Postoperative infection in spine surgery: does the month matter?

Area of Science:

• Neurosurgery
• Infectious Disease Epidemiology
• Public Health

Background:

• Surgical site infections (SSIs) following neurosurgery are a concern.
• Previous studies suggested higher SSI rates during summer months, but the cause (climatological vs. trainee-related
• July effect") remained unclear.

Purpose of the Study:

• To investigate seasonal variations in SSI rates after spine surgery.
• To determine if observed summer increases in SSIs are linked to environmental or trainee-related factors in non-teaching hospitals.

Main Methods:

• Analysis of 6 years of prospectively collected surveillance data (2007-2012) from 20 community hospitals.
• Inclusion of all laminectomies and spinal fusions, defining SSIs using National Healthcare Safety Network criteria.
• Use of Poisson regression models to assess seasonal trends and categorical analysis to compare summer SSI rates with the remainder of the year.

Main Results:

• A total of 642 SSIs were identified in 57,559 neurosurgical procedures.
• Higher SSI prevalence rates were observed during summer months (June-September or July-September) compared to the rest of the year.
• Increases in SSIs were primarily associated with gram-positive cocci, particularly Staphylococcus aureus, while gram-negative bacilli showed no significant seasonal trend.

Conclusions:

• Spine surgery patients in community hospitals experience higher SSI rates during summer.
• The observed increase in SSIs is linked to gram-positive organisms, specifically S. aureus.
• Findings suggest ecological or environmental factors, not the "July effect," are likely drivers of summer SSI increases in these settings.