Intradiscal Pressure, Shear Strain, and Fiber Strain in the Intervertebral Disc Under Combined Loading

Institute of Orthopaedic Research and Biomechanics, Universität Ulm, Ulm, Baden-Württemberg, Germany
Spine (Impact Factor: 2.3). 05/2007; 32(7):748-55. DOI: 10.1097/01.brs.0000259059.90430.c2
Source: PubMed


Finite element study.
To investigate intradiscal pressure, shear strain between anulus and adjacent endplates, and fiber strain in the anulus under pure and combined moments.
Concerning anulus failures such as fissures and disc prolapses, the mechanical response of the intervertebral disc during combined load situations is still not well understood.
A 3-dimensional, nonlinear finite element model of a lumbar spinal segment L4-L5 was used. Pure unconstraint moments of 7.5 Nm in all anatomic planes with and without an axial preload of 500 N were applied to the upper vertebral body. The load direction was incrementally changed with an angle of 15 degrees between the 3 anatomic planes to realize not only moments in the principle motion planes but also moment combinations.
Intradiscal pressure was highest in flexion and lowest in lateral bending. Load combinations did not increase the pressure. A combination of lateral bending plus flexion or lateral bending plus extension strongly increased the maximum shear strains. Lateral bending plus axial rotation yielded the highest increase in fiber strains, followed by axial rotation plus flexion or axial rotation plus extension. The highest shear and fiber strains were both located posterolaterally. An additional axial preload tended to increase the pressure, the shear, and fiber strains essentially for all load scenarios.
Combined moments seem to lead to higher stresses in the disc, especially posterolaterally. This region might be more susceptible to disc failure and prolapses. These results may help clinicians better understand the mechanical causes of disc prolapses and may also be valuable in developing preventive clinical strategies and postoperative treatments.

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Available from: Hendrik Schmidt
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    • "E-mail: (Schmidt et al., 2007), and bony components such as the pars interarticularis (Chosa, Totoribe, & Tajima, 2004), two common sites of injury in the fast bowler (Hardcastle et al., 1992 ). Bowling technique, specifically excessive trunk movements in the transverse (Burnett et al., 1996; Foster, John, Elliott, Ackland, & Fitch, 1989; Hardcastle et al., 1992) and frontal planes (Bayne et al., 2016; Ranson, Burnett, King, Patel, & O'Sullivan, 2008) also influence lumbar injury in the fast bowler. For example, excessive shoulder counter rotation (SCR) has been linked with abnormalities in the lumbar vertebra and intervertebral disk (Burnett et al., 1996; Foster et al., 1989; Hardcastle et al., 1992), with excessive lateral trunk flexion to the side contralateral to the bowling arm linked with soft tissue and bony lumbar injuries (Bayne et al., 2016; Ranson et al., 2008). "
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    ABSTRACT: Introduction: Adolescent fast bowlers are prone to sustaining lumbar injuries. Numerous components have been identified as contributing factors; however, there is limited empirical evidence outlining how the muscles of the lumbopelvic region, which play a vital role in stabilising the spine, function during the bowling action and the influence of such activation on injuries in the fast bowler. Methods: Surface electromyography was utilised to measure the function of the lumbar erector spinae, lumbar multifidus, gluteus medius and gluteus maximus muscles bilaterally during the fast bowling action in a group of 35 cricket fast bowlers aged 12-16 years. Results: Two prominent periods of activation occurred in each of the muscles examined. The period of greatest mean activation in the erector spinae and multifidus occurred near back foot contact (BFC) and within the post-ball-release (BR) phase. The period of greatest mean activation for the gluteus medius and gluteus maximus occurred during phases of ipsilateral foot contact. Discussion: The greatest periods of muscle activation in the paraspinal and gluteal muscles occurred at times where vertical forces were high such as BFC, and in the phases near BR where substantial shear forces are present. Conclusion: The posterior muscles within the lumbopelvic region appear to play a prominent role during the bowling action, specifically when compressive and shear forces are high. Further research is required to substantiate these findings and establish the role of the lumbopelvic muscles in the aetiology of lumbar injury in the cricket fast bowler.
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    • "The mesh of two intervening endplates was used to create the disc by extruding 7 circumferential layers of solid elements for the annulus fibrosus ground enclosing the nucleus mesh (Fig. 1b). These layers were reinforced by unidirectional springs distributed in concentric lamellae with crosswise pattern close to 7 35° (El-Rich et al., 2009; Schmidt et al., 2007) to represent the annular fibres (Fig. 1b). The disc volume was divided with a proportion according to the histological findings (44%_nucleus and 56%_annulus) (El-Rich et al., 2009; Schmidt et al., 2006). "
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    ABSTRACT: A harmonic synergy between the load-bearing and stabilizing components of the spine is necessary to maintain its normal function. This study aimed to investigate the load-sharing along the ligamentous lumbosacral spine under sagittal loading. A 3D nonlinear detailed Finite Element (FE) model of lumbosacral spine with realistic geometry was developed and validated using wide range of numerical and experimental (in-vivo and in-vitro) data. The model was subjected to 500N compressive Follower Load (FL) combined with 7.5Nm flexion (FLX) or extension (EXT) moments. Load-sharing was expressed as percentage of total internal force/moment developed along the spine that each spinal component carried. These internal forces and moments were determined at the discs centres and included the applied load and the resisting forces in the ligaments and facet joints. The contribution of the facet joints and ligaments in supporting bending moments produced additional forces and moments in the discs. The intervertebral discs carried up to 81% and 68% of the total internal force in case of FL combined with FLX and EXT, respectively. The ligaments withstood up to 67% and 81% of the total internal moment in cases of FL combined with EXT and FLX, respectively. Contribution of the facet joints in resisting internal force and moment was noticeable at levels L4-S1 only particularly in case of FL combined with EXT and reached up 29% and 52% of the internal moment and force, respectively. This study demonstrated that spinal load-sharing depended on applied load and varied along the spine.
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    • "à 4 [10] Facets 10 [14] à 50 [13] 0.3 à 0.4 "
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    ABSTRACT: The presented work reports the various stress and displacements observed within a total intervertebral disc of cervical level C5/C6, and this was under the action of a compressive load of 1,5kN, as well as sagittal, lateral and axial moments. We showed the importance of the nucleus pulposus, from its fundamental properties to absorb the shocks and to absorb the major part of the deformations. Through the obtained results of simulation, we can affirm that the effects of the sagittal moment are most dangerous, relatively to the axial and lateral moments. This observation is dictated by the intensity as by the nonlinear behavior increasing in a quadratic form, from a certain inclination angle which can lead to a rupture of the cervical rachis on one hand, and to a degenerative reorganisation of the disc leading thus to the cervicathrose on the other hand.
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