Effects of Pre-Operative HbA1c on Outcomes and the Rate of Clinical Improvement Following Anterior Cervical Discectomy and Fusion

Retrospective Cohort Study. Objectives: The objectives of this study are to (1) compare post-operative patient-reported outcome measures (PROMs) between non-diabetic (non-DM) and diabetic (DM) patients undergoing Anterior Cervical Discectomy and Fusion (ADCF), (2) characterize the clinical trajectory, and (3) compare the rate of post-operative complications. Methods: A total of 261 non-DM and 52 DM patients were included. Patient demographics, Neck Disability Index (NDI) and Patient-Recorded Outcomes Measurement Information System (PROMIS) scores were collected up to one year after operation. Maximum medical improvement (MMI) was defined as the timepoint where more than 90% of the cohort achieved a minimal clinically important difference (MCID) in survey scores. Post-operative complications were collected. Descriptive and inferential statistics were performed. Results: Non-DM patients achieve MMI significantly more quickly than DM patients (non-DM: 6 months; DM: 1 year, p < 0.010). No difference in ∆NDI (non-DM: 24.9; DM: 23.0; p = 0.824) or ∆PROMIS-Physical Function (non-DM: 7.1; DM: 9.1; p = 0.373) was found between the two cohorts. In diabetic patients undergoing single-level fusion ACDF, a pre-operative HbA1c of ≥7.3% demonstrates 100% sensitivity and 25% specificity in detecting failure to achieve 1-year PROMIS MCID (AUC = 0.833, p = 0.009). There was no association between diabetic status and post-operative complication rate. Conclusion: Diabetic patients may demonstrate a slower rate of achieving maximum medical improvement despite equal subjective and clinical outcomes. Pre-operative HbA1c ≥ 7.3% demonstrates a significant correlation with worse subjective outcomes following single-level ACDF.