Aims: Antibiotic administration, severity of injury, and debridement are associated with surgical site infection (SSI) after internal fixation of open fractures. We sought to validate a time-dependent treatment effect of antibiotic administration.

Patients: Consecutive open fracture patients at a level 1 trauma center with minimum 30-day follow-up were identified from an orthopaedic registry from 2013-2017.

Methods: The primary endpoint was SSI within 90 days. A threshold time to antibiotic administration associated with SSI was ascertained by receiver-operator analysis. A multivariate Cox proportional hazards model adjusted for open fracture type, smoking, and drug use determined the treatment effect of antibiotic administration within the threshold period.

Results: Ten percent of 230 patients developed a SSI. There was a trend for patients who did not develop an SSI to receive antibiotics earlier than those who did develop an SSI (61 minutes, IQR 33-107 vs 83 minutes, IQR 40-186), p=0.053). Intravenous antibiotic administration after 120 minutes of presentation of an open fracture to emergency department was significantly associated with a 2.7 increased hazard of surgical site infection (p=0.033) within 90 days. On subgroup analysis, the treatment effect of antibiotic administration within 120 minutes held for lower extremity fractures (HR=4.16, p=0.006). No significant treatment effect was observed for upper extremity fractures (p=0.932).

Conclusion: Antibiotic administration greater than 120 minutes after ED presentation of an open fracture was associated with an increased risk of SSI. The risk of SSI was greater for lower extremity fractures.

05 - Delay of Antibiotic Administration Greater Than 2 Hours Predicts Surgical Site Infection in Open Lower-Extremity Fractures