1. Biomechanical Testing of the Lumbar Intervertebral Discs Emily Brown Advisor: Dr. Gary Bledsoe BE@SLU REU, Summer 2009 Saint Louis University

2. Background Lumbar spine  Contains 5 vertebrae  Highest loads  Most prone to degenerative disc disease From: http://www.backpain-guide.com/Chapter_Fig_folders/Ch05_Anatomy_Folder/Ch5_Images/05-4_Overall_Spine.jpg

3. Intervertebral Disc Anatomy Annulus Fibrosus Nucleus Pulposus Vertebral End Plate From: http://indyspinemd.com/Images/normalAnat/IntervertebralDisc.jpg

4. Effects of Aging and Degeneration

5. Intervertebral Disc Biomechanics Compression  Failure of end plate Torsion  Most damaging to disc Degenerated Discs  Lower load to failure From: http://www.biomechanika.cz/index.php?lang=en&pg=laborato r-mechanickych-zkousek

6. Lab Goals Study biomechanical properties of orthopedics  Orthopedic devices Plate fixators Interbody spinal fusion cages  Spine Intact lumbar segment Individual intervertebral discs

7. Rationale Methodology for use on fresh lumbar spines  More accurate model for in vivo studies Finite element model Degenerative disc disease  Comparing normal tested discs to patients' discs

8. Intervertebral Disc Project Mechanical Testing  Compressional  Torsional  Compressional/Torsional Combination Analysis

9. Methods and Materials MTS  Testing  Collection of data Discs from 3 human cadavers  L1-L2 through L4-L5

10. Specific Goals Grip system for discs in testing Measure biomechanical properties  Stress v strain  Elastic modulus Determine effects of formalin fixation on disc properties

11. References Farafan HF, Cossette JW, Robertson GH, Wells RV, Kraus H: The Effects of Torsion on the Lumbar Intervertebral Joints: The Role of Torsion in the Production of Disc Degeneration. J. Bone and Joint Surg., 52: 468-497, 1970 Nixon J: Intervertebral disc mechanics: a review. Journal of the Royal Society of Medicine, v79(2): 100-104, February 1986 Panjabi M, White A: Basic Biomechanics of the Spine. J of Neurosurgery, 7(1): 76-93, 1980 Urban J, Roberts S: Degeneration of the intervertebral disc. Arthritis Research and Therapy, v5(3): 120-130, March 2003 Wilke H, Krischak S, Claes L: Formalin Fixation Strongly Influences Biomechanical Properties of the Spine

12. Questions?