Abstract
Dear editor,
We read with interest the article “Comparison of Surgical Site Infection After Instrumented Spine Surgery in Patients With High Risk of Infection According to Different Antibiotic Prophylaxis Protocols: A Cohort Study of 132 Patients With a Minimum Follow-Up of 1 year” by Ferrer Pomares et al 1 published in Global Spine Journal. In an observational cohort study, they aimed to investigate the impact of different preoperative antibiotic prophylaxis regimens on postoperative infection rates in patients at high risk of infection undergoing instrumented thoracolumbar spine surgery and concluded that long-term prophylaxis with dual antibiotic therapy with cefazolin and amikacin was associated with a statistically significant reduction in the incidence of surgical site infections (SSIs) in patients at high risk of infection. We acknowledge the work of the authors and appreciate the objective discussion of their findings, including some of the inherent limitations noted. However, after extensive discussion with our professional peer group, we have several salient and pertinent questions that we hope you will address:
First, the aim of this study was to assess the effectiveness of preoperative antibiotics in the control of SSIs after spinal surgery, but there were no studies examining the various concentrations of cefazolin and amikacin in plasma and tissue. This lacks an objective indicator of the effect of actual antibiotic concentrations during spinal surgery on the incidence of SSIs. Notably, Sheikh et al 2 who used high pressure liquid chromatography to determine the actual concentrations of antibiotics achieved during ongoing spinal surgery and ultimately found that serum and tissue concentrations of antibiotics during spinal surgery were significant predictors of SSIs. Therefore, we suggest that the authors could add intraoperative drug level monitoring for preoperative antibiotic surgical prophylaxis in patients undergoing instrumented spinal surgery, and that further studies are necessary in an attempt to establish an equivocal relationship between drug concentrations and the occurrence of SSIs.
Second, we would like to draw the authors’ attention to the latest findings in the field, which are somewhat controversial with the authors’ viewpoint mentioned in the Discussion section, ie, “The main cause of SSI following operations is bacterial contamination of the surgical site during procedures”. According to recent studies, in current surgical practice using standard infection precautions, pathogens causing SSI following instrumented spine surgery are largely attributable to pre-existing strains of organisms from the patient’s resident microbiota. 3
In addition, patients in this study who were allergic to cefazolin chose to use vancomycin as an alternative option. However, the vast majority of patients reporting allergy to cefazolin are not truly allergic and have been found to have a 50% increased chance of SSI due to the use of alternative surgical prophylaxis such as vancomycin. 4 We therefore suggest that the authors could perhaps have included allergy to cefazolin as an exclusion criterion in this study, thereby reducing the impact of confounding factors on the credibility of the findings.
Finally, we again thank Ferrer Pomares and his colleagues for an important study. We believe that discussion of these issues will enhance the reader’s understanding and improve the design of subsequent studies.
