Type III Gustilo-Anderson open fracture does not justify routine prophylactic Gram-negative antibiotic coverage.

Postoperative surgical site infection (SSI) is common in open long bone fractures, so early administration of prophylactic antibiotics is critical to prevent SSI. However, the necessity of initial broad-spectrum coverage for Gram-positive and -negative pathogens remains unclear. The purpose of this study was to clarify the effectiveness of prophylactic broad-spectrum antibiotics in a large, national-wide sample. We reviewed an open fracture database of prospectively collected data from 111 institutions managed by our society. A retrospective cohort study was designed to compare the rates of deep SSI between narrow- and broad-spectrum antibiotics, which were initiated within three hours after injury. A total of 1041 type III fractures were evaluated at three months after injury. Overall deep SSI rates did not differ significantly between the narrow-spectrum group (43/538, 8.0%) and broad-spectrum group (49/503, 9.8%) (p = 0.320). During propensity score-matched analysis, 425 pairs were analyzed. After matching, no significant difference in the SSI rate was seen between the narrow- and broad-spectrum groups, with 42 SSIs (9.9%) and 40 SSIs (9.4%), respectively (p = 0.816). The probability of deep SSI was not reduced by broad-spectrum antibiotics compared with narrow-spectrum antibiotics in type III open long bone fractures.