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Biomechanical analysis of the lumbar spine on facet joint force and intradiscal pressure--a finite element study.

Kuo CS, Hu HT, Lin RM, Huang KY, Lin PC, Zhong ZC, Hseih ML - BMC Musculoskelet Disord (2010)

Bottom Line: The results revealed that asymmetric responses of the facet joint forces exist in various postures and that such effect is amplified with larger loadings.Although the effect of the preloads on facet joint forces was not apparent, intradiscal pressure did increase with preload, and its magnitude increased more markedly in flexion than in extension and axial rotation.Compared with the applied preloads, the postures played a more important role, especially in axial rotation; the facet joint forces were increased in the contralateral facet joints as compared to the ipsilateral ones at the same level of the lumbar spine.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Civil Engineering, National Cheng Kung University, Tainan, Taiwan. kcs60417@ms17.hinet.net

ABSTRACT

Background: Finite element analysis results will show significant differences if the model used is performed under various material properties, geometries, loading modes or other conditions. This study adopted an FE model, taking into account the possible asymmetry inherently existing in the spine with respect to the sagittal plane, with a more geometrically realistic outline to analyze and compare the biomechanical behaviour of the lumbar spine with regard to the facet force and intradiscal pressure, which are associated with low back pain symptoms and other spinal disorders. Dealing carefully with the contact surfaces of the facet joints at various levels of the lumbar spine can potentially help us further ascertain physiological behaviour concerning the frictional effects of facet joints under separate loadings or the responses to the compressive loads in the discs.

Methods: A lumbar spine model was constructed from processes including smoothing the bony outline of each scan image, stacking the boundary lines into a smooth surface model, and subsequent further processing in order to conform with the purpose of effective finite element analysis performance. For simplicity, most spinal components were modelled as isotropic and linear materials with the exception of spinal ligaments (bilinear). The contact behaviour of the facet joints and changes of the intradiscal pressure with different postures were analyzed.

Results: The results revealed that asymmetric responses of the facet joint forces exist in various postures and that such effect is amplified with larger loadings. In axial rotation, the facet joint forces were relatively larger in the contralateral facet joints than in the ipsilateral ones at the same level. Although the effect of the preloads on facet joint forces was not apparent, intradiscal pressure did increase with preload, and its magnitude increased more markedly in flexion than in extension and axial rotation.

Conclusions: Disc pressures showed a significant increase with preload and changed more noticeably in flexion than in extension or in axial rotation. Compared with the applied preloads, the postures played a more important role, especially in axial rotation; the facet joint forces were increased in the contralateral facet joints as compared to the ipsilateral ones at the same level of the lumbar spine.

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Intradiscal pressures at various levels of the lumbar spine under preloads of (a) 300 N, (b) 460 N, and (c) 600 N and different loadings, including forward/backward bending moments and left/right rotation moments of 5 Nm, 10 Nm, 15 Nm, and 20 Nm.
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Figure 9: Intradiscal pressures at various levels of the lumbar spine under preloads of (a) 300 N, (b) 460 N, and (c) 600 N and different loadings, including forward/backward bending moments and left/right rotation moments of 5 Nm, 10 Nm, 15 Nm, and 20 Nm.

Mentions: Figures 9(a), (b) and 9(c) show the intradiscal pressures of the nuclei pulposi at various levels under preloads of 300 N, 460 N, and 600N and at different loadings. From these figures, the calculated data for intradiscal pressures increased with preload. In an upright standing posture, the average pressure at all levels (L1/L2 to L4/L5) was approximately 0.2 MPa under a preload of 300 N, and was 0.324 MPa and 0.42275 MPa under preloads of 460 N and 600 N, respectively. In flexion, the pressure increased noticeably compared with other postures and had a value of approximately 0.9 MPa at level L1/L2 under a forward bending (flexion) moment of 20 Nm. In the case of left and right rotations, the intradiscal pressures were relatively larger at level L1/L2 than those at other levels under the same loading and different preloads. For the left rotation, levels L1/L2 and L4/L5 had values higher than levels L2/L3 and L3/L4. Level L2/L3 did not appear to be affected by the left/right rotation postures and maintained a value of approximately 0.2 MPa when subjected to a rotation moment of less than 15 Nm. Similarly results were obtained for level L3/L4 under a rotation moment of less than 10 Nm. As in the case of extension, initially the intradiscal pressures at levels L2/L3 and L3/L4 were reduced temporarily, then after the backward bending moment exceeded 10 Nm or 15 Nm, the pressures gradually increased.


Biomechanical analysis of the lumbar spine on facet joint force and intradiscal pressure--a finite element study.

Kuo CS, Hu HT, Lin RM, Huang KY, Lin PC, Zhong ZC, Hseih ML - BMC Musculoskelet Disord (2010)

Intradiscal pressures at various levels of the lumbar spine under preloads of (a) 300 N, (b) 460 N, and (c) 600 N and different loadings, including forward/backward bending moments and left/right rotation moments of 5 Nm, 10 Nm, 15 Nm, and 20 Nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2913991&req=5

Figure 9: Intradiscal pressures at various levels of the lumbar spine under preloads of (a) 300 N, (b) 460 N, and (c) 600 N and different loadings, including forward/backward bending moments and left/right rotation moments of 5 Nm, 10 Nm, 15 Nm, and 20 Nm.
Mentions: Figures 9(a), (b) and 9(c) show the intradiscal pressures of the nuclei pulposi at various levels under preloads of 300 N, 460 N, and 600N and at different loadings. From these figures, the calculated data for intradiscal pressures increased with preload. In an upright standing posture, the average pressure at all levels (L1/L2 to L4/L5) was approximately 0.2 MPa under a preload of 300 N, and was 0.324 MPa and 0.42275 MPa under preloads of 460 N and 600 N, respectively. In flexion, the pressure increased noticeably compared with other postures and had a value of approximately 0.9 MPa at level L1/L2 under a forward bending (flexion) moment of 20 Nm. In the case of left and right rotations, the intradiscal pressures were relatively larger at level L1/L2 than those at other levels under the same loading and different preloads. For the left rotation, levels L1/L2 and L4/L5 had values higher than levels L2/L3 and L3/L4. Level L2/L3 did not appear to be affected by the left/right rotation postures and maintained a value of approximately 0.2 MPa when subjected to a rotation moment of less than 15 Nm. Similarly results were obtained for level L3/L4 under a rotation moment of less than 10 Nm. As in the case of extension, initially the intradiscal pressures at levels L2/L3 and L3/L4 were reduced temporarily, then after the backward bending moment exceeded 10 Nm or 15 Nm, the pressures gradually increased.

Bottom Line: The results revealed that asymmetric responses of the facet joint forces exist in various postures and that such effect is amplified with larger loadings.Although the effect of the preloads on facet joint forces was not apparent, intradiscal pressure did increase with preload, and its magnitude increased more markedly in flexion than in extension and axial rotation.Compared with the applied preloads, the postures played a more important role, especially in axial rotation; the facet joint forces were increased in the contralateral facet joints as compared to the ipsilateral ones at the same level of the lumbar spine.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Civil Engineering, National Cheng Kung University, Tainan, Taiwan. kcs60417@ms17.hinet.net

ABSTRACT

Background: Finite element analysis results will show significant differences if the model used is performed under various material properties, geometries, loading modes or other conditions. This study adopted an FE model, taking into account the possible asymmetry inherently existing in the spine with respect to the sagittal plane, with a more geometrically realistic outline to analyze and compare the biomechanical behaviour of the lumbar spine with regard to the facet force and intradiscal pressure, which are associated with low back pain symptoms and other spinal disorders. Dealing carefully with the contact surfaces of the facet joints at various levels of the lumbar spine can potentially help us further ascertain physiological behaviour concerning the frictional effects of facet joints under separate loadings or the responses to the compressive loads in the discs.

Methods: A lumbar spine model was constructed from processes including smoothing the bony outline of each scan image, stacking the boundary lines into a smooth surface model, and subsequent further processing in order to conform with the purpose of effective finite element analysis performance. For simplicity, most spinal components were modelled as isotropic and linear materials with the exception of spinal ligaments (bilinear). The contact behaviour of the facet joints and changes of the intradiscal pressure with different postures were analyzed.

Results: The results revealed that asymmetric responses of the facet joint forces exist in various postures and that such effect is amplified with larger loadings. In axial rotation, the facet joint forces were relatively larger in the contralateral facet joints than in the ipsilateral ones at the same level. Although the effect of the preloads on facet joint forces was not apparent, intradiscal pressure did increase with preload, and its magnitude increased more markedly in flexion than in extension and axial rotation.

Conclusions: Disc pressures showed a significant increase with preload and changed more noticeably in flexion than in extension or in axial rotation. Compared with the applied preloads, the postures played a more important role, especially in axial rotation; the facet joint forces were increased in the contralateral facet joints as compared to the ipsilateral ones at the same level of the lumbar spine.

Show MeSH
Related in: MedlinePlus