Comparison of 1-Level Versus 2-Level Anterior Cervical Discectomy and Fusion

STUDY DESIGN: This study represents a posthoc analysis of data collected from 2 control arms of a prospective, randomized study. OBJECTIVE: The purpose of this study was to compare results of patients undergoing 1- versus 2-level anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: For single-level ACDF, reported outcomes have generally been good; however, results for 2 levels have been less consistent. METHODS: This 60-month follow-up study was based on data from the prospective Food and Drug Administration regulated Mobi-C artificial disc trial. Serving as the control, ACDF was performed at 1 level in 81 patients and 2 levels in 105 patients. Study selection criteria, fusion technique, and outcome measures were identical, with the only exception being the number of levels that were pathological and operated. RESULTS: Neck Disability Index (NDI) scores, visual analog scales assessing neck and arm pain, and SF-12 scores improved significantly in both groups. Significant differences were observed between groups on NDI and SF-12 PCS scores through 60 months. Fusion rates were 93.3% in the 1-level group and 86.1% in the 2-level (60 months, not significantly different). Adjacent segment degeneration occurred in 54.7% of patients at the superior level and 44.7% at the inferior segment in the 1-level group and 70.8%, and 55.0% respectively in 2-level patients (trend at superior level; 0.05 < P < 0.10). Subsequent index level surgery was performed in 11.1% of single-level patients versus 16.2% of the 2-level group (not significantly different). CONCLUSION: One- and 2-level ACDF groups improved significantly and maintained improvement throughout 60 month follow-up. When comparing groups, outcomes were often similar, though the 1-level group demonstrated higher fusion rates at 6 and 12 months, greater improvement in NDI scores from 18 to 60-month follow-up, and greater improvement in SF-12 PCS from 12 to 60 months.