One hundred eighty-four patients undergoing primary total joint arthroplasty (92 hip and 92 knee cases) were randomized to receive either standard perioperative antibiotic prophylaxis (n=92) or extended oral antibiotic prophylaxis with levofloxacin for 14 days postoperatively (n=92). The primary outcome was the 90-day postoperative incidence of periprosthetic joint infection (PJI). Secondary outcomes included EOA-related complications and cost-effectiveness. The study revealed an identical 90-day PJI incidence of 1.09% (1/92) in both groups, with knee patients showing a 2.17% incidence and no infections observed in hip patients. No EOA-related complications were reported, and the cost-effectiveness model suggested that 333 patients would need EOA to prevent one case of PJI. Overall, the study concluded that EOA did not reduce PJI incidence in high-risk TJA patients within 90 days.