Comparison of One-Level versus Two-Level Anterior Cervical Discectomy and Fusion: Clinical and Radiograph Follow-Up at 60 Months in Patients Serving as Control Groups in Randomized Trials
Authors: Zigler Jack , Rogers Roger Warren , Ohnmeiss Donna , Guyer Richard 
Published: May 2015

Introduction Anterior cervical discectomy and fusion (ACDF) has become a standard surgical option for patients with neck pain or radicular symptoms who failed nonoperative care. Although outcomes are generally good in patients undergoing single-level procedures, results for two-level cases have been less consistent. The purpose of this study was to compare results of single level. ACDF with those of two-level ACDF in patients serving as control groups in a total disc replacement trial. Materials and Methods This was a post hoc analysis of data from two control arms of the Food and Drug Administration regulated trial for the Mobi-C artificial disc. As the control treatment, ACDF with allograft and anterior plate was performed at one level in 81 patients and at two levels in 105 patients for the treatment of symptomatic disc degeneration. The study selection criteria, surgical technique, and outcome measures were identical with the only exception being pathology and surgery at one or two levels. Radiographic assessments were performed by an independent laboratory. In the two-level group, both the levels had to be radiographically fused for the patient to be considered fused. Results Gender, age, body mass index, and 5-year follow-up rates (∼ 75%) were similar in the two groups. Operative time and blood loss were significantly less in the single-level cases ( p < 0.05). Preoperative Neck Disability Index (NDI) scores were similar in the two groups and both improved significantly by 6 weeks and remained significantly improved through follow-up ( p < 0.05). The scores improved by approximately 50% in both the groups. Scores in the single-level group were significantly less at several time points. Visual analog scale scores assessing neck and arm pain followed a pattern similar to NDI, with significant improvement in both groups at 6 weeks' postoperative being maintained through 5 years, with few significant differences between groups. Both groups had significant improvements in SF-12 PCS and MCS scores by 6 months which were maintained throughout follow-up. The single-level group had significantly greater PCS scores at 12-month follow-up and thereafter ( p < 0.05). There were no significant differences in MCS scores between the groups. At 5 years, there was no significant difference in index level secondary surgery rates (11.1 vs. 16.2%). At 60 months, the one-level group fusion rate was 93.3versus 86.1% in the two-level group (not statistically significant). Fusion rates were significantly greater in the one-level group at 6 and 12 months. There was a trend (not statistically significant) for greater adjacent segment degeneration at the inferior segment in the two-level group. Conclusion The design of the disc replacement study created a unique opportunity to compare one- versus two-level ACDF control groups, which used the same inclusion/exclusion criteria and evaluations. Single-level ACDF outcomes were better on a few measures. However, patients in both groups had significantly improved scores on various outcome measures early after surgery and these improvements were maintained throughout 5-year follow-up.