Current Aseptic Approaches
Antibiotic administration as well as local application of vancomycin powder at the surgical site are commonly used aseptic practices. However, these techniques do not eliminate surgical site infection and present their own concerns. The authors cited recent global task force exploration of how to mitigate overuse of antibiotics, as well as studies showing increased prevalence of microbial infection for patients who received vancomycin powder as concerns.
Method
The researchers used two types of surgical pedicle screws for the study. One group with intraoperative guards, the other without guards. Five independent hospitals with various surgeons and surgical staff produced 31 samples via 28 surgeries for each of the two surgical screw type groups.
For the study, pre-sterilized, individually packaged pedicle screws were employed (with and without guards). During surgery, screws from both groups were first handled by a scrub tech and loaded into a pedicle screw driver within a sterile field. Next, screws were left for 20 minutes on a sterile surgical tray in the operating room. After approximately 20 minutes, the lead surgeon handled the instrument holding the screw to check its fit into the insertion device. Finally, rather than being implanted, the screw sample was taken with fresh, sterile gloves straight into a sterile container without additional handling.
All surgeries were for degenerative or traumatic spine conditions in patients over 18 years old and all standard procedures were kept otherwise. The 3-step protocol utilized in the study was agreed upon by 50 international orthopedic surgeons. They found 20 minutes to be the shortest time of exposure recorded for use of at least one pedicle screw in their daily surgical practices.
While unguarded screws signify those treated with standard practice of removing the sterile packaging, guarded screws by definition maintain impermeable barriers along their length after removal from sterile packaging. These screw guards are removed just seconds before insertion.
The samples were tested via two culturing techniques; streaking and spectrophotometry. Streaking is used to help identify bacteria type. Spectrophotometry measures opacity when light is shined through the specimen. Bacterial growth in such samples would affect this opacity.
After incubating for 24 hours in a Fisher Scientific rotisserie incubator, the turbidity of samples was measured via spectrophotometry. Also, 0.1 mL from each sample were streaked on agar plates with 5% sheep’s blood and incubated at 36 degrees for 14 days, with turbidity and CFU [colony forming units] counts recorded daily. Samples of positive cultures were sent for specific bacterial identification after this time.
Saturated levels of turbidity were detected on screws without guards within 24-48 hours. However, pedicle screw samples with guards showed no turbidity for the entirety of the incubation period. While unguarded screws had visible CFU presence within 2 hours of initial streaking, plates from guarded screws showed no CFU growth during the 14 day incubation period. Bacteria noted were those most commonly found in surgical site infection, staphylococcus and micrococcus.
The authors noted that these outcomes were consistent across the multiple surgical sites included in this multicenter study. Agarwal told OTW, “the most challenging aspect of this study design was the variability inherent in surgical workflow (in a single hospital and between different hospital groups) and making sure that the exact study method is followed in each hospital (especially when many surgical staff rotate and have to be re-trained, so we literally had to train members before each spine surgery on the data collection process). But given the consistency of the methods of exposure in spine surgery, and no change in the existing work-flow due to the use of guard made comparison very easy.”
