Outcomes Associated with Choice of Prophylactic Antibiotics in Open Fractures.

BACKGROUND The ideal antibiotic prophylaxis for open fractures is unknown. We evaluated outcomes following different antibiotic prophylaxis regimens for open fractures. METHODS This is a secondary analysis of data from PREP-IT. Prophylactic antibiotics were defined as any intravenous antibiotic given on the day of admission. The outcomes were surgical site infection (SSI) within 90 days and reoperation within 1 year. Logistic regression and an instrumental variable analysis that leveraged site-level variation accounted for confounding. Subgroup variation was evaluated by stratifying by Gustilo-Anderson classification (Types I and II versus III). RESULTS Of the 3,331 included participants, the mean age was 45 ± 18 years, 63% were male, 73% were White, 21% were Black, 2% were Asian, and 10% were Hispanic. Cefazolin monotherapy (58% of patients), ceftriaxone monotherapy (10%), and cefazolin plus gentamicin (6%) were the most common regimens. In the instrumental variable analysis, the odds of infection did not significantly differ with ceftriaxone use (odds ratio [OR], 1.24; 95% confidence interval [CI], 0.70 to 2.20; p = 0.45) or cefazolin plus gentamicin use (OR, 0.25; 95% CI, 0.03 to 2.04; p = 0.20) compared with cefazolin monotherapy. There were no significant differences between the regimens with respect to infection when stratified by Gustilo-Anderson type. However, we did observe a nearly 3-fold increase in the odds of infection with ceftriaxone use compared with cefazolin monotherapy (OR, 2.73; 95% CI, 0.96 to 7.79; p = 0.06) in Type-I and II fractures, and a 75% decrease in the odds of infection with cefazolin plus gentamicin use (OR, 0.25; 95% CI, 0.03 to 2.02; p = 0.19) compared with cefazolin monotherapy in Type-III fractures. CONCLUSIONS Among patients with open fractures, antibiotic prophylaxis with ceftriaxone monotherapy did not provide significant benefits compared with cefazolin monotherapy in preventing infection in Type-I and II fractures. The findings suggest that cefazolin plus gentamicin might reduce the odds of infection in Type-III fractures compared with cefazolin monotherapy, but this difference was not statistically significant. LEVEL OF EVIDENCE Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.