Association Between Preoperative HbA1c and Coded Pseudarthrosis After Anterior Cervical Discectomy and Fusion in Patients with Type 2 Diabetes: A Multi-Institutional Propensity Score-Matched Cohort Study

Background/Objectives: The association between preoperative hemoglobin A1c (HbA1c) and subsequently recorded pseudarthrosis after anterior cervical discectomy and fusion (ACDF) remains uncertain in patients with type 2 diabetes mellitus. Methods: We analyzed adults undergoing ACDF between 1 January 2016 and 31 December 2023 in the TriNetX US Collaborative Network. The most recent HbA1c recorded within 90 days before surgery was categorized as >6.5% or ≤6.5%. After independent 1:1 propensity score matching, the primary outcome was coded pseudarthrosis (ICD-10-CM M96.0, pseudarthrosis after fusion or arthrodesis) recorded on postoperative days 1–730. Kaplan–Meier/Cox, sensitivity, and exploratory HbA1c-category analyses were performed. Results: Among 6079 eligible patients, 2191 remained in each matched group. Coded pseudarthrosis was recorded in 129 (5.89%) patients with HbA1c >6.5% and 92 (4.20%) with HbA1c ≤6.5% (risk ratio 1.402, 95% confidence interval [CI] 1.080–1.820; p = 0.0128; risk difference +1.689 percentage points). The Cox hazard ratio was 1.413 (95% CI 1.082–1.847; log-rank p = 0.0108). Later-window and complete-BMI sensitivity analyses were directionally consistent. No significant differences were detected in reported secondary postoperative or subsequent cervical fusion outcomes; nonsignificance does not establish equivalence. Conclusions: Higher preoperative HbA1c was associated with more frequent coded pseudarthrosis diagnoses among matched patients, but this observational analysis does not validate nonunion at the index cervical level, establish causality, or identify a surgical eligibility threshold.