title: A methodological systematic review on surgical site infections following spinal surgery: part 1:  risk factors.
abstract: METHODS
  A methodological systematic review.
  
  
  OBJECTIVE
  To critically appraise the validity of risk factors for surgical site infection (SSI) after spinal surgery.
  
  
  BACKGROUND
  SSIs lead to higher morbidity, mortality, and increased health care costs. Understanding which factors lead to an increased risk of SSI is important for the development of prophylactic protocols to counter this risk. To date, however, no review appraising the methodological quality of studies evaluating risk factors for spinal SSIs has been published.
  
  
  METHODS
  Contemporary studies identifying risk factors for SSI after spinal surgery were searched through the Medline and EMBASE databases (January 2001 to December 2010). References were retrieved and bias-prone study features were abstracted individually and independently by 2 authors.
  
  
  RESULTS
  Twenty-four eligible studies were identified, including 9 (nested) case-control studies and 15 case series. Included studies covered wide variations of indications and surgical procedures. A total of 73 different types of factors were evaluated for the risk of an SSI of which 34 (47%) were reported to be significantly related to at least 1 study. Only the following risk factors-diabetes mellitus, obesity, and previous SSI-were confirmed more often (n = 11, 8, and 3, respectively) as a significant risk factor for an SSI than they were disproved (n = 7, 6, and 1, respectively). Various sources of heterogeneity were observed, including patient selection, selection and analysis of putative risk factors, and definitions of SSI outcomes.
  
  
  CONCLUSIONS
  There is an abundance of conflicting data on risk factors for SSI after spinal surgery. Given various sources of heterogeneity observed in observational literature, there is a paucity of solid evidence for the proof of robust risk factors. The authors recommend the introduction, validation, and use of a standardized set of strongly justified eligibility criteria and well-defined candidate risk factors and spinal SSI outcomes.
authors.affiliation: Department of General Surgery, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands. af@pulltergunne.nl
authors.forename: Albert F
authors.initials: AF
authors.lastname: Pull ter Gunne
authors.forename: Allard J F
authors.initials: AJ
authors.lastname: Hosman
authors.forename: David B
authors.initials: DB
authors.lastname: Cohen
authors.forename: Michael
authors.initials: M
authors.lastname: Schuetz
authors.forename: Drmed
authors.initials: D
authors.lastname: Habil
authors.forename: Cees J H M
authors.initials: CJ
authors.lastname: van Laarhoven
authors.forename: Joost J
authors.initials: JJ
authors.lastname: van Middendorp
mesh_terms: D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D006801:Humans; D009765:Obesity / Q000150:complications; D019637:Orthopedic Procedures / Q000009:adverse effects*; D012307:Risk Factors; D013131:Spine / Q000601:surgery*; D013530:Surgical Wound Infection / Q000209:etiology*