Postoperative sepsis is a costly and potentially devastating problem in total joint arthroplasty. Airborne bacteria and other viable microorganisms shed from surgical staff are a source of deep prosthetic infection, and the density of airborne bacteria is correlated with the rate of postoperative joint sepsis in total joint arthroplasty surgery. Previous studies have also reported a positive relationship between the density of nonviable airborne particulate and viable CFU counts, both airborne and in the surgical wound, during surgery. The purpose of this study was to determine the extent to which a system that delivers a small field of local, directed HEPA-filtered air flow over the surgical field reduces airborne particulate and airborne bacteria during total hip arthroplasty. A minimum of 8 subjects per group provided 80% power (a = 0.05) to detect a =75% difference in bacterial density between groups. All patients who consented to undergo primary total hip arthroplasty were eligible. Thirty-six patients were prospectively randomized into three groups: directed air flow, air flow system present but turned off (sham), and control (standard) conditions. Airborne particulate and bacteria were continuously collected in consecutive 10 minute intervals within 5 cm of the surgical wound using an air sampling device. Data were analyzed using a generalized linear model for repeated measures. Particulate counts and bacterial density at the surgical site were 80% lower on average in the directed air flow group compared to the other two groups (p<0.001) (Figure 1). Density of particulate >10 μm in diameter was strongly related to bacterial density at the surgical site (p<0.001), as was staff count (p<0.001) and bacterial density at a control site that was remote from the surgical field (p<0.001). The directed air flow system's effectiveness in reducing bacteria appears to be related to its ability to reduce particulate that may carry and allow proliferation of bacteria. The directed air flow system is relatively simple to use and does not appear to hinder the function of the surgeon or operating room staff, impede access to the surgical site, or interfere with the surgical procedure. The directed air flow system can be used in any operating room environment to provide clean air equivalent to a properly-used, well-functioning laminar air flow system. The directed air flow system was effective in reducing airborne particulate and bacteria in the surgical field during total hip arthroplasty.
Prevention of surgical infection following joint arthroplasty is preferable to treatment. Prevention requires identification and control of the potential sources of microbial contamination. The purpose of this study was to determine whether the density of airborne particulate in the operating room during total joint arthroplasty could predict the density of viable airborne bacteria at the surgery site. A standard particle analyzer was used to measure the number and diameters of airborne particulate during 22 joint arthroplasty surgeries performed in non-laminer flow rooms. An impact air sampler and standard culture plates were used to collect airborne particulate and were analysed to identify and count colony-forming units. Particulate density averaged >
500,000 particles/ft3, and 1,786 colony-forming units were identified, primarily gram-positive cocci. The density of particles ≥10um explained 41% of the variation in colony-forming unit density. Colony-forming units and ≥10 um particle density increased with longer surgery duration and higher staff counts. This is the first study to the authors knowledge that shows a correlation between the number of persons in the OR and CFUs at the surgical site during total joint arthroplasty procedures. Increasing surgical staff appear to produce both more particulate and more CFUs. These observations support the use of environmental controls that isolate and protect the surgical site from airborne particulate and microbial contamination. Continuous monitering of particulate larger than 10 um during joint arthroplasty procedures may be warrented.
