Dynamic Load Response of the Lumbar Spine in Flexion (original) (raw)
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Dynamic load response of the in vitro lumbar spine in flexion
1992
Tue biomechanical response of the in vitro lumbar motion segment (functional spinal unit, FSU) under a dynamic (transient) flexion-shear load was detennined. Tue load was transferred to the specimen by a padded pendulum and simulated a flexion-distraction injury, a so called lap seat-belt injury. Tue load response of the specimen was measured with a force and moment transducer, and the motions were detennined with high speed photography. Two series of tests were made with 10 specimens in each, with two different load pulses: one moderate pulse (mean acce leration 2.5 g, duration 150 ms) and one severe pulse (mean acceleration 8 g, durarion 250 ms). Tue resuJts showed that the moderate load pulse caused initial flexion-distraction injuries at a mean bending moment of 113 Nm and a mean shear force of 346 N. Tue maximum flexion angulation attained during the loading sequence was 14 •. Tue severe load pulse caused evident signs of failure or total rupture of the segments at a mean bending moment of 151 Nm and a mean shear force of 481 N. Tue flexion angulation just before failure was 19•. A statistically significant correlation (r>0.7, p<0.05) was found between the load response and the height of the segment, the load response and the lateral disc diameter, and the load response and the bone mineral content (BMC) in the venebrae. Comparisons were made with previous established thresholds for st.atic flcxion-shear loading. Tue results indicated that thresholds for initial and ultimate flexion-distraction injury respectively are in the same range for static and transient loading conditions.
Lumbar Spine System: Biomechanical Model Evaluation
2004
Considering lumbar spine injuries, investigations were pointed in many different directions. Our approach in case of lumbar spine under external mechanical load is to propose approach that can offer better understanding of lumbar spine functionality. For this purpose, this paper describes hypothetic model of lumbar spine mechanism, reduced on sagittal mid plane. As found in our previous investigations, there is principle that can explain response of lumbar spine to applied external mechanical load. Our findings are compared with experimental results. Beside comparison of our findings, comparison with other authors shows even more similarities. Conclusion of this paper comes through noticeable dependence of lumbar spine extension torque and trunk inclination. Connection between lumbar spine responses and applied external mechanical load can be defined as regulative system, however very complex. Used approach can have implications in further biomechanical modelling. For evaluation of ...
Failure Tolerance of the Human Lumbar Spine in Combined Compression and Flexion Loading
arXiv: Medical Physics, 2021
Vehicle safety systems have substantially decreased motor vehicle crash-related injuries and fatalities, but injuries to the lumbar spine still have been reported. Experimental and computational analyses of upright and, particularly, reclined occupants in frontal crashes have shown that the lumbar spine can be subjected to axial compression followed by combined compression-flexion loading. Lumbar spine failure tolerance in combined compression-flexion has not been widely explored in the literature. Therefore, the goal of this study was to measure the failure tolerance of the lumbar spine in combined compression and flexion. Forty 3-vertebra lumbar spine segments were pre-loaded with axial compression and then subjected to dynamic flexion bending until failure. Clinically relevant middle vertebra fractures were observed in twenty-one of the specimens, including compression and burst fractures. The remaining nineteen specimens experienced failure at the potting grip interface. Since s...
Shear strength of the human lumbar spine
Clinical Biomechanics, 2012
Background: Shear loading is recognised as a risk factor for lower back pain. Previous studies of shear loading have either not addressed the influence of age, bone mineral density, axial height loss due to creep or were performed on animal specimens. Methods: Intact human lumbar motion segments (L2-3) were tested in shear using a modified materials testing machine, while immersed in a Ringer bath at 37°C. Vertebrae were rigidly embedded in neutral posture (0°flexion) and subjected to a constant axial compression load of 500 N. Shear was applied to three groups: 'Young-No-Creep' (20-42 years), 'Young-Creep' (22-38 years, creep 1000 N for 1 h) and 'Old-No-Creep' (44-64 years). Failure was induced by up to 15 mm of anterior shear displacement at a rate of 0.5 mm/s. The trabecular and apophyseal joint bone mineral densities were evaluated from computed tomography images of the intact lumbar spines. Findings: Peak shear force correlated positively with trabecular bone mineral density for specimens tested without axial creep. No significant differences were observed with respect to age. During shear overload specimens increased in height in the axial direction. Interpretation: Trabecular bone mineral density can be used to predict the peak force of lumbar spine in shear in neutral posture.
The Influence of Muscle Forces on the Stress Distribution in the Lumbar Spine
The Open Spine Journal, 2011
Introduction: Previous studies of bone stresses in the human lumbar spine have relied on simplified models when modeling the spinal musculature, even though muscle forces are likely major contributors to the stresses in the vertebral bones. Detailed musculoskeletal spine models have recently become available and show good correlation with experimental findings. A combined inverse dynamics and finite element analysis study was conducted in the lumbar spine to investigate the effects of muscle forces on a detailed musculoskeletal finite element model of the 4 th lumbar vertebral body. Materials and Methodology: The muscle forces were computed with a detailed and validated inverse dynamics musculoskeletal spine model in a lifting situation, and were then applied to an orthotropic finite element model of the 4 th lumbar vertebra. The results were compared with those from a simplified load case without muscles. Results: In general the von Mises stress was larger by 30 %, and even higher when looking at the von Mises stress distribution in the superio-anterior and central part of the vertebral body and in the pedicles. Conclusion: The application of spine muscles to a finite element model showed markedly larger von Mises stress responses in the central and anterior part of the vertebral body, which can be tolerated in the young and healthy spine, but it would increase the risk of compression fractures in the elderly, osteoporotic spine.
Study of Compression-Related Lumbar Spine Fracture Criteria Using a Full Body Fe Human Model
A detailed lumbar spine FE component model (including vertebrae, inter-vertebral discs, all ligaments and facet joints of T12-L5) was built per the Global Human Body Model Consortium (GHBMC) CAD data. The lumbar model was correlated with the Post-Mortem Human Subject (PMHS) lumbar spine tests under flexion, compression and anterior shear loading modes in the physiological ranges (Belwadi, 2008), and was validated with the tests of PMHS functional spine units (FSU) of three adjunct vertebrae in fracture loading conditions (Belwadi, 2008). The lumbar model was integrated into the Takata in-house 50th percentile full human body model. The full body model was validated with the Wayne State University (WSU) PMHS vertical sled tests under +Gz loading in the range of 6G to 10G (Prasad, 1973). Good agreements were found between the test results and the FE model. At the lumbar component levels, stiffness and failure loads along with failure modes were correlated. At the full body level, the ...
Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 2017
Quantification of biomechanical tolerance is necessary for injury prediction and protection of vehicular occupants. This study experimentally quantified lumbar spine axial tolerance during accelerative environments simulating a variety of military and civilian scenarios. Intact human lumbar spines (T12-L5) were dynamically loaded using a custom-built drop tower. Twenty-three specimens were tested at sub-failure and failure levels consisting of peak axial forces between 2.6 and 7.9 kN and corresponding peak accelerations between 7 and 57 g. Military aircraft ejection and helicopter crashes fall within these high axial acceleration ranges. Testing was stopped following injury detection. Both peak force and acceleration were significant (p < 0.0001) injury predictors. Injury probability curves using parametric survival analysis were created for peak acceleration and peak force. Fifty-percent probability of injury (95%CI) for force and acceleration were 4.5 (3.9-5.2 kN), and 16 (13-1...
Journal of applied biomechanics, 2012
This study presents a CT-based finite element model of the lumbar spine taking into account all function-related boundary conditions, such as anisotropy of mechanical properties, ligaments, contact elements, mesh size, etc. Through advanced mesh generation and employment of compound elements, the developed model is capable of assessing the mechanical response of the examined spine segment for complex loading conditions, thus providing valuable insight on stress development within the model and allowing the prediction of critical loading scenarios. The model was validated through a comparison of the calculated force-induced inclination/deformation and a correlation of these data to experimental values. The mechanical response of the examined functional spine segment was evaluated, and the effect of the loading scenario determined for both vertebral bodies as well as the connecting intervertebral disc.
A Non-linear Finite Element Model for Assessment of Lumbar Spinal Injury Due to Dynamic Loading
International Joint Conference on Biomedical Engineering Systems and Technologies, 2013
In this paper a highly detailed model of an adult lumbar spine (L1-L5) was recreated based on Computed Tomography. Next to the viscoelastic deformation of the intervertebral discs, cortical and cancellous bone anisotropy was considered, while seven types of ligaments were simulated either by solid or cable elements. The dynamic behaviour of the spine segment was assessed through stress-strain curves, provoking a nonlinear response of all implicated tissues' material properties. The model was subjected to dynamic loading to determine abnormalities in the anatomy's stress equilibrium that could provoke gait disturbances. Results indicated the introduced methodology as an effective alternative to in vitro investigations, capable of providing valuable insight on critical movements and loads of potential patients, as the model can be employed to optimize therapeutic training or threshold kinematics of any given lumbar spine pathology.
Characterization of the Mechanical Response of the Lumbar Spine
2011
Characterization of the Mechanical Response of the Lumbar Spine Shannon A. Zirbel Department of Mechanical Engineering, BYU Master of Science The primary objective of this research is to associate lumbar segmental mechanical response with intervertebral disc degeneration under physiologic testing conditions. Because no mathematical model exists for lumbar spine segmental rotations, a portion of this thesis evaluates potential methods for curve fitting the torque-rotation curves. The Dual Inflection Point (DIP) Boltzmann equation was developed during the course of this research and is presented here as a method for fitting spinal motion data wherein a physical meaning can be assigned to each of the model coefficients. This model can tell us more about the effects of degeneration, testing conditions, and other factors that are expressed in the change in spinal motion. Previous studies have investigated the relationship between the degeneration grade and flexibility of the intervertebr...