Published 6/1/2011
Peter Pollack

How pertinent is the “6-hour rule”?

Well-accepted rule has a place in open fracture management, but does evidence support it?

The so-called “6-hour rule” is a long-accepted guideline for dealing with open fractures. In essence, the rule states that, to prevent infection, open fractures should be fully managed within a 6-hour time frame. But is this rule supported by any evidence, and is it still relevant in an era of modern wound management and antibiotics?

Speaking at the Orthopaedic Trauma Association meeting on Specialty Day, Mark A. Lee, MD, traced the history of the rule and its importance to modern orthopaedics.

More historic than evidential
“The origins of the 6-hour rule are not really clear,” said Dr. Lee. “The closest starting point is a reference to an 1898 study using a forelimb wound model in a guinea pig that showed increased infection rates after 6 hours of delay. Recent military studies have examined timing and rates of infection, but the take-home point is that the 6-hour rule seems to come out of the air, and it’s probably not that useful in our practices.”

Dr. Lee explained that a more pertinent question is whether or not elective delay is reasonable when dealing with open fractures. The evidence for or against, he admitted, remains weak, but he warned against taking a “cavalier attitude” toward delaying débridement.

“The randomized, prospective study that would help us is probably not going to happen,” he said. “The current evidence isn’t specific to open fractures, but it does provide some practical considerations that can help with the day-to-day management of these injuries.”

Dr. Lee cited a study conducted by Anthony G. Gristina, MD, which examined implant-related infections connected to biomaterials.

“The Gristina study looked at the process of infection,” he said. “It pointed out that infection proceeds in stages, through bacterial adhesion and colonization and then infection. Most significantly, this is a time-dependent process. Early on, the attachment of bacteria to implant is nonspecific and weak, but over time the interactions become more specific and stronger.

“Of course, an open fracture isn’t really a biomaterial, but what we’re looking at in trauma and open fracture is devitalized bone, which has no periosteum, limited blood flow, and a situation that, to my mind, is optimized for infection.”

Dr. Lee said that indirect evidence regarding timing of the infection path can be found in a number of studies on lavage and clearance. In one such study, researchers took transverse sections of tibias and inoculated them with Staphylococcus aureus or Escherichia coli to examine the efficacy of high- and low-pressure lavage at removing bacteria from those bone specimens. At 3 hours after introduction of the bacteria, both high- and low-pressure lavage were effective, but at 6 hours, only high-pressure lavage removed the bacteria.

“This too, suggests that the bacteria were gaining adhesion over time,” said Dr. Lee.

A sense of urgency
According to Dr. Lee, studies that have attempted to directly assess time to wound management in relation to infection have collectively been inconclusive. Data from the military have suggested that time to débridement has a significant effect on likelihood of infection, while a subset analysis from the Lower Extremity Assessment Project (LEAP) study found no significant correlation between ultimate infection and time to débridement. Both sets of data, Dr. Lee pointed out, generally dealt with more severe injuries than are commonly seen in emergency departments, and the most available studies are Level 2 or Level 3 evidence at best.

Given the lack of direct evidence, Dr. Lee encouraged his colleagues to maintain a sense of urgency in open fracture management.

“Wound complexity is variable and very difficult to assess outside the operative theater,” he said. “Many of us have experienced finding debris hidden deep inside what appear to be very simple fracture-related wounds. Any foreign material inside a wound could be a severe nidus for infection, and you can’t prevent that if you haven’t found it.

“In summary, indirect evidence suggests that colonization and infection is time-dependent and related to adhesion, but I don’t think we have evidence to support any specific timing. I don’t believe the 6-hour rule is a strict number. But because undetected contamination is common and problematic in many open fracture wounds, open fractures should generally be débrided at the first reasonable opportunity.”

Disclosure information: Dr. Lee—Biomet, Smith & Nephew, Synthes, Zimmer.

Peter Pollack is a staff writer for AAOS Now. He can be reached at ppollack@aaos.org

Bottom Line

  • Little evidence exists to support the 6-hour rule as a hard limit.
  • Infection is a time-dependent process, and removing bacteria becomes more difficult over time.
  • A sense of urgency should be maintained when dealing with open fractures.