Finite Element Models

Univ.-Prof. biol. hum. Hendrik Schmidt

Finite element models used for the mechanical analysis of biological structures have the advantage of being bloodless and not being dependent on preparations. Their results are reproducible and parameter variations can be performed by keeping all but one parameter constant. Here different finite element models are described that were developed in our laboratory. Although the main interest is in the lumbar region, the thoracic and sacral  parts being adjacent to the lumbar one cannot be neglected when dealing with questions related to pelvis and spine altogether.

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Model of the Lumbar Spine

The current model of the lumbar spine contains five lumbar vertebrae, four lumbar intervertebral discs, and the lumbosacral disc. All ligaments and facet joints were modelled. The model was developed to simulate static body postures. All in all the model contains about 60,000 elements with about 200,000 nodal points. It is nonlinear in all three points of view due to large possible deformations, due to mostly progressive material behaviour, and due to possible contact in the facet joints.

Model of the Thoracic Spine

Although the focus of spinal research is the lumbar region, it is also necessary to consider the adjacent thoracic region that loads the lumbar one. The model of the thoracic spine consists of twelve vertebrae modelled as rigid bodies and their intervertebral discs whose material behaviour was modelled transverse isotropic to mimic the rotational stiffness with and without rib cage measured in experiments. Ribs and sternum were modelled as one dimensional beam elements. The ribcage is elastically connected to the vertebrae by the costotransverse and costovertebral ligaments. The facet joints are simulated kinematically.

Entire Model of Thoracic and Lumbar Spine with Pelvis

The complete model consists of the models of the thoracic and the lumbar spine, also incorporating sacrum and pelvis which provide insertion points of the muscular system. The modelled muscle fibres enable to load the model physiologically. The complete model allows to study multisegmental implants.

2014
Comparison of eight published static finite element models of the intact lumbar spine: Predictive power of models improves when combined together.
M Dreischarf, T Zander, A Shirazi-Adl, CM Puttlitz, CJ Adam, CS Chen, VK Goel, A Kiapour, YH Kim, KM Labus, JP Little, WM Park, YH Wang, HJ Wilke, A Rohlmann, H Schmidt
Journal of Biomechanics 2014; DOI:10.1016/j.jbiomech.2014.04.002, 2.75 Impact Factor
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2013
Considerations when loading spinal finite element models with predicted muscle forces from inverse static analyses.

Zhu R, Zander T, Dreischarf M, Duda GN, Rohlmann A, Schmidt H
Journal of Biomechanics 2013 Apr 26;46(7):1376-8, 2.75 Impact Factor
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2012
Optimised in vitro applicable loads for the simulation of lateral bending in the lumbar spine.

Dreischarf M, Rohlmann A, Bergmann G, Zander T
Medical Engineering & Physics 2012 Jul;34(6):777-80, 1.84 Impact Factor
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2011
Optimised loads for the simulation of axial rotation in the lumbar spine.

Dreischarf M, Rohlmann A, Bergmann G, Zander T
Journal of Biomechanics 2011 Aug 11;44(12):2323-7, 2.75 Impact Factor
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Spinal muscles can create compressive follower loads in the lumbar spine in a neutral standing posture.
Han KS, Rohlmann A, Yang SJ, Kim BS, Lim TH
Medical Engineering & Physics 2011 May;33(4):472-8, 1.84 Impact Factor
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2010
A non-optimized follower load path may cause considerable intervertebral rotations.

Dreischarf M, Zander T, Bergmann G, Rohlmann A
Journal of Biomechanics 2010 Sep 17;43(13):2625-8, 2.75 Impact Factor
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2009
Applying a follower load delivers realistic results for simulating standing.

Rohlmann A, Zander T, Rao M, Bergmann G
Journal of Biomechanics 2009 Jul 22;42(10):1520-6, 2.75 Impact Factor
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Realistic loading conditions for upper body bending.
Rohlmann A, Zander T, Rao M, Bergmann G
Journal of Biomechanics 2009 May 11;42(7):884-90, 2.75 Impact Factor
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2006
Determination of trunk muscle forces for flexion and extension by using a validated finite element model of the lumbar spine and measured in vivo data.

Rohlmann A, Bauer L, Zander T, Bergmann G, Wilke HJ
Journal of Biomechanics 2006;39(6):981-9, 2.75 Impact Factor
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2001
Estimation of muscle forces in the lumbar spine during upper-body inclination.

Zander T, Rohlmann A, Calisse J, Bergmann G
Clin Biomech (Bristol, Avon). 2001;16 Suppl 1:S73-80, 1.88 Impact Factor
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1999
Estimation of trunk muscle forces using the finite element method and in vivo loads measured by telemeterized internal spinal fixation devices.

Calisse J, Rohlmann A, Bergmann G
Journal of Biomechanics 1999 Jul;32(7):727-31, 2.75 Impact Factor
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