Association of Extended Oral Antibiotic Prophylaxis With 90-Day Complication Rates After Primary Total Knee Arthroplasty: A Propensity-Matched Retrospective Cohort Study.

BACKGROUND: While perioperative antibiotic prophylaxis has been widely implemented to reduce periprosthetic joint infection (PJI) rates, the efficacy of an extended oral antibiotic prophylaxis (EOAP) regimen postoperatively remains equivocal among arthroplasty surgeons. This study investigated the association of EOAP with PJI rates after primary total knee arthroplasty (TKA) using a large database and propensity-matched cohorts. METHODS: A retrospective analysis using a national database stratified primary TKA patients into two cohorts: those who had and did not have a qualifying oral antibiotic medication event on postoperative day one. Patients were propensity-score matched for age, sex, and medical comorbidities. A subgroup analysis of lower-risk patients excluded patients who had diabetes mellitus, chronic kidney disease, and liver disease. Primary 90-day outcomes included PJI and superficial skin infection (SSI), with revision as a secondary outcome. RESULTS: At 90 days postoperatively, EOAP-exposed patients showed a significantly higher rate of PJI (1.99 versus 0.72%, P < 0.0003) and revision (0.7 versus 0.44%, P = 0.0039), but not SSI (0.38 versus 0.36%, P > 0.999). Kaplan-Meier analysis supported significantly reduced infection-free survival in EOAP-exposed patients for PJI (P < 0.0001), and revision (P = 0.0027), but not SSI (P > 0.999). In the lower-risk subgroup, EOAP-exposed patients demonstrated a significantly higher rate of PJI (1.52 versus 0.50%, P < 0.0003), but not SSI (0.32 versus 0.34%, P > 0.999) or revision (0.61 versus 0.36%, P = 0.0627). Kaplan-Meier analysis showed significantly higher rates of PJI (P < 0.0001) and revision (P = 0.0484), but not SSI (P > 0.999). CONCLUSION: In an analysis of 34,584 patients, EOAP was associated with a significantly increased risk of PJI and revision surgery, supported by Kaplan-Meier analysis. Subgroup analysis of lower-risk patients upheld these results in PJI. Prospective studies are required to further evaluate EOAP's efficacy in preventing post-TKA complications.