40 results on '"Guo Li-Xin"'
Search Results
2. Prediction of the biomechanical behaviour of the lumbar spine under multi‐axis whole‐body vibration using a whole‐body finite element model.
- Author
-
Zhang, Chi and Guo, Li‐Xin
- Subjects
- *
WHOLE-body vibration , *FINITE element method , *LUMBAR vertebrae , *LUMBAR pain , *INTERVERTEBRAL disk , *HUMAN body - Abstract
Low back pain has been reported to have a high prevalence among occupational drivers. Whole‐body vibration during the driving environment has been found to be a possible factor leading to low back pain. Vibration loads might lead to degeneration and herniation of the intervertebral disc, which would increase incidence of low back problems among drivers. Some previous studies have reported the effects of whole‐body vibration on the human body, but studies on the internal dynamic responses of the lumbar spine under multi‐axis vibration are limited. In this study, the internal biomechanical response of the intervertebral disc was extracted to investigate the biomechanical behaviour of the lumbar spine under a multi‐axial vibration in a whole‐body environment. A whole‐body finite element model, including skin, soft tissues, the bone skeleton, internal organs and a detailed ligamentous lumbar spine, was used to provide a whole‐body condition for analyses. The results showed that both vibrations close to vertical and fore‐and‐aft resonance frequencies would increase the transmission of vibrations in the intervertebral disc, and vertical vibration might have a greater effect on the lumbar spine than fore‐and‐aft vibration. The larger deformation of the posterior region of the intervertebral disc in a multi‐axis vibration environment might contribute to the higher susceptibility of the posterior region of the intervertebral disc to injury. The findings of this study revealed the dynamic behaviours of the lumbar spine in multi‐axis vehicle vibration conditions, and suggested that both vertical and fore‐and‐aft vibration should be considered for protecting the lumbar health of occupational drivers. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. Topology optimization and dynamic characteristic evaluation of W-shaped interspinous process device.
- Author
-
Guo, Li-Xin and Liu, Juan
- Subjects
- *
LUMBAR vertebrae , *FINITE element method , *ARTIFICIAL implants , *TOPOLOGY , *RANGE of motion of joints - Abstract
For reducing the adjacent segment degeneration of the lumbar spine, the interspinous process device as a kind of flexible non-fusion device was designed to overcome the deficiencies associated with rigid fusion devices. However, it was not clear how the interspinous process device influenced the human spine system, especially the lumbar spine under a vibration environment. This study was designed to evaluate the effect of StenoFix under the vibration condition and also to optimize the structure of the device to obtain better biomechanical performance. A finite element model of the intact lumbar spine was developed and validated. The surgical finite element model was constructed by implanting the interspinous process device StenoFix. Using topology optimization, a new device StenoFix-new was redesigned. The results showed that the interspinous process device decreased vibration amplitudes of annulus stress and intradiscal pressure under vibration at the surgical level. The redesigned StenoFix-new with the smaller stiffness exhibited a better dynamic flexibility performance than StenoFix. In addition, the range of motions of StenoFix-new was closer to the intact model than StenoFix at the surgical level. These results might encourage the designers to give more consideration to the dynamic characteristics of the human spine on the premise of ensuring the safety and strength of implanted devices. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
4. Biomechanical analysis of lumbar nonfusion dynamic stabilization using a pedicle screw‐based dynamic stabilizer or an interspinous process spacer.
- Author
-
Fan, Wei, Zhang, Chi, Zhang, Dong‐Xiang, Guo, Li‐Xin, and Zhang, Ming
- Subjects
LUMBAR vertebrae ,FINITE element method ,RANGE of motion of joints ,DEAD loads (Mechanics) ,BIOMECHANICS - Abstract
This study aimed to investigate and compare the effects of two widely used nonfusion posterior dynamic stabilization (NPDS) devices, pedicle screw‐based dynamic stabilizer (PSDS) and interspinous process spacer (IPS), on biomechanics of the implanted lumbar spine under static and vibration loadings. The finite element model of healthy human lumbosacral segment was modified to incorporate NPDS device insertion at L4–L5 segment. Bioflex and DIAM were used as PSDS‐based and IPS‐based NPDS devices, respectively. As a comparison, lumbar interbody fusion with rigid stabilization was also simulated at L4–L5. For static loading, segmental range of motion (ROM) of the models under moments of four physiological motions was computed using hybrid testing protocol. For vibration loading, resonant modes and dynamic stress of the models under vertical excitation were extracted through random response analysis. The results showed that compared with the rigid fusion model, ROM of the nonfusion models was higher at L4–L5 level but lower at adjacent levels (L1– L2, L2–L3, L3–L4, L5–S1). Compared with the Bioflex model, the DIAM model produced higher ROM at L4–L5 level but lower ROM at adjacent levels, especially under lateral bending and axial rotation; resonant frequency of the DIAM model was slightly lower; dynamic response of nucleus stress at L4–L5 level was slightly higher for the DIAM model, and the dynamic stress at adjacent levels was no obvious difference between the nonfusion models. This study reveals biomechanical differences between the Bioflex and DIAM systems, which may provide references for selecting surgical approaches in clinical practice. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
5. Development and Validation of a Whole Human Body Finite Element Model with Detailed Lumbar Spine.
- Author
-
Guo, Li-Xin and Zhang, Chi
- Subjects
- *
LUMBAR vertebrae , *FINITE element method , *HUMAN body , *WHOLE-body vibration , *LUMBAR pain - Abstract
Investigations showed that low back pain of occupational drivers might be closely related to the whole-body vibration. Restricted by ethical concerns, the finite element method had become a viable alternative to invasive human experiments. Many mechanical behaviors of the human spine inside of the human body were unclear; therefore, a human whole-body finite element model might be required to better understand the lumbar behavior under whole-body vibration. In this study, a human whole-body finite element model with a detailed lumbar spine segment was developed. Several validations were performed to ensure the correctness of this model. The results of anthropometry and geometry validation, static validation, and dynamic validation were presented in this study. The validation results showed that the whole human body model was reasonable and valid by comparing with published data. The model developed in this study could reflect the biomechanical response of the human lumbar spine under vibration and could be used in further vibration analysis and offer proposals for protecting human body under whole-body vibration environment. [Display omitted] [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
6. Biomechanical role of cement augmentation in the vibration characteristics of the osteoporotic lumbar spine after lumbar interbody fusion.
- Author
-
Wang, Qing-Dong and Guo, Li-Xin
- Subjects
LUMBAR vertebrae ,WHOLE-body vibration ,OSTEOPOROSIS ,CEMENT ,FINITE element method ,HUMAN body - Abstract
Under whole body vibration, how the cement augmentation affects the vibration characteristic of the osteoporotic fusion lumbar spine, complications, and fusion outcomes is unclear. A L1-L5 lumbar spine finite element model was developed to simulate a transforaminal lumbar interbody fusion (TLIF) model with bilateral pedicle screws at L4-L5 level, a polymethylmethacrylate (PMMA) cement-augmented TLIF model (TLIF-PMMA) and an osteoporotic TLIF model. A 40 N sinusoidal vertical load at 5 Hz and a 400 N preload were utilized to simulate a vertical vibration of the human body and the physiological compression caused by muscle contraction and the weight of human body. The results showed that PMMA cement augmentation may produce a stiffer pedicle screw/rod construct and decrease the risk of adjacent segment disease, subsidence, and rod failure under whole-body vibration(WBV). Cement augmentation might restore the disc height and segmental lordosis and decrease the risk of poor outcomes, but it might also increase the risk of cage failure and prolong the period of lumbar fusion under WBV. The findings may provide new insights for performing lumbar interbody fusion in patients affected by osteoporosis of the lumbar spine. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
7. Biomechanical Investigation of Lumbar Interbody Fusion Supplemented with Topping-off Instrumentation Using Different Dynamic Stabilization Devices.
- Author
-
Fan, Wei and Guo, Li-Xin
- Subjects
- *
SPINAL fusion , *FINITE element method , *LUMBAR vertebrae , *BENDING moment , *RANGE of motion of joints , *DEAD loads (Mechanics) , *LUMBAR vertebrae surgery , *SPINE diseases , *KINEMATICS - Abstract
Study Design: A biomechanical comparison study using finite element method.Objective: The aim of this study was to investigate effects of different dynamic stabilization devices, including pedicle-based dynamic stabilization system (PBDSS) and interspinous process spacer (ISP), used for topping-off implants on biomechanical responses of human spine after lumbar interbody fusion.Summary Of Background Data: Topping-off stabilization technique has been proposed to prevent adjacent segment degeneration following lumbar spine fusion. PBDSS and ISP are the most used dynamic stabilizers for topping-off instrumentation. However, biomechanical differences between them still remain unclear.Methods: A validated, normal FE model of human lumbosacral spine was employed. Based on this model, rigid fusion at L4-L5 and moderately disc degeneration at L3-L4 were simulated and used as a comparison baseline. Subsequently, Bioflex and DIAM systems were instrumented at L3-L4 segment to construct PBDSS-based and ISP-based topping-off models. Biomechanical responses of the models to bending moments and vertical vibrational excitation were computed using FE static and random response analyses, respectively.Results: Results from static analysis showed that at L3-L4, the response parameters including annulus stress and range of motion were decreased by 41.6% to 85.2% for PBDSS-based model and by 6.3% to 67% for ISP-based model compared with rigid fusion model. At L2-L3, these parameters were lower in ISP-based model than in PBDSS-based model. Results from random response analysis showed that topping-off instrumentation increased resonant frequency of spine system but decreased dynamic response of annulus stress at L3-L4. PBDSS-based model generated lower dynamic stress than ISP-based model at L3-L4, but the dynamic stress was higher at L2-L3 for PBDSSbased model.Conclusion: Under static and vibration loadings, the PBDSSbased topping-off device (Bioflex) provided a better protection for transition segment, and likelihood of degeneration of supraadjacent segment might be relatively lower when using the ISPbased topping-off device (DIAM).Level of Evidence: 5. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
8. Biomechanical analysis of lumbar interbody fusion supplemented with various posterior stabilization systems.
- Author
-
Fan, Wei, Guo, Li-Xin, and Zhang, Ming
- Subjects
- *
LUMBAR vertebrae , *BENDING moment , *YIELD stress , *BONE grafting , *FINITE element method , *BIOMECHANICS - Abstract
Purpose: Biomechanical comparison between rigid and non-rigid posterior stabilization systems following lumbar interbody fusion has been conducted in several studies. However, most of these previous studies mainly focused on investigating biomechanics of adjacent spinal segments or spine stability. The objective of the present study was to compare biomechanical responses of the fusion devices when using different posterior instrumentations. Methods: Finite-element model of the intact human lumbar spine (L1–sacrum) was modified to simulate implantation of the fusion cage at L4–L5 level supplemented with different posterior stabilization systems including (i) pedicle screw-based fixation using rigid connecting rods (titanium rods), (ii) pedicle screw-based fixation using flexible connecting rods (PEEK rods) and (iii) dynamic interspinous spacer (DIAM). Stress responses were compared among these various models under bending moments. Results: The highest and lowest stresses in endplate, fusion cage and bone graft were found at the fused L4–L5 level with DIAM and titanium rod stabilization systems, respectively. When using PEEK rod for the pedicle screw fixation, peak stress in the pedicle screw was lower but the ratio of peak stress in the rods to yield stress of the rod material was higher than using titanium rod. Conclusions: Compared with conventional rigid posterior stabilization system, the use of non-rigid stabilization system (i.e., the PEEK rod system and DIAM system) following lumbar interbody fusion might increase the risks of cage subsidence and cage damage, but promote bony fusion due to higher stress in the bone graft. For the pedicle screw-based rod stabilization system, using PEEK rod might reduce the risk of screw breakage but increased breakage risk of the rod itself. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
9. Posterior Lumbar Interbody Fusion Versus Transforaminal Lumbar Interbody Fusion: Finite Element Analysis of the Vibration Characteristics of Fused Lumbar Spine.
- Author
-
Fan, Wei, Guo, Li-Xin, and Zhao, Dan
- Subjects
- *
SPINAL fusion , *LUMBAR vertebrae , *FINITE element method , *WHOLE-body vibration , *COMPRESSION loads , *STRAINS & stresses (Mechanics) , *DEAD loads (Mechanics) - Abstract
Previous studies have investigated biomechanical characteristics of the lumbar spine after different types of lumbar interbody fusion surgery under static loadings. However, very few have dealt with the whole-body vibration (WBV) condition that is typically present in vehicles. The aim of this study was to compare the influence of posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) on dynamic responses of the fused lumbar spine to vertical WBV. The PLIF and TLIF procedures with bilateral pedicle screw fixation at L4-L5 level were simulated by modifying a previously validated intact lumbar L1-S1 finite element model. The PLIF and TLIF models were subjected to a sinusoidal vertical load with a compressive follower preload, and computed for transient dynamic analysis. The obtained dynamic responses for the models at the fused and adjacent levels were collected and compared. The results showed that the contact force between endplate and cage was higher in the PLIF model than in the TLIF model, indicating that PLIF allowed for higher compressive load across the anterior structure. At fused L4-L5 level, the TLIF led to a higher stress in the endplate and posterior BPSF system than the PLIF. At adjacent L3-L4 level and L5-S1 level, the computed dynamic responses, in terms of stress and deformation, for the PLIF and TLIF models showed very few differences. This study may be helpful to quantify dynamic mechanical properties of the fused lumbar spine, and better understand biomechanical differences between the PLIF and TLIF procedures during vibration. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
10. Prediction of complications and fusion outcomes of fused lumbar spine with or without fixation system under whole-body vibration.
- Author
-
Wang, Qing-Dong and Guo, Li-Xin
- Subjects
- *
LUMBAR vertebrae abnormalities , *ORTHOPEDIC implants , *LUMBAR vertebrae physiology , *FINITE element method , *BIOMECHANICS - Abstract
Lumbar fixator has been widely used, which can stabilize the lumbar spine and improve the fusion outcomes, but also lead to many complications. The effects of the internal fixator on biomechanical properties of the fused lumbar spine have been widely concerned for many years. However, most studies only considered the static loads and did not consider the effect of the fixator on the properties of the human lumbar spine under whole-body vibration (WBV). The purpose of this study is to investigate how the fixation system affects the biomechanical characteristics of the lumbar spine, fusion outcomes, and complications under WBV based on the finite element analysis. A three-dimensional nonlinear osteoligamentous finite element model of the intact L1-sacrum spine with muscles was established. A 5-Hz, 40-N sinusoidal vertical load supplemented with a 400-N preload was applied at L1 to simulate the vibration of the human body. For the adjacent segments, the fixation system may increase the risk of the adjacent segment disease under WBV. For the fused segments, the fixation system may decrease the risk of subsidence and cage failure including fatigue failure under WBV. The fixation system may provide a more stable and suitable environment for vertebral cell growth under WBV and lead to better fusion outcomes. This study reveals insights into the effect of the fixation system on the vibration characteristics of the lumbar and provides new information on the fixation system, fusion outcomes, complications, clinical evaluation, and selection of fixation system. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
11. Comparison of dynamic response of three TLIF techniques on the fused and adjacent segments under vibration.
- Author
-
Wang, Qing-Dong and Guo, Li-Xin
- Subjects
- *
CELL growth , *FINITE element method - Abstract
To explore which TLIF techniques are advantageous in reducing the risk of complications and conducive to bone fusion under the vibration. The L1–L5 finite element lumbar model was modified to simulate three different TLIF techniques (a unilateral standard cage, a crescent-shaped cage, and bilateral standard cages). The results showed that the crescent-shaped cage may reduce the risk of subsidence and provide a more stable and suitable environment for vertebral cell growth under the vibration compared to the other TLIF techniques. Unilateral cage may increase the risk of adjacent segment disease and cage failure including fatigue failure under vibration. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
12. Study on the transient electromagnetic scattering from multiple targets above a rough surface with time‐domain FEM‐PML.
- Author
-
He, Hong‐Jie, Guo, Li‐Xin, and Zhang, Ya
- Subjects
- *
ELECTROMAGNETIC wave scattering , *ROUGH surfaces , *SCATTERING (Physics) , *FINITE element method , *INTEGRAL equations , *SURFACE morphology - Abstract
The time‐domain finite‐element method (TDFEM) is extended to study the two‐dimensional transient electromagnetic scattering from multiple targets above a rough surface in this article. The perfectly matched layer is employed as the truncation boundary of TDFEM region to absorb the outward wave scattered from the model. To introduce the incident wave, a total field boundary, which splits the whole region into total‐ and scattered‐field regions is built around the composite model. To model the composite scattering, the total‐ and scattered‐field formulas are used in these two regions, respectively. Numerical results are presented to demonstrate the accuracy, efficiency, and flexibility of the method. The results show that the proposed method is significantly superior to the time‐domain integral equation method in terms of solving time. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
13. Finite element modeling and static/dynamic validation of thoracolumbar-pelvic segment.
- Author
-
Guo, Li-Xin and Li, Wu-Jie
- Subjects
- *
INTERVERTEBRAL disk , *FINITE element method , *ZYGAPOPHYSEAL joint , *HUMAN mechanics , *REACTION forces - Abstract
Finite element method is an efficient tool to investigate the biomechanics of human spine. The key to finite element method is to reconstruct a complete and accurate finite element model. In this study, a three-dimensional finite element model of thoracolumbar structure including complete pelvis (T12-pelvis) was built using computed tomography technology. The modeling process has been explained in detailed. During the process of validation, the model was assigned with non-linear material property for static or dynamic analyses. In static analysis, the vertebral geometry parameters of T12-L5, the axial displacement, the posterior disc bulge and the intradiscal pressure of intervertebral disc, range of motion under six loading cases and facet joint forces were obtained and compared with the experimental data. In dynamic analysis, motion segments were loaded with sinusoidal displacement at 1 Hz in the anterior–posterior and axial directions to verify the reaction force. The first-order resonant frequencies in the vertical direction from one motion segment and two motion segments to the entire model were obtained. The study provides a detailed and accurate method of validation to verify the finite element model of thoracolumbar spine. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
14. A biomechanical investigation of thoracolumbar burst fracture under vertical impact loads using finite element method.
- Author
-
Guo, Li-Xin and Li, Wu-Jie
- Subjects
- *
NERVOUS system injuries , *NEUROLOGICAL disorder prevention , *LUMBAR vertebrae , *BIOMECHANICS , *CHEST injuries , *COMPACT bone , *FINITE element method , *BONE fractures , *MEDICAL practice , *SPINAL injuries , *PHYSIOLOGIC strain , *WOUNDS & injuries - Abstract
A sudden vertical impact load on spine can cause spinal burst fracture, especially in the thoracolumbar junction region. This study aimed at investigating the mechanism of spinal burst fracture under different energy vertical impact loads, producing the failure risk region to understand burst fracture, reducing nervous system damage and guiding clinical treatment. A nonlinear finite element model of T12-L1 motion segment was created to analyze the response of the vertical impact load. A rigid ball was used to impact the segment vertically to simulate the vertical impact load in practice. There were three different mass balls to represent the different loads: low energy, intermediate energy and high energy (respectively 13 J, 30 J and 56 J). The results of impact force, vertical displacement, stress, intradiscal pressure and contact force were obtained during the process. At low energy condition, the rigid ball rebounded rapidly. At intermediate energy condition, fractures were initiated in vertebral foramen and left rear regions on the superior cortical bone near the superior endplate of L1. At high energy condition, burst fracture occurred and a part of L1 was isolated from the model. The fracture occurred on the L1 segment only at the intermediate energy and high energy. The strength of vertebral body under low and intermediate energy was enough to support the impact. The burst fracture pattern at high energy was also observed in clinical practice. The findings may explain the mechanism of burst fracture. • Simulating the impact test of drop tower • Reproducing burst fracture under three weights • Spinal finite element model was assigned with failure material. • The burst fracture process including initiation, propagation and termination was obtained. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
15. Biomechanical comparison of the effects of anterior, posterior and transforaminal lumbar interbody fusion on vibration characteristics of the human lumbar spine.
- Author
-
Fan, Wei and Guo, Li-Xin
- Subjects
- *
LUMBAR vertebrae , *BIOMECHANICS , *SPINAL fusion , *WHOLE-body vibration , *FINITE element method - Abstract
Previous studies have compared the effects of different interbody fusion approaches on biomechanical responses of the lumbar spine to static loadings. However, very few have dealt with the whole body vibration (WBV) condition that is typically present in vehicles. This study was designed to determine the biomechanical differences among anterior, posterior and transforaminal lumbar interbody fusion (ALIF, PLIF and TLIF) under vertical WBV. A previously developed and validated finite element (FE) model of the intact L1–sacrum human lumbar spine was modified to simulate ALIF, PLIF and TLIF with bilateral pedicle screw fixation at L4–L5. Comparative studies on dynamic responses to the axial cyclic loading in these developed models were conducted. The results showed that at the fused L4–L5 level, dynamic responses of the von-Mises stress in L4 inferior and L5 superior endplates for the ALIF, PLIF and TLIF models were increased compared with the intact model. The endplate stresses in the TLIF model were lower than in the ALIF and PLIF models, but the TLIF generated greater stresses in the screws and rods compared with the ALIF and PLIF. At other levels, a decrease in dynamic responses of the disc bulge, annulus stress and intradiscal pressure was observed in all the fusion models compared with the intact one, but there was no obvious difference in these dynamic responses among the ALIF, PLIF and TLIF models. These findings might be useful in understanding vibration characteristics of the whole lumbar spine after different types of fusion surgery. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
16. Impact of material properties of intervertebral disc on dynamic response of the human lumbar spine to vertical vibration: a finite element sensitivity study.
- Author
-
Guo, Li-Xin and Fan, Wei
- Subjects
- *
INTERVERTEBRAL disk , *LUMBAR vertebrae , *FINITE element method , *SENSITIVITY analysis , *NUCLEUS pulposus , *LUMBAR vertebrae physiology , *BIOLOGICAL models , *VIBRATION (Mechanics) , *IMPACT of Event Scale , *PHYSIOLOGY - Abstract
This study aimed to determine the effect of variations in material properties of the intervertebral disc on dynamic response of the human lumbar spine to vertical vibration using a finite element model of the lumbar L1-S1 motion segment. The present material sensitivity study was conducted by varying elastic moduli for annulus ground substance (AGS), annulus fibers (AF), and nucleus pulposus (NP) in the disc. Transient dynamic analysis was performed initially on the model with basic material property under a sinusoidal vertical vibration load. Subsequently, the same analysis was done for each of the three disc components corresponding to high and low material property cases. The computed results were plotted as a function of time and compared. The AGS property displayed a larger impact on vertebral axial displacement and von Mises stress in AGS, and the AF property displayed a larger impact on disc bulge. In contrast, the NP property had little effect on all the response parameters. Additionally, the intradiscal pressure was found to be not sensitive to any of the disc properties. These findings may be helpful in adoption of appropriate material parameters for the intervertebral disc in finite element model of the lumbar spine used for vibration analysis. Graphical abstract Material property sensitivity analysis on vibration characteristics of the human lumbar spine. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
17. Finite element analysis and design of an interspinous device using topology optimization.
- Author
-
Guo, Li-Xin and Yin, Jia-Yu
- Subjects
- *
TOPOLOGY , *MATHEMATICAL optimization , *FINITE element method , *SPINAL stenosis , *BIOMECHANICS , *LUMBAR vertebrae surgery , *RANGE of motion of joints , *PROSTHETICS , *PHYSIOLOGIC strain ,RESEARCH evaluation - Abstract
Recently, interspinous stabilization with Coflex-F implant has become an alternative to treat lumbar spinal stenosis (LSS). However, little attention focused on modifying the structure of the device to obtain the better clinic application. The purpose of this study was to design a new interspinous implant using topology optimization methods and evaluate its biomechanical performance. The finite element models of healthy lumbar spine and surgical lumbar spine with Coflex-F and Coflex-NEW (the new designed implant) were constructed. Finite element analysis was applied to each of the three models. The interspinous implant structure after topology optimization was remodeled at an 8% reduced volume compared with the Coflex-F device, and they can both provide stability in all motion at the surgical segment. Additionally, the advantage of Coflex-NEW was that it can decrease the von Mises stress of the implant structure in flexion, extension, torsion, and the spinous process in flexion, extension, and bending. The stress in spinous process with Coflex-NEW was well-distributed. Graphical abstract ᅟ. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
18. Evolution of linear edge dislocation in atmospheric turbulence and free space.
- Author
-
Gao, Peng-hui, Bai, Lu, Wu, Zhen-sen, and Guo, Li-xin
- Subjects
ATMOSPHERIC turbulence ,FINITE element method ,FREE-space optical technology ,NUMERICAL analysis ,GIRDERS - Abstract
In accordance with the extended Huygens-Fresnel principle, the evolution of linear edge dislocation propagating through atmospheric turbulence is studied, and the effects of waist width and the slope of linear edge dislocation are investigated. It is shown that when linear edge dislocation beams propagate through atmospheric turbulence, if the waist width is not equal and the slope is not zero, then the linear edge dislocation vanishes and transforms into an optical vortex with a topological charge of −1 or +1. The optical vortex and an optical vortex that is created annihilate when the transmission distance is far enough. The linear edge dislocation vanishes when the slope is zero. If the waist width is equal, then the linear edge dislocation will vanish regardless of the slope value. For linear edge dislocation beams in free space, when selecting specific parameters, linear edge dislocation always exists. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
19. Biomechanical Comparison of the Influence of Osteoporosis on the Lumbar Spine After Lumbar Interbody Fusion Surgery or Non-fusion Dynamic Stabilization Surgery Under Whole Body Vibration.
- Author
-
Fan, Wei, Zhang, Chi, Zhang, Dong-Xiang, Wang, Qing-Dong, and Guo, Li-Xin
- Subjects
WHOLE-body vibration ,BONE density ,LUMBAR vertebrae ,OSTEOPOROSIS ,CYCLIC loads ,FINITE element method ,ARTIFICIAL implants - Abstract
The objective of this study was to determine and compare the influence of osteoporosis on biomechanics of the spine after lumbar interbody fusion (LIF) surgery or non-fusion dynamic stabilization (NFDS) surgery under whole body vibration (WBV) which is typically present in moving vehicles. Based on a previously validated finite element (FE) model of normal human lumbosacral spine, four surgical models including LIF, LIF with osteoporosis (LIF-OST), NFDS, and NFDS with osteoporosis (NFDS-OST) were constructed. Biomechanical responses of the surgical models to an axial cyclic load were calculated using transient dynamic analysis. Response parameters include vibration amplitudes of the endplate stress and screw stress at surgical L4–L5 level, vibration amplitudes of the disc bulge and intradiscal pressure at adjacent L3–L4 level. Osteoporosis increased vibration amplitudes of all these investigated response parameters. Further, we found that vibration amplitudes of the endplate stress and screw stress for the LIF-OST model were significantly higher than those for the NFDS-OST model, but there was very small difference in vibration amplitudes of the disc bulge and intradiscal pressure between the LIF-OST and NFDS-OST models. For both the LIF and NFDS surgeries, osteoporosis might increase the risk for implant failure and accelerate adjacent segment degeneration (ASD) under WBV. When osteoporosis occurs, LIF might be associated with a higher likelihood of implant failure at the surgical level compared with NFDS, and the surgical approach (LIF or NFDS) might have little influence on biomechanics of the adjacent level. • Finite element models of surgical lumbar spine with osteoporosis were created. • Fusion surgery and non-fusion dynamic stabilization surgery were considered. • Dynamic responses of the surgical models to whole body vibration were computed. • Effects of osteoporosis on the fusion and non-fusion models were compared. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
20. Finite element investigation of the effect of nucleus removal on vibration characteristics of the lumbar spine under a compressive follower preload.
- Author
-
Fan, Wei and Guo, Li-Xin
- Subjects
LUMBAR vertebrae ,BIOMECHANICS ,VIBRATION (Mechanics) ,DEAD loads (Mechanics) ,FINITE element method ,ANATOMY - Abstract
Previous studies have reported the effect of removing the nucleus on biomechanical responses of the human spine to static loadings. However, few studies have dealt with the whole-body vibration condition. The purpose of this study was to investigate the effect of a single-level (L4–L5) nucleus removal on vibration characteristics of the whole lumbar spine in the presence of a physiologic compressive preload, and also to evaluate the preload effect on the vibration characteristics. A 3-D non-linear finite element model of the lumbar spine (L1 to sacrum) subjected to the physiologic conditions of a compressive follower preload was developed and validated. Comparative studies on forced vibration responses between the intact and denucleated models were conducted. The results from the forced-vibration (transient dynamic) analyses considering axial cyclic loading indicated that the nucleus removal increased the dynamic responses at all disc levels. For example, at the denucleated L4–L5 level, after nucleus removal the maximum response values of disc bulge and von-Mises stress in annulus increased by 63.9% and 110.5% respectively, and their vibration amplitudes increased by 97.9% and 139.7% respectively. At other levels, the predicted maximum response values and vibration amplitudes of the stresses and strains also produced 3.1–7.5% and 10.8–30.6% increases respectively due to the nucleus removal, and a relatively larger increase was observed at level L5–S1. It was also found that increasing the preload increased the stresses and strains at all levels but decreased their vibration amplitudes. Nucleus removal at a single level deteriorates the effects of vibration on whole lumbar spine. Also, increasing the preload alters vibration characteristics of the spine. These findings may be useful to provide a guideline for the patients suffering from lumbar disc degeneration to minimize the risk of further injury and discomfort. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
21. The Effect of Single-Level Disc Degeneration on Dynamic Response of the Whole Lumbar Spine to Vertical Vibration.
- Author
-
Guo, Li-Xin and Fan, Wei
- Subjects
- *
LUMBAR vertebrae , *DEGENERATION (Pathology) , *COMPRESSION loads , *FINITE element method , *REACTION time - Abstract
Objective The objective of this study was to investigate the effect of single-level disc degeneration on dynamic response of the whole lumbar spine to vertical whole body vibration that is typically present when driving vehicles. Methods Ligamentous finite element models of the lumbar L1-S1 motion segment in different grades of degeneration (healthy, mild, and moderate) at the L4-L5 level were developed with consideration of changing disc height and material properties of the nucleus pulpous. All models were loaded with a compressive follower preload of 400 N and a sinusoidal vertical vibration load of ±40 N. After transient dynamic analyses, computational results for the 3 models in terms of disc bulge, von-Mises stress in annulus ground substance, and nucleus pressure were plotted as a function of time and compared. Results All the predicted results showed a cyclic response with time. At the degenerated L4-L5 disc level, as degeneration progressed, maximum value of the predicted response showed a decrease in disc bulge and von-Mises stress in annulus ground substance but a slight increase in nucleus pressure, and their vibration amplitudes were all decreased. At the adjacent levels of the degenerated disc, there was a slight decrease in maximum value and vibration amplitude of these predicted responses with the degeneration. Conclusions The results indicated that single-level disc degeneration can alter vibration characteristics of the whole lumbar spine especially for the degenerated disc level, and increasing the degeneration did not deteriorate the effect of vertical vibration on the spine. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
22. An Efficient Hybrid Method for 3D Scattering from Inhomogeneous Object Buried beneath a Dielectric Randomly Rough Surface.
- Author
-
He, Hong-jie, Guo, Li-xin, and Liu, Wei
- Subjects
ELECTROMAGNETIC wave scattering ,SCATTERING (Physics) ,CLOAKING devices ,FINITE element method ,NUMERICAL analysis - Abstract
An efficient iterative analytical-numerical method is proposed for three-dimensional (3D) electromagnetic scattering from an inhomogeneous object buried beneath a two-dimensional (2D) randomly dielectric rough surface. In the hybrid method, the electric and magnetic currents on the dielectric rough surface are obtained by current-based Kirchhoff approximation (KA), while the scattering from the inhomogeneous object is rigorously studied by finite element method (FEM) combined with the boundary integral method (BIM). The multiple interactions between the buried object and rough surface are taken into account by updating the electric and magnetic current densities on them. Several numerical simulations are considered to demonstrate the algorithm’s ability to deal with the scattering from the inhomogeneous target buried beneath a dielectric rough surface, and the effectiveness of our proposed method is also illustrated. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
23. Composite Scattering from an Arbitrary Dielectric Target above the Dielectric Rough Surface with FEM/PML
- Author
-
Guo Li-Xin, XU Run-Wen, and Fan Tian-Qi
- Subjects
Permittivity ,Materials science ,Scattering ,business.industry ,Composite number ,Mathematical analysis ,Physics::Optics ,General Physics and Astronomy ,Boundary (topology) ,Dielectric ,Domain (mathematical analysis) ,Finite element method ,Mathematics::Numerical Analysis ,Perfectly matched layer ,Optics ,business - Abstract
A numerical approach of the finite element method is extended to study the scattering properties of an arbitrary dielectric target above the dielectric rough surface. For scattering in an open region, the artificial boundaries should be introduced to truncate the infinite computational domain. A perfectly matched layer (PML), as the artificial boundary of the finite-element-method (FEM) region, is employed to absorb the outward wave scattered from the model. The strategies of hybrid FEM/PML are presented with their validity evaluated by finite element/boundary integral method (FE/BIM), and then the scattering properties of the dielectric composite problem with different material permittivity are discussed in detail. Compared with the published works about FEM/PML, we extend the FEM/PML into the simulations of a dielectric target above the dielectric rough surface.
- Published
- 2013
24. Effect of different fixation methods on biomechanical property of cervical vertebral body replacement and fusion.
- Author
-
Zhang, Dong-Xiang and Guo, Li-Xin
- Subjects
- *
CERVICAL vertebrae , *INTERNAL fixation in fractures , *FINITE element method , *PHYSIOLOGICAL stress , *SPINAL fusion , *VERTEBRAE , *BONE screws , *OSTEOPOROSIS , *SPINAL injuries , *DESCRIPTIVE statistics , *BIOMECHANICS ,SURGICAL complication risk factors - Abstract
The main purpose of this study was to examine the effect of different fixation methods (anterior fixation, self-stabilizing fixation and anterior-posterior fixation) on biomechanical property of vertebral body replacement and fusion. Three finite element models of cervical vertebral body replacement and fusion were established. The implanted models included artificial vertebral body and fixation system, and the loads imposed on the models included 75 N compression load and 1 Nm moment load. For anterior-posterior fixation, the cervical load was mainly transmitted by the posterior pedicle screw and rod (more than 50%), and the stress shielding problem was the most significant than the self-stabilizing and anterior fixation. Self-stabilizing fixation was more helpful to the fusion of implant and vertebrae, but the higher risk of vertebral body collapse was worthy of attention if the cervical spine with osteoporosis. The stress of bone was mainly concentrated around the screw hole. The maximum stress (20.03 MPa) was lower than the yield stress of cortical bone and the possibility of fracture around the fixation device of cervical spine was low. The anterior fixation could meet the requirement of vertebral body replacement and fusion, and the addition of posterior pedicle screws and rods might obtain better treatment in cases of severe spine injury or osteoporosis. The findings of this study may provide guidance on clinical treatments for choosing more appropriate fixation methods for different patients. • Anterior fixation can satisfy the requirements of vertebral body replacement. • The self-stabilizing fixation has the highest fusion rate of implants and vertebrae. • Stiffness of the posterior pedicle screw and rod is larger than the anterior plate and AVB. • The anterior-posterior fixation model has the highest risk of stress shielding. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
25. Study on scattering from multilayer rough surfaces with an object buried with FEM/PML.
- Author
-
Xu, Run‐Wen, Guo, Li‐Xin, He, Hong‐Jie, and Liu, Wei
- Subjects
- *
MULTILAYER waveguides , *ROUGH surfaces , *FINITE element method , *PERFECTLY matched layers (Mathematical physics) , *MATHEMATICAL proofs - Abstract
ABSTRACT The two-dimensional electromagnetic scattering properties from multilayer rough surfaces with an object buried were studied in this article by the finite element method (FEM). When FEM is applied to analyze an open-space scattering problem and an artificial boundary needs to be built to truncate the computational domain. The perfectly matched layer (PML) has been proved to be an accurate boundary condition in the electromagnetic scattering problems. It is widely used in the electromagnetic simulations for limited objects. However, there are few articles provided to deal with the scattering problem of the multilayer rough surfaces. In this letter, the modeling of multilayer rough surfaces with an object buried is presented, and the application of FEM and PML is provided in detail. The method is validated by the method of moments (MoM), and some numerical results are provided to discuss the scattering properties. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:429-433, 2016 [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
26. An Investigation of Acoustic Attenuation Performance of Silencers with Mean Flow Based on Three-Dimensional Numerical Simulation.
- Author
-
Fan, Wei and Guo, Li-Xin
- Subjects
- *
SOUND waves , *ATTENUATION (Physics) , *NOISE control , *FLUID flow , *COMPUTER simulation , *FINITE element method , *COMPUTATIONAL fluid dynamics - Abstract
Transmission loss (TL) is often used to evaluate the acoustic attenuation performance of a silencer. In this work, a three-dimensional (3D) finite element method (FEM) is employed to calculate the TL of some representative silencers, namely, circular expansion chamber silencer and straight-through perforated pipe silencer. In order to account for the effect of mean flow that exists inside the silencer, the 3D FEM is used in conjunction with the Computational Fluid Dynamics (CFD) simulation of the flow field. More concretely, the 3D mean flow field is computed by firstly using CFD, and then the obtained mean flow data are imported to an acoustic solution undertaken using FEM. The data transfer between the two steps is accomplished by mesh mapping. The results presented demonstrate good agreement between present TL predictions and previously published experimental and numerical works. Also, the details of the flow inside the silencers may be studied. Furthermore, the effect of mean flow velocity on acoustic attenuation performance of the silencers is investigated. It is concluded that for the studied silencers, in general, increasing flow velocity increases the TL and decreases the resonance peaks. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
27. Electromagnetic scattering from missile target above sea surface with finite element/boundary integral method
- Author
-
Guo Li-Xin, Fan Tian-Qi, and Xu Run-Wen
- Subjects
Surface (mathematics) ,Physics ,Missile ,Scattering ,Mathematical analysis ,General Physics and Astronomy ,Boundary integral method ,Finite element method - Abstract
In this work, the finite element/boundary integral method (FE/BIM) combined with the domain decomposition method is introduced to study the electromagnetic scattering from the target above the rough sea surface. As the integral boundary can be set at anywhere with an arbitrary shape, the conformal truncated boundary is built to reduce the unknowns of the computational region combined with the domain decomposition method. In the interior region, the finite element method is used to solve the problem, whereas the artificial boundary condition can be obtained by the boundary integral method. The strategy of hybrid FE/BIM and the modeling method are presented with their validity evaluated by the method of moment, then bistatic scattering properties of a missile above the sea surface are discussed, and their dependence upon different incident angles, target height, wind speed above the sea, and the size of the missile are discussed in detail. The information of targets and the target detection can be retrieved and analyzed by the results in this paper.
- Published
- 2013
28. Electromagnetic Scattering from Randomly Rough Surfaces with Hybrid FEM/BIE
- Author
-
Li Jie, He Qiong, Guo Li-Xin, and Wei Bing
- Subjects
Physics ,symbols.namesake ,Scattering ,Gaussian ,Mathematical analysis ,symbols ,General Physics and Astronomy ,Boundary (topology) ,Boundary value problem ,Method of moments (statistics) ,Half-space ,Integral equation ,Finite element method - Abstract
The hybrid finite element method (FEM) together with the boundary integral equation (BIE) is firstly applied to scattering from a conducting rough surface. The BIE is used as the truncation boundary condition for the special unbounded half space, whereas the FEM is used to solve the governing equation in the region surrounded by a rough surface and artificial boundary. Tapered wave incidence is employed to cancel the so-called "edge effect". A hybrid FEM/BIE formulation for generalized one-dimensional conducting rough surface scattering is presented, as well as examples that evaluate its validity compared to the method of moments. The bistatic scattering coefficients of a Gaussian rough surface are calculated for transverse-magnetic wave incidence. Conclusions are reached after analyzing the scattering patterns of rough surfaces with different rms heights and correlation lengths
- Published
- 2011
29. An Efficient Multiregion FEM-BIM for Composite Scattering From an Arbitrary Dielectric Target Above Dielectric Rough Sea Surfaces.
- Author
-
Guo, Li-Xin and Xu, Run-Wen
- Subjects
- *
FINITE element method , *ELECTROMAGNETIC wave scattering , *ELECTROMAGNETIC fields , *DIELECTRICS , *ROUGH surfaces - Abstract
An efficient multiregion hybrid method of the finite element method (FEM) combined with the boundary integral method (FEM-BIM) is first proposed for the fast simulation of 2-D scattering from an arbitrary dielectric target above a “Pierson– Moskowitz” rough sea surface. In the implementation of the multiregion hybrid method, the entire model is divided into multiple computational regions depending on energy distribution of an incident wave. With mutual coupling between the target and the dominant region of the sea considered, FEM and BIM are respectively applied to study the target and the dominant region to exactly obtain electromagnetic fields and currents, which have powerful illuminated field and strong interaction with each other. Mutual coupling between different subordinate regions is approximately considered by field integral equations based on Kirchhoff approximation by which the approximate currents in subordinate regions can be obtained. Because FEM and BIM are only performed on the target and the dominant region of the sea, the number of unknowns and the time required in the new method are dramatically reduced than those in the traditional FEM-BIM, making the hybrid method more efficient in the simulation of the composite problem. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
30. Investigation on scattering from a plasma-coated target over a rough sea surface using a multi-hybrid method.
- Author
-
Li, Jie, Guo, Li-Xin, He, Qiong, and Wei, Bing
- Subjects
- *
SCATTERING (Physics) , *OCEAN surface topography , *FINITE element method , *AEROFOILS , *COLLISIONS (Nuclear physics) , *NUMERICAL analysis - Abstract
An iterative strategy combining the Kirchhoff approximation (KA) with the hybrid finite element–boundary integral (FE-BI) method is presented to consider electromagnetic scattering from a coated target above a rough sea surface. The multi-hybrid method considers the multiple-scattering interactions between target and underlying surface based on equivalent principle and currents updating scheme. The hybrid FE-BI-KA method, which is an improved and generalized version of a previous KA–Method of Moments (MoM) technique, can deal with an inhomogeneous target. Numerical results are given to evaluate the validity of the multi-hybrid technique, and then the hybrid method is employed to investigate electromagnetic scattering from a plasma-coated airfoil above a rough sea surface, including the effects of several key parameters on stealth performance, such as plasma angular frequency and electron collision frequency. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
31. Finite Element Modeling and Modal Analysis of the Human Spine Vibration Configuration.
- Author
-
Guo, Li-Xin, Zhang, Yi-Min, and Zhang, Ming
- Subjects
- *
SPINE , *RESONANT vibration , *FINITE element method , *MODAL analysis , *HARMONIC analysis (Mathematics) , *BIOMECHANICS , *COMPUTER simulation - Abstract
This study was designed to investigate the modal characteristics of the human spine. A 3-D finite element model of the spine T12-Pelvis segment was used to extract resonant frequencies and modal modes of the human spine. By finite element modal analysis and harmonic response analysis, several lower vibration modes in the flexion–extension, lateral bending, and vertical directions were obtained and its vibration configurations were shown in this paper. The results indicate that the lowest resonant frequency of the model is in the flexion–extension direction. The second-order resonant frequency is in the lateral bending direction and the third-order resonant frequency of the T12-Pelvis model is in the vertical direction. The results also show that lumbar spinal vertebrae conduct the rotation action during whole body vibration (WBV). The vibration configurations of the lumbar spine can explore the motion mechanism of different lumbar components under WBV and make us to understand the vibration-induced spine diseases. The findings in this study will be helpful to understand WBV-related injury of the spine in clinics and the ergonomics design and development of mechanical production to protect human spine safety. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
32. Influence of anteroposterior shifting of trunk mass centroid on vibrational configuration of human spine
- Author
-
Guo, Li-Xin, Zhang, Ming, Wang, Zhao-Wen, Zhang, Yi-Min, Wen, Bang-Chun, and Li, Jin-Li
- Subjects
- *
POSTURE , *SKELETON , *SPINE , *FINITE element method , *STRUCTURAL dynamics - Abstract
Abstract: This study attempts to determine the influence of anteroposterior (A-P) shifting of trunk mass from the upright sedentary posture on dynamic characteristics of the human lumbar spine. A three-dimensional finite element (FE) model comprising of the T12–Pelvis spine unit was used to mimic the human spine system. It is not clear how the A-P shifting of the upper part of human upper body affect on vibrational modality of the human lumbar spine under whole body vibration. Five trunk mass point locations were assumed by 2.0cm anterior, 1.0cm anterior, 1.0cm posterior and 2.0cm posterior to the upright sedentary posture including no shifting posture. FE modal analysis was used to extract the resonant frequencies and vibration modes of the human spine. The analytical results indicate that trunk mass centroid shifting onwards or rearwards may result in a reduction of vertical resonant frequency of the human spine. The human spine has the highest vertical resonant frequency at the normal upright sedentary posture with the trunk mass locating around 1.0cm anterior to the L3–L4 vertebral centroid. Larger A-P deformations and rotational deformations were also found at the spine motion segments L3–L4 and L4–L5, which imply higher compressive stress and shear stress at the disc annulus of those spinal motion segments. The findings in this study may explain why long-term whole body vibration might induce the degeneration of human spine at the relevant spinal motion segments. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
33. Prediction of the modal characteristics of the human spine at resonant frequency using finite element models.
- Author
-
Guo, Li-Xin and Teo, Ee-Chon
- Subjects
LUMBAR vertebrae physiology ,THORACIC vertebrae ,SACRUM ,PELVIC bones ,BIOLOGICAL models ,COMPARATIVE studies ,COMPUTER simulation ,ELASTICITY ,FINITE element method ,RESEARCH methodology ,MEDICAL cooperation ,RESEARCH ,VIBRATION (Mechanics) ,EVALUATION research ,PHYSIOLOGIC strain ,BODY movement ,PHYSIOLOGY - Abstract
To understand the dynamic characteristics of the human spine, a detailed three-dimensional finite element model of the lower thorax to pelvis segment, T12-pelvis, was developed based on actual vertebral geometry. After modal analysis, the resonant frequencies of different spinal segments were obtained. The vibration mode of T12-pelvis shows that the human upper body mainly performs the vertical motion during whole-body vibration and the lumbar spine segment conducts translation and rotation in the sagittal plane. The lower segments of the lumbar spine move in flexion and the upper lumbar segments move in extension. This investigation may be helpful in understanding further the biomechanical behaviour of the human spine under the condition of whole-body vibration and to offer potential references for spinal disease treatments and product design in industry. [ABSTRACT FROM AUTHOR]
- Published
- 2005
34. Vibration characteristics of the human spine under axial cyclic loads: effect of frequency and damping.
- Author
-
Guo, Li-Xin, Teo, Ee-Chon, Lee, Kim-Kheng, and Zhang, Qing-Hang
- Subjects
- *
LUMBAR vertebrae physiology , *BIOLOGICAL models , *COMPARATIVE studies , *COMPUTER simulation , *DEAD , *FINITE element method , *RESEARCH methodology , *MEDICAL cooperation , *RESEARCH , *PHYSIOLOGICAL stress , *VIBRATION (Mechanics) , *EVALUATION research , *ZYGAPOPHYSEAL joint , *WEIGHT-bearing (Orthopedics) - Abstract
Study Design: A nonlinear finite element model of lumbar spine segment L3-L5 was developed. The effects of upper body mass, nucleus injury, damping, and different vibration frequency loads were analyzed for the whole body vibration.Objectives: To analyze the influence of whole body vibration on facets of lumbar spine and to analyze the influence of nucleus injury, upper body mass, and damping on the dynamic characteristics of lumbar spine.Summary Of Background Data: Many studies have investigated whole body vibration for lumbar spine. However, very few investigations analyzed the influence of whole body vibration on facets and vibration characteristics of the injured spine.Methods: The nonlinear finite element model of the L3-L5 segment was constructed based on the embalmed vertebra geometry and validated. Besides static and modal analyses, transient dynamic analyses were also conducted on the model with an upper body mass under damping and different frequency cyclic loads.Results: In the period of human spine vibration, the vibration effects of different regions of the lumbar spine are not the same. Anterior regions of the L3-L5 segment show small vibration amplitudes, but posterior regions show large amplitudes. The vibration amplitude of facet contact force is more than 2.0-fold as large as that of displacement and stress on vertebrae or discs. To decrease the weight of the upper body will increase the resonant frequency. To remove the nucleus will decrease the resonant frequencies. The vibration displacement, stress, and facet contact force will reduce generally by 50% using damping ratio 0.08.Conclusions: The posterior regions of intervertebral discs of the lumbar spine are easy to injure during long-term whole body vibration compared to anterior regions. The vibration of human spine is more dangerous to facets, especially during whole body vibration approximating a sympathetic vibration, which may lead to abnormal remodeling and disorder of the lumbar spine. [ABSTRACT FROM AUTHOR]- Published
- 2005
- Full Text
- View/download PDF
35. Prediction of the influence of vertical whole-body vibration on biomechanics of spinal segments after lumbar interbody fusion surgery.
- Author
-
Fan, Wei and Guo, Li-Xin
- Subjects
- *
LUMBAR vertebrae physiology , *SPINE physiology , *FINITE element method , *SPINAL fusion , *VIBRATION (Mechanics) , *BIOMECHANICS , *STATISTICAL models , *KINEMATICS - Abstract
Previous studies have shown that for healthy spine, cyclic loading encountered due to whole-body vibration exposure generated higher responses in spinal tissues than static loading. However, how whole-body vibration affects spine biomechanics after interbody fusion surgery is poorly understood. This study aimed at comparing the effects of vibration loading on spinal segments between postsurgical and healthy lumbar spines. A validated finite element model of healthy human lumbosacral spine was modified to simulate interbody fusion at L4–L5 level considering the statuses immediately after surgery (before bony fusion) and after bony fusion. Biomechanical responses at its adjacent levels for the healthy and fusion models to a sinusoidal axial vibration load of ±40 N and the corresponding static axal loads (−40 N and 40 N) were computed using transient dynamic and static analyses, respectively. For both healthy and fusion models, vibration amplitudes of the predicted responses were significantly higher than the corresponding changing amplitudes under static loads. Specifically, the increasing effect of vibration load in disc bulge, disc stress and intradiscal pressure at L3–L4 level reached 255.9%, 215.0% and 224.4% for the healthy model, 157.4%, 177.8% and 171.8% for the fusion model (before bony fusion), 141.9%, 152.6% and 160.1% for the fusion model (after bony fusion). Although whole-body vibration is still more dangerous for the lumbar spine after interbody fusion surgery than static loading, the sensitivity of adjacent segment in postsurgical spine to vibration loading is decreased compared with healthy spine, especially when reaching to bony fusion. • Vibration load is more dangerous for the postsurgical lumbar spine than static load. • Interbody fusion decreased sensitivity of adjacent spinal segment to vibration load. • The vibration sensitivity is further decreased when reaching to bony fusion. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
36. The effect of non-fusion dynamic stabilization on biomechanical responses of the implanted lumbar spine during whole-body vibration.
- Author
-
Fan, Wei and Guo, Li-Xin
- Subjects
- *
WHOLE-body vibration , *LUMBAR vertebrae , *FINITE element method , *CYCLIC loads , *AXIAL loads , *ZYGAPOPHYSEAL joint - Abstract
• Dynamic fixation using the BioFlex system and anterior lumbar interbody fusion (ALIF) with rigid fixation were simulated using finite element method. • Stress and strain responses of the healthy, degenerated, BioFlex and ALIF models to vertical vibration loading were computed. • Biomechanical differences among these four finite elements models were compared. Non-fusion dynamic stabilization surgery is increasingly popular for treating degenerative lumbar disc disease. However, changes in spine biomechanics after application of posterior dynamic fixation devices during whole-body vibration (WBV) remain unclear. The study aimed to examine the effects of non-fusion dynamic stabilization on biomechanical responses of the implanted lumbar spine to vertical WBV. By modifying L4–L5 segment of the healthy human L1–sacrum finite element model, single-level disc degeneration, dynamic fixation using the BioFlex system and anterior lumbar interbody fusion (ALIF) with rigid fixation were simulated, respectively. Dynamic responses of stress and strain in the spinal levels for the healthy, degenerated, BioFlex and ALIF models under an axial cyclic loading were investigated and compared. The results showed that endplate stress at implant level was lower in the BioFlex model than in the degenerated and ALIF models, but stress of the connecting rod in the BioFlex system was greater than that in the rigid fixation system used in the ALIF. Compared with the healthy model, stress and strain responses in terms of disc bulge, annulus stress and nucleus pressure at adjacent levels were decreased in the degenerated, BioFlex and ALIF models, but no obvious difference was observed in these responses among the three models. This study may be helpful to understand variations in vibration characteristics of the lumbar spine after application of non-fusion dynamic stabilization system. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
37. Comparison of effects of four interbody fusion approaches on the fused and adjacent segments under vibration.
- Author
-
Guo, Li-Xin and Wang, Qing-Dong
- Subjects
- *
LUMBAR vertebrae surgery , *BONE screws , *FINITE element method , *RISK assessment , *SPINAL fusion , *STRUCTURAL models , *VIBRATION (Mechanics) , *STATISTICAL reliability , *PHYSIOLOGIC strain , *TREATMENT effectiveness ,SURGICAL complication risk factors - Abstract
Which lumbar fusion approaches having fewer impacts on the lumbar spine, reducing the risk of complications and the most conducive to bone fusion under whole-body vibration is urgent to know. This study researched the best approach under vibration by comparing the effects of four different approaches on the spine, especially regarding some significant indexes related to complications and outcomes. The L1-L5 finite element model was modified to simulate anterior, posterior, trans-foraminal and direct lateral lumbar interbody fusion approaches with bilateral pedicle screw fixation at L4-L5 level. Anterior lumbar interbody fusion decreased the corresponding vibration amplitude of the dynamic response at adjacent segments compared with the other three approaches. Direct lateral lumbar interbody fusion decreased the maximum stress in the cage, the endplates at the fused level, and the maximum compressive stress at the interface between the cage and endplates. The maximum disc height and segmental lordosis of Direct lateral lumbar interbody fusion model were the highest among these fusion approaches. Anterior lumbar interbody fusion may provide a more stable environment for the adjacent segments under vibration. Direct lateral lumbar interbody fusion may reduce the risk of subsidence, cage failure, and adjacent segment disease. Direct lateral lumbar interbody fusion may provide a more stable and suitable environment for vertebral cell growth and lead to better fusion outcomes. The findings may help us understand the effect of various fusion approaches on lumbar and provide some references for choosing a fusion approach. • Anteriorlumbar interbody fusion provides more stability for adjacent segments under vibration. • The risk of complications in direct lateral lumbar interbody fusion may be the lowest. • Direct lateral lumbar interbody fusion may generate more stable and suitable growth environment. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
38. A comparison of the influence of three different lumbar interbody fusion approaches on stress in the pedicle screw fixation system: Finite element static and vibration analyses.
- Author
-
Fan, Wei and Guo, Li‐Xin
- Subjects
- *
FINITE element method , *VIBRATION (Mechanics) , *PEDICLE flaps (Surgery) , *MECHANICAL loads , *LUMBAR puncture - Abstract
This study aimed to examine breakage risk of the bilateral pedicle screw (BPS) fixation system under static and vibration loadings after three different types of lumbar interbody fusion surgery. A previously validated intact L1‐sacrum finite element model was modified to simulate anterior, posterior, and transforaminal lumbar interbody fusion (ALIF, PLIF, and TLIF, respectively) with BPS fixation system (consisting of pedicle screws and rigid connecting rods) at L4‐L5. As a risk parameter for breakage, the von Mises stresses in the pedicle screws and the rods for the ALIF, PLIF, and TLIF models under static loading (flexion, extension, lateral bending, and axial torsion moments) and vibration loading (sinusoidal vertical load) were calculated and compared. The calculated von Mises stresses were different in the ALIF, PLIF, and TLIF models, but these stresses for all the fusion models were found to be concentrated in neck of the pedicle screw and middle of the rod under both the static and vibration loadings. The results from static analyses showed that the maximum stress in the BPS fixation system was greater in the TLIF model than in the ALIF and PLIF models under all the applied static loadings. The results from transient dynamic analyses also showed that the TLIF generated greater dynamic responses of the stress in the BPS fixation system to the vertical vibration compared with the ALIF and PLIF. It implies that the TLIF procedure might incur a higher risk of breakage for the BPS fixation system than the ALIF and PLIF procedures. Breakage risk of the bilateral pedicle screw (BPS) fixation system used in anterior, posterior, and transforaminal lumbar interbody fusion (ALIF, PLIF, and TLIF, respectively) procedures was investigated by calculating von Mises stresses in the pedicle screws and the rods using finite element analysis. The results indicated that the TLIF might incur a higher risk of breakage for the BPS fixation system than the ALIF and PLIF. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
39. The Role of Posterior Screw Fixation in Single-Level Transforaminal Lumbar Interbody Fusion During Whole Body Vibration: A Finite Element Study.
- Author
-
Fan, Wei and Guo, Li-Xin
- Subjects
- *
FRACTURE fixation , *CARTILAGE cells , *INTERVERTEBRAL disk , *FINITE element method , *BIOMEDICAL materials - Abstract
Objective Few studies have evaluated the need for supplementary instrumentation after lumbar interbody fusion under the condition of whole body vibration (WBV) that is typically present in vehicles. This study aimed to determine the effect of posterior pedicle screw fixation on dynamic response of the whole lumbar spine to vertical WBV after transforaminal lumbar interbody fusion (TLIF). Methods A previously validated nonlinear, osteoligamentous finite element (FE) model of the intact L1–sacrum human lumbar spine was modified to simulate single-level (L4-L5) TLIF without and with bilateral pedicle screw fixation (BPSF). Transit dynamic analysis was performed on the 2 developed models under a sinusoidal vertical vibration load of ±40 N and a compressive follower preload of 400 N. The resulting dynamic response results for the 2 models in terms of stresses and deformations were recorded and compared. Results When compared with no fixation, BPSF decreased dynamic responses of the spinal levels to the vertical vibration after TLIF. At the fused level (L4–L5), vibration amplitudes of the von-Mises stresses in L4 inferior endplate and L5 superior endplate decreased after BPSF by 48.0% and 46.4%, respectively. At other disc levels (L1-L2, L2-L3, L3-L4, and L5-S1), vibration amplitudes of the disc bulge, von-Mises stress in annulus ground substance and intradiscal pressure also produced 4.2%–9.0%, 2.3%–8.9%, and 3.4%–8.8% deceases, respectively, after BPSF. Conclusions After TLIF, application of BPSF can be helpful in the prevention of spine injury during vertical WBV. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
40. Dynamic Response of the Lumbar Spine to Whole-body Vibration Under a Compressive Follower Preload.
- Author
-
Li-Xin Guo, Wei Fan, Guo, Li-Xin, and Fan, Wei
- Subjects
- *
LUMBAR vertebrae , *WHOLE-body vibration , *DEAD loads (Mechanics) , *FINITE element method , *TIME-domain analysis , *VIBRATION therapy , *LUMBAR vertebrae physiology , *BIOLOGICAL models , *BIOMECHANICS , *EXPERIMENTAL design , *RESEARCH methodology , *QUANTITATIVE research , *RESEARCH methodology evaluation , *COMPRESSIVE strength , *EVALUATION - Abstract
Study Design: A finite element study of dynamic response of the lumbar spine to whole-body vibration.Objective: The aim of this study was to develop and validate a finite element model for exploring the impact of whole-body vibration on the entire lumbar spine with a compressive follower preload applied.Summary Of Background Data: Several finite element studies have investigated the biodynamic characteristics of the human lumbar spine when exposed to whole-body vibration. However, very limited studies have been performed to quantitatively describe dynamic response in time domain of the entire lumbar spine to vibration loading under a compressive follower preload.Methods: A three-dimensional nonlinear finite element model of the human lumbar spine (L1-sacrum) subjected to the compressive follower preload was created. Transient dynamic analysis was conducted on the model to compute the spinal response to a sinusoidal vertical vibration load of ±40 N under a 400 N preload. The obtained dynamic response results at all spinal levels were collected and plotted as a function of time. As a comparison, the corresponding results for vertical static loads (-40 and 40 N) under the preload (400 N) were also computed.Results: Plots of the dynamic response at all levels showed a cyclic response with time, and their vibration amplitudes (peak-to-bottom variations) were markedly higher than the corresponding changing amplitudes of static load cases. The increasing effect of the vibration load reached 314.5%, 263.2%, 242.4%, and 232.7%, respectively, in axial displacement of vertebral center, disc bulge, intradiscal pressure, and annulus stress (von-Mises stress). In addition, increasing the compressive follower preload led to an increase in the dynamic response and a decrease in their vibration amplitudes.Conclusion: This study may be useful to help quantify the effect of cyclic loading on the entire lumbar spine under physiologic compressive loading, and better understand vibration characteristics of the spine.Level Of Evidence: 5. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.