Extended oral antibiotic prophylaxis has become increasingly common after knee revision surgery, but two new studies suggest the practice may not be delivering the infection-prevention benefits many clinicians hope for. Presented at the Joint European Bone & Joint Infection Society-Musculoskeletal Infection Society Conference, both studies found no statistically significant reduction in periprosthetic joint infection (PJI) rates among patients who received extended oral antibiotics compared to those who didn't.

In the larger study, Yale's Dr. Ilda Molloy analyzed over 95,000 aseptic revision TKA cases and found PJI rates at 5 years were nearly identical — 8% with extended antibiotics vs. 8.5% without. A separate Hospital for Special Surgery study of 2,181 patients undergoing two-stage reimplantation for TKA found similarly flat PJI-related reoperation rates across 90-day, 1-year, and 2-year windows. Researchers caution that antibiotic use carries real risks, including GI complications, kidney injury, and potential downstream infections.

Key Takeaways:

• PJI rates at 5 years: 8% (with extended antibiotics) vs. 8.5% (without) — not statistically significant
• No significant difference in PJI-related reoperation at 90 days, 1 year, or 2 years in the reimplantation cohort
• Extended antibiotics were linked to lower odds of pneumonia, UTI, and surgical site infections — but these were secondary outcomes in retrospective studies, and should not be interpreted as a reason to prescribe extended prophylaxis routinely

Why it matters: With antibiotic use rising sharply in orthopedic surgery, these findings challenge the assumption that more prophylaxis equals better outcomes. Clinicians are being urged to weigh the risks carefully and reserve extended antibiotic courses for patients with a clear clinical rationale — not as routine practice.