Dealing With Positive Cultures After Revision Spine Surgery You Thought Was “Aseptic”

Unexpected intraoperative positive cultures are much more common than you might realize — and when you find one, things really get tricky

What’s the Claim?

A meta-analysis found that unexpected intraoperative positive cultures (UIPCs) were extremely common after revision spine surgery believed to have been performed for aseptic indications. A bunch of claims made in this paper didn’t withstand scrutiny, but the few that did justify sharing — about one in four adults will have a UIPC, and about four in 10 children will (big caveat on this one, more in a moment). Although there were not enough infections to determine whether a UIPC is likely to cause infection, the two most-common organisms the source articles cultured — C. acnes and coagulase-negative Staphylococcus — have turned out to be problematic pathogens in revision hips, knees, and shoulders. For this reason, as much as any other, we’re sharing what otherwise is mainly a descriptive study.

How’s It Stack Up?

The finding that 43% of children undergoing revision spine surgery had a UIPC may be higher than it really is — it was based on only two studies in this meta-analysis, and both of them evaluated the same operation: surgery for early-onset scoliosis with vertical expandable prosthetic titanium rib (VEPTR) implants. Those involve multiple, planned procedures to expand the prosthesis, and so a higher risk of infection might be expected there. We’d put caveats on a number of other claims made here. For example, the suggestions that sonication yielded more positive cultures and that C. acnes was more common than coagulase-negative Staphylococcus were not borne out by the statistics (both had broadly overlapping 95% CIs). Still, the finding that one in four adults undergoing revision spine surgery will have a UIPC was robust, as was the observation that the two main bugs were the ones named. Because one of them is C. acnes, the finding that UIPCs are more common in males also makes sense, since males tend to harbor C. acnes more than females.

What’s Our Take?