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research-article

The mechanical role of the radial fibers network within the annulus fibrosus of the lumbar intervertebral disc: a finite elements study

[+] Author and Article Information
Mirit Sharabi

School of Mechanical Engineering, The Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
miritsharabi@gmail.com

Aviad Levi-Sasson

School of Mechanical Engineering, The Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
aviadsasson@gmail.com

Roza Wolfson

School of Mechanical Engineering, The Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
rozalina7@gmail.com

Kelly R. Wade

Institute of Orthopaedic Research and Biomechanics, University of Ulm, Ulm, Germany
wadekellyr@gmail.com

Fabio Galbusera

Institute of Orthopaedic Research and Biomechanics, University of Ulm, Ulm, Germany; IRCCS Galeazzi Orthopaedic Institute, Milan, Italy
fabio.galbusera@uni-ulm.de

Dafna Benayahu

Department of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
dafnab@tauex.tau.ac.il

Hans-Joachim Wilke

Institute of Orthopaedic Research and Biomechanics, University of Ulm, Ulm, Germany
hans-joachim.wilke@uni-ulm.de

Rami Haj-Ali

School of Mechanical Engineering, The Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel; Prof. Rami Haj-Ali, School of Mechanical Engineering, The Fleischman Facultyof Engineering, Tel Aviv University, Ramat Aviv 69978, Israel. Phone: 972-3-640-8207
rami98@tau.ac.il

1Corresponding author.

ASME doi:10.1115/1.4041769 History: Received April 29, 2018; Revised October 04, 2018

Abstract

The annulus fibrosus (AF) of the intervertebral disc (IVD) consists of a set of concentric layers composed of a primary circumferential collagen fibers arranged in an alternating oblique orientation. Moreover, there exists an additional secondary set of radial translamellar collagen fibers which connects the concentric layers, creating an entangled fiber network. The aim of this study is to investigate the mechanical role of the radial fiber network. Towards that goal, a three-dimensional finite-element model of the L3-L4 spinal segment was generated, and calibrated to axial compression and pure moment loading. The AF model explicitly recognizes the two heterogeneous networks of fibers. The presence of radial fibers demonstrated a pronounced effect on the local disc responses under lateral bending, flexion and extension modes. In these modes, the radial fibers, in the disc region with axial compression stress, were in a tensile state. In addition, the circumferential fibers, on the opposite side of the IVD, were also under tension. The local stress in the matrix was decreased in up to 9% in the radial fibers presence. This implies an active fiber network acting collectively to reduce the stresses and strains in the AF lamellae. Moreover, the radial fibers reduce the sideways expansion in the matrix in 26.6% near the neutral bending axis of the disc. The proposed biomechanical model provided a new insight into the mechanical role of the radial collagen fibers in the AF structure. This model can be used in the design of future IVD substitutes.

Copyright (c) 2018 by ASME
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