Tehran University of Medical Sciences Journal of Orthopedic and Spine Trauma 2538-2330 10 1 2024 04 01 19 24 Pezhman Shahbazi Hamadan university of medical science Gholamreza Ghorbani Amjad 0000-0000-0000-0000 2023 06 02 2024 03 13 Background: One of the proposed methods to reduce the risk of infection after joint replacement is the use of disinfectant solutions at the end of the surgery. Differing results have been reported regarding the effects of diluted povidone-iodine (betadine) washing solution and normal saline in reducing the risk of periprosthetic joint infection (PJI). The purpose of this retrospective cohort study is to compare the outcomes of diluted betadine solution with normal saline in bilateral knee replacement surgery. Methods: Patients who were referred to Ba’ath Hospital, Hamedan, Iran, from 2019 to 2021 for bilateral knee joint replacement were included. For each patient, one knee was washed with diluted betadine (35%), and the other with normal saline for 3 minutes before closing the wound. Demographic information, risk factors, and the rate of PJI three months after were collected and analyzed. Results: Out of 320 patients, 177 (55.3%) were women, and the most common underlying disease was type 2 diabetes with a frequency of 20.0%. Out of 640 operated knees, 17 cases (2.7%) of PJI occurred after surgery, of which 11 (4.3%) were washed with normal saline (P = 0.326). The multivariate regression analysis showed that being male (P = 0.028), diabetes (P = 0.030), high blood pressure (P = 0.019), and an increase in each body mass index (BMI) unit (P = 0.030) increased the chance of infection.  Conclusion: Intraoperative irrigation with diluted betadine solution in bilateral knee replacement surgery can reduce the risk of infection, especially in patients with underlying diseases and obesity. https://jost.tums.ac.ir/index.php/jost/article/view/499 https://jost.tums.ac.ir/index.php/jost/article/download/499/356