Thorough debridement is mandatory in revision for infected total knee arthroplasties (TKA). We investigated a novel adjuvant chemical debridement strategy using acetic acid (AA) that seeks to create a hostile environment for microorganisms. We report the first orthopedic in vivo series using an AA soak in infected TKAs. We also investigated the in vitro efficacy of AA against bacteria isolated from these knees.
Twenty-three patients with infected TKA were treated with a standard debridement protocol and chemical debridement with a 20-minute AA soak. In parallel, bacteria from infected TKAs were cultured for in vitro susceptibility testing with AA solutions of different concentrations to understand its potential mechanism of action.
Intraoperatively, there were no physiological responses during the AA soak or on release of the tourniquet. Postoperatively, there was no increase in analgesic requirements or wound or soft-tissue complications. Clinical follow-up continued for 24 months to monitor recurrent infection. In vitro, zones of inhibition were formed on less than 40% of the organisms, demonstrating that AA was not directly bactericidal against the majority of the isolates. However, when cultured in a bacterial suspension, AA completely inhibited the growth of the isolates at concentrations as low as 0.19% vol/vol.
This study has shown that the use of 3% AA soak, as part of a debridement protocol is safe in patients. While the exact mechanism of action is yet to be determined, AA concentrations as low as 0.19% vol/vol in vitro are sufficient to completely inhibit bacterial growth.