Letter to “Postoperative C-Reactive Protein Trajectories in Spine Surgery - Influence of Vancomycin Powder: A Secondary Analysis of a Prospective Randomized Controlled Trial”

To the Editor,

We read with great interest the article by Lukas F Panzenböck et al ¹ entitled “Postoperative C-Reactive Protein Trajectories in Spine Surgery – Influence of Vancomycin Powder: A Secondary Analysis of a Prospective Randomized Controlled Trial.” The authors should be congratulated for conducting a prospective randomized study evaluating the diagnostic utility of postoperative C-reactive protein (CRP) trajectories for surgical site infection (SSI) surveillance following lumbar fusion surgery. The study provides clinically meaningful evidence supporting postoperative day 7 CRP as a potentially valuable rule-out biomarker for SSI.

Nevertheless, several issues merit further discussion. First, the study did not investigate whether postoperative CRP trajectories differed according to the causative pathogen. Different microorganisms may induce substantially different inflammatory responses. ² High-virulence pathogens such as Staphylococcus aureus often elicit a pronounced systemic inflammatory response, whereas low-virulence organisms, including Staphylococcus epidermidis, may result in only modest CRP elevation despite the presence of clinically significant infection. ³ Consequently, reliance on a single CRP threshold may reduce sensitivity for detecting indolent or chronic infections. Future studies should therefore explore pathogen-specific inflammatory patterns and evaluate combined microbiological and biomarker-based prediction models to improve early diagnosis of low-grade spinal infections.

Second, the duration of postoperative CRP surveillance was limited to the first 7 postoperative days. Although early CRP kinetics may be useful for identifying acute SSI, certain delayed or low-grade infections, particularly biofilm-associated infections, may not become clinically apparent until weeks or even months after surgery. ⁴ As a result, the predictive value of longer-term CRP monitoring remains uncertain. Future investigations incorporating extended longitudinal follow-up, including outpatient assessment at 2 weeks, 1 month, and later postoperative intervals, may help determine whether persistent or secondary CRP elevation improves detection of delayed spinal infections.

In addition, although the study demonstrated that intrawound vancomycin powder did not significantly alter systemic postoperative CRP trajectories, its potential influence on the local immune microenvironment remains insufficiently understood. Locally administered antibiotics may affect cytokine expression, bacterial biofilm formation, microbial ecology, and host inflammatory responses at the surgical site without substantially altering systemic inflammatory markers. Furthermore, concerns remain regarding the possible development of antimicrobial resistance and the potential effects of high local vancomycin concentrations on bone healing and fusion biology. ⁵ Future studies integrating local tissue biomarkers, microbiological profiling, and radiographic fusion assessment may help clarify the broader biological implications of intrawound vancomycin use in spine surgery.

Overall, this study contributes valuable prospective evidence regarding postoperative CRP monitoring after lumbar fusion surgery. Further validation in larger multicenter cohorts with standardized SSI definitions and comprehensive longitudinal biomarker follow-up will be important to determine whether CRP-guided surveillance algorithms can improve early SSI detection while minimizing unnecessary antibiotic exposure.