Withholding Prophylactic Antibiotics Improves Culture Yield in Revision Total Knee Arthroplasty for Periprosthetic Joint Infection with Negative Aspirations: A Multicenter Retrospective Study.

BACKGROUND Pre-incision antibiotic prophylaxis reduces infection risk in total knee arthroplasty (TKA), but its role in revision procedures for periprosthetic joint infection (PJI) remains uncertain. Early antibiotic administration may suppress culture yield or alter concordance with preoperative aspiration, potentially leading to false-negative results that complicate postoperative antimicrobial selection. METHODS This retrospective multicenter study identified 576 chronic knee PJI patients who underwent two-stage exchange arthroplasty with a minimum of 1-year follow-up. A PJI was defined using the 2013 Musculoskeletal Infection Society criteria. Patients who did not have preoperative synovial aspirations or who were receiving outpatient antibiotic treatment within two weeks of aspiration or revision surgery were excluded (n = 182). Preoperative synovial aspirate cultures, intraoperative tissue cultures, and antimicrobial prophylaxis regimens were recorded. Antibiotic prophylaxis was administered before incision in 49% and withheld in 51%. Pearson Chi-square tests and one-way analyses of variance were used to determine whether antibiotic timing affected culture yield, proportion of positive culture results, and concordance with prior synovial aspirate results. RESULTS Intraoperative culture positivity was similar between early and delayed antibiotic groups (63 versus 63%, P = 0.960), regardless of antibiotic class. Aspirate-to-tissue concordance was also comparable (85 versus 80%, P = 0.225). Among patients who had positive preoperative aspirates, intraoperative culture yield was unaffected by antibiotic timing (89 versus 87%, P = 0.531). However, in those who had negative preoperative aspirations, withholding antibiotics significantly improved culture yield (49 versus 29%, P = 0.015). The number of intraoperative samples was not associated with culture positivity. CONCLUSIONS The timing of antibiotic prophylaxis does not influence overall intraoperative culture yield or aspirate concordance in revision TKA for PJI. However, in patients who have negative preoperative aspirations, withholding antibiotics significantly improves the likelihood of identifying a pathogen. Surgeons should consider delaying prophylaxis in this subgroup to optimize microbiologic diagnosis.