Background: The risk of periprosthetic joint infection (PJI), a serious complication after arthroplasty, has not changed for years. Interventions such as eradication of Staphylococcus aureus and antibiotic bone cement are used to diminish infection risk but despite these efforts, the percentage of infection in TKA remains constant. Antimicrobial drapes have a dual action, acting both as a physical and antimicrobial barrier to counter bacterial contamination of the surgical wound. To study the effect of antimicrobial drapes, we used intraoperative contamination as a proxy for infection in our investigation.
Questions/purposes: (1) Do antimicrobial surgical drapes reduce the risk of intraoperative microbial contamination in patients undergoing primary knee arthroplasty? (2) Are other factors such as sex, season, age, type of arthroplasty and duration of surgery associated with an increased risk of contamination in patients undergoing primary knee arthroplasty? (3) Does loosening of the antimicrobial drape increase contamination risk?
Methods: An investigator-initiated, two-arm, non-blinded, multicenter, randomized, controlled trial was performed at five different hospitals in the capital and central regions of Denmark. Twenty-four surgeons participated in the study. Participants were patients older than 18 years undergoing primary knee arthroplasty. We excluded patients with an iodine allergy, previous open knee surgery, previous septic arthritis, any antibiotics taken 4 weeks before surgery, and if they were unable to understand the implications of study participation. Patients were randomly assigned to operation with an antimicrobial drape (intervention group) or operation without (control group). We screened 1769 patients, of which 100 were ineligible and 10 declined to participate. In all, 94% (1659 of 1769) of patients consented and were randomized to the intervention group (51%, 838 of 1659) and control group (49%, 821 of 1659), respectively. In all, 36% (603 of 1659) of patients in the intervention group and 35% (584 of 1659) patients in the control group were available for final analysis. No crossover was performed, and analysis was done per-protocol. Patients were excluded due to logistic failures like lack of utensils, samples disappearing en route to the laboratory mainly caused by implementation of a new electronic patient chart (EPIC, Verona, WI, USA), and forgetful surgeons. Intraoperatively, we swabbed for bacteria at the surgical site and in a rinse from the surgeons' gloves. All samples were sent for cultivation, and colony forming units (CFUs) counts ≥ 1 were deemed contaminated. The primary outcome measure was the difference in the proportion of contaminated patients between the two randomized groups. Secondary outcome measures were the affiliation of sex, season, age, type of implant used, and duration of surgery on contamination risk. To investigate whether other factors were affiliated with contamination risk, we did a logistic regression to control for confounding variables, including sex, age, season, type of implant and duration of surgery.
Results: Use of iodinated drapes reduced contamination, with contamination detected in 10% (60 of 603) procedures where iodinated drapes were used compared with 15% (90 of 584) when they were not (odds ratio 0.61 [95% CI 0.43 to 0.87]; p = 0.005), with a relative risk reduction of 35% (95% CI 12.3 to 52.5) and a number needed to treat of 18 patients. After controlling for confounding variables such as sex, age, type of implant, and duration of surgery, we found that not using an antimicrobial drape increased contamination risk by a factor of 1.6 (95% CI 1.08 to 2.35; p = 0.02). Female sex and undergoing surgery in the central region were associated with lower odds of contamination (OR 0.55 [95% CI 0.39 to 0.8]; p = 0.002 and OR 0.45 [95% CI 0.25 to 0.8]; p = 0.006, respectively). Patients with more than a 10-mm separation of the drape from the skin had higher odds of contamination (OR 3.54 [95% CI 1.64 to 11.05]; p = 0.0013).
Conclusions: The use of an antimicrobial drape resulted in lower contamination risk than operating without an antimicrobial drape. Our findings suggest that antimicrobial drapes are useful in infection prevention, but further studies are needed to investigate the effect of antimicrobial drapes on infection.
Level of evidence: Level I, therapeutic study.