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

Background Lumbar spine  Contains 5 vertebrae  Highest loads  Most prone to degenerative disc disease From:

Intervertebral Disc Anatomy Annulus Fibrosus Nucleus Pulposus Vertebral End Plate From:

Effects of Aging and Degeneration

Intervertebral Disc Biomechanics Compression  Failure of end plate Torsion  Most damaging to disc Degenerated Discs  Lower load to failure From: r-mechanickych-zkousek

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

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

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

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

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

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: , 1970 Nixon J: Intervertebral disc mechanics: a review. Journal of the Royal Society of Medicine, v79(2): , 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): , March 2003 Wilke H, Krischak S, Claes L: Formalin Fixation Strongly Influences Biomechanical Properties of the Spine

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