Effects of Intracortical Porosity on Fracture Toughness in Aging Human Bone: A μCT-Based Cohesive Finite Element Study

2007 ◽  
Vol 129 (5) ◽  
pp. 625-631 ◽  
Author(s):  
Ani Ural ◽  
Deepak Vashishth
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Cortical Bone ◽  
Microcomputed Tomography ◽  
Compact Tension ◽  
Osteoporotic Bone ◽  
Initiation Toughness ◽  
Fracture Properties ◽  
Age Related ◽  
Age Related Changes

The extent to which increased intracortical porosity affects the fracture properties of aging and osteoporotic bone is unknown. Here, we report the development and application of a microcomputed tomography based finite element approach that allows determining the effects of intracortical porosity on bone fracture by blocking all other age-related changes in bone. Previously tested compact tension specimens from human tibiae were scanned using microcomputed tomography and converted to finite element meshes containing three-dimensional cohesive finite elements in the direction of the crack growth. Simulations were run incorporating age-related increase in intracortical porosity but keeping cohesive parameters representing other age-related effects constant. Additional simulations were performed with reduced cohesive parameters. The results showed a 6% decrease in initiation toughness and a 62% decrease in propagation toughness with a 4% increase in porosity. The reduction in toughnesses became even more pronounced when other age-related effects in addition to porosity were introduced. The initiation and propagation toughness decreased by 51% and 83%, respectively, with the combined effect of 4% increase in porosity and decrease in the cohesive properties reflecting other age-related changes in bone. These results show that intracortical porosity is a significant contributor to the fracture toughness of the cortical bone and that the combination of computational modeling with advanced imaging improves the prediction of the fracture properties of the aged and the osteoporotic cortical bone.

Effects of Aging on the Toughness of Human Cortical Bone: A Study from Nano to Macro Size-Scales

2004 ◽  
Vol 844 ◽  
Author(s):  
Ravi K. Nalla ◽  
Jamie J. Kruzic ◽  
John H. Kinney ◽  
Mehdi Balooch ◽  
Joel W. Ager ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Crack Growth ◽  
Bone Fracture ◽  
Ex Vivo ◽  
Longitudinal Direction ◽  
Initiation Toughness ◽  
Fracture Properties ◽  
Human Cortical Bone ◽  
Age Related ◽  
Effects Of Aging

ABSTRACTAge-related deterioration of both the fracture properties and the architecture of bone, coupled with increased life expectancy, are factors leading to the increasing incidence of bone fracture in the elderly. In order to facilitate the development of treatments which counter this increased fracture risk, a thorough understanding of how fracture properties degrade with age is required. The present study describes ex vivo fracture experiments to quantitatively assess the effects of aging on the fracture toughness of human cortical bone in the longitudinal direction. Because cortical bone exhibits rising crack-growth resistance with crack extension, we depart from most previous studies by evaluating the toughness in terms of resistance-curve (R-curve) behavior, measured for bone taken from donors 34 to 99 years old. Using this approach, both the crack-initiation and crack-growth toughness are determined and are found to deteriorate with age; the initiation toughness decreases ∼40% from 40 to 100 years, while the growth toughness is effectively eliminated over the same age range. Evidence from x-ray synchrotron tomography is provided to support the hypothesis that the reduction in crack-growth toughness is associated primarily with a degradation in the degree of extrinsic toughening, in particular involving crack bridging at the microstructural level in the wake of the crack. Atomic force microscope-based nanoidentation of individual collagen fibers revealed changes at the collagen fibrillar level and deep-ultraviolet Raman spectroscopy showed that the cross-linking at the nanostructural level also changes with age. These results should provide for a better mechanistic understanding of the increased propensity for bone fracture with age.

Mechanistic Aspects of Fracture of Human Cortical Bone

2004 ◽  
Vol 823 ◽  
Author(s):  
Ravi K. Nalla ◽  
Jamie J. Kruzic ◽  
John H. Kinney ◽  
R. O. Ritchie
Keyword(s):  
Fracture Toughness ◽  
Cortical Bone ◽  
Crack Extension ◽  
Three Dimensional ◽  
Compact Tension ◽  
Initiation Toughness ◽  
Post Test ◽  
X Ray Computed ◽  
Distal Direction

AbstractThere has been growing interest of late in the fracture properties of human bone. As understanding such properties in the context of the hierarchical microstructure of bone is of obvious importance, this study addresses the evolution of the in vitro fracture toughness with crack extension (Resistance-curve behavior) in terms of the salient mechanisms involved. Fracture-mechanics based measurements were performed on compact-tension specimens hydrated in Hanks' Balanced Salt Solution using cortical bone from mid-diaphyses of 34-41 year-old human humeri. Post-test observations of the crack path were made by optical microscopy and three-dimensional X-ray computed tomography. The fracture toughness was found to rise linearly with crack extension with a mean crack-initiation toughness of Ko ∼ 2.0 MPa√m for crack growth in the proximal-distal direction. The increasing cracking resistance had its origins in several toughening mechanisms, most notably crack bridging by uncracked ligaments. Uncracked-ligament bridging, which was observed by tomography in the wake of the crack, was identified as the dominant toughening mechanism responsible for the observed Rcurve behavior through compliance-based experiments. The extent and nature of the bridging zone was examined quantitatively using multi-cutting compliance experiments in order to assess the bridging stress distribution. The results obtained in this study provide an improved understanding of the mechanisms associated with the failure of cortical bone, and as such are of importance from the perspective of developing a realistic framework for fracture risk assessment, and for determining how the increasing propensity for fracture with age can be prevented.

Orientation and age-related dependence of the fracture toughness of cortical bone

1985 ◽  
Vol 18 (7) ◽  
pp. 521-522 ◽  
Author(s):  
W. Bonfield ◽  
J.C. Behiri ◽  
B. Cullen
Keyword(s):  
Fracture Toughness ◽  
Cortical Bone ◽  
Age Related

Finite Element Modeling of Microcrack Growth in Cortical Bone

2011 ◽  
Vol 78 (4) ◽  
Author(s):  
Susan Mischinski ◽  
Ani Ural
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Elastic Modulus ◽  
Crack Growth ◽  
Line Strength ◽  
Crack Deflection ◽  
Cement Line ◽  
Fracture Properties ◽  
Cement Lines ◽  
Microcrack Growth

Bone is similar to fiber-reinforced composite materials made up of distinct phases such as osteons (fiber), interstitial bone (matrix), and cement lines (matrix-fiber interface). Microstructural features including osteons and cement lines are considered to play an important role in determining the crack growth behavior in cortical bone. The aim of this study is to elucidate possible mechanisms that affect crack penetration into osteons or deflection into cement lines using fracture mechanics-based finite element modeling. Cohesive finite element simulations were performed on two-dimensional models of a single osteon surrounded by a cement line interface and interstitial bone to determine whether the crack propagated into osteons or deflected into cement lines. The simulations investigated the effect of (i) crack orientation with respect to the loading, (ii) fracture toughness and strength of the cement line, (iii) crack length, and (iv) elastic modulus and fracture properties of the osteon with respect to the interstitial bone. The results of the finite element simulations showed that low cement line strength facilitated crack deflection irrespective of the fracture toughness of the cement line. However, low cement line fracture toughness did not guarantee crack deflection if the cement line had high strength. Long cracks required lower cement line strength and fracture toughness to be deflected into cement lines compared with short cracks. The orientation of the crack affected the crack growth trajectory. Changing the fracture properties of the osteon influenced the crack propagation path whereas varying the elastic modulus of the osteon had almost no effect on crack trajectory. The findings of this study present a computational mechanics approach for evaluating microscale fracture mechanisms in bone and provide additional insight into the role of bone microstructure in controlling the microcrack growth trajectory.

In vivo quantification of age-related changes in human cortical bone thickness and porosity by HR-pQCT

Bone ◽  
2009 ◽  
Vol 44 ◽  
pp. S22
Author(s):  
K.K. Nishiyama ◽  
H.M. Macdonald ◽  
H.R. Buie ◽  
D.A. Hanley ◽  
S.K. Boyd
Keyword(s):  
Cortical Bone ◽  
Bone Thickness ◽  
Cortical Bone Thickness ◽  
Human Cortical Bone ◽  
Age Related ◽  
Age Related Changes

Experimental evaluation of fracture properties of bovine hip cortical bone using elastic–plastic fracture mechanics

2021 ◽  
pp. 1-10
Author(s):  
Waseem Ur Rahman ◽  
Rafiullah khan ◽  
Noor Rahman ◽  
Ziyad Awadh Alrowaili ◽  
Baseerat Bibi ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Cortical Bone ◽  
Elastic Deformation ◽  
Compact Tension ◽  
J Integral ◽  
Elastic Plastic ◽  
American Society ◽  
Fracture Specimens

BACKGROUND: Understanding the fracture mechanics of bone is very important in both the medical and bioengineering field. Bone is a hierarchical natural composite material of nanoscale collagen fibers and inorganic material. OBJECTIVE: This study investigates and presents the fracture toughness of bovine cortical bone by using elastic plastic fracture mechanics. METHODS: The J-integral was used as a parameter to calculate the energies utilized in both elastic deformation (Jel) and plastic deformation (Jpl) of the hipbone fracture. Twenty four different types of specimens, i.e. longitudinal compact tension (CT) specimens, transverse CT specimens, and also rectangular unnotched specimens for tension in longitudinal and transverse orientation, were cut from the bovine hip bone of the middle diaphysis. All CT specimens were prepared according to the American Society for Testing and Materials (ASTM) E1820 standard and were tested at room temperature. RESULTS: The results showed that the average total J-integral in transverse CT fracture specimens is 26% greater than that of longitudinal CT fracture specimens. For longitudinal-fractured and transverse-fractured cortical specimens, the energy used in the elastic deformation was found to be 2.8–3 times less than the energy used in the plastic deformation. CONCLUSION: The findings indicate that the overall fracture toughness measured using the J-integral is significantly higher than the toughness calculated by the stress intensity factor. Therefore, J-integral should be employ to compute the fracture toughness of cortical bone.

Age-related changes in cortical bone in men: metacarpal bone mass measurement study

2000 ◽  
Vol 5 (1) ◽  
pp. 4-9 ◽  
Author(s):  
Jun Iwamoto ◽  
Tsuyoshi Takeda ◽  
Shoichi Ichimura ◽  
Yasunori Tsukimura ◽  
Yoshiaki Toyama
Keyword(s):  
Bone Mass ◽  
Cortical Bone ◽  
Mass Measurement ◽  
Metacarpal Bone ◽  
Measurement Study ◽  
Bone Mass Measurement ◽  
Age Related ◽  
Age Related Changes
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