Influence of Modic changes on short-term clinical and patient-reported outcomes after anterior cervical discectomy and fusion: a retrospective cohort study.

BACKGROUND: Modic changes are MR signal changes in the vertebral endplate and adjacent subchondral bone marrow that reflect degenerative and inflammatory processes. Their prognostic significance after anterior discectomy and fusion (ACDF) remains incompletely defined. OBJECTIVE: To determine whether Modic changes are associated with baseline disease severity and short-term clinical and patient-reported outcomes after ACDF. METHODS: We retrospectively analyzed 130 patients with classifiable Modic status who underwent ACDF and completed 6-month follow-up. The primary outcome measure was the 6-month change in the Neck Disability Index (NDI). Secondary outcomes included neck and arm Visual Analog Scale (VAS) scores, motor grade, and clinically important responder rates. Comparisons were made using appropriate parametric or non-parametric tests. Multivariable, propensity-score-adjusted, and inverse-probability-of-treatment-weighted analysis were used to evaluate the independent association between Modic status and NDI improvement. RESULTS: Thirty-six patients were Modic-positive, and 94 were Modic-negative. Modic-positive patients were older (52.3 vs. 45.9 years; p = 0.011). Additionally, these patients exhibited a higher surgical level Pfirrmann grade (4.39 vs. 4.02; p < 0.001), greater spinal cord compression (p = 0.001), and a higher prevalence of myelomalacia (44.4% vs. 21.3%; p = 0.015). Significant improvements in neck VAS, arm VAS, NDI, and motor grade scores were observed in both groups at the 6-month mark (all within-group p < 0.001). Although post-procedure residual neck VAS and NDI scores were higher in Modic-positive patients, the change scores did not differ significantly between the groups. Modic status was not found to be independently associated with NDI improvement in the expanded multivariable model (β = 0.90; 95% CI, -0.44 to 2.24; p = 0.185), the propensity-score-adjusted model (β = 0.98; 95% CI, -2.15 to 4.11; p = 0.537), or the weighted analysis (β = 0.25; 95% CI, -2.65 to 3.15; p = 0.865). NDI responder rates were 91.7 and 83.0%, respectively (p = 0.328). CONCLUSION: Cervical Modic changes were associated with more advanced structural degeneration, spinal cord compression, and myelomalacia, but they did not show an independent association with the level of short-term improvement following ACDF. Modic status alone should not be considered an adverse short-term prognostic factor in appropriately selected patients.