Optimal protocol for intraoperative irrigation to prevent periprosthetic joint infection : an in vitro study

Many surgeons use dilute povidone-iodine for intraoperative irrigation to prevent periprosthetic joint infection (PJI), with reported effectiveness. However, the timing of irrigation and its optimal concentration for effective bacterial eradication have not been established. This study aimed to investigate how the timing of intraoperative irrigation with dilute povidone-iodine affects bacterial eradication, and to determine the most effective timing and concentration for optimal results in an in vitro model.

Ti-6Al-4V washers were placed in medium and prepared methicillin-susceptible Staphylococcus aureus (MSSA) was added. Three different irrigation solutions (saline, 0.13% povidone-iodine, 0.35% povidone-iodine) were applied for three minutes in four different time patterns (15, 30, 60, 120 minutes) and returned to medium. This was repeated until 120 minutes had elapsed. Finally, the washers were exposed to saline and then removed. Floating bacteria in the saline were assessed using a spread plate method, while biofilm bacteria on the washers were evaluated using scanning electron microscopy (SEM), fluorescence microscopy, and a spread plate assay. Cytotoxicity was measured via the WST-1 assay, evaluating human osteoblast and fibroblast metabolic activity.

Dilute povidone-iodine irrigation successfully eliminated MSSA from the floating bacteria in all irrigation patterns (floating colony-forming units (CFU)/well: 0 ± 0 at all timepoints for both 0.13% and 0.35%). For biofilm bacteria, povidone-iodine irrigation within 30 minutes showed the most effective bacterial eradication (mean biofilm CFU/well (SD): 15 mins, 0 (0) vs 0 (0); 30 mins, 1,250 (433) vs 850 (310); 60 mins, 1,812 (429) vs 2,000 (500); 120 mins, 13,200 (2,100) vs 9,800 (1,850) for 0.13% vs 0.35%, respectively). SEM and fluorescence microscopy revealed low biofilm coverage when the washers were irrigated with povidone-iodine within 30 minutes (mean biofilm coverage, % (SD): 15 mins, 0.145 (0.012) vs 0.123 (0.010); 30 mins, 0.114 (0.002) vs 0.124 (0.006); 60 mins, 7.664 (0.091) vs 5.405 (0.351); 120 mins, 18.787 (0.133) vs 18.454 (0.210) for 0.13% vs 0.35%, respectively). Cytotoxicity analysis indicated that 0.13% povidone-iodine irrigation did not cause significant damage to human osteoblasts after 30, 60, and 120 minutes of exposure (mean cytotoxicity, % cell viability (SD): 15 mins, 45.47 (3.47) vs 23.87 (2.51); 30 mins, 58.24 (3.66) vs 34.93 (0.54); 60 mins, 58.78 (1.60) vs 46.14 (0.98); 120 mins, 55.42 (1.42) vs 43.69 (1.85) for 0.13% vs 0.35%, respectively). Additionally, no significant cytotoxicity was observed in human fibroblasts at any timepoint (mean cytotoxicity, % cell viability (SD): 15 mins, 57.85 (2.91) vs 31.88 (4.67); 30 mins, 56.12 (3.64) vs 37.78 (3.54); 60 mins, 60.08 (2.71) vs 44.95 (5.19); 120 mins, 64.52 (5.66) vs 46.57 (6.77) for 0.13% vs 0.35%, respectively).

Irrigation with 0.13% diluted povidone-iodine every 30 minutes provides the optimal balance between antimicrobial efficacy against MSSA and minimal cytotoxicity, making it the most effective strategy for preventing PJI during surgery. This study highlights the critical role of timing and frequency in povidone-iodine irrigation for reducing PJI risk.