#535 Post-Market Surveillance Pedicle Based Dynamic Stabilization System (DSS)
Lumbar Therapies and Outcomes
Poster Presented by: M. Lorio
M.P. Lorio (1)
B.M. Lewis (1)
R.C. Hubbard (2)
(1) Neuro-Spine Solutions, P.C., Bristol, TN, USA
(2) West Virginia School of Osteopathic Medicine, Huntington, WV, USA
Purpose: On October 5, 2009, the Food and Drug Administration (FDA) ordered "dynamic stabilization system," (DSS) manufacturers to conduct post-market surveillance studies--analyzing the available clinical data to determine the efficacy of class II DSS(s) and their components for bone fusion. These studies were to address four major points: fusion rates, adverse events, subsequent surgical interventions compared to traditional (rigid) fusions, and cause of failure for any DSS. Of the many DSS(s) available on the market today, we present a retrospective case utilization review with the motion preserving implant Paradigm DSS (Paradigm Spine GmbH, Wurmlingen, Germany) and concomitant hardware failure rate of 5.0% (1/20). Paradigm DSS is a non-traditional modular system that employs either flexible rod spacers (DSS Motion) or rigid rod spacers (DSS Fusion) anchored to a segmental pedicle assembly.
Methods: Twenty Paradigm DSS cases, performed by senior author (from 2009 to 2011) were retrospectively reviewed in regards to product safety concerns expressed by the FDA. This Paradigm DSS patient cohort consisted of 12 men and 8 women with an average age of 57 years (range 29-78y). The average number of levels treated per patient was 2 (range, 1-4 levels). Specific levels treated ranged from Lumbar 1 to Sacrum, with 70% of patients receiving a "hybrid" fusion. Each case was clinically reviewed with a focus on radiographic findings. The average patient follow-up time was 18 months (range, 4-38mo). Our indications included: symptomatic debilitating lumbar degenerative disc disease (including grade 1 spondylolisthesis), stenosis, salvage, or protection of adjacent levels (topping off).
Results: Radiographic case complications were as follows:
1) symptomatic & asymptomatic halo formation 2/20 (10%),
2) anterior-column induced instability 1/20 (5%), and
3) bilateral flexible rod spacer(s) (DSS Motion) hardware symptomatic failure 1/20 (5%). All radiographic complications occurred in stabilized levels using flexible rod spacers (DSS Motion). Overall symptomatic case complication rate and concomitant revision rate were 10% respectively; both cases were revised with interbody fusion.
Case report: A 29 year-old female with failed Charite TDR at L5/S1 was initially salvaged with a "hybrid" fusion using DSS Fusion at L5/S1and DSS Motion at L4/L5. Thirty months post implantation, DSS became symptomatic following a ground-level fall (see figure). Revision was achieved by L4/L5 TLIF and exchange of DSS Fusion for DSS Motion leaving the remainder of the construct intact.
Conclusion: Ease of modular Paradigm DSS implantation is similarly accompanied with ease of modular revision as purported by Bertagnoli. Overall, our complication rate with DSS was within an acceptable range 10%. Greater than 8500 levels have been treated with DSS worldwide with only a "complaint rate of 0.25% [for] 21 issues on broken couplers.” DSS Motion overload with our patient´s fall was cited as the mode of failure. DSS Active Zone constraint on the Neutral Zone (as described by Panjabi) was our hypothesized cause for failure.
Figure: Paradigm DSS Motion Failure