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Modelling creep behaviour of the human intervertebral disc
Albert J van der Veen1, Arno Bisschop, Margriet G Mullender
1Department of Physics and Medical Technology, VU University Medical Centre, The Netherlands. aj.veen@vumc.nl
Journal of Biomechanics
|June 26, 2013
Summary
Comparing creep models for intervertebral discs, this study found both Kohlrausch-Williams-Watts (KWW) and Double-Voight (DV) models fit data well. However, parameters varied with test duration, limiting extrapolation accuracy for disc mechanics.
Area of Science:
- Biomechanics
- Biomaterials Science
- Orthopedic Research
Background:
- Intervertebral disc mechanical behavior is time-dependent, with creep being a key characteristic.
- Various constitutive equations exist to model disc creep, but their predictive validity is debated.
Purpose of the Study:
- To compare the predictive accuracy of the Kohlrausch-Williams-Watts (KWW) model and the Double-Voight (DV) model for intervertebral disc creep.
- To assess the influence of test duration on the reliability of model parameters.
Main Methods:
- Human thoracic intervertebral discs underwent a specific loading protocol: 0.1 MPa preload (12h), 0.8 MPa compression (24h), and 0.1 MPa unloading (24h).
- KWW and DV models were fitted to creep data obtained over varying test durations (4-24h).
Main Results:
- Both KWW and DV models effectively described the measured creep data.
- Model parameters, particularly the time constant, showed high sensitivity to test duration, ranging from 3.6 to 17h.
- Extrapolation beyond the tested duration revealed inaccuracies: DV underestimated creep, while KWW overestimated it.
Conclusions:
- While both models capture normal disc creep behavior within the tested duration, a 24h experiment is insufficient for accurate parameter determination.
- The parameters derived are suitable for describing observed behavior but not for predicting long-term creep or extrapolating beyond the experimental timeframe.
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