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 efectiveness of povidone-iodine irrigation in reducing bacterial contamination of the surgical feld during primary RTSA. Methods A total of 65 patients were prospectively included (mean age 74.1 years (SD 7.9); 43 female, 22 male). Patients with fractures, osteonecrosis, tumours, or previous surgical treatment failures, as well as those who had received recent antibiotic or infltrative therapy, were excluded. At the end of the surgery, six diferent samples were collected. The frst 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 Cutibacterium acnes was the only anaerobic strain recovered, found in both swabs and periprosthetic tissues, while the aerobic fora included gram-positive bacteria – mainly coagulase-negative staphylococci (CoNS) – and few gram-negative species. Povidone-iodine irrigation signifcantly reduced both the positivity rates and bacterial loads of C. acnes and CoNS. C. acnes loads decreased from ~103 to ~102 colony-forming units (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 three to fve days (≥ 103 CFUs/ml) to > six days (≤ 102 CFUs/ml), while the aerobes grew faster (one to four days). Higher C. acnes positivity and loads were associated with male sex and the use of cuf tear arthropathy as a surgical indication. Conclusion Intraoperative irrigation with povidone-iodine is signifcantly efective in reducing bacterial contamination rates during RTSA surgery, despite C. acnes being less susceptible than CoNS.