Preoperative Magnetic Resonance Imaging Abnormalities Predict Symptomatic Adjacent Segment Degeneration After Anterior Cervical Discectomy and Fusion

Introduction Anterior cervical discectomy and fusions (ACDFs) are generally limited to the levels causing neurological symptoms, but whether adjacent asymptomatic levels should be included if they demonstrate severe radiographic degeneration is a matter of controversy. We evaluated whether asymptomatic preoperative magnetic resonance imaging (MRI) abnormalities at adjacent levels were predictive of reoperation for symptomatic adjacent-segment degeneration (ASD) after the initial ACDF. Methods We reviewed patients treated with ACDF in 2000-2010 who had MRIs preoperatively and again ≥3 years after the index surgery to evaluate new neurological symptoms. Patients were stratified by ASD severity score, calculated based on MRI features. The associations between preoperative ASD severity score and reoperation for ASD were evaluated with logistic and Cox regressions after adjusting for covariates. Results Of 1038 patients who underwent ACDF, 96 (9%) had MRI evaluation ≥3 years postoperatively (mean follow-up 78 months). Of the 195 adjacent segments evaluated, 14 (7%) were included in subsequent fusion procedures. The 10-year surgery-free survival estimate was 82.7% (73.4-93.2%). After adjusting for covariates, ASD severity scores were predictive of reoperation only for patients with the highest score (hazard ratio [HR] 4.5 [1.0-19.8]) and those with foraminal stenosis (HR 4.2 [.4-12.7]). However, the prevalence of reoperation for ASD in these groups was only 16% and 15%, respectively. Conclusion The prevalence of reoperation for ASD was low for patients who presented with new symptoms ≥3 years after the index ACDF. Our findings do not support including asymptomatic levels in an anterior fusion construct, even if severe MRI abnormalities are present preoperatively.