Diluted Povidone-Iodine Irrigation for Prevention of Implant-Related Infection: A Comparative Analysis of Concentration and Frequency in a Rat Model.

Abstract

Background: Povidone-iodine (PVI) irrigation is widely used to reduce surgical site infection risk; however, the appropriate concentration and timing remain uncertain. We evaluated how the PVI concentration and irrigation interval influence the early bacterial burden and tissue response in a rat model of implant-related infection.

Methods: Female rats received a stainless steel plate contaminated with methicillin-susceptible Staphylococcus aureus . The rats were randomized to receive 0.13% PVI, 0.35% PVI, or normal saline solution irrigation every 30 or 60 minutes during a 60-minute procedure. Irrigation consisted of a 3-minute exposure followed by a saline solution rinse. Outcomes included the bacterial count after sonication, soft-tissue infection score, peri-implant bone mineral density (BMD) on microcomputed tomography (µCT), histological inflammation grading, and body weight trajectory.

Results: Higher PVI concentrations and a shorter irrigation interval were associated with reduced recoverable bacterial burden. Among the 30-minute interval groups, no culturable bacteria were recovered in the 0.35% PVI group (i.e., the values were below the assay detection limit); in contrast, culturable bacteria were detectable in all of the 60-minute interval groups. PVI-treated rats demonstrated lower macroscopic infection scores and a trend toward more rapid body weight recovery compared with saline solution controls. For both irrigation intervals, µCT showed higher peri-implant BMD in the PVI-treated groups than in the saline solution controls. Histology showed less inflammation and fewer abscesses in the PVI-treated groups compared with controls, with the least inflammation observed in the group that received 0.35% PVI at 30-minute intervals.

Conclusions: In this rat model, PVI concentration and irrigation interval were associated with early differences in bacterial recovery and peri-implant tissue and bone responses. These findings are hypothesis-generating and should be interpreted as mechanistic, preclinical signals rather than as guidance for clinical practice. Further translational and clinical studies are needed to determine the relevance of these signals in humans.

Clinical relevance: Current practice typically involves a single 3-minute 0.35% PVI soak before wound closure. This study provides preclinical mechanistic data on how PVI concentration and irrigation timing influence early bacterial recovery in an implant-related infection model. The findings do not support changes to clinical protocols, but highlight the need for careful evaluation of cytotoxicity and safety.