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Effect of Degeneration on Fluid-Solid Interaction within Intervertebral Disk Under Cyclic Loading - A Meta-Model Analysis of Finite Element Simulations.

Nikkhoo M, Khalaf K, Kuo YW, Hsu YC, Haghpanahi M, Parnianpour M, Wang JL - Front Bioeng Biotechnol (2015)

Bottom Line: The results showed that the averaged peak-to-peak disk deformations during the in vitro cyclic tests were well fitted with limited FE simulations and a quadratic response surface regression for both disk groups.The results showed that higher loading frequency increased the intradiscal pressure, decreased the total fluid loss, and slightly increased the maximum axial stress within solid matrix.Based on this study, it is found that enzyme-induced degeneration decreases energy attenuation capability of disk, but less change the strength of disk.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University , Tehran , Iran ; Institute of Biomedical Engineering, College of Medicine and Engineering, National Taiwan University , Taipei , Taiwan.

ABSTRACT
The risk of low back pain resulted from cyclic loadings is greater than that resulted from prolonged static postures. Disk degeneration results in degradation of disk solid structures and decrease of water contents, which is caused by activation of matrix digestive enzymes. The mechanical responses resulted from internal solid-fluid interactions of degenerative disks to cyclic loadings are not well studied yet. The fluid-solid interactions in disks can be evaluated by mathematical models, especially the poroelastic finite element (FE) models. We developed a robust disk poroelastic FE model to analyze the effect of degeneration on solid-fluid interactions within disk subjected to cyclic loadings at different loading frequencies. A backward analysis combined with in vitro experiments was used to find the elastic modulus and hydraulic permeability of intact and enzyme-induced degenerated porcine disks. The results showed that the averaged peak-to-peak disk deformations during the in vitro cyclic tests were well fitted with limited FE simulations and a quadratic response surface regression for both disk groups. The results showed that higher loading frequency increased the intradiscal pressure, decreased the total fluid loss, and slightly increased the maximum axial stress within solid matrix. Enzyme-induced degeneration decreased the intradiscal pressure and total fluid loss, and barely changed the maximum axial stress within solid matrix. The increase of intradiscal pressure and total fluid loss with loading frequency was less sensitive after the frequency elevated to 0.1 Hz for the enzyme-induced degenerated disk. Based on this study, it is found that enzyme-induced degeneration decreases energy attenuation capability of disk, but less change the strength of disk.

No MeSH data available.


Related in: MedlinePlus

Comparison of disk deformation obtained from in vitro cyclic loading experiments and the ones predicted by poroelastic FE model for (A) intact and (B) enzyme-induced degenerative intervertebral disks.
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Figure 2: Comparison of disk deformation obtained from in vitro cyclic loading experiments and the ones predicted by poroelastic FE model for (A) intact and (B) enzyme-induced degenerative intervertebral disks.

Mentions: The averaged peak-to-peak disk deformations during cyclic loading experiments were well fitted by FE model predictions for both intact (Figure 2A) and enzyme-induced degenerated disks (Figure 2B). The average normalized percentages of RMS error were 3.84 (0.96) and 3.42 (0.79)% for the intact and enzyme-induced degenerated disks, respectively. For the intact disks, the average elastic modulus of anulus fibrosus and nucleus pulposus were 2.35 and 1.41 MPa, and the average hydraulic permeability was 2.17 × 10−16 m4/Ns (Table 2). For the enzyme-induced degenerated disk, the average elastic modulus of anulus fibrosus and nucleus pulposus decreased to 2.16 and 1.30 MPa, and the average hydraulic permeability decreased to 1.39 × 10−16 m4/Ns (Table 2). The results of discriminate analysis showed that 88.9% of intact disks (8 of 9 intact disks) correctly classified as intact group using the current backward material property identification algorithm. This criterion was 77.8% (7 of 9 enzyme-induced degenerated disks) for enzyme-induced degenerated disks group.


Effect of Degeneration on Fluid-Solid Interaction within Intervertebral Disk Under Cyclic Loading - A Meta-Model Analysis of Finite Element Simulations.

Nikkhoo M, Khalaf K, Kuo YW, Hsu YC, Haghpanahi M, Parnianpour M, Wang JL - Front Bioeng Biotechnol (2015)

Comparison of disk deformation obtained from in vitro cyclic loading experiments and the ones predicted by poroelastic FE model for (A) intact and (B) enzyme-induced degenerative intervertebral disks.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4309208&req=5

Figure 2: Comparison of disk deformation obtained from in vitro cyclic loading experiments and the ones predicted by poroelastic FE model for (A) intact and (B) enzyme-induced degenerative intervertebral disks.
Mentions: The averaged peak-to-peak disk deformations during cyclic loading experiments were well fitted by FE model predictions for both intact (Figure 2A) and enzyme-induced degenerated disks (Figure 2B). The average normalized percentages of RMS error were 3.84 (0.96) and 3.42 (0.79)% for the intact and enzyme-induced degenerated disks, respectively. For the intact disks, the average elastic modulus of anulus fibrosus and nucleus pulposus were 2.35 and 1.41 MPa, and the average hydraulic permeability was 2.17 × 10−16 m4/Ns (Table 2). For the enzyme-induced degenerated disk, the average elastic modulus of anulus fibrosus and nucleus pulposus decreased to 2.16 and 1.30 MPa, and the average hydraulic permeability decreased to 1.39 × 10−16 m4/Ns (Table 2). The results of discriminate analysis showed that 88.9% of intact disks (8 of 9 intact disks) correctly classified as intact group using the current backward material property identification algorithm. This criterion was 77.8% (7 of 9 enzyme-induced degenerated disks) for enzyme-induced degenerated disks group.

Bottom Line: The results showed that the averaged peak-to-peak disk deformations during the in vitro cyclic tests were well fitted with limited FE simulations and a quadratic response surface regression for both disk groups.The results showed that higher loading frequency increased the intradiscal pressure, decreased the total fluid loss, and slightly increased the maximum axial stress within solid matrix.Based on this study, it is found that enzyme-induced degeneration decreases energy attenuation capability of disk, but less change the strength of disk.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University , Tehran , Iran ; Institute of Biomedical Engineering, College of Medicine and Engineering, National Taiwan University , Taipei , Taiwan.

ABSTRACT
The risk of low back pain resulted from cyclic loadings is greater than that resulted from prolonged static postures. Disk degeneration results in degradation of disk solid structures and decrease of water contents, which is caused by activation of matrix digestive enzymes. The mechanical responses resulted from internal solid-fluid interactions of degenerative disks to cyclic loadings are not well studied yet. The fluid-solid interactions in disks can be evaluated by mathematical models, especially the poroelastic finite element (FE) models. We developed a robust disk poroelastic FE model to analyze the effect of degeneration on solid-fluid interactions within disk subjected to cyclic loadings at different loading frequencies. A backward analysis combined with in vitro experiments was used to find the elastic modulus and hydraulic permeability of intact and enzyme-induced degenerated porcine disks. The results showed that the averaged peak-to-peak disk deformations during the in vitro cyclic tests were well fitted with limited FE simulations and a quadratic response surface regression for both disk groups. The results showed that higher loading frequency increased the intradiscal pressure, decreased the total fluid loss, and slightly increased the maximum axial stress within solid matrix. Enzyme-induced degeneration decreased the intradiscal pressure and total fluid loss, and barely changed the maximum axial stress within solid matrix. The increase of intradiscal pressure and total fluid loss with loading frequency was less sensitive after the frequency elevated to 0.1 Hz for the enzyme-induced degenerated disk. Based on this study, it is found that enzyme-induced degeneration decreases energy attenuation capability of disk, but less change the strength of disk.

No MeSH data available.


Related in: MedlinePlus