title: Morbid obesity: a significant risk factor for failure of two-stage revision total knee arthroplasty for infection.
abstract: BACKGROUND
  Obese patients have a higher risk of complications following primary total knee arthroplasty, including periprosthetic joint infection. However, there is a paucity of data concerning the efficacy of two-stage revision arthroplasty in obese patients.
  
  
  METHODS
  We performed a two-to-one matched cohort study to compare the outcomes of thirty-seven morbidly obese patients (those with a body mass index of ≥ 40 kg/m(2)) who underwent two-stage revision total knee arthroplasty for periprosthetic joint infection following primary total knee arthroplasty with the outcomes of seventy-four non-obese patients (those with a body mass index of <30 kg/m(2)). Groups were matched by sex, age, and date of reimplantation. Outcomes included subsequent revision, reinfection, reoperation, and Knee Society pain and function scores. The minimum follow-up time was five years.
  
  
  RESULTS
  Morbidly obese patients had a significantly increased risk for revision surgery (32% compared with 11%; p < 0.01), reinfection (22% compared with 4%; p < 0.01), and reoperation (51% compared with 16%; p < 0.01). Implant survival rates were 80% for the morbidly obese group and 97% for the non-obese group at five years and 55% for the morbidly obese group and 82% for the non-obese group at ten years. Knee Society pain scores improved significantly following surgery in both groups; the mean scores (and standard deviation) were 50 ± 5 points for the morbidly obese group and 55 ± 2 points for the non-obese group (p = 0.06) preoperatively, 74 ± 5 points for the morbidly obese group and 89 ± 2 points for the non-obese group (p < 0.0001) at two years, 72 ± 6 points for the morbidly obese group and 88 ± 3 points for the non-obese group (p < 0.0001) at five years, and 56 ± 9 points for the morbidly obese group and 84 ± 3 points for the non-obese group (p = 0.01) at ten years.
  
  
  CONCLUSIONS
  Morbid obesity significantly increased the risk of subsequent revision, reoperation, and reinfection following two-stage revision total knee arthroplasty for infection. In addition, these patients had worse pain relief and overall function at intermediate-term clinical follow-up. Although two-stage revision should remain a standard treatment for chronic periprosthetic joint infection in morbidly obese patients, increased failure rates and poorer outcomes should be anticipated.
authors.affiliation: Departments of Orthopedic Surgery (C.D.W., E.R.W., M.T.H., A.D.H., D.G.L., and T.M.M.) and Internal Medicine, Division of Infectious Diseases (D.R.O.), Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address for T.M. Mabry: mabry.tad@mayo.edu.
authors.forename: Chad D
authors.initials: CD
authors.lastname: Watts
authors.affiliation: Departments of Orthopedic Surgery (C.D.W., E.R.W., M.T.H., A.D.H., D.G.L., and T.M.M.) and Internal Medicine, Division of Infectious Diseases (D.R.O.), Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address for T.M. Mabry: mabry.tad@mayo.edu.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Wagner
authors.affiliation: Departments of Orthopedic Surgery (C.D.W., E.R.W., M.T.H., A.D.H., D.G.L., and T.M.M.) and Internal Medicine, Division of Infectious Diseases (D.R.O.), Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address for T.M. Mabry: mabry.tad@mayo.edu.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Houdek
authors.affiliation: Departments of Orthopedic Surgery (C.D.W., E.R.W., M.T.H., A.D.H., D.G.L., and T.M.M.) and Internal Medicine, Division of Infectious Diseases (D.R.O.), Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address for T.M. Mabry: mabry.tad@mayo.edu.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Osmon
authors.affiliation: Departments of Orthopedic Surgery (C.D.W., E.R.W., M.T.H., A.D.H., D.G.L., and T.M.M.) and Internal Medicine, Division of Infectious Diseases (D.R.O.), Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address for T.M. Mabry: mabry.tad@mayo.edu.
authors.forename: Arlen D
authors.initials: AD
authors.lastname: Hanssen
authors.affiliation: Departments of Orthopedic Surgery (C.D.W., E.R.W., M.T.H., A.D.H., D.G.L., and T.M.M.) and Internal Medicine, Division of Infectious Diseases (D.R.O.), Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address for T.M. Mabry: mabry.tad@mayo.edu.
authors.forename: David G
authors.initials: DG
authors.lastname: Lewallen
authors.affiliation: Departments of Orthopedic Surgery (C.D.W., E.R.W., M.T.H., A.D.H., D.G.L., and T.M.M.) and Internal Medicine, Division of Infectious Diseases (D.R.O.), Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address for T.M. Mabry: mabry.tad@mayo.edu.
authors.forename: Tad M
authors.initials: TM
authors.lastname: Mabry
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus; D008875:Middle Aged; D009767:Obesity, Morbid / Q000150:complications*; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000209:etiology*; D012008:Recurrence; D012086:Reoperation / Q000706:statistics & numerical data; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000209:etiology; D013997:Time Factors; D017211:Treatment Failure