Recovery Trajectories After Anterior Cervical Discectomy and Fusion

STUDY DESIGN: Retrospective analysis. OBJECTIVE: To characterize recovery trajectory after anterior cervical discectomy and fusion (ACDF) by identifying recovery phases and their inflection timepoints. SUMMARY OF BACKGROUND CONTEXT: Understanding how the number of fused levels influences recovery is essential for tailoring surgical decisions and postoperative management. MATERIALS AND METHODS: This study included patients who underwent primary ACDF for degenerative cervical disease. Outcome measures included the Neck Disability Index (NDI), and numeric rating scale (NRS) for neck and arm pain, collected longitudinally. Segmented regression modeling was employed to predict recovery trajectories by phase-specific slopes, and inflection timepoints between phases. RESULTS: A total of 290 patients were included. Segmented regression identified three improvement phases of NDI: early improvement phase (EIP), late improvement phase (LIP), and plateau phase (PP), with two inflection timepoints between phases (EIP to LIP: day 43.4±6.7; LIP to PP: day 100.7±13.1). During EIP, the 1-level group demonstrated significantly steeper improvement slopes (-0.44 points/day in NDI) compared to ≥2-level (-0.35 points/day; P=0.001). The models for NRS for neck and arm pain detected two phases: the improvement phase and PP. Neck pain improved until day 24.1±2.6, while arm pain improved until day 10.6±2.0. Level specific model showed that the breakpoint for NRS neck occurred faster in 1-level compared to ≥2-level (18.0 ± 3.0 vs. 28.2 ± 4.0 d; P = 0.042). CONCLUSION: The recovery trajectory of disability following ACDF was characterized by three phases: rapid improvement until 4-6 weeks, slower improvement until 3-4 months, followed by symptom plateau after 4 months. A greater number of fused levels slows early disability recovery and delays neck‑pain relief. These findings are informative to tailor peri‑operative expectations and rehabilitation protocols to fusion length. LEVEL OF EVIDENCE: 3.