The efficacy of intrawound vancomycin powder and povidone-iodine irrigation to prevent surgical site infections in complex instrumented spine surgery

BACKGROUND CONTEXT: Surgical site infections (SSIs) are notorious complications in spinal surgery and cause substantial patient morbidity. Intraoperative decontamination of the wound with povidone-iodine irrigation or vancomycin powder has gained attention lately, but the efficacy of either intervention is unclear. PURPOSE: To determine the efficacy of intrawound povidone-iodine or vancomycin in reducing the incidence of deep- and superficial SSIs in instrumented spinal surgery. STUDY DESIGN/SETTING: Retrospective cohort study. PATIENT SAMPLE: A retrospective chart review was performed including all consecutive adult patients undergoing open, posterior, instrumented spinal surgery at any level between January 2012 and August 2017. OUTCOME MEASURES: The presence of SSI was evaluated according to the criteria published by the Centers for Disease Control and Prevention. The SSIs were divided into deep SSIs (below the muscular fascia) and superficial SSIs (above the muscular fascia). METHODS: A retrospective cohort without intrawound treatment was compared with two separate, consecutive intervention groups. One intrawound group received 1.3g/L povidone-iodine irrigation and the other received 1-2 grams of intrawound vancomycin powder at the end of surgery. Incidence of SSIs, as well as demographic, surgical and patient-related variables were registered and compared between groups. In patients with SSI, additional microbiological data were collected. RESULTS: In total, 853 patients were included. In the control group (N=257), 25 (9.7%) patients developed a deep and 13 (5.1%) developed a superficial SSI. In the povidone-iodine group (N=217), 21 (9.7%) patients developed a deep and two (0.9%) developed a superficial SSI. Compared with the control group, there was no significant difference in the incidence of deep SSIs (risk ratio [RR]: 1.00, 95% CI 0.57–1.73), although the number of superficial SSIs was reduced significantly (RR 0.18, 95% CI 0.04–0.80). In the vancomycin group (N=379), 19 (5.0%) patients developed a deep and six (1.6%) developed a superficial SSI. Both deep (RR: 0.52, 95% CI 0.29–0.92) and superficial SSIs (RR: 0.31, 95% CI 0.12–0.81) were significantly reduced in the vancomycin group compared with the control group, even when correcting for several risk factors associated with SSIs in a multivariable logistic regression analysis. There were no significant differences in complications between the 3 groups. No gram-negative selection or vancomycin-resistance was seen in the vancomycin group. CONCLUSIONS: Intrawound application of vancomycin was associated with a significant reduction in both deep and superficial SSIs in instrumented spinal surgery. A 1.3g/L intrawound povidone-iodine solution did not show a reduction in deep SSIs, although a reduction of superficial SSIs was observed.