P61. Biomechanical Effect of Crosslinks with Long Segment Pedicle Screw Constructs

Proceedings of the NASS 22nd Annual Meeting / The Spine Journal 7 (2007) 1S–163S TDRs at 12 months. Patient satisfaction was very satisfied or satisfied in 91% of patients. Adverse events were similar between groups. CONCLUSIONS: The Kineflex TDR appears at short-term follow-up to be at least equivalent in outcome to the Charite´ TDR. At 12 months, over 80% of patients met the primary endpoint of O25% improvement in ODI and all discs displayed O3 degrees ROM. A larger sample size with longer term follow-up may reveal differences between the two devices. This prospective study also suggests that the results of the initial Charite´ US IDE study can be reproduced in a novel, post-market setting. FDA DEVICE/DRUG STATUS: Kineflex Lumbar Disc Replacement: Investigational/ Not approved; Charite´ Lumbar Disc Replacement: Approved for this indication. doi: 10.1016/j.spinee.2007.07.266

P61. Biomechanical Effect of Crosslinks with Long Segment Pedicle Screw Constructs Timothy R. Kuklo, MD, JD1, Anton E. Dmitriev, MSc2, Ronald A. Lehman, MD2, Mario J. Cardoso, MD3, Mark Erickson, MD4, Norman W. Gill, DSC5; 1Washington University in St. Louis, St Louis, MO, USA; 2DC, USA; 3Washington, DC, USA; 4Children’s Hospital, Denver, CO, USA; 5 Walter Reed Army Medical Center, Washington, DC, USA BACKGROUND CONTEXT: Crosslinks are not thought to be necessary with pedicle screw constructs, yet to date no study has reported the effect of crosslinks (CLs) after all pedicle screw long thoracic fusions. PURPOSE: The purpose of this study is to determine the biomechanical effect following the addition of CL(s) to long constructs. STUDY DESIGN/SETTING: Study of 7 human cadaver spines. OUTCOME MEASURES: Specimens were tested with a six-degrees-offreedom spine stimulator at each stage of reconstruction. METHODS: 7 human cadaveric spines were instrumented from T4-T10 with bilateral 5.5 mm multiaxial Ti pedicle screws and 5.5 mm contoured rods. Specimens were tested with a six-degree-of-freedom spine stimulator in the intact condition, after instrumentation, after 1 CL (3 different locations) and 2 CLs. Data was analyzed by loading modality (axial rotation, flexion-extension, and lateral bending) using one-way ANOVAs with an alpha of 0.05; paired t-tests were used for post-hoc analysis with correction for multiple comparisons. RESULTS: There was no difference with the addition of 1 or 2 CLs in terms of flexion-extension or lateral bending when compared to the instrumented condition (pO0.05). For axial rotation, mean ROM was 11.07  (SD 3.84) for the instrumented specimen without CLs, 8.76  (SD 2.84) with a CL at T5-6, 8.48  (SD 2.55) with a CL at T7-8, and 9.21  (SD 2.98) with a CL at T9-10. Single CLs demonstrated no significant difference from each other (pO0.05), but each significantly reduced motion better than no CL ( 20%) (p!0.05). Mean ROM for 2 CLs was 7.21  (SD 2.19) ( 35%), which was significantly less than 1 CL (p!0.05). CONCLUSIONS: Axial rotation is significantly decreased with the addition of a CL to long constructs; location is immaterial. A second CL adds further torsional stability. Flexion-extension and lateral bending are not affected. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2007.07.267

P62. Evaluating the Effect of rhBMP2 on Surgical Site Infections in a Posterolateral Lumbar Fusion Rabbit Model Andrew Simpson, BS1, Christopher Miller, BA1, Peter Whang, MD1, James Lawrence, MD1, Benjamin Erickson, BS1, Walid Waked, MD1, Jonathan Grauer, MD1; 1Yale University, New Haven, CT, USA BACKGROUND CONTEXT: Postoperative infections can have devastating implications for patients following spinal surgery. Biologic factors, such as recombinant human bone morphogenetic proteins (rhBMPs), are

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being increasingly utilized in fusion surgery. While the osteoinductive effects of rhBMPs have received great attention, their effect on local surgical site infections has not been well explored. Nonetheless, there is evidence from long bone applications to suggest that rhBMPs may help limit local infection. PURPOSE: To refine a rabbit infected posterolateral lumbar fusion model to evaluate the effect of rhBMP-2 in an infection environment, and to compare results to those seen with autograft. STUDY DESIGN/SETTING: Prospective, randomized animal study of posterolateral lumbar fusions. PATIENT SAMPLE: 28 adult female New Zealand white rabbits. OUTCOME MEASURES: Abscess grade, fusion, and callus formation. METHODS: After preparation of the L5-L6 posterolateral lumbar fusion site, rabbits were randomized to receive iliac crest autograft or rhBMP-2 with an absorbable collagen sponge (1.29 mg in 3cc/side INFUSEÒ, Medtronic, TN). After graft placement, an inoculum of Staph aureus or sterile saline was placed in the posterolateral gutters. No antibiotics were given to provide a worst case scenario. Bacterial inoculums were quantified to confirm consistency of colony forming units (CFUs) delivered. Rabbits were monitored for signs of systemic or local infection. At 5 weeks, the lumbar spines were explanted, and fusion sites evaluated for fusion, callus formation, and infection/abscess grade (Scale from 0 to 10, 0 being no infection and increasing with greater abscess size up to 10, which was assigned for death secondary to sepsis). Fusion rates were compared with chi-square analysis and infection/abscess grades were compared using a paired t-test, both considered significant at p!0.05. RESULTS: The bacterial inoculums delivered to autograft and rhBMP-2 groups, 4896133 CFUs and 4566118 CFUs respectively, were not significantly different (p50.061). In the non-inoculated control groups, fusion was observed in the autograft group in 3 of the 7 (43%) rabbits and in the rhBMP-2 group in 7 out of 7 (100%) rabbits by manual palpation (p50.018). In the inoculated groups, fusion was observed in the autograft group in 0 of 7 (0%) rabbits and in the rhBMP-2 group in 1 out of 7 (14%) rabbits by manual palpation (p50.299). The average infection/abscess grade was significantly less in the rhBMP-2 group than the autograft group, 4.961.6 and 7.461.3 respectively (p50.047). CONCLUSIONS: This study demonstrates a successful method for producing surgical site infections in a posterolateral lumbar fusion rabbit model. In the non-inoculated control groups, fusion rates were consistent with prior studies. In the setting of local bacterial inoculation without antibiotic therapy, the fusion rates of both autograft and rhBMP-2 groups were appreciably affected. While the fusion rate in the rhBMP-2 group (14%) was greater than the autograft group (0%) in the setting of infection, this was not significantly different with the current sample sizes. However, the rhBMP-2 was associated with a significantly lesser infection/abscess grade, potentially related to increased neovascularization and cellular influx response. Histologic analyses are ongoing. This study will be expanded to include more animals, in order to increase study power. FDA DEVICE/DRUG STATUS: INFUSEÒ, Medtronic, TN: Not approved for this indication. doi: 10.1016/j.spinee.2007.07.268

P63. Evaluation of ProDisc-C During Low Speed, Rear-end Impact: A Full-body Post Mortem Human Subject Study Constantine Demetropoulos, PhD1, Srinivasan Sundararajan, PhD1, Sukhinder Bilkhu, MS1, Warren Hardy, MS2, King Yang, PhD2, Jennifer Bishop, MS3, Celeste Abjornson, PhD4, Michael Bey, PhD3, Harry Herkowitz, MD5, Stephen Bartol, MD6; 1Royal Oak, MI, USA; 2 Wayne State University, Detroit, MI, USA; 3Henry Ford Hospital, Detroit, MI, USA; 4Synthes Spine, West Chester, PA, USA; 5William Beaumont Hospital, Royal Oak, MI, USA; 6Henry Ford Hospital Detroit, Detroit, MI, USA BACKGROUND CONTEXT: The potential for harm following low speed rear-end impact for cervical total disc replacement patients is yet