Does the Application of Topical Vancomycin Reduce Surgical Site Infections in Spine Surgery? A Meta-analysis of Randomized Controlled Trials
Authors: Daher Mohammad , Nassar Joseph E. , McDonald Christopher L. , Diebo Bassel G. , Daniels Alan H. 
Published: July 2024

Background
Surgical site infections (SSIs) represent a major challenge in spine surgery, leading to severe morbidity, mortality, and increased costs. The local application of antibiotics, particularly vancomycin, has emerged as a potential strategy. Individual randomized controlled trials (RCTs) have disagreed about the efficacy of topical vancomycin in preventing SSIs after spine surgery, and so a meta-analysis that pools data from those RCTs might be helpful to inform clinicians’ decisions on the topic.

Questions/purposes
This meta-analysis of RCTs asked: Does intrawound topical vancomycin reduce the risk of (1) SSIs, (2) deep SSIs, and (3) superficial SSIs in patients undergoing spine surgery?

Methods
PubMed, Cochrane, and Google Scholar (pages 1-20) were searched up through March 13, 2024 (search performed on March 13, 2024). Inclusion criteria consisted of English or non-English-language RCTs comparing the implementation of topical vancomycin in spine surgery to its nonuse and assessing its efficacy in preventing SSI, while exclusion criteria consisted of nonrandomized comparative studies, single-arm noncomparative studies, comparative studies based on national databases or from the same center as other included studies, studies posted to preprint servers, studies reporting incomplete/nonrelevant outcomes, and studies adding another SSI preventive measure. The studies were assessed using the Cochrane Risk of Bias tool. Heterogeneity was evaluated by Q tests and I2 statistics. We used a random-effects model when considerable heterogeneity was observed (all SSIs, deep SSIs); otherwise, a fixed-effects model was used (all SSIs subanalysis, superficial SSIs). Furthermore, the fragility index was calculated for each of the assessed outcomes when there was no difference between the two groups to assess how many patients were needed to experience the outcomes for a difference to become present. The studied outcomes were the risks of SSIs, deep SSIs, and superficial SSIs. Deep SSIs were defined by the included trials as SSIs underneath the fascia, otherwise they were considered superficial. Six RCTs representing a total of 2140 patients were included, with 1053 patients in the vancomycin group and 1087 in the control group. Using an alpha of 0.05, our meta-analysis had 80% power to detect a risk difference of 1.5% for the primary outcome between patients who did and did not receive vancomycin. The age of the patients in the vancomycin group ranged from 37 to 52 years, while the age in the control group ranged from 34 to 52 years. The surgical procedures consisted of both instrumented and noninstrumented spinal procedures. Overall, the risk of bias in the included studies was either low or unclear, with none of the studies having a high risk of bias in any of the assessed categories (selection bias, performance bias, detection bias, attrition bias, and reporting bias).

Results
We found no difference in the risk of SSI between the vancomycin and control groups (3.0% [32 of 1053] versus 3.9% [42 of 1087], relative risk 0.74 [95% CI 0.35 to 1.57]; p = 0.43). Ten additional patients (4.8% infection risk) in the control group would need to experience an SSI for a difference to be observed between the two groups. We found no difference in the risk of deep SSI between the vancomycin and control groups (1.8% [15 of 812] versus 2.7% [23 of 860], relative risk 0.69 [95% CI 0.24 to 2.00]; p = 0.50). Seven additional patients (3.5% infection risk) in the control group would need to experience a deep SSI for a difference to be observed between the two groups. We found no difference in the risk of superficial SSI between the vancomycin and control groups (1.0% [6 of 620] versus 1.4% [9 of 662], relative risk 0.68 [95% CI 0.25 to 1.89]; p = 0.46). Seven additional patients (2.4% infection risk) in the control group would need to experience a superficial SSI for a difference to be observed between the two groups.

Conclusion
This meta-analysis of randomized trials examining use of topical vancomycin in spine surgery failed to show efficacy in reducing infection, and thus we do not recommend routine use of topical vancomycin for this indication. Future large-scale trials would be needed if surgeons believe that between-group differences smaller than those for which we were powered here (this meta-analysis had 80% power to detect a between-group difference of 1.5% in infection risk) are clinically important, and large database surveys may be informative in terms of assessing for postoperative adverse events associated with the use of vancomycin powder.

Level of Evidence
Level I, therapeutic study.