title: Does minimally invasive surgery have a lower risk of surgical site infections compared with open spinal surgery?
abstract: BACKGROUND
  Surgical site infection (SSI) ranges from 1.9% to 5.5% in most large series. Minimally invasive surgery (MIS) has been postulated to reduce SSI rates.
  
  
  OBJECTIVE
  (1) Is MIS associated with a lower incidence of SSI compared with open spinal surgery? (2) Are there other independent risk factors associated with SSI? (3) What bacteria are most common in spinal SSI?
  
  
  METHODS
  Medical records of 2299 patients who underwent transforaminal lumbar interbody fusion, laminectomy, or discectomy were analyzed and selected for a nested case-control analysis. Twenty-seven cases with SSI were matched with 162 control subjects without SSI stratified based on procedure performed within 28 days of the case's date of surgery. Patients were identified from an institutional database at a tertiary care hospital. MIS involved spinal procedures performed through a tubular retractor system. Univariate and multivariate analyses were performed.
  
  
  RESULTS
  Patients undergoing open spinal surgery were 5.77 times more likely to develop SSI compared with MIS approaches (odds ratio [OR], 5.77; 95% confidence interval [CI], 1.0-32.7; p = 0.048). Also, from the multivariate regression model, diabetes (OR, 4.7; 95% CI, 1.3-17.0; p = 0.018), number of levels operated on (OR, 3.5; 95% CI, 1.6-7.5; p = 0.001), and body mass index (OR, 1.2; 95% CI, 1.0-1.3; p = 0.010) were predictive of an increased risk in SSI. Staphylococcus aureus was most frequently identified, being present in 12 of 21 (52.4%) patients in whom positive cultures were obtained. Four of the 12 patients had methicillin-resistant S aureus infection.
  
  
  CONCLUSIONS
  In our series, MIS has a lower incidence of SSI. The risk factors predictive of SSI should be further evaluated in well-designed prospective trials.
  
  
  METHODS
  Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedics, Singapore General Hospital, Outram Road, Singapore, 169 608, Singapore, gerardee@gmail.com.
authors.forename: Wen Wei Gerard
authors.initials: WW
authors.lastname: Ee
authors.forename: Wen Liang Joel
authors.initials: WL
authors.lastname: Lau
authors.forename: William
authors.initials: W
authors.lastname: Yeo
authors.forename: Yap
authors.initials: Y
authors.lastname: Von Bing
authors.forename: Wai Mun
authors.initials: WM
authors.lastname: Yue
mesh_terms: D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D017586:Diskectomy / Q000009:adverse effects; D005260:Female; D006801:Humans; D015994:Incidence; D007796:Laminectomy / Q000009:adverse effects; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures; D015999:Multivariate Analysis; D016017:Odds Ratio; D019637:Orthopedic Procedures / Q000009:adverse effects* / Q000379:methods; D012189:Retrospective Studies; D012307:Risk Factors; D012846:Singapore / Q000453:epidemiology; D013123:Spinal Fusion / Q000009:adverse effects; D013131:Spine / Q000601:surgery*; D013530:Surgical Wound Infection / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D062606:Tertiary Care Centers; D016896:Treatment Outcome