title: Seasonal Variations in the Risk of Reoperation for Surgical Site Infection Following Elective Spinal Fusion Surgery: A Retrospective Study Using the Japanese Diagnosis Procedure Combination Database.
abstract: METHODS
  A retrospective study of data abstracted from the Diagnosis Procedure Combination (DPC) database, a national representative database in Japan.
  
  
  OBJECTIVE
  The aim of this study was to examine seasonal variations in the risk of reoperation for surgical site infection (SSI) following spinal fusion surgery.
  
  
  BACKGROUND
  Although higher rates of infection in the summer than in other seasons were thought to be caused by increasing inexperience of new staff, high temperature, and high humidity, no studies have examined seasonal variations in the risk of SSI following spinal fusion surgery in the country where medical staff rotation timing is not in summer season. In Japan, medical staff rotation starts in April.
  
  
  METHODS
  We retrospectively extracted the data of patients who were admitted between July 2010 and March 2013 from the DPC database. Patients were included if they were aged 20 years or older and underwent elective spinal fusion surgery. The primary outcome was reoperation for SSI during hospitalization. We performed multivariate analysis to clarify the risk factors of primary outcome with adjustment for patient background characteristics.
  
  
  RESULTS
  We identified 47,252 eligible patients (23,659 male, 23,593 female). The mean age of the patients was 65.4 years (range, 20-101 yrs). Overall, reoperation for SSI occurred in 0.93% of the patients during hospitalization. The risk of reoperation for SSI was significantly higher in April (vs. February; odds ratio, 1.93; 95% confidence interval, 1.09-3.43, P = 0.03) as well as other known risk factors. In subgroup analysis with stratification for type of hospital, month of surgery was identified as an independent risk factor of reoperation for SSI among cases in an academic hospital, although there was no seasonal variation among those in a nonacademic hospital.
  
  
  CONCLUSIONS
  This study showed that month of surgery is a risk factor of reoperation for SSI following elective spinal fusion surgery, nevertheless, in the country where medical staff rotation timing is not in summer season.
  
  
  METHODS
  3.
authors.affiliation: Department of Orthopaedic Surgery, the University of Tokyo, Tokyo, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Ohya
authors.affiliation: Department of Orthopaedic Surgery, the University of Tokyo, Tokyo, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Chikuda
authors.affiliation: Department of Orthopaedic Surgery, the University of Tokyo, Tokyo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Oichi
authors.affiliation: Department of Orthopaedic Surgery, the University of Tokyo, Tokyo, Japan.
authors.forename: So
authors.initials: S
authors.lastname: Kato
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, The University of Tokyo, Tokyo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, The University of Tokyo, Tokyo, Japan.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Horiguchi
authors.affiliation: Department of Orthopaedic Surgery, the University of Tokyo, Tokyo, Japan.
authors.forename: Sakae
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, The University of Tokyo, Tokyo, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Yasunaga
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016208:Databases, Factual; D017558:Elective Surgical Procedures / Q000009:adverse effects / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012086:Reoperation; D012189:Retrospective Studies; D012621:Seasons; D013123:Spinal Fusion / Q000009:adverse effects / Q000706:statistics & numerical data*; D013530:Surgical Wound Infection / Q000453:epidemiology* / Q000209:etiology; D055815:Young Adult