Seasonal variation and preoperative risk factors for polymicrobial infection following open fracture

Despite modern approaches to open fracture management, fracture-related infection (FRI) rates remain high. Recent studies demonstrated the seasonal and regional variation of causative organisms in FRI. This study aims to better understand the causative organisms and identify preoperative risk factors for the primary outcome of FRIs at a Level I trauma center.

This retrospective cohort study examined all patients that underwent irrigation and debridement of an open fracture at a single Level I trauma center between 2007 and 2019. Exclusion criteria included gunshot wounds, hand injuries, and follow-up less than 3 months. Patients that developed FRI were compared by season, injury characteristics, patient demographics, initial management, and causative organisms.

Among 695 patients with open fractures, 78 patients (11.2 %) developed infection, of which eight were Gustilo-Anderson (GA) Type I, 16 were GA Type II, 25 were GA Type IIIA, 26 were GA Type IIIB, and three were GA Type IIIC. Gram-positive FRIs were most common (81.1 %), followed by 56.8 % polymicrobial, 54.1 % gram-negative, and 10.1 % culture-negative infections. More than half (55.1 %) of the infections were from open tibial fractures and occurred after a motorcycle (32.1 %) or motor vehicle collision (23.1 %). Patients were more likely to have high FRI rates in the summer (12.8 %, n = 29) and fall (15.8 %, n = 32) in comparison of spring (4.7 %, n = 7) and winter (8.5 %, n = 10) (p < 0.01). Staphylococcus infections were more common in fall and winter (73.8 %, n = 31) versus spring and summer (44.4 %, n = 16) (p = 0.01). Patients that were transferred from outside hospitals had significantly higher rates of polymicrobial infection when compared to those who arrived from the field (63.6 % vs 41.2 %, p = 0.03). No differences were observed in infection causative organisms based on GA type.

Two preoperative risk factors for polymicrobial infection following open fracture include inter-hospital transfers and warm/humid weather. Broadening antibiotic prophylaxis during spring/summer months or for transferred patients may enhance antibiotic coverage and reduce infections.