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Saline Better than Soap for Wound Cleaning in Open Fractures

October 08, 2015

By Gene Emery

NEW YORK - Researchers have uncovered a dirty little secret for cleaning open wound fractures - soap isn't as good as saline. Neither are the costly machines that deliver the solution at high pressure.

A new study found that the risk of reoperation to treat a wound infection or to promote wound or bone healing increased 32% when soap was used instead of regular saline (P=0.01).

The researchers, reporting in the New England Journal of Medicine online and at the Orthopaedic Trauma Association annual meeting in San Diego, also found that putting the fluid under pressure to assist in cleaning offered no benefit.

Just letting the fluid flow over the wound worked just as well.

"The soap-and-saline finding is really the surprise," coauthor Dr. Brad Petrisor of McMaster University told Reuters Health by phone. "If you look at all the basic science data and the smaller randomized studies, the evidence suggests that soap would be the better. But when you look at just over 2,400 randomized patients, it looks like soap is detrimental and saline was the best at getting out the bugs without damaging the bone."

The reason is unclear, he said.

Doctors were also expecting that pressure washing would clean the wound better.

"When you wash out the wound with the (pressure) gun, it's satisfying. But when you see there's no difference, that's huge" because it means such equipment isn't necessary in resource-limited countries, Dr. Petriso said. Higher pressure might also damage the architecture of the bone.

The pressure findings do not apply to soft tissue wounds, he said. "High pressure would be the standard there."

When the bone breaks the skin, "the most effective technique for irrigation has been widely debated," said Dr. Douglas Dirschl of the University of Chicago in a Journal editorial. Despite some evidence to the contrary, high pressure is used more often.

He said the new study "represents the most substantial contribution to medical knowledge in these areas to date."

Known as FLOW, the research was conducted at 41 sites in the U.S. Canada, Australia, Norway and India, looking at open fractures of the extremities, clavicle and scapula but excluding fractures of the hand, toes, axial skeleton and pelvic ring.

Reoperation was required within 12 months in 13.2% of the 826 patients whose wounds were cleaned by washing with a pressure of >20 psi, 12.7% of the 809 patients where the pressure was 5 to 10 psi, and 13.7% of 812 when the pressure was 1 to 2 psi and gravity carried the fluid over the wound (all P values equal to 0.53 or higher for head-to-head comparisons).

The reoperation rate was 14.8% in the group using a 0.45% solution of castile soap, compared to 11.6% with saline (P=0.01).

The test focused "on an outcome of unequivocal importance to patients and health can providers (reoperation) and the findings indicate that the differences noted in prior experimental studies do not translate into differences in important outcomes in clinical practice," Dr. Dirschl said.

Using a pressure machine cost about $50 per procedure, Dr. Petrisor said.

"Our findings may be particularly relevant for low-income and middle-income countries, in which 90% of the road traffic fatalities globally, and probably a similar percentage of open fractures, occur," he and his colleagues wrote. "In such contexts, the knowledge that there is no benefit to the use of irrigation-pressure devices can guide the allocation of limited resources - a result that is also very important for the management of open fractures in combat settings."

The U.S. Department of Defense was one of the sponsors of the study.


N Engl J Med 2015


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