Maislin G, Maislin DG, Keenan BT and Alvis MR
Background: This study was performed to evaluate the preliminary clinical results for the Simplify™ Cervical Artificial Disc. Methods: We compared outcomes for the first 61 subjects to reach Month 12 follow-up in a prospective, multicenter, FDA IDE clinical trial with 61 propensity score matched historical control subjects who received conventional anterior cervical discectomy and fusion (ACDF) for single-level cervical degenerative disc disease. The outcome measures included the change from preoperative baseline to Month 12 in Neck Disability Index (NDI) and visual analog scales (VAS) for neck and arm pain with missing follow-up determined by last observation carried forward. Results: The null hypothesis that the Simplify 1-disc is inferior to ACDF (non-inferiority margin=8.4) was rejected at a 1-sided p<0.0001. The upper bound of the 1-sided 95% non-inferiority confidence interval was -7.44 which is much smaller than the non-inferiority margin of 8.4. Superiority was demonstrated with a 2-sided p=0.0004. The upper bound of the 2-sided 95% confidence interval was -6.26 which is much less than zero. Sensitivity analyses on the assumptions about missing data and the matching included completer’s analyses and analyses that were restricted to the 55 of 61 first stage matches that could be achieved without expanding of the calipers used to identify potential matches. The p-values for non-inferiority in all analyses are <0.0001. Similarly, the p-values for superiority are all ≤ 0.0030. Conclusion: Therefore, we conclude that the Simplify Disc is superior to ACDF control in terms of improvement in NDI and VAS from baseline to Month 12.
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