Influence of a dynamic stabilisation system on load bearing of a bridged disc: an in vitro study of intradiscal pressure

Schmoelz, Werner; Huber, J.; Nydegger, Thomas; Claes, Lutz; Wilke, Hans–Joachim

doi:10.1007/s00586-005-0032-5

Cited by 115 publications

(85 citation statements)

References 44 publications

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“…These pressure values match those obtained by Schmoelz et al [37]. In the native situation, IDP was found in the same range in all motion planes; this also applies to the effect of decompression and instrumentation with a rigid fixator and the Dynesys system on IDP.…”

Section: Discussionsupporting

confidence: 89%

The effect of design parameters of dynamic pedicle screw systems on kinematics and load bearing: an in vitro study

Schilling

Krüger²,

Grupp

et al. 2010

Eur Spine J

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As an alternative treatment for chronic back pain due to disc degeneration motion preserving techniques such as posterior dynamic stabilization (PDS) has been clinically introduced, with the intention to alter the load transfer and the kinematics at the affected level to delay degeneration. However, up to the present, it remains unclear when a PDS is clinically indicated and how the ideal PDS mechanism should be designed to achieve this goal. Therefore, the objective of this study was to compare different PDS devices against rigid fixation to investigate the biomechanical impact of PDS design on stabilization and load transfer in the treated and adjacent cranial segment. Six human lumbar spine specimens (L3-L5) were tested in a spine loading apparatus. In vitro flexibility testing was performed by applying pure bending moments of 7.5 Nm without and with additional preload of 400 N in the three principal motion planes. Four PDS devices,

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Section: Discussionsupporting

confidence: 89%

The effect of design parameters of dynamic pedicle screw systems on kinematics and load bearing: an in vitro study

Schilling

Krüger²,

Grupp

et al. 2010

Eur Spine J

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“…Schmoelz et al [9] found that the Dynesys provided stability for the unstable segment, but was more flexible than was rigid fixation system. No differences were found in motion and intradiscal pressure at the adjacent segments between the Dynesys and rigid fixation systems [9,10]. In 2007, Rohlmann et al [11] indicated that, other than after distraction, the mechanical effects of the Dynesys are similar to those of a rigid fixation system.…”

Section: Introductionmentioning

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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“…Finite element analysis and other laboratory simulations have been devised to quantify the biomechanical effect of dynamic stabilization on models of the implanted lumbar spine [14][15][16][17]. Schmoelz [18] found a reduction in the lumbar spine range of motion in flexion after the dynamic stabilization device implantation, but negligible effects on the range of motion of the segments adjacent to the implanted one.…”

Section: Introductionmentioning

confidence: 99%

Molecular MR imaging for the evaluation of the effect of dynamic stabilization on lumbar intervertebral discs

et al. 2009

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The dynamic stabilization of lumbar spine is a non-fusion stabilization system that unloads the disc without the complete loss of motion at the treated motion segment. Clinical outcomes are promising but still not definitive, and the long-term effect on instrumented and adjacent levels is still a matter of discussion. Several experiments have been devised in order to gain a better understanding of the effect of the device on the intervertebral disc. One of the hypotheses was that while instrumented levels are partially relieved from loading, adjacent levels suffer from the increased stress. But this has not been proved yet. The aim of this study was to investigate the long-term effect of dynamic stabilization in vivo, through the quantification of glycosaminoglycans (GAG) concentration within instrumented and adjacent levels by means of the delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) protocol. Ten patients with low back pain, unresponsive to conservative treatment and scheduled for Dynesys implantation at one to three lumbar spine levels, underwent the dGEMRIC protocol to quantify GAG concentration before and 6 months after surgery. Each patient was also evaluated with visual analog scale (VAS), Oswestry, Prolo, Modic and Pfirrmann scales, both at pre-surgery and at follow-up. Six months after implantation, VAS, Prolo and Oswestry scales had improved in all patients. Pfirrmann scale could not detect any change, while dGEMRIC data already showed a general improvement in the instrumented levels: GAG was increased in 61% of the instrumented levels, while 68% of the non-instrumented levels showed a decrease in GAG, mainly in the posterior disc portion. In particular, seriously GAG-depleted discs seemed to have the greatest benefit from the Dynesys implantation, whereas less degenerated discs underwent a GAG depletion. dGEMRIC was able to visualize changes in both instrumented and non-instrumented levels. Our results suggest that the dynamic stabilization of lumbar spine is able to stop and partially reverse the disc degeneration, especially in seriously degenerated discs, while incrementing the stress on the adjacent levels, where it induces a matrix suffering and an early degeneration.

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Influence of a dynamic stabilisation system on load bearing of a bridged disc: an in vitro study of intradiscal pressure

Cited by 115 publications

References 44 publications

The effect of design parameters of dynamic pedicle screw systems on kinematics and load bearing: an in vitro study

The effect of design parameters of dynamic pedicle screw systems on kinematics and load bearing: an in vitro study

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

Molecular MR imaging for the evaluation of the effect of dynamic stabilization on lumbar intervertebral discs

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