Quantitative computed tomography estimates of the mechanical properties of human vertebral trabecular bone

Abstract

The objective of this study was to report our quantitative computed tomography (QCT) density-mechanical property regressions for trabecular bone for use in biomechanical modelling of the human spine. Cylindrical specimens of human vertebral trabecular bone (from T I 0 to L4) were cored from 32 cadavers (mean f SD age = 70.1 i 16.8; 13 females, 19 males) and scanned using QCT. Mechanical tests were conducted using a protocol that minimized end-artifacts over the apparent density range tested (0.09-0.38 g/ cm3). To account for the presence of multiple specimens per donor in this data set, donor was treated as a random effect in the regression model. Mean modulus (319 i 189 MPa) was higher and mean yield strain (0.78 z t 0.06%) was lower than typical values reported previously due to minimization of the end-artifact errors. QCT density showed a strong positive correlation with modulus ( n = 76) and yield stress (v2 = 0.90-0.95, n = 53, p < 0,001). There was a weak positive linear correlation with yield strain (r' = 0.58, n = 53, p = 0.07). Prediction errors, incurred when estimating modulus or strength for specimens from a new donor, were 30-36'X of the mean values of these properties. Direct QCT density-mechanical property regressions gave more precise predictions of mechanical properties than if physically measured wet apparent density was used as an intermediate variable to predict mechanical properties from QCT density. Use of these QCT density-mechanical property regressions should improve the fidelity of QCT-based biomechanical models of the human spine for whole bone and bone-implant analyses. 0

Effects of preexisting microdamage, collagen cross‐links, degree of mineralization, age, and architecture on compressive mechanical properties of elderly human vertebral trabecular bone

“…[39][40][41][42][43] Additionally, our low measurements could be due to differences in testing methodologies, anatomic site and/or donor age. 33,34,[39][40][41][42][43][44][45] We note that our relationship between BV/TV and elastic modulus appears weaker than that in several other studies, where 60-80% of the variability in elastic modulus is explained by volume fraction. This FACTORS INFLUENCING HUMAN VERTEBRAL TRABECULAR BONE MECHANICS may be due to the limited age range (and therefore bone density) of our donors compared to previously published studies, as a broader age (and density) range would likely lead to a higher correlation coefficient.…”

Comparison of quantitative computed tomography-based measures in predicting vertebral compressive strength

“…A final limitation of our study is that the material model used in the FE analyses does not precisely simulate the mechanical response of vertebral bone. First, the elastic behavior of the bone was based on empirical density-modulus relationships from compression tests on relatively large sections of vertebral trabecular bone (20). The validity of applying these relationships to smaller bone volumes, e.g., 1 mm cubic "voxels" as in this study, has not yet been established.…”

“…The vertebral bone was assumed to be a transversely isotropic, linearly elastic-perfectly plastic material. Material properties were assigned on an element-specific basis using previously established density-modulus and density-strength relationships for vertebral trabecular bone (20). Because the clinical resolution QCT scans used in this study did not produce a discrete image of the cortical shell, elements along the periphery of the bone were treated as trabecular bone in assigning material properties.…”

Biomechanical evaluation of two different vertebral interbody devices by using QCT-based case-specific nonlinear finite element models

“…For each set, the elastic moduli and the yield strength were computed using experimentally established vertebra-specific relationships. [8][9] The applied material properties are summarized in Boundary conditions were set to represent the mechanical tests. The lower plane of the inferior embedding layer as fully constrained.…”