Effect of surgical delay on bacterial colonization in proximal humeral fractures

Postoperative infection is a severe complication after proximal humeral fracture surgical treatment. The aim of this study was to determine if the surgical delay could modify the number and type of bacteria on the surgical site. A two stages study was set up. In the first stage the effect of delay was simulated in 20 patients affected by proximal humeral fracture treated conservatively. In a second stage, the effect of delay was measured in 20 patients that underwent surgery. In stage 1, three skin culture swabs were taken in correspondence of the deltopectoral approach, the day of the fracture (day 0), the day after (day 1), and five days after fracture (day 5). In stage 2, skin swab cultures were taken the day of trauma and immediately before surgery and cultured on various media suitable for aerobic and anaerobic bacteria. The number of bacteria increased over the course of the study, from day 0 to day 5, both considering the total number of colony-forming units and individual species of pathogen bacteria. The second stage of the study confirmed these data. An increasing number of bacteria was observed in patients that underwent surgery later than 2 days from trauma. The delay of surgery increased bacterial colonization of the skin in the deltopectoral approach area including common pathogenic bacteria such as Staphylococcus aureus, coagulase-negative staphylococci and Propionibacterium acnes. This might justify the correlation between delay to surgery and risk of infection.