Agent Orange in spinal surgery

This week I learned from an orthopaedic surgeon that randomized trials were something that could be of use in “pharmaceutical sciences”, but that it is well-known that in the “surgical science” retrospective analyses are better for deriving evidence. We came to this when discussing the benefits of powdered vancomycin in the wounds of spinal surgery. Apparently this is something “all spinal orthopaedics do”, because it works so good.

In my search for enlightment, I found a recent review, summarizing the evidence on this topic, in which it is also stated that “administration of local intra-wound vancomycin has become a routine practice for many spine surgeons…. despite a lack of high level evidence.” Quoting from thie review: There are 21 controlled studies, but only 1 was performed prospectively as a RCT. 11 of 20 retrospective studies utilized a pre- and post-intervention design without adequately controlling for potential confounders in the historical control group, and control groups in 8 retrospective studies had SSI rates above 11% (!). Most studies did not use a standardized definition for SSI. Fortunately, there are 8 (!!!) meta-analyses since 2014, reporting on the pooled risk for SSI from up to 16 studies; Each meta-analysis found a statistically significant improvement in favor of the use of topical vancomycin (odds ratios for SSI from 0.11 to 0.43), and also identified publication bias, indicating that only positive studies have been reported.

The only RCT was performed from 2011-2012, and included 907 patients who underwent both instrumented and non-instrumented spinal surgery in India, see. All patients received iv cefuroxime for at least 24 hours postoperatively or until drain removal for instrumented procedures. The intervention group also received 1 gram of topical vancomycin introduced into the muscle, fascia, and subcutaneous tissue. SSI rates were 1.68% (control) and 1.61% (treatment group).

6 of 9 retrospective studies (110 to 389 patients) reported a statistically significant reduction in the SSI rate with topical vancomycin, and 2 reported a strong trend in favor of topical antibiotics (Odds ratios from 0.06 to 0.75). However, the 1 study using propensity score matching and accounting for potentially confounding variables demonstrated no difference.

9 of 11 studies using a historical control group demonstrated a statistically significant reductions in SSI with topical vancomycin (Odds ratios from 0.02-0.96). Yet, only a single study of this type accounted for confounding variables.

So, what to do? And what is done in your hospital? I know that some experts in infection control recently started to curse the use of randomized trials in infection control, see. Our lives would be much easier if we would all agree, but something tells me that I should not. Interested to hear if and how your spinal surgeons powder their wounds in your place.

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