Finite Element Analysis of Osteoporotic Vertebrae with First Lumbar (L1) Vertebral Compression Fracture (original) (raw)
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Biomechanical Study of Vertebral Compression Fracture Using Finite Element Analysis
Journal of Applied Mathematics and Physics, 2017
This research aimed to mechanically analyze vertebral stress concentration in one healthy subject and one subject with osteoporotic first lumbar (L1) vertebral compression fracture by using finite element analysis (FEA). We constructed three-dimensional image-based finite element (FE) models (Th12L2) by using computed tomographic (CT) digital imaging and communications in medicine (DICOM) for each patient and then conducted exercise stress simulations on the spine models. The loadings on the 12th thoracic vertebra (Th12) due to compression, flexion, extension, lateral bending, and axial rotation were examined within the virtual space for both spine models. The healthy and vertebral compression fracture models were then compared based on the application of equivalent vertebral stress. The comparison showed that vertebral stress concentration increased with all stresses in the vertebral compression fracture models. In particular, compression and axial rotation caused remarkable increases in stress concentration in the vertebral compression fracture models. These results suggest that secondary vertebral compression fractures are caused not only by bone fragility but possibly also by the increase in vertebral stress concentration around the site of the initial fracture.
The effect of osteoporotic vertebral fracture on predicted spinal loads in vivo
European Spine Journal, 2006
The aetiology of osteoporotic vertebral fractures is multi-factorial, and cannot be explained solely by low bone mass. After sustaining an initial vertebral fracture, the risk of subsequent fracture increases greatly. Examination of physiologic loads imposed on vertebral bodies may help to explain a mechanism underlying this fracture cascade. This study tested the hypothesis that model-derived segmental vertebral loading is greater in individuals who have sustained an osteoporotic vertebral fracture compared to those with osteoporosis and no history of fracture. Flexion moments, and compression and shear loads were calculated from T2 to L5 in 12 participants with fractures (66.4 ± 6.4 years, 162.2 ± 5.1 cm, 69.1 ± 11.2 kg) and 19 without fractures (62.9 ± 7.9 years, 158.3 ± 4.4 cm, 59.3 ± 8.9 kg) while standing. Static analysis was used to solve gravitational loads while muscle-derived forces were calculated using a detailed trunk muscle model driven by optimization with a cost function set to minimise muscle fatigue. Least squares regression was used to derive polynomial functions to describe normalised load profiles. Regression co-efficients were compared between groups to examine differences in loading profiles. Loading at the fractured level, and at one level above and below, were also compared between groups. The fracture group had significantly greater normalised compression (p = 0.0008) and shear force (p < 0.0001) profiles and a trend for a greater flexion moment profile. At the level of fracture, a significantly greater flexion moment (p = 0.001) and shear force (p < 0.001) was observed in the fracture group. A greater flexion moment (p = 0.003) and compression force (p = 0.007) one level below the fracture, and a greater flexion moment (p = 0.002) and shear force (p = 0.002) one level above the fracture was observed in the fracture group. The differences observed in multi-level spinal loading between the groups may explain a mechanism for increased risk of subsequent vertebral fractures. Interventions aimed at restoring vertebral morphology or reduce thoracic curvature may assist in normalising spine load profiles.
FEM-Based Compression Fracture Risk Assessment in Osteoporotic Lumbar Vertebra L1
Applied Sciences
This paper presents a finite element method (FEM)-based fracture risk assessment in patient-specific osteoporotic lumbar vertebra L1. The influence of osteoporosis is defined by variation of parameters such as thickness of the cortical shell, the bone volume–total volume ratio (BV/TV), and the trabecular bone score (TBS). The mechanical behaviour of bone is defined using the Ramberg–Osgood material model. This study involves the static and nonlinear dynamic calculations of von Mises stresses and follows statistical processing of the obtained results in order to develop the patient-specific vertebra reliability. In addition, different scenarios of parameters show that the reliability of the proposed model of human vertebra highly decreases with low levels of BV/TV and is critical due to the thinner cortical bone, suggesting high trauma risk by reason of osteoporosis.
Buckling of Osteoporotic Lumbar: Finite Element Analysis
Research in Medical & Engineering Sciences, 2019
Research in Medical & Engineering Sciences (30% for males) experience at least one osteoporotic vertebral fracture during their life [5,6]. Consequently, research on osteoporotic degradation is basically focused on evaluation of the change of mechanical properties in the vertebral bone tissue [7-9]. It was found, however, that macroscopic vertebral properties strongly correlate with bone density decrease. Therewith, bone mineral density (BMD) is probably the single directly measurable physical quantity.
The Spine Journal, 2015
BACKGROUND CONTEXT: With an increasing prevalence of low back pain, physicians strive to optimize the treatment of patients with degenerated motion segments. There exists a consensus in literature that osteoporotic patients exhibit nonphysiologic loading patterns, while degenerated intervertebral discs (IVDs) are also believed to alter spine biomechanics. PURPOSE: To evaluate alterations occurring in lumbosacral spine biomechanics of an osteoporotic model, with or without IVD degeneration, when compared with a healthy spine segment. STUDY DESIGN: The investigation was based on finite element (FE) analysis of a patientspecific lumbosacral spine model. METHODS: A biorealistic model of a lumbosacral spine segment is introduced to determine the morbidity of disc degeneration and osteoporosis. The model was verified and validated for the purpose of the study and subjected to a dynamic FE analysis, considering anisotropic bone properties and solid ligamentous tissue. RESULTS: The yielded results merit high clinical interest. Osteoporosis resulted in a nonuniform increase of facet joint loading, which was even more pronounced in the scenario simulating a degenerated disc. The results also revealed an enslavement of intradiscal pressure to the disc state (in the degenerated and superior adjacent level). CONCLUSIONS: The investigation presented refined insight into the dynamic biomechanical response of a degenerated spine segment. The increase in the calculated occurring stresses was considered as critical in the motion segment adjacent and superior to the degenerated one. This suggests that prevalent trauma in a motion segment may be a symptomatic condition of a poorly treated formal pathology in the inferior spine level. Ó 2015 Elsevier Inc. All rights reserved.
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 ...
Osteoporotic vertebral fractures represent major cause of disability, loss of quality of life and even mortality among the elderly population. Decisions on drug therapy are based on the assessment of risk factors for fracture, from bone mineral density measurements. The combination of biomechanical models with clinical studies could better estimate bone strength and support the specialists in their decision. A model to assess the probability of fracture, based on the Damage and Fracture Mechanics has been developed, evaluating the mechanical magnitudes involved in the fracture process from clinical bone mineral density measurements. The model is intended for simulating the degenerative process in the skeleton, with the consequent lost of bone mass and hence the decrease of its mechanical resistance which enables the fracture due to different traumatisms. Clinical studies were chosen, both in non-treatment conditions and receiving drug therapy, and fitted to specific patients according their actual bone mineral density measures. The predictive model is applied in a finite element simulation of the lumbar spine. The fracture zone would be determined according loading scenario (fall, impact, accidental loads, etc.), using the mechanical properties of bone obtained from the evolutionary model corresponding to the considered time. Bone mineral density evolution in untreated patients and in those under different * Corresponding author. E. López et al. 528 treatments was analyzed. Evolutionary curves of fracture probability were obtained from the evolution of mechanical damage. The evolutionary curve of the untreated group of patients presented a marked increase of the fracture probability, while the curves of patients under drug treatment showed variable decreased risks, depending on the therapy type. The finite element model allowed obtaining detailed maps of damage and fracture probability, identifying high-risk local zones at vertebral body, which are the usual localization of osteoporotic vertebral fractures. The developed model is suitable for being used in individualized cases. The model might better identify at-risk individuals in early stages of osteoporosis and might be helpful for treatment decisions.
Determinants of the mechanical behavior of human lumbar vertebrae after simulated mild fracture
Journal of Bone and Mineral Research, 2011
The ability of a vertebra to carry load after an initial deformation and the determinants of this postfracture load-bearing capacity are critical but poorly understood. This study aimed to determine the mechanical behavior of vertebrae after simulated mild fracture and to identify the determinants of this postfracture behavior. Twenty-one human L 3 vertebrae were analyzed for bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) and for microarchitecture by micro-computed tomography (mCT). Mechanical testing was performed in two phases: initial compression of vertebra to 25% deformity, followed, after 30 minutes of relaxation, by a similar test to failure to determine postfracture behavior. We assessed (1) initial and postfracture mechanical parameters, (2) changes in mechanical parameters, (3) postfracture elastic behavior by recovery of vertebral height after relaxation, and (4) postfracture plastic behavior by residual strength and stiffness. Postfracture failure load and stiffness were 11% AE 19% and 53% AE 18% lower than initial values ( p ¼ .021 and p < .0001, respectively), with 29% to 69% of the variation in the postfracture mechanical behavior explained by the initial values. Both initial and postfracture mechanical behaviors were significantly correlated with bone mass and microarchitecture. Vertebral deformation recovery averaged 31% AE 7% and was associated with trabecular and cortical thickness (r ¼ 0.47 and r ¼ 0.64; p ¼ .03 and p ¼ .002, respectively). Residual strength and stiffness were independent of bone mass and initial mechanical behavior but were related to trabecular and cortical microarchitecture (jrj ¼ 0.50 to 0.58; p ¼ .02 to .006). In summary, we found marked variation in the postfracture load-bearing capacity following simulated mild vertebral fractures. Bone microarchitecture, but not bone mass, was associated with postfracture mechanical behavior of vertebrae. ß Note: D ¼ difference between postfracture and initial parameters in % [mean AE SD (range)]. The comparisons between initial and postfracture mechanical parameters were performed using Wilcoxon signed-rank tests ( Ã p < .05).
A review of anatomical and mechanical factors affecting vertebral body integrity
International Journal of Medical Sciences, 2000
A Ab bs st tr ra ac ct t Background: The aetiology of osteoporotic vertebral fracture is multifactorial and may be conceptualised using a systems framework. Previous studies have established several correlates of vertebral fracture including reduced vertebral cross-sectional area, weakness in back extensor muscles, reduced bone mineral density, increasing age, worsening kyphosis and recent vertebral fracture. Alterations in these physical characteristics may influence biomechanical loads and neuromuscular control of the trunk and contribute to changes in subregional bone mineral density of the vertebral bodies.