The load-transfer pathway in trabecular bone is largely determined by its architecture. However, the influence of variations
in mineralization is not known. The goal of this study was to examine the influence of inhomogeneously distributed degrees
of mineralization (DMB) on intratrabecular stresses and strains. Cubic mandibular condylar bone specimens from fetal and newborn
pigs were used. Finite element models were constructed, in which the element tissue moduli were scaled to the local DMB. Disregarding
the observed distribution of mineralization was associated with an overestimation of average equivalent strain and underestimation
of von Mises equivalent stress. From the surface of trabecular elements towards their core the strain decreased irrespective
of tissue stiffness distribution. This indicates that the trabecular elements were bent during the compression experiment.
Inhomogeneously distributed tissue stiffness resulted in a low stress at the surface that increased towards the core. In contrast,
disregarding this tissue stiffness distribution resulted in high stress at the surface which decreased towards the core. It
was concluded that the increased DMB, together with concurring alterations in architecture, during development leads to a
structure which is able to resist increasing loads without an increase in average deformation, which may lead to damage. 相似文献
The deformation of bone when subjected to loads is not instantaneous but varies with time. To investigate this time-dependent behaviour sixteen bovine trabecular bone specimens were subjected to compressive loading, creep, unloading and recovery at multiple load levels corresponding to apparent strains of 2000–25,000 με. We found that: the time-dependent response of trabecular bone comprises of both recoverable and irrecoverable strains; the strain response is nonlinearly related to applied load levels; and the response is linked to bone volume fraction. Although majority of strain is recovered after the load-creep-unload-recovery cycle some residual strain always exists. The analysis of results indicates that trabecular bone becomes stiffer initially and then experiences stiffness degradation with the increasing load levels. Steady state creep rate was found to be dependent on applied stress level and bone volume fraction with a power law relationship. 相似文献
Cancellous centrum is a major component of the vertebral body and significantly contributes to its structural strength and
fracture risk. We hypothesized that the variability of cancellous bone properties in the centrum is associated with vertebral
strength. Microcomputed tomography (micro-CT)-based gray level density (GLD), bone volume fraction (BV/TV), and finite element
modulus (E) were examined for different regions of the trabecular centrum and correlated with vertebral body strength determined experimentally.
Two sets of images in the cancellous centrum were digitally prepared from micro-CT images of eight human vertebral bodies
(T10–L5). One set included a cubic volume (1 per vertebral centrum, n = 8) in which the largest amount of cancellous material from the centrum was included but all the shell materials were excluded.
The other set included cylindrical volumes (6 per vertebral centrum, n = 48) from the anterior (4 regions: front, center, left, and right of the midline of vertebra) and the posterior (2 regions:
left and right) regions of the centrum. Significant positive correlations of vertebral strength with GLD (r2 = 0.57, p = 0.03) and E (r2 = 0.63, p = 0.02) of the whole centrum and with GLD (r2 = 0.65, p = 0.02), BV/TV (r2 = 0.72, p = 0.01) and E (r2 = 0.85, p = 0.001) of the central region of the vertebral centrum were found. Vertebral strength decreased with increasing coefficient
of variation of GLD, BV/TV, and E calculated from subregions of the vertebral centrum. The values of GLD, BV/TV, and E in centrum were significantly smaller for the anterior region than for the posterior region. Overall, these findings supported
the significant role of regional variability of centrum properties in determining the whole vertebral strength. 相似文献
It is widely hypothesized that mechanical loading, specifically repetitive low‐intensity tasks, influences the inner structure of cancellous bone. As such, there is likely a relationship between handedness and bone morphology. The aim of this study is to determine patterns in trabecular bone between dominant and non‐dominant hands in modern humans. Seventeen healthy patients between 22 and 32 years old were included in the study. Radial carpal bones (lunate, capitate, scaphoid, trapezium, trapezoid, 1st, 2nd and 3rd metacarpals) were analyzed with high‐resolution micro‐computed tomography. Additionally, crush and pinch grip were recorded. Factorial analysis indicated that bone volume ratio, trabeculae number (Tb.N), bone surface to volume ratio (BS.BV), body weight, stature and crush grip were all positively correlated with principal components 1 and 2 explaining 78.7% of the variance. Volumetric and trabecular endostructural parameters (BV/TV, BS/BV or Tb.Th, Tb.N) explain the observed inter‐individual variability better than anthropometric or clinical parameters. Factors analysis regressions showed correlations between these parameters and the dominant side for crush strength for the lunate (r2 = 0.640, P < 0.0001), trapezium (r2 = 0.836, P < 0.0001) and third metacarpal (r2 = 0.763). However, despite a significant lateralization in grip strength for all patients, the endostructural variability between dominant and non‐dominant sides was limited in perspective to inter‐individual differences. In conclusion, handedness is unlikely to generate trabecular patterns of asymmetry. It appears, however, that crush strength can be considered for endostructural analysis in the modern human wrist. 相似文献
Progression of osteoporosis is caused by a decline in bone formation activity relative to the resorption activity. In this
paper, the authors carried out a theoretical analysis of the progression of osteoporosis to estimate the osteoporotic change
in the upper end of the femur. According to this analysis, the progression rate of osteoporosis in cancellous bone depends
on the product of remodeling activity,Ract, and the trabecular structure parameter,Ktr. To confirm that the theoretical results were reasonably comparable to actual osteoporotic change, these two factors were
measured in rabbits. From the results, it was concluded that the highest progression rate was shown in bar/barlike trabecular
structure (type 3); the next highest rate, was shown in plate/bar-like structure (type 2); and the plate/plate-like structure
(type 1) was the most insensible. Furthermore, the bone volume fractions of cancellous bone were measured at the upper end
of human femurs with and without osteoporosis. Then the measured value was compared with the theoretical value for each type
of trabecular structure. Results showed that the decrease in bone volume fraction predicted by Eq. 7 was well in accord with
the actual decrease. 相似文献
Vertebroplasty is a common and effective treatment for symptomatic osteoporotic vertebral compression fractures. However, the cemented and adjacent vertebras have a risk of recollapse due to largely unassured mechanisms, among which excessive stiffness of bone cement may be an important risk factor. This study aimed to find the most appropriate range of bone cement stiffness by analyzing its biomechanical effects on the augmented and adjacent vertebras of individual patient after vertebroplasty. A three-dimensional finite element model of T11-L1 osteoligamentous vertebras was reconstructed according to individual computed tomography data and validated by post mortem human subject experiment in literatures. Bone cement of varying stiffness was injected into the trabecular core of the T12 vertebra simulatively. The maximum von Mises stresses on cancellous and cortical bones of T11-L1 vertebras were analyzed under the loading conditions of flexion, extension, bending, and torsion. For the adjacent T11 and L1 vertebras, the stepwise elevation of the bone cement elastic modulus increased the maximum von Mises stress on the cancellous bone, but its effect on cortical bone was negligible. For the augmented T12 vertebra, the stresses on cancellous bone increased slightly under the loading condition of lateral bending and remained no impact on cortical bone. The linear interpolation revealed that the most suitable range of cement elastic modulus is 833.1 and 1408.1 Mpa for this patient. Increased elastic modulus of bone cement may lead to a growing risk of recollapse for the cemented vertebra as well as the adjacent vertebras. Our study provides a fresh perspective in clinical optimization of individual therapy in vertebroplasty.
Recent development of high-resolution imaging of cancellous bone allows finite element (FE) analysis of bone tissue stresses
and strains in individual trabeculae. However, specimen-specific stress/strain analyses can include effects of anatomical
variations and local damage that can bias the interpretation of the results from individual specimens with respect to large
populations. This study developed a standard (generic) ‘building-block’ of a trabecula for large-scale FE models. Being parametric
and based on statistics of dimensions of ovine trabeculae, this building block can be scaled for trabecular thickness and
length and be used in commercial or custom-made FE codes to construct generic, large-scale FE models of bone, using less computer
power than that currently required to reproduce the accurate micro-architecture of trabecular bone. Orthogonal lattices constructed
with this building block, after it was scaled to trabeculae of the human proximal femur, provided apparent elastic moduli
of ∼ 150 MPa, in good agreement with experimental data for the stiffness of cancellous bone from this site. Likewise, lattices
with thinner, osteoporotic-like trabeculae could predict a reduction of ∼30% in the apparent elastic modulus, as reported
in experimental studies of osteoporotic femora. Based on these comparisons, it is concluded that the single-trabecula element
developed in the present study is well-suited for representing cancellous bone in large-scale generic FE simulations. 相似文献
The pulse transmission ultrasonic technique is used to characterise the actual pathway and the wavelength dependence in relation
to the bone specimen and microstructural dimensions. The average velocity through individual trabecular bone is 2901 m s−1 (SD 161), and the mean velocity through cylindrical cancellous bone specimens is 2717 m s−1 (SD 171). Thus, the velocity through the cylindrical cancellous bone specimens is underestimated by as much as 6.4% of that
through individual trabeculae. There is statistically significant difference in the ultrasonic velocity between individual
trabeculae and cylindrical cancellous bone specimens (p=0.0012). 相似文献
The aim of this study was to obtain the apparent and tissue-level mechanical parameters of vertebral cancellous bones using
micro-finite element analysis, and to identify the regional variations and their relative differences with respect to aging.
Ninety trabecular specimens were obtained from six normal L4 vertebral bodies of six male cadavers in two age groups, three
aged 62 years and three aged 69 years, and then were scanned using a high-resolution micro-Computed Tomography (micro-CT)
system. The obtained micro-CT reconstruction models were then converted to micro-finite element models. Micro-finite element
analyses were done to determine the apparent Young’s moduli and tissue-level Von Mises stress distribution for each trabecular
specimen on the longitudinal direction, and medial–lateral and anterior–posterior directions (transverse directions), respectively. Regional variations about the mechanical parameters at both apparent and
tissue levels in different transverse layers and vertical columns within and between the two age groups were then analyzed.
The results showed significant decreases in the apparent Young’s moduli in each direction with aging, and those in the two
transverse directions decreased more with aging compared with the longitudinal direction. Furthermore, there were no statistically
significant differences between the mechanical parameters in the two transverse directions in both age groups. This study
offered an insight into the distributions and variations of mechanical properties within a vertebral body. The mechanical
parameters calculated from this study may help in a better understanding of regional fracture risks and the vertebral fracture
mechanism in the prevention of osteoporotic fracture in elder individuals. 相似文献
Patient-specific finite element (FE) modelling is a promising technology that is expected to support clinical assessment of
the spine in the near future. To allow rapid, robust and economic patient-specific modelling of the whole spine or of large
spine segments, it is practicable to consider vertebral cancellous bone in the spine as a continuum material, but the elastic
modulus of that continuum material must reflect the quality of the individual vertebral bone. A numerical parametric model
of lattice trabecular architecture has been developed for determining the apparent elastic modulus of cancellous bone Ecb in vertebrae. The model inputs were apparent morphological parameters (trabecular thickness TbTh and trabecular separation TbSp) and the bone mineral density (BMD), which can all be measuredin vivo, using the spatial resolution of current clinical quantitative computed tomography (QCT) commercial whole-body scanners.
The model predicted that Ecb values between 30 and 110 MPa represent normal morphology and BMD of human spinal cancellous bone. The present Ecb to TbTh, TbSp and BMD relationships pave the way for automatic generation of patientspecific continuum FE spine models that consider the
individual's osteoporotic or other degenerative condition of cancellous bone. 相似文献
The ultrasound velocity and attenuation were examined in 16 sets of human patellae. The average ultrasound velocity of patella was shown to be greater in the superior/inferior direction than in the anterior/posterior and medial/lateral directions. The distribution of bone mineral density (BMD) was also examined. The BMD of the patella varied with location. BMD values were largest at the superior and lateral regions and decreased inferiorly and medially. A two-dimensional finite element analysis was performed on each patella. The maximum von Mises stress occurred along the cortical shell on the non-articular surface. The trabecular von Mises stress existed in the posterior region of the patella. Correlation study showed that patellar BMD was significantly associated with each of three directional ultrasound velocities. The relationship between BMD and ultrasound attenuation was not significant. It was also found that the ultrasound velocity and attenuation were not significantly correlated with the maximum von Mises stress. 相似文献