Background: 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. Because of contact with the surgeon's gloves and instruments, further spread occurs throughout the surgical field. The purpose of this study was to determine whether subcutaneous tissue disinfection could reduce the C acnes culture rate in primary open shoulder surgery.

Methods: All patients eligible for primary open shoulder surgery by 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 and December 2019, 108 patients were enrolled in the 2 groups: treatment (n = 70) and control (n = 38). The 2 groups did not show any significant difference in terms of sex, age, body mass index, or occurrence of diabetes. The subcutaneous disinfection protocol significantly reduced the positive culture rate of the operating field for all germs combined (P = .036) and specifically for C acnes (P = .013). The reduction of positive swabs for C acnes was significant for the surgeon's gloves (P = .041), as well as the retractors (P = .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 an adjunct to the current surgical practice to limit iatrogenic contamination of the surgical field. Future studies may observe a reduction in postoperative shoulder infection owing to this practice.