Remedy for fictive negative pressures in biphasic finite element models of the intervertebral disc during unloading

Hendrik Schmidt, Fabio Galbusera, Hans Joachim Wilke, Aboulfazl Shirazi-Adl

Research output: Contribution to journalArticlepeer-review

Abstract

Previous biphasic finite element studies investigated the temporal response of a spinal segment under rather simplified loading conditions with no attention to unloading and recovery phases. Employment of existing constitutive relations in porous media yields rather large suction-type pore pressures in the disc as the load suddenly disappears. Such negative pressures are absent in vivo and are hence fictive. The aim of this study was to search for remedies to avoid the computation of negative pressures upon unloading. Partial saturation for the disc or a rest load (RL) higher than 400N totally eliminated the negative pressures. Decreasing the voids ratio (VR) also led to a reduced negative pressure. When defining a partial saturated disc or using a lower VR in combination with a boundary pressure of 0.25 MPa and a RL of 350 N, no negative pressure was calculated. It appears that the constraint of full saturation and a high mobile fluid fraction of the disc tissues along with inadequate tissue properties are the likely causes of negative pressures during unloading.

Original languageEnglish
Pages (from-to)293-303
Number of pages11
JournalComputer Methods in Biomechanics and Biomedical Engineering
Volume14
Issue number3
DOIs
Publication statusPublished - 2011

Keywords

  • Finite element analysis
  • Intervertebral disc
  • Negative pore pressure
  • Poroelastic
  • Recovery
  • Suction

ASJC Scopus subject areas

  • Bioengineering
  • Biomedical Engineering
  • Computer Science Applications
  • Human-Computer Interaction

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