Multi- versus single-level anterior cervical discectomy and fusion: comparing sagittal alignment, early adjacent segment degeneration, and clinical outcomes

Purpose The purpose of this study was to compare the rates of adjacent segment degeneration (ASD), sagittal alignment parameters, and patient-reported outcomes in patients who underwent multi-level versus single-level anterior cervical discectomy and fusion (ACDF). Methods A retrospective cohort analysis was performed on consecutive patients who underwent an ACDF. Pre- and post-operative radiographic assessment included ASD, change in C2-C7 lordosis, T1 angle, levels fused, sagittal vertical axis (SVA), fusion mass lordosis, proximal and distal adjacent segment lordosis. Patient-reported outcomes were obtained. Results Of the 404 that underwent an ACDF with a minimum of 6 months of follow-up (average 28 months), there was no significant difference in the rate of radiographic ASD overall (p = 0.479) or in the proximal or distal adjacent segments on multivariate analysis. Secondarily, the multi-level fusions appear to restore significantly greater amounts of lordosis compared to single-level procedures (p < 0.001) and are able to maintain the corrected cervical lordosis and fusion segment lordosis over time. From the immediate post-operative period to final follow-up, the single-level ACDFs show continuing lordosis improvement (p = 0.005) that is significantly greater than that of the multi-level constructs. There were no significant differences between pre-operative, post-operative, or change in patient-reported outcomes. Conclusions Two years following an ACDF, patients who underwent multi-level fusions appear to restore significantly greater amounts of lordosis compared to single-level procedures, while single-level ACDFs show significantly greater amounts of lordosis improvement over time. Multi-level procedures may not be at a significantly greater risk of developing early radiographic evidence of ASD compared to single-level procedure.