Role of Dynesys as Pedicle-Based Nonfusion Stabilization for Degenerative Disc Disorders

Anand, Neel; Baron, Eli M.

doi:10.1155/2012/218385

Cited by 23 publications

(21 citation statements)

References 39 publications

(50 reference statements)

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“…Dynesys is the most widely used dynamic xation method and is based on use of PSs; however, the clinical results generated by this procedure are not fully clear. 20 In our simulation, the dynamic TT provides sound biomechanical pro le, decreases disk stress at the instrumented level, and reduces stress compensation in adjacent disc and facet, similar to previous ndings. [28][29][30][31] However, no signi cant clinical bene ts of Dynesys were reported in both short term and long-term studies.…”

Section: Discussionsupporting

confidence: 86%

Traditional and Cortical Trajectory Screws of Static and Dynamic Lumbar Fixation- A Finite Element Study

Liu

Wang

et al. 2020

Preprint

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Background: Two types of screw trajectories are commonly used in lumbar surgery. Both traditional trajectory (TT) and cortical bone trajectory (CBT) were shown to provide equivalent pull-out strengths of a screw. CBT utilizing a laterally-directed trajectory engaging only cortical bone in the pedicle is widely used in minimal invasive spine posterior fusion surgery. It has been demonstrated that CBT exerts a lower likelihood of violating the facet joint, and superior pull-out strength than the TT screws, especially in osteoporotic vertebral body. No design yet to apply this trajectory to dynamic fixation. To evaluate kinetic and kinematic behavior in both static and dynamic CBT fixation a finite element study was designed. This study aimed to simulate the biomechanics of CBT-based dynamic system for an evaluation of CBT dynamization. Methods: A validated nonlinearly lumbosacral finite-element model was used to simulate four variations of screw fixation. Responses of both implant (screw stress) and tissues (disc motion, disc stress, and facet force) at the upper adjacent (L3-L4) and fixed (L4-L5) segments were used as the evaluation indices. Flexion, extension, bending, and rotation of both TT and CBT screws were simulated in this study for comparison. Results: The results showed that the TT static was the most effective stabilizer to the L4-L5 segment, followed by CBT static, TT dynamic, and the CBT dynamic, which was the least effective. Dynamization of the TT and CBT fixators decreased stability of the fixed segment and alleviate adjacent segment stress compensation. The 3.5-mm diameter CBT screw deteriorated stress distribution and rendered it vulnerable to bone-screw loosening and fatigue cracking. Conclusions: Modeling the effects of TT and CBT fixation in a full lumbosacral model suggest that dynamic TT provide slightly superior stability compared with dynamic CBT especially in bending and rotation. In dynamic CBT design, large diameter screws might avoid issues with loosening and cracking.

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Section: Discussionsupporting

confidence: 86%

Traditional and Cortical Trajectory Screws of Static and Dynamic Lumbar Fixation- A Finite Element Study

Liu

Wang

et al. 2020

Preprint

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“…In general terms, rigid metal spinal fixation devices do not change their stiffness over time, but biomechanical testing of the Dynesys demonstrated creep in the spacer, and stress relaxation in the tensioning cord, 142 and changes in stiffness with different diameter spacers. 143 Clinically, the posterior non-rigid fixation systems were designed to function as motion preservation devices, and while initial clinical outcomes were promising, 65 evidence regarding the stiffness and ROM at the instrumented level 144,145 has led to these devices being re-categorized as posterior dynamic stabilization devices. Further research is required regarding the adjacent level effects compared to traditional posterior stabilization procedures.…”

Section: Dynesys Spinal Systemmentioning

confidence: 99%

Advanced Multi-Axis Spine Testing: Clinical Relevance and Research Recommendations

et al. 2015

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Back pain and spinal degeneration affect a large proportion of the general population. The economic burden of spinal degeneration is significant, and the treatment of spinal degeneration represents a large proportion of healthcare costs. However, spinal surgery does not always provide improved clinical outcomes compared to non-surgical alternatives, and modern interventions, such as total disc replacement, may not offer clinically relevant improvements over more established procedures. Although psychological and socioeconomic factors play an important role in the development and response to back pain, the variation in clinical success is also related to the complexity of the spine, and the multi-faceted manner by which spinal degeneration often occurs.The successful surgical treatment of degenerative spinal conditions requires collaboration between surgeons, engineers, and scientists in order to provide a multi-disciplinary approach to managing the complete condition. In this review, we provide relevant background from both the clinical and the basic research perspectives, which is synthesized into several examples and recommendations for consideration in increasing translational research between communities with the goal of providing improved knowledge and care.Current clinical imaging, and multi-axis testing machines, offer great promise for future research by combining invivo kinematics and loading with in-vitro testing in six degrees of freedom to offer more accurate predictions of the performance of new spinal instrumentation. Upon synthesis of the literature, it is recommended that in-vitro tests strive to recreate as many aspects of the in-vivo environment as possible, and that a physiological preload is a critical factor in assessing spinal biomechanics in the laboratory. A greater link between surgical procedures, and the outcomes in all three anatomical planes should be considered in both the in-vivo and in-vitro settings, to provide data relevant to quality of motion, and stability.

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“…90,121 Current dynamic systems are not suitable for multilevel postural corrections. 9 An effective dynamic system should help to preserve muscle strength and bone health by allowing the dynamic motion for which the human body evolved. A dynamic fixation system suitable for postural deformities could significantly improve patient quality of life by reducing the energetic costs of fixed lordosis and reduce complications by eliminating load and deformation concentrations in the spinal levels above and below the fusion instrumentation.…”

mentioning

confidence: 99%

Etiology of lumbar lordosis and its pathophysiology: a review of the evolution of lumbar lordosis, and the mechanics and biology of lumbar degeneration

Sparrey

Bailey

Safaee

et al. 2014

FOC

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The goal of this review is to discuss the mechanisms of postural degeneration, particularly the loss of lumbar lordosis commonly observed in the elderly in the context of evolution, mechanical, and biological studies of the human spine and to synthesize recent research findings to clinical management of postural malalignment. Lumbar lordosis is unique to the human spine and is necessary to facilitate our upright posture. However, decreased lumbar lordosis and increased thoracic kyphosis are hallmarks of an aging human spinal column. The unique upright posture and lordotic lumbar curvature of the human spine suggest that an understanding of the evolution of the human spinal column, and the unique anatomical features that support lumbar lordosis may provide insight into spine health and degeneration. Considering evolution of the skeleton in isolation from other scientific studies provides a limited picture for clinicians. The evolution and development of human lumbar lordosis highlight the interdependence of pelvic structure and lumbar lordosis. Studies of fossils of human lineage demonstrate a convergence on the degree of lumbar lordosis and the number of lumbar vertebrae in modern Homo sapiens. Evolution and spine mechanics research show that lumbar lordosis is dictated by pelvic incidence, spinal musculature, vertebral wedging, and disc health. The evolution, mechanics, and biology research all point to the importance of spinal posture and flexibility in supporting optimal health. However, surgical management of postural deformity has focused on restoring posture at the expense of flexibility. It is possible that the need for complex and costly spinal fixation can be eliminated by developing tools for early identification of patients at risk for postural deformities through patient history (genetics, mechanics, and environmental exposure) and tracking postural changes over time.

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Role of Dynesys as Pedicle-Based Nonfusion Stabilization for Degenerative Disc Disorders

Cited by 23 publications

References 39 publications

Traditional and Cortical Trajectory Screws of Static and Dynamic Lumbar Fixation- A Finite Element Study

Traditional and Cortical Trajectory Screws of Static and Dynamic Lumbar Fixation- A Finite Element Study

Advanced Multi-Axis Spine Testing: Clinical Relevance and Research Recommendations

Etiology of lumbar lordosis and its pathophysiology: a review of the evolution of lumbar lordosis, and the mechanics and biology of lumbar degeneration

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