629 - Comparison of Two-year Clinical Outcomes with activL Artificial Disc v...

#629 Comparison of Two-year Clinical Outcomes with activL Artificial Disc vs. Circumferential Fusion


Poster Presented by: J. Yue


J. Yue (1)
L. Miller (2)

(1) Yale University School of Medicine, Orthopaedic Surgery, New Haven, CT, United States
(2) Miller Scientific Consulting, Ashville, CT, United States


Background: Total disc replacement (TDR) is an alternative to fusion in well-selected patients with symptomatic lumbar degenerative disc disease (DDD). The activL® Artificial Disc is a novel TDR that has demonstrated distinct clinical advantages over other FDA-approved TDRs in a previous randomized controlled trial1. However, no studies have directly compared activL to fusion surgery.

Purpose: The purpose of this study was to perform a post-hoc analysis of published IDE prospective multi center randomized data to determine the comparative clinical effectiveness of activL vs. fusion in the treatment of symptomatic lumbar DDD.

Methods: Clinical outcomes with activL and lumbar fusion were determined using comparisons of the activL and ProDisc-L IDE studies1,2. While the activL IDE study included comparisons between activL (n=212) and ProDisc-L (n=64), the ProDisc-L IDE study compared ProDisc-L (n=161) to lumbar fusion (n=75). The common effectiveness outcomes reported for each group in each study included back pain severity measured on a 0-100 mm visual analogue scale (VAS), Oswestry Disability Index (ODI), and ODI success, defined as an improvement ≥ 15 points relative to baseline. All outcomes were extracted at 2 year follow-up. Comparisons of activL vs. fusion were calculated as the difference between activL and ProDisc-L plus the difference between ProDisc-L and fusion. One-sided 95% confidence intervals were calculated using pooled variances from each study. For back pain severity and ODI, a correlation r=0.5 was assumed between baseline and 2-year outcomes.

Results: Pre-operative measurements of back pain severity (VAS) and ODI were not different between groups (activL vs. ProDisc-L; ProDisc-L vs. fusion). Through 2 years, the improvement in back pain severity was 10 mm greater with activL vs. fusion (95% CI: 2 to 18 mm, p=0.02). ODI improvements were 5 points greater with activL vs. fusion (95% CI: -1 to 12, p=0.08). Both findings are comparable to ProDisc-L vs. fusion2. At 2 years, ODI success was 15% higher in the activL group (95% CI: 0% to 29%, p=0.05).

Conclusions: This post hoc analysis demonstrated that the activL Artificial Disc results in greater improvements in back pain severity and back-related disability compared to lumbar fusion. These results are consistent with previously reported ProDisc-L vs. fusion outcomes.