complications associated with BMI were analyzed using the Kaplan-Meier method of assessing survivorship, with associations of outcomes assessed using a Cox model.
  
  
  RESULTS
  Utilizing smoothing spline parameterization, we found that reoperation (p < 0.001) and implant revision or removal rates (p = 0.002) increased with increasing BMI. Increasing BMI was associated with increased rates of early hip dislocation (p = 0.02), wound infection, and, most strikingly, deep periprosthetic infection (a hazard ratio of 1.09 per unit of BMI >25 kg/m(2); p < 0.001). However, we found no association between increasing BMI and any revision for mechanical failure of the implant or between increasing BMI and revision for aseptic implant loosening. There was an inverse correlation between increasing BMI and risk of revision for bearing wear.
  
  
  CONCLUSIONS
  The rates of reoperation, implant revision or removal, and common complications after total hip arthroplasty were strongly associated with BMI.
authors: Departments of Orthopedic Surgery (E.R.W., A.F.K., and D.J.B.) and Biostatistics and Health Sciences Research (K.F. and W.S.H.), Mayo Clinic, Rochester, Minnesota wagner.eric@mayo.edu.
authors: Eric R
authors: ER
authors: Wagner
authors: Departments of Orthopedic Surgery (E.R.W., A.F.K., and D.J.B.) and Biostatistics and Health Sciences Research (K.F. and W.S.H.), Mayo Clinic, Rochester, Minnesota akamath@post.harvard.edu.
authors: Atul F
authors: AF
authors: Kamath
authors: Departments of Orthopedic Surgery (E.R.W., A.F.K., and D.J.B.) and Biostatistics and Health Sciences Research (K.F. and W.S.H.), Mayo Clinic, Rochester, Minnesota fruth.kristin@mayo.edu.
authors: Kristin M
authors: KM
authors: Fruth
authors: Departments of Orthopedic Surgery (E.R.W., A.F.K., and D.J.B.) and Biostatistics and Health Sciences Research (K.F. and W.S.H.), Mayo Clinic, Rochester, Minnesota harmsen.william@mayo.edu.
authors: William S
authors: WS
authors: Harmsen
authors: Departments of Orthopedic Surgery (E.R.W., A.F.K., and D.J.B.) and Biostatistics and Health Sciences Research (K.F. and W.S.H.), Mayo Clinic, Rochester, Minnesota berry.daniel@mayo.edu.
authors: Daniel J
authors: DJ
authors: Berry
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D015992:Body Mass Index; D020878:Device Removal; D005260:Female; D006617:Hip Dislocation / Q000209:etiology; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D015207:Osteoarthritis, Hip / Q000601:surgery; D011183:Postoperative Complications; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections; D012086:Reoperation