Applying a follower load delivers realistic results for simulating standing

Rohlmann, A.; Zander, Thomas; Rao, Milind; Bergmann, G.

doi:10.1016/j.jbiomech.2009.03.048

Cited by 155 publications

(82 citation statements)

References 51 publications

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“…The concept of FL was effectively applied to in vitro experiments and the path of FL was known to be an important factor to avoid the induced bending by non-optimized compressive FL [29]. According to Rohlmann et al [30], applying 500 N of FL acting in the center of each vertebral body and directed to the centers of the adjacent vertebral bodies delivered the most probable ISRs among six different loading modes for simulating standing. Our model also produced similar ISRs by applying 500 N of FL only instead of a loading method used in this study, but small magnitudes of nucleus pressure were calculated especially in the lower levels (399.7, 400.5, and 452.7 MPa at the L3-L4, L4-L5, and L5-S1 level, respectively).…”

Section: Discussionmentioning

confidence: 99%

Effects of rod stiffness and fusion mass on the adjacent segments after floating mono-segmental fusion: a study using finite element analysis

Jin

Kim²,

Seo³

et al. 2012

Eur Spine J

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Purpose The aims of the present study were to compare the biomechanical effects on the adjacent segments after mono-segmental floating fusion with posterior semi-rigid or rigid stabilization, and to evaluate the effect of the amount of fusion mass on the biomechanical differences. Methods A detailed, nonlinear L1-S1 finite element model had been developed and validated. Then five models were reconstructed by different fixation techniques on the L3-L4 level: rigid fixation with an interbody spacer (Ti ? IS), rigid fixation with a large interbody spacer (Ti ? IS_all), semi-rigid fixation with an interbody spacer (PEEK ? IS), semi-rigid fixation with a large interbody spacer (PEEK ? IS_all), and semi-rigid fixation only (PEEK). Analyses were conducted for the case of erect standing position, flexion, and extension motion. Results At L1-L2 and L2-L3, PEEK ? IS demonstrated less inter-segmental rotation and nucleus pressure increments from the intact model compared with Ti ? IS. The L4-L5 and L5-S1 levels showed slightly higher values with PEEK ? IS, but these differences among the instrumented models were not significant. The motion difference based on the fusion mass at the adjacent levels was at most 3 %. All instrumentation cases generated a 55 % higher facet contact force at the lower adjacent level (L4-L5) compared to that of the intact model during 26°e xtension and the largest increment was detected at the upper adjacent level (L2-L3) in the Ti ? IS. Instrumentation with Ti ? IS markedly increased the stress in the intervertebral disk at the upper adjacent level, while the stress with PEE-K ? IS appeared largest at the lower adjacent level. Conclusions Posterior instrumentation with semi-rigid rods may lower the incidence of disk and facet degeneration in the upper adjacent segment compared to rigid rods. On the other hand, the possibility of facet degeneration will be similar for all instrumentation devices in the lower adjacent segment in the long-term. The stiffness difference between rigid and semi-rigid rods on the changes in the adjacent motion segments was more crucial than amount of fusion mass.

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Section: Discussionmentioning

confidence: 99%

Effects of rod stiffness and fusion mass on the adjacent segments after floating mono-segmental fusion: a study using finite element analysis

Jin

Kim²,

Seo³

et al. 2012

Eur Spine J

View full text Add to dashboard Cite

show abstract

“…However, the results for the adjacent levels depend on the number of vertebra included in the model. Regarding the consideration of the loading condition, a realistic load simulating the upper body [22], rather than the preload of 150 N, should be used to conduct FE analysis in the future studies. Finally, the presented FE model did not consider the nuclectomy and laminectomy surgeries.…”

Section: Discussionmentioning

confidence: 99%

Effect of the cord pretension of the Dynesys dynamic stabilisation system on the biomechanics of the lumbar spine: a finite element analysis

Liu

Zhong²,

Hsu³

et al. 2011

Eur Spine J

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The Dynesys dynamics stabilisation system was developed to maintain the mobility of motion segment of the lumbar spine in order to reduce the incidence of negative effects at the adjacent segments. However, the magnitude of cord pretension may change the stiffness of the Dynesys system and result in a diverse clinical outcome, and the effects of Dynesys cord pretension remain unclear. Displacement-controlled finite element analysis was used to evaluate the biomechanical behaviour of the lumbar spine after insertion of Dynesys with three different cord pretensions. For the implanted level, increasing the cord pretension from 100 to 300 N resulted in an increase in flexion stiffness from 19.0 to 64.5 Nm/deg, a marked increase in facet contact force (FCF) of 35% in extension and 32% in torsion, a 40% increase of the annulus stress in torsion, and an increase in the high-stress region of the pedicle screw in flexion and lateral bending. For the adjacent levels, varying the cord pretension from 100 to 300 N only had a minor influence on range of motion (ROM), FCF, and annulus stress, with changes of 6, 12, and 9%, respectively. This study found that alteration of cord pretension affects the ROM and FCF, and annulus stress within the construct but not the adjacent segment. In addition, use of a 300 N cord pretension causes a much higher stiffness at the implanted level when compared with the intact lumbar spine.

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“…The loading cases for flexion, extension, lateral bending and axial rotation were all studied ( Table 2). In order to simulate these activities, a follower load was applied in a first step, representing the compression force during standing [11]. In a second step, a moment representing the associated activity was applied and simultaneously the follower load was increased to the corresponding value as given in Table 2 [12][13][14].…”

Section: Finite Element Modelmentioning

confidence: 99%

Optimal stiffness of a pedicle-screw-based motion preservation implant for the lumbar spine

et al. 2011

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Applying a follower load delivers realistic results for simulating standing

Cited by 155 publications

References 51 publications

Effects of rod stiffness and fusion mass on the adjacent segments after floating mono-segmental fusion: a study using finite element analysis

Effects of rod stiffness and fusion mass on the adjacent segments after floating mono-segmental fusion: a study using finite element analysis

Effect of the cord pretension of the Dynesys dynamic stabilisation system on the biomechanics of the lumbar spine: a finite element analysis

Optimal stiffness of a pedicle-screw-based motion preservation implant for the lumbar spine

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