Effects of extended oral antibiotic prophylaxis on surgical site infections after instrumented spinal fusion: a cohort study of 901 patients with a minimum follow-up of 1 year.

Background And Purpose: We aimed to determine whether an extended oral antibiotic prophylaxis protocol may reduce the rate of surgical site infection (SSI) in patients undergoing instrumented spinal fusion.

Patients And Methods: This retrospective cohort study comprise 901 consecutive patients subjected to spinal fusion between September 2011 and December 2018 with a minimum 1-year follow-up. 368 patients operated on between September 2011 and August 2014 were administered standard intravenous prophylaxis. 533 patients operated on between September 2014 and December 2018 were administered an extended protocol with 500 mg of oral cefuroxime axetil every 12 hours (clindamycin or levofloxacin in allergic individuals) until the removal of sutures. SSI was defined following the Centers for Disease Control and Prevention criteria. The association between risk factors and the incidence of SSI was evaluated by odds ratio (OR) with a multiple logistic regression model.

Results: The bivariate analysis showed a statistically significant association between SSI and the type of prophylaxis used ("extended"' = 1.7% vs. "standard" = 6.2%, p= 0.001), with a lower proportion of superficial SSIs with the extended regimen (0.8% vs. 4.1%, p = 0.001). The multiple logistic regression model showed an OR = 0.25 (95% confidence interval [CI] 0.10-0.53) for extended prophylaxis and an OR = 3.5 (CI 1.3-8.1) for non-beta-lactams antibiotics.

Conclusion: Extended antibiotic prophylaxis seems to be associated with a reduction in the incidence of superficial SSI in instrumented spine surgery.