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Updated: Jun 21, 2026

Surgical Technique for the Implantation of a Biomimetic Artificial Intervertebral Disc in a Goat Animal Model
Published on: October 10, 2025
On the stiffness matrix of the intervertebral joint: application to total disk replacement
Oliver M O'Reilly1, Melodie F Metzger, Jenni M Buckley
1Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94706-1740, USA. oreilly@berkeley.edu
Abstract:
The traditional method of establishing the stiffness matrix associated with an intervertebral joint is valid only for infinitesimal rotations, whereas the rotations featured in spinal motion are often finite. In the present paper, a new formulation of this stiffness matrix is presented, which is valid for finite rotations. This formulation uses Euler angles to parametrize the rotation, an associated basis, which is known as the dual Euler basis, to describe the moments, and it enables a characterization of the nonconservative nature of the joint caused by energy loss in the poroviscoelastic disk and ligamentous support structure. As an application of the formulation, the stiffness matrix of a motion segment is experimentally determined for the case of an intact intervertebral disk and compared with the matrices associated with the same segment after the insertion of a total disk replacement system. In this manner, the matrix is used to quantify the changes in the intervertebral kinetics associated with total disk replacements. As a result, this paper presents the first such characterization of the kinetics of a total disk replacement.
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