Creating Physiologically Realistic Vertebral Fractures in a Cervine Model

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Nicole C. Corbiere ◽  
Kathleen A. Lewicki ◽  
Kathleen A. Issen ◽  
Laurel Kuxhaus
Keyword(s):  
Cancellous Bone ◽  
Mechanical Response ◽  
Bone Structure ◽  
Peak Load ◽  
Compressive Load ◽  
Compression Fracture ◽  
Loading Conditions ◽  
Cross Sectional ◽  
Motion Segment ◽  
Cadaver Specimen

Approximately 50% of women and 25% of men will have an osteoporosis-related fracture after the age of 50, yet the micromechanical origin of these fractures remains unclear. Preventing these fractures requires an understanding of compression fracture formation in vertebral cancellous bone. The immediate research goal was to create clinically relevant (midvertebral body and endplate) fractures in three-vertebrae motion segments subject to physiologically realistic compressional loading conditions. Six three-vertebrae motion segments (five cervine, one cadaver) were potted to ensure physiologic alignment with the compressive load. A 3D microcomputed tomography (microCT) image of each motion segment was generated. The motion segments were then preconditioned and monotonically compressed until failure, as identified by a notable load drop (48–66% of peak load in this study). A second microCT image was then generated. These three-dimensional images of the cancellous bone structure were inspected after loading to qualitatively identify fracture location and type. The microCT images show that the trabeculae in the cervine specimens are oriented similarly to those in the cadaver specimen. In the cervine specimens, the peak load prior to failure is highest for the L4–L6 motion segment, and decreases for each cranially adjacent motion segment. Three motion segments formed endplate fractures and three formed midvertebral body fractures; these two fracture types correspond to clinically observed fracture modes. Examination of normalized-load versus normalized-displacement curves suggests that the size (e.g., cross-sectional area) of a vertebra is not the only factor in the mechanical response in healthy vertebral specimens. Furthermore, these normalized-load versus normalized-displacement data appear to be grouped by the fracture type. Taken together, these results show that (1) the loading protocol creates fractures that appear physiologically realistic in vertebrae, (2) cervine vertebrae fracture similarly to the cadaver specimen under these loading conditions, and (3) that the prefracture load response may predict the impending fracture mode under the loading conditions used in this study.

The Effect of Creep on Human Lumbar Intervertebral Disk Impact Mechanics

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
David Jamison ◽  
Michele S. Marcolongo
Keyword(s):  
Mechanical Response ◽  
Compressive Load ◽  
Fluid Phase ◽  
Constant Load ◽  
Time Of Day ◽  
Intervertebral Disk ◽  
Fluid Loss ◽  
Loading Conditions ◽  
Impact Mechanics ◽  
Continuous Displacement

The intervertebral disk (IVD) is a highly hydrated tissue, with interstitial fluid making up 80% of the wet weight of the nucleus pulposus (NP), and 70% of the annulus fibrosus (AF). It has often been modeled as a biphasic material, consisting of both a solid and fluid phase. The inherent porosity and osmotic potential of the disk causes an efflux of fluid while under constant load, which leads to a continuous displacement phenomenon known as creep. IVD compressive stiffness increases and NP pressure decreases as a result of creep displacement. Though the effects of creep on disk mechanics have been studied extensively, it has been limited to nonimpact loading conditions. The goal of this study is to better understand the influence of creep and fluid loss on IVD impact mechanics. Twenty-four human lumbar disk samples were divided into six groups according to the length of time they underwent creep (tcreep = 0, 3, 6, 9, 12, 15 h) under a constant compressive load of 400 N. At the end of tcreep, each disk was subjected to a sequence of impact loads of varying durations (timp = 80, 160, 320, 400, 600, 800, 1000 ms). Energy dissipation (ΔE), stiffness in the toe (ktoe) and linear (klin) regions, and neutral zone (NZ) were measured. Analyzing correlations with tcreep, there was a positive correlation with ΔE and NZ, along with a negative correlation with ktoe. There was no strong correlation between tcreep and klin. The data suggest that the IVD mechanical response to impact loading conditions is altered by fluid content and may result in a disk that exhibits less clinical stability and transfers more load to the AF. This could have implications for risk of diskogenic pain as a function of time of day or tissue hydration.

ANALYSIS OF DURAL-SAC OCCLUSION IN A LUMBAR SPINAL MOTION SEGMENT FE MODEL

2001 ◽  
Vol 05 (04) ◽  
pp. 243-252 ◽  
Author(s):  
YOUNG EUN KIM ◽  
SUNG YOON CHO ◽  
HYUNG YUN CHOI
Keyword(s):  
Lumbar Spine ◽  
Compressive Load ◽  
Elastic Behavior ◽  
Fe Model ◽  
Cross Sectional ◽  
Dural Sac ◽  
Motion Segment ◽  
Flexion Moment ◽  
Spine Model ◽  
Lumbar Spinal

Occlusion of dural-sac in the lumbar spine was quantitatively analyzed by utilizing one motion segment of finite element lumbar spine model developed in this study. And the mechanism of occlusion, considering both static and viscous behavior of materials, was also investigated with various loading conditions. Occlusion was quantified by calculating the cross sectional area change or volumetric changes of dural-sac. In the static analysis, it was found that less than 2 kN of compressive load could not produce dural-sac occlusion but the compression together with extension moment was more likely to produce the dural-sac occlusion. The 7.4% of occlusion was obtained when the 8 Nm of extension moment was added to 2 kN of compressive load which alone did not create any occlusion. The magnitude of occlusions was increased to 10.5% as the extension moment become to 10 Nm with the same 2 kN of compressive load. In creep analysis, 10 Nm extension, kept for 3600 seconds, induced 6.9% of occlusion and 2.4% of volume reduction in dural-sac. However, flexion moment did not produce any occlusion in dural-sac but increased the volume instead because it caused stretching of dural-sac coupled with vertebra motion. As a conclusion, occlusions resulted mainly from the slackening of ligamentum flavum and disc bulging, and the amount of occlusion was strongly dependent with loading condition and visco-elastic behavior of materials as well.

Load Sharing Among Spinal Elements of a Motion Segment in Extension and Lateral Bending

1987 ◽  
Vol 109 (4) ◽  
pp. 291-297 ◽  
Author(s):  
V. K. Goel ◽  
J. M. Winterbottom ◽  
J. N. Weinstein ◽  
Y. E. Kim
Keyword(s):  
Ligamentum Flavum ◽  
Linear Optimization ◽  
Compressive Load ◽  
Tensile Load ◽  
Loading Conditions ◽  
Lateral Bending ◽  
Capsular Ligament ◽  
Motion Segment ◽  
Axial Tensile ◽  
The Right

A linear optimization model was formulated using a semi-experimental protocol to estimate the forces in the spinal elements of a lumbar motion segment subjected to an extension or lateral bending moment with and without a 120 N compressive preload. A morphometer was used to acquire the three-dimensional locations of the disk center, facet centers and ligament origin and insertion sites with the specimen in a “neutral” position. The relative motion of the superior vertebra, under the loading conditions tested, was monitored using a Selspot II® system. These data allowed the formulation of the static equilibrium equations for the superior vertebra at each of the loading conditions mentioned above. A linear optimization technique was used, along with a suitable cost function, to find an optimum solution for the set of equations and imposed constraints. Results showed that for 6.9 Nm of extension moment, each facet carried a load of 52 N, with the disk carrying an axial tensile load of 104 N. At the 6.9 Nm extension moment coupled with 120 N preload, each facet carried a load of 77.2 N and the disk an axial tensile load of 37 N. In right lateral bending, with and without preload, the load was distributed among the right facet, the disk, the left ligamentum flavum and the left capsular ligament. At the 6.9 Nm load step without preload the right facet carried an axial load of 127.01 N with the disk carrying an axial compressive load of 7.8 N. Ligament forces for this step for the left ligamentum flavum and capsular ligament, respectively, were 61.03 N and 65.14 N. The addition of 120 N of preload reduced the load on the right facet to 83.5 N. The compressive load in the disk increased to 107.5 N. The corresponding ligament forces were 43.2 N (left ligamentum flavum) and 50.7 N (left capsular ligament).

scholarly journals Numerical and Theoretical Study of Performance and Mechanical Behavior of PEM-FC Using Innovative Channel Geometrical Configurations

2021 ◽  
Vol 11 (12) ◽  
pp. 5597
Author(s):  
Hussein A. Z. AL-bonsrulah ◽  
Mohammed J. Alshukri ◽  
Ammar I. Alsabery ◽  
Ishak Hashim
Keyword(s):  
Fuel Cell ◽  
Cross Section ◽  
Rectangular Channel ◽  
Compressive Load ◽  
Proton Exchange ◽  
Channel Cross Section ◽  
Channel Height ◽  
Cross Sectional ◽  
Triangular Channel ◽  
Higher Power

Proton exchange membrane fuel cell (PEM-FC) aggregation pressure causes extensive strains in cell segments. The compression of each segment takes place through the cell modeling method. In addition, a very heterogeneous compressive load is produced because of the recurrent channel rib design of the dipole plates, so that while high strains are provided below the rib, the domain continues in its initial uncompressed case under the ducts approximate to it. This leads to significant spatial variations in thermal and electrical connections and contact resistances (both in rib–GDL and membrane–GDL interfaces). Variations in heat, charge, and mass transfer rates within the GDL can affect the performance of the fuel cell (FC) and its lifetime. In this paper, two scenarios are considered to verify the performance and lifetime of the PEM-FC using different innovative channel geometries. The first scenario is conducted by adopting a constant channel height (H = 1 mm) for all the differently shaped channels studied. In contrast, the second scenario is conducted by taking a constant channel cross-sectional area (A = 1 mm2) for all the studied channels. Therefore, a computational fluid dynamics model (CFD) for a PEM fuel cell is formed through the assembly of FC to simulate the pressure variations inside it. The simulation results showed that a triangular cross-section channel provided the uniformity of the pressure distribution, with lower deformations and lower mechanical stresses. The analysis helped gain insights into the physical mechanisms that lead to the FC’s durability and identify important parameters under different conditions. The model shows that it can assume the intracellular pressure configuration toward durability and appearance containing limited experimental data. The results also proved that the better cell voltage occurs in the case of the rectangular channel cross-section, and therefore, higher power from the FC, although its durability is much lower compared to the durability of the triangular channel. The results also showed that the rectangular channel cross-section gave higher cell voltages, and therefore, higher power (0.63 W) from the fuel cell, although its durability is much lower compared to the durability of the triangular channel. Therefore, the triangular channel gives better performance compared to other innovative channels.

scholarly journals Discrete element analysis of the punching behaviour of a secured drapery system: from laboratory characterization to idealized in situ conditions

2021 ◽  
Author(s):  
Antonio Pol ◽  
Fabio Gabrieli ◽  
Lorenzo Brezzi
Keyword(s):  
Mechanical Response ◽  
Steel Wire ◽  
Discrete Element ◽  
Wire Mesh ◽  
Steel Plates ◽  
Loading Conditions ◽  
Element Analysis ◽  
In Situ Conditions ◽  
Wire Meshes

AbstractIn this work, the mechanical response of a steel wire mesh panel against a punching load is studied starting from laboratory test conditions and extending the results to field applications. Wire meshes anchored with bolts and steel plates are extensively used in rockfall protection and slope stabilization. Their performances are evaluated through laboratory tests, but the mechanical constraints, the geometry and the loading conditions may strongly differ from the in situ conditions leading to incorrect estimations of the strength of the mesh. In this work, the discrete element method is used to simulate a wire mesh. After validation of the numerical mesh model against experimental data, the punching behaviour of an anchored mesh panel is investigated in order to obtain a more realistic characterization of the mesh mechanical response in field conditions. The dimension of the punching element, its position, the anchor plate size and the anchor spacing are varied, providing analytical relationships able to predict the panel response in different loading conditions. Furthermore, the mesh panel aspect ratio is analysed showing the existence of an optimal value. The results of this study can provide useful information to practitioners for designing secured drapery systems, as well as for the assessment of their safety conditions.

Temporal changes in cancellous bone structure of rats immediately after ovariectomy

Bone ◽  
1995 ◽  
Vol 16 (1) ◽  
pp. 157-161 ◽  
Author(s):  
D.W. Dempster ◽  
R. Birchman ◽  
R. Xu ◽  
R. Lindsay ◽  
V. Shen
Keyword(s):  
Cancellous Bone ◽  
Bone Structure ◽  
Temporal Changes ◽  
Cancellous Bone Structure

Shear strength properties of plain and spirally profiled cable bolts

2015 ◽  
Vol 52 (10) ◽  
pp. 1490-1495 ◽  
Author(s):  
Naj Aziz ◽  
Ali Mirzaghorbanali ◽  
Jan Nemcik ◽  
Kay Heemann ◽  
Stefan Mayer
Keyword(s):  
Shear Strength ◽  
Testing Machine ◽  
Peak Load ◽  
Strength Properties ◽  
Shear Displacement ◽  
Vertical Shear ◽  
Cross Sectional ◽  
Cable Bolts ◽  
Strength Capacity ◽  
Cable Bolt

An experimental investigation into the performance of two 22 mm diameter, 60 t tensile strength capacity Hilti cable bolts in shear was conducted using the double-shear testing apparatus at the laboratory of the School of Civil, Mining and Environmental Engineering, Faculty of Engineering and Information Sciences, University of Wollongong. The tested cable bolts were (i) Hilti 19 wire HTT-UXG plain strand and (ii) Hilti 19 wire HTT-IXG spirally profiled (smaller cross-sectional area than the plain one) cable bolt, with indentation only on the surface of the outer strands. These cable bolts are of sealed wire construction type, consisting of an outer 5.5 mm diameter wire layer overlying the middle 3 mm diameter wire strands. Both layers are wrapped around a single solid 7 mm diameter strand wire core. The double-shearing test was carried out in 40 MPa concrete blocks, contained in concrete moulds. Cable bolts were encapsulated in concrete using Orica FB400 pumpable grout. Prior to encapsulation, each cable bolt was pre-tensioned initially to 50 kN axial force. A 500 t capacity servocontrolled compression testing machine was used for both tests, and during each test the vertical shear displacement was limited to 70 mm of travel. The rate of vertical shear displacement was maintained constant at 1 mm/min. The maximum shear load achieved for the plain strand cable was 1024 kN, while the spiral cable peak load was 904 kN, before the cable bolt wires began to individually snap, leading to the cable bolt break-up into two sections. It is apparent that spiral profiles of the outer wires weaken both the tensile and shearing strength. Finally, another set of tests was undertaken using the British Standard single-shear approach, producing lower shear strength values.

scholarly journals Simulation of cortico-cancellous bone structure by 3D printing of bilayer calcium phosphate-based scaffolds

Bioprinting ◽  
2017 ◽  
Vol 6 ◽  
pp. 1-7 ◽  
Author(s):  
Thafar Almela ◽  
Ian M. Brook ◽  
Kimia Khoshroo ◽  
Morteza Rasoulianboroujeni ◽  
Farahnaz Fahimipour ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
3D Printing ◽  
Cancellous Bone ◽  
Bone Structure ◽  
Cancellous Bone Structure

scholarly journals The problem of mismatches between CT scan and DXA results

2019 ◽  
pp. 12-17
Author(s):  
A. E. Bokov ◽  
S. G. Mlyavykh ◽  
A. A. Bulkin ◽  
A. Y. Aleynik ◽  
M. V. Rasteryeva
Keyword(s):  
Lumbar Spine ◽  
Cancellous Bone ◽  
Cross Sectional Study ◽  
Facet Joints ◽  
Mineral Density ◽  
Cross Sectional ◽  
Property Assessment ◽  
Ct Data ◽  
The Right ◽  
Vertebra Body

Background. It is reported that radiodensity measured in Hounsfield units becomes more and more popular in bone property assessment, however also mismatch with DXA results is observed.Purpose. The aim of this study is to evaluate the relationships between the results of DXA and CT with a focus on explanations for observed discrepancies.Material and methods. This is a cross-sectional study; forty patients were enrolled, all patients underwent DXA and CT. A bone mineral density BMD (g/cm2 ) was calculated for each vertebra of a lumbar spine (L1-L4 inclusive), neck, upper neck, shaft, Wards triangle and trochanter of hip. Bone radiodensity in HU was taken from each vertebral body in the sagittal, axial and coronal planes. A total vertebra body radiodensity including cortical bone and radiodensity of only cancellous bone were calculated. To assess a potential impact on DXA and CT data agreement a mean radiodensity and square of the right and left vertebral pedicles and facet joints were measured for each vertebra.Results. A strong correlation between BMD measured using DXA and CT data was estimated with a multiply r accounting for 0,84169, p<0,0001, however the most contributing parameters were those calculated for facet joints. It has been detected that both radiodensity of only a cancellous bone and total have a weak correlation with matching BMD measurements of a proximal femur.Conclusion. The results of DXA could be strongly influenced by hypertrophic changes of facet joints. Both CT and DXA measurements taken from a lumbar spine may have a mismatch with figures taken from hip. 

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