Timing of antibiotic prophylaxis for primary total knee arthroplasty performed during ischemia

Background. There is no clinical trial analyzing the best moment to infuse an antibiotic during knee arthroplasty performed during ischemia. We designed a single-center, randomized, double-blind, placebo-controlled trial to evaluate whether antibiotic therapy should be administered before tourniquet inflation or just before tourniquet deflation. Material and methods. Patients who underwent a primary knee arthroplasty were randomized to receive (1) 1.5 g of cefuroxime 10-30 min before inflation of the tourniquet and placebo 10 min before release of the tourniquet (standard arm) or (2) placebo 10-30 min before inflation of the tourniquet and 1.5 g of cefuroxime 10 min before release of the tourniquet (experimental arm). In both arms, a postoperative dose of 1.5 g of cefuroxime was given 6 h after the surgical procedure. The main variables associated with the rate of deep-tissue infection after 3 and 12 months of follow-up were gathered. Continuous variables were compared using Student's t test, and categorical variables were compared using the x 2 test or Fisher's exact test. Results. From September 2004 through December 2005, a total of 908 patients were randomized, 442 and 466 of whom were allocated to the standard and experimental arms, respectively. There were no differences between treatment arms in terms of age, sex, comorbidity, American Society of Anaesthesiologists score, duration of surgery, need of blood transfusion, or fourth-day hematocrit. The rates of deep-tissue infection among the standard and experimental groups were 3.4% and 1.9%, respectively, at 3 months of follow-up (P = .21) and 3.6% and 2.6%, respectively, at 12 months of follow-up (P = .44). Conclusion. The administration of prophylactic antibiotics just before tourniquet release was not inferior to standard antibiotic prophylaxis.