scholarly journals Effects of Revision Rod Position on Spinal Construct Stability in Lumbar Revision Surgery: A Finite Element Study

2022 ◽  
Vol 9 ◽  
Author(s):  
Quan-Chang Tan ◽  
Jin-Feng Huang ◽  
Hao Bai ◽  
Zi-Xuan Liu ◽  
Xin-Yi Huang ◽  
...  
Keyword(s):  
Finite Element ◽  
Revision Surgery ◽  
Spinal Instrumentation ◽  
Axial Rotation ◽  
Von Mises Stress ◽  
Fe Model ◽  
Interspinous Ligament ◽  
Moment Load ◽  
Von Mises ◽  
Changing Tendency

Revision surgery (RS) is a necessary surgical intervention in clinical practice to treat spinal instrumentation–related symptomatic complications. Three constructs with different configurations have been applied in RS. One distinguishing characteristic of these configurations is that the revision rods connecting previous segments and revision segments are placed alongside, outside, or inside the previous rods at the level of facetectomy. Whether the position of the revision rod could generate mechanical disparities in revision constructs is unknown. The objective of this study was to assess the influence of the revision rod position on the construct after RS. A validated spinal finite element (FE) model was developed to simulate RS after previous instrumented fusion using a modified dual-rod construct (DRCm), satellite-rod construct (SRC), and cortical bone trajectory construct (CBTC). Thereafter, maximum von Mises stress (VMS) on the annulus fibrosus and cages and the ligament force of the interspinous ligament, supraspinous ligament, and ligamentum flavum under a pure moment load and a follower load in six directions were applied to assess the influence of the revision rod position on the revision construct. An approximately identical overall reducing tendency of VMS was observed among the three constructs. The changing tendency of the maximum VMS on the cages placed at L4-L5 was nearly equal among the three constructs. However, the changing tendency of the maximum VMS on the cage placed at L2-L3 was notable, especially in the CBTC under right bending and left axial rotation. The overall changing tendency of the ligament force in the DRCm, SRC, and CBTC was also approximately equal, while the ligament force of the CBTC was found to be significantly greater than that of the DRCm and SRC at L1-L2. The results indicated that the stiffness associated with the CBTC might be lower than that associated with the DRCm and SRC in RS. The results of the present study indicated that the DRCm, SRC, and CBTC could provide sufficient stabilization in RS. The CBTC was a less rigid construct. Rather than the revision rod position, the method of constructing spinal instrumentation played a role in influencing the biomechanics of revision.

Design and development of a novel expanding flexible rod device (FRD) for stability in the lumbar spine: A finite-element study

2020 ◽  
Vol 43 (12) ◽  
pp. 803-810 ◽  
Author(s):  
Masud Rana ◽  
Sandipan Roy ◽  
Palash Biswas ◽  
Shishir Kumar Biswas ◽  
Jayanta Kumar Biswas
Keyword(s):  
Finite Element ◽  
Lumbar Spine ◽  
Range Of Motion ◽  
Pedicle Screw ◽  
Axial Rotation ◽  
Von Mises Stress ◽  
Lateral Bending ◽  
Intact Bone ◽  
Flexion Extension ◽  
Von Mises

The aim of this study is to design a novel expanding flexible rod device, for pedicle screw fixation to provide dynamic stability, based on strength and flexibility. Three-dimensional finite-element models of lumbar spine (L1-S) with flexible rod device on L3-L4-L5 levels are developed. The implant material is taken to be Ti-6Al-4V. The models are simulated under different boundary conditions, and the results are compared with intact model. In natural model, total range of motion under 10 Nm moment were found 66.7°, 24.3° and 13.59°, respectively during flexion–extension, lateral bending and axial rotation. The von Mises stress at intact bone was 4 ± 2 MPa and at bone, adjacent to the screw in the implanted bone, was 6 ± 3 MPa. The von Mises stress of disc of intact bone varied from 0.36 to 2.13 MPa while that of the disc between the fixed vertebra of the fixation model reduced by approximately 10% for flexion and 25% for extension compared to intact model. The von Mises stresses of pedicle screw were 120, 135, 110 and 90 MPa during flexion, extension, lateral bending, and axial rotation, respectively. All the stress values were within the safe limit of the material. Using the flexible rod device, flexibility was significantly increased in flexion/extension but not in axial rotation and lateral bending. The results suggest that dynamic stabilization system with respect to fusion is more effective for homogenizing the range of motion of the spine.

scholarly journals A Novel Rat Model of Orthodontic Tooth Movement Using Temporary Skeletal Anchorage Devices: 3D Finite Element Analysis andIn VivoValidation

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Neelambar Kaipatur ◽  
Yuchin Wu ◽  
Samer Adeeb ◽  
Thomas Stevenson ◽  
Paul Major ◽  
...  
Keyword(s):  
Finite Element ◽  
Alveolar Bone ◽  
Tooth Movement ◽  
Orthodontic Tooth Movement ◽  
Von Mises Stress ◽  
Fe Model ◽  
Sprague Dawley ◽  
Element Analysis ◽  
Von Mises ◽  
The Right

The aim of this animal study was to develop a model of orthodontic tooth movement using a microimplant as a TSAD in rodents. A finite element model of the TSAD in alveolar bone was built usingμCT images of rat maxilla to determine the von Mises stresses and displacement in the alveolar bone surrounding the TSAD. Forin vivovalidation of the FE model, Sprague-Dawley rats (n=25) were used and a Stryker 1.2 × 3 mm microimplant was inserted in the right maxilla and used to protract the right first permanent molar using a NiTi closed coil spring. Tooth movement measurements were taken at baseline, 4 and 8 weeks. At 8 weeks, animals were euthanized and tissues were analyzed by histology and EPMA. FE modeling showed maximum von Mises stress of 45 Mpa near the apex of TSAD but the average von Mises stress was under 25 Mpa. Appreciable tooth movement of 0.62 ± 0.04 mm at 4 weeks and 1.99 ± 0.14 mm at 8 weeks was obtained. Histological and EPMA results demonstrated no active bone remodeling around the TSAD at 8 weeks depicting good secondary stability. This study provided evidence that protracted tooth movement is achieved in small animals using TSADs.

scholarly journals Identification of Surgical Plan for Syndesmotic Fixation Procedure Based on Finite Element Method

2020 ◽  
Vol 10 (12) ◽  
pp. 4349 ◽  
Author(s):  
Tae Sik Goh ◽  
Beop-Yong Lim ◽  
Jung Sub Lee ◽  
Chi-Seung Lee
Keyword(s):  
Finite Element ◽  
Simulation Method ◽  
Fe Analysis ◽  
Von Mises Stress ◽  
Fe Model ◽  
Syndesmotic Screw ◽  
Surgical Options ◽  
Biomechanical Parameters ◽  
Von Mises ◽  
Two Parameters

Syndesmosis injuries account for approximately 20% of ankle fractures that require surgery. Although multiple surgical options are available, all of them are based on metal screws. Serious complications that arise when applying metal screws include screw loosening or breakage. To prevent such complications, we applied a simulation method using a finite element (FE) analysis. We created a 3D FE model of an ankle joint and conducted an FE analysis focusing on syndesmosis in terms of the level, material, and diameter of the syndesmotic screw and the number of penetrated cortical bones. The magnitude and direction of the force applied to the tibia in the midstance state were considered for simulating the model. The maximum von-Mises stress and syndesmosis widening were analyzed in terms of different biomechanical parameters. We identified the characteristics of the most biomechanically stable syndesmotic screw and its fixation point on the basis of the two parameters. We demonstrated that the ideal syndesmotic screw fixation should be fixed at a level 20 to 25 mm above the ankle using a 4.5 mm titanium screw.

scholarly journals Multi-layered bird beaks: a finite-element approach towards the role of keratin in stress dissipation

2012 ◽  
Vol 9 (73) ◽  
pp. 1787-1796 ◽  
Author(s):  
Joris Soons ◽  
Anthony Herrel ◽  
Annelies Genbrugge ◽  
Dominique Adriaens ◽  
Peter Aerts ◽  
...  
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Speckle Pattern ◽  
Young Modulus ◽  
Von Mises Stress ◽  
Fe Model ◽  
Element Approach ◽  
Von Mises ◽  
The Impact

Bird beaks are layered structures, which contain a bony core and an outer keratin layer. The elastic moduli of this bone and keratin were obtained in a previous study. However, the mechanical role and interaction of both materials in stress dissipation during seed crushing remain unknown. In this paper, a multi-layered finite-element (FE) model of the Java finch's upper beak ( Padda oryzivora ) is established. Validation measurements are conducted using in vivo bite forces and by comparing the displacements with those obtained by digital speckle pattern interferometry. Next, the Young modulus of bone and keratin in this FE model was optimized in order to obtain the smallest peak von Mises stress in the upper beak. To do so, we created a surrogate model, which also allows us to study the impact of changing material properties of both tissues on the peak stresses. The theoretically best values for both moduli in the Java finch are retrieved and correspond well with previous experimentally obtained values, suggesting that material properties are tuned to the mechanical demands imposed during seed crushing.

Comparison of Fatigue Behaviors of Spinal Implants Under Physiological Spinal Loads: A Finite Element Pilot Study

2017 ◽  
Author(s):  
Ming Xu ◽  
James Yang ◽  
Isador H. Lieberman ◽  
Ram Haddas
Keyword(s):  
Pedicle Screw ◽  
Axial Rotation ◽  
Von Mises Stress ◽  
Fe Model ◽  
Fusion Surgery ◽  
Spinal Loads ◽  
Spinal Implants ◽  
Exact Geometry ◽  
Von Mises ◽  
Biomechanical Tests

The fusion surgery is a standard treatment for scoliosis. Fatigue-related failure is one common cause for the fusion surgery implant. Due to the high cost of revision surgery, it is of clinical value to study the fatigue behaviors of the spinal implants under physiological spinal loads. In the literature, biomechanical tests and finite element (FE) methods have been used to study the fatigue of the spinal implants. Compared with biomechanical tests, FE analysis has the advantage of low cost and high efficiency. Due to the high computational cost, no FE study has been modeled the exact geometry of the pedicle screw (including the thread) in the screw-bone connection within the multi-level spine FE model. This study introduced a feasible FE-based method to predict the fatigue behaviors of the spinal implants with exact geometry of pedicle screw. One previously-validated FE spine model was utilized to provide physiological spinal loads and was bilaterally fused with pedicle screws and rods at L3-L4 spine levels. The exact geometry of the pedicle screw was simulated in this study for accurate stress prediction. The fused spine FE model was subjected to six loading directions (flexion/extension, left/right lateral bending, and left/right axial rotation). For each loading direction, a pure bending moment of 10 Nm was tested. First, FE analysis was performed for one loading cycle. Range of motion, maximum von Mises stress values of the spinal implants were recorded and compared for the six tested loading conditions. Then, based on the stress/strain history of the spinal implants for one loading cycle provided by the FE simulation, fatigue life cycles of the spinal implants were calculated using strain-based Smith-Watson-Topper equation. Flexion produced the largest range of motion at the adjacent level. Axial rotation produced the largest von Mises stress in the spinal implants. Except for lateral bending, the von Mises stress predicted in the screws fused at the superior vertebra was larger than that in the screws fused at inferior vertebra. The method introduced in this study will be used to study different screw fixation methods in the future work.

scholarly journals Development of a Finite Element Head Model for the Study of Impact Head Injury

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Bin Yang ◽  
Kwong-Ming Tse ◽  
Ning Chen ◽  
Long-Bin Tan ◽  
Qing-Qian Zheng ◽  
...  
Keyword(s):  
Finite Element ◽  
Brain Injuries ◽  
Current Knowledge ◽  
Human Head ◽  
Von Mises Stress ◽  
Head Model ◽  
Fe Model ◽  
Prediction And Prevention ◽  
Von Mises ◽  
The Brain

This study is aimed at developing a high quality, validated finite element (FE) human head model for traumatic brain injuries (TBI) prediction and prevention during vehicle collisions. The geometry of the FE model was based on computed tomography (CT) and magnetic resonance imaging (MRI) scans of a volunteer close to the anthropometry of a 50th percentile male. The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The cerebrospinal fluid (CSF) was simulated explicitly as a hydrostatic fluid by using a surface-based fluid modeling method. The model was validated in the loading condition observed in frontal impact vehicle collision. These validations include the intracranial pressure (ICP), brain motion, impact force and intracranial acceleration response, maximum von Mises stress in the brain, and maximum principal stress in the skull. Overall results obtained in the validation indicated improved biofidelity relative to previous FE models, and the change in the maximum von Mises in the brain is mainly caused by the improvement of the CSF simulation. The model may be used for improving the current injury criteria of the brain and anthropometric test devices.

scholarly journals Biomechanical feasibility of semi-rigid stabilization and semi-rigid lumbar interbody fusion: a finite element study

2022 ◽  
Vol 23 (1) ◽  
Author(s):  
Chia-En Wong ◽  
Hsuan-Teh Hu ◽  
Li-Hsing Kao ◽  
Che-Jung Liu ◽  
Ke-Chuan Chen ◽  
...  
Keyword(s):  
Finite Element ◽  
Strain Energy ◽  
Lumbar Fusion ◽  
Axial Rotation ◽  
Von Mises Stress ◽  
Peek Cage ◽  
Lateral Bending ◽  
Interspinous Spacer ◽  
Flexion Extension ◽  
Von Mises

Abstract Background Semi-rigid lumbar fusion offers a compromise between pedicle screw-based rigid fixation and non-instrumented lumbar fusion. However, the use of semi-rigid interspinous stabilization (SIS) with interspinous spacer and ligamentoplasty and semi-rigid posterior instrumentation (SPI) to assist interbody cage as fusion constructs remained controversial. The purpose of this study is to investigate the biomechanical properties of semi-rigidly stabilized lumbar fusion using SIS or SPI and their effect on adjacent levels using finite element (FE) method. Method Eight FE models were constructed to simulate the lumbosacral spine. In the non-fusion constructs, semi-rigid stabilization with (i) semi-rigid interspinous spacer and artificial ligaments (PD-SIS), and (ii) PI with semi-rigid rods were simulated (PD + SPI). For fusion constructs, the spinal models were implanted with (iii) PEEK cage only (Cage), (iv) PEEK cage and SIS (Cage+SIS), (v) PEEK cage and SPI (Cage+SPI), (vi) PEEK cage and rigid PI (Cage+PI). Result The comparison of flexion-extension range of motion (ROM) in the operated level showed the difference between Cage+SIS, Cage+SPI, and Cage+PI was less than 0.05 degree. In axial rotation, ROM of Cage+SIS were greater than Cage+PI by 0.81 degree. In the infrajacent level, while Cage+PI increased the ROM by 24.1, 27,7, 25.9, and 10.3% and Cage+SPI increased the ROM by 26.1, 30.0, 27.1, and 10.8% in flexion, extension, lateral bending and axial rotation respectively, Cage+SIS only increased the ROM by 3.6, 2.8, and 11.2% in flexion, extension, and lateral bending and reduced the ROM by 1.5% in axial rotation. The comparison of the von Mises stress showed that SIS reduced the adjacent IVD stress by 9.0%. The simulation of the strain energy showed a difference between constructs less than 7.9%, but all constructs increased the strain energy in the infradjacent level. Conclusion FE simulation showed semi-rigid fusion constructs including Cage+SIS and Cage+SPI can provide sufficient stabilization and flexion-extension ROM reduction at the fusion level. In addition, SIS-assisted fusion resulted in less hypermobility and less von Mises stress in the adjacent levels. However, SIS-assisted fusion had a disadvantage of less ROM reduction in lateral bending and axial rotation. Further clinical studies are warranted to investigate the clinical efficacy and safety of semi-rigid fusions.

scholarly journals A Hybrid Uniplanar Pedicle Screw System with a New Intermediate Screw for Minimally Invasive Spinal Fixation: A Finite Element Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Jia Li ◽  
Li-Cheng Zhang ◽  
Jiantao Li ◽  
Hao Zhang ◽  
Jing-Xin Zhao ◽  
...  
Keyword(s):  
Finite Element ◽  
Minimally Invasive ◽  
Range Of Motion ◽  
Pedicle Screw ◽  
Axial Rotation ◽  
Von Mises Stress ◽  
Spinal Fixation ◽  
Lateral Bending ◽  
Maximum Displacement ◽  
Von Mises

Purpose. A hybrid pedicle screw system for minimally invasive spinal fixation was developed based on the uniplanar pedicle screw construct and a new intermediate screw. Its biomechanical performance was evaluated using finite element (FE) analysis. Methods. A T12-L2 FE model was established to simulate the L1 vertebral compression fracture with Magerl classification A1.2. Six fixation models were developed to simulate the posterior pedicle screw fracture fixation, which were divided into two subgroups with different construct configurations: (1) six-monoaxial/uniplanar/polyaxial pedicle screw constructs and (2) four-monoaxial/uniplanar/polyaxial pedicle screw constructs with the new intermediate screw. After model validation, flexion, extension, lateral bending, and axial rotation with 7.5 Nm moments and preloading of 500 N vertical compression were applied to the FE models to compare the biomechanical performances of the six fixation models with maximum von Mises stress, range of motion, and maximum displacement of the vertebra. Results. Under four loading scenarios, the maximum von Mises stresses were found to be at the roots of the upper or lower pedicle screws. In the cases of flexion, lateral bending, and axial rotation, the maximum von Mises stress of the uniplanar screw construct lay in between the monoaxial and polyaxial screw constructs in each subgroup. Considering lateral bending, the uniplanar screw construct enabled to lower the maximum von Mises stress than monoaxial and polyaxial pedicle screw constructs in each subgroup. Two subgroups showed comparable results of the maximum von Mises stress on the endplates, range of motion of T12-L1, and maximum displacement of T12 between the corresponding constructs with the new intermediate screw or not. Conclusions. The observations shown in this study verified that the hybrid uniplanar pedicle screw system exhibited comparable biomechanical performance as compared with other posterior short-segment constructs. The potential advantage of this new fixation system may provide researchers and clinical practitioners an alternative for minimally invasive spinal fixation with vertebral augmentation.

scholarly journals Different fixation pattern for thoracolumbar fracture of ankylosing spondylitis: A finite element analysis

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250009
Author(s):  
Tianyu Zhang ◽  
Yanhua Wang ◽  
Peixun Zhang ◽  
Feng Xue ◽  
Dianying Zhang ◽  
...  
Keyword(s):  
Finite Element ◽  
Ankylosing Spondylitis ◽  
Internal Fixation ◽  
Thoracolumbar Fracture ◽  
Von Mises Stress ◽  
Fe Model ◽  
Pull Force ◽  
Kyphosis Correction ◽  
Four Levels ◽  
Von Mises

The objective of this study is to establish an ankylosing spondylitis (AS) thoracolumbar fracture finite element (FE) model and provide a proper posterior fixation choice from the biomechanical perspective. The ankylosing spondylitis T9-L5 FE model was built and the range of motion (ROM) was compared to previous studies. The L1 transverse fracture was simulated and was separately fixed by five different patterns. The pull force and yielding force of the screws, the von Mises stress of the internal fixation, and the displacement of fracture site were analyzed to evaluate the proper fixation pattern for thoracolumbar fracture of AS. ROM of AS model was obviously restricted comparing to the normal vertebral experimental data. All the fixation patterns can stabilize the fracture. At least four levels of fixation can reduce the von Mises stress of the internal fixation. Four levels fixation has a higher pull force than the six levels fixation. Skipped level fixation did not reduce the stress, pull force and yielding force. The kyphosis correction did not change the biomechanical load. At least 4 levels fixation was needed for AS thoracolumbar fracture. The cemented screws should be chosen in 4 levels fixation to increase the holding of the screws. The skipped fixation has no advantage. The kyphosis correction can be chosen after weighing the pros and cons.

Rod Stress Prediction in Spinal Alignment Surgery With Different Supplementary Rod Constructing Techniques: A Finite Element Study

2018 ◽  
Author(s):  
Ming Xu ◽  
Thomas Scholl ◽  
Pedro Berjano ◽  
Jazmin Cruz ◽  
James Yang
Keyword(s):  
Finite Element ◽  
Contact Region ◽  
Element Model ◽  
Axial Rotation ◽  
Von Mises Stress ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Single Cross ◽  
Von Mises ◽  
Double Cross

Rod fracture and nonunion are common complications associated with pedicle subtraction osteotomies (PSO). Supplementary rods and interbody cage (IB) are added to reduce the primary rod stress. As supplementary rods, delta rods and cross rods have been proposed to reduce more stress on the primary rods compared to conventional supplementary rods (accessary rods) in PSO. The objective of this study is to investigate the effects of cross rods and delta rods on reducing primary rod stress in PSO subject. A validated 3D finite element model of a T12-S1 spine segment with 25° PSO at L3 and bilateral rods fixation from T12-S1 was used to compare different rod configurations: 1) PSO and two primary rods (PSO+2P); 2) PSO with an IB at L2-L3 (PSO+2P+IB); 3) PSO with accessory rods and an IB at L2-L3 (PSO+2P+IB+2A); 4) PSO with delta rods and an IB at L2-L3 (PSO+2P+IB+2D); 5) PSO with single cross rod and an IB at L2-L3 (PSO+2P+IB+1C); 6) PSO with double cross rods and an IB at L2-L3 (PSO+2P+IB+2C). The spine model was loaded with a follower load of 400 N combined with pure moments of 7.5 Nm in flexion, extension, right lateral bending, and right axial rotation. Von Mises stress of the primary rods were predicted for all test conditions. The PSO without IB condition had the largest primary rod stress in flexion. With IB at L2-L3, the rod stress in flexion reduced by 15%. Adding 2 conventional supplementary rods reduced the rod stress in flexion by 29%, which was achieved by adding single cross rod. The maximum von Mises stress occurred in the middle of the primary rods without supplementary rods whereas the maximum stress concentrated adjacent to the contact region between the connectors and the primary rods. Delta rods and double cross rods reduced the most rod stress in flexion, which were by 33% and 32% respectively. Under lateral bending, 2 delta rods reduced the most primary rod stress (−33%). Under axial rotation, the single cross rod reduced the most primary rod stress (−48%). Interbody cages and supplementary rods reduced the primary rod stress in a comparable way. Primary rod stress with 2 delta rods and double cross rods were comparable, which were marginally lower than those with conventional supplementary rods. Adding single cross rod was comparable to adding 2 conventional accessory rods in rod stress reduction in flexion. Under lateral bending, delta rods reduced most rod stress whereas under axial rotation, cross rods reduced most rod stress. This study suggested that both delta rods and cross rods reduce more primary rod stress than conventional accessory rods do.

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