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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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Comparison of the calculated results with previous studies.
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Figure 2: Comparison of the calculated results with previous studies.

Mentions: To validate the constructed model, we compared the calculated intradiscal pressures of the L2/L3 disc, under the preload of 300N, 460 N and 600N respectively over the superior surface of the L1 vertebral body in a standing posture, with those reported in the literature [1,23-26] (Figure 2), and found that the linearity with compressive load is in agreement with their studies. Although the calculated data in this study appears to be relative lower than most of the previous results, it could be interpreted reasonably from the fact that the stronger homogeneous annulus fiber elements were used in this study, and the sensitivity analysis for the intradiscal pressure versus the inner fiber strength at the level L2/L3, under preload 460N, is shown in Figure 3. The changes in intradiscal pressures at various levels in different postures also exhibit the similarity when compared to the research by Rohlmann et al. [9] as shown in Figure 4.


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)

Comparison of the calculated results with previous studies.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Comparison of the calculated results with previous studies.
Mentions: To validate the constructed model, we compared the calculated intradiscal pressures of the L2/L3 disc, under the preload of 300N, 460 N and 600N respectively over the superior surface of the L1 vertebral body in a standing posture, with those reported in the literature [1,23-26] (Figure 2), and found that the linearity with compressive load is in agreement with their studies. Although the calculated data in this study appears to be relative lower than most of the previous results, it could be interpreted reasonably from the fact that the stronger homogeneous annulus fiber elements were used in this study, and the sensitivity analysis for the intradiscal pressure versus the inner fiber strength at the level L2/L3, under preload 460N, is shown in Figure 3. The changes in intradiscal pressures at various levels in different postures also exhibit the similarity when compared to the research by Rohlmann et al. [9] as shown in Figure 4.

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