Biomechanical Study of Vertebral Compression Fracture Using Finite Element Analysis (original) (raw)
Related papers
International Journal of Applied Physics and Mathematics, 2014
The aim of this work is to assess the biomechanical response or load transfer response between osteoporotic (with first lumbar (L1) vertebral compression fracture) and healthy vertebrae in five vertebral physiological motions namely as compression, flexion, extension, lateral bending and axial rotation. For this purpose, an image-basedheterogeneous three-dimensional patient-specific of lumbar and thoracic spinal unit (T12-L2) finite element models for healthy and osteoporotic subjects were created. The finite element analysis have shown that one of the most significant effects of osteoporosis is the tendency to produce higher stress and strain in the cancellous region of the vertebral body. The maximum stress and strain was 4.53 fold (compression) and 5.43 fold (axial rotation) higher for the osteoporotic than the healthy subject, respectively, under the similar loading activity. Uneven stress distribution patterns also have been detected in the osteoporotic vertebrae rather than the healthy vertebrae. All of these characteristicsare reflected bya reduced structural strength and bone mass which might lead to an increased risk of fracture. These results strengthen the paradigm of a strong relationship between osteoporosis and its high susceptibility to fracture.
Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research, 2015
The biomechanical mechanisms leading to vertebral fractures are not well understood. Clinical and laboratory evidence suggests that the vertebral endplate plays a key role in failure of the vertebra as a whole, but how this role differs for different types of vertebral loading is not known. Mechanical testing of human thoracic spine segments, in conjunction with time-lapsed micro-computed tomography, enabled quantitative assessment of deformations occurring throughout the entire vertebral body under axial compression combined with anterior flexion ("combined loading") and under axial compression only ("compression loading"). The resulting deformation maps indicated that endplate deflection was a principal feature of vertebral failure for both loading modes. Specifically, the onset of endplate deflection was temporally coincident with a pronounced drop in the vertebra's ability to support loads. The location of endplate deflection, and also vertebral strength,...
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 ...
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.
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.
Technology and health care : official journal of the European Society for Engineering and Medicine, 2020
BACKGROUND The use of fresh-frozen (FF) specimens represents the gold standard for biomechanical investigations. Since FF specimens are often difficult to obtain, chemical-fixed specimens (formalin (FA), Thiel (TH)) are also used. OBJECTIVE Since fixation methods can alter the mechanical properties of bone tissue, the purpose of this study was to examine their influence on the fracture force of lumbar vertebral bodies (VB). METHODS First the VB were subdivided into three focus groups: FF, TH, and FA. After removing the soft tissue and the processus transverses of all VB, the endplates were planned with a thin layer of epoxy resin, in order to apply a constant strain to the surface and sub-surface. The VB were subjected to axial compression tests in order to determine fracture force. Lastly a standardized compression fracture was generated. RESULTS The mean values of the fracture force of the focus groups were 4529.5 N (FF), 3211.3N (TH) and 2947.9N (FA). Consequently a significant d...
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).
Biomechanics of Vertebral Fractures and the Vertebral Fracture Cascade
Current Osteoporosis Reports, 2010
Vertebral fractures (VFxs) are the most common osteoporotic fracture, and are a strong risk factor for future fracture. The presence of a VFx greatly increases the risk of sustaining subsequent VFxs-a phenomenon often referred to as the "vertebral fracture cascade." VFxs do not occur uniformly along the spine, but occur more often at the midthoracic and thoracolumbar regions than elsewhere. It is likely that both the vertebral fracture cascade and the bimodal distribution of VFx along the spine are attributable to biomechanical factors. VFxs occur when the forces applied to the vertebral body exceed its strength. Loading on the spine is primarily determined by a person's height, weight, muscle forces, and the task or movement performed, but can also be affected by other factors, such as spinal curvature and invertebral disk deterioration. Vertebral strength is determined mainly by bone size, shape, and bone mineral density, and secondarily by bone microarchitecture, collagen characteristics, and microdamage. Better understanding of VFx etiology is hampered by the fact that most VFxs do not come to clinical attention; therefore, the factors and activities that cause VFxs remain ill defined, including possible differences in the etiology of acute fractures versus those of slow onset. Additional research is needed to elucidate the precise mechanical, morphologic, and biological mechanisms that underlie VFx to improve strategies for assessing VFx risk and preventing the vertebral fracture cascade.
Rate-dependent fracture characteristics of lumbar vertebral bodies
Journal of the Mechanical Behavior of Biomedical Materials, 2015
Experimental testing incorporating lumbar columns and isolated components is essential to advance the understanding of injury tolerance and for the development of safety enhancements. This study incorporated a whole column axial acceleration model and an isolated vertebral body model to quantify compression rates during realistic loading and compressive tolerance of vertebrae. Eight lumbar columns and 53 vertebral bodies from 23 PMHS were used. Three-factor ANOVA was used to determine significant differences (po0.05) in physiologic and failure biomechanics based on compression rate, spinal level, and gender. Results demonstrated a significant increase in ultimate force (i.e., fracture) from lower to higher compression rates. Ultimate stress also increased with compression rate. Displacement and strain to failure were consistent at both compression rates. Differences in ultimate mechanics between vertebral bodies obtained from males and females demonstrated non-significant trends, with female vertebral bodies having lower ultimate force that would be associated with decreased injury tolerance. This was likely a result of smaller vertebrae in that population. Combined with existing literature, results presented in this manuscript contribute to the understanding of lumbar spine tolerance during axial loading events that occur in both military and civilian environments with regard to effects of compression rate and gender.