Fusion Assessment, Reoperation Rates, and Imaging Modality Agreement after Four-Level Anterior Cervical Discectomy and Fusion: A Retrospective Single-Center Study.

Abstract

Study DesignRetrospective single-center cohort study.ObjectiveTo evaluate fusion and reoperation rates after four-level anterior cervical discectomy and fusion (ACDF) using a hierarchical imaging strategy, and to assess agreement between imaging modalities.MethodsPatients undergoing primary four-level ACDF with postoperative imaging for fusion assessment and ≥2-year follow-up were included. Fusion status by ≥12 months was determined using a hierarchical imaging strategy, with computed tomography (CT) prioritized, followed by dynamic flexion-extension (F-E) radiographs and plain radiographs. Early fusion (6-12 months) was analyzed separately. Reoperation within 24 months was recorded. Agreement between imaging modalities was assessed using Fleiss' kappa for tri-modality comparison and Cohen's kappa for pairwise analyses.ResultA total of 152 patients had imaging available for fusion assessment; 140 had ≥12-month follow-up. Fusion by 12 months was observed in 81.4% (114/140). Early fusion occurred in 70.1% (101/144). Nonunion most commonly involved a single level, predominantly at C6-7. Within 24 months, reoperation occurred in 7.7% of patients with nonunion and 2.6% of fused patients. In a tri-modality subset, overall agreement was high (κ=0.823), with near-perfect agreement between CT and F-E radiographs (κ=0.938).ConclusionFour-level ACDF demonstrated high fusion rates and low reoperation rates in one of the largest single-center cohorts reported to date. CT and F-E radiographs showed strong agreement, while plain radiographs tended to overestimate fusion. These findings suggest that acceptable outcomes may be achieved in appropriately selected patients and that construct length alone should not preclude consideration of an anterior-only approach.