Introduction Periprosthetic infection is one of the most severe complications following implant-based breast reconstruction affecting 5%–10% of the women. Currently, many surgeons apply antibiotics locally on the breast implant to reduce the risk of postoperative infection, but no randomised, placebo-controlled trials have tested the treatment’s efficacy. Methods and analysis The BREAST-AB trial (BREAST-AntiBiotics) is an investigator-initiated, multicentre, randomised, placebo-controlled, double-blind trial of local treatment with gentamicin, vancomycin and cefazolin on breast implants in women undergoing implant-based breast reconstruction. The trial drug consists of 80 mg gentamicin, 1 g vancomycin and 1 g cefazolin dissolved in 500 mL of isotonic saline. The placebo solution consists of 500 mL isotonic saline. The trial drug is used to wash the dissected tissue pocket and the breast implant prior to insertion. The primary outcome is all-cause explantation of the breast implant within 180 days after the breast reconstruction surgery. This excludes cases where the implant is replaced with a new permanent implant, for example, for cosmetic reasons. Key long-term outcomes include capsular contracture and quality of life. The trial started on 26 January 2021 and is currently recruiting. Ethics and dissemination The trial was approved by the Regional Ethics Committee of the Capital Region (H-20056592) on 1 January 2021 and the Danish Medicines Agency (2020070016) on 2 August 2020. The main paper will include the primary and secondary outcomes and will be submitted to an international peer-reviewed journal. Trial registration number NCT04731025 .

Background: Antibiotic implant irrigation is increasingly used to prevent deep infection after implant-based breast reconstruction. However, there is limited evidence of the clinical effect. In this study, the authors compare the risk of a deep infection in a Danish population of women who received antibiotic implant irrigation with either gentamicin or vancomycin, or no irrigation. Methods: The authors retrospectively reviewed consecutive patients undergoing all types of breast reconstruction with implants at Rigshospitalet and Herlev Hospital, Denmark, from 2010 to 2019. Logistic regression was used to compare the risk of deep infection between no irrigation and irrigation with gentamicin or vancomycin, and to account for the difference in risk between patient subgroups and risk factors. Results: The authors included 1508 patients who received antibiotic irrigation with gentamicin (500 patients), vancomycin (304 patients), or no irrigation (704 patients). The univariable risk analysis showed a significant decreased risk of deep infection using gentamicin irrigation compared with no irrigation (OR, 0.58; P < 0.05). However, when adjusting for risk factors for infection, there was no significant decrease in the risk of infection when using gentamicin (OR, 0.90; P = 0.71) or vancomycin (OR, 1.0; P = 0.99) compared with the control group. Conclusions: The authors found no significant effect of using antibiotic implant irrigation after isolating it from risk factors for deep infection. However, because of the limitations of the study, the authors cannot conclude that there is no effect of antibiotic implant irrigation. There is a need for a randomized, placebo-controlled trial to investigate the effect, and potential side-effects, of antibiotic implant irrigation.