Ceftriaxone versus cefazolin plus gentamicin for antibiotic prophylaxis in Gustilo-Anderson type III open lower extremity fractures.

OBJECTIVES: To compare fracture related infection (FRI) rates and outcomes between ceftriaxone (CTX) and cefazolin plus gentamicin (C+G) for antibiotic prophylaxis in Gustilo-Anderson (GA) type III open lower extremity fractures. METHODS: Design: Retrospective cohort study. SETTING: Single, academic level one trauma center. PATIENT SELECTION CRITERIA: Included were patients age 18-89 years with GA type III open lower extremity fractures (AO/OTA 32,33,41,42,43,4F3, 44) from 2013 to 2024 with at least 6 weeks follow-up. OUTCOME MEASUREMENTS AND COMPARISONS: The primary outcome was FRI. Secondary outcomes included acute kidney injury (AKI), nonunion, and other complications. Cox proportional hazards models and multivariable logistic regression adjusted for confounding variables. RESULTS: Of 3,334 lower extremity fractures reviewed, 307 met inclusion criteria: 229 C+G and 78 CTX. Mean age (40.4 [range 18-88] vs 41.2 [range 18-81] years, p=0.7) and sex (75.1% vs 64.1% male, p=0.084) were similar between the C+G and CTX cohorts. Mean follow-up was 23.8 months (C+G) and 14.0 months (CTX) (P=0.002). The C+G cohort had more tibial shaft fractures (34.1% vs 19.2%, P=0.014) and type IIIB injuries (19.7% vs 7.7%, P=0.014). On unadjusted analysis, there was no significant difference in FRI (18.3% vs 12.8%, P=0.343) or AKI (11.4% vs 12.8%, P=0.728) or organisms cultured. After adjusting for GA type, fracture location, time to debridement and time to antibiotics there remained no significant difference in FRI (HR=1.26, 95% CI: 0.59-2.68, P=0.545), AKI (OR=1.51, 95% CI: 0.62-3.49, P=0.349) or other complications between antibiotic regimens. Tibial shaft fractures trended towards higher risk of FRI compared to femur fractures (HR=2.15, P=0.052). GA type IIIB/C fractures (HR=3.05, p<0.001) and time to antibiotics of >60min (HR=2.56, p=0.003) were associated with higher odds of FRI. CONCLUSIONS: Ceftriaxone monotherapy demonstrated similar rate of FRI and complications compared to cefazolin plus gentamicin for Gustilo-Anderson type III open lower extremity fractures. Severity of the open fracture and time to antibiotics were independently associated with higher infection risk regardless of antibiotic regimen. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.