Evaluating the Impact of Povidone-Iodine Irrigation on Microbial Contamination in Reverse Total Shoulder Arthroplasty

Aims: One of the primary causes of periprosthetic joint infection (PJI) in reverse total shoulder arthroplasty (RTSA) is intraoperative contamination. This study aimed to evaluate the effectiveness of povidone-iodine irrigation in reducing bacterial contamination of the surgical field during primary RTSA. Methods: Sixty-five patients were prospectively included. Patients with fractures, osteonecrosis, tumors, or previous surgical treatment failures, as well as those who had received recent antibiotic or infiltrative therapy, were excluded. At the end of the surgery, six different samples were collected. The first set of three samples—one swab from the glenosphere, one from the humeral component, and one from the periprosthetic tissue—were obtained before irrigation (using a 0.35% povidone-iodine solution diluted with saline). The second set of three samples was taken from the same sites, but after irrigation. The six samples were processed to perform both qualitative and quantitative assessments of the microbial load. Results: C. acnes was the only anaerobic strain recovered, found in both swabs and periprosthetic tissues, while the aerobic flora included gram-positive bacteria—mainly coagulase-negative staphylococci (CoNS)—and few gram-negative species. Povidone-iodine irrigation significantly reduced both the positivity rates and bacterial loads of C. acnes and CoNS. C. acnes loads decreased from ~10³ to ~10² CFUs/ml, and CoNS loads decreased from ~10¹ to nearly zero CFUs/ml. The time to culture positivity for C. acnes depended on the bacterial load, ranging from 3–5 days (≥10³ CFUs/ml) to >6 days (≤10² CFUs/ml), while the aerobes grew faster (1–4 days). Higher C. acnes positivity and loads were associated with male sex and the use of CTA as a surgical indication. Conclusion: Intraoperative irrigation with povidone-iodine is significantly effective in reducing bacterial contamination rates during RTSA surgery, despite C. acnes is less susceptible than CoNS.