Postoperative infection in spine surgery: does the month matter?

Abstract

<jats:sec> <jats:title>OBJECT</jats:title> <jats:p>The relationship between time of year and surgical site infection (SSI) following neurosurgical procedures is poorly understood. Authors of previous reports have demonstrated that rates of SSI following neurosurgical procedures performed during the summer months were higher compared with rates during other seasons. It is unclear, however, if this difference was related to climatological changes or inexperienced medical trainees (the July effect). The aim of this study was to evaluate for seasonal variation of SSI following spine surgery in a network of nonteaching community hospitals.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>The authors analyzed 6 years of prospectively collected surveillance data (January 1, 2007, to December 31, 2012) from all laminectomies and spinal fusions from 20 hospitals in the Duke Infection Control Outreach Network of community hospitals. Surgical site infections were defined using National Healthcare Safety Network criteria and identified using standardized methods across study hospitals. Regression models were then constructed using Poisson distribution to evaluate for seasonal trends by month. Each analysis was first performed for all SSIs and then for SSIs caused by specific organisms or classes of organisms. Categorical analysis was performed using two separate definitions of summer: June through September (definition 1), and July through September (definition 2). The prevalence rate of SSIs during the summer was compared with the prevalence rate during the remainder of the year by calculating prevalence rate ratios and 95% confidence intervals.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>The authors identified 642 SSIs following 57,559 neurosurgical procedures (overall prevalence rate = 1.11/100 procedures); 215 occurred following 24,466 laminectomies (prevalence rate = 0.88/100 procedures), and 427 following 33,093 spinal fusions (prevalence rate = 1.29/100 procedures). Common causes of SSI were <jats:italic>Staphylococcus aureus</jats:italic> (n = 380; 59%), coagulase-negative staphylococci (n = 90; 14%), and <jats:italic>Escherichia coli</jats:italic> (n = 41; 6.4%). Poisson regression models demonstrated increases in the rates of SSI during each of the summer months for all SSIs and SSIs due to gram-positive cocci, <jats:italic>S. aureus</jats:italic>, and methicillin-sensitive <jats:italic>S. aureus</jats:italic>. Categorical analysis confirmed that the rate of SSI during the 4-month summer period was higher than the rate during the remainder of the year, regardless of which definition for summer was used (definition 1, p = 0.008; definition 2, p = 0.003). Similarly, the rates of SSI due to grampositive cocci and <jats:italic>S. aureus</jats:italic> were higher during the summer months than the remainder of the year regardless of which definition of summer was used. However, the rate of SSI due to gram-negative bacilli was not.</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>The rate of SSI following fusion or spinal laminectomy/laminoplasty was higher during the summer in this network of community hospitals. The increase appears to be related to increases in SSIs caused by gram-positive cocci and, more specifically, <jats:italic>S. aureus</jats:italic>. Given the nonteaching nature of these hospitals, the findings demonstrate that increases in the rate of SSI during the summer are more likely related to ecological and/or environmental factors than the July effect.</jats:p></jats:sec>

Analysis of Postoperative Thoracolumbar Spine Infections in a Prospective Randomized Controlled Trial Using the Centers for Disease Control Surgical Site Infection Criteria

“…Encouraging is the recent publication of a prospectively Table 1 gathered spinal SSI population meeting CDC criteria, although those patients did not have the same increased risk as our patient population of universally having an intraoperative drain placed. 19 An interesting finding was the prevalence of P. acnes, which occurred as frequently as MSSA and MRSA in our series and comprised 10% of the culturepositive organisms found in our series (Table 1); this incidence is consistent with recent literature. [20][21] Also consistent with the majority of the postoperative spinal infection literature was that our most common causative organism was S. aureus (comprising 20% of International Journal of Spine Surgerythe culture-positive organisms in our study) with coagulase-negative staphylococcus and E. coli comprising a significant representation as well.…”

“…[20][21] Also consistent with the majority of the postoperative spinal infection literature was that our most common causative organism was S. aureus (comprising 20% of International Journal of Spine Surgerythe culture-positive organisms in our study) with coagulase-negative staphylococcus and E. coli comprising a significant representation as well. 19,[22][23][24][25] In conclusion our series, which represents one of the first analyses of prospectively collected thoracolumbar postoperative spine infections meeting CDC criteria, revealed an overall infection incidence of 12.7%, of which only 50% grew organisms on culture. The three most common organisms in our analysis (S. aureus, P. acnes, E. coli) are consistent with previous reports.…”

Associations between seasonal variation and post-operative complications after total hip arthroplasty

“…Particularly in orthopedics, Gruskay et al demonstrated a statistically significant increase in post-operative infection rate in summer (4.1%) vs. spring (2.8%; P=0.03) following spine surgery (13). Furthermore, Durkin et al confirmed the higher rate of superficial skin infection following spine surgery during the summer, and since their study was performed in a nonteaching hospital, they attributed the increases in the rate of complications during the summer to be related to ecological and/or environmental factors rather than the July effect (14).…”

The Seasonal Variability in Surgical Site Infections and the Association With Warmer Weather: A Population-Based Investigation

“…For example, some studies have demonstrated an increased incidence of SSIs for surgeries performed during summer months. 12,22–24 …”