Impact of intrawound vancomycin powder on prevention of surgical site infection after posterior spinal surgery.

Surgical site infection (SSI) after posterior spinal surgery is one of the severe complications that may occur despite administration of prophylactic antibiotics and the use of intraoperative aseptic precautions. The use of intrawound vancomycin powder for SSI prevention is still controversial, with a lack of high-quality and large-scale studies. The purpose of this retrospective study using a propensity score-matched analysis was to clarify whether intrawound vancomycin powder prevents SSI occurrence after spinal surgery. The authors analyzed 1261 adult patients who underwent posterior spinal surgery between 2010 and 2018 (mean age 62.3 years; 506 men, 755 women; follow-up period at least 1 year). Baseline and surgical data were assessed. After a preliminary analysis, a propensity score model was established with adjustments for age, sex, type of disease, and previously reported risk factors for SSI. The SSI rates were compared between patients with intrawound vancomycin powder treatment (vancomycin group) and those without (control group). In a preliminary analysis of 1261 unmatched patients (623 patients in the vancomycin group and 638 patients in the control group), there were significant differences between the groups in age (p = 0.041), body mass index (p = 0.013), American Society of Anesthesiologists classification (p < 0.001), malnutrition (p = 0.001), revision status (p < 0.001), use of steroids (p = 0.019), use of anticoagulation (p = 0.033), length of surgery (p = 0.003), estimated blood loss (p < 0.001), and use of instrumentation (p < 0.001). There was no significant difference in SSI rates between the vancomycin and control groups (21 SSIs [3.4%] vs 33 SSIs [5.2%]; OR 0.640, 95% CI 0.368-1.111; p = 0.114). Using a one-to-one propensity score-matched analysis, 444 pairs of patients from the vancomycin and control groups were selected. There was no significant difference in the baseline and surgical data, except for height (p = 0.046), between both groups. The C-statistic for the propensity score model was 0.702. In the score-matched analysis, 12 (2.7%) and 24 (5.4%) patients in the vancomycin and control groups, respectively, developed SSIs (OR 0.486, 95% CI 0.243-0.972; p = 0.041). There were no systemic complications related to the use of vancomycin. The current study showed that intrawound vancomycin powder was useful in reducing the risk of SSI after posterior spinal surgery by half, without adverse events. Intrawound vancomycin powder use is a safe and effective procedure for SSI prevention.