Study challenges ‘5-second rule’ for dropped surgical implants

In kitchens, the “five-second rule” offers a small, comforting fiction—that what falls and is retrieved quickly can be salvaged germ-free. A similar story can surface in surgical settings, where dropped objects are surprisingly common. But a new randomized study suggests that even brief contact with a contaminated surface can affect the sterility of surgical implants and that certain disinfection methods can reduce, but not fully eliminate, contamination. 

In a study published in Infection Control & Hospital Epidemiology, researchers led by a team at the Duke Center for Antimicrobial Stewardship and Infection Prevention examined what happens when orthopedic implants used in joint-replacement surgery are contaminated and then disinfected using different approaches. 

“Studies of operating room contamination consistently demonstrate that surfaces, including floors, are frequently colonized by pathogens, making any dropped item, particularly an implant, potentially dangerous,” the authors write. 

Disinfection reduces, but doesn’t eliminate, pathogens

For the study, the researchers deliberately exposed 213 polyethylene (PE) implant liners from hip or knee implants to contamination by placing them on the operating room (OR) floor where the surgeon had stood for 10 seconds immediately following orthopedic surgery. Floor sponge samples were collected from drop sites to evaluate baseline contamination after liners were dropped. 

Then they divided each implant in half and swabbed one half for bacteria before applying any antiseptic intervention and swabbed the other half after applying either chlorhexidine gluconate (CHG) and alcohol (2% CHG in 70% isopropyl alcohol), povidone and iodine (PI; 10%), or ethanol (EtOH; 70%) as disinfectants. The control consisted of no disinfection.

Both the CHG and PI immersions reduced the pathogens on the implants better than EtOH or the control group. Median bacterial counts fell from 10 (0 to 60) colony-forming units (CFU) before disinfection to 0 (0 to 20) CFU after, with CHG and PI performing similarly and both significantly reducing bacterial counts better than the control. Disinfection with EtOH did not differ from the control and was less effective than CHG or PI. 

Clinically important pathogens were found in 73 of 213 implant liners (34%) before disinfection and 41 of 213 (19%) after. EtOH showed no difference from the control or PI and was less effective than CHG.

When the researchers tested for specific organisms, they found that Staphylococcus aureus levels declined from 22% to 12% with the CHG and PI immersions, while EtOH was much less effective. Enterococcus declined from 16% to 8% without clear differences between the three arms, and Gram-negative organisms were eliminated by all three disinfection methods (but not in the control group). Samples collected from 19 floor sponges showed “substantial baseline contamination” on the OR floor.

Dropped implants should be replaced

The results underscore that even brief exposure to nonsterile environments can introduce microbes that are not easily or fully removed from implants, and that, whenever possible, dropped implants should be replaced rather than disinfected. 

“Even with CHG or PI, disinfection did not guarantee sterility, indicating residual risk,” the authors write. “Therefore, a dropped PE liner should be replaced. If an alternative is unavailable, immersion in sterile CHG or PI is preferable to ethanol or no intervention. Patients should be informed of the event and monitored for signs of infection.”