Letter to the Editor,“What is the Evidence Supporting Osteobiologic Use in Revision Anterior Cervical Discectomy and Fusion?”

Dear Editor,

I read with great interest the recent review by Muthu et al, which thoroughly summarizes the current evidence on osteobiologic use in revision anterior cervical discectomy and fusion (ACDF). ¹ Their clear identification of gaps in comparative clinical data is both timely and valuable for guiding future research in this challenging field.

I would like to contribute an additional perspective regarding an emerging factor that may influence outcomes in revision ACDF—occult low-grade infection, most commonly due to Cutibacterium acnes. Recent series have demonstrated that up to 40% of anterior cervical pseudarthrosis revisions harbor occult infection despite appearing clinically aseptic, and colonization.^2-4 These infections are often overlooked because they do not present with fever, wound redness, or elevated inflammatory markers, yet they interfere with bone healing and may explain why some patients fail to improve clinically despite achieving radiographic fusion. In cervical spine surgery specifically, C. acnes is frequently isolated, reflecting its biofilm-forming ability on implants and hardware. The presence of biofilm protects bacteria from both host immune response and standard perioperative antibiotics, allowing the infection to persist silently. Such microbial colonization alters the biologic environment at the fusion site, creating conditions where even highly osteoinductive graft materials may appear less effective than they truly are, thereby introducing unrecognized variability and potentially masking genuine differences in osteobiologic performance.

Importantly, advanced detection methods—including extended anaerobic cultures, multiple deep tissue samples, and sonication of retrieved hardware to disrupt biofilm—markedly improve pathogen recovery compared with standard intraoperative culture techniques. ⁵ These approaches have been increasingly adopted since 2020 and are practical to implement in revision cervical fusion procedures.

To enhance the accuracy of future osteobiologic studies, I suggest; Routine microbiologic sampling using optimized techniques during revision ACDF, Stratified reporting of outcomes based on infection status, Explicit recognition of occult infection as a potential confounder in systematic evaluations of fusion success.

Integrating infection screening into study protocols will ensure that the true performance of osteobiologic grafts is assessed in an infection-free host environment. Identifying and treating low-grade infection at the time of revision surgery may not only improve fusion rates but also provide clearer evidence regarding the comparative effectiveness of different biologic graft materials.