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ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

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A PARAMETERIZED FE MODEL FOR SIMULATING THE INFLUENCE OF<br />

DISC ANATOMY ON THE MECHANICAL RESPONSE OF HUMAN<br />

INTERVERTEBRAL DISCS<br />

B. Helgason 1 , P. Lindenmann 2 , H. Studer 3 , C. Reutlinger 4 and S. J. Ferguson 5<br />

1. ABSTRACT<br />

Characterizing the mechanical conditions that the intervertebral disc (IVD) must withstand<br />

across the full spectrum of population-based variation is of importance for understanding<br />

degenerative and injury processes and developing new implantable devices or treatments. The<br />

aim of the present study was twofold. Firstly, to develop a parameterized FE model of the<br />

human IVD that can be used to simulate the influence of different IVD geometries on the<br />

mechanical response of the discs. Secondly, to use this model to identify the range for<br />

mechanical properties for candidate implant or annulus repair materials. By comparing<br />

simulation results for nine different vertebra geometries, using four different load cases, we<br />

found that principal stresses in the annulus increased with increasing disc thickness but<br />

decreased with increasing vertebra size. By combining the results for all the models for all<br />

load cases we constructed a window of stress-strain responses as a suggestion for a search<br />

domain in which candidate implant or annulus repair materials could be found.<br />

2. INTRODUCTION<br />

A natural wear and tear as well as alteration of the physiology of the intervertebral discs<br />

(IVD) due to aging can lead to Degenerative Disc Disease (DDD). A degenerated disc<br />

gradually loses height and becomes stiff causing pain and other symptoms e.g. leg weakness<br />

or loss of bowel or bladder control. Treatment of late-stage DDD is traditionally<br />

accomplished through spinal arthrodesis [1], in order to achieve disc height restoration,<br />

leading to neural decompression and pain release through a rigid stabilization via bony fusion.<br />

Beside fusion and dynamic stabilization, total disc replacement (TDR) has become a popular<br />

treatment method for lumbar DDD. Future treatment options may include the focal repair of<br />

degenerated disc tissue or even the biological regeneration of the disc through a tissue<br />

engineering approach. Characterizing the mechanical conditions that the intervertebral disc<br />

must withstand across the full spectrum of population-based variation is of importance for<br />

understanding degenerative and injury processes and developing new implantable devices or<br />

treatments.<br />

1 Senior Scientist, Institute for Biomechanics, ETH-Zürich, HPP O12, Schafmattstrasse 30, 8093 Zürich,<br />

Switzerland.<br />

2 Senior Development Engineer, Spine Development Center Europe, Synthes GmbH, Eimattstrasse 3, 4436<br />

Oberdorf, Switzerland.<br />

3 Scientific consultant, Integrated Scientific Services - ISS AG, Allmendstrasse 11, 2562 Port, Switzerland.<br />

4 Post-doctoral research fellow, Institute for Surgical Technology and Biomechanics, <strong>University</strong> of Bern,<br />

Stauffacherstrasse 78, 3014 Bern, Switzerland.<br />

5 Professor, Institute for Biomechanics, ETH-Zürich, HCI E355.2, Wolfgang-Pauli Strasse 10, 8093 Zürich,<br />

Switzerland.

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