title: Obesity Is an Independent Risk Factor of Early Complications After Revision Spine Surgery.
abstract: METHODS
  Retrospective cohort analysis of risk factors in revision spine surgery using a prospectively collected database.
  
  
  OBJECTIVE
  To examine the risk of developing early (30-day) complications across obesity level after adjusting for comorbidities in patients undergoing revision spine surgery.
  
  
  BACKGROUND
  Prior studies suggest obesity influences early complications after primary surgery. The association between obesity and early complications after revision surgery remains to be characterized.
  
  
  METHODS
  Data were abstracted from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database from 2005 to 2012. Adult Caucasian patients undergoing removal/revision of instrumentation or exploration of fusion were included. Patients were categorized by WHO body mass index (BMI, kg/m): Non-Obese (18.5-29.9), Obese Class I (30-34.9), and Obese Class II/III (≥35). Univariate regression was performed to assess the predictive value of obesity level and baseline risk factors in the presence of at least one early complication, and significant predictors were entered into the multivariable model.
  
  
  RESULTS
  Of 2538 patients, 57.6% were nonobese, 23% Obese Class I, and 19.4% Obese Class II/III. Obesity was associated with diabetes, hypertension, respiratory disease, and American Society of Anesthesiologists (ASA) score of 3-4 (all P < 0.001). BMI group (P = 0.01), older age (P = 0.008), functional dependence (P < 0.001), ASA 3-4 (P = 0.008), bleeding disorder (P = 0.04), and diabetes (P = 0.016) were identified as univariate predictors for early complications. In the multivariable model, higher BMI (P = 0.04), older age (P = 0.014), and functional dependence (P < 0.001) remained significant predictors for early complications. Notably, patients who were Obese Class II/III (OR 1.66, 95% CI [1.12-2.45]), age ≥75 (OR 1.83, [1.20-2.81]), and functionally dependent (OR 3.02 [1.85-4.94]) had significantly higher risk compared with their reference groups.
  
  
  CONCLUSIONS
  Obesity is an independent risk factor for early complications after revision spine surgery. Although obesity may not contraindicate revision surgery, its status as a modifiable risk factor warrants disclosure and preoperative counseling to optimize outcomes.
  
  
  METHODS
  3.
authors.affiliation: *Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA †Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA.
authors.forename: David C
authors.initials: DC
authors.lastname: Sing
authors.forename: John K
authors.initials: JK
authors.lastname: Yue
authors.forename: Lionel N
authors.initials: LN
authors.lastname: Metz
authors.forename: Ethan A
authors.initials: EA
authors.lastname: Winkler
authors.forename: William R
authors.initials: WR
authors.lastname: Zhang
authors.forename: Shane
authors.initials: S
authors.lastname: Burch
authors.forename: Sigurd H
authors.initials: SH
authors.lastname: Berven
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000601:surgery*; D011183:Postoperative Complications / Q000175:diagnosis / Q000209:etiology*; D011446:Prospective Studies; D012086:Reoperation / Q000009:adverse effects* / Q000639:trends; D012189:Retrospective Studies; D012307:Risk Factors; D013123:Spinal Fusion / Q000009:adverse effects* / Q000639:trends; D055815:Young Adult