Risk Factors for Infection in Closed Surgical Wounds Identified

Defect size and the use of complex layered closure are associated with higher risks for infections in closed surgical wounds of the lower extremities, according to  study research published in the Journal of the American Academy of Dermatology.

The study used data from excisions and Mohs micrographic surgery of the lower extremities, which were performed by 3 fellowship-trained surgeons. Prior to intervention, the skin was treated with chlorhexidine disinfectant. Skin wound infections were identified based on photograph review and surgeon documentation. In patients with dehiscence or drainage, a wound culture was performed. A total of 41 infections from the 410 excisions and Mohs micrographic surgeries were identified. The overall infection rate was 10%.

Of the 410 surgeries included in this study, 27 (6.6 were culture-proven infections. The remaining 14 infections, including 2 with negative cultures, were classified as clinically infected. The median time to infection after these surgeries was 7.5 days (range, 3-46 days). In 15 cases of culture-proven infections, the primary organism on culture was methicillin-susceptible Staphylococcus aureus. In addition, the other cases had beta-hemolytic Streptococcus as well as Pseudomonas, Proteus, Escherichia coli, and Enterobacter.

For each 1cm² increase in defect size, the investigators observed a 1.2-times higher risk for infection (95% CI, 1.0-1.3; P =.02). Increasing wound size correlated with an increase in infection rate from 5% to 35%. The risk for infection in surgically closed wounds increased by 1.3 per cm² (95% CI, 1.1-1.6; P =.009). Defects ≥3 cm² featured a 6.2 times greater infection risk compared with smaller defects (95% CI, 1.9-20.8; P =.003). The investigators also observed a 4.1 times greater risk for infection with complex layered closure vs intermediate layered closure (95% CI, 1.9-20.8; P =.01) in an analysis that adjusted for defect size.

The researchers concluded that a surgical site infection “on the lower extremity may be reduced by avoiding complex closures, or limiting wound size, which can be achieved through Mohs micrographic surgery.”

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Reference

Nathan NR, O’Connor DM, Tiger JB, et al. Factors associated with surgical site infection of the lower extremity: a retrospective cohort study [published online March 31, 2020]. J Am Acad Dermatol. doi: 10.1016/j.jaad.2020.03.060