Spine - 2026-09-10 - Journal Article
Incidence and Time Course of Adjacent Segment Disease After Anterior Cervical Fusion: A Multimodal Assessment in 400 Patients.
Matsukura Y, Sakai K, Sasaki S, Torigoe I, Tomori M, Sakaki K, Yuasa M, Morishita S, Kawabata A, Hirai T, Yoshii T, Arai Y
Topics
Key Takeaway
After anterior cervical fusion, radiographic ASD occurred in 35.2% of patients at mean 2.2 years, but MRI-confirmed compression, clinical ASD, and reoperation rates were 7.8%, 3.0%, and 2.3%, respectively, confirming a staged progression model.
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Summary
This study evaluated ASD incidence after ACF using four simultaneous endpoints—radiographic, MRI, clinical, and reoperation—in 400 patients with minimum 1-year follow-up. Kaplan-Meier analysis demonstrated annualized event rates of 11.4% (Xp-ASD), 2.5% (MRI-ASD), 0.97% (clinical ASD), and 0.74% (reoperation). Multilevel fusion (≥2 levels) increased Xp-ASD risk (HR 1.44, 95% CI 1.03–2.03) but did not significantly affect MRI, clinical, or reoperation endpoints.
Key Limitation
Mean follow-up of 3.1 years is insufficient to capture the full incidence of clinical ASD and reoperation, which develop later than radiographic changes and are likely underrepresented in this cohort.
Original Abstract
STUDY DESIGN
Retrospective cohort study.
OBJECTIVE
To evaluate the incidence and time course of adjacent segment disease (ASD) after anterior cervical fusion (ACF) using radiographic, MRI, clinical, and reoperation endpoints.
SUMMARY OF BACKGROUND DATA
ASD is a recognized concern after ACF, but reported rates vary by definition. Radiographic degeneration, MRI-confirmed neural compression, symptoms, and reoperation may represent different stages, yet these endpoints are rarely assessed together in one cohort.
METHODS
We reviewed 400 patients who underwent ACF for degenerative cervical spine disease from January 2008 to June 2015 and had ≥1 year of follow-up. ASD was assessed using four endpoints: radiographic ASD on plain radiographs (Xp-ASD), MRI-confirmed ASD (MRI-ASD), clinical ASD, and reoperation for ASD. Kaplan-Meier analyses were used to estimate ASD-free survival for each endpoint. Secondarily, Xp-ASD-free survival was compared between 1-level and ≥2-level fusion.
RESULTS
Mean age was 59.8 years, and mean follow-up was 3.1 years. Xp-ASD occurred in 141 patients (35.2%) at a mean of 2.2 years after surgery. MRI-ASD was identified in 31 patients (7.8%) at a mean of 3.3 years. Clinical ASD developed in 12 patients (3.0%), and reoperation for ASD was performed in 9 patients (2.3%). The annualized event rates were 11.4%, 2.5%, 0.97%, and 0.74%, respectively. ≥2-level fusion was associated with a higher risk of Xp-ASD than 1-level fusion (hazard ratio, 1.44; 95% confidence interval, 1.03-2.03), whereas MRI-ASD, clinical ASD, and reoperation did not differ between groups.
CONCLUSION
After ACF, Xp-ASD was common during medium-term follow-up, but MRI-confirmed compression, clinical ASD, and reoperation were infrequently observed. The results support a staged course of ASD, with a time lag between radiographic degeneration and clinically meaningful disease. Level of Evidence: 3.