European Spine Journal

, Volume 25, Issue 9, pp 2681–2690 | Cite as

Analysis of the impact of the course of hydration on the mechanical properties of the annulus fibrosus of the intervertebral disc

  • Małgorzata ŻakEmail author
  • Celina Pezowicz
Original Article



The aim of this study was to determine the impact of free hydration on the mechanical parameters of the annulus fibrosus (AF) of the intervertebral disc (IVD), determined in a standard manner. Attention was also given to the hydration occurring in real time and geometric changes resulting from swelling of the AF.


Uniaxial tensile tests of multilayer samples of the AF with bone attachment were performed for two groups: samples subjected to 30 min of hydration prior to the mechanical test, and control samples, which were not subjected to additional hydration.


As a result of hydration, the values of both the failure stress (σ UTS) and the tensile modulus (E) were lower than in the control group. A decrease in these values was observed for the AF from both the anterior and posterior parts of the IVD.


The tests showed a significant dependence of the determined mechanical parameters on the cross-sectional area. The larger the cross-sectional area, the lower the obtained value of stress. By contrast, the value of the stiffness coefficient is independent of the cross-sectional area. The differences in mechanical parameters are related mainly to water absorption into structures of the AF during hydration. This is confirmed by microscopic analysis of geometric dimensions of the AF during hydration conducted in real time. The greatest changes occurred in the radial direction, where the thickness increased by 2.05 mm, while in the axial direction the main change concerned an increase in height by 0.69 mm. There were negligible changes in the circumferential direction.


Swelling Hydration Intervertebral disc Annulus fibrosus Tensile properties 


Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Department of Biomedical Engineering, Mechatronics and Theory of MechanismsWroclaw University of TechnologyWrocławPoland

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