Antimicrobial prophylaxis in noninstrumented spine surgery: a prospective study to determine efficacy and drawbacks.

OBJECTIVE The authors sought to evaluate the roles of perioperative antibiotic prophylaxis in noninstrumented spine surgery (NISS), both in postoperative infections and the impact on the selection of resistant bacteria. To the authors' knowledge, only one prospective study recommending preoperative intravenous (IV) antibiotics for prophylaxis has been published previously. METHODS Two successive prospective IV antibiotic prophylaxis protocols were used: from 2011 to 2013 (group A: no prophylactic antibiotic) and from 2014 to 2016 (group B: prophylactic cefazolin). Patient infection rates, infection risk factors, and bacteriological status were determined. RESULTS In total, 2250 patients (1031 in group A and 1219 in group B) were followed for at least 1 year. The authors identified 72 surgical site infections, 51 in group A (4.9%) and 21 in group B (1.7%) (p < 0.0001). A multiple logistic regression hazard model identified male sex (HR 2.028, 95% CI 1.173-3.509; p = 0.011), cervical laminectomy (HR 2.078, 95% CI 1.147-3.762; p = 0.016), and postoperative CSF leak (HR 43.782, 95% CI 10.9-189.9; p < 0.0001) as independent predictive risk factors of infection. In addition, preoperative antibiotic prophylaxis was the only independent favorable factor (HR 0.283, 95% CI 0.164-0.488; p < 0.0001) that significantly reduced infections for NISS. Of 97 bacterial infections, cefazolin-resistant bacteria were identified in 26 (26.8%), with significantly more in group B (40%) than in group A (20.9%) (p = 0.02). CONCLUSIONS A single dose of preoperative cefazolin is effective and mandatory in preventing surgical site infections in NISS. Single-dose antibiotic prophylaxis has an immediate impact on cutaneous flora by increasing cefazolin-resistant bacteria.