Mechanical Response of a Lumbar Motion Segment in Axial Torque Alone and Combined with Compression

Shirazi‐Adl, A.; Ahmed, A. M.; Shrivastava, S.C.

doi:10.1097/00007632-198611000-00012

Cited by 415 publications

(212 citation statements)

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“…The 8-node solid element was used to model the cortical bone, cancellous bone, endplate, posterior bony element, and annulus ground substance. For the disc, 12 double cross-linked fibre layers were embedded in the ground substance, and fibre stiffness was increased proportionally from the outermost layer to the innermost layer [16]. The 43% of the cross-sectional area in the disc was defined as the nucleus, within the range reported by Panagiotacopulos [17] (30-50%).…”

Section: Fe Model Of the Intact Lumbar Spine (Int Model)supporting

confidence: 56%

“…Under a 10-Nm moment with a 150-N preload, the current INT model showed some stiffer behaviour in flexion when compared with mean value of in vitro tests. Second, FCF in torsion of each level was compared with Chen's [19] and ShiraziAdl's [16] FE studies. A similar trend was achieved and demonstrated in our previous study.…”

Section: Convergence Test and Model Validationmentioning

confidence: 99%

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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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Section: Fe Model Of the Intact Lumbar Spine (Int Model)supporting

confidence: 56%

Section: Convergence Test and Model Validationmentioning

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

View full text Add to dashboard Cite

show abstract

“…The facet joints were assumed to be frictionless, had a gap of 0.5 mm, and could only transmit compressive force. The capsule of the facet joints and the six ligaments of the lumbar spine were (Tables 1 and 2) were taken from the literature [4,5,13]. The intact model was validated on the basis of experimental data from in vitro measurements [9,10], and a high degree of conformity was found.…”

Section: Methodsmentioning

confidence: 99%

Comparison of the biomechanical effects of posterior and anterior spine-stabilizing implants

2005

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“…The fibres and ligaments have been described in detail elsewhere [25,30]. Material properties of the different tissues were taken from the literature (Table 1) [29,[31][32][33].…”

Section: Finite Element Model Of Intact Lumbar Spinementioning

confidence: 99%

A probabilistic finite element analysis of the stresses in the augmented vertebral body after vertebroplasty

et al. 2010

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Fractured vertebral bodies are often stabilized by vertebroplasty. Several parameters, including fracture type, cement filling shape, cement volume, elastic moduli of cement, cancellous bone and fractured region, may all affect the stresses in the augmented vertebral body and in bone cement. The aim of this study was to determine numerically the effects of these input parameters on the stresses caused. In a probabilistic finite element study, an osteoligamentous model of the lumbar spine was employed. Seven input parameters were simultaneously and randomly varied within appropriate limits for [110 combinations thereof. The maximum von Mises stresses in cancellous and cortical bone of the treated vertebral body L3 and in bone cement were calculated. The loading cases standing, flexion, extension, lateral bending, axial rotation and walking were simulated. In a subsequent sensitivity analysis, the coefficients of correlation and determination of the input parameters on the von Mises stresses were calculated. The loading case has a strong influence on the maximum von Mises stress. In cancellous bone, the median value of the maximum von Mises stresses for the different input parameter combinations varied between 1.5 (standing) and 4.5 MPa (flexion). The ranges of the stresses are large for all loading cases studied. Depending on the loading case, up to 69% of the maximum stress variation could be explained by the seven input parameters. The fracture shape and the elastic modulus of the fractured region have the highest influence. In cortical bone, the median values of the maximum von Mises stresses varied between 31.1 (standing) and 61.8 MPa (flexion). The seven input parameters could explain up to 80% of the stress variation here. It is the fracture shape, which has always the highest influence on the stress variation. In bone cement, the median value of the maximum von Mises stresses varied between 3.8 (standing) and 12.7 MPa (flexion). Up to 75% of the maximum stress variation in cement could be explained by the seven input parameters. Fracture shape, and the elastic moduli of bone cement and of the fracture region are those input parameters with the highest influence on the stress variation. In the model with no fracture, the maximum von Mises stresses are generally low. The present probabilistic and sensitivity study clearly showed that in vertebroplasty the maximum stresses in the augmented vertebral body and in bone cement depend mainly on the loading case and fracture shape. Elastic moduli of cement, fracture region and cancellous bone as well as cement volume have sometimes a moderate effect while number and symmetry of cement plugs have virtually no effect on the maximum stresses.

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Mechanical Response of a Lumbar Motion Segment in Axial Torque Alone and Combined with Compression

Cited by 415 publications

References 0 publications

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

Comparison of the biomechanical effects of posterior and anterior spine-stabilizing implants

A probabilistic finite element analysis of the stresses in the augmented vertebral body after vertebroplasty

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