Subcutaneous tissue disinfection significantly reduces C. acnes burden in primary open shoulder surgery.

Introduction Cutibacterium acnes is one of the major pathogens responsible for infection after shoulder surgery. Surgical dissection of the dermis may expose C. acnes from sebum-producing hair follicles. Due to contact with surgeon's gloves and instruments these are further spread throughout the surgical field. The purpose of this study was to determine if subcutaneous tissue disinfection could reduce the C. acnes culture rate in primary open shoulder surgery. Methods All patients eligible for primary open shoulder surgery using a deltopectoral approach were prospectively enrolled in our 2-arm randomized, single blinded clinical trial. In all patients a skin swab of the operative field was taken prior to standard surgical skin preparation. After exposure of the deltoid fascia, the disinfection group received an additional preparation of the subcutaneous layer with povidone-iodine solution. Once the proximal humerus was completely exposed, 5 swabs from different sites were taken for microbiological examination according to a strict specimen collection protocol. All cultures were incubated in aerobic and anaerobic conditions for 14 days. Results Between February 2019 and December 2019, 108 patients were enrolled in two groups (70 treatment vs 38 control). The two groups did not show any significant difference in terms of gender, age, BMI or occurrence of diabetes. The subcutaneous disinfection protocol reduced significantly the positive culture rate of the operating field for all germs combined (p = 0.036) and specifically for C. acnes (p = 0.013). The reduction of positive swabs for C. acnes was significant for the surgeon's gloves (p = 0.041) as well as for the retractors (p = 0.007). Conclusion Disinfection of the subcutaneous tissue significantly reduced the C. acnes culture rate during primary open shoulder surgery. We highly recommend this simple step as adjunct to the current surgical practice in order to limit iatrogenic contamination of the surgical field. Future studies may observe a reduction in postoperative shoulder infection due to this practice.