P35. The Strength of the Scientific Evidence Underlying Studies Related to Food and Drug Administration-Approved Class 3 Spinal Devices: A Systematic Review Using Objective Rating Criteria

Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S and the robustness of new bone formation over allograft alone. Further studies with larger numbers are necessary. Although there are numerous studies using human demineralized bone matrix (DBM) in an athymic nude rat model, we are not aware of any previous studies utilizing homologous rat DBM in an euthymic rat model. The relatively high probability of fusion in our control group suggests that this may be a novel cost effective animal model particularly for studies evaluating conditions or substances with potentially deleterious effects on spinal fusion. FDA DEVICE/DRUG STATUS: AA861: Investigational/Not approved; Zileuton: Investigational/Not approved. doi: 10.1016/j.spinee.2009.08.292

P35. The Strength of the Scientific Evidence Underlying Studies Related to Food and Drug Administration-Approved Class 3 Spinal Devices: A Systematic Review Using Objective Rating Criteria Branko Kopjar, MD, PhD1, Zoya Bauer, MD, PhD1, Michael Fehlings, MD, PhD, FACS, FRCSC2; 1University of Washington, Seattle, WA, USA; 2 University of Toronto, Toronto, Ontario, Canada BACKGROUND CONTEXT: Attainment of marketing approval for Class III medical devices requires scientific evidence regarding safety and effectiveness. This area of clinical research represents a ‘‘shifting landscape’’ in which the need to undertake rigorous scientific research is balanced against the practicalities of introducing novel technologies to the market-place. Following publication, many of these studies have been criticized for methodological shortcomings. PURPOSE: Our team has identified potential opportunities for methodological improvements to this area of clinical research. STUDY DESIGN/SETTING: As part of this effort, we have undertaken a systematic review to assess the strength of scientific evidence from the pivotal studies used to obtain approval for Class III spinal devices in the area of degenerative disc disease (DDD). PATIENT SAMPLE: Patients with degenerative disk disease OUTCOME MEASURES: N/A METHODS: The summaries of safety and effectiveness from the publicly available Pre-market Approval (PMA) FDA applications and the corresponding main peer-reviewed journal publications for eleven FDA approved Class III devices for the treatment of DDD were scored using a modified quality checklist developed by Downs and Black (1998). The modified list had a maximum score of 26. The Levels of evidence (IdV) were assigned using a modification of Sackett’s criteria as adopted by the Journal of Bone and Joint Surgery (2008). RESULTS: The scientific support for three devices approved in the 1990s was based on case-series (level IV) evidence. The quality score for these studies ranged between 9-11. The level of evidence for the remaining eight devices approved between 1999 and 2007 studies was II and the quality score ranged between 18-22. The main methodological limitations in the most recent studies included a) a lack of blinding, b) unsatisfactory follow-up rate (!80%) and c) a small number of subjects per investigative site. Of concern, all studies were statistically underpowered to rigorously evaluate safety. The methodological quality score was higher for the FDA Summaries of the Safety and Effectiveness than in the comparative main journal publication, which may reflect the space-constraints in scientific publications. CONCLUSIONS: The level and strength of evidence supporting approval of Class III medical devices for DDD has substantially improved since the first device approval in 1996. However, significant scientific limitations remain in these studies. The key issues of concern include a lack of blinding, poor rates of follow- up, the inclusion of sites with poor patient enrolment and lack of statistical power to detect safety issues. Our team is actively examining innovative approaches to study design and oversight to further enhance the quality of efficiency of this vital area of clinical research. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2009.08.293

133S

P36. Biomechanical Comparison of Transarticular Facet and Lateral Mass Screws for Cervical Spine Fusion Claire Robertson1, Yu-Po Lee, MD2, Mark Kuper2, Andrew Mahar3, Deborah Lee4, Steven Garfin, MD2; 1Irvine, CA, USA; 2University of California, San Diego, San Diego, CA, USA; 3Children’s Hospital and Health Center - San Diego, San Diego, CA, USA; 4San Diego, CA, USA BACKGROUND CONTEXT: Percutaneous transarticular facet screws for cervical fusion may offer a miminally invasive alternative to lateral mass screw fixation for cervical fusion. It is unclear whether transarticular facet screws are as mechanically stable as lateral mass screws, especially in cases where a corpectomy has destabilized the cervical spine. PURPOSE: This study compared the biomechanical stability offered by lateral mass and transarticular facet screws with and without anterior plating in a two level corpectomy model. STUDY DESIGN/SETTING: In vitro biomechanical study PATIENT SAMPLE: Not Applicable OUTCOME MEASURES: Stiffness in three loading modes and strut graft loading METHODS: Sixteen human cadaveric cervical spines (C3-C7) were dissected and potted at the superior and inferior vertebral body. The specimens were fixed within custom fixtures in a biaxial materials test frame and tested to in flexion and extension, lateral bending and axial torsion. The specimens then underwent two level corpecomy and fixation with either lateral mass or transarticular facet screws. Testing was repeated. An anterior plate was then placed across the corpectomy site and testing repeated again. Stiffness and peak strut graft loading were calculated and compared across groups. RESULTS: Lateral mass screw constructs had significantly higher flexionextension stiffness and approached significance in lateral bending. From the post hoc tests, facet screw and anterior plate constructs were similar to lateral mass constructs without an anterior plate (p50.9 in flexion extension, p50.3 in lateral bending, p50.3 in axial torsion) In flexion and extension, the peak loading on the strut graft was 5727 and 30þ20 N for facet screws and lateral mass constructs without an anterior plate. With an anterior plate, the peak loading was 16þ11 N and 6þ6 N for facet screws and lateral mass screws respectively. Both screw type and plate had a significant effect on graft loading (p!0.01 and p!0.0001). From the post hoc test, facet screw constructs without an anterior plate had a significantly higher graft loading than any other construct (p!0.05 for all), though the other constructs were not different from each other. CONCLUSIONS: Significantly higher loading on the strut graft was observed in flexion and extension in specimens fixed with transarticular facet screws, and in axial torsion, near significant differences in stiffness were observed between screw types. FDA DEVICE/DRUG STATUS: Oasys Lateral Mass Screws: Approved for this indication; 3.5 mm Cortical Bone Screws: Not approved for this indication. doi: 10.1016/j.spinee.2009.08.294

P37. What is Degenerative Disc Disease? A Literature Review Reveals No Answer Edward Dohring, MD1, Christopher Bono, MD2, Tom Faciszewski, MD3, Belinda Duszynski4; 1Scottsdale, AZ, USA; 2Boston, MA, USA; 3 Marshfield, WI, USA; 4Burr Ridge, IL, USA BACKGROUND CONTEXT: The terms degenerative disc disease (DDD) and disc degeneration (DD) are widely used in scientific, educational, and lay literature concerning the spine. DDD and DD are frequently cited as indications for many forms of treatment (add multiple medical, PT, injection treatments, as well as lumbar fusion. Clarity regarding the precise definition of DDD and DD is critically important. Recently the terms DDD and DD, used as such without precise definition, were prominently featured in a technology assessment commissioned by the Centers for Medicare and Medicaid Services (CMS), whose purpose was to investigate the