Intrawound Antibiotics: Infections in Lower-Limb Trauma Surgery and a Potentially Misleading Claim

What’s the Claim?

The authors of this study used RCTs, cohort studies, and case-control studies to evaluate whether using intraoperative antibiotic powder plus the usual IV antibiotic routine reduced the rate of deep surgical site infections in patients undergoing pelvic or lower-limb trauma surgery compared to routine IV antibiotics alone. They claimed a “potential” reduction in the odds of infection associated with using antibiotic powder, but we are skeptical: They seemed to ignore their own statistical analyses in order to make this claim.

How’s It Stack Up?

Bringing together diverse sources like this is worth doing when the event of interest is uncommon to rare, and we are big fans of a well-done meta-analysis. On this topic, in particular, studies that aggregate or pool data (like systematic reviews and meta-analyses) are going to be important. Infections are uncommon enough that typical primary study designs (like case series and even randomized trials) are likely to be underpowered to test the treatment fairly, so we’re glad that the authors did this study. Earlier meta-analyses that included lower-quality studies on this topic suggested antibiotic powder is effective; this study, which looked at higher-quality studies, did not. It’s often true that better study quality results in smaller effect sizes or no-difference findings, and that seemed to be the case here.

What’s Our Take?

The authors’ claim of a “potential 23% reduction" in the odds of deep infection in patients treated with intraoperative antibiotic powder came with this caveat:
“although the results did not reach statistical significance.” This does not withstand scrutiny, and we recommend against applying this finding to your patients. The authors’ actual data suggest that the impact of antibiotic powder could range from a 48% reduction in odds (in other words, the stuff is even more effective than claimed) to a 13% increase in the odds of infection associated with use of antibiotic powder—that’s right, a very real possibility that the treatment actually made things worse. Claims like “did not reach statistical significance” should put your antennae up. Data don’t have volition; they’re not trying to “reach” significance. A no-difference finding is a no-difference finding. The fact that they found no difference in 3600 patients analyzed makes it likely that, in fact, there is no difference.

Source

Ma N, Gogos S, Moaveni A. Do Intrawound Antibiotics Reduce the Incidence of Surgical Site Infections in Pelvic and Lower-Limb Trauma Surgery? A Systematic Review and Meta-analysis. J Orthop Trauma. 2022;36:e418-e424.

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