Objective:

The purpose of this study was to examine the relationship between timing of preoperative surgical antibiotic prophylaxis and postoperative surgical site infections (SSIs) among 1-3 level lumbar fusion patients.

Methods:

Patients having undergone a primary 1-3 level lumbar fusion at a single institution were allocated into 5 groups based on the time period from preoperative antibiotic administration to incision (Group A = 0-15 min, Group B = 16-30 min, Group C = 31-45 min, Group D = 46 – 60 min, and Group E = 61+ min). Timing of antibiotic administration as a continuous variable was also analyzed. All patients received irrigation with 3 liters of normal saline containing bacitracin as well as local administration of vancomycin powder. SSIs were identified by the definition set forth by the 2017 Centers for Disease Control and Prevention (CDC) guidelines.

Results:

Among 1,131 patients, 27 (2.4%) patients were found to have an SSI. Compared to patients with antibiotic administration within 0-15 minutes prior to incision, patients with administration 61+ minutes prior to incision (Group 4) had significantly higher odds of developing a SSI (p: < 0.001). Patients had a 1.05-fold higher likelihood of infection for each additional minute delay of administration prior to incision (p: < 0.001). ROC analysis reported an AUC of 0.733 and 0.776 for time as a continuous and categorical variable, respectively. Age (p: 0.02), BMI (p: 0.03), diabetes mellitus diagnosis (p: 0.04), and type of antibiotic (p: 0.004) were significant predictors of SSI.

Conclusions:

Our results present that preoperative antibiotic administration beyond one hour in patients who have undergone lumbar fusion is associated with higher rates of SSI.