In the emergency room, a doctor typically treats an open wound with broken bone by first washing it with high-pressure water to blast away debris, then rinsing the wound with soap and water to wash away bacteria and other microbes. Yet nearly half of individuals with a severe fracture wind up back in the hospital with an infection.

Now, a large international study, published in the New England Journal of Medicine, has upended the conventional wisdom about cleaning wounds. Forget the soap, the authors say. The best way to clean a fracture wound is with sterile salt water, called saline. The study also found that very low-pressure water is just as effective as a high-pressure rinse.


"Despite the perception that soap should work — an idea that has been indoctrinated into our culture — it doesn't necessarily apply to open wounds," says study author Mohit Bhandari, professor and head of orthopedic surgery at McMaster University in Ontario, Canada. "We believe the findings to be closer to the truth than previous studies. If we had not done this, we'd still be prompting therapies that don't work."

Smaller past studies found high pressure and soap to be the most effective for cleaning wounds. Even Bhandari's own 2011 trial of 100 people concluded that soap was slightly better than saline. He and colleagues at McMaster decided to organize a larger, definitive study. "Smaller trials have a risk of being wrong," says Bhandari. "It was possible our smaller study was just a chance finding. One way to find out was to do a much bigger trial."

So they went big. A team of 250 surgeons at 41 locations around the world, including in Australia and India, combined resources to treat over 2,400 patients with open arm or leg fractures, most commonly from car accidents. Each patient was randomly chosen to have his or her wound cleaned with either soap and water or saline alone, and at one of three different water pressures: high, low, and very low. The team then monitored the patients for 12 months and recorded who returned to the hospital for additional surgery, which is most often due to infection and poor healing.


Surprisingly, patients in the soap group were more likely to return for another operation. The high-pressure wash patients also fared no better than the ones who got a low or very-low pressure wash. That is valuable information for doctors in rural areas and developing countries, says Bhandari: Gently pouring water over a wound is an acceptable, low-cost alternative to spraying a wound with an expensive water gun.

The jury is still out on why saline water worked better than soap, but one possibility is due to soap's "rebound effect." Within two or three days after cleaning a wound with soap, many of the bacteria return with a vengeance, stronger and more abundant than before. Researchers don't yet know why.

For now, doctors who participated in the trial are presenting the results at hospitals worldwide, working to change the current wisdom on how to treat open fracture wounds. The findings may also apply to other types of injuries, says Bhandari. "I imagine anyone dealing with an open wound could benefit from this approach," he says, though it will require further testing.