Comment on: Does Aspirin Use Influence Rates of Pseudoarthrosis After Anterior Cervical Discectomy and Fusion?

To the Editor,

We read with great interest the study by Kim et al., “Does Aspirin Use Influence Rates of Pseudoarthrosis After Anterior Cervical Discectomy and Fusion?” ¹ The authors should be commended for addressing a clinically relevant and frequently encountered question in cervical spine surgery. Their propensity score–matched analysis reported that 81 mg aspirin use was associated with lower pseudoarthrosis rates at 6 months, 1 year, and 2 years after single-level anterior cervical discectomy and fusion (ACDF), as well as a lower 2-year rate of reoperation with additional spinal fusion. Notably, this association was not observed with 325 mg aspirin after single-level ACDF or with either aspirin dose after multi-level ACDF. These findings are reassuring in suggesting that aspirin use does not appear to increase pseudoarthrosis risk after ACDF; however, the apparent protective association of low-dose aspirin should be interpreted cautiously.

A key issue is the exposure definition. Aspirin use was defined by documentation within both the 3-month preoperative and 3-month postoperative windows. ¹ This approach may preferentially classify patients as aspirin users if they were stable enough to resume aspirin, had consistent medication documentation, or maintained closer contact with the healthcare system after surgery. Such factors may be associated with medication adherence, cardiovascular care, postoperative follow-up, and overall health status, and may not be fully captured by propensity matching. Therefore, the lower pseudoarthrosis rate observed in the 81 mg aspirin cohort may partly reflect exposure-definition bias or healthcare-contact differences rather than a true dose-specific protective effect on arthrodesis. The lack of a consistent dose-response pattern and the absence of a similar association in multi-level ACDF further support a cautious interpretation. In this context, the results may be more appropriately framed as evidence against a harmful association between aspirin and pseudoarthrosis, rather than evidence that low-dose aspirin improves fusion.

The outcome definition also deserves consideration. Pseudoarthrosis after ACDF remains heterogeneous in clinical practice and depends on imaging modality, radiographic criteria, symptoms, follow-up intensity, and surgeon interpretation. ² Administrative coding may not reliably distinguish radiographic nonunion from clinically meaningful pseudoarthrosis, and reoperation with additional fusion may reflect adjacent segment disease rather than index-level nonunion when level-specific information is unavailable. Future analyses defining aspirin exposure using preoperative status alone, modeling postoperative aspirin resumption separately, or comparing aspirin continuers with discontinuers could help clarify whether the observed association is medication-related. An active-comparator new-user framework may also reduce treatment-selection and healthcare-contact bias. ³ Kim et al. provide important early evidence that aspirin use may not increase pseudoarthrosis risk after ACDF, but prospective studies with standardized exposure timing and radiographic fusion assessment are needed before low-dose aspirin can be considered protective for cervical arthrodesis.