Biomechanical Effects of Disc Degeneration and Hybrid Fixation on the Transition and Adjacent Lumbar Segments

Lin, Shu; Wang, Chih Wei; Tsai, Wen Chi; Chen, Yeung Jen; Hwang, Jiun Ren

doi:10.1097/brs.0b013e31826cdd93

Cited by 43 publications

(66 citation statements)

References 26 publications

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“…Some, such as the morphology and material property of the tissues have been previously discussed. 22 However, the pedicle size substantially affects the diameter of the inserted screw and is not extensively investigated in this study. Only 3.5 mm diameter CBT screws were considered to show the effect of the slimmest diameter screws that may be used in clinical use.…”

Section: Discussionmentioning

confidence: 99%

“…The material properties of all implants and lumbosacral tissues were adapted from a previous model of the current authors that has been validated from cadaveric and numerical data. 22…”

Section: Methodsmentioning

confidence: 99%

“…The simulative mechanism of the TT and CBT dynamic fixator were previously described as space and cord Dynesys like construct. 22 Between static and dynamic fixations, the insertion site orientations of the pedicle screws and the rod curvature were modeled under the guidance of an orthopedic surgeon. The top-and side-view trajectories of the TT and CBT screws are shown in Figure 2.…”

Section: Static and Dynamic Traditional And Cortical Constructsmentioning

confidence: 99%

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Biomechanical Investigation about Traditional and Cortical Trajectory Screws of Static and Dynamic Lumbar Fixation

Liu

Wang

et al. 2019

Preprint

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Background To evaluate kinetic and kinematic behavior in both static and dynamic CBT fixation a finite element study was designed. Two types of screw trajectories are commonly used in lumbar surgery. Both traditional trajectory (TT) and cortical bone trajectory (CBT) provide equivalent pull-out strengths of a screw. Dynesys fixation of TT screws, but not dynamization of CBT screws, has been used extensively in lumbar surgery. 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 A systematic analysis of the effects of TT and CBT fixation constructs on kinematic and kinetic responses in a full lumbosacral model is currently lacking. This study examined both the static fixation effect and its dynamic counterpart and identified that dynamization of CBT have slightly inferior structural stiffness than dynamic TT and cautious preoperative evaluation is essential if 3.5-mm diameter CBT screws are used. Therefore, 4.5-mm or 5.5-mm diameter CBT screws, or as big as tolerated, are recommended to avoid loosening and cracking.

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Section: Discussionmentioning

confidence: 99%

“…The material properties of all implants and lumbosacral tissues were adapted from a previous model of the current authors that has been validated from cadaveric and numerical data. 22…”

Section: Methodsmentioning

confidence: 99%

Section: Static and Dynamic Traditional And Cortical Constructsmentioning

confidence: 99%

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Biomechanical Investigation about Traditional and Cortical Trajectory Screws of Static and Dynamic Lumbar Fixation

Liu

Wang

et al. 2019

Preprint

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“…The lumbosacral model from L1 to S1 segments has been developed and validated in the previous studies of the current authors (Chien et al, 2014;Chuang et al, 2012;Chuang et al, 2013). For a paired facet joint, the orientation and separation of the articulating surfaces were cautiously established to ensure a consistent unloaded neutral position within a range of around 0.5 mm.…”

Section: Lumbosacral Modelsmentioning

confidence: 99%

Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion: A finite element analysis

Hsieh

Chen

et al. 2017

Clinical Biomechanics

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“…Its purpose is to relieve clinical symptoms, and preserving lumbar motion is seldom considered. Recent biomechanical and clinical data show that range of motion (ROM) decreases at the fusion level, leading to ROM at the non-surgical level increase to compensate for the lost ROM, resulting in aggravation at the non-surgical level [2–7]. These conditions, in turn, can accelerate the degenerative process and may cause adjacent segment degeneration (ASD) and new symptoms [2–7].…”

Section: Introductionmentioning

confidence: 99%

The influence of L4–S1 Dynesys® dynamic stabilization versus fusion on lumbar motion and its relationship with lumbar degeneration: a retrospective study

et al. 2017

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BackgroundThe aim of this study is to evaluate the efficacy of Dynesys® posterior dynamic stabilization (PDS) in the treatment of L4–S1 degenerative diseases and to assess the influence of postoperative motion on lumbar degeneration.MethodsIncluded in this retrospective study were patients with L4–S1 degenerative disease who underwent fusion or PDS from September 2010 to September 2014. Clinical outcomes were assessed by preoperative and postoperative visual analog scale (VAS) and Oswestry Disability Index (ODI). Preoperative and postoperative X-rays assessed range of motion (ROM) of the non-surgical and surgical levels and whole lumbar. MRI assessed degeneration of non-surgical levels.ResultsA total of 56 consecutive patients were divided into two groups: group A, PDS, and group B, fusion. Patient demographics and baseline characteristics were similar in the two groups. In both groups, there was a significant difference between preoperative and postoperative VAS and ODI scores (P < 0.05). However, there was a significant difference in a 6-month follow-up ODI between the two groups (P < 0.05). X-rays showed PDS patients partially maintained surgical level ROM and non-surgical level ROM increased less than in the fusion group. MRI showed adjacent segment degeneration (ASD) in both groups, and patients whose preoperative L3–4 Pfirrmann classification was higher than grade 2 had more ASD than lower than grade 2.ConclusionPDS can maintain surgical level ROM and had less influence on whole and non-surgical level ROM. Following PDS, patients recovered faster and had a better lumbar function. It may be a better choice for multi-level lumbar degenerative diseases.

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Biomechanical Effects of Disc Degeneration and Hybrid Fixation on the Transition and Adjacent Lumbar Segments

Cited by 43 publications

References 26 publications

Biomechanical Investigation about Traditional and Cortical Trajectory Screws of Static and Dynamic Lumbar Fixation

Biomechanical Investigation about Traditional and Cortical Trajectory Screws of Static and Dynamic Lumbar Fixation

Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion: A finite element analysis

The influence of L4–S1 Dynesys® dynamic stabilization versus fusion on lumbar motion and its relationship with lumbar degeneration: a retrospective study

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