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Sample records for cortical bone strain

  1. Analysis of creep strain during tensile fatigue of cortical bone.

    PubMed

    Cotton, John R; Zioupos, Peter; Winwood, Keith; Taylor, Mark

    2003-07-01

    During fatigue tests of cortical bone specimens, at the unload portion of the cycle (zero stress) non-zero strains occur and progressively accumulate as the test progresses. This non-zero strain is hypothesised to be mostly, if not entirely, describable as creep. This work examines the rate of accumulation of this strain and quantifies its stress dependency. A published relationship determined from creep tests of cortical bone (Journal of Biomechanics 21 (1988) 623) is combined with knowledge of the stress history during fatigue testing to derive an expression for the amount of creep strain in fatigue tests. Fatigue tests on 31 bone samples from four individuals showed strong correlations between creep strain rate and both stress and "normalised stress" (sigma/E) during tensile fatigue testing (0-T). Combined results were good (r(2)=0.78) and differences between the various individuals, in particular, vanished when effects were examined against normalised stress values. Constants of the regression showed equivalence to constants derived in creep tests. The universality of the results, with respect to four different individuals of both sexes, shows great promise for use in computational models of fatigue in bone structures.

  2. Variations in mineralization affect the stress and strain distributions in cortical and trabecular bone.

    PubMed

    van Ruijven, L J; Mulder, L; van Eijden, T M G J

    2007-01-01

    The mechanical properties of bone depend largely on its degree and distribution of mineralization. The present study analyzes the effect of an inhomogeneous distribution of mineralization on the stress and strain distributions in the human mandibular condyle during static clenching. A condyle was scanned with a micro-CT scanner to create a finite element model. For every voxel the degree of mineralization (DMB) was determined from the micro-CT scan. The Young's moduli of the elements were calculated from the DMB using constant, linear, and cubic relations, respectively. Stresses, strains, and displacements in cortical and trabecular bone, as well as the condylar deformation (extension along the antero-posterion axis) and compliance were compared. Over 90% of the bone mineral was located in the cortical bone. The DMB showed large variations in both cortical bone (mean: 884, SD: 111 mg/cm(3)) and trabecular bone (mean: 738, SD: 101 mg/cm(3)). Variations of the stresses and the strains were small in cortical bone, but large in trabecular bone. In the cortical bone an inhomogeneous mineral distribution increased the stresses and the strains. In the trabecular bone, however, it decreased the stresses and increased the strains. Furthermore, the condylar compliance remained relatively constant, but the condylar deformation doubled. It was concluded that neglect of the inhomogeneity of the mineral distribution results in a large underestimation of the stresses and strains of possibly more than 50%. The stiffness of trabecular bone strongly influences the condylar deformation. Vice versa, the condylar deformation largely determines the magnitude of the strains in the trabecular bone.

  3. Effects of gamma radiation sterilization and strain rate on compressive behavior of equine cortical bone.

    PubMed

    Tüfekci, Kenan; Kayacan, Ramazan; Kurbanoğlu, Cahit

    2014-06-01

    Gamma radiation has been widely used for sterilization of bone allograft. However, sterilization by gamma radiation damages the material properties of bone which is a major clinical concern since bone allograft is used in load bearing applications. While the degree of this damage is well investigated for quasi-static and cyclic loading conditions, there does not appear any information on mechanical behavior of gamma-irradiated cortical bone at high speed loading conditions. In this study, the effects of gamma irradiation on high strain rate compressive behavior of equine cortical bone were investigated using a Split Hopkinson Pressure Bar (SHPB). Quasi-static compression testing was also performed. Equine cortical bone tissue from 8year old retired racehorses was divided into two groups: non-irradiated and gamma-irradiated at 30kGy. Quasi-static and high strain rate compression tests were performed at average strain rates of 0.0045/s and 725/s, respectively. Agreeing with previous results on the embrittlement of cortical bone when gamma-irradiated, the quasi-static results showed that gamma-irradiation significantly decreased ultimate strength (9%), ultimate strain (27%) and toughness (41%), while not having significant effect on modulus of elasticity, yield strain and resilience. More importantly, contrary to what is typically observed in quasi-static loading, the gamma-irradiated bone under high speed loading showed significantly higher modulus of elasticity (45%), ultimate strength (24%) and toughness (26%) than those of non-irradiated bone, although the failure was at a similar strain. Under high speed loading, the mechanical properties of bone allografts were not degraded by irradiation, in contrast to the degradation measured in this and prior studies under quasi-static loading. This result calls into question the assumption that bone allograft is always degraded by gamma irradiation, regardless of loading conditions. However, it needs further investigation

  4. Influence of strain rate on the mechanical behaviour in tension of bovine cortical bone

    NASA Astrophysics Data System (ADS)

    Latella, C.; Dotta, M.; Forni, D.; Tesio, N.; Cadoni, E.

    2015-09-01

    The mechanical behaviour of bones when subjected to tension loading in a wide range of strain-rates is fundamental to develop protection systems. The paper presents the preliminary tests on the tensile behaviour of bovine cortical bone at medium and high strain rates. Two special apparatus, both installed at the DynaMat Laboratory of the University of Applied Sciences of Southern Switzerland, a Hydro-Pneumatic Machine and a Modified Hopkinson Bar respectively for medium and high strain-rate tests have been used. Flat shape specimens (having 10 mm of gauge length, 5 mm width and 3 mm thickness) have been obtained from 15 bovine femurs with the same age. The paper describes the preparation techniques of the samples and the experimental results obtained. The bovine cortical bone shown a quite important strain rate dependency.

  5. Characterizing gait induced normal strains in a murine tibia cortical bone defect model.

    PubMed

    Prasad, Jitendra; Wiater, Brett P; Nork, Sean E; Bain, Steven D; Gross, Ted S

    2010-10-19

    The critical role that mechanical stimuli serve in mediating bone repair is recognized but incompletely understood. Further, previous attempts to understand this role have utilized application of externally applied mechanical loads to study the tissue's response. In this project, we have therefore endeavored to capitalize on bone's own consistently diverse loading environment to develop a novel model that would enable assessment of the influence of physiologically engendered mechanical stimuli on cortical defect repair. We used an inverse dynamics approach with finite element analysis (FEA) to first quantify normal strain distributions generated in mouse tibia during locomotion. The strain environment of the tibia, as previously reported for other long bones, was found to arise primarily due to bending and was consistent in orientation through the stance phase of gait. Based on these data, we identified three regions within a transverse cross-section of the mid-diaphysis as uniform locations of either peak tension, peak compression, or the neutral axis of bending (i.e. minimal strain magnitude). We then used FEA to quantify the altered strain environment that would be produced by a 0.6mm diameter cylindrical cortical bone defect at each diaphyseal site and, in an in situ study confirmed our ability to accurately place defects at the desired diaphyseal locations. The resulting model will enable the exploration of cortical bone healing within the context of physiologically engendered mechanical strain. Copyright © 2010 Elsevier Ltd. All rights reserved.

  6. Hopkinson bar techniques for the intermediate strain rate testing of bovine cortical bone.

    PubMed

    Cloete, T J; Paul, G; Ismail, E B

    2014-05-13

    Detailed knowledge of the dynamic viscoelastic properties of bone is required to understand the mechanisms of macroscopic bone fracture in humans, and other terrestrial mammals, during impact loading events (e.g. falls, vehicle accidents, etc.). While the dynamic response of bone has been studied for several decades, high-quality data remain limited, and it is only within the last decade that techniques for conducting dynamic compression tests on bone at near-constant strain rates have been developed. Furthermore, there appears to be a lack of published bone data in the intermediate strain rate (ISR) range (i.e. 1-100 s(-1)), which represents a regime in which many dynamic bone fractures occur. In this paper, preliminary results for the dynamic compression of bovine cortical bone in the ISR regime are presented. The results are obtained using two Hopkinson-bar-related techniques, namely the conventional split Hopkinson bar arrangement incorporating a novel cone-in-tube striker design, and the recently developed wedge bar apparatus. The experimental results show a rapid transition in the strain rate sensitive behaviour of bovine cortical bone in the ISR range. Finally, a new viscoelastic model is proposed that captures the observed transition behaviour.

  7. Hopkinson bar techniques for the intermediate strain rate testing of bovine cortical bone

    PubMed Central

    Cloete, T. J.; Paul, G.; Ismail, E. B.

    2014-01-01

    Detailed knowledge of the dynamic viscoelastic properties of bone is required to understand the mechanisms of macroscopic bone fracture in humans, and other terrestrial mammals, during impact loading events (e.g. falls, vehicle accidents, etc.). While the dynamic response of bone has been studied for several decades, high-quality data remain limited, and it is only within the last decade that techniques for conducting dynamic compression tests on bone at near-constant strain rates have been developed. Furthermore, there appears to be a lack of published bone data in the intermediate strain rate (ISR) range (i.e. 1–100 s−1), which represents a regime in which many dynamic bone fractures occur. In this paper, preliminary results for the dynamic compression of bovine cortical bone in the ISR regime are presented. The results are obtained using two Hopkinson-bar-related techniques, namely the conventional split Hopkinson bar arrangement incorporating a novel cone-in-tube striker design, and the recently developed wedge bar apparatus. The experimental results show a rapid transition in the strain rate sensitive behaviour of bovine cortical bone in the ISR range. Finally, a new viscoelastic model is proposed that captures the observed transition behaviour. PMID:24711493

  8. In vitro non-enzymatic ribation reduces post-yield strain accommodation in cortical bone.

    PubMed

    Willett, Thomas L; Sutty, Sibi; Gaspar, Anne; Avery, Nick; Grynpas, Marc

    2013-02-01

    Non-enzymatic glycation (NEG) and advanced glycation endproducts (AGEs) may contribute to bone fragility in various diseases, ageing, and other conditions by modifying bone collagen and causing degraded mechanical properties. In this study, we sought to further understand how collagen modification in an in vitro non-enzymatic ribation model leads to loss of cortical bone toughness. Previous in vitro studies using non-enzymatic ribation reported loss of ductility in the cortical bone. Increased crosslinking is most commonly blamed for these changes; however, some studies report positive correlations between measures of total collagen crosslinking and work-to-fracture/toughness measurements whilst correlations between general NEG and measures of ductility are often negative. Fifteen bone beam triplets were cut from bovine metatarsi. Each provided one native non-incubated control, one incubated control and one ribated specimen. Incubation involved simulated body fluid±ribose for fourteen days at 37°C. Pentosidine and pyridinoline crosslinks were measured using HPLC. Three-point bending tests quantified mechanical properties. Fracture surfaces were examined using scanning electron microscopy. The effects of ribation on bone collagen molecular stability and intermolecular connectivity were investigated using differential scanning calorimetry and hydrothermal isometric tension testing. Ribation caused increased non-enzymatic collagen modification and pentosidine content (16mmol/mol collagen) and inferior post-yield mechanical behaviour, especially post-yield strain and flexural toughness. Fracture surfaces were smoother with less collagen fibril deformation or tearing than observed in controls. In the ribated group only, pentosidine content and thermomechanical measures of crosslinking were positively correlated with measures of strain accommodation and energy absorption before failure. Non-enzymatic ribation and the resulting modifications reduce cortical bone pseudo

  9. The effect of strain rate on fracture toughness of human cortical bone: a finite element study.

    PubMed

    Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak

    2011-10-01

    Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive finite element modeling was employed to evaluate the effect of strain rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing strain rate (range: 0.08-18 s(-1)). In addition, the effect of porosity in combination with strain rate was assessed using three-dimensional models of micro-computed tomography-based compact tension specimens. The simulation results showed that bone's resistance against the propagation of a crack decreased sharply with increase in strain rates up to 1 s(-1) and attained an almost constant value for strain rates larger than 1 s(-1). On the other hand, initiation fracture toughness exhibited a more gradual decrease throughout the strain rates. There was a significant positive correlation between the experimentally measured number of microcracks and the fracture toughness found in the simulations. Furthermore, the simulation results showed that the amount of porosity did not affect the way initiation fracture toughness decreased with increasing strain rates, whereas it exacerbated the same strain rate effect when propagation fracture toughness was considered. These results suggest that strain rates associated with falls lead to a dramatic reduction in bone's resistance against crack propagation. The compromised fracture resistance of bone at loads exceeding normal activities indicates a sharp reduction and/or absence of toughening mechanisms in bone during high strain conditions associated with traumatic fracture.

  10. THE EFFECT OF STRAIN RATE ON FRACTURE TOUGHNESS OF HUMAN CORTICAL BONE: A FINITE ELEMENT STUDY

    PubMed Central

    Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak

    2011-01-01

    Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive finite element modeling was employed to evaluate the effect of strain rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing strain rate (range: 0.08 to 18 s−1). In addition, the effect of porosity in combination with strain rate was assessed using three-dimensional models of microcomputed tomography-based compact tension specimens. The simulation results showed that bone’s resistance against the propagation of fracture decreased sharply with increase in strain rates up to 1 s−1 and attained an almost constant value for strain rates larger than 1 s−1. On the other hand, initiation fracture toughness exhibited a more gradual decrease throughout the strain rates. There was a significant positive correlation between the experimentally measured number of microcracks and the fracture toughness found in the simulations. Furthermore, the simulation results showed that the amount of porosity did not affect the way initiation fracture toughness decreased with increasing strain rates, whereas it exacerbated the same strain rate effect when propagation fracture toughness was considered. These results suggest that strain rates associated with falls lead to a dramatic reduction in bone’s resistance against crack propagation. The compromised fracture resistance of bone at loads exceeding normal activities indicates a sharp reduction and/or absence of toughening mechanisms in bone during high strain conditions associated with traumatic fracture. PMID:21783112

  11. The effects of bone density and crestal cortical bone thickness on micromotion and peri-implant bone strain distribution in an immediately loaded implant: a nonlinear finite element analysis

    PubMed Central

    2016-01-01

    Purpose This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions. Methods A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment. Results The maximum extent of micromotion was approximately 100 μm in the low-density cancellous bone models, whereas it was under 30 μm in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness. Conclusions Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading. PMID:27382504

  12. Mechanical strain, induced noninvasively in the high-frequency domain, is anabolic to cancellous bone, but not cortical bone.

    PubMed

    Rubin, C; Turner, A S; Mallinckrodt, C; Jerome, C; McLeod, K; Bain, S

    2002-03-01

    Departing from the premise that it is the large-amplitude signals inherent to intense functional activity that define bone morphology, we propose that it is the far lower magnitude, high-frequency mechanical signals that continually barrage the skeleton during longer term activities such as standing, which regulate skeletal architecture. To examine this hypothesis, we proposed that brief exposure to slight elevations in these endogenous mechanical signals would suffice to increase bone mass in those bones subject to the stimulus. This was tested by exposing the hind limbs of adult female sheep (n = 9) to 20 min/day of low-level (0.3g), high-frequency (30 Hz) mechanical signals, sufficient to induce a peak of approximately 5 microstrain (micro epsilon) in the tibia. Following euthanasia, peripheral quantitative computed tomography (pQCT) was used to segregate the cortical shell from the trabecular envelope of the proximal femur, revealing a 34.2% increase in bone density in the experimental animals as compared with controls (p = 0.01). Histomorphometric examination of the femur supported these density measurements, with bone volume per total volume increasing by 32% (p = 0.04). This density increase was achieved by two separate strategies: trabecular spacing decreased by 36.1% (p = 0.02), whereas trabecular number increased by 45.6% (p = 0.01), indicating the formation of cancellous bone de novo. There were no significant differences in the radii of animals subject to the stimulus, indicating that the adaptive response was local rather than systemic. The anabolic potential of the signal was evident only in trabecular bone, and there were no differences, as measured by any assay, in the cortical bone. These data suggest that subtle mechanical signals generated during predominant activities such as posture may be potent determinants of skeletal morphology. Given that these strain levels are three orders of magnitude below strains that can damage bone tissue, we

  13. Development of a strain rate dependent material model of human cortical bone for computer-aided reconstruction of injury mechanisms.

    PubMed

    Asgharpour, Zahra; Zioupos, Peter; Graw, Matthias; Peldschus, Steffen

    2014-03-01

    Computer-aided methods such as finite-element simulation offer a great potential in the forensic reconstruction of injury mechanisms. Numerous studies have been performed on understanding and analysing the mechanical properties of bone and the mechanism of its fracture. Determination of the mechanical properties of bones is made on the same basis used for other structural materials. The mechanical behaviour of bones is affected by the mechanical properties of the bone material, the geometry, the loading direction and mode and of course the loading rate. Strain rate dependency of mechanical properties of cortical bone has been well demonstrated in literature studies, but as many of these were performed on animal bones and at non-physiological strain rates it is questionable how these will apply in the human situations. High strain-rates dominate in a lot of forensic applications in automotive crashes and assault scenarios. There is an overwhelming need to a model which can describe the complex behaviour of bone at lower strain rates as well as higher ones. Some attempts have been made to model the viscoelastic and viscoplastic properties of the bone at high strain rates using constitutive mathematical models with little demonstrated success. The main objective of the present study is to model the rate dependent behaviour of the bones based on experimental data. An isotropic material model of human cortical bone with strain rate dependency effects is implemented using the LS-DYNA material library. We employed a human finite element model called THUMS (Total Human Model for Safety), developed by Toyota R&D Labs and the Wayne State University, USA. The finite element model of the human femur is extracted from the THUMS model. Different methods have been employed to develop a strain rate dependent material model for the femur bone. Results of one the recent experimental studies on human femur have been employed to obtain the numerical model for cortical femur. A

  14. Variation of the mineral density in cortical bone may serve to keep strain amplitudes within a physiological range.

    PubMed

    de Jong, W C; van Ruijven, L J; Brugman, P; Langenbach, G E J

    2013-08-01

    Within-bone variation in mineral density could be functional. A heterogeneous mineral-density distribution might serve to maintain habitual amplitudes of bone strain within a non-harmful, i.e., physiological range. Regions of a bone that would be strained the most on the basis of architecture alone might have a higher mineral density to make them more stiff and resistant to strain. We hypothesised that the cortical bone of the rabbit mandible contains such a functional distribution of mineral density. We thereby expected similar mineral-density patterns in the mandibles of different individuals due to the shared masticatory function. Secondly, we hypothesised that the highest mineral densities occur in mandibular regions predicted to be exposed to the largest amplitudes of strain-when taking into account bone architecture only. Mineral-density maps of the cortical bone of rabbit mandibles were obtained using micro-computed tomography (μCT). The μCT scans of two rabbits were converted into finite-element models (FEMs). To predict mandibular deformation during biting, these models were loaded by muscle forces and reaction forces. The forces acted on the condyles and on either the incisal or molar bite point. The FEMs were assigned a homogeneous material stiffness to calculate the strain amplitudes that would occur when only the architecture of the mandibular bone would be of influence. We found the cortical bone-mineral density patterns to be similar in all six mandibles. The mineral density of the corpus was higher than that of the ramus. A second consistent feature of the mandibular mineral-density distribution was that the medial ridge of the temporal-muscle insertion groove contained more mineral than its surrounding regions. The strain amplitudes calculated with the FEMs were variable and did not feature clear corpo-ramal differences. However, specific mandibular bone sites calculated to be exposed to the largest amplitudes of strain, including the medial

  15. Microcracking damage and the fracture process in relation to strain rate in human cortical bone tensile failure.

    PubMed

    Zioupos, Peter; Hansen, Ulrich; Currey, John D

    2008-10-20

    It is difficult to define the 'physiological' mechanical properties of bone. Traumatic failures in-vivo are more likely to be orders of magnitude faster than the quasistatic tests usually employed in-vitro. We have reported recently [Hansen, U., Zioupos, P., Simpson, R., Currey, J.D., Hynd, D., 2008. The effect of strain rate on the mechanical properties of human cortical bone. Journal of Biomechanical Engineering/Transactions of the ASME 130, 011011-1-8] results from tests on specimens of human femoral cortical bone loaded in tension at strain rates (epsilon ) ranging from low (0.08s(-1)) to high (18s(-1)). Across this strain rate range the modulus of elasticity generally increased, stress at yield and failure and strain at failure decreased for rates higher than 1s(-1), while strain at yield was invariant for most strain rates and only decreased at rates higher than 10s(-1). The results showed that strain rate has a stronger effect on post-yield deformation than on initiation of macroscopic yielding. In general, specimens loaded at high strain rates were brittle, while those loaded at low strain rates were much tougher. Here, a post-test examination of the microcracking damage reveals that microcracking was inversely related to the strain rate. Specimens loaded at low strain rates showed considerable post-yield strain and also much more microcracking. Partial correlation and regression analysis suggested that the development of post-yield strain was a function of the amount of microcracking incurred (the cause), rather than being a direct result of the strain rate (the excitation). Presumably low strain rates allow time for microcracking to develop, which increases the compliance of the specimen, making them tougher. This behaviour confirms a more general rule that the degree to which bone is brittle or tough depends on the amount of microcracking damage it is able to sustain. More importantly, the key to bone toughness is its ability to avoid a ductile

  16. Interactive effects of nutrition, environment, and rat-strain on cortical and vertebral bone geometry and biomechanics

    NASA Technical Reports Server (NTRS)

    Zernicke, R. F.; Li, K.-C.; Salem, G. J.; Vailas, A. C.; Grindeland, R. E.

    1990-01-01

    An investigation was conducted to generate comparative data on the sensitivity of cortical- and vertebral-bone adaptations in two different rat strains maintained at conditions typical for spaceborne experiments conducted by U.S.A. and USSR. The effects of cage environment, diet, and rat-strain on the cortical (humerus) and vertebral (T7) bones of male Taconic-Sprague-Dawley and Czechoslovakian-Wistar rats were investigated using different flight-simulation cages (one rat/cage for U.S.A.; ten rats/cage for USSR conditions) and fed either U.S.A. or USSR diet. The results showed significant effects of these factors on the humeral and vertebral geometry and mechanical properties, as well as significant interactive effects on the mechanical properties of the humerus.

  17. Strain-rate stiffening of cortical bone: observations and implications from nanoindentation experiments

    NASA Astrophysics Data System (ADS)

    Maruyama, Noriko; Shibata, Yo; Wurihan, Affb; Swain, Michael V.; Kataoka, Yu; Takiguchi, Yuichi; Yamada, Atsushi; Maki, Koutaro; Miyazaki, Takashi

    2014-11-01

    While bone mineralization is considered to be responsible for its stiffness, bone durability partially associated with the time-dependent viscoelasticity of matrix proteins is still poorly elucidated. Here we demonstrate a novel mechanism of highly mineralized bone durability almost independent of inherent viscoelastic behaviour along with a protocol for measuring the mechanical properties of mineralized tissues. Strain-rate nanoindentation tests showed substantial stiffening of the highly mineralized calvarial bone, whereas large creep or stress relaxation was observed during constant load or displacement tests, respectively. Based on the lower viscoelasticity of the highly mineralized structure, such large time-dependent response appears to be associated with nanoscale dimensional recovery, rather than viscoelastic behaviour, implying the inverse namely strain-rate dependent dilatant behaviour. This dilatant expansion increased the indenter penetration resistance into the surface, enhancing instantaneous stiffness. The associated stiffening and higher effective elastic modulus were highly strain-rate dependent and more readily observed in more highly mineralized tissues such as the calvarial bone. Such strain-rate stiffening and consequent dimensional recovery may be vital responses of bone tissues against excessive deformation to maintain tissue integrity.While bone mineralization is considered to be responsible for its stiffness, bone durability partially associated with the time-dependent viscoelasticity of matrix proteins is still poorly elucidated. Here we demonstrate a novel mechanism of highly mineralized bone durability almost independent of inherent viscoelastic behaviour along with a protocol for measuring the mechanical properties of mineralized tissues. Strain-rate nanoindentation tests showed substantial stiffening of the highly mineralized calvarial bone, whereas large creep or stress relaxation was observed during constant load or displacement

  18. Measurement of strain distribution in cortical bone around miniscrew implants used for orthodontic anchorage using digital speckle pattern interferometry

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Agarwal, Rupali; Bhutani, Ravi; Shakher, Chandra

    2016-05-01

    An application of digital speckle pattern interferometry (DSPI) for the measurement of deformations and strain-field distributions developed in cortical bone around orthodontic miniscrew implants inserted into the human maxilla is presented. The purpose of this study is to measure and compare the strain distribution in cortical bone/miniscrew interface of human maxilla around miniscrew implants of different diameters, different implant lengths, and implants of different commercially available companies. The technique is also used to measure tilt/rotation of canine caused due to the application of retraction springs. The proposed technique has high sensitivity and enables the observation of deformation/strain distribution. In DSPI, two specklegrams are recorded corresponding to pre- and postloading of the retraction spring. The DSPI fringe pattern is observed by subtracting these two specklegrams. Optical phase was extracted using Riesz transform and the monogenic signal from a single DSPI fringe pattern. The obtained phase is used to calculate the parameters of interest such as displacement/deformation and strain/stress. The experiment was conducted on a dry human skull fulfilling the criteria of intact dental arches and all teeth present. Eight different miniscrew implants were loaded with an insertion angulation of 45 deg in the inter-radicular region of the maxillary second premolar and molar region. The loading of miniscrew implants was done with force level (150 gf) by nickel-titanium closed-coil springs (9 mm). The obtained results from DSPI reveal that implant diameter and implant length affect the displacement and strain distribution in cortical bone layer surrounding the miniscrew implant.

  19. Relationships between in vivo microdamage and the remarkable regional material and strain heterogeneity of cortical bone of adult deer, elk, sheep and horse calcanei.

    PubMed

    Skedros, John G; Sybrowsky, Christian L; Anderson, Wm Erick; Chow, Frank

    2011-12-01

    Natural loading of the calcanei of deer, elk, sheep and horses produces marked regional differences in prevalent/predominant strain modes: compression in the dorsal cortex, shear in medial-lateral cortices, and tension/shear in the plantar cortex. This consistent non-uniform strain distribution is useful for investigating mechanisms that mediate the development of the remarkable regional material variations of these bones (e.g. collagen orientation, mineralization, remodeling rates and secondary osteon morphotypes, size and population density). Regional differences in strain-mode-specific microdamage prevalence and/or morphology might evoke and sustain the remodeling that produces this material heterogeneity in accordance with local strain characteristics. Adult calcanei from 11 animals of each species (deer, elk, sheep and horses) were transversely sectioned and examined using light and confocal microscopy. With light microscopy, 20 linear microcracks were identified (deer: 10; elk: six; horse: four; sheep: none), and with confocal microscopy substantially more microdamage with typically non-linear morphology was identified (deer: 45; elk: 24; horse: 15; sheep: none). No clear regional patterns of strain-mode-specific microdamage were found in the three species with microdamage. In these species, the highest overall concentrations occurred in the plantar cortex. This might reflect increased susceptibility of microdamage in habitual tension/shear. Absence of detectable microdamage in sheep calcanei may represent the (presumably) relatively greater physical activity of deer, elk and horses. Absence of differences in microdamage prevalence/morphology between dorsal, medial and lateral cortices of these bones, and the general absence of spatial patterns of strain-mode-specific microdamage, might reflect the prior emergence of non-uniform osteon-mediated adaptations that reduce deleterious concentrations of microdamage by the adult stage of bone development.

  20. Relationships between in vivo microdamage and the remarkable regional material and strain heterogeneity of cortical bone of adult deer, elk, sheep and horse calcanei

    PubMed Central

    Skedros, John G; Sybrowsky, Christian L; Anderson, Wm Erick; Chow, Frank

    2011-01-01

    Natural loading of the calcanei of deer, elk, sheep and horses produces marked regional differences in prevalent/predominant strain modes: compression in the dorsal cortex, shear in medial–lateral cortices, and tension/shear in the plantar cortex. This consistent non-uniform strain distribution is useful for investigating mechanisms that mediate the development of the remarkable regional material variations of these bones (e.g. collagen orientation, mineralization, remodeling rates and secondary osteon morphotypes, size and population density). Regional differences in strain-mode-specific microdamage prevalence and/or morphology might evoke and sustain the remodeling that produces this material heterogeneity in accordance with local strain characteristics. Adult calcanei from 11 animals of each species (deer, elk, sheep and horses) were transversely sectioned and examined using light and confocal microscopy. With light microscopy, 20 linear microcracks were identified (deer: 10; elk: six; horse: four; sheep: none), and with confocal microscopy substantially more microdamage with typically non-linear morphology was identified (deer: 45; elk: 24; horse: 15; sheep: none). No clear regional patterns of strain-mode-specific microdamage were found in the three species with microdamage. In these species, the highest overall concentrations occurred in the plantar cortex. This might reflect increased susceptibility of microdamage in habitual tension/shear. Absence of detectable microdamage in sheep calcanei may represent the (presumably) relatively greater physical activity of deer, elk and horses. Absence of differences in microdamage prevalence/morphology between dorsal, medial and lateral cortices of these bones, and the general absence of spatial patterns of strain-mode-specific microdamage, might reflect the prior emergence of non-uniform osteon-mediated adaptations that reduce deleterious concentrations of microdamage by the adult stage of bone development. PMID

  1. Short-term Low-strain Vibration Enhances Chemo-transport Yet Does Not Stimulate Osteogenic Gene Expression or Cortical Bone Formation in Adult Mice

    PubMed Central

    Kotiya, Akhilesh A.; Bayly, Philip V.; Silva, Matthew J.

    2010-01-01

    Development of low-magnitude mechanical stimulation (LMMS) based treatment strategies for a variety of orthopaedic issues requires better understanding of mechano-transduction and bone adaptation. Our overall goal was to study the tissue and molecular level changes in cortical bone in response to low-strain vibration (LSV: 70 Hz, 0.5 g, 300 με) and compare these to changes in response to a known anabolic stimulus: high-strain compression (HSC: rest inserted loading, 1000 με). Adult (6–7 month) C57BL/6 mice were used for the study and non-invasive axial compression of the tibia was used as a loading model. We first studied bone adaptation at the tibial mid-diaphysis, using dynamic histomorphometry, in response to daily loading of 15 min LSV or 60 cycles HSC for 5 consecutive days. We found that bone formation rate and mineral apposition rate were significantly increased in response to HSC but not LSV. The second aim was to compare chemo-transport in response to 5 min of LSV versus 5 min (30 cycles) of HSC. Chemo-transport increased significantly in response to both loading stimuli, particularly in the medial and the lateral quadrants of the cross section. Finally, we evaluated the expression of genes related to mechano-responsiveness, osteoblast differentiation, and matrix mineralization in tibias subjected to 15 min LSV or 60 cycles HSC for 1 day (4-hour time point) or 4 consecutive days (4-day time point). The expression level of most of the genes remained unchanged in response to LSV at both time points. In contrast, the expression level of all the genes changed significantly in response to HSC at the 4-hour time point. We conclude that short-term, low-strain vibration results in increased chemo-transport, yet does not stimulate an increase in mechano-responsive or osteogenic gene expression, and cortical bone formation in tibias of adult mice. PMID:20937421

  2. Advances in the fracture mechanics of cortical bone.

    PubMed

    Bonfield, W

    1987-01-01

    As cortical bone is a semi-brittle solid, its fracture is dependent not only on the magnitude of the applied stress, but also on the nature of any intrinsic or introduced cracks. Consequently a variety of fracture mechanics techniques have been utilised to evaluate the fracture toughness of cortical bone, including the single edge notched, centre notched cylindrical and compact tension methods, and values have been established for the critical stress intensity factor (Kc) and the critical strain energy release rate (Gc). The Kc and Gc values obtained depend on the orientation of the cortical bone, as well as on bone density, the velocity of crack propagation and specimen geometry. The significance of these fracture mechanics parameters for cortical bone is critically reviewed.

  3. Probiotics protect mice from ovariectomy-induced cortical bone loss.

    PubMed

    Ohlsson, Claes; Engdahl, Cecilia; Fåk, Frida; Andersson, Annica; Windahl, Sara H; Farman, Helen H; Movérare-Skrtic, Sofia; Islander, Ulrika; Sjögren, Klara

    2014-01-01

    The gut microbiota (GM) modulates the hosts metabolism and immune system. Probiotic bacteria are defined as live microorganisms which when administered in adequate amounts confer a health benefit on the host and can alter the composition of the GM. Germ-free mice have increased bone mass associated with reduced bone resorption indicating that the GM also regulates bone mass. Ovariectomy (ovx) results in bone loss associated with altered immune status. The purpose of this study was to determine if probiotic treatment protects mice from ovx-induced bone loss. Mice were treated with either a single Lactobacillus (L) strain, L. paracasei DSM13434 (L. para) or a mixture of three strains, L. paracasei DSM13434, L. plantarum DSM 15312 and DSM 15313 (L. mix) given in the drinking water during 6 weeks, starting two weeks before ovx. Both the L. para and the L. mix treatment protected mice from ovx-induced cortical bone loss and bone resorption. Cortical bone mineral content was higher in both L. para and L. mix treated ovx mice compared to vehicle (veh) treated ovx mice. Serum levels of the resorption marker C-terminal telopeptides and the urinary fractional excretion of calcium were increased by ovx in the veh treated but not in the L. para or the L. mix treated mice. Probiotic treatment reduced the expression of the two inflammatory cytokines, TNFα and IL-1β, and increased the expression of OPG, a potent inhibitor of osteoclastogenesis, in cortical bone of ovx mice. In addition, ovx decreased the frequency of regulatory T cells in bone marrow of veh treated but not probiotic treated mice. In conclusion, treatment with L. para or the L. mix prevents ovx-induced cortical bone loss. Our findings indicate that these probiotic treatments alter the immune status in bone resulting in attenuated bone resorption in ovx mice.

  4. Probiotics Protect Mice from Ovariectomy-Induced Cortical Bone Loss

    PubMed Central

    Ohlsson, Claes; Engdahl, Cecilia; Fåk, Frida; Andersson, Annica; Windahl, Sara H.; Farman, Helen H.; Movérare-Skrtic, Sofia; Islander, Ulrika; Sjögren, Klara

    2014-01-01

    The gut microbiota (GM) modulates the hosts metabolism and immune system. Probiotic bacteria are defined as live microorganisms which when administered in adequate amounts confer a health benefit on the host and can alter the composition of the GM. Germ-free mice have increased bone mass associated with reduced bone resorption indicating that the GM also regulates bone mass. Ovariectomy (ovx) results in bone loss associated with altered immune status. The purpose of this study was to determine if probiotic treatment protects mice from ovx-induced bone loss. Mice were treated with either a single Lactobacillus (L) strain, L. paracasei DSM13434 (L. para) or a mixture of three strains, L. paracasei DSM13434, L. plantarum DSM 15312 and DSM 15313 (L. mix) given in the drinking water during 6 weeks, starting two weeks before ovx. Both the L. para and the L. mix treatment protected mice from ovx-induced cortical bone loss and bone resorption. Cortical bone mineral content was higher in both L. para and L. mix treated ovx mice compared to vehicle (veh) treated ovx mice. Serum levels of the resorption marker C-terminal telopeptides and the urinary fractional excretion of calcium were increased by ovx in the veh treated but not in the L. para or the L. mix treated mice. Probiotic treatment reduced the expression of the two inflammatory cytokines, TNFα and IL-1β, and increased the expression of OPG, a potent inhibitor of osteoclastogenesis, in cortical bone of ovx mice. In addition, ovx decreased the frequency of regulatory T cells in bone marrow of veh treated but not probiotic treated mice. In conclusion, treatment with L. para or the L. mix prevents ovx-induced cortical bone loss. Our findings indicate that these probiotic treatments alter the immune status in bone resulting in attenuated bone resorption in ovx mice. PMID:24637895

  5. Quantitative radiology: radiogrammetry of cortical bone.

    PubMed

    Dequeker, J

    1976-11-01

    Based on personal experience and data in the literature, an overview is given of radiogrammetry of cortical bone of the second metacarpal. There is a within- and between-observer error which amounts respectively to 1.2 and 1.5% for the outer diameter and 4.8 and 6.4% for the inner diameter. The systematic + or-- trend between observers indicates that one observer working according to certain defined rules obtains the most reliable results. There is a large variability in amount of bone within one age and sex group which is partly due to skeletal size differences, are insufficient since skeletal size differences still exist. The variability is reduced when the data are divided into strata of skeletal size. Since cortical area shows the best correlation with outer diameter within each age group and since cortical area represents best the ash content of the bones the values of this index are most suited to be grouped according to outer diameter. In differentiating pathological from physiological bone loss this procedure is an improvement on the previously published indices of amount of bone. When comparing different populations this method has advantages since skeletal size differences are eliminated. Comparing seven populations it was found that populations living in the United States of America have more bone for a given skeletal size than populations in Europe or Nigeria. Bone loss with age is a general phenomenon but differences in rate of loss are observed between the sexes and between ethnic different populations. The decrease of bone mass is faster after the age of 50 years in woman than in men. Blacks living in the United States loose less bone with age than whites. Radiogrammetry of cortical bone in groups gives useful information on bond remodelling during ageing and in pathological conditions. At an individual level, however, it is difficult to evaluate changes on a short term basis with radiogrammetry. Radiogrammetry of cortical bone is a simple and

  6. Micromechanics of osteonal cortical bone fracture.

    PubMed

    Guo, X E; Liang, L C; Goldstein, S A

    1998-02-01

    Microcracks have been associated with age-related bone tissue fragility and fractures. The objective of this study was to develop a simple osteonal cortical bone model and apply linear elastic fracture mechanics theory to understand the micromechanics of the fracture process in osteonal cortical bone and its dependence on material properties. The linear fracture mechanics of our composite model of cortical bone, consisting of an osteon and interstitial bone tissue, was characterized in terms of a stress intensity factor (SIF) near the tip of a microcrack. The interaction between a microcrack and an osteon was studied for different types of osteons and various spacing between the crack and the osteon. The results of the analysis indicate that the fracture mechanics of osteonal cortical bone is dominated by the modulus ratio between the osteon and interstitial bone tissue: A soft osteon promotes microcrack propagation toward the osteon (and cement line) while a stiff one repels the microcrack from the osteon (and cement line). These findings suggest that newly formed, low-stiffness osteons may toughen cortical bone tissue by promoting crack propagation toward osteons. A relatively accurate empirical formula also was obtained to provide an easy estimation of the influence of osteons on the stress intensity factor.

  7. Elastic Properties of Chimpanzee Craniofacial Cortical Bone.

    PubMed

    Gharpure, Poorva; Kontogiorgos, Elias D; Opperman, Lynne A; Ross, Callum F; Strait, David S; Smith, Amanda; Pryor, Leslie C; Wang, Qian; Dechow, Paul C

    2016-12-01

    Relatively few assessments of cranial biomechanics formally take into account variation in the material properties of cranial cortical bone. Our aim was to characterize the elastic properties of chimpanzee craniofacial cortical bone and compare these to the elastic properties of dentate human craniofacial cortical bone. From seven cranial regions, 27 cylindrical samples were harvested from each of five chimpanzee crania. Assuming orthotropy, axes of maximum stiffness in the plane of the cortical plate were derived using modified equations of Hooke's law in a Mathcad program. Consistent orientations among individuals were observed in the zygomatic arch and alveolus. The density of cortical bone showed significant regional variation (P < 0.001). The elastic moduli demonstrated significant differences between sites, and a distinct pattern where E3  > E2  > E1 . Shear moduli were significantly different among regions (P < 0.001). The pattern by which chimpanzee cranial cortical bone varies in elastic properties resembled that seen in humans, perhaps suggesting that the elastic properties of craniofacial bone in fossil hominins can be estimated with at least some degree of confidence. Anat Rec, 299:1718-1733, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  8. Role of cortical bone in hip fracture.

    PubMed

    Reeve, Jonathan

    2017-01-01

    In this review, I consider the varied mechanisms in cortical bone that help preserve its integrity and how they deteriorate with aging. Aging affects cortical bone in two ways: extrinsically through its effects on the individual that modify its mechanical loading experience and 'milieu interieur'; and intrinsically through the prolonged cycle of remodelling and renewal extending to an estimated 20 years in the proximal femur. Healthy femoral cortex incorporates multiple mechanisms that help prevent fracture. These have been described at multiple length scales from the individual bone mineral crystal to the scale of the femur itself and appear to operate hierarchically. Each cortical bone fracture begins as a sub-microscopic crack that enlarges under mechanical load, for example, that imposed by a fall. In these conditions, a crack will enlarge explosively unless the cortical bone is intrinsically tough (the opposite of brittle). Toughness leads to microscopic crack deflection and bridging and may be increased by adequate regulation of both mineral crystal size and the heterogeneity of mineral and matrix phases. The role of osteocytes in optimising toughness is beginning to be worked out; but many osteocytes die in situ without triggering bone renewal over a 20-year cycle, with potential for increasing brittleness. Furthermore, the superolateral cortex of the proximal femur thins progressively during life, so increasing the risk of buckling during a fall. Besides preserving or increasing hip BMD, pharmaceutical treatments have class-specific effects on the toughness of cortical bone, although dietary and exercise-based interventions show early promise.

  9. Tensile behavior of cortical bone: dependence of organic matrix material properties on bone mineral content.

    PubMed

    Kotha, S P; Guzelsu, N

    2007-01-01

    A porous composite model is developed to analyze the tensile mechanical properties of cortical bone. The effects of microporosity (volksman's canals, osteocyte lacunae) on the mechanical properties of bone tissue are taken into account. A simple shear lag theory, wherein tensile loads are transferred between overlapped mineral platelets by shearing of the organic matrix, is used to model the reinforcement provided by mineral platelets. It is assumed that the organic matrix is elastic in tension and elastic-perfectly plastic in shear until it fails. When organic matrix shear stresses at the ends of mineral platelets reach their yield values, the stress-strain curve of bone tissue starts to deviate from linear behavior. This is referred as the microscopic yield point. At the point where the stress-strain behavior of bone shows a sharp curvature, the organic phase reaches its shear yield stress value over the entire platelet. This is referred as the macroscopic yield point. It is assumed that after macroscopic yield, mineral platelets cannot contribute to the load bearing capacity of bone and that the mechanical behavior of cortical bone tissue is determined by the organic phase only. Bone fails when the principal stress of the organic matrix is reached. By assuming that mechanical properties of the organic matrix are dependent on bone mineral content below the macroscopic yield point, the model is used to predict the entire tensile mechanical behavior of cortical bone for different mineral contents. It is found that decreased shear yield stresses and organic matrix elastic moduli are required to explain the mechanical behavior of bones with lowered mineral contents. Under these conditions, the predicted values (elastic modulus, 0.002 yield stress and strain, and ultimate stress and strain) are within 15% of experimental data.

  10. The myokine irisin increases cortical bone mass

    PubMed Central

    Colaianni, Graziana; Cuscito, Concetta; Mongelli, Teresa; Pignataro, Paolo; Buccoliero, Cinzia; Liu, Peng; Lu, Ping; Sartini, Loris; Di Comite, Mariasevera; Mori, Giorgio; Di Benedetto, Adriana; Brunetti, Giacomina; Yuen, Tony; Sun, Li; Reseland, Janne E.; Colucci, Silvia; New, Maria I.; Zaidi, Mone; Cinti, Saverio; Grano, Maria

    2015-01-01

    It is unclear how physical activity stimulates new bone synthesis. We explored whether irisin, a newly discovered myokine released upon physical activity, displays anabolic actions on the skeleton. Young male mice were injected with vehicle or recombinant irisin (r-irisin) at a low cumulative weekly dose of 100 µg kg−1. We observed significant increases in cortical bone mass and strength, notably in cortical tissue mineral density, periosteal circumference, polar moment of inertia, and bending strength. This anabolic action was mediated primarily through the stimulation of bone formation, but with parallel notable reductions in osteoclast numbers. The trabecular compartment of the same bones was spared, as were vertebrae from the same mice. Higher irisin doses (3,500 µg kg−1 per week) cause browning of adipose tissue; this was not seen with low-dose r-irisin. Expectedly, low-dose r-irisin modulated the skeletal genes, Opn and Sost, but not Ucp1 or Pparγ expression in white adipose tissue. In bone marrow stromal cell cultures, r-irisin rapidly phosphorylated Erk, and up-regulated Atf4, Runx2, Osx, Lrp5, β-catenin, Alp, and Col1a1; this is consistent with a direct receptor-mediated action to stimulate osteogenesis. We also noted that, although the irisin precursor Fndc5 was expressed abundantly in skeletal muscle, other sites, such as bone and brain, also expressed Fndc5, albeit at low levels. Furthermore, muscle fibers from r-irisin–injected mice displayed enhanced Fndc5 positivity, and irisin induced Fdnc5 mRNA expression in cultured myoblasts. Our data therefore highlight a previously unknown action of the myokine irisin, which may be the molecular entity responsible for muscle–bone connectivity. PMID:26374841

  11. Shear deformation and fracture of human cortical bone.

    PubMed

    Tang, Tengteng; Ebacher, Vincent; Cripton, Peter; Guy, Pierre; McKay, Heather; Wang, Rizhi

    2015-02-01

    Bone can be viewed as a nano-fibrous composite with complex hierarchical structures. Its deformation and fracture behaviors depend on both the local structure and the type of stress applied. In contrast to the extensive studies on bone fracture under compression and tension, there is a lack of knowledge on the fracture process under shear, a stress state often exists in hip fracture. This study investigated the mechanical behavior of human cortical bone under shear, with the focus on the relation between the fracture pattern and the microstructure. Iosipescu shear tests were performed on notched rectangular bar specimens made from human cortical bone. They were prepared at different angles (i.e. 0°, 30°, 60° and 90°) with respect to the long axis of the femoral shaft. The results showed that human cortical bone behaved as an anisotropic material under shear with the highest shear strength (~50MPa) obtained when shearing perpendicular to the Haversian systems or secondary osteons. Digital image correlation (DIC) analysis found that shear strain concentration bands had a close association with long bone axis with an average deviation of 11.8° to 18.5°. The fracture pattern was also greatly affected by the structure with the crack path generally following the direction of the long axes of osteons. More importantly, we observed unique peripheral arc-shaped microcracks within osteons, using laser scanning confocal microscopy (LSCM). They were generally long cracks that developed within a lamella without crossing the boundaries. This microcracking pattern clearly differed from that created under either compressive or tensile stress: these arc-shaped microcracks tended to be located away from the Haversian canals in early-stage damaged osteons, with ~70% developing in the outer third osteonal wall. Further study by second harmonic generation (SHG) and two-photon excitation fluorescence (TPEF) microscopy revealed a strong influence of the organization of collagen

  12. Histological fate of cortical bone autografts in the middle ear.

    PubMed

    Mills, R P; Cree, I A

    1995-08-01

    Histological studies have been carried out on six cortical bone autografts and three ossicular grafts removed between 6 and 232 months after implantation in ossicular reconstructions. Both types of graft consisted mainly of dead bone, with some areas of viable osteocytes. Four out of six cortical bone grafts showed evidence of new bone formation and only one had reduced in size during the period in the middle ear. Fibrosis and inflammation were also noted in some specimens. In most cases cortical bone autografts appear to survive as well as ossicular grafts in the middle ear.

  13. Cortical bone distribution in the femoral neck of hominoids: implications for the locomotion of Australopithecus afarensis.

    PubMed

    Ohman, J C; Krochta, T J; Lovejoy, C O; Mensforth, R P; Latimer, B

    1997-09-01

    Contiguous high resolution computed tomography images were obtained at a 1.5 mm slice thickness perpendicular to the neck axis from the base of the femoral head to the trochanteric line in a sample of 10 specimens each of Homo sapiens, Pan troglodytes, and Gorilla gorilla, plus five specimens of Pan paniscus. Superior, inferior, anterior, and posterior cortical thicknesses were automatically measured directly from these digital images. Throughout the femoral neck H. sapiens displays thin superior cortical bone and inferior cortical bone that thickens distally. In marked contrast, cortical bone in the femoral neck of African apes is more uniformly thick in all directions, with even greater thickening of the superior cortical bone distally. Because the femoral neck acts as a cantilevered beam, its anchorage at the neck-shaft junction is subjected to the highest bending stresses and is the most biomechanically relevant region to inspect for response to strain. As evinced by A.L. 128-1, A.L. 211-1 and MAK-VP-1/1, Australopithecus afarensis is indistinguishable from H. sapiens, but markedly different from African apes in cortical bone distribution at the femoral neck-shaft junction. Cortical distribution in the African ape indicates much greater variation in loading conditions consistent with their more varied locomotor repertoire. Cortical distribution in hominids is a response to the more stereotypic loading pattern imposed by habitual bipedality, and thin superior cortex in A. afarensis confirms the absence of a significant arboreal component in its locomotor repertoire.

  14. The effect of shockwaves on mature and healing cortical bone.

    PubMed

    Forriol, F; Solchaga, L; Moreno, J L; Canãdell, J

    1994-10-01

    It has been proposed that high energy shockwaves could be used to create microfractures in cortical bone. This quality might be exploited clinically to perform closed osteotomies and promote healing in nonunion (15). However, no study has previously documented the effect of shockwaves on cortical bone "in vivo". We report an investigation designed to demonstrate the effect of shockwaves on mature cortical and healing bone. An osteotomy was performed on the tibiae of 37 lambs; two weeks later the operation site was exposed to shockwaves. Three weeks later the lambs were killed and specimens of the bone examined histologically and radiographically. Shockwaves had no effect on the periosteal surface of mature cortical bone, but on the endosteal surface some new trabecular bone was seen. Healing of bone was delayed by the shockwave therapy. We conclude that there is currently little place for shockwave treatment in clinical orthopaedics.

  15. Impact of lanthanum carbonate on cortical bone in dialysis patients with adynamic bone disease.

    PubMed

    Yajima, Aiji; Inaba, Masaaki; Tominaga, Yoshihiro; Tanaka, Motoko; Otsubo, Shigeru; Nitta, Kosaku; Ito, Akemi; Satoh, Shigeru

    2013-04-01

    Among the most serious problems in patients with chronic kidney disease (CKD) is fragility of cortical bone caused by cortical thinning and increased cortical porosity; the cortical fragility is sometimes irreversible, with fractures generally initiating from cortical bone. Therefore, development of treatments for problems of cortical bone is urgently desired. Cortical bone has the three surfaces, including the periosteal surface, intracortical spaces and endocortical surface. Bone turnover at the endocortical surface and intracortical resorption spaces are increased as compared with that at cancellous surface. Bone growth sometimes depends on apposition at the periosteal surface. We treated hyperphosphatemia in two hemodialysis patients with adynamic bone disease with 750-1500 mg/day of lanthanum carbonate, which is a non-calcium containing phosphate binder; the treatment resulted in a decrease of the serum phosphorus levels (P levels), without significant change of the serum intact parathyroid hormone levels. We now report that treatment of these patients with lanthanum carbonate increased mineralization of the periosteal surface, increased bone mass within the intracortical resorption spaces and increased mineralization of the minimodeling surface at the endocortical surface. In addition, woven bone volume in cortical bone was decreased and mineralization of bone units, namely, osteons, was increased. Although these findings were not observed across all surfaces of the cortical bone in the patients, it is expected that lanthanum carbonate would increase the cortical stability in CKD patients, with consequent reduction in the fracture rate in these patients.

  16. Comparisons of trabecular and cortical bone in late adolescent black and white females.

    PubMed

    Pollock, Norman K; Laing, Emma M; Taylor, Ruth G; Baile, Clifton A; Hamrick, Mark W; Hall, Daniel B; Lewis, Richard D

    2011-01-01

    Few childhood studies have investigated racial differences in volumetric bone mineral density (vBMD), bone geometry, and bone strength indices measured by three-dimensional bone imaging. The purpose of this study was to compare trabecular and cortical bone parameters at the radius and tibia between late adolescent white and black females using peripheral quantitative computed tomography (QCT). White (n = 25) and black females (n = 25), 18-19 years of age, were pair-matched for age, height, and fat-free soft tissue mass. Peripheral QCT scans were obtained at the 4% (trabecular bone), 20% (cortical bone), and 66% [muscle cross-sectional area (CSA)] sites from the distal metaphyses. Bone strength was determined from vBMD and bone geometry to calculate bone strength index (BSI; trabecular site) and polar strength-strain index (SSI; cortical site). Radial SSI was not different between groups; however, blacks had greater radial BSI (P = 0.02) than whites. After adjustment for the longer forearm in blacks, the greater radial BSI in blacks no longer remained. At the tibia, blacks versus whites had greater bone strength at the trabecular and cortical bone sites (BSI, P = 0.03; SSI, P = 0.04, respectively). When controlling for differences in tibial length and muscle CSA, the higher estimates of bone strength persisted in blacks versus whites (BSI, P = 0.01; SSI, P = 0.02). Our data suggest that when differences in body size are considered, late adolescent black versus white females have a stronger bone profile, due to greater bone geometry and vBMD, at the trabecular and cortical regions of the tibia but not at the radius.

  17. Increased Training Volume Improves Bone Density and Cortical Area in Adolescent Football Players.

    PubMed

    Varley, Ian; Hughes, David C; Greeves, Julie P; Fraser, William D; Sale, Craig

    2017-03-01

    Habitual football participation has been shown to be osteogenic, although the specific volume of football participation required to cause bone adaptations are not well established. The aim of the present study is to investigate tibial bone adaptations in response to 12 weeks of increased training volume in elite adolescents who are already accustomed to irregular impact training. 99 male adolescent elite footballers participated (age 16±0 y; height 1.76±0.66 m; body mass 70.2±8.3 kg). Tibial scans were performed using peripheral quantitative computed tomography immediately before and 12 weeks after an increase in football training volume. Scans were obtained at 4, 14, 38 and 66% of tibial length. Trabecular density (mg/cm(3)), cortical density (mg/cm(3)), cross-sectional area, cortical area (mm(2)), cortical thickness (mm) and strength strain index (mm(3)) were assessed. Trabecular (4%) and cortical density (14, 38%), cortical cross-sectional area (14, 38%), total cross-sectional area (66%), cortical thickness (14, 38%) and strength strain index (14, 38%) increased following 12 weeks of augmented volume training (P<0.05). Increased density of trabecular and cortical compartments and cortical thickening were shown following an increased volume of training. These adaptive responses may have been enhanced by the adolescent status of the cohort, supporting the role of early exercise intervention in improving bone strength.

  18. Cement line staining in undecalcified thin sections of cortical bone

    NASA Technical Reports Server (NTRS)

    Bain, S. D.; Impeduglia, T. M.; Rubin, C. T.

    1990-01-01

    A technique for demonstrating cement lines in thin, undecalcified, transverse sections of cortical bone has been developed. Cortical bone samples are processed and embedded undecalcified in methyl methacrylate plastic. After sectioning at 3-5 microns, cross-sections are transferred to a glass slide and flattened for 10 min. Sections of cortical bone are stained for 20 sec free-floating in a fresh solution of 1% toluidine blue dissolved in 0.1% formic acid. The section is dehydrated in t-butyl alcohol, cleared in xylene, and mounted with Eukitt's medium. Reversal lines appear as thin, scalloped, dark blue lines against a light blue matrix, whereas bone formation arrest lines are thicker with a smooth contour. With this technique cellular detail, osteoid differentiation, and fluorochrome labels are retained. Results demonstrate the applicability of a one-step staining method for cement lines which will facilitate the assessment of bone remodeling activity in thin sections of undecalcified cortical bone.

  19. A preliminary investigation of the dynamic viscoelastic relaxation of bovine cortical bone

    NASA Astrophysics Data System (ADS)

    Loete, T. J. C.; Paul, G.; Ismail, E. B.

    2015-09-01

    A new experimental approach is proposed to characterize the dynamic viscoelastic relaxation behaviour of cortical bone. Theoretical models are presented to show that a linear viscoelastic material, when allowed to relax between two long elastic bars, will produce stress, strain and strain rate histories that contain characteristic features. Furthermore, typical experimental results are presented to show that these characteristic features are observed during split Hopkinson bar tests on bovine cortical bone using a Cone-in-Tube striker. The interpretation of this behaviour in the context of a standard linear viscoelastic model is discussed.

  20. Strain driven transport for bone modeling at the periosteal surface.

    PubMed

    Banks-Sills, Leslie; Ståhle, Per; Svensson, Ingrid; Eliaz, Noam

    2011-03-01

    Bone modeling and remodeling has been the subject of extensive experimental studies. There have been several mathematical models proposed to explain the observed behavior, as well. A different approach is taken here in which the bone is treated from a macroscopic view point. In this investigation, a one-dimensional analytical model is used to shed light on the factors which play the greatest role in modeling or growth of cortical bone at the periosteal surface. It is presumed that bone growth is promoted when increased amounts of bone nutrients, such as nitric oxide synthase (NOS) or messenger molecules, such as prostaglandin E2 (PGE2), seep out to the periosteal surface of cortical bone and are absorbed by osteoblasts. The transport of the bone nutrients is assumed to be a strain controlled process. Equations for the flux of these nutrients are written for a one-dimensional model of a long bone. The obtained partial differential equation is linearized and solved analytically. Based upon the seepage of nutrients out of the bone, the effect of loading frequency, number of cycles and strain level is examined for several experiments that were found in the literature. It is seen that bone nutrient seepage is greatest on the tensile side of the bone; this location coincides with the greatest amount of bone modeling.

  1. Assessment of compressive failure process of cortical bone materials using damage-based model.

    PubMed

    Ng, Theng Pin; R Koloor, S S; Djuansjah, J R P; Abdul Kadir, M R

    2017-02-01

    The main failure factors of cortical bone are aging or osteoporosis, accident and high energy trauma or physiological activities. However, the mechanism of damage evolution coupled with yield criterion is considered as one of the unclear subjects in failure analysis of cortical bone materials. Therefore, this study attempts to assess the structural response and progressive failure process of cortical bone using a brittle damaged plasticity model. For this reason, several compressive tests are performed on cortical bone specimens made of bovine femur, in order to obtain the structural response and mechanical properties of the material. Complementary finite element (FE) model of the sample and test is prepared to simulate the elastic-to-damage behavior of the cortical bone using the brittle damaged plasticity model. The FE model is validated in a comparative method using the predicted and measured structural response as load-compressive displacement through simulation and experiment. FE results indicated that the compressive damage initiated and propagated at central region where maximum equivalent plastic strain is computed, which coincided with the degradation of structural compressive stiffness followed by a vast amount of strain energy dissipation. The parameter of compressive damage rate, which is a function dependent on damage parameter and the plastic strain is examined for different rates. Results show that considering a similar rate to the initial slope of the damage parameter in the experiment would give a better sense for prediction of compressive failure.

  2. Pueraria mirifica alleviates cortical bone loss in naturally menopausal monkeys.

    PubMed

    Kittivanichkul, Donlaporn; Charoenphandhu, Narattaphol; Khemawoot, Phisit; Malaivijitnond, Suchinda

    2016-11-01

    Since the in vitro and in vivo anti-osteoporotic effects of Pueraria mirifica (PM) in rodents have been verified, its activity in menopausal monkeys was evaluated as required before it can be applicable for human use. In this study, postmenopausal osteoporotic monkeys were divided into two groups (five per group), and fed daily with standard diet alone (PMP0 group) or diet mixed with 1000 mg/kg body weight (BW) of PM powder (PMP1000 group) for 16 months. Every 2 months, the bone mineral density (BMD), bone mineral content (BMC) and bone geometry parameters (cortical area and thickness and periosteal and endosteal circumference) at the distal radius and proximal tibia were determined using peripheral quantitative computed tomography together with plasma and urinary bone markers. Compared with the baseline (month 0) values, the cortical, but not trabecular, BMDs and BMCs and the cortical area and thickness at the metaphysis and diaphysis of the radius and tibia of the PMP0 group continuously decreased during the 16-month study period. In contrast, PMP1000 treatment ameliorated the bone loss mainly at the cortical diaphysis by decreasing bone turnover, as indicated by the lowered plasma bone-specific alkaline phosphatase and osteocalcin levels. Generally, changes in the cortical bone geometry were in the opposite direction to the cortical bone mass after PMP1000 treatment. This study indicated that postmenopausal monkeys continuously lose their cortical bone compartment, and they have a higher possibility for long bone fractures. Oral PMP treatment could improve both the bone quantity (BMC and BMD) and quality (bone geometry). © 2016 Society for Endocrinology.

  3. Variability and Anisotropy of Fracture Toughness of Cortical Bone Tissue

    NASA Astrophysics Data System (ADS)

    Abdel-Wahab, Adel; Nordin, Norhaziqah; Silberschmidt, Vadim

    2012-08-01

    Bones form protective and load-bearing framework of the body. Therefore, their structural integrity is vital for the quality of life. Unfortunately, bones can only sustain a load until a certain limit, beyond which they fail. Therefore, it is essential to study their mechanical and fracture behaviours in order to get an in-depth understanding of the origins of its fracture resistance that, in turn, can assist diagnosis and prevention of bone's trauma. This can be achieved by studying mechanical properties of bone, such as its fracture toughness. Generally, most of bone fractures occur for long bones that consist mostly of cortical bone. Therefore, in this study, only a cortical bone tissue was studied. Since this tissue has an anisotropic behaviour and possesses hierarchical and complex structure, in this paper, an experimental analysis for the fracture toughness of cortical bone tissue is presented in terms of J-integral. The data was obtained using single-edge-notch bending (SENB) cortical specimens of bone tested in a three-point bending setup. Variability of values of fracture toughness was investigated by testing specimens cut from different cortex positions of bovine femur called anterior, posterior, medial, and lateral. In addition, anisotropy ratios of fracture toughness were considered by examining specimens cut from three different orientations: longitudinal, transverse and radial. Moreover, in order to link cortical bone fracture mechanisms with its underlying microstructure, fracture surfaces of specimens from different cortices and along different orientations were studied. Experimental results of this study provide a clear understanding of both variability and anisotropy of cortical bone tissue with regard to its fracture toughness.

  4. Periosteal ganglion: a cause of cortical bone erosion.

    PubMed

    McCarthy, E F; Matz, S; Steiner, G C; Dorfman, H D

    1983-01-01

    Three cases of periosteal ganglia of long bones are presented. These lesions are produced by mucoid degeneration and cyst formation of the periosteum to produce external cortical erosion and reactive periosteal new bone. They are not associated with a soft tissue ganglion or an intraosseous lesion. They may radiologically mimic other periosteal lesions or soft tissue neoplasms which erode bone.

  5. Microstrain fields for cortical bone in uniaxial tension: optical analysis method.

    PubMed

    Kim, D G; Brunski, J B; Nicolella, D P

    2005-01-01

    This study employed an optical strain measurement method, called microdisplacements by machine vision photogrammetry (DISMAP), to measure both the global and local strain fields in microtensile specimens of cortical bone subjected to controlled uniaxial tension. The variation of local maximum principal strains was measured within the gauge region of samples as a function of applied tensile stress during testing. High gradients of local strain appeared around microstructural features in stressed bone even while the global strain for the entire gauge region showed a strong linear correlation with increasing tensile stress (r2 = 0.98, p < 0.0001). The highest local strain around microstructural features in bone was 11.5-79.5 times higher than the global strain.

  6. The Effects of Obesity on Murine Cortical Bone

    NASA Astrophysics Data System (ADS)

    Martin, Sophi

    This dissertation details the effects of obesity on the mechanical properties and structure of cortical bone. Obesity is associated with greater bone mineral content that might be expected to protect against fracture, which has been observed in adults. Paradoxically however, the incidence of bone fractures has been found to increase in overweight and obese children and adolescents. Femora from adolescent and adult mice fed a high-fat diet are investigated for changes in shape, tissue structure, as well as tissue-level and whole-bone mechanical properties. Results indicate increased bone size, reduced size-independent mechanical properties, but maintained size-dependent mechanical properties. Other changes in cortical bone response to obesity are observed with advancing age. This study indicates that bone quantity and bone quality play important compensatory roles in determining fracture risk, and that fracture risk may not be lessened for adults as previously thought.

  7. The importance of murine cortical bone microstructure for microcrack initiation and propagation.

    PubMed

    Voide, R; Schneider, P; Stauber, M; van Lenthe, G H; Stampanoni, M; Müller, R

    2011-12-01

    In order to better understand bone postyield behavior and consequently bone failure behavior, this study aimed first to investigate cortical bone microstructure and second, to relate cortical bone microstructure to microdamage initiation and propagation in C57BL/6 (B6) and C3H/He (C3H) mice; two murine inbred strains known for their differences in bone phenotype. Murine femora of B6 and C3H were loaded axially under compression in a stepwise manner. For each loading step, 3D data sets at a nominal resolution of 700 nm were acquired by means of synchrotron radiation-based computed tomography. Cortical bone microstructure was divided into three phases: the canal network, the osteocyte lacunar system, and microdamage. Canal volume density and canal unit volume both correlated highly to crack number density (canal volume density: R(2)=0.64, p<0.005 and canal unit volume: R(2)=0.75, p<0.001). Moreover, the large canal units in C3H bone were responsible for more microdamage accumulation compared to B6 bones. This more pronounced microdamage accumulation due to large intracortical bone voids, which eventually leads to a fatal macrocrack (fracture), represents a potential contributing factor to the higher incidence of bone fractures in the elderly. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. Broken Bones, Sprains, and Strains (For Parents)

    MedlinePlus

    ... for TV, Video Games, and the Internet Broken Bones, Sprains, and Strains KidsHealth > For Parents > Broken Bones, ... home. What to Do: For a Suspected Broken Bone: Do not move a child whose injury involves ...

  9. Effect of micromorphology of cortical bone tissue on crack propagation under dynamic loading

    NASA Astrophysics Data System (ADS)

    Wang, Mayao; Gao, Xing; Abdel-Wahab, Adel; Li, Simin; Zimmermann, Elizabeth A.; Riedel, Christoph; Busse, Björn; Silberschmidt, Vadim V.

    2015-09-01

    Structural integrity of bone tissue plays an important role in daily activities of humans. However, traumatic incidents such as sports injuries, collisions and falls can cause bone fracture, servere pain and mobility loss. In addition, ageing and degenerative bone diseases such as osteoporosis can increase the risk of fracture [1]. As a composite-like material, a cortical bone tissue is capable of tolerating moderate fracture/cracks without complete failure. The key to this is its heterogeneously distributed microstructural constituents providing both intrinsic and extrinsic toughening mechanisms. At micro-scale level, cortical bone can be considered as a four-phase composite material consisting of osteons, Haversian canals, cement lines and interstitial matrix. These microstructural constituents can directly affect local distributions of stresses and strains, and, hence, crack initiation and propagation. Therefore, understanding the effect of micromorphology of cortical bone on crack initiation and propagation, especially under dynamic loading regimes is of great importance for fracture risk evaluation. In this study, random microstructures of a cortical bone tissue were modelled with finite elements for four groups: healthy (control), young age, osteoporosis and bisphosphonate-treated, based on osteonal morphometric parameters measured from microscopic images for these groups. The developed models were loaded under the same dynamic loading conditions, representing a direct impact incident, resulting in progressive crack propagation. An extended finite-element method (X-FEM) was implemented to realize solution-dependent crack propagation within the microstructured cortical bone tissues. The obtained simulation results demonstrate significant differences due to micromorphology of cortical bone, in terms of crack propagation characteristics for different groups, with the young group showing highest fracture resistance and the senior group the lowest.

  10. Anisotropy in the compressive mechanical properties of bovine cortical bone and the mineral and protein constituents.

    PubMed

    Novitskaya, Ekaterina; Chen, Po-Yu; Lee, Steve; Castro-Ceseña, Ana; Hirata, Gustavo; Lubarda, Vlado A; McKittrick, Joanna

    2011-08-01

    The mechanical properties of fully demineralized, fully deproteinized and untreated cortical bovine femur bone were investigated by compression testing in three anatomical directions (longitudinal, radial and transverse). The weighted sum of the stress-strain curves of the treated bones was far lower than that of the untreated bone, indicating a strong molecular and/or mechanical interaction between the collagen matrix and the mineral phase. Demineralization and deproteinization of the bone demonstrated that contiguous, stand-alone structures result, showing that bone can be considered an interpenetrating composite material. Structural features of the samples from all groups were studied by optical and scanning electron microscopy. Anisotropic mechanical properties were observed: the radial direction was found to be the strongest for untreated bone, while the longitudinal one was found to be the strongest for deproteinized and demineralized bones. A possible explanation for this phenomenon is the difference in bone microstructure in the radial and longitudinal directions.

  11. Women Build Long Bones With Less Cortical Mass Relative to Body Size and Bone Size Compared With Men.

    PubMed

    Jepsen, Karl J; Bigelow, Erin M R; Schlecht, Stephen H

    2015-08-01

    from recombinant inbred mouse strains showed the opposite trend; femurs from female mice had a 4% larger cortical area compared with those of male mice after adjusting for body size and bone size (female: mean=0.73 mm2; 95% CI, 0.71-0.74 mm2; male: mean=0.70 mm2; 95% CI, 0.68-0.71 mm2; effect size=0.74; p=0.04, GLM). Female femurs are not simply a more slender version of male femurs. Women acquire substantially less mass (cortical area) for their body size and bone size compared with men. Our analysis questions whether mouse long bone is a suitable model to study human sexual dimorphism. Identifying differences in the way bones are constructed may be clinically important for developing sex-specific diagnostics and treatment strategies to reduce fragility fractures.

  12. Prostaglandin E2 Prevents Disuse-Induced Cortical Bone Loss

    NASA Technical Reports Server (NTRS)

    Jee, Webster S. S.; Akamine, T.; Ke, Hua Zhu; Li, Xiao Jian; Tang, L. Y.; Zeng, Q. Q.

    1992-01-01

    The object of this study was to determine whether prostaglandin E2 (PGE2) can prevent disuse (underloaded)-induced cortical bone loss as well as add extra bone to underloaded bones. Thirteen-month-old retired female Sprague-Dawley breeders served as controls or were subjected to simultaneous right hindlimb immobilization by bandaging and daily subcutaneous doses of 0, 1, 3, or 6 mg PGE2/kg/d for two and six weeks. Histomorphometric analyses were performed on double-fluorescent labeled undecalcified tibial shaft sections (proximal to the tibiofibular junction). Disuse-induced cortical bone loss occurred by enlarging the marrow cavity and increasing intracortical porosity. PGE2 treatment of disuse shafts further increased intracortical porosity above that in disuse alone controls. This bone loss was counteracted by enhancement of periosteal and corticoendosteal bone formation. Stimulation of periosteal and corticoendosteal bone formation slightly enlarged the total tissue (cross-sectional) area and inhibited marrow cavity enlargement. These PGE2-induced activities netted the same percentage of cortical bone with a different distribution than the beginning and age related controls. These findings indicate the PGE2-induced increase in bone formation compensated for the disuse and PGE2-induced bone loss, and thus prevented immobilization induced bone loss.

  13. Material properties of mandibular cortical bone in the American alligator, Alligator mississippiensis.

    PubMed

    Zapata, Uriel; Metzger, Keith; Wang, Qian; Elsey, Ruth M; Ross, Callum F; Dechow, Paul C

    2010-03-01

    This study reports the elastic material properties of cortical bone in the mandible of juvenile Alligator mississippiensis obtained by using an ultrasonic wave technique. The elastic modulus, the shear modulus, and Poisson's ratio were measured on 42 cylindrical Alligator bone specimens obtained from the lingual and facial surfaces of 4 fresh Alligator mandibles. The data suggest that the elastic properties of alligator mandibular cortical bone are similar to those found in mammals and are orthotropic. The properties most resemble those found in the cortex of mammalian postcranial long bones where the bone is most stiff in one direction and much less stiff in the two remaining orthogonal directions. This is different from cortical bone found in the mandibles of humans and some monkeys, where the bone has greatest stiffness in one direction, much less stiffness in another direction, and an intermediate amount in the third orthogonal direction. This difference suggests a relationship between levels of orthotropy and bending stress. The comparability of these elastic moduli to those of other vertebrates suggest that the high bone strain magnitudes recorded from the alligator mandible in vivo are not attributable to a lower stiffness of alligator mandibular bone.

  14. Strain changes on the cortical shell of vertebral bodies due to spine ageing: a parametric study using a finite element model evaluated by strain measurements.

    PubMed

    Lu, Yongtao; Rosenau, Eike; Paetzold, Helge; Klein, Anke; Püschel, Klaus; Morlock, Michael M; Huber, Gerd

    2013-12-01

    The probability of fractures of the cortical shell of vertebral bodies increases as ageing progresses. Ageing involves all the spinal component changes. However, the effect of the spinal component ageing on the fracture risk of the cortical shell remains poorly understood. In this study, the influence of the ageing of the spinal components on cortical shell strain was investigated. A lumbar spinal specimen (L3-L5) was mechanically tested under a quasi-static axial compressive load. Clinical computed tomography images of the same specimen were used to create a corresponding finite element model. The material properties were determined by calibrating the finite element model using the L4 cortical shell strains of the anterior centre measurement site. The remaining experiment data (axial displacement, the intra-discal pressures, L4 cortical shell strain on the lateral measurement site) were used to evaluate the model. The individual ageing process of the six spinal components (cortical shell, cancellous bone, bony endplate, posterior elements, nucleus pulposus and annulus matrix) was simulated by changing their Young's moduli and Poisson's ratios, and the effect on cortical shell strain was investigated. Results show that the cortical shell strain is more sensitive to the ageing of the cortical shell and the cancellous bone than to the ageing of the nucleus pulposus, the annulus matrix, and the bony endplates and of the posterior elements. The results can help the clinicians focus on the aspects that mainly influence the vertebral cortex fracture risk factor.

  15. Cortical bone drilling: An experimental and numerical study.

    PubMed

    Alam, Khurshid; Bahadur, Issam M; Ahmed, Naseer

    2014-12-16

    Bone drilling is a common surgical procedure in orthopedics, dental and neurosurgeries. In conventional bone drilling process, the surgeon exerts a considerable amount of pressure to penetrate the drill into the bone tissue. Controlled penetration of drill in the bone is necessary for safe and efficient drilling. Development of a validated Finite Element (FE) model of cortical bone drilling. Drilling experiments were conducted on bovine cortical bone. The FE model of the bone drilling was based on mechanical properties obtained from literature data and additionally conducted microindentation tests on the cortical bone. The magnitude of stress in bone was found to decrease exponentially away from the lips of the drill in simulations. Feed rate was found to be the main influential factor affecting the force and torque in the numerical simulations and experiments. The drilling thrust force and torque were found to be unaffected by the drilling speed in numerical simulations. Simulated forces and torques were compared with experimental results for similar drilling conditions and were found in good agreement.CONCLUSIONS: FE schemes may be successfully applied to model complex kinematics of bone drilling process.

  16. Cortical bone screw fixation in ionically modified apatite cements.

    PubMed

    Barralet, J E; Duncan, C O; Dover, M S; Bassett, D C; Nishikawa, H; Monaghan, A; Gbureck, U

    2005-05-01

    Hydroxyapatite cements are used in reconstruction of the face; usually in well-defined cavities where the cement can be stabilized without the need for internal fixation. A hydroxyapatite cement that could enable screw fixation and some loading therefore has considerable potential in maxillofacial reconstruction. It has been demonstrated recently that water demand of calcium phosphate cements can be reduced by ionically modifying the liquid component. This study investigated the capacity of an ionically modified precompacted apatite cement to retain self-tapping cortical bone screws. Screw pullout forces were determined in the direction of the screw long axis and perpendicular to it, using cortical bone and polymethylmethacrylate cement as a control. In bending pullout tests, measured forces to remove screws from ionically modified precompacted cement were insignificantly different from cortical bone. However, pullout forces of bone screws from hydroxyapatite cement decreased with aging time in vitro. (c) 2005 Wiley Periodicals, Inc.

  17. Micromechanical Modeling of R-Curve Behaviors in Human Cortical Bone

    PubMed Central

    Chan, Kwai S.; Nicolella, Daniel P.

    2012-01-01

    The risk of bone fracture increases with age because of a variety of factors that include, among others, decreasing bone quantity and quality due to increasing porosity and crack density with age. Experimental evidence has indicated that changes in bone microstructure and trace mineralization with age can result in different crack-tip strain field and fracture response, leading to different fracture mechanisms and R-curve behaviors. In this paper, a micromechanical modeling approach is developed to predict the R-curve response of bone tissue by delineating fracture mechanisms that lead to microdamage and ligament bridging by incorporating the influence of increasing porosity and crack density with age. The effects of age on fracture of human femur cortical bone due to porosity (bone quantity) and bone quality (crack density) with age are then examined via the micromechanical model. PMID:23158217

  18. Micromechanical modeling of R-curve behaviors in human cortical bone.

    PubMed

    Chan, Kwai S; Nicolella, Daniel P

    2012-12-01

    The risk of bone fracture increases with age because of a variety of factors that include, among others, decreasing bone quantity and quality due to increasing porosity and crack density with age. Experimental evidence has indicated that changes in bone microstructure and trace mineralization with age can result in different crack-tip strain field and fracture response, leading to different fracture mechanisms and R-curve behaviors. In this paper, a micromechanical modeling approach is developed to predict the R-curve response of bone tissue by delineating fracture mechanisms that lead to microdamage and ligament bridging by incorporating the influence of increasing porosity and crack density with age. The effects of age on fracture of human femur cortical bone due to porosity (bone quantity) and bone quality (crack density) with age are then examined via the micromechanical model.

  19. Equine cortical bone exhibits rising R-curve fracture mechanics.

    PubMed

    Malik, C L; Stover, S M; Martin, R B; Gibeling, J C

    2003-02-01

    Previous studies of the fracture properties of cortical bone have suggested that the fracture toughness increases with crack length, which is indicative of rising R-curve behavior. Based on this indirect evidence and the similarity of bone to ceramic matrix composites, we hypothesized that bone would exhibit rising R-curve behavior in the transverse orientation and that the characteristics of the R-curves would be regionally dependent within the cortex due to variations in bone microstructure and toughening mechanisms. To test these hypotheses, we conducted R-curve experiments on specimens from equine third metacarpal bones using standard fracture mechanics testing methods. Compact type specimens from the dorsal and lateral regions in the middle of the diaphysis were oriented for crack propagation transverse to the longitudinal axis of the bone. The test results demonstrate that equine cortical bone exhibits rising R-curve behavior during transverse crack propagation as hypothesized. Statistical analyses of the crack growth initiation toughness, K0, the peak toughness, Kpeak, and the crack extension at peak toughness, deltaa, revealed significant regional differences in these characteristics. Specifically, the lateral cortex displayed higher crack growth initiation and peak toughnesses. The dorsal cortex exhibited greater crack extension at the peak of crack growth resistance. Scanning electron microscopy revealed osteon pullout on fracture surfaces from the dorsal cortex and but not in the lateral cortex. Taken together, the significant differences in R-curves and the SEM fractography indicate that the fracture mechanisms acting in equine cortical bone are regionally dependent.

  20. Phenotypic integration among trabecular and cortical bone traits establishes mechanical functionality of inbred mouse vertebrae.

    PubMed

    Tommasini, Steven M; Hu, Bin; Nadeau, Joseph H; Jepsen, Karl J

    2009-04-01

    Conventional approaches to identifying quantitative trait loci (QTLs) regulating bone mass and fragility are limited because they examine cortical and trabecular traits independently. Prior work examining long bones from young adult mice and humans indicated that skeletal traits are functionally related and that compensatory interactions among morphological and compositional traits are critical for establishing mechanical function. However, it is not known whether trait covariation (i.e., phenotypic integration) also is important for establishing mechanical function in more complex, corticocancellous structures. Covariation among trabecular, cortical, and compositional bone traits was examined in the context of mechanical functionality for L(4) vertebral bodies across a panel of 16-wk-old female AXB/BXA recombinant inbred (RI) mouse strains. The unique pattern of randomization of the A/J and C57BL/6J (B6) genome among the RI panel provides a powerful tool that can be used to measure the tendency for different traits to covary and to study the biology of complex traits. We tested the hypothesis that genetic variants affecting vertebral size and mass are buffered by changes in the relative amounts of cortical and trabecular bone and overall mineralization. Despite inheriting random sets of A/J and B6 genomes, the RI strains inherited nonrandom sets of cortical and trabecular bone traits. Path analysis, which is a multivariate analysis that shows how multiple traits covary simultaneously when confounding variables like body size are taken into consideration, showed that RI strains that tended to have smaller vertebrae relative to body size achieved mechanical functionality by increasing mineralization and the relative amounts of cortical and trabecular bone. The interdependence among corticocancellous traits in the vertebral body indicated that variation in trabecular bone traits among inbred mouse strains, which is often thought to arise from genetic factors, is also

  1. The aging of Wolff's "law": ontogeny and responses to mechanical loading in cortical bone.

    PubMed

    Pearson, Osbjorn M; Lieberman, Daniel E

    2004-01-01

    The premise that bones grow and remodel throughout life to adapt to their mechanical environment is often called Wolff's law. Wolff's law, however, is not always true, and in fact comprises a variety of different processes that are best considered separately. Here we review the molecular and physiological mechanisms by which bone senses, transduces, and responds to mechanical loads, and the effects of aging processes on the relationship (if any) between cortical bone form and mechanical function. Experimental and comparative evidence suggests that cortical bone is primarily responsive to strain prior to sexual maturity, both in terms of the rate of new bone growth (modeling) as well as rates of turnover (Haversian remodeling). Rates of modeling and Haversian remodeling, however, vary greatly at different skeletal sites. In addition, there is no simple relationship between the orientation of loads in long bone diaphyses and their cross-sectional geometry. In combination, these data caution against assuming without testing adaptationist views about form-function relationships in order to infer adult activity patterns from skeletal features such as cross-sectional geometry, cortical bones density, and musculo-skeletal stress markers. Efforts to infer function from shape in the human skeleton should be based on biomechanical and developmental models that are experimentally tested and validated.

  2. Disuse exaggerates the detrimental effects of alcohol on cortical bone

    NASA Technical Reports Server (NTRS)

    Hefferan, Theresa E.; Kennedy, Angela M.; Evans, Glenda L.; Turner, Russell T.

    2003-01-01

    BACKGROUND: Alcohol abuse is associated with an increased risk for osteoporosis. However, comorbidity factors may play an important role in the pathogenesis of alcohol-related bone fractures. Suboptimal mechanical loading of the skeleton, an established risk factor for bone loss, may occur in some alcohol abusers due to reduced physical activity, muscle atrophy, or both. The effect of alcohol consumption and reduced physical activity on bone metabolism has not been well studied. The purpose of this study was to determine whether mechanical disuse alters bone metabolism in a rat model for chronic alcohol abuse. METHODS: Alcohol was administered in the diet (35% caloric intake) of 6-month-old male rats for 4 weeks. Rats were hindlimb-unloaded the final 2 weeks of the experiment to prevent dynamic weight bearing. Afterward, cortical bone histomorphometry was evaluated at the tibia-fibula synostosis. RESULTS: At the periosteal surface of the tibial diaphysis, alcohol and hindlimb unloading independently decreased the mineralizing perimeter, mineral apposition rate, and bone formation rate. In addition, alcohol, but not hindlimb unloading, increased endocortical bone resorption. The respective detrimental effects of alcohol and hindlimb unloading to inhibit bone formation were additive; there was no interaction between the two variables. CONCLUSIONS: Reduced weight bearing accentuates the detrimental effects of alcohol on cortical bone in adult male rats by further inhibiting bone formation. This finding suggests that reduced physical activity may be a comorbidity factor for osteoporosis in alcohol abusers.

  3. Disuse exaggerates the detrimental effects of alcohol on cortical bone

    NASA Technical Reports Server (NTRS)

    Hefferan, Theresa E.; Kennedy, Angela M.; Evans, Glenda L.; Turner, Russell T.

    2003-01-01

    BACKGROUND: Alcohol abuse is associated with an increased risk for osteoporosis. However, comorbidity factors may play an important role in the pathogenesis of alcohol-related bone fractures. Suboptimal mechanical loading of the skeleton, an established risk factor for bone loss, may occur in some alcohol abusers due to reduced physical activity, muscle atrophy, or both. The effect of alcohol consumption and reduced physical activity on bone metabolism has not been well studied. The purpose of this study was to determine whether mechanical disuse alters bone metabolism in a rat model for chronic alcohol abuse. METHODS: Alcohol was administered in the diet (35% caloric intake) of 6-month-old male rats for 4 weeks. Rats were hindlimb-unloaded the final 2 weeks of the experiment to prevent dynamic weight bearing. Afterward, cortical bone histomorphometry was evaluated at the tibia-fibula synostosis. RESULTS: At the periosteal surface of the tibial diaphysis, alcohol and hindlimb unloading independently decreased the mineralizing perimeter, mineral apposition rate, and bone formation rate. In addition, alcohol, but not hindlimb unloading, increased endocortical bone resorption. The respective detrimental effects of alcohol and hindlimb unloading to inhibit bone formation were additive; there was no interaction between the two variables. CONCLUSIONS: Reduced weight bearing accentuates the detrimental effects of alcohol on cortical bone in adult male rats by further inhibiting bone formation. This finding suggests that reduced physical activity may be a comorbidity factor for osteoporosis in alcohol abusers.

  4. Cortical bone loss with age in three native American populations.

    PubMed

    Ericksen, M F

    1976-11-01

    Age-related thinning of cortical bone was investigated in archaeological populations of Eskimos, Pueblos, and Arikaras. Medial-lateral cortical thickness was measured on radiographs of humerus and femur, and thickness of the anterior femoral cortex was measured directly on samples taken for histologic study. Maximum length of the bones was used to calculate indices of relative cortical thickness, in order to minimize differences due to body size and build. Bone loss in the humerus begins before middle age in all three populations and, except for Eskimo males, the same is true of the anterior femoral cortex. In general, overall female loss of cortical bone amounts to two or three times that of the males, and in the case of the humerus and the anterior cortex of the femur, this difference is evident by middle age. The weight-bearing femoral medial-lateral cortex shows less sexual difference but has the greatest number of statistically significant differences between populations and the greatest contrast between populations in pattern of loss with age. It appears that of the cortical regions studied this is the area upon which environmental factors have the greatest effect, whereas areas more subject to tensile stress, the humerus and anterior femoral cortex, are less affected by these factors.

  5. Architecture and microstructure of cortical bone in reconstructed canine mandibles after bone transport distraction osteogenesis.

    PubMed

    Zapata, Uriel; Halvachs, Emily K; Dechow, Paul C; Elsalanty, Mohammed E; Opperman, Lynne A

    2011-11-01

    Reconstruction of the canine mandible using bone transport distraction osteogenesis has been shown to be a suitable method for correcting segmental bone defects produced by cancer, gunshots, and trauma. Although the mechanical quality of the new regenerate cortical bone seems to be related to the mineralization process, several questions regarding the microstructural patterns of the new bony tissue remain unanswered. The purpose of this study was to quantify any microstructural differences that may exist between the regenerate and control cortical bone. Five adult American foxhound dogs underwent unilateral bone transport distraction of the mandible to repair bone defects of 30-35 mm. Animals were killed 12 weeks after the beginning of the consolidation period. Fourteen cylindrical cortical samples were extracted from the superior, medial, and inferior aspects of the lingual and buccal plates of the reconstructed aspect of the mandible, and 21 specimens were collected similarly from the contralateral aspect of the mandible. Specimens were evaluated using histomorphometric and micro-computed tomographic techniques to compare their microstructure. Except for differences in haversian canal area, histomorphometric analyses suggested no statistical differences in microstructure between regenerate and control cortical bone. Morphological evaluation suggested a consistent level of anisotropy, possibly related to the distraction vector. After 12 weeks' consolidation, bone created during bone transport distraction osteogenesis was comparable to native bone in microstructure, architecture, and mechanical properties. It is proposed that, after enough time, the properties of the regenerate bone will be identical to that of native bone.

  6. Qualitative and quantitative ultrashort-TE MRI of cortical bone

    PubMed Central

    Du, Jiang; Bydder, Graeme M.

    2014-01-01

    Osteoporosis causes over 1.5 million fractures per year, costing about $15 billion annually in the USA. Current guidelines utilize bone mineral density (BMD) to assess fracture risk; however, BMD alone only accounts for 30–50% of fractures. The other two major components of bone, organic matrix and water, contribute significantly to bone mechanical properties, but cannot be assessed with conventional imaging techniques in spite of the fact that they make up about 57% of cortical bone by volume. Conventional clinical MRI usually detects signals from water in tissues without difficulty, but cannot detect the water bound to the organic matrix, or the free water in the microscopic pores of the Haversian and the lacunar-canalicular system of cortical bone, because of their very short apparent transverse relaxation times (T2*). In recent years, a new class of sequences, ultrashort-TE (UTE) sequences, with nominal TEs of less than 100 μs, which are much shorter than the TEs available with conventional sequences, have received increasing interest. These sequences can detect water signals from within cortical bone and provide an opportunity to study disease of this tissue in a new way. This review summarizes the recent developments in qualitative UTE imaging (techniques and contrast mechanisms to produce bone images with high contrast) and quantitative UTE imaging (techniques to quantify the MR properties, including T1, T2* and the magnetization transfer ratio, and tissue properties, including bone perfusion, as well as total, bound and free water content) of cortical bone in vitro and in vivo. The limitations of the current techniques for clinical applications and future directions are also discussed. PMID:23280581

  7. Mammalian cortical bone in tension is non-Haversian

    NASA Astrophysics Data System (ADS)

    Mayya, Ashwij; Banerjee, Anuradha; Rajesh, R.

    2013-08-01

    Cortical bone, found in the central part of long bones like femur, is known to adapt to local mechanical stresses. This adaptation has been linked exclusively with Haversian remodelling involving bone resorption and formation of secondary osteons. Compared to primary/plexiform bone, the Haversian bone has lower stiffness, fatigue strength and fracture toughness, raising the question why nature prefers an adaptation that is detrimental to bone's primary function of bearing mechanical stresses. Here, we show that in the goat femur, Haversian remodelling occurs only at locations of high compressive stresses. At locations corresponding to high tensile stresses, we observe a microstructure that is non-Haversian. Compared with primary/plexiform bone, this microstructure's mineralisation is significantly higher with a distinctly different spatial pattern. Thus, the Haversian structure is an adaptation only to high compressive stresses rendering its inferior tensile properties irrelevant as the regions with high tensile stresses have a non-Haversian, apparently primary microstructure.

  8. The effect of supercritical carbon dioxide sterilization on the anisotropy of bovine cortical bone.

    PubMed

    Russell, Nicholas; Rives, Alain; Pelletier, Matthew H; Wang, Tian; Walsh, William R

    2015-03-01

    Bone allografts are used to replace bone that has been removed or to augment bone tissue in a number of clinical scenarios. In order to minimize the risk of infection and immune response, the bone is delipidated and terminally sterilized prior to implantation. The optimal method for bone graft sterilization has been the topic of considerable research and debate. Recently, supercritical carbon dioxide (SCCO(2)) treatments have been shown to terminally sterilize bone against a range of bacteria and viruses. This study aimed to evaluate the effect of these SCCO(2) treatments on the anisotropic mechanical properties of cortical bone. Adult bovine cortical cubes were prepared and treated using SCCO(2) and a range of common processing additives (ethanol, peracetic acid and hydrogen peroxide). The bone was mechanically tested in uniaxial compression in the axial, radial and tangential orientations. Ultimate stress, strain, elastic modulus, energy and stiffness were evaluated. This study found that SCCO(2) treatment without additive did not alter the ultimate stress, stiffness or energy to failure depreciably in any orientation. The addition of sterilants peracetic acid and hydrogen peroxide also preserved mechanical function, with no deleterious effect on stress or stiffness. This study highlights the expediency of SCCO(2) treatment for bone allograft processing as terminal sterilization can be achieved while maintaining the intrinsic mechanical properties of the graft.

  9. Fracture toughness and fatigue crack propagation rate of short fiber reinforced epoxy composites for analogue cortical bone.

    PubMed

    Chong, Alexander C M; Miller, Forrest; Buxton, McKee; Friis, Elizabeth A

    2007-08-01

    Third-generation mechanical analogue bone models and synthetic analogue cortical bone materials manufactured by Pacific Research Laboratories, Inc. (PRL) are popular tools for use in mechanical testing of various orthopedic implants and biomaterials. A major issue with these models is that the current third-generation epoxy-short fiberglass based composite used as the cortical bone substitute is prone to crack formation and failure in fatigue or repeated quasistatic loading of the model. The purpose of the present study was to compare the tensile and fracture mechanics properties of the current baseline (established PRL "third-generation" E-glass-fiber-epoxy) composite analogue for cortical bone to a new composite material formulation proposed for use as an enhanced fourth-generation cortical bone analogue material. Standard tensile, plane strain fracture toughness, and fatigue crack propagation rate tests were performed on both the third- and fourth-generation composite material formulations using standard ASTM test techniques. Injection molding techniques were used to create random fiber orientation in all test specimens. Standard dog-bone style tensile specimens were tested to obtain ultimate tensile strength and stiffness. Compact tension fracture toughness specimens were utilized to determine plane strain fracture toughness values. Reduced thickness compact tension specimens were also used to determine fatigue crack propagation rate behavior for the two material groups. Literature values for the same parameters for human cortical bone were compared to results from the third- and fourth-generation cortical analogue bone materials. Tensile properties of the fourth-generation material were closer to that of average human cortical bone than the third-generation material. Fracture toughness was significantly increased by 48% in the fourth-generation composite as compared to the third-generation analogue bone. The threshold stress intensity to propagate the crack

  10. Crack growth resistance in cortical bone: concept of microcrack toughening.

    PubMed

    Vashishth, D; Behiri, J C; Bonfield, W

    1997-08-01

    The role of microcracking in cortical bone as a toughening mechanism has been investigated in conjunction with the variation in fracture toughness with crack length. Fracture toughness tests were conducted on miniaturised compact tension specimens made from human and bovine cortical bone and the resultant microstructural damage, present in the form of microcracking on the surface, was analysed around the main propagating crack. It was found that the fracture toughness (Kc) and the cumulative number of microcracks increased linearly with crack extension in human and bovine cortical bone, although both Kc and number of microcracks were considerably higher in the latter case. Based on these results, a mechanism, derived from the resistance (R) curve concept developed for microcracking brittle solids, is proposed to explain the fracture of cortical bone, with microcracking distributed between a frontal process zone and a significant process zone wake. Evidence to support this mechanism is given from the existing bone literature, detailed scanning electron microscopical observations and the distribution of microcracks in the process zone wake.

  11. Strain amplification in the bone mechanosensory system.

    PubMed

    Cowin, S C; Weinbaum, S

    1998-09-01

    This article discusses the potential mechanisms by which the strain induced at the membrane of an osteocyte may be amplified from the strain experienced by the whole bone due to mechanical loading. These mechanisms address the question of how these mechanical load-induced small strains of (typically) about 0.1% (but up to 0.5%) applied to a whole bone are amplified to strains of 1% or larger at the membrane of the osteocyte buried in its lacuna in the bone matrix. The answer to this question is an important link in the mechanosensory system in bone and in relating in vitro cell studies to in vivo cellular response.

  12. Influence of cortical bone thickness on the ultrasound velocity

    PubMed Central

    Mandarano-Filho, Luiz Garcia; Bezuti, Márcio Takey; Mazzer, Nilton; Barbieri, Cláudio Henrique

    2012-01-01

    Objective An experimental in vitro study was carried out to evaluate the influence of cortical bone thickness on ultrasound propagation velocity. Methods Sixty bone plates were used, made from bovine femurs, with thickness ranging from 1 to 6 mm (10 of each). The ultrasound velocity measurements were performed using a device specially designed for this purpose, in an underwater acoustic tank and with direct contact using contact gel. The transducers were positioned in two ways: on opposite sides, with the bone between them, for the transverse measurement; and parallel to each other, on the same side of the bone plates, for the axial measurements. Results In the axial transmission mode, the ultrasound velocity speed increased with cortical bone thickness, regardless of the distance between the transducers, up to a thickness of 5 mm, then remained constant thereafter. There were no changes in velocity when the transverse measures were made. Conclusion Ultrasound velocity increased with cortical bone thickness in the axial transmission mode, until the thickness surpasses the wavelength, after which point it remained constant. Level of Evidence: Experimental Study. PMID:24453601

  13. Bone density and cortical structure after pediatric renal transplantation.

    PubMed

    Terpstra, Anniek M; Kalkwarf, Heidi J; Shults, Justine; Zemel, Babette S; Wetzsteon, Rachel J; Foster, Bethany J; Strife, C Frederic; Foerster, Debbie L; Leonard, Mary B

    2012-04-01

    The impact of renal transplantation on trabecular and cortical bone mineral density (BMD) and cortical structure is unknown. We obtained quantitative computed tomography scans of the tibia in pediatric renal transplant recipients at transplantation and 3, 6, and 12 months; 58 recipients completed at least two visits. We used more than 700 reference participants to generate Z-scores for trabecular BMD, cortical BMD, section modulus (a summary measure of cortical dimensions and strength), and muscle and fat area. At baseline, compared with reference participants, renal transplant recipients had significantly lower mean section modulus and muscle area; trabecular BMD was significantly greater than reference participants only in transplant recipients younger than 13 years. After transplantation, trabecular BMD decreased significantly in association with greater glucocorticoid exposure. Cortical BMD increased significantly in association with greater glucocorticoid exposure and greater decreases in parathyroid hormone levels. Muscle and fat area both increased significantly, but section modulus did not improve. At 12 months, transplantation associated with significantly lower section modulus and greater fat area compared with reference participants. Muscle area and cortical BMD did not differ significantly between transplant recipients and reference participants. Trabecular BMD was no longer significantly elevated in younger recipients and was low in older recipients. Pediatric renal transplant associated with persistent deficits in section modulus, despite recovery of muscle, and low trabecular BMD in older recipients. Future studies should determine the implications of these data on fracture risk and identify strategies to improve bone density and structure.

  14. Bone Density and Cortical Structure after Pediatric Renal Transplantation

    PubMed Central

    Terpstra, Anniek M.; Kalkwarf, Heidi J.; Shults, Justine; Zemel, Babette S.; Wetzsteon, Rachel J.; Foster, Bethany J.; Strife, C. Frederic; Foerster, Debbie L.

    2012-01-01

    The impact of renal transplantation on trabecular and cortical bone mineral density (BMD) and cortical structure is unknown. We obtained quantitative computed tomography scans of the tibia in pediatric renal transplant recipients at transplantation and 3, 6, and 12 months; 58 recipients completed at least two visits. We used more than 700 reference participants to generate Z-scores for trabecular BMD, cortical BMD, section modulus (a summary measure of cortical dimensions and strength), and muscle and fat area. At baseline, compared with reference participants, renal transplant recipients had significantly lower mean section modulus and muscle area; trabecular BMD was significantly greater than reference participants only in transplant recipients younger than 13 years. After transplantation, trabecular BMD decreased significantly in association with greater glucocorticoid exposure. Cortical BMD increased significantly in association with greater glucocorticoid exposure and greater decreases in parathyroid hormone levels. Muscle and fat area both increased significantly, but section modulus did not improve. At 12 months, transplantation associated with significantly lower section modulus and greater fat area compared with reference participants. Muscle area and cortical BMD did not differ significantly between transplant recipients and reference participants. Trabecular BMD was no longer significantly elevated in younger recipients and was low in older recipients. Pediatric renal transplant associated with persistent deficits in section modulus, despite recovery of muscle, and low trabecular BMD in older recipients. Future studies should determine the implications of these data on fracture risk and identify strategies to improve bone density and structure. PMID:22282589

  15. Estimation of the poroelastic parameters of cortical bone.

    PubMed

    Smit, Theo H; Huyghe, Jacques M; Cowin, Stephen C

    2002-06-01

    Cortical bone has two systems of interconnected channels. The largest of these is the vascular porosity consisting of Haversian and Volkmann's canals, with a diameter of about 50 microm, which contains a.o. blood vessels and nerves. The smaller is the system consisting of the canaliculi and lacunae: the canaliculi are at the submicron level and house the protrusions of the osteocytes. When bone is differentially loaded, fluids within the solid matrix sustain a pressure gradient that drives a flow. It is generally assumed that the flow of extracellular fluid around osteocytes plays an important role not only in the nutrition of these cells, but also in the bone's mechanosensory system. The interaction between the deformation of the bone matrix and the flow of fluid can be modelled using Biot's theory of poroelasticity. However, due to the inhomogeneity of the bone matrix and the scale of the porosities, it is not possible to experimentally determine all the parameters that are needed for numerical implementation. The purpose of this paper is to derive these parameters using composite modelling and experimental data from literature. A full set of constants is estimated for a linear isotropic description of cortical bone as a two-level porous medium. Bone, however, has a wide variety of mechanical and structural properties; with the theoretical relationships described in this note, poroelastic parameters can be derived for other bone types using their specific experimental data sets.

  16. Cavitary osteomyelitis treated by fragmentary cortical bone transportation.

    PubMed

    Aronson, J

    1992-07-01

    Fragmentary cortical bone transportation can be used to fill large gaps in chronic cavitary osteomyelitis when standard techniques have failed. A low-energy corticotomy can create a loose fragment of cortex with periosteal attachments and surface blood supply still intact. This "vital" fragment can be gradually pulled across a defect within a bone to restore the integrity of the bone segment by distraction osteogenesis. The biologic principles for successful distraction osteogenesis by this innovative technique are illustrated in a 41-year-old man with chronic cavitary (150 cc) (four years) osteomyelitis refractory to multiple debridements, Papineau grafting, gentamicin beads, and tricalcium phosphate.

  17. Investigation of hyperelastic models for nonlinear elastic behavior of demineralized and deproteinized bovine cortical femur bone.

    PubMed

    Hosseinzadeh, M; Ghoreishi, M; Narooei, K

    2016-06-01

    In this study, the hyperelastic models of demineralized and deproteinized bovine cortical femur bone were investigated and appropriate models were developed. Using uniaxial compression test data, the strain energy versus stretch was calculated and the appropriate hyperelastic strain energy functions were fitted on data in order to calculate the material parameters. To obtain the mechanical behavior in other loading conditions, the hyperelastic strain energy equations were investigated for pure shear and equi-biaxial tension loadings. The results showed the Mooney-Rivlin and Ogden models cannot predict the mechanical response of demineralized and deproteinized bovine cortical femur bone accurately, while the general exponential-exponential and general exponential-power law models have a good agreement with the experimental results. To investigate the sensitivity of the hyperelastic models, a variation of 10% in material parameters was performed and the results indicated an acceptable stability for the general exponential-exponential and general exponential-power law models. Finally, the uniaxial tension and compression of cortical femur bone were studied using the finite element method in VUMAT user subroutine of ABAQUS software and the computed stress-stretch curves were shown a good agreement with the experimental data. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Cortical and trabecular bone adaptation to incremental load magnitudes using the mouse tibial axial compression loading model.

    PubMed

    Weatherholt, Alyssa M; Fuchs, Robyn K; Warden, Stuart J

    2013-01-01

    The mouse tibial axial compression loading model has recently been described to allow simultaneous exploration of cortical and trabecular bone adaptation within the same loaded element. However, the model frequently induces cortical woven bone formation and has produced inconsistent results with regards to trabecular bone adaptation. The aim of this study was to investigate bone adaptation to incremental load magnitudes using the mouse tibial axial compression loading model, with the ultimate goal of revealing a load that simultaneously induced lamellar cortical and trabecular bone adaptation. Adult (16 weeks old) female C57BL/6 mice were randomly divided into three load magnitude groups (5, 7 and 9N), and had their right tibia axially loaded using a continuous 2-Hz haversine waveform for 360 cycles/day, 3 days/week for 4 consecutive weeks. In vivo peripheral quantitative computed tomography was used to longitudinally assess midshaft tibia cortical bone adaptation, while ex vivo micro-computed tomography and histomorphometry were used to assess both midshaft tibia cortical and proximal tibia trabecular bone adaptation. A dose response to loading magnitude was observed within cortical bone, with increasing load magnitude inducing increasing levels of lamellar cortical bone adaptation within the upper two thirds of the tibial diaphysis. Greatest cortical bone adaptation was observed at the midshaft where there was a 42% increase in estimated mechanical properties (polar moment of inertia) in the highest (9N) load group. A dose response to load magnitude was not clearly evident within trabecular bone, with only the highest load (9N) being able to induce measureable adaptation (31% increase in trabecular bone volume fraction at the proximal tibia). The ultimate finding was that a load of 9N (engendering a tensile strain of 1833 με on medial surface of the midshaft tibia) was able to simultaneously induce measurable lamellar cortical and trabecular bone adaptation

  19. Drill wear monitoring in cortical bone drilling.

    PubMed

    Staroveski, Tomislav; Brezak, Danko; Udiljak, Toma

    2015-06-01

    Medical drills are subject to intensive wear due to mechanical factors which occur during the bone drilling process, and potential thermal and chemical factors related to the sterilisation process. Intensive wear increases friction between the drill and the surrounding bone tissue, resulting in higher drilling temperatures and cutting forces. Therefore, the goal of this experimental research was to develop a drill wear classification model based on multi-sensor approach and artificial neural network algorithm. A required set of tool wear features were extracted from the following three types of signals: cutting forces, servomotor drive currents and acoustic emission. Their capacity to classify precisely one of three predefined drill wear levels has been established using a pattern recognition type of the Radial Basis Function Neural Network algorithm. Experiments were performed on a custom-made test bed system using fresh bovine bones and standard medical drills. Results have shown high classification success rate, together with the model robustness and insensitivity to variations of bone mechanical properties. Features extracted from acoustic emission and servomotor drive signals achieved the highest precision in drill wear level classification (92.8%), thus indicating their potential in the design of a new type of medical drilling machine with process monitoring capabilities. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

  20. Re-evaluating the toughness of human cortical bone.

    PubMed

    Yang, Q D; Cox, B N; Nalla, R K; Ritchie, R O

    2006-06-01

    Data for fracture in human humeral cortical bone are re-analyzed to assess the validity for this material of linear-elastic fracture mechanics (LEFM), which is the standard method of analyzing toughness and one basis for analyzing clinical data relating to bone quality. A nonlinear fracture model, which is based on representing the damage zone in the bone by a cohesive model, is calibrated against a number of sets of test data for normal (not diseased or aged) human cortical bone taken from cadavers. The data consist of load vs. load-point displacement measurements from standard compact-tension fracture tests. Conventional LEFM is unable to account for the shape of the load-displacement curves, but the nonlinear model overcomes this deficiency. Calibration of the nonlinear model against one data curve leads to predictions of the peak load and the displacement to peak load for two other data curves that are, for this limited test set, more accurate than those made using LEFM. Furthermore, prior observations of damage mechanisms in bone are incompatible with the modeling assumption of LEFM that all nonlinearity is confined to a zone much smaller than the specimen and the crack length. The predictions of the cohesive model and the prior observations concur that the length of the nonlinear zone in human cortical bone varies in the range 3-10 mm, which is comparable to or larger than naturally-occurring bones and the specimens used to test them. We infer that LEFM is not an accurate model for cortical bone. The fracture toughness of bone deduced via LEFM from test data will not generally be a material constant, but will take different values for different crack lengths and test configurations. The accuracy of using LEFM or single-parameter fracture toughness for analyzing the significance of data from clinical studies is called into question. The nonlinear cohesive zone model is proposed to be a more accurate model of bone and the traction-displacement or cohesive law

  1. Machining characteristics of the haversian and plexiform components of bovine cortical bone.

    PubMed

    Conward, Michael; Samuel, Johnson

    2016-07-01

    This paper investigates the characteristic differences observed while machining the haversian and plexiform components of a bovine cortical femoral bone. To this end micro-milling slotting experiments are performed on both the components by varying both the cutting velocity and the feed-per-tooth values. The scale of machining is chosen specifically to ensure sensitivity to the microstructural variations in the bone. The material properties of the microstructural components and their size-scale relative to the feed-per-tooth values are seen to dictate the failure mechanisms encountered during machining. The cutting force, surface roughness, and tool wear are all uniquely affected by the plexiform and haversian components of the cortical bone. In general, plexiform bone requires a higher cutting force than the haversian bone. While a higher cutting velocity can lower the surface roughness of haversian bone, it typically results in the most surface damage. The cutting force and surface roughness values for both the components show strain rate sensitivity. The tool wear is seen to be the highest while cutting parallel to the lamellar structures seen in the plexiform bone.

  2. Evaluation of trabecular bone patterns on dental radiographic images: influence of cortical bone

    NASA Astrophysics Data System (ADS)

    Amouriq, Yves; Evenou, Pierre; Arlicot, Aurore; Normand, Nicolas; Layrolle, Pierre; Weiss, Pierre; Guédon, Jean-Pierre

    2010-03-01

    For some authors trabecular bone is highly visible in intraoral radiographs. For other authors, the observed intrabony trabecular pattern is a representation of only the endosteal surface of cortical bone, not of intermedullary striae. The purpose of this preliminary study was to investigate the true anatomical structures that are visible in routine dental radiographs and classically denoted trabecular bone. This is a major point for bone texture analysis on radiographs. Computed radiography (CR) images of dog mandible section in molar region were compared with simulations calculated from high-resolution micro-CT volumes. Calculated simulations were obtained using the Mojette Transform. By digitally editing the CT volume, the simulations were separated into trabecular and cortical components into a region of interest. Different images were compared and correlated, some bone micro-architecture parameters calculated. A high correlation was found between computed radiographs and calculated simulations from micro-CT. The Mojette transform was successful to obtain high quality images. Cortical bone did not contribute to change in a major way simulated images. These first results imply that intrabony trabecular pattern observed on radiographs can not only be a representation of the cortical bone endosteal surface and that trabecular bone is highly visible in intraoral radiographs.

  3. Integration of dense HA rods into cortical bone.

    PubMed

    Benhayoune, H; Jallot, E; Laquerriere, P; Balossier, G; Bonhomme, P; Frayssinet, P

    2000-02-01

    HA ceramics are daily used in human surgery for bone healing partly due to their ability to integrate into bone. They are generally used under a macroporous form. The behaviour of dense HA after implantation is not so well known. We implanted within cortical sheep femurs dense pure HA-ceramics cylinders for periods from 2 weeks to 18 months. The samples were then sectioned and examined using back-scattered and secondary SEM and the interface was analysed using EDS. Histomorphometry measurement was also performed using an image analysis device coupled to a light microscope. It appeared that the cylinders were in direct contact with immature bone after three weeks. The bone maturated within three months. The implant surface showed moderate signs of resorption and some grains were released from the surface. The resorption zone was only a few microm thick after 18 months. The bulk ceramic contained default zones of increased porosity. They can constitute fragile zone when located close to the surface in which the resorption rate is increased. We conclude that dense pure HA is poorly degraded when implanted in cortical bone. Degradation depends on the defaults found on the ceramic structure and the remodelling of bone surrounding the material.

  4. Adaptations in tibial cortical thickness and total volumetric bone density in postmenopausal South Asian women with small bone size.

    PubMed

    Darling, Andrea L; Hakim, Ohood A; Horton, Khim; Gibbs, Michelle A; Cui, Liang; Berry, Jacqueline L; Lanham-New, Susan A; Hart, Kathryn H

    2013-07-01

    There is some evidence that South Asian women may have an increased risk of osteoporosis compared with Caucasian women, although whether South Asians are at increased risk of fracture is not clear. It is unknown whether older South Asian women differ from Caucasian women in bone geometry. This is the first study, to the authors' knowledge, to use peripheral Quantitative Computed Tomography (pQCT) to measure radial and tibial bone geometry in postmenopausal South Asian women. In comparison to Caucasian women, Asian women had smaller bone size at the 4% (-18% p<0.001) and 66% radius (-15% p=0.04) as well as increased total density at the 4% (+13% p=0.01) radius. For the tibia, they had a smaller bone size at the 4% (-16% p=0.005) and 14% (-38% p=0.002) sites. Also, Asians had increased cortical thickness (-17% p=0.04) at the 38% tibia, (in proportion to bone size (-30% p=0.003)). Furthermore, at the 4% and 14% tibia there were increased total densities (+12% to +29% p<0.01) and at the 14% tibia there was increased cortical density (+5% p=0.005) in Asians. These differences at the 14% and 38% (but not 4%) remained statistically significant after adjustment for Body Mass Index (BMI). These adaptations are similar to those seen previously in Chinese women. Asian women had reduced strength at the radius and tibia, evidenced by the 20-40% reduction in both polar Strength Strain Index (SSIp) and fracture load (under bending). Overall, the smaller bone size in South Asians is likely to be detrimental to bone strength, despite some adaptations in tibial cortical thickness and tibial and radial density which may partially compensate for this.

  5. Cortical bone fracture analysis using XFEM - case study.

    PubMed

    Idkaidek, Ashraf; Jasiuk, Iwona

    2016-06-11

    We aim to achieve an accurate simulation of human cortical bone fracture using the extended finite element method within a commercial finite element software abaqus. A two-dimensional unit cell model of cortical bone is built based on a microscopy image of the mid-diaphysis of tibia of a 70-year-old human male donor. Each phase of this model, an interstitial bone, a cement line, and an osteon, are considered linear elastic and isotropic with material properties obtained by nanoindentation, taken from literature. The effect of using fracture analysis methods (cohesive segment approach versus linear elastic fracture mechanics approach), finite element type, and boundary conditions (traction, displacement, and mixed) on cortical bone crack initiation and propagation are studied. In this study cohesive segment damage evolution for a traction separation law based on energy and displacement is used. In addition, effects of the increment size and mesh density on analysis results are investigated. We find that both cohesive segment and linear elastic fracture mechanics approaches within the extended finite element method can effectively simulate cortical bone fracture. Mesh density and simulation increment size can influence analysis results when employing either approach, and using finer mesh and/or smaller increment size does not always provide more accurate results. Both approaches provide close but not identical results, and crack propagation speed is found to be slower when using the cohesive segment approach. Also, using reduced integration elements along with the cohesive segment approach decreases crack propagation speed compared with using full integration elements. Copyright © 2016 John Wiley & Sons, Ltd.

  6. Low-amplitude, broad-frequency vibration effects on cortical bone formation in mice.

    PubMed

    Castillo, Alesha B; Alam, Imranul; Tanaka, Shigeo M; Levenda, Jeffery; Li, Jiliang; Warden, Stuart J; Turner, Charles H

    2006-11-01

    Mechanical loading of the skeleton is necessary to maintain bone structure and strength. Large amplitude strains associated with vigorous activity typically result in the greatest osteogenic response; however, data suggest that low-amplitude, broad-frequency vibration results in new bone formation and may enhance adaptation through a stochastic resonance (SR) phenomenon. That is, random noise may maximally enhance bone formation to a known osteogenic stimulus. The aims of this study were to (1) assess the ability of different vibration signals to enhance cortical bone formation during short- and long-term loading and (2) determine whether vibration could effect SR in bone. Two studies were completed wherein several osteogenic loading waveforms, with or without an additive low-amplitude, broad-frequency (0-50 Hz) vibration signal, were applied to the mouse ulna in axial compression. In study 1, mice were loaded short-term (30 s/day, 2 days) with either a carrier signal alone (1 or 2 N sine waveform), vibration signal alone [0.1 N or 0.3 N root mean square (RMS)] or combined carrier and vibration signal. In study 2, mice were loaded long-term (30 s/day, 3 days/week, 4 weeks) with a carrier signal alone (static or sine waveform), vibration signal alone (0.02 N, 0.04 N, 0.08 N or 0.25 N RMS) or combined carrier and vibration signal. Sequential calcein bone labels were administered at 2 and 4 days and at 4 and 29 days after the first day of loading in study 1 and 2, respectively; bone formation parameters and changes in geometry were measured. Combined application of the carrier and vibration signals in study 1 resulted in significantly greater bone formation than with either signal alone (P < 0.001); however, this increase was independently explained by increased strain levels associated with additive vibration. When load and strain levels were similar across loading groups in study 2, cortical bone formation and changes in geometry were not significantly altered by

  7. Heat accumulation during sequential cortical bone drilling.

    PubMed

    Palmisano, Andrew C; Tai, Bruce L; Belmont, Barry; Irwin, Todd A; Shih, Albert; Holmes, James R

    2016-03-01

    Significant research exists regarding heat production during single-hole bone drilling. No published data exist regarding repetitive sequential drilling. This study elucidates the phenomenon of heat accumulation for sequential drilling with both Kirschner wires (K wires) and standard two-flute twist drills. It was hypothesized that cumulative heat would result in a higher temperature with each subsequent drill pass. Nine holes in a 3 × 3 array were drilled sequentially on moistened cadaveric tibia bone kept at body temperature (about 37 °C). Four thermocouples were placed at the center of four adjacent holes and 2 mm below the surface. A battery-driven hand drill guided by a servo-controlled motion system was used. Six samples were drilled with each tool (2.0 mm K wire and 2.0 and 2.5 mm standard drills). K wire drilling increased temperature from 5 °C at the first hole to 20 °C at holes 6 through 9. A similar trend was found in standard drills with less significant increments. The maximum temperatures of both tools increased from <0.5 °C to nearly 13 °C. The difference between drill sizes was found to be insignificant (P > 0.05). In conclusion, heat accumulated during sequential drilling, with size difference being insignificant. K wire produced more heat than its twist-drill counterparts. This study has demonstrated the heat accumulation phenomenon and its significant effect on temperature. Maximizing the drilling field and reducing the number of drill passes may decrease bone injury.

  8. Bone strain magnitude is correlated with bone strain rate in tetrapods: implications for models of mechanotransduction.

    PubMed

    Aiello, B R; Iriarte-Diaz, J; Blob, R W; Butcher, M T; Carrano, M T; Espinoza, N R; Main, R P; Ross, C F

    2015-07-07

    Hypotheses suggest that structural integrity of vertebrate bones is maintained by controlling bone strain magnitude via adaptive modelling in response to mechanical stimuli. Increased tissue-level strain magnitude and rate have both been identified as potent stimuli leading to increased bone formation. Mechanotransduction models hypothesize that osteocytes sense bone deformation by detecting fluid flow-induced drag in the bone's lacunar-canalicular porosity. This model suggests that the osteocyte's intracellular response depends on fluid-flow rate, a product of bone strain rate and gradient, but does not provide a mechanism for detection of strain magnitude. Such a mechanism is necessary for bone modelling to adapt to loads, because strain magnitude is an important determinant of skeletal fracture. Using strain gauge data from the limb bones of amphibians, reptiles, birds and mammals, we identified strong correlations between strain rate and magnitude across clades employing diverse locomotor styles and degrees of rhythmicity. The breadth of our sample suggests that this pattern is likely to be a common feature of tetrapod bone loading. Moreover, finding that bone strain magnitude is encoded in strain rate at the tissue level is consistent with the hypothesis that it might be encoded in fluid-flow rate at the cellular level, facilitating bone adaptation via mechanotransduction.

  9. Bone strain magnitude is correlated with bone strain rate in tetrapods: implications for models of mechanotransduction

    PubMed Central

    Aiello, B. R.; Iriarte-Diaz, J.; Blob, R. W.; Butcher, M. T.; Carrano, M. T.; Espinoza, N. R.; Main, R. P.; Ross, C. F.

    2015-01-01

    Hypotheses suggest that structural integrity of vertebrate bones is maintained by controlling bone strain magnitude via adaptive modelling in response to mechanical stimuli. Increased tissue-level strain magnitude and rate have both been identified as potent stimuli leading to increased bone formation. Mechanotransduction models hypothesize that osteocytes sense bone deformation by detecting fluid flow-induced drag in the bone's lacunar–canalicular porosity. This model suggests that the osteocyte's intracellular response depends on fluid-flow rate, a product of bone strain rate and gradient, but does not provide a mechanism for detection of strain magnitude. Such a mechanism is necessary for bone modelling to adapt to loads, because strain magnitude is an important determinant of skeletal fracture. Using strain gauge data from the limb bones of amphibians, reptiles, birds and mammals, we identified strong correlations between strain rate and magnitude across clades employing diverse locomotor styles and degrees of rhythmicity. The breadth of our sample suggests that this pattern is likely to be a common feature of tetrapod bone loading. Moreover, finding that bone strain magnitude is encoded in strain rate at the tissue level is consistent with the hypothesis that it might be encoded in fluid-flow rate at the cellular level, facilitating bone adaptation via mechanotransduction. PMID:26063842

  10. Insulin Resistance Is Associated With Smaller Cortical Bone Size in Nondiabetic Men at the Age of Peak Bone Mass.

    PubMed

    Verroken, Charlotte; Zmierczak, Hans-Georg; Goemaere, Stefan; Kaufman, Jean-Marc; Lapauw, Bruno

    2017-06-01

    In type 2 diabetes mellitus, fracture risk is increased despite preserved areal bone mineral density. Although this apparent paradox may in part be explained by insulin resistance affecting bone structure and/or material properties, few studies have investigated the association between insulin resistance and bone geometry. We aimed to explore this association in a cohort of nondiabetic men at the age of peak bone mass. Nine hundred ninety-six nondiabetic men aged 25 to 45 years were recruited in a cross-sectional, population-based sibling pair study at a university research center. Insulin resistance was evaluated using the homeostasis model assessment of insulin resistance (HOMA-IR), with insulin and glucose measured from fasting serum samples. Bone geometry was assessed using peripheral quantitative computed tomography at the distal radius and the radial and tibial shafts. In age-, height-, and weight-adjusted analyses, HOMA-IR was inversely associated with trabecular area at the distal radius and with cortical area, periosteal and endosteal circumference, and polar strength strain index at the radial and tibial shafts (β ≤ -0.13, P < 0.001). These associations remained essentially unchanged after additional adjustment for dual-energy X-ray absorptiometry-derived body composition, bone turnover markers, muscle size or function measurements, or adiponectin, leptin, insulin-like growth factor 1, or sex steroid levels. In this cohort of nondiabetic men at the age of peak bone mass, insulin resistance is inversely associated with trabecular and cortical bone size. These associations persist after adjustment for body composition, muscle size or function, or sex steroid levels, suggesting an independent effect of insulin resistance on bone geometry.

  11. Connection between elastic and electrical properties of cortical bone.

    PubMed

    Gao, X; Sevostianov, I

    2016-03-21

    The paper focuses on the connection between elastic and electrical properties of cortical bone. Both these properties are governed by microstructure that consists of several pore systems filled with mechanically soft and electrically conductive tissue. Microstructural changes induced by aging, various diseases, microgravity conditions etc. lead to variation in both properties. The paper address the problem of evaluation of the changes in mechanical performance (decrease in Young׳s moduli) via monitoring electrical conductivity. The theoretical results are verified experimentally.

  12. Are uniform regional safety factors an objective of adaptive modeling/remodeling in cortical bone?

    PubMed

    Skedros, John G; Dayton, Michael R; Sybrowsky, Christian L; Bloebaum, Roy D; Bachus, Kent N

    2003-07-01

    It has been hypothesized that a major objective of morphological adaptation in limb-bone diaphyses is the achievement of uniform regional safety factors between discrete cortical locations (e.g. between cranial and caudal cortices at mid-diaphysis). This hypothesis has been tested, and appears to be supported in the diaphyses of ovine and equine radii. The present study more rigorously examined this question using the equine third metacarpal (MC3), which has had functionally generated intracortical strains estimated by a sophisticated finite element model. Mechanical properties of multiple mid-diaphyseal specimens were evaluated in both tension and compression, allowing for testing of habitually tensed or compressed regions in their respective habitual loading mode ("strain-mode-specific" loading). Elastic modulus, and yield and ultimate strength and strain, were correlated with in vivo strain data from a previously published finite element model. Mechanical tests revealed minor variations in elastic modulus, and yield and ultimate strength in both tension and compression loading, while physiological strains varied significantly between the cortices. Contrary to the hypothesis of uniform safety factors, the MC3 has a broad range of tension (caudo-medial, 4.0; cranio-lateral, 37.7) and compression (caudo-medial, 5.7; cranio-lateral, 68.9) safety factors.

  13. Comparative study between cortical bone graft versus bone dust for reconstruction of cranial burr holes.

    PubMed

    Worm, Paulo V; Ferreira, Nelson P; Faria, Mario B; Ferreira, Marcelo P; Kraemer, Jorge L; Collares, Marcus V M

    2010-12-22

    As a consequence of the progressive evolution of neurosurgical techniques, there has been increasing concern with the esthetic aspects of burr holes. Therefore, the objective of this study was to compare the use of cortical bone graft and bone dust for correcting cranial deformities caused by neurosurgical trephines. Twenty-three patients were enrolled for cranial burr hole reconstruction with a 1-year follow-up. A total of 108 burr holes were treated; 36 burr holes were reconstructed with autogenous cortical bone discs (33.3%), and the remaining 72 with autogenous wet bone powder (66.6%). A trephine was specifically designed to produce this coin-shaped bone plug of 14 mm in diameter, which fit perfectly over the burr holes. The reconstructions were studied 12 months after the surgical procedure, using three-dimensional quantitative computed tomography. Additionally, general and plastic surgeons blinded for the study evaluated the cosmetic results of those areas, attributing scores from 0 to 10. The mean bone densities were 987.95 ± 186.83 Hounsfield units (HU) for bone fragment and 473.55 ± 220.34 HU for bone dust (P < 0.001); the mean cosmetic scores were 9.5 for bone fragment and 5.7 for bone dust (P < 0.001). The use of autologous bone discs showed better results than bone dust for the reconstruction of cranial burr holes because of their lower degree of bone resorption and, consequently, better cosmetic results. The lack of donor site morbidity associated with procedural low cost qualifies the cortical autograft as the first choice for correcting cranial defects created by neurosurgical trephines.

  14. Comparative study between cortical bone graft versus bone dust for reconstruction of cranial burr holes

    PubMed Central

    Worm, Paulo V.; Ferreira, Nelson P.; Faria, Mario B.; Ferreira, Marcelo P.; Kraemer, Jorge L.; Collares, Marcus V. M.

    2010-01-01

    Background: As a consequence of the progressive evolution of neurosurgical techniques, there has been increasing concern with the esthetic aspects of burr holes. Therefore, the objective of this study was to compare the use of cortical bone graft and bone dust for correcting cranial deformities caused by neurosurgical trephines. Methods: Twenty-three patients were enrolled for cranial burr hole reconstruction with a 1-year follow-up. A total of 108 burr holes were treated; 36 burr holes were reconstructed with autogenous cortical bone discs (33.3%), and the remaining 72 with autogenous wet bone powder (66.6%). A trephine was specifically designed to produce this coin-shaped bone plug of 14 mm in diameter, which fit perfectly over the burr holes. The reconstructions were studied 12 months after the surgical procedure, using three-dimensional quantitative computed tomography. Additionally, general and plastic surgeons blinded for the study evaluated the cosmetic results of those areas, attributing scores from 0 to 10. Results: The mean bone densities were 987.95 ± 186.83 Hounsfield units (HU) for bone fragment and 473.55 ± 220.34 HU for bone dust (P < 0.001); the mean cosmetic scores were 9.5 for bone fragment and 5.7 for bone dust (P < 0.001). Conclusions: The use of autologous bone discs showed better results than bone dust for the reconstruction of cranial burr holes because of their lower degree of bone resorption and, consequently, better cosmetic results. The lack of donor site morbidity associated with procedural low cost qualifies the cortical autograft as the first choice for correcting cranial defects created by neurosurgical trephines. PMID:21206899

  15. Repair of Microdamage in Osteonal Cortical Bone Adjacent to Bone Screw

    PubMed Central

    Wang, Lei; Ye, Tingjun; Deng, Lianfu; Shao, Jin; Qi, Jin; Zhou, Qi; Wei, Li; Qiu, Shijing

    2014-01-01

    Up to date, little is known about the repair mode of microdamage in osteonal cortical bone resulting from bone screw implantation. In this study, self-tapping titanium cortical bone screws were inserted into the tibial diaphyses of 24 adult male rabbits. The animals were sacrificed at 1 day, 2 weeks, 1 month and 2 months after surgery. Histomorphometric measurement and confocal microscopy were performed on basic fuchsin stained bone sections to examine the morphological characteristics of microdamage, bone resorption activity and spatial relationship between microdamage and bone resorption. Diffuse and linear cracks were coexisted in peri-screw bone. Intracortical bone resorption was significantly increased 2 weeks after screw installation and reach to the maximum at 1 month. There was no significant difference in bone resorption between 1-month and 2-months groups. Microdamage was significantly decreased within 1 month after surgery. Bone resorption was predisposed to occur in the region of <100 µm from the bone-screw interface, where had extensive diffuse damage mixed with linear cracks. Different patterns of resorption cavities appeared in peri-screw bone. These data suggest that 1) the complex microdamage composed of diffuse damage and linear cracks is a strong stimulator for initiating targeted bone remodeling; 2) bone resorption activities taking place on the surfaces of differently oriented Haversian and Volkmann canals work in a team for the repair of extensive microdamage; 3) targeted bone remodeling is a short-term reaction to microdamage and thereby it may not be able to remove all microdamage resulting from bone screw insertion. PMID:24586702

  16. Time-lapsed assessment of microcrack initiation and propagation in murine cortical bone at submicrometer resolution.

    PubMed

    Voide, R; Schneider, P; Stauber, M; Wyss, P; Stampanoni, M; Sennhauser, U; van Lenthe, G H; Müller, R

    2009-08-01

    The strength of bone tissue is not only determined by its mass, but also by other properties usually referred to as bone quality, such as microarchitecture, distribution of bone cells, or microcracks and damage. It has been hypothesized that the bone ultrastructure affects microcrack initiation and propagation. Due to its high resolution, bone assessment by means of synchrotron radiation (SR)-based computed tomography (CT) allows unprecedented three-dimensional (3D) and non-invasive insights into ultrastructural bone phenotypes, such as the canal network and the osteocyte lacunar system. The aims of this study were to describe the initiation and propagation of microcracks and their relation with these ultrastructural phenotypes. To this end, femora from the two genetically distinct inbred mouse strains C3H/He (C3H) and C57BL/6 (B6) were loaded axially under compression, from 0% strain to failure, with 1% strain steps. Between each step, a high-resolution 3D image (700 nm nominal resolution) was acquired at the mid-diaphysis using SR CT for characterization and quantitative analysis of the intracortical porosity, namely the bone canal network, the osteocyte lacunar system and the emerging microcracks. For C3H mice, the canal, lacunar, and microcrack volume densities accounted typically for 1.91%, 2.11%, and 0.27% of the cortical total volume at 2% apparent strain, respectively. Due to its 3D nature, SR CT allowed to visualize and quantify also the volumetric extent of microcracks. At 2% apparent strain, the average microcrack thickness for both mouse strains was 2.0 microm for example. Microcracks initiated at canal and at bone surfaces, whereas osteocyte lacunae provided guidance to the microcracks. Moreover, we observed that microcracks could appear as linear cracks in one plane, but as diffuse cracks in a perpendicular plane. Finally, SR CT images permitted visualization of uncracked ligament bridging, which is thought to be of importance in bone toughening

  17. Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone

    NASA Astrophysics Data System (ADS)

    Gu, Chunju; Katti, Dinesh R.; Katti, Kalpana S.

    2013-02-01

    Chemical pretreatment has been the prevailing sample preparation procedure for infrared (IR) spectroscopic studies on bone. However, experiments have indicated that chemical pretreatment can potentially affect the interactions between the components. Typically the IR techniques have involved transmission experiments. Here we report experimental studies using photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). As a nondestructive technique, PA-FTIR can detect absorbance spectrum from a sample at controllable sampling depth and with little or no sample preparation. Additionally, the coupling inert gas, helium, which is utilized in the PA-FTIR system, can inhibit bacteria growth of bone by displacing oxygen. Therefore, we used this technique to study the undisturbed human cortical bone. It is found that photoacoustic mode (linear-scan, LS-PA-FTIR) can obtain basically similar spectra of bone as compared to the traditional transmission mode, but it seems more sensitive to amide III and ν2 carbonate bands. The ν3 phosphate band is indicative of detailed mineral structure and symmetry of native bone. The PA-FTIR depth profiling experiments on human cortical bone also indicate the influence of water on OH band and the cutting effects on amide I and mineral bands. Our results indicate that phosphate ion geometry appears less symmetric in its undisturbed state as detected by the PA-FTIR as compared to higher symmetry observed using transmission techniques on disturbed samples. Moreover, the PA-FTIR spectra indicate a band at 1747 cm-1 possibly resulting from Cdbnd O stretching of lipids, cholesterol esters, and triglycerides from the arteries. Comparison of the spectra in transverse and longitudinal cross-sections demonstrates that, the surface area of the longitudinal section bone appears to have more organic matrix exposed and with higher mineral stoichiometry.

  18. Analyzing the anisotropic Hooke's law for children's cortical bone.

    PubMed

    Lefèvre, Emmanuelle; Lasaygues, Philippe; Baron, Cécile; Payan, Cédric; Launay, Franck; Follet, Hélène; Pithioux, Martine

    2015-09-01

    Child cortical bone tissue is rarely studied because of the difficulty of obtaining samples. Yet the preparation and ultrasonic characterization of the small samples available, while challenging, is one of the most promising ways of obtaining information on the mechanical behavior of non-pathological children׳s bone. We investigated children׳s cortical bone obtained from chirurgical waste. 22 fibula or femur samples from 21 children (1-18 years old, mean age: 9.7±5.8 years old) were compared to 16 fibula samples from 16 elderly patients (50-95 years old, mean age: 76.2±13.5 years old). Stiffness coefficients were evaluated via an ultrasonic method and anisotropy ratios were calculated as the ratio of C33/C11, C33/C22 and C11/C22. Stiffness coefficients were highly correlated with age in children (R>0.56, p<0.01). No significant difference was found between C11 and C22 for either adult or child bone (p>0.5), nor between C44 and C55 (p>0.5). We observe a transverse isotropy with C33>C22=C11>C44C55>C66. For both groups, we found no correlation between age and anisotropy ratios. This study offers the first complete analysis of stiffness coefficients in the three orthogonal bone axes in children, giving some indication of how bone anisotropy is related to age. Future perspectives include studying the effect of the structure and composition of bone on its mechanical behavior. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Individual-specific multi-scale finite element simulation of cortical bone of human proximal femur

    SciTech Connect

    Ascenzi, Maria-Grazia; Kardas, Dieter; Nackenhorst, Udo; Keyak, Joyce H.

    2013-07-01

    We present an innovative method to perform multi-scale finite element analyses of the cortical component of the femur using the individual’s (1) computed tomography scan; and (2) a bone specimen obtained in conjunction with orthopedic surgery. The method enables study of micro-structural characteristics regulating strains and stresses under physiological loading conditions. The analysis of the micro-structural scenarios that cause variation of strain and stress is the first step in understanding the elevated strains and stresses in bone tissue, which are indicative of higher likelihood of micro-crack formation in bone, implicated in consequent remodeling or macroscopic bone fracture. Evidence that micro-structure varies with clinical history and contributes in significant, but poorly understood, ways to bone function, motivates the method’s development, as does need for software tools to investigate relationships between macroscopic loading and micro-structure. Three applications – varying region of interest, bone mineral density, and orientation of collagen type I, illustrate the method. We show, in comparison between physiological loading and simple compression of a patient’s femur, that strains computed at the multi-scale model’s micro-level: (i) differ; and (ii) depend on local collagen-apatite orientation and degree of calcification. Our findings confirm the strain concentration role of osteocyte lacunae, important for mechano-transduction. We hypothesize occurrence of micro-crack formation, leading either to remodeling or macroscopic fracture, when the computed strains exceed the elastic range observed in micro-structural testing.

  20. Occlusal load distribution through the cortical and trabecular bone of the human mid-facial skeleton in natural dentition: a three-dimensional finite element study.

    PubMed

    Janovic, Aleksa; Saveljic, Igor; Vukicevic, Arso; Nikolic, Dalibor; Rakocevic, Zoran; Jovicic, Gordana; Filipovic, Nenad; Djuric, Marija

    2015-01-01

    Understanding of the occlusal load distribution through the mid-facial skeleton in natural dentition is essential because alterations in magnitude and/or direction of occlusal forces may cause remarkable changes in cortical and trabecular bone structure. Previous analyses by strain gauge technique, photoelastic and, more recently, finite element (FE) methods provided no direct evidence for occlusal load distribution through the cortical and trabecular bone compartments individually. Therefore, we developed an improved three-dimensional FE model of the human skull in order to clarify the distribution of occlusal forces through the cortical and trabecular bone during habitual masticatory activities. Particular focus was placed on the load transfer through the anterior and posterior maxilla. The results were presented in von Mises stress (VMS) and the maximum principal stress, and compared to the reported FE and strain gauge data. Our qualitative stress analysis indicates that occlusal forces distribute through the mid-facial skeleton along five vertical and two horizontal buttresses. We demonstrated that cortical bone has a priority in the transfer of occlusal load in the anterior maxilla, whereas both cortical and trabecular bone in the posterior maxilla are equally involved in performing this task. Observed site dependence of the occlusal load distribution may help clinicians in creating strategies for implantology and orthodontic treatments. Additionally, the magnitude of VMS in our model was significantly lower in comparison to previous FE models composed only of cortical bone. This finding suggests that both cortical and trabecular bone should be modeled whenever stress will be quantitatively analyzed.

  1. Quantitative Ultrashort Echo Time (UTE) MRI of Human Cortical Bone: Correlation with Porosity and Biomechanical Properties

    PubMed Central

    Bae, Won C.; Chen, Peter C.; Chung, Christine B.; Masuda, Koichi; D’Lima, Darryl; Du, Jiang

    2012-01-01

    In this study we describe the use of ultrashort echo time (UTE) magnetic resonance imaging (MRI) to evaluate short and long T2* components as well as the water content of cortical bone. Fourteen human cadaveric distal femur and proximal tibia were sectioned to produce 44 rectangular slabs of cortical bone for quantitative UTE MR imaging, micro computed tomography (μCT), and biomechanical testing. A two-dimensional (2D) UTE pulse sequence with a minimal nominal TE of 8 μs was used together with bi-component analysis to quantify the bound and free water in cortical bone using a clinical 3T scanner. Total water concentration was measured using a 3D UTE sequence together with a reference water phantom. UTE MR measures of water content (total, free and bound), T2* (short and long), and short and long T2* fractions were compared to porosity assessed with μCT, as well as elastic (modulus, yield stress and strain) and failure (ultimate stress, failure strain and energy) properties, using Pearson correlation. Porosity significantly correlated positively with total (R2=0.23; P<0.01) and free (R2=0.31; P<0.001) water content as well as long T2* fraction (R2=0.25; P<0.001), and negatively with short T2* fraction and short T2* (R2=0.24; P<0.01). Failure strain significantly correlated positively with short T2* (R2=0.29; P<0.001), ultimate stress significantly correlated negatively with total (R2=0.25; P<0.001) and bound (R2=0.22; P<0.01) water content, and failure energy significantly correlated positively with both short (R2=0.30; P<0.001) and long (R2=0.17; P<0.01) T2* values. These results suggest that UTE MR measures are sensitive to the structure and failure properties of human cortical bone, and may provide a novel way of evaluating cortical bone quality. PMID:22190232

  2. Bone morphology in 46 BXD recombinant inbred strains and femur-tibia correlation.

    PubMed

    Zhang, Yueying; Huang, Jinsong; Jiao, Yan; David, Valentin; Kocak, Mehmet; Roan, Esra; Di'Angelo, Denis; Lu, Lu; Hasty, Karen A; Gu, Weikuan

    2015-01-01

    We examined the bone properties of BXD recombinant inbred (RI) mice by analyzing femur and tibia and compared their phenotypes of different compartments. 46 BXD RI mouse strains were analyzed including progenitor C57BL/6J (n = 16) and DBA/2J (n = 15) and two first filial generations (D2B6F1 and B6D2F1). Strain differences were observed in bone quality and structural properties (P < 0.05) in each bone profile (whole bone, cortical bone, or trabecular bone). It is well known that skeletal phenotypes are largely affected by genetic determinants and genders, such as bone mineral density (BMD). While genetics and gender appear expectedly as the major determinants of bone mass and structure, significant correlations were also observed between femur and tibia. More importantly, positive and negative femur-tibia associations indicated that genetic makeup had an influence on skeletal integrity. We conclude that (a) femur-tibia association in bone morphological properties significantly varies from strain to strain, which may be caused by genetic differences among strains, and (b) strainwise variations were seen in bone mass, bone morphology, and bone microarchitecture along with bone structural property.

  3. Cancellous and cortical bone imaging by reflected tomography.

    PubMed

    Lasaygues, P; Lefebvre, J P

    2001-01-01

    This paper deals with the inverse scattering problem observed when ultrasonic waves are used to analyze biological media. The objective is to image cancellous and cortical bone by ultrasonic reflected tomography (URT). Because strong contrast and high absorbance bodies such as bones cannot be imaged at usual ultrasonic high frequencies (> 1 MHz), we adapted for low-frequency URT (< 1 MHz) our tomographic set-up and reconstruction and acquisition tools, previously developed for weakly scattered media. Indeed, when the frequency of the transducer decreases, the penetration length of the wave increases, which unfortunately makes resolution poor, inappropriate for bone imagery. To improve resolution, we extend the generalized inversion in the complementary bandwidth of the electro-acoustic set-up (Papoulis deconvolution). This resolution enhancement for human porous vertebrae and human and animal femur showed that high-resolution images can be obtained with low-frequency URT.

  4. Genetic Determinants of Trabecular and Cortical Volumetric Bone Mineral Densities and Bone Microstructure

    PubMed Central

    Kähönen, Mika; Raitakari, Olli; Laaksonen, Marika; Sievänen, Harri; Viikari, Jorma; Lyytikäinen, Leo-Pekka; Mellström, Dan; Karlsson, Magnus; Ljunggren, Östen; Grundberg, Elin; Kemp, John P.; Sayers, Adrian; Nethander, Maria; Evans, David M.; Vandenput, Liesbeth; Tobias, Jon H.; Ohlsson, Claes

    2013-01-01

    Most previous genetic epidemiology studies within the field of osteoporosis have focused on the genetics of the complex trait areal bone mineral density (aBMD), not being able to differentiate genetic determinants of cortical volumetric BMD (vBMD), trabecular vBMD, and bone microstructural traits. The objective of this study was to separately identify genetic determinants of these bone traits as analysed by peripheral quantitative computed tomography (pQCT). Separate GWA meta-analyses for cortical and trabecular vBMDs were performed. The cortical vBMD GWA meta-analysis (n = 5,878) followed by replication (n = 1,052) identified genetic variants in four separate loci reaching genome-wide significance (RANKL, rs1021188, p = 3.6×10−14; LOC285735, rs271170, p = 2.7×10−12; OPG, rs7839059, p = 1.2×10−10; and ESR1/C6orf97, rs6909279, p = 1.1×10−9). The trabecular vBMD GWA meta-analysis (n = 2,500) followed by replication (n = 1,022) identified one locus reaching genome-wide significance (FMN2/GREM2, rs9287237, p = 1.9×10−9). High-resolution pQCT analyses, giving information about bone microstructure, were available in a subset of the GOOD cohort (n = 729). rs1021188 was significantly associated with cortical porosity while rs9287237 was significantly associated with trabecular bone fraction. The genetic variant in the FMN2/GREM2 locus was associated with fracture risk in the MrOS Sweden cohort (HR per extra T allele 0.75, 95% confidence interval 0.60–0.93) and GREM2 expression in human osteoblasts. In conclusion, five genetic loci associated with trabecular or cortical vBMD were identified. Two of these (FMN2/GREM2 and LOC285735) are novel bone-related loci, while the other three have previously been reported to be associated with aBMD. The genetic variants associated with cortical and trabecular bone parameters differed, underscoring the complexity of the genetics of bone parameters. We propose that a genetic

  5. Inhibition of cortical and trabecular bone formation in the long bones of immobilized monkeys

    NASA Technical Reports Server (NTRS)

    Wronski, T. J.; Morey, E. R.

    1983-01-01

    Tetracycline derivatives are administered on three separate occasions to label the sites of bone formation. Determinations are made of the tetracycline-labeling frequency and mineral apposition rate of osteons and trabecular bone surfaces in the humerus and femur. The inhibition of bone formation induced by immobilization is found to be more pronounced in trabecular bone. The immobilized monkeys exhibit a moderate, but statistically nonsignificant, reduction in the percentage of osteons forming bone. Conversely, the dramatic decline in the percentage of trabecular surfaces undergoing bone formation in the monkeys is found to be highly significant. The diminished rate of mineral apposition in osteons is seen as suggesting that osteoblastic activity is impaired in cortical bone during immobilization.

  6. WNT16 Influences Bone Mineral Density, Cortical Bone Thickness, Bone Strength, and Osteoporotic Fracture Risk

    PubMed Central

    Eriksson, Joel; Paternoster, Lavinia; Yerges-Armstrong, Laura M.; Lehtimäki, Terho; Bergström, Ulrica; Kähönen, Mika; Leo, Paul J.; Raitakari, Olli; Laaksonen, Marika; Nicholson, Geoffrey C.; Viikari, Jorma; Ladouceur, Martin; Lyytikäinen, Leo-Pekka; Medina-Gomez, Carolina; Rivadeneira, Fernando; Prince, Richard L.; Sievanen, Harri; Leslie, William D.; Mellström, Dan; Eisman, John A.; Movérare-Skrtic, Sofia; Goltzman, David; Hanley, David A.; Jones, Graeme; St. Pourcain, Beate; Xiao, Yongjun; Timpson, Nicholas J.; Smith, George Davey; Reid, Ian R.; Ring, Susan M.; Sambrook, Philip N.; Karlsson, Magnus; Dennison, Elaine M.; Kemp, John P.; Danoy, Patrick; Sayers, Adrian; Wilson, Scott G.; Nethander, Maria; McCloskey, Eugene; Vandenput, Liesbeth; Eastell, Richard; Liu, Jeff; Spector, Tim; Mitchell, Braxton D.; Streeten, Elizabeth A.; Brommage, Robert; Pettersson-Kymmer, Ulrika; Brown, Matthew A.; Ohlsson, Claes; Richards, J. Brent; Lorentzon, Mattias

    2012-01-01

    We aimed to identify genetic variants associated with cortical bone thickness (CBT) and bone mineral density (BMD) by performing two separate genome-wide association study (GWAS) meta-analyses for CBT in 3 cohorts comprising 5,878 European subjects and for BMD in 5 cohorts comprising 5,672 individuals. We then assessed selected single-nucleotide polymorphisms (SNPs) for osteoporotic fracture in 2,023 cases and 3,740 controls. Association with CBT and forearm BMD was tested for ∼2.5 million SNPs in each cohort separately, and results were meta-analyzed using fixed effect meta-analysis. We identified a missense SNP (Thr>Ile; rs2707466) located in the WNT16 gene (7q31), associated with CBT (effect size of −0.11 standard deviations [SD] per C allele, P = 6.2×10−9). This SNP, as well as another nonsynonymous SNP rs2908004 (Gly>Arg), also had genome-wide significant association with forearm BMD (−0.14 SD per C allele, P = 2.3×10−12, and −0.16 SD per G allele, P = 1.2×10−15, respectively). Four genome-wide significant SNPs arising from BMD meta-analysis were tested for association with forearm fracture. SNP rs7776725 in FAM3C, a gene adjacent to WNT16, was associated with a genome-wide significant increased risk of forearm fracture (OR = 1.33, P = 7.3×10−9), with genome-wide suggestive signals from the two missense variants in WNT16 (rs2908004: OR = 1.22, P = 4.9×10−6 and rs2707466: OR = 1.22, P = 7.2×10−6). We next generated a homozygous mouse with targeted disruption of Wnt16. Female Wnt16−/− mice had 27% (P<0.001) thinner cortical bones at the femur midshaft, and bone strength measures were reduced between 43%–61% (6.5×10−13bone strength, and risk of fracture. PMID:22792071

  7. WNT16 influences bone mineral density, cortical bone thickness, bone strength, and osteoporotic fracture risk.

    PubMed

    Zheng, Hou-Feng; Tobias, Jon H; Duncan, Emma; Evans, David M; Eriksson, Joel; Paternoster, Lavinia; Yerges-Armstrong, Laura M; Lehtimäki, Terho; Bergström, Ulrica; Kähönen, Mika; Leo, Paul J; Raitakari, Olli; Laaksonen, Marika; Nicholson, Geoffrey C; Viikari, Jorma; Ladouceur, Martin; Lyytikäinen, Leo-Pekka; Medina-Gomez, Carolina; Rivadeneira, Fernando; Prince, Richard L; Sievanen, Harri; Leslie, William D; Mellström, Dan; Eisman, John A; Movérare-Skrtic, Sofia; Goltzman, David; Hanley, David A; Jones, Graeme; St Pourcain, Beate; Xiao, Yongjun; Timpson, Nicholas J; Smith, George Davey; Reid, Ian R; Ring, Susan M; Sambrook, Philip N; Karlsson, Magnus; Dennison, Elaine M; Kemp, John P; Danoy, Patrick; Sayers, Adrian; Wilson, Scott G; Nethander, Maria; McCloskey, Eugene; Vandenput, Liesbeth; Eastell, Richard; Liu, Jeff; Spector, Tim; Mitchell, Braxton D; Streeten, Elizabeth A; Brommage, Robert; Pettersson-Kymmer, Ulrika; Brown, Matthew A; Ohlsson, Claes; Richards, J Brent; Lorentzon, Mattias

    2012-07-01

    We aimed to identify genetic variants associated with cortical bone thickness (CBT) and bone mineral density (BMD) by performing two separate genome-wide association study (GWAS) meta-analyses for CBT in 3 cohorts comprising 5,878 European subjects and for BMD in 5 cohorts comprising 5,672 individuals. We then assessed selected single-nucleotide polymorphisms (SNPs) for osteoporotic fracture in 2,023 cases and 3,740 controls. Association with CBT and forearm BMD was tested for ∼2.5 million SNPs in each cohort separately, and results were meta-analyzed using fixed effect meta-analysis. We identified a missense SNP (Thr>Ile; rs2707466) located in the WNT16 gene (7q31), associated with CBT (effect size of -0.11 standard deviations [SD] per C allele, P = 6.2 × 10(-9)). This SNP, as well as another nonsynonymous SNP rs2908004 (Gly>Arg), also had genome-wide significant association with forearm BMD (-0.14 SD per C allele, P = 2.3 × 10(-12), and -0.16 SD per G allele, P = 1.2 × 10(-15), respectively). Four genome-wide significant SNPs arising from BMD meta-analysis were tested for association with forearm fracture. SNP rs7776725 in FAM3C, a gene adjacent to WNT16, was associated with a genome-wide significant increased risk of forearm fracture (OR = 1.33, P = 7.3 × 10(-9)), with genome-wide suggestive signals from the two missense variants in WNT16 (rs2908004: OR = 1.22, P = 4.9 × 10(-6) and rs2707466: OR = 1.22, P = 7.2 × 10(-6)). We next generated a homozygous mouse with targeted disruption of Wnt16. Female Wnt16(-/-) mice had 27% (P<0.001) thinner cortical bones at the femur midshaft, and bone strength measures were reduced between 43%-61% (6.5 × 10(-13)bone strength, and risk of fracture.

  8. Finite element analysis of dental implant loading on atrophic and non-atrophic cancellous and cortical mandibular bone - a feasibility study.

    PubMed

    Marcián, Petr; Borák, Libor; Valášek, Jiří; Kaiser, Jozef; Florian, Zdeněk; Wolff, Jan

    2014-12-18

    The first aim of this study was to assess displacements and micro-strain induced on different grades of atrophic cortical and trabecular mandibular bone by axially loaded dental implants using finite element analysis (FEA). The second aim was to assess the micro-strain induced by different implant geometries and the levels of bone-to-implant contact (BIC) on the surrounding bone. Six mandibular bone segments demonstrating different grades of mandibular bone atrophy and various bone volume fractions (from 0.149 to 0.471) were imaged using a micro-CT device. The acquired bone STL models and implant (Brånemark, Straumann, Ankylos) were merged into a three-dimensional finite elements structure. The mean displacement value for all implants was 3.1 ±1.2 µm. Displacements were lower in the group with a strong BIC. The results indicated that the maximum strain values of cortical and cancellous bone increased with lower bone density. Strain distribution is the first and foremost dependent on the shape of bone and architecture of cancellous bone. The geometry of the implant, thread patterns, grade of bone atrophy and BIC all affect the displacement and micro-strain on the mandible bone. Preoperative finite element analysis could offer improved predictability in the long-term outlook of dental implant restorations.

  9. Micro-Computed Tomography of Fatigue Microdamage in Cortical Bone Using a Barium Sulfate Contrast Agent

    PubMed Central

    Leng, Huijie; Wang, Xiang; Ross, Ryan D.; Niebur, Glen L.; Roeder, Ryan K.

    2008-01-01

    Accumulation of microdamage during fatigue can lead to increased fracture susceptibility in bone. Current techniques for imaging microdamage in bone are inherently destructive and two-dimensional. Therefore, the objective of this study was to image the accumulation of fatigue microdamage in cortical bone using micro-computed tomography (micro-CT) with a barium sulfate (BaSO4) contrast agent. Two symmetric notches were machined on the tensile surface of bovine cortical bone beams in order to generate damage ahead of the stress concentrations during four-point bending fatigue. Specimens were loaded to a specified number of cycles or until one notch fractured, such that the other notch exhibited the accumulation of microdamage prior to fracture. Microdamage ahead of the notch was stained in vitro by precipitation of BaSO4 and imaged using micro-CT. Reconstructed images showed a distinct region of bright voxels around the notch tip or along propagating cracks due to the presence of BaSO4, which was verified by backscattered electron imaging and energy dispersive spectroscopy. The shape of the stained region ahead of the notch tip was consistent with principal strain contours calculated by finite element analysis. The relative volume of the stained region was correlated with the number of loading cycles by non-linear regression using a power-law. This study demonstrates new methods for the non-destructive and three-dimensional detection of fatigue microdamage accumulation in cortical bone in vitro, which may be useful to gain further understanding into the role of microdamage in bone fragility. PMID:18443659

  10. [Fracture toughness of cortical bone in tension, shear, and tear--a comparison of longitudinal and transverse fracture].

    PubMed

    Feng, Z

    1997-09-01

    The fracture toughness at crack initiation was determined for bovine cortical bone under tension (mode I), shear (mode II), and tear (mode III). A total of 130 compact tension specimens, compact shear specimens and triple pantleg specimens were used for the measurement of fracture toughness under tension, shear, and tear, respectively. Multiple-sample compliance method was utilized to measure the critical strain energy release rate (Gc) at the a/W = 0.55 (crack length, a, to specimen width, W, ratio). The critical stress intensity factor (Kc) was also calculated from the critical loading (PQ) of the specimens at the a/W = 0.55. The effect of the anisotropy of bone on its resistance to crack initiation under shear and tear loading was investigated as well. The fracture toughness of bone with precrack orientations parallel(designed as longitudinal fracture) to and that with precrack orientations normal (designed as transverse fracture) to the longitudinal axis of bone were compared. In longitudinal fracture, the critical strain energy release rates(Gc) of cortical bone under tension, shear, and tear were 644 +/- 102, 2430 +/- 836, and 1723 +/- 486 N/m, respectively. In transverse fracture, the critical strain energy release rates(Gc) of cortical bone under tesion, shear, and tear were 1374 +/- 183, 4710 +/- 1284, and 4016 +/- 948 N/m, respectively. An analysis of variance demonstrated that the crack initiation fracture toughness of bone under shear and tear loading is significantly greater than that under tensile loading in both longitudinal and transverse fracture. Our results also suggest that cortical bone has been "designed" to prevent crack initiation in transverse fracture under tension, shear, and tesar.

  11. Effect of a hypergravity environment on cortical bone elasticity in rats

    NASA Technical Reports Server (NTRS)

    Kohles, S. S.; Bowers, J. R.; Vailas, A. C.; Vanderby, R. Jr

    1996-01-01

    There is considerable interest in determining whether hypergravity can be used as a countermeasure for microgravity-induced bone loss. This study was conducted on 20 immature male rats in order to investigate possible elastic adaptations of cortical bone in rapidly growing rats exposed to chronic hypergravity. Ten rats were continuously centrifuged for 14 days at twice gravitational acceleration (2G) on a 12.75 foot radius centrifuge and 10 rats concurrently acted as stationary controls. The effect of hypergravity on the elastic characteristics of cortical bone was quantified via ultrasonic wave propagation. Propagation velocities of longitudinal and shear waves were measured through cubic cortical specimens from the posterior femoral diaphyses. Density was measured with an Archimedes' technique. The orthotropic elastic properties were calculated and used to compare the difference between groups. Results showed an average increase in both the Young's moduli (Eii, + 2.2%) and shear moduli (Gij, + 4.3%) with a statistically significant increase only in G12 (+15.7%, P = 0.046). The ratio of transverse to axial strain (Poisson's ratio, nuij) demonstrated statistically significant changes in nu12, nu21, nu13, and nu31 (P < 0.05). These findings suggest that although slight elastic changes were incurred via a hypergravity environment, the treatment level or duration in this study do not dramatically perturb the normal elastic behavior of cortical bone and that dramatic biomechanical differences noted in previous studies were due more to structural changes than material elasticity changes. Hypergravity applied post facto to a microgravity environment would offer further illucidation of this method as treatment for a degenerative spaceflight experience.

  12. Effect of a hypergravity environment on cortical bone elasticity in rats

    NASA Technical Reports Server (NTRS)

    Kohles, S. S.; Bowers, J. R.; Vailas, A. C.; Vanderby, R. Jr

    1996-01-01

    There is considerable interest in determining whether hypergravity can be used as a countermeasure for microgravity-induced bone loss. This study was conducted on 20 immature male rats in order to investigate possible elastic adaptations of cortical bone in rapidly growing rats exposed to chronic hypergravity. Ten rats were continuously centrifuged for 14 days at twice gravitational acceleration (2G) on a 12.75 foot radius centrifuge and 10 rats concurrently acted as stationary controls. The effect of hypergravity on the elastic characteristics of cortical bone was quantified via ultrasonic wave propagation. Propagation velocities of longitudinal and shear waves were measured through cubic cortical specimens from the posterior femoral diaphyses. Density was measured with an Archimedes' technique. The orthotropic elastic properties were calculated and used to compare the difference between groups. Results showed an average increase in both the Young's moduli (Eii, + 2.2%) and shear moduli (Gij, + 4.3%) with a statistically significant increase only in G12 (+15.7%, P = 0.046). The ratio of transverse to axial strain (Poisson's ratio, nuij) demonstrated statistically significant changes in nu12, nu21, nu13, and nu31 (P < 0.05). These findings suggest that although slight elastic changes were incurred via a hypergravity environment, the treatment level or duration in this study do not dramatically perturb the normal elastic behavior of cortical bone and that dramatic biomechanical differences noted in previous studies were due more to structural changes than material elasticity changes. Hypergravity applied post facto to a microgravity environment would offer further illucidation of this method as treatment for a degenerative spaceflight experience.

  13. Insulin Resistance and the IGF-I-Cortical Bone Relationship in Children Ages 9 to 13 Years.

    PubMed

    Kindler, Joseph M; Pollock, Norman K; Laing, Emma M; Oshri, Assaf; Jenkins, Nathan T; Isales, Carlos M; Hamrick, Mark W; Ding, Ke-Hong; Hausman, Dorothy B; McCabe, George P; Martin, Berdine R; Hill Gallant, Kathleen M; Warden, Stuart J; Weaver, Connie M; Peacock, Munro; Lewis, Richard D

    2017-07-01

    IGF-I is a pivotal hormone in pediatric musculoskeletal development. Although recent data suggest that the role of IGF-I in total body lean mass and total body bone mass accrual may be compromised in children with insulin resistance, cortical bone geometric outcomes have not been studied in this context. Therefore, we explored the influence of insulin resistance on the relationship between IGF-I and cortical bone in children. A secondary aim was to examine the influence of insulin resistance on the lean mass-dependent relationship between IGF-I and cortical bone. Children were otherwise healthy, early adolescent black and white boys and girls (ages 9 to 13 years) and were classified as having high (n = 147) or normal (n = 168) insulin resistance based on the homeostasis model assessment of insulin resistance (HOMA-IR). Cortical bone at the tibia diaphysis (66% site) and total body fat-free soft tissue mass (FFST) were measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA), respectively. IGF-I, insulin, and glucose were measured in fasting sera and HOMA-IR was calculated. Children with high HOMA-IR had greater unadjusted IGF-I (p < 0.001). HOMA-IR was a negative predictor of cortical bone mineral content, cortical bone area (Ct.Ar), and polar strength strain index (pSSI; all p ≤ 0.01) after adjusting for race, sex, age, maturation, fat mass, and FFST. IGF-I was a positive predictor of most musculoskeletal endpoints (all p < 0.05) after adjusting for race, sex, age, and maturation. However, these relationships were moderated by HOMA-IR (pInteraction  < 0.05). FFST positively correlated with most cortical bone outcomes (all p < 0.05). Path analyses demonstrated a positive relationship between IGF-I and Ct.Ar via FFST in the total cohort (βIndirect Effect  = 0.321, p < 0.001). However, this relationship was moderated in the children with high (βIndirect Effect  = 0.200, p

  14. Experimental analysis of drilling process in cortical bone.

    PubMed

    Wang, Wendong; Shi, Yikai; Yang, Ning; Yuan, Xiaoqing

    2014-02-01

    Bone drilling is an essential part in orthopaedics, traumatology and bone biopsy. Prediction and control of drilling forces and torque are critical to the success of operations involving bone drilling. This paper studied the drilling force, torque and drilling process with automatic and manual drill penetrating into bovine cortical bone. The tests were performed on a drilling system which is used to drill and measure forces and torque during drilling. The effects of drilling speed, feed rate and drill bit diameter on force and torque were discussed separately. The experimental results were proven to be in accordance with the mathematic expressions introduced in this paper. The automatic drilling saved drilling time by 30-60% in the tested range and created less vibration, compared to manual drilling. The deviation between maximum and average force of the automatic drilling was 5N but 25N for manual drilling. To conclude, using the automatic method has significant advantages in control drilling force, torque and drilling process in bone drilling.

  15. Transduction of mechanical strain in bone

    NASA Technical Reports Server (NTRS)

    Duncan, R. L.

    1995-01-01

    One physiologic consequence of extended periods of weightlessness is the rapid loss of bone mass associated with skeletal unloading. Conversely, mechanical loading has been shown to increase bone formation and stimulate osteoblastic function. The mechanisms underlying mechanotransduction, or how the osteoblast senses and converts biophysical stimuli into cellular responses has yet to be determined. For non-innervated mechanosensitive cells like the osteoblast, mechanotransduction can be divided into four distinct phases: 1) mechanocoupling, or the characteristics of the mechanical force applied to the osteoblast, 2) biochemical coupling, or the mechanism through which mechanical strain is transduced into a cellular biochemical signal, 3) transmission of signal from sensor to effector cell and 4) the effector cell response. This review examines the characteristics of the mechanical strain encountered by osteoblasts, possible biochemical coupling mechanisms, and how the osteoblast responds to mechanical strain. Differences in osteoblastic responses to mechanical strain are discussed in relation to the types of strain encountered and the possible transduction pathways involved.

  16. Transduction of mechanical strain in bone

    NASA Technical Reports Server (NTRS)

    Duncan, R. L.

    1995-01-01

    One physiologic consequence of extended periods of weightlessness is the rapid loss of bone mass associated with skeletal unloading. Conversely, mechanical loading has been shown to increase bone formation and stimulate osteoblastic function. The mechanisms underlying mechanotransduction, or how the osteoblast senses and converts biophysical stimuli into cellular responses has yet to be determined. For non-innervated mechanosensitive cells like the osteoblast, mechanotransduction can be divided into four distinct phases: 1) mechanocoupling, or the characteristics of the mechanical force applied to the osteoblast, 2) biochemical coupling, or the mechanism through which mechanical strain is transduced into a cellular biochemical signal, 3) transmission of signal from sensor to effector cell and 4) the effector cell response. This review examines the characteristics of the mechanical strain encountered by osteoblasts, possible biochemical coupling mechanisms, and how the osteoblast responds to mechanical strain. Differences in osteoblastic responses to mechanical strain are discussed in relation to the types of strain encountered and the possible transduction pathways involved.

  17. Multiscale and multimodality computed tomography for cortical bone analysis

    NASA Astrophysics Data System (ADS)

    Ostertag, A.; Peyrin, F.; Gouttenoire, P. J.; Laredo, J. D.; DeVernejoul, M. C.; Cohen Solal, M.; Chappard, C.

    2016-12-01

    In clinical studies, high resolution peripheral quantitative computed tomography (HR-pQCT) is used to separately evaluate cortical bone and trabecular bone with an isotropic voxel of 82 µm3, and typical cortical parameters are cortical density (D.comp), thickness (Ct.Th), and porosity (Ct.Po). In vitro, micro-computed tomography (micro-CT) is used to explore the internal cortical bone micro-structure with isotropic voxels and high resolution synchrotron radiation (SR); micro-CT is considered the ‘gold standard’. In 16 tibias and 8 femurs, HR-pQCT measurements were compared to conventional micro-CT measurements. To test modality effects, conventional micro-CT measurements were compared to SR micro-CT measurements at 7.5 µm3 SR micro-CT measurements were also tested at different voxel sizes for the femurs, specifically, 7.5 µm3 versus 2.8 µm3. D.comp (r  =  -0.88, p  <  10-3) was the parameter best correlated with porosity (Po.V/TV). The correlation was not affected by the removal of pores under 130 µm. Ct.Th was also significantly highly correlated (r  =  -0.89 p  <  10-3), while Ct.Po was correlated with its counterpart Po.V/TV (r  =  0.74, p  <  10-3). From SR micro-CT and conventional micro-CT at 7.5 µm3 in matching areas, Po.V/TV and pore diameter were underestimated in conventional micro-CT with mean  ±  standard deviation (SD) biases of  -2.5  ±  1.9% and  -0.08  ±  0.08 mm, respectively. In contrast, pore number (Po.N) and pore separation (Po.Sp) were overestimated with mean  ±  SD biases of  +0.03  ±  0.04 mm-1 and  +0.02  ±  0.04 mm, respectively. The results from the tibia and femur were similar when the results of SR micro-CT at 7.5 µm3 and 2.8 µm3 were compared. Po.V/TV, specific surface of pores (Po.S/Po.V), and Po.N were underestimated with mean biases of  -1.7  ±  0.9%, -4.6  ±  4.4 mm-1, and

  18. Dynamic testing of old and young baboon cortical bone with numerical validation

    NASA Astrophysics Data System (ADS)

    Chocron, S.; Nicolella, D.; Nicholls, A. E.; Bredbenner, T.; Havill, L.

    2012-08-01

    Cortical bone tensile mechanical properties at quasistatic and high rates (˜300s-1) were determined ex vivo using the right femurs of 12 female baboons, (Papio hamadryas spp.) from the Texas Biomedical Research Institute/Southwest National Primate Research Center in San Antonio, Texas. The animals were divided into two age groups: a young age group (6.63 ± 0.6 years) and an old age group (26.96 ± 1.3 years). Seven specimens per group were monotonically loaded to failure to determine their mechanical properties. The quasistatic strength of the bone for the old group was just a little (but not significantly) lower than the young group. High strain rate tests performed with the Hopkinson bar indicate that baboon bone from the older group was significantly weaker under impact loads than that from the younger group. This observation is particularly important due to the similarities between baboon and human bone tissue. Typical strain rates for these tests ranged from 130s-1 to 250s-1. A full-size 3-D simulation of the Hopkinson bar test was performed to confirm that the bone specimen was under stress equilibrium and to evaluate the consistency of the modulus and strength inferred from the tests. Simulations were performed in which the modulus, strength and failure strain were varied to see the sensitivity of the results. Additionally, simplified simulations were performed to estimate the strain rate environment of a femur during a fall at an impact velocity of 5 m/s, similar to a free fall velocity from a height of 1.3 meters. The simulations confirm that strain rates obtained in the Hopkinson bar are relevant because they are similar to those expected inr such a fall.

  19. Two-wave behavior under various conditions of transition area from cancellous bone to cortical bone.

    PubMed

    Nagatani, Yoshiki; Mizuno, Katsunori; Matsukawa, Mami

    2014-07-01

    The two-wave phenomenon, the wave separation of a single ultrasonic pulse in cancellous bone, is expected to be a useful tool for the diagnosis of osteoporosis. However, because actual bone has a complicated structure, precise studies on the effect of transition conditions between cortical and cancellous parts are required. This study investigated how the transition condition influenced the two-wave generation using three-dimensional X-ray CT images of an equine radius and a three-dimensional simulation technique. As a result, any changes in the boundary between cortical part and trabecular part, which gives the actual complex structure of bone, did not eliminate the generation of either the primary wave or the secondary wave at least in the condition of clear trabecular alignment. The results led us to the possibility of using the two-wave phenomenon in a diagnostic system for osteoporosis in cases of a complex boundary.

  20. [Normal tissue tolerance to external beam radiation therapy: Bone marrow and cortical bone structures].

    PubMed

    Schernberg, A; Hennequin, C

    2017-10-01

    In patients undergoing external radiation therapy, bone marrow and cortical bone structures are all often neglected as organs at risk. Still, from increased febrile neutropenia risk in patients undergoing chemoradiation for a pelvic tumour to increased risk of vertebral fracture when undergoing hypofractioned stereotactic radiotherapy of a spinal metastasis, adverse effects are frequent and sometimes serious. This literature review first defines the rules for contouring these structures, then the dose constraints currently recommended. This article focuses first on conventional irradiation or intensity modulation radiotherapy considering classical fractionation. Secondly, it focuses on stereotactic radiotherapy. The considered organs will be haematopoietic structures, and bone cortical structures. Current recommendations are summarised in a table. Copyright © 2017 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

  1. Osteoprogenitor cells from bone marrow and cortical bone: understanding how the environment affects their fate.

    PubMed

    Corradetti, Bruna; Taraballi, Francesca; Powell, Sebastian; Sung, David; Minardi, Silvia; Ferrari, Mauro; Weiner, Bradley K; Tasciotti, Ennio

    2015-05-01

    Bone is a dynamic organ where skeletal progenitors and hematopoietic cells share and compete for space. Presumptive mesenchymal stem cells (MSC) have been identified and harvested from the bone marrow (BM-MSC) and cortical bone fragments (CBF-MSC). In this study, we demonstrate that despite the cells sharing a common ancestor, the differences in the structural properties of the resident tissues affect cell behavior and prime them to react differently to stimuli. Similarly to the bone marrow, the cortical portion of the bone contains a unique subset of cells that stains positively for the common MSC-associated markers. These cells display different multipotent differentiation capability, clonogenic expansion, and immunosuppressive potential. In particular, when compared with BM-MSC, CBF-MSC are bigger in size, show a lower proliferation rate at early passages, have a greater commitment toward the osteogenic lineage, constitutively produce nitric oxide as a mediator for bone remodeling, and more readily respond to proinflammatory cytokines. Our data suggest that the effect of the tissue's microenvironment makes the CBF-MSC a superior candidate in the development of new strategies for bone repair.

  2. An investigation of the mineral in ductile and brittle cortical mouse bone.

    PubMed

    Rodriguez-Florez, Naiara; Garcia-Tunon, Esther; Mukadam, Quresh; Saiz, Eduardo; Oldknow, Karla J; Farquharson, Colin; Millán, José Luis; Boyde, Alan; Shefelbine, Sandra J

    2015-05-01

    Bone is a strong and tough material composed of apatite mineral, organic matter, and water. Changes in composition and organization of these building blocks affect bone's mechanical integrity. Skeletal disorders often affect bone's mineral phase, either by variations in the collagen or directly altering mineralization. The aim of the current study was to explore the differences in the mineral of brittle and ductile cortical bone at the mineral (nm) and tissue (µm) levels using two mouse phenotypes. Osteogenesis imperfecta model, oim(-/-) , mice have a defect in the collagen, which leads to brittle bone; PHOSPHO1 mutants, Phospho1(-/-) , have ductile bone resulting from altered mineralization. Oim(-/-) and Phospho1(-/-) were compared with their respective wild-type controls. Femora were defatted and ground to powder to measure average mineral crystal size using X-ray diffraction (XRD) and to monitor the bulk mineral to matrix ratio via thermogravimetric analysis (TGA). XRD scans were run after TGA for phase identification to assess the fractions of hydroxyapatite and β-tricalcium phosphate. Tibiae were embedded to measure elastic properties with nanoindentation and the extent of mineralization with backscattered electron microscopy (BSE SEM). Results revealed that although both pathology models had extremely different whole-bone mechanics, they both had smaller apatite crystals, lower bulk mineral to matrix ratio, and showed more thermal conversion to β-tricalcium phosphate than their wild types, indicating deviations from stoichiometric hydroxyapatite in the original mineral. In contrast, the degree of mineralization of bone matrix was different for each strain: brittle oim(-/-) were hypermineralized, whereas ductile Phospho1(-/-) were hypomineralized. Despite differences in the mineralization, nanoscale alterations in the mineral were associated with reduced tissue elastic moduli in both pathologies. Results indicated that alterations from normal crystal size

  3. Evidence of strain-mode-related cortical adaptation in the diaphysis of the horse radius.

    PubMed

    Mason, M W; Skedros, J G; Bloebaum, R D

    1995-09-01

    The relative importance that certain strain features, including mode (e.g., tension vs. compression) and magnitude, have in affecting adaptive bone remodeling seen in normal skeletally mature bones remains controversial. The equine radius is used as a model because in vivo strain data show that the mid-to-proximal diaphysis receives a consistent history of predominantly cranial-caudal bending loads, in contrast to the distal diaphysis which receives relatively more torsional loading superimposed on cranial-caudal bending. Medial and lateral cortices serve as control regions because they correspond to a neutral axis of bending. Equine radii were sectioned transversely at 65% (proximal), 50%, and 35% (distal) of length and cortical bone from the cranial ("tension"), caudal ("compression"), medial, and lateral regions was examined to determine if one, of many, structural and material features could be distinguished as being consistently related to the distribution of the prevailing strain modes. Mineral content (percent ash) differences, though statistically significant (p < 0.01), vary less than 1% between regions of the cortex at all sections. Porosity is not significantly different between any of the regions (p = 0.13). In the 65% and 50% sections, secondary osteon population density (OPD, osteons per square millimeter) and fractional area of secondary bone (FASB) are each nearly two times as great in the caudal regions than in the other three regions (p < 0.01). The 35% section shows a pattern opposite of that in the other sections--there are more than two times as many osteons in the cranial cortex than in the caudal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

  4. Effect of specimen geometry on tensile strength of cortical bone.

    PubMed

    Feng, Liang; Jasiuk, Iwona

    2010-11-01

    We investigate the effect of specimen geometry on the ultimate tensile strength of cortical bone measured by a tensile test. This article is motivated by the fact that there is no clear consensus in the literature on a suitable specimen shape for cortical bone testing. We consider three commonly used tensile test specimen shapes: strip, dumbbell with sharp junctions, and dumbbell with rounded junctions. We conduct this study computationally, using a finite element method, and experimentally by testing porcine femurs. Our results show that local stress concentration factors in the specimen lead to reduced values in the measured tensile strength. The higher the stress concentrations are, the lower is the measured strength. We find that the strip specimens are not a good choice due to high stress concentrations. For the same reason, dumbbell specimens with sharp junctions between the grip and gage sections should also be avoided. The dumbbell shaped tensile test specimens with an arc transition and a maximized radius of fillet are a better choice because such geometry lowers stress concentrations.

  5. Midline Lumbar Fusion with Cortical Bone Trajectory Screw

    PubMed Central

    MIZUNO, Masaki; KURAISHI, Keita; UMEDA, Yasuyuki; SANO, Takanori; TSUJI, Masanori; SUZUKI, Hidenori

    2014-01-01

    A novel cortical bone trajectory (CBT) screw technique provides an alternative fixation technique for lumbar spine. Trajectory of CBT screw creates a caudo-cephalad path in sagittal plane and a medio-lateral path in axial plane, and engages cortical bone in the pedicle. The theoretical advantage is that it provides enhanced screw grip and interface strength. Midline lumbar fusion (MIDLF) is composed of posterior mid-line approach, microsurgical laminectomy, and CBT screw fixation. We adopted the MIDLF technique for lumbar spondylolisthesis. Advantages of this technique include that decompression and fusion are available in the same field, and it minimizes approach-related damages. To determine whether MIDLF with CBT screw is as effective as traditional approach and it is minimum invasive technique, we studied the clinical and radiological outcomes of MIDLF. Our results indicate that MIDLF is effective and minimum invasive technique. Evidence of effectiveness of MIDLF is that patients had good recovery score, and that CBT screw technique was safety in clinical and stable in radiological. MIDLF with CBT screw provides the surgeon with additional options for fixation. This technique is most likely to be useful for treating lumbar spondylolisthesis in combination with midline decompression and insertion of an interbody graft, such as the transforaminal lumbar interbody fusion or posterior lumbar interbody fusion techniques. PMID:25169139

  6. In Vitro Fracture of Human Cortical Bone: Local Fracture Criteria and Toughening Mechanisms

    SciTech Connect

    Nalla, R; Stolken, J; Kinney, J; Ritchie, R

    2004-08-18

    A micro-mechanistic understanding of bone fracture that encompasses how cracks interact with the underlying microstructure and defines their local failure mode is lacking, despite extensive research on the response of bone to a variety of factors like aging, loading, and/or disease. Micro-mechanical models for fracture incorporating such local failure criteria have been widely developed for metallic and ceramic materials systems; however, few such deliberations have been undertaken for the fracture of bone. In fact, although the fracture event in mineralized tissues such as bone is commonly believed to be locally strain controlled, until recently there has been little experimental evidence to support this widely held belief. In the present study, a series of in vitro experiments involving a double-notch bend test geometry are performed in order to shed further light on the nature of the local cracking events that precede catastrophic fracture in bone and to define their relationship to the microstructure. Specifically, crack-microstructure interactions are examined to determine the salient toughening mechanisms in human cortical bone and to characterize how these may affect the anisotropy in fracture properties. Based on preliminary micro-mechanical models of these processes, in particular crack deflection and uncracked ligament bridging, the relative importance of these toughening mechanisms is established.

  7. Cortical bone development under the growth plate is regulated by mechanical load transfer.

    PubMed

    Tanck, E; Hannink, G; Ruimerman, R; Buma, P; Burger, E H; Huiskes, R

    2006-01-01

    Longitudinal growth of long bones takes place at the growth plates. The growth plate produces new bone trabeculae, which are later resorbed or merged into the cortical shell. This process implies transition of trabecular metaphyseal sections into diaphyseal sections. We hypothesize that the development of cortical bone is governed by mechanical stimuli. We also hypothesize that trabecular and cortical bone share the same regulatory mechanisms for adaptation to mechanical loads. To test these hypotheses, we monitored the development of the tibial cortex in growing pigs, using micro-computer tomography and histology. We then tested the concept that regulatory mechanisms for trabecular bone adaptation can also explain cortical bone development using our mechanical stimulation theory, which could explain trabecular bone (re)modelling. The main results showed that, from the growth plate towards the diaphysis, the pores of the trabecular structure were gradually filled in with bone, which resulted in increased density and cortical bone. The computer model largely predicted this morphological development. We conclude that merging of metaphyseal trabeculae into cortex is likely to be governed by mechanical stimuli. Furthermore, cortex development of growing long bones can be explained as a form of trabecular bone adaptation, without the need for different regulatory mechanisms for cortical and trabecular bone.

  8. Noncontact ultrasound imaging applied to cortical bone phantoms

    PubMed Central

    Bulman, J. B.; Ganezer, K. S.; Halcrow, P. W.; Neeson, Ian

    2012-01-01

    Purpose: The purpose of this paper was to take the first steps toward applying noncontact ultrasound (NCU) to the tasks of monitoring osteoporosis and quantitative ultrasound imaging (QUS) of cortical bone. The authors also focused on the advantages of NCU, such as its lack of reliance on a technologist to apply transducers and a layer of acoustical coupling gel, the ability of the transducers to operate autonomously as specified by preprogrammed software, and the likely reduction in statistical and systematic errors associated with the variability in the pressure applied by the clinician to the transmitting transducer that NCU might provide. The authors also undertook this study in order to find additional applications of NCU beyond its past limited usage in assessing the severity of third degree burns. Methods: A noncontact ultrasound imaging system using a pair of specially designed broadband, 1.5 MHz noncontact piezoelectric transducers and cortical bone phantoms, were used to determine bone mineral density (BMD), speed of sound (SOS), integrated response (IR), and ultrasonic transmittance. Air gaps of greater than 3 cm, two transmission and two reflection paths, and a digital signal processor were also used in the collection of data from phantoms of nominal mass densities that varied from 1.17 to 2.25 g/cm3 and in bone mineral density from 0 to 1.7 g/cm3. Results: Good correlations between known BMD and measured SOS, IR, and transmittance were obtained for all 17 phantoms, and methods for quantifying and minimizing sources of systematic errors were outlined. The BMD of the phantom sets extended through most of the in vivo range found in cortical bone. A total of 16–20 repeated measurements of the SOS, thickness, and IR for the phantom set that were conducted over a period of several months showed a small variation in the range of measurements of ±1%–2%. These NCU data were shown to be in agreement with similar results using contact ultrasound to be within

  9. Nanoindentation analysis of the micromechanical anisotropy in mouse cortical bone.

    PubMed

    Casanova, Michele; Balmelli, Anna; Carnelli, Davide; Courty, Diana; Schneider, Philipp; Müller, Ralph

    2017-02-01

    Studies investigating micromechanical properties in mouse cortical bone often solely focus on the mechanical behaviour along the long axis of the bone. Therefore, data on the anisotropy of mouse cortical bone is scarce. The aim of this study is the first-time evaluation of the anisotropy ratio between the longitudinal and transverse directions of reduced modulus and hardness in mouse femurs by using the nanoindentation technique. For this purpose, nine 22-week-old mice (C57BL/6) were sacrificed and all femurs extracted. A total of 648 indentations were performed with a Berkovich tip in the proximal (P), central (C) and distal (D) regions of the femoral shaft in the longitudinal and transverse directions. Higher values for reduced modulus are obtained for indentations in the longitudinal direction, with anisotropy ratios of 1.72 ± 0.40 (P), 1.75 ± 0.69 (C) and 1.34 ± 0.30 (D). Hardness is also higher in the longitudinal direction, with anisotropic ratios of 1.35 ± 0.27 (P), 1.35 ± 0.47 (C) and 1.17 ± 0.19 (D). We observed a significant anisotropy in the micromechanical properties of the mouse femur, but the correlation for reduced modulus and hardness between the two directions is low (r(2) < 0.3) and not significant. Therefore, we highly recommend performing independent indentation testing in both the longitudinal and transverse directions when knowledge of the tissue mechanical behaviour along multiple directions is required.

  10. Nanoindentation analysis of the micromechanical anisotropy in mouse cortical bone

    PubMed Central

    Balmelli, Anna; Carnelli, Davide; Courty, Diana; Müller, Ralph

    2017-01-01

    Studies investigating micromechanical properties in mouse cortical bone often solely focus on the mechanical behaviour along the long axis of the bone. Therefore, data on the anisotropy of mouse cortical bone is scarce. The aim of this study is the first-time evaluation of the anisotropy ratio between the longitudinal and transverse directions of reduced modulus and hardness in mouse femurs by using the nanoindentation technique. For this purpose, nine 22-week-old mice (C57BL/6) were sacrificed and all femurs extracted. A total of 648 indentations were performed with a Berkovich tip in the proximal (P), central (C) and distal (D) regions of the femoral shaft in the longitudinal and transverse directions. Higher values for reduced modulus are obtained for indentations in the longitudinal direction, with anisotropy ratios of 1.72 ± 0.40 (P), 1.75 ± 0.69 (C) and 1.34 ± 0.30 (D). Hardness is also higher in the longitudinal direction, with anisotropic ratios of 1.35 ± 0.27 (P), 1.35 ± 0.47 (C) and 1.17 ± 0.19 (D). We observed a significant anisotropy in the micromechanical properties of the mouse femur, but the correlation for reduced modulus and hardness between the two directions is low (r2 < 0.3) and not significant. Therefore, we highly recommend performing independent indentation testing in both the longitudinal and transverse directions when knowledge of the tissue mechanical behaviour along multiple directions is required. PMID:28386450

  11. Biomechanical effectiveness of cortical bone thickness on orthodontic microimplant stability: an evaluation based on the load share between cortical and cancellous bone.

    PubMed

    Alrbata, Raed H; Yu, Wonjae; Kyung, Hee-Moon

    2014-08-01

    The aim of this study was to determine the appropriate range of cortical bone thickness (CBT) for supporting an orthodontic microimplant. Analysis of an orthodontic microimplant subjected to a horizontal force of 2N was performed using a nonlinear finite element method. The peak stresses in the cortical bone of 6 bone specimens (6 base models) with CBT of 0.5, 0.75, 1.0, 1.5, 2.0, and 3.0 mm, respectively, were analyzed. Assuming that the biomechanical effectiveness of cortical and cancellous bone is determined by the portion of the orthodontic force that each bone component takes up, we defined the ratios of the orthodontic force divided between the cortical and cancellous bone as load share ratios (LSR): ie, LSRcortical and LSRcancellous. Along with the base models, imaginary models created by removal of the cancellous bone from the base model bone specimens were analyzed in parallel; the imaginary models were designed so that the cortical bone alone took up all of the orthodontic force. By comparing the peak stresses in the imaginary and base models, the ratios of orthodontic force taken up by the cancellous and cortical bone (LSRcancellous and LSRcortical) were calculated. The highest stress concentration occurred near the fulcrum where the orthodontic microimplant, undergoing tipping, presses the cortical bone surface in the direction of the force. Overall, the increase in CBT resulted in a decrease of the peak stress in the cortical bone. The decrease of stress, however, was not significant when the CBT was > 2.0 mm. LSR analysis showed that the cancellous bone has a substantial role in resisting the orthodontic force in cases of CBT ≤1.0 mm. Its role, however, declined rapidly with an increase of CBT and virtually disappeared at CBT values > 2.0 mm. LSRcortical was approximately 95% (LSRcancellous was 5%) at CBT = 1.5 mm and almost 100% at CBT = 2.0 mm, indicating that virtually all of the orthodontic force is transmitted to the cortical bone at CBT values

  12. Interpreting cortical bone adaptation and load history by quantifying osteon morphotypes in circularly polarized light images.

    PubMed

    Skedros, John G; Mendenhall, Shaun D; Kiser, Casey J; Winet, Howard

    2009-03-01

    Birefringence variations in circularly polarized light (CPL) images of thin plane-parallel sections of cortical bone can be used to quantify regional differences in predominant collagen fiber orientation (CFO). Using CPL images of equine third metacarpals (MC3s), R.B. Martin, V.A. Gibson, S.M. Stover, J.C. Gibeling, and L.V. Griffin. (40) described six secondary osteon variants ('morphotypes') and suggested that differences in their regional prevalence affect fatigue resistance and toughness. They devised a numerical osteon morphotype score (MTS) for quantifying regional differences in osteon morphotypes. We have observed that a modification of this score could significantly improve its use for interpreting load history. We hypothesized that our modified osteon MTS would more accurately reveal differences in osteon MTSs between opposing "tension" and "compression" cortices of diaphyses of habitually bent bones. This was tested using CPL images in transverse sections of calcanei from sheep, deer, and horses, and radii from sheep and horses. Equine MC3s and sheep tibiae were examined as controls because they experience comparatively greater load complexity that, because of increased prevalence of torsion/shear, would not require regional mechanical enhancements provided by different osteon morphotypes. Predominant CFO, which can reliably reflect adaptation for a regionally prevalent strain mode, was quantified as mean gray levels from birefringence of entire images (excluding pore spaces) in anterior, posterior, medial, and lateral cortices. Results showed that, in contrast to the original scoring scheme of Martin et al., the modified scheme revealed significant anterior/posterior differences in osteon MTSs in nearly all "tension/compression" bones (p<0.0001), but not in equine MC3s (p=0.30) and sheep tibiae (p=0.35). Among habitually bent bones, sheep radii were the exception; relatively lower osteon populations and the birefringence of the primary bone contributed

  13. Strain determination in bone sections with simultaneous 3D digital holographic interferometry

    NASA Astrophysics Data System (ADS)

    Alvarez, Araceli Sánchez; De la Torre Ibarra, Manuel H.; Santoyo, Fernando Mendoza; Anaya, Tonatiuh-Saucedo

    2014-06-01

    A 3D digital holographic interferometer was used to measure the surface strain components in two different bovine's bone sections. The applied force on the sample was induced by a precisely controlled lateral micro compression. The simultaneous acquisition capability of the system helps to record a fast sequence of images, each one containing three independent holograms that result in three orthogonal displacement components u, v and w from which the surface strain components ɛx, ɛy and γxy over the bone's field of view were calculated. This research study was carried out in two different bone sections: the cortical bone and the medullary cavity/yellow marrow section. The resulting strain concentrators are of great importance to better understand the mechanical response of complex biological structures such as this bovine femoral bone.

  14. A study of dielectric anisotropy in dehydrated cortical bone.

    PubMed

    García Sánchez, F J; De Mercato, G

    The complex permittivity of dehydrated bovine femoral bone has been studied in vitro, in the three orthogonal directions from 1 kHz to 3 MHz, as part of an analysis of the various factors involved in the dielectric behavior of fluid-saturated cortical bone. In this study the bone's physical structure reveals its anisotropic nature by its dependence on both the real and imaginary parts of permittivity on the orientation of the applied electric field. The real permittivity and the total conductivity are generally higher in the longitudinal direction than in the other two transverse directions, with the tangential direction presenting values between those of the longitudinal and radial directions and closer to the former. The high frequency limit of the real part of the permittivity was found to be around 10 and its low frequency limit is of the order of 1000. The dispersion parameters of relaxation time show values of about 0.4 and the corresponding mean relaxation frequencies are below 100 Hz.

  15. Aging and Fracture of Human Cortical Bone and Tooth Dentin

    SciTech Connect

    Ager, Joel; Koester, Kurt J.; Ager III, Joel W.; Ritchie, Robert O.

    2008-05-07

    Mineralized tissues, such as bone and tooth dentin, serve as structural materials in the human body and, as such, have evolved to resist fracture. In assessing their quantitative fracture resistance or toughness, it is important to distinguish between intrinsic toughening mechanisms which function ahead of the crack tip, such as plasticity in metals, and extrinsic mechanisms which function primarily behind the tip, such as crack bridging in ceramics. Bone and dentin derive their resistance to fracture principally from extrinsic toughening mechanisms which have their origins in the hierarchical microstructure of these mineralized tissues. Experimentally, quantification of these toughening mechanisms requires a crack-growth resistance approach, which can be achieved by measuring the crack-driving force, e.g., the stress intensity, as a function of crack extension ("R-curve approach"). Here this methodology is used to study of the effect of aging on the fracture properties of human cortical bone and human dentin in order to discern the microstructural origins of toughness in these materials.

  16. Aging and fracture of human cortical bone and tooth dentin

    NASA Astrophysics Data System (ADS)

    Koester, Kurt J.; Ager, Joel W.; Ritchie, Robert O.

    2008-06-01

    Mineralized tissues, such as bone and tooth dentin, serve as structural materials in the human body and, as such, have evolved to resist fracture. In assessing their quantitative fracture resistance or toughness, it is important to distinguish between intrinsic toughening mechanisms, which function ahead of the crack tip, such as plasticity in metals, and extrinsic mechanisms, which function primarily behind the tip, such as crack bridging in ceramics. Bone and dentin derive their resistance to fracture principally from extrinsic toughening mechanisms, which have their origins in the hierarchical microstructure of these mineralized tissues. Experimentally, quantification of these toughening mechanisms requires a crack-growth resistance approach, which can be achieved by measuring the crack-driving force (e.g., the stress intensity) as a function of crack extension (“R-curve approach”). Here this methodology is used to study the effect of aging on the fracture properties of human cortical bone and human dentin in order to discern the microstructural origins of toughness in these materials.

  17. Strain measurement of a mouse bone by 3D-electronic speckle pattern interferometry (3D-ESPI)

    NASA Astrophysics Data System (ADS)

    Samala, Praveen R.; Su, Min; Liu, Sheng; Jiang, Hui H.; Yokota, Hiroki; Yang, Lianxiang

    2005-08-01

    Bone is a mechanosensitive tissue that adapts its mass, architecture and mechanical properties to mechanical loading. Appropriate mechanical loads provide an effective means to stimulate bone remodeling and prevent from bone loss. It is controversial whether in situ strain in bone is a critical determinant in enhancement of bone formation, and it is therefore important to evaluate load-driven strain in bone. Using electronic speckle pattern interferometry, we determined high-resolution three-dimensional strains on the mouse femur in response to two loading modalities: an axial loading modality (ALM) and a knee loading modality (KLM). We demonstrated that these two loading modalities induced a different pattern of strain distributions. ALM generated strain in the midshaft of cortical bone, while strains with KLM were concentrated on the distal epiphysis of the mouse femur. Since KLM is capable of enhancing bone formation in cortical bone distant from the knee, the current results indicate that in situ strain is not always necessary for load-driven bone formation.

  18. Long bone histology of the subterranean rodent Bathyergus suillus (Bathyergidae): ontogenetic pattern of cortical bone thickening.

    PubMed

    Montoya-Sanhueza, Germán; Chinsamy, Anusuya

    2017-02-01

    Patterns of bone development in mammals are best known from terrestrial and cursorial groups, but there is a considerable gap in our understanding of how specializations for life underground affect bone growth and development. Likewise, studies of bone microstructure in wild populations are still scarce, and they often include few individuals and tend to be focused on adults. For these reasons, the processes generating bone microstructural variation at intra- and interspecific levels are not fully understood. This study comprehensively examines the bone microstructure of an extant population of Cape dune molerats, Bathyergus suillus (Bathyergidae), the largest subterranean mammal endemic to the Western Cape of South Africa. The aim of this study is to investigate the postnatal bone growth of B. suillus using undecalcified histological sections (n = 197) of the femur, humerus, tibia-fibula, ulna and radius, including males and females belonging to different ontogenetic and reproductive stages (n = 42). Qualitative histological features demonstrate a wide histodiversity with thickening of the cortex mainly resulting from endosteal and periosteal bone depositions, whilst there is scarce endosteal resorption and remodeling throughout ontogeny. This imbalanced bone modeling allows the tissues deposited during ontogeny to remain relatively intact, thus preserving an excellent record of growth. The distribution of the different bone tissues observed in the cortex depends on ontogenetic status, anatomical features (e.g. muscle attachment structures) and location on the bone (e.g. anterior or lateral). The type of bone microstructure and modeling is discussed in relation to digging behavior, reproduction and physiology of this species. This study is the first histological assessment describing the process of cortical thickening in long bones of a fossorial mammal.

  19. Extensiometric analysis of strain in craniofacial bones during implant-supported palatal expansion.

    PubMed

    Nelson Elias, Carlos; Jogaib Fernandes, Daniel; Souza Zanivan, Denis; Resende Fonseca, Yuri

    2017-05-25

    Palatal expansion has several orthodontic and orthopedic applications, such as increasing maxillary transverse dimensions and correcting maxillary atresia, oral breathing, and skeletal cross-bites. Little is known about the strain to which craniofacial bones are submitted when a palatal expander is loaded. The objectives of the present work were to propose a new palatal bone-borne titanium device (expansion screw), to determine patterns of strain distribution in craniofacial bones during palatal expansion and to show the clinical results of a new palatal expander supported by implants. For in vitro testing, the palatal expander supported by two commercially pure titanium (cp Ti) implants was inserted parallel to the median palatine suture of four dry adult human skulls. Uniaxial and triaxial strain gauges were attached to craniofacial bones and connected to a signal acquisition system. An expansion screw was turned and strain data were collected during palatal expansion. The results showed that the bone strain distribution in craniofacial bones loaded by the palatal bone-borne titanium device was complex: the strain was tensile in the palatine cortical bone and compressive in pterygopalatine processes, nasal bones, and orbital floor. The maximum compressive strain occurs in the upper portion of the pterygopalatine processes and the strain changes from compressive to tensile in the zygomatic process. The experimental results suggest that the bone strain due to the palatal expander is distributed over all craniofacial bones and that the upper portions of pterygopalatine processes are the main sites of resistance to palatal expansion. The new palatal expander supported by two cp Ti implants proposed was employed on adult patient as an illustrative report, where adequate palatal expansion was achieved. The new protocol proposed was less invasive, risky, painful and costless for the correction of moderate maxillary transverse deficiency. Copyright © 2017. Published by

  20. Racial differences in cortical bone and their relationship to biochemical variables in black and white children in the early stages of puberty

    PubMed Central

    Warden, Stuart J.; Hill, Kathleen M.; Ferira, Ashley J.; Laing, Emma M.; Martin, Berdine R.; Hausman, Dorothy B.; Weaver, Connie M.; Peacock, Munro; Lewis, Richard D.

    2014-01-01

    Introduction Racial differences in bone structure likely have roots in childhood as bone size develops predominantly during growth. This study aimed to compare cortical bone health within the tibial diaphysis of black and white children in the early stages of puberty, and explore the contributions of biochemical variables in explaining racial variation in cortical bone properties. Methods A cross-sectional study was performed comparing peripheral quantitative computed tomography-derived cortical bone measures of the tibial diaphysis and biochemical variables in 314 participants (n=155 males; n=164 blacks) in the early stages of puberty. Results Blacks had greater cortical volumetric bone mineral density, mass and size compared to whites (all p<0.01), contributing to blacks having 17.0% greater tibial strength (polar strength-strain index [SSIP]) (p<0.001). Turnover markers indicated blacks had higher bone formation (osteocalcin [OC] and bone specific alkaline phosphatase) and lower bone resorption (N-terminal telopeptide) than whites (all p<0.01). Blacks also had lower 25-hydroxyvitamin D [25(OH)D], and higher 1,25-dihydroxyvitamin D [1,25(OH)2D] and parathyroid hormone (PTH) (all p<0.05). There were no correlations between tibial bone properties, and 25(OH)D and PTH in whites (all p≥0.10); however, SSIP was negatively and positively correlated with 25(OH)D and PTH in blacks, respectively (all p≤0.02). Variation in bone cross-sectional area and SSIP attributable to race was partially explained by tibial length, 25(OH)D/PTH and OC. Conclusions Divergence in tibial cortical bone properties between blacks and whites is established by the early stages of puberty with the enhanced cortical bone properties in black children possibly being explained by higher PTH and OC. PMID:23093348

  1. Post-yield nanomechanics of human cortical bone in compression using synchrotron X-ray scattering techniques.

    SciTech Connect

    Dong, X.N.; Almer, J.D.; Wang, X.

    2011-02-24

    The ultrastructural response to applied loads governs the post-yield deformation and failure behavior of bone, and is correlated with bone fragility fractures. Combining a novel progressive loading protocol and synchrotron X-ray scattering techniques, this study investigated the correlation of the local deformation (i.e., internal strains of the mineral and collagen phases) with the bulk mechanical behavior of bone. The results indicated that the internal strains of the longitudinally oriented collagen fibrils and mineral crystals increased almost linearly with respect to the macroscopic strain prior to yielding, but markedly decreased first and then gradually leveled off after yielding. Similar changes were also observed in the applied stress before and after yielding of bone. However, the collagen to mineral strain ratio remained nearly constant throughout the loading process. In addition, the internal strains of longitudinal mineral and collagen phases did not exhibit a linear relationship with either the modulus loss or the plastic deformation of bulk bone tissue. Finally, the time-dependent response of local deformation in the mineral phase was observed after yielding. Based on the results, we speculate that the mineral crystals and collagen fibrils aligned with the loading axis only partially explain the post-yield deformation, suggesting that shear deformation involving obliquely oriented crystals and fibrils (off axis) is dominant mechanism of yielding for human cortical bone in compression.

  2. Scanning electron microscopy of human cortical bone failure surfaces.

    PubMed

    Braidotti, P; Branca, F P; Stagni, L

    1997-02-01

    Undecalcified samples extracted from human femoral shafts are fractured by bending and the fracture surfaces are examined with a scanning electron microscope (SEM). The investigation is performed on both dry and wet (hydrated with a saline solution) specimens. SEM micrographs show patterns in many respects similar to those observed in fractography studies of laminated fiber-reinforced synthetic composites. In particular, dry and wet samples behave like brittle and ductile matrix laminates, respectively. An analysis carried out on the basis of the mechanisms that dominate the fracture process of laminates shows that a reasonable cortical bone model is that of a laminated composite material whose matrix is composed of extracellular noncollagenous calcified proteins, and the reinforcement is constituted by the calcified collagen fiber system.

  3. Cancellous Screws Are Biomechanically Superior to Cortical Screws in Metaphyseal Bone.

    PubMed

    Wang, Tim; Boone, Christopher; Behn, Anthony W; Ledesma, Justin B; Bishop, Julius A

    2016-09-01

    Cancellous screws are designed to optimize fixation in metaphyseal bone environments; however, certain clinical situations may require the substitution of cortical screws for use in cancellous bone, such as anatomic constraints, fragment size, or available instrumentation. This study compares the biomechanical properties of commercially available cortical and cancellous screw designs in a synthetic model representing various bone densities. Commercially available, fully threaded, 4.0-mm outer-diameter cortical and cancellous screws were tested in terms of pullout strength and maximum insertion torque in standard-density and osteoporotic cancellous bone models. Pullout strength and maximum insertion torque were both found to be greater for cancellous screws than cortical screws in all synthetic densities tested. The magnitude of difference in pullout strength between cortical and cancellous screws increased with decreasing synthetic bone density. Screw displacement prior to failure and total energy absorbed during pullout strength testing were also significantly greater for cancellous screws in osteoporotic models. Stiffness was greater for cancellous screws in standard and osteoporotic models. Cancellous screws have biomechanical advantages over cortical screws when used in metaphyseal bone, implying the ability to both achieve greater compression and resist displacement at the screw-plate interface. Surgeons should preferentially use cancellous over cortical screws in metaphyseal environments where cortical bone is insufficient for fixation. [Orthopedics.2016; 39(5):e828-e832.]. Copyright 2016, SLACK Incorporated.

  4. Relationship of Bone Mineralization Density Distribution (BMDD) in Cortical and Cancellous Bone Within the Iliac Crest of Healthy Premenopausal Women

    PubMed Central

    Dempster, D. W.; Zhou, Hua; Roschger, P.; Fratzl-Zelman, N.; Fratzl, P.; Silverberg, S. J.; Shane, E.; Cohen, A.; Stein, E.; Nickolas, T. L.; Recker, R. R.; Lappe, J.; Bilezikian, J. P.; Klaushofer, K.

    2015-01-01

    Bone mineralization density distribution (BMDD) is an important determinant of bone mechanical properties. The most available skeletal site for access to the BMDD is the iliac crest. Compared to cancellous bone much less information on BMDD is available for cortical bone. Hence, we analyzed complete transiliac crest bone biopsy samples from premenopausal women (n = 73) aged 25–48 years, clinically classified as healthy, by quantitative backscattered electron imaging for cortical (Ct.) and cancellous (Cn.) BMDD. The Ct.BMDD was characterized by the arithmetic mean of the BMDD of the cortical plates. We found correlations between Ct. and Cn. BMDD variables with correlation coefficients r between 0.42 and 0.73 (all p < 0.001). Additionally to this synchronous behavior of cortical and cancellous compartments, we found that the heterogeneity of mineralization densities (Ct.CaWidth), as well as the cortical porosity (Ct.Po) was larger for a lower average degree of mineralization (Ct.CaMean). Moreover, Ct.Po correlated negatively with the percentage of highly mineralized bone areas (Ct.CaHigh) and positively with the percentage of lowly mineralized bone areas (Ct.CaLow). In conclusion, the correlation of cortical with cancellous BMDD in the iliac crest of the study cohort suggests coordinated regulation of bone turnover between both bone compartments. Only in a few cases, there was a difference in the degree of mineralization of >1wt % between both cortices suggesting a possible modeling situation. This normative dataset of healthy premenopausal women will provide a reference standard by which disease- and treatment-specific effects can be assessed at the level of cortical bone BMDD. PMID:25134800

  5. Effect of gamma irradiation on mechanical properties of human cortical bone: influence of different processing methods.

    PubMed

    Kaminski, Artur; Jastrzebska, Anna; Grazka, Ewelina; Marowska, Joanna; Gut, Grzegorz; Wojciechowski, Artur; Uhrynowska-Tyszkiewicz, Izabela

    2012-08-01

    increase in the ultimate strain. The results of our study suggest that there may be an association between mechanical properties of bone tissue grafts and the damage process of collagen structure during gamma irradiation. This collagen damage in cortical bone allografts containing water does not depends on the temperature of irradiation or defatting during processing if dose of gamma irradiation does not exceed 35 kGy.

  6. Skeletal maturity leads to a reduction in the strain magnitudes induced within the bone: a murine tibia study.

    PubMed

    Razi, Hajar; Birkhold, Annette I; Zaslansky, Paul; Weinkamer, Richard; Duda, Georg N; Willie, Bettina M; Checa, Sara

    2015-02-01

    Bone adapts to changes in the local mechanical environment (e.g. strains) through formation and resorption processes. However, the bone adaptation response is significantly reduced with increasing age. The mechanical strains induced within the bone by external loading are determined by bone morphology and tissue material properties. Although it is known that changes in bone mass, architecture and bone tissue quality occur with age, to what extent they contribute to the altered bone adaptation response remains to be determined. This study investigated alterations in strains induced in the tibia of different aged female C57Bl/6J mice (young, 10-week-old; adult, 26-week-old; and elderly, 78-week-old) subjected to in vivo compressive loading. Using a combined in vivo/in silico approach, the strains in the bones were assessed by both strain gauging and finite element modeling experiments. In cortical bone, strain magnitudes induced at the mid-diaphysis decreased by 20% from young to adult mice and by 15% from adult to elderly mice. In the cancellous bone (at the proximal metaphysis), induced strains were 70% higher in young compared with adult and elderly mice. Taking into account previous studies showing a reduced bone adaptation response to mechanical loading in adulthood, these results suggest that the diminished adaptive response is in part due to a reduction in the strains induced within the bone.

  7. Radiographic features of bone in several strains of laboratory mice and of their tumours induced by bone-seeking radionuclides.

    PubMed Central

    Loutit, J F; Corp, M J; Ardran, G M

    1976-01-01

    The natural radiographic appearance of the various bones of the skeleton are described for several strains of laboratory mice. The Harwell substrains of CBA, A and 101 are generally similar and become osteoporotic on ageing. Harwell C57BL have similar, but more delicately chiseled, bones. Harwell C3H mice have bones with stouter cortices and may show osteosclerosis on ageing. CF1 females (donated by Dr M. Finkel) showed osteosclerosis and osteophytic outgrowths when aged. NMRI mice (donated by Dr A. Luz) appeared larger than the pure-strain Harwell mice. In general, mouse bones are simple tubular structures with an ivory cortex and a marrow cavity. Cancellous trabecular bone is scanty, even in vertebrae, flat bones and the metaphyses of long bones. Bone-seeking radionuclides administered to mice lead to skeletal tumours: (a) osteosarcomata, which are commonly radio-opaque to a variable degree owing to calcified tumour bone, but which may be osteolytic, (b) primitive mesenchymal (angio-) sarcomata which are non-osteogenic and osteolytic, (c) fibrosarcomata--which also are osteolytic--and to local or general lymphomata from irradiation of parental cells in bone marrow, but no special radiological features have been found associated with these last-named tumours. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 PMID:1069700

  8. In vivo monitoring of bone architecture and remodeling after implant insertion: The different responses of cortical and trabecular bone.

    PubMed

    Li, Zihui; Kuhn, Gisela; von Salis-Soglio, Marcella; Cooke, Stephen J; Schirmer, Michael; Müller, Ralph; Ruffoni, Davide

    2015-12-01

    The mechanical integrity of the bone-implant system is maintained by the process of bone remodeling. Specifically, the interplay between bone resorption and bone formation is of paramount importance to fully understand the net changes in bone structure occurring in the peri-implant bone, which are eventually responsible for the mechanical stability of the bone-implant system. Using time-lapsed in vivo micro-computed tomography combined with new composite material implants, we were able to characterize the spatio-temporal changes of bone architecture and bone remodeling following implantation in living mice. After insertion, implant stability was attained by a quick and substantial thickening of the cortical shell which counteracted the observed loss of trabecular bone, probably due to the disruption of the trabecular network. Within the trabecular compartment, the rate of bone formation close to the implant was transiently higher than far from the implant mainly due to an increased mineral apposition rate which indicated a higher osteoblastic activity. Conversely, in cortical bone, the higher rate of bone formation close to the implant compared to far away was mostly related to the recruitment of new osteoblasts as indicated by a prevailing mineralizing surface. The behavior of bone resorption also showed dissimilarities between trabecular and cortical bone. In the former, the rate of bone resorption was higher in the peri-implant region and remained elevated during the entire monitoring period. In the latter, bone resorption rate had a bigger value away from the implant and decreased with time. Our approach may help to tune the development of smart implants that can attain a better long-term stability by a local and targeted manipulation of the remodeling process within the cortical and the trabecular compartments and, particularly, in bone of poor health.

  9. Comparative cortical bone thickness between the long bones of humans and five common non-human mammal taxa.

    PubMed

    Croker, Sarah L; Reed, Warren; Donlon, Denise

    2016-03-01

    The task of identifying fragments of long bone shafts as human or non-human is difficult but necessary, for both forensic and archaeological cases, and a fast simple method is particularly useful. Previous literature suggests there may be differences in the thickness of the cortical bone between these two groups, but this has not been tested thoroughly. The aim of this study was not only to test this suggestion, but also to provide data that could be of practical assistance for future comparisons. The major limb bones (humerus, radius, femur and tibia) of 50 Caucasoid adult skeletons of known age and sex were radiographed, along with corresponding skeletal elements from sheep, pigs, cattle, large dogs and kangaroos. Measurements were taken from the radiographs at five points along the bone shaft, of shaft diameter, cortical bone thickness, and a cortical thickness index (sum of cortices divided by shaft diameter) in both anteroposterior and mediolateral orientations. Each variable for actual cortical bone thickness as well as cortical thickness indices were compared between the human group (split by sex) and each of the non-human groups in turn, using Student's t-tests. Results showed that while significant differences did exist between the human groups and many of the non-human groups, these were not all in the same direction. That is, some variables in the human groups were significantly greater than, and others were significantly less than, the corresponding variable in the non-human groups, depending on the particular non-human group, sex of the human group, or variable under comparison. This was the case for measurements of both actual cortical bone thickness and cortical thickness index. Therefore, for bone shaft fragments for which the skeletal element is unknown, the overlap in cortical bone thickness between different areas of different bones is too great to allow identification using this method alone. However, by providing extensive cortical bone

  10. A method for isolating high quality RNA from mouse cortical and cancellous bone.

    PubMed

    Kelly, Natalie H; Schimenti, John C; Patrick Ross, F; van der Meulen, Marjolein C H

    2014-11-01

    The high incidence of fragility fractures in cortico-cancellous bone locations, plus the fact that individual skeletal sites exhibit different responsiveness to load and disease, emphasizes the need to document separately gene expression in cortical and cancellous bone. A further confounding factor is marrow contamination since its high cellularity may effect gene expression measurements. We isolated RNA from cortical and cancellous bone of intact mouse tibiae, and also after marrow removal by flushing or centrifugation. RNA isolated from cancellous bone by each method was sufficient for gene expression analysis. Centrifugation removed contaminating cells more efficiently than flushing, as indexed by histology and decreased expression of Icam4, a highly expressed erythroid gene. In contrast, centrifuged cortical bone had 12- and 13- fold higher expression of the bone-related genes Col1a1 and Bglap, while levels in marrow-free cancellous bone were 30- and 31-fold higher when compared to bone where marrow was left intact. Furthermore, cortical bone had higher expression of Col1a1 and Bglap than cancellous bone. Thus, RNA isolated by this novel approach can reveal site-specific changes in gene expression in cortical and cancellous bone sites.

  11. Effect of porosity, tissue density, and mechanical properties on radial sound speed in human cortical bone.

    PubMed

    Eneh, C T M; Malo, M K H; Karjalainen, J P; Liukkonen, J; Töyräs, J; Jurvelin, J S

    2016-05-01

    The purpose of this study was to investigate the effect of simultaneous changes in cortical porosity, tissue mineral density, and elastic properties on radial speed of sound (SOS) in cortical bone. The authors applied quantitative pulse-echo (PE) ultrasound techniques that hold much potential especially for screening of osteoporosis at primary healthcare facilities. Currently, most PE measurements of cortical thickness, a well-known indicator of fracture risk, use a predefined estimate for SOS in bone to calculate thickness. Due to variation of cortical bone porosity, the use of a constant SOS value propagates to an unknown error in cortical thickness assessment by PE ultrasound. The authors conducted 2.25 and 5.00 MHz focused PE ultrasound time of flight measurements on femoral diaphyses of 18 cadavers in vitro. Cortical porosities of the samples were determined using microcomputed tomography and related to SOS in the samples. Additionally, the effect of cortical bone porosity and mechanical properties of the calcified matrix on SOS was investigated using numerical finite difference time domain simulations. Both experimental measurements and simulations demonstrated significant negative correlation between radial SOS and cortical porosity (R(2) ≥ 0.493, p < 0.01 and R(2) ≥ 0.989, p < 0.01, respectively). When a constant SOS was assumed for cortical bone, the error due to variation of cortical bone porosity (4.9%-16.4%) was about 6% in the cortical thickness assessment in vitro. Use of a predefined, constant value for radial SOS in cortical bone, i.e., neglecting the effect of measured variation in cortical porosity, propagated to an error of 6% in cortical thickness. This error can be critical as characteristic cortical thinning of 1.10% ± 1.06% per yr decreases bending strength of the distal radius and results in increased fragility in postmenopausal women. Provided that the cortical porosity can be estimated in vivo, the relationship between radial SOS and

  12. Effect of porosity, tissue density, and mechanical properties on radial sound speed in human cortical bone

    SciTech Connect

    Eneh, C. T. M. E-mail: markus.malo@uef.fi E-mail: jukka.liukkonen@gmail.com Töyräs, J. E-mail: markus.malo@uef.fi E-mail: jukka.liukkonen@gmail.com Jurvelin, J. S.; Malo, M. K. H. E-mail: markus.malo@uef.fi E-mail: jukka.liukkonen@gmail.com Liukkonen, J. E-mail: markus.malo@uef.fi E-mail: jukka.liukkonen@gmail.com; Karjalainen, J. P. E-mail: markus.malo@uef.fi E-mail: jukka.liukkonen@gmail.com

    2016-05-15

    Purpose: The purpose of this study was to investigate the effect of simultaneous changes in cortical porosity, tissue mineral density, and elastic properties on radial speed of sound (SOS) in cortical bone. The authors applied quantitative pulse-echo (PE) ultrasound techniques that hold much potential especially for screening of osteoporosis at primary healthcare facilities. Currently, most PE measurements of cortical thickness, a well-known indicator of fracture risk, use a predefined estimate for SOS in bone to calculate thickness. Due to variation of cortical bone porosity, the use of a constant SOS value propagates to an unknown error in cortical thickness assessment by PE ultrasound. Methods: The authors conducted 2.25 and 5.00 MHz focused PE ultrasound time of flight measurements on femoral diaphyses of 18 cadavers in vitro. Cortical porosities of the samples were determined using microcomputed tomography and related to SOS in the samples. Additionally, the effect of cortical bone porosity and mechanical properties of the calcified matrix on SOS was investigated using numerical finite difference time domain simulations. Results: Both experimental measurements and simulations demonstrated significant negative correlation between radial SOS and cortical porosity (R{sup 2} ≥ 0.493, p < 0.01 and R{sup 2} ≥ 0.989, p < 0.01, respectively). When a constant SOS was assumed for cortical bone, the error due to variation of cortical bone porosity (4.9%–16.4%) was about 6% in the cortical thickness assessment in vitro. Conclusions: Use of a predefined, constant value for radial SOS in cortical bone, i.e., neglecting the effect of measured variation in cortical porosity, propagated to an error of 6% in cortical thickness. This error can be critical as characteristic cortical thinning of 1.10% ± 1.06% per yr decreases bending strength of the distal radius and results in increased fragility in postmenopausal women. Provided that the cortical porosity can be estimated

  13. An in vitro study of ultrasound signal loss across simple fractures in cortical bone mimics and bovine cortical bone samples.

    PubMed

    Dodd, S P; Cunningham, J L; Miles, A W; Gheduzzi, S; Humphrey, V F

    2007-03-01

    Measurements have been performed on Sawbones and bovine cortical bone samples at 200 kHz using an axial transmission technique to investigate the factors that determine how ultrasonic waves propagate across a simulated fracture. The peak amplitude of the first arrival signal (FAS) was studied. Results taken from intact specimens were compared with those produced when a simple transverse fracture was introduced. These fracture simulation experiments were found to be consistent with Finite Difference modelling of the experimental conditions. The peak amplitude showed a characteristic variation across the fracture caused by interference between reradiated and scattered/diffracted waves at the fracture site and a net Fracture Transmission Loss (FTL). For small fracture gaps, the change in amplitude was sensitive to the presence of the fracture. This sensitivity suggests that this parameter could be a good quantitative indicator for the fracture healing process assuming the relative change in this parameter brought about by healing is measurable.

  14. Bones' Adaptive Response to Mechanical Loading Is Essentially Linear Between the Low Strains Associated With Disuse and the High Strains Associated With the Lamellar/Woven Bone Transition

    PubMed Central

    Sugiyama, Toshihiro; Meakin, Lee B; Browne, William J; Galea, Gabriel L; Price, Joanna S; Lanyon, Lance E

    2012-01-01

    There is a widely held view that the relationship between mechanical loading history and adult bone mass/strength includes an adapted state or “lazy zone” where the bone mass/strength remains constant over a wide range of strain magnitudes. Evidence to support this theory is circumstantial. We investigated the possibility that the “lazy zone” is an artifact and that, across the range of normal strain experience, features of bone architecture associated with strength are linearly related in size to their strain experience. Skeletally mature female C57BL/6 mice were right sciatic neurectomized to minimize natural loading in their right tibiae. From the fifth day, these tibiae were subjected to a single period of external axial loading (40, 10-second rest interrupted cycles) on alternate days for 2 weeks, with a peak dynamic load magnitude ranging from 0 to 14 N (peak strain magnitude: 0–5000 µε) and a constant loading rate of 500 N/s (maximum strain rate: 75,000 µε/s). The left tibiae were used as internal controls. Multilevel regression analyses suggest no evidence of any discontinuity in the progression of the relationships between peak dynamic load and three-dimensional measures of bone mass/strength in both cortical and cancellous regions. These are essentially linear between the low-peak locomotor strains associated with disuse (∼300 µε) and the high-peak strains derived from artificial loading and associated with the lamellar/woven bone transition (∼5000 µε). The strain:response relationship and minimum effective strain are site-specific, probably related to differences in the mismatch in strain distribution between normal and artificial loading at the locations investigated. © 2012 American Society for Bone and Mineral Research. PMID:22431329

  15. Bone strains around immediately loaded implants supporting mandibular overdentures in human cadavers.

    PubMed

    Akça, Kivanç; Akkocaoglu, Murat; Cömert, Ayhan; Tekdemir, Ibrahim; Cehreli, Murat Cavit

    2007-01-01

    To compare the biomechanical effect of splinted versus unsplinted mandibular implants supporting overdentures subjected to experimental static immediate load on bone tissue deformation using strain gauge analysis. Strain gauges were bonded on the labial cortical bone adjacent to 2 Straumann dental implants placed in the mandibular interforaminal region of 4 completely edentulous mandibles of fresh human cadavers. The installation torque value (ITV) of each implant was measured using a custom-made torque wrench, and implant stability quotients (ISQs) were also obtained using resonance frequency analysis. Three overdentures (ODs), 2 splinted (bar- and cantilevered bar-retained) and 1 unsplinted (ball-retained), were fabricated for each edentulous mandible. Two experimental loads were applied subsequently via 2 miniature load cells that were placed bilaterally 10 mm (anterior loading) and 15 mm (posterior loading) from the implant. Strain measurements were performed at a sample rate of 10 KHz and under a maximum experimental static load of 100 N; they were simultaneously monitored from a computer connected to a data acquisition system. Finally, the removal torque values (RTV) of the implants were measured. Strains on the labial cortical bone around implants supporting mandibular ODs under anterior loading were significantly higher than measured under posterior loading for all attachment types (P < .05). All strain values were compressive in nature, and the minimum strain (-19 microepsilon) was recorded for bar-retained ODs under 25 N posterior loading, while the maximum strain (-797 microepsilon) was for recorded for retentive anchor-retained ODs under 100 N anterior loading. Nonparametric correlations between ISQs, ITVs, and RTVs identified significant correlations only for ITVs and RTVs (P < .05). Splinting of 2 interforaminal dental implants, regardless of attachment type, to support mandibular ODs subjected to immediate load significantly reduced initial bone

  16. Fatigue crack growth behavior in equine cortical bone

    NASA Astrophysics Data System (ADS)

    Shelton, Debbie Renee

    2001-07-01

    Objectives for this research were to experimentally determine crack growth rates, da/dN, as a function of alternating stress intensity factor, DeltaK, for specimens from lateral and dorsal regions of equine third metacarpal cortical bone tissue, and to determine if the results were described by the Paris law. In one set of experiments, specimens were oriented for crack propagation in the circumferential direction with the crack plane transverse to the long axis of the bone. In the second set of experiments, specimens were oriented for radial crack growth with the crack plane parallel to the long axis of the bone. Results of fatigue tests from the latter specimens were used to evaluate the hypothesis that crack growth rates differ regionally. The final experiments were designed to determine if crack resistance was dependent on region, proportion of hooped osteons (those with circumferentially oriented collagen fibers in the outer lamellae) or number of osteons penetrated by the crack, and to address the hypothesis that hooped osteons resist invasion by cracks better than other osteonal types. The transverse crack growth data for dorsal specimens were described by the Paris law with an exponent of 10.4 and suggested a threshold stress intensity factor, DeltaKth, of 2.0 MPa·m1/2 and fracture toughness of 4.38 MPa·m 1/2. Similar results were not obtained for lateral specimens because the crack always deviated from the intended path and ran parallel to the loading direction. Crack growth for the dorsal and lateral specimens in the radial orientation was described by the Paris law with exponents of 8.7 and 10.2, respectively, and there were no regional differences in the apparent DeltaK th (0.5 MPa·m1/2) or fracture toughness (1.2 MPa·m 1/2). Crack resistance was not associated with cortical region, proportion of hooped osteons or the number of osteons penetrated by the crack. The extent to which cracks penetrate osteons was influenced by whether the collagen fiber

  17. Effect of surgical fit on integration of cancellous bone and implant cortical bone shear strength for a porous titanium.

    PubMed

    Bertollo, Nicky; Matsubara, Masaaki; Shinoda, Tsuyoshi; Chen, Dong; Kumar, Mukesh; Walsh, William R

    2011-10-01

    Porous scaffold dowels of Ti(6)Al(4)V were prepared and implanted into cancellous and cortical bone sites in adult sheep. Cancellous implants were examined under gap, line-to-line, and press-fit conditions, whereas line-to-line implantation was used in cortical sites. Cortical shear strength increased significantly with time and reached 26.1 ± 8.6 MPa at 12 weeks, accompanied by a concomitant increase in bone integration and remodeling. In cancellous sites, bone integration was well established at 4 and 12 weeks under conditions of press-fit and line-to-line match between implant and surgical defect. New bone growth was also found in the gap conditions, although to a lesser extent. These findings suggest that the porous Ti(6)Al(4)V could prove an effective scaffold material for uncemented fixation in cortical and cancellous sites.

  18. Remodelling of bone and bones: effects of translation and strain on transplants.

    PubMed Central

    Pollard, A. W.; Feik, S. A.; Storey, E.

    1984-01-01

    Tail segments, from 4-day-old Sprague-Dawley rats, consisting of caudal vertebrae (CV) approximately 7-9 were impaled on 0.23-mm diameter Elgiloy wire and transplanted subcutaneously into 50-70 g male hosts to study the effects on transplants of (a) impaling (b) strain and (c) translation. The CV were impaled onto straight lengths of wire to serve as controls (a); onto a wire curved to form a loop and exert a bending force (b) and onto the arms of a spring which moved bones through the surrounding tissues, i.e. translation (c). Tissue changes were studied up to 28 days by radiographic and histological techniques. Control bones grow relatively normally along the straight wire. The CV subjected to strain bend initially and then grow in an arc along the curve of the wire. The outer bone shaft usually becomes straighter while the inner one becomes concave and rarefied. In the translated bones remodelling occurs in a direction generally opposite to the direction of movement but this is modified by the influence of soft tissue tension and pressure. Bone resorbs on the outer leading side under continuous pressure and forms on the inner trailing side under continuous tension. The process is essentially the same as that seen in 'cortical drift'; however, since translation is rapid there is an alteration in the shape of the translated bones as formation on the trailing side is faster than resorption on the leading side.(ABSTRACT TRUNCATED AT 250 WORDS) Images Fig. 4 Fig. 5 Fig. 3 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 PMID:6388616

  19. Analysis of micro fracture in human Haversian cortical bone under compression.

    PubMed

    Jonvaux, J; Hoc, T; Budyn, E

    2012-09-01

    A procedure to investigate local stress intensity factors in human Haversian cortical bone under compression is presented. The method combines a customised experimental setting for micro-compression tests of millimetric bone specimens and a finite element contact model conforming to the bone morphology that tracks advancing microcracks. The non-interpenetration conditions along the crack edges are ensured by penalty constraints of which the parameters are optimised for minimum contact pressure error with respect to the crack orientations. A cohesive crack opening law is implemented in the wake of the crack tips to remain consistent with the progressive tearing of collagen fibrils. The displacement solution is searched by a Newton-Raphson scheme containing a double loop first on the displacements and second on the frictional contact and cohesive condition updates at the crack interfaces. The experimental Dirichlet boundary conditions are acquired by digital image cross-correlation of bone light microscopy observations and then imported into the model. The local mechanical elastic moduli are measured by nanoindentation and microextensometry. The comparison of the macroscopic stress-strain numerical response with the experiment reveals the existence of narrow diffuse damaged zones near the major cracks where the local stress intensity factors can be calculated. Copyright © 2012 John Wiley & Sons, Ltd.

  20. Precision of pQCT-measured total, trabecular and cortical bone area, content, density and estimated bone strength in children

    PubMed Central

    Duff, W.R.D.; Björkman, K.M.; Kawalilak, C.E.; Kehrig, A.M.; Wiebe, S.; Kontulainen, S.

    2017-01-01

    Objectives: To define pQCT precision errors, least-significant-changes, and identify associated factors for bone outcomes at the radius and tibia in children. Methods: We obtained duplicate radius and tibia pQCT scans from 35 children (8-14yrs). We report root-mean-squared coefficient of variation (CV%RMS) and 95% limits-of-agreement to characterize repeatability across scan quality and least-significant-changes for bone outcomes at distal (total and trabecular area, content and density; and compressive bone strength) and shaft sites (total area and content; cortical area content, density and thickness; and torsional bone strength). We used Spearman’s rho to identify associations between CV% and time between measurements, child’s age or anthropometrics. Results: After excluding unanalyzable scans (6-10% of scans per bone site), CV%RMS ranged from 4% (total density) to 19% (trabecular content) at the distal radius, 4% (cortical content) to 8% (cortical thickness) at the radius shaft, 2% (total density) to 14% (trabecular content) at the distal tibia and from 2% (cortical content) to 6% (bone strength) at the tibia shaft. Precision errors were within 95% limits-of-agreement across scan quality. Age was associated (rho -0.4 to -0.5, p <0.05) with CV% at the tibia. Conclusion: Bone density outcomes and cortical bone properties appeared most precise (CV%RMS <5%) in children. PMID:28574412

  1. Overexpression of DMP1 accelerates mineralization and alters cortical bone biomechanical properties in vivo

    SciTech Connect

    Bhatia A.; Miller L.; Albazza, M.; Espinoza Orias, A.A.; Inoue, N.; Acerbo, A.; George, A.; Sumner, D.R.

    2011-09-29

    Dentin matrix protein-1 (DMP1) is a key regulator of biomineralization. Here, we examine changes in structural, geometric, and material properties of cortical bone in a transgenic mouse model overexpressing DMP1. Micro-computed tomography and three-point bending were performed on 90 femora of wild type and transgenic mice at 1, 2, 4, and 6 months. Fourier transform infrared imaging was performed at 2 months. We found that the transgenic femurs were longer (p < 0.01), more robust in cross-section (p < 0.05), stronger (p < 0.05), but had less post-yield strain and displacement (p < 0.01), and higher tissue mineral density (p < 0.01) than the wild type femurs at 1 and 2 months. At 2 months, the transgenic femurs also had a higher mineral-to-matrix ratio (p < 0.05) and lower carbonate substitution (p < 0.05) compared to wild type femurs. These findings indicate that increased mineralization caused by overexpressing DMP1 led to increased structural cortical bone properties associated with decreased ductility during the early post-natal period.

  2. Absorbed fractions for alpha-particles in tissues of cortical bone

    NASA Astrophysics Data System (ADS)

    Watchman, Christopher J.; Bolch, Wesley E.

    2009-10-01

    Bone-seeking alpha-particle emitting radionuclides are common health physics hazards. Additionally, they are under consideration as an option for therapeutic molecular radiotherapy applications. Current dose models do not account for energy or bone-site dependence as shown by alpha-particle absorbed fractions given in ICRP Publication 30. Energy-dependent, yet bone-site independent, alpha-particle absorbed fractions have been presented by the models of Stabin and Siegel (2003 Health Phys. 85 294-310). In this work, a chord-based computational model of alpha-particle transport in cortical bone has been developed that explicitly accounts for both the bone-site and particle-energy dependence of alpha-particle absorbed fractions in this region of the skeleton. The model accounts for energy deposition to three targets: cortical endosteum, haversian space tissues and cortical bone. Path length distributions for cortical bone given in Beddoe (1977 Phys. Med. Biol. 22 298-308) provided additional transport regions in the absorbed fraction calculation. Significant variations in absorbed fractions between different skeletal sites were observed. Differences were observed between this model and the absorbed fractions given in ICRP Publication 30, which varied by as much as a factor of 2.1 for a cortical bone surface source irradiating cortical endosteum.

  3. NOTE: New tissue substitutes representing cortical bone and adipose tissue in quantitative radiology

    NASA Astrophysics Data System (ADS)

    Sanada, Shigeru; Kawahara, Kazuhiro; Yamamoto, Tomoyuki; Takashima, Tsutomu

    1999-06-01

    To employ quantitative radiology more accurately, we examined phantom materials for cortical bone and adipose tissue as calibration standards and as experimental phantoms. New tissue substitutes for cortical bone and adipose tissue composed of liquid phantom were verified by computing their attenuation coefficients and observing their chemical properties. We showed that a potassium pyrophosphate (K4P2O7) solution for cortical bone was comparable to a dipotassium hydrogen phosphate (K2HPO4) solution. Also, the use of methyl alcohol for adipose tissue was more suitable than ethyl alcohol as a phantom material because of its physical and chemical properties.

  4. AGE-RELATED FACTORS AFFECTING THE POST-YIELD ENERGY DISSIPATION OF HUMAN CORTICAL BONE

    PubMed Central

    Nyman, Jeffry S.; Roy, Anuradha; Tyler, Jerrod H.; Acuna, Rae L.; Gayle, Heather J.; Wang, Xiaodu

    2007-01-01

    The risk of bone fracture depends in part on the quality of the tissue, not just the size and mass. This study assessed the post-yield energy dissipation of cortical bone in tension as a function of age and composition. Tensile specimens were prepared from tibiae of human cadavers in which male and female donors were divided into two age groups: middle aged (51 to 56 years old, n = 9) and elderly (72 to 90 years old, n = 8). By loading, unloading, and reloading a specimen with rest period inserted in between, tensile properties at incremental strain levels were assessed. In addition, the post-yield toughness was estimated and partitioned as follows: plastic strain energy related to permanent deformation, released elastic strain energy related to stiffness loss, and hysteresis energy related to viscous behavior. Porosity, mineral and collagen content, and collagen crosslinks of each specimen were also measured to determine the micro and ultrastructural properties of the tissue. It was found that age affected all the energy terms plus strength but not elastic stiffness. The post-yield energy terms were correlated with porosity, pentosidine (a marker of non-enzymatic crosslinks), and collagen content, all of which significantly varied with age. General linear models with the highest possible R2 value suggested that the pentosidine concentration and collagen content provided the best explanation of the age-related decrease in the post-yield energy dissipation of bone. Among them, pentosidine concentration had the greatest contribution to plastic strain energy and was the best explanatory variable of damage accumulation. PMID:17266142

  5. Cortical bone finite element models in the estimation of experimentally measured failure loads in the proximal femur.

    PubMed

    Koivumäki, Janne E M; Thevenot, Jérôme; Pulkkinen, Pasi; Kuhn, Volker; Link, Thomas M; Eckstein, Felix; Jämsä, Timo

    2012-10-01

    Highly accurate nonlinear finite element (FE) models have been presented to estimate bone fracture load. However, these complex models require high computational capacity, which restricts their clinical applicability. The objective of this experimental FE study was to assess the predictive value of a more simple cortical bone simulation model in the estimation of experimentally measured fracture load of the proximal femur. The prediction was compared with that of DXA, and with the prediction of our previous, more complex FE model including trabecular bone. Sixty-one formalin-fixed cadaver femora (from 41 women and 20 men, age 55-100 years) were scanned using a multi-detector CT and were mechanically tested for failure in a sideways fall loading configuration. Trabecular bone was completely removed from the FE models and only cortical bone was analyzed. The training set FE models (N=21) was used to establish the stress and strain thresholds for the element failure criteria. Bi-linear elastoplastic FE analysis was performed based on the CT images. The validation set (N=40) was used to estimate the fracture load. The estimated fracture load values were highly correlated with the experimental data (r(2)=0.73; p<0.001). The slope was 1.128, with an intercept of -360 N, which was not significantly different from 1 and 0, respectively. DXA-based BMD and BMC correlated moderately with the fracture load (r(2)=0.41 and r(2)=0.40, respectively). The study shows that the proximal femoral failure load in a sideways fall configuration can be estimated with reasonable accuracy by using the CT-based bi-linear elastoplastic cortical bone FE model. This model was more predictive for fracture load than DXA and only slightly less accurate than a full bone FE model including trabecular bone. The accuracy and calculation time of the model give promises for clinical use.

  6. Regional, ontogenetic, and sex-related variations in elastic properties of cortical bone in baboon mandibles

    PubMed Central

    Wang, Qian; Ashley, Dennis W.; Dechow, Paul C.

    2010-01-01

    Understanding the mechanical features of cortical bone and their changes with growth and adaptation to function plays an important role in our ability to interpret the morphology and evolution of craniofacial skeletons. We assessed the elastic properties of cortical bone of juvenile and adult baboon mandibles using ultrasonic techniques. Results showed that, overall, cortical bone from baboon mandibles could be modeled as an orthotropic elastic solid. There were significant differences in the directions of maximum stiffness, thickness, density, and elastic stiffness among different functional areas, indicating regional adaptations. After maturity, the cortical bone becomes thicker, denser, and stiffer, but less anisotropic. There were differences in elastic properties of the corpus and ramus between male and female mandibles which are not observed in human mandibles. There were correlations between cortical thicknesses and densities, between bone elastic properties and microstructural configuration, and between the directions of maximum stiffness and bone anatomical axes in some areas. The relationships between bone extrinsic and intrinsic properties bring us insights into the integration of form and function in craniofacial skeletons and suggest that we need to consider both macroscopic form, microstructural variation, and the material properties of bone matrix when studying the functional properties and adaptive nature of the craniofacial skeleton in primates. The differences between baboon and human mandibles is at variance to the pattern of differences in crania, suggesting differences in bone adaption to varying skeletal geometries and loading regimes at both phylogenetic and ontogenetic levels. PMID:19927280

  7. Bones' adaptive response to mechanical loading is essentially linear between the low strains associated with disuse and the high strains associated with the lamellar/woven bone transition.

    PubMed

    Sugiyama, Toshihiro; Meakin, Lee B; Browne, William J; Galea, Gabriel L; Price, Joanna S; Lanyon, Lance E

    2012-08-01

    There is a widely held view that the relationship between mechanical loading history and adult bone mass/strength includes an adapted state or "lazy zone" where the bone mass/strength remains constant over a wide range of strain magnitudes. Evidence to support this theory is circumstantial. We investigated the possibility that the "lazy zone" is an artifact and that, across the range of normal strain experience, features of bone architecture associated with strength are linearly related in size to their strain experience. Skeletally mature female C57BL/6 mice were right sciatic neurectomized to minimize natural loading in their right tibiae. From the fifth day, these tibiae were subjected to a single period of external axial loading (40, 10-second rest interrupted cycles) on alternate days for 2 weeks, with a peak dynamic load magnitude ranging from 0 to 14 N (peak strain magnitude: 0-5000 µε) and a constant loading rate of 500 N/s (maximum strain rate: 75,000 µε/s). The left tibiae were used as internal controls. Multilevel regression analyses suggest no evidence of any discontinuity in the progression of the relationships between peak dynamic load and three-dimensional measures of bone mass/strength in both cortical and cancellous regions. These are essentially linear between the low-peak locomotor strains associated with disuse (∼300 µε) and the high-peak strains derived from artificial loading and associated with the lamellar/woven bone transition (∼5000 µε). The strain:response relationship and minimum effective strain are site-specific, probably related to differences in the mismatch in strain distribution between normal and artificial loading at the locations investigated.

  8. The influence of collagen fiber orientation and other histocompositional characteristics on the mechanical properties of equine cortical bone.

    PubMed

    Skedros, John G; Dayton, Michael R; Sybrowsky, Christian L; Bloebaum, Roy D; Bachus, Kent N

    2006-08-01

    This study examined relative influences of predominant collagen fiber orientation (CFO), mineralization (% ash), and other microstructural characteristics on the mechanical properties of equine cortical bone. Using strain-mode-specific (S-M-S) testing (compression testing of bone habitually loaded in compression; tension testing of bone habitually loaded in tension), the relative mechanical importance of CFO and other material characteristics were examined in equine third metacarpals (MC3s). This model was chosen since it had a consistent non-uniform strain distribution estimated by finite element analysis (FEA) near mid-diaphysis of a thoroughbred horse, net tension in the dorsal/lateral cortices and net compression in the palmar/medial cortices. Bone specimens from regions habitually loaded in tension or compression were: (1) tested to failure in both axial compression and tension in order to contrast S-M-S vs non-S-M-S behavior, and (2) analyzed for CFO, % ash, porosity, fractional area of secondary osteonal bone, osteon cross-sectional area, and population densities of secondary osteons and osteocyte lacunae. Multivariate multiple regression analyses revealed that in S-M-S compression testing, CFO most strongly influenced total energy (pre-yield elastic energy plus post-yield plastic energy); in S-M-S tension testing CFO most strongly influenced post-yield energy and total energy. CFO was less important in explaining S-M-S elastic modulus, and yield and ultimate stress. Therefore, in S-M-S loading CFO appears to be important in influencing energy absorption, whereas the other characteristics have a more dominant influence in elastic modulus, pre-yield behavior and strength. These data generally support the hypothesis that differentially affecting S-M-S energy absorption may be an important consequence of regional histocompositional heterogeneity in the equine MC3. Data inconsistent with the hypothesis, including the lack of highly longitudinal collagen in the

  9. Clinically-Compatible MRI Strategies for Discriminating Bound and Pore Water in Cortical Bone

    PubMed Central

    Horch, R. Adam; Gochberg, Daniel F.; Nyman, Jeffry S.; Does, Mark D.

    2012-01-01

    Advances in modern MRI pulse sequences have enabled clinically-practical cortical bone imaging. Human cortical bone is known to contain a distribution of T1 and T2 components attributed to bound and pore water, although clinical imaging approaches have yet to discriminate bound from pore water on the basis of their relaxation properties. Herein, two clinically-compatible MRI strategies are proposed for selectively imaging either bound or pore water by utilizing differences in their T1s and T2s. The strategies are validated in a population of ex vivo human cortical bones, and estimates obtained for bound and pore water are compared to bone mechanical properties. Results show that the two MRI strategies provide good estimates of bound and pore water that correlate to bone mechanical properties. As such, the strategies for bound and pore water-discrimination shown herein should provide diagnostically useful tools for assessing bone fracture risk, once applied to clinical MRI. PMID:22294340

  10. Mixed-mode toughness of human cortical bone containing a longitudinal crack in far-field compression.

    PubMed

    Olvera, Diana; Zimmermann, Elizabeth A; Ritchie, Robert O

    2012-01-01

    Bone is generally loaded under multiaxial conditions in vivo; as it invariably contains microcracks, this leads to complex mixed-mode stress-states involving combinations of tension, compression and shear. In previous work on the mixed-mode loading of human cortical bone (using an asymmetric bend test geometry), we found that the bone toughness was lower when loaded in far-field shear than in tension (opposite to the trend in most brittle materials), although only for the transverse orientation. This is a consequence of the competition between preferred mechanical vs. microstructural crack-path directions, the former dictated by the direction of the maximum mechanical "driving force" (which changes with the mode-mixity), and the latter by the "weakest" microstructural path (which in human bone is along the osteonal interfaces or cement lines). As most microcracks are oriented longitudinally, we investigate here the corresponding mixed-mode toughness of human cortical bone in the longitudinal (proximal-distal) orientation using a "double cleavage drilled compression" test geometry, which provides a physiologically-relevant loading condition for bone in that it characterizes the toughness of a longitudinal crack loaded in far-field compression. In contrast to the transverse toughness, results show that the longitudinal toughness, measured using the strain-energy release rate, is significantly higher in shear (mode II) than in tension (mode I). This is consistent, however, with the individual criteria of preferred mechanical vs. microstructural crack paths being commensurate in this orientation.

  11. Trabecular and Cortical Bone of Growing C3H Mice Is Highly Responsive to the Removal of Weightbearing

    PubMed Central

    Judex, Stefan

    2016-01-01

    Genetic make-up strongly influences the skeleton’s susceptibility to the loss of weight bearing with some inbred mouse strains experiencing great amounts of bone loss while others lose bone at much smaller rates. At young adulthood, female inbred C3H/HeJ (C3H) mice are largely resistant to catabolic pressure induced by unloading. Here, we tested whether the depressed responsivity to unloading is inherent to the C3H genetic make-up or whether a younger age facilitates a robust skeletal response to unloading. Nine-week-old, skeletally immature, female C3H mice were subjected to 3wk of hindlimb unloading (HLU, n = 12) or served as normal baseline controls (BC, n = 10) or age-matched controls (AC, n = 12). In all mice, cortical and trabecular architecture of the femur, as well as levels of bone formation and resorption, were assessed with μCT, histomorphometry, and histology. Changes in bone marrow progenitor cell populations were determined with flow cytometry. Following 21d of unloading, HLU mice had 52% less trabecular bone in the distal femur than normal age-matched controls. Reflecting a loss of trabecular tissue compared to baseline controls, trabecular bone formation rates (BFR/BS) in HLU mice were 40% lower than in age-matched controls. Surfaces undergoing osteoclastic resorption were not significantly different between groups. In the mid-diaphysis, HLU inhibited cortical bone growth leading to 14% less bone area compared to age-matched controls. Compared to AC, BFR/BS of HLU mice were 53% lower at the endo-cortical surface and 49% lower at the periosteal surface of the mid-diaphysis. The enriched osteoprogenitor cell population (OPC) comprised 2% of the bone marrow stem cells in HLU mice, significantly different from 3% OPC in the AC group. These data show that bone tissue in actively growing C3H mice is lost rapidly, or fails to grow, during the removal of functional weight bearing—in contrast to the insignificant response previously demonstrated in

  12. Isthmus-guided cortical bone trajectory for pedicle screw insertion.

    PubMed

    Iwatsuki, Koichi; Yoshimine, Toshiki; Ohnishi, Yu-ichiro; Ninomiya, Kosi; Ohkawa, Toshika

    2014-08-01

    Herein is described cortical bone trajectory (CBT), a new path for pedicle screw insertion for lumbar vertebral fusion. Because the points of insertion are under the end of the inferior articular process, and because the screws are inserted toward the lateral side, there is less soft tissue development than with the conventional technique; the CBT technique therefore enables less invasive surgery than the conventional technique. However, it has some drawbacks. For example, in the original CBT approach, the points of insertion are in the vicinity of the end of the inferior articular process. Because this joint has been destroyed in many patients who have indications for intervertebral fusion surgery, it is sometimes difficult to use it as a reference point for screw insertion location. With severe lateral slippage, the screw insertion site can become significantly dislocated sideways, with possible resultant damaging to the spinal canal and/or nerve root. The CBT technique here involved inserting the screws while keeping clear of the intervertebral foramen with the assistance of side view X-ray fluoroscopy and using the end of the inferior articular process and the isthmus as points of reference for screw location.

  13. Histomorphometric and osteocytic characteristics of cortical bone in male subtrochanteric femoral shaft.

    PubMed

    Tong, Xiaoyu; Malo, Markus K H; Burton, Inari S; Jurvelin, Jukka S; Isaksson, Hanna; Kröger, Heikki

    2017-08-07

    The histomorphometric properties of the subtrochanteric femoral region have rarely been investigated. The aim of this study was to investigate the age-associated variations and regional differences of histomorphometric and osteocytic properties in the cortical bone of the subtrochanteric femoral shaft, and the association between osteocytic and histological cortical bone parameters. Undecalcified histological sections of the subtrochanteric femoral shaft were obtained from cadavers (n = 20, aged 18-82 years, males). They were cut and stained using modified Masson-Goldner stain. Histomorphometric parameters of cortical bone were analysed with ×50 and ×100 magnification after identifying cortical bone boundaries using our previously validated method. Within cortical bone areas, only complete osteons with typical concentric lamellae and cement line were selected and measured. Osteocytic parameters of cortical bone were analyzed under phase contrast microscopy and epifluorescence within microscopic fields (0.55 mm(2) for each). The cortical widths of the medial and lateral quadrants were significantly higher than other quadrants (P < 0.01). Osteonal area per cortical bone area was lower and cortical porosities were higher in the posterior quadrant than in the other quadrants (P < 0.05). Osteocyte lacunar number per cortical bone area was found higher in the young subjects (≤ 50 years) than in the older ones (> 50 years) both before and after adjustments for body height and weight (P < 0.05). Moreover, significant but low correlations were found between the cortical bone and osteocytic parameters (0.20 ≤ R(2)  ≤ 0.35, P < 0.05). It can be concluded that in healthy males, the cortical histomorphometric parameters differ between the anatomical regions of the subtrochanteric femoral shaft, and are correlated with the osteocytic parameters from the same site. These findings may be of use when discussing mechanisms that predispose patients to

  14. Adaptations of young adult rat cortical bone to 14 days of spaceflight

    NASA Technical Reports Server (NTRS)

    Vailas, A. C.; Vanderby, R., Jr.; Martinez, D. A.; Ashman, R. B.; Ulm, M. J.; Grindeland, R. E.; Durnova, G. N.; Kaplanskii, A.

    1992-01-01

    To determine whether mature humeral cortical bone would be modified significantly by an acute exposure to weightlessness, adult rats (110 days old) were subjected to 14 days of microgravity on the COSMOS 2044 biosatellite. There were no significant changes in peak force, stiffness, energy to failure, and displacement at failure in the flight rats compared with ground-based controls. Concentrations and contents of hydroxyproline, calcium, and mature stable hydroxylysylpyridinoline and lysylpyridinoline collagen cross-links remained unchanged after spaceflight. Bone lengths, cortical and endosteal areas, and regionl thicknesses showed no significant differences between flight animals and ground controls. The findings suggest that responsiveness of cortical bone to microgravity is less pronounced in adult rats than in previous spaceflight experiments in which young growing animals were used. It is hypothesized that 14 days of spaceflight may not be sufficient to impact the biochemical and biomechanical properties of cortical bone in the mature rat skeleton.

  15. Adaptations of young adult rat cortical bone to 14 days of spaceflight

    NASA Technical Reports Server (NTRS)

    Vailas, A. C.; Vanderby, R., Jr.; Martinez, D. A.; Ashman, R. B.; Ulm, M. J.; Grindeland, R. E.; Durnova, G. N.; Kaplanskii, A.

    1992-01-01

    To determine whether mature humeral cortical bone would be modified significantly by an acute exposure to weightlessness, adult rats (110 days old) were subjected to 14 days of microgravity on the COSMOS 2044 biosatellite. There were no significant changes in peak force, stiffness, energy to failure, and displacement at failure in the flight rats compared with ground-based controls. Concentrations and contents of hydroxyproline, calcium, and mature stable hydroxylysylpyridinoline and lysylpyridinoline collagen cross-links remained unchanged after spaceflight. Bone lengths, cortical and endosteal areas, and regionl thicknesses showed no significant differences between flight animals and ground controls. The findings suggest that responsiveness of cortical bone to microgravity is less pronounced in adult rats than in previous spaceflight experiments in which young growing animals were used. It is hypothesized that 14 days of spaceflight may not be sufficient to impact the biochemical and biomechanical properties of cortical bone in the mature rat skeleton.

  16. The Hounsfield value for cortical bone geometry in the proximal humerus--an in vitro study.

    PubMed

    Lim Fat, Daren; Kennedy, Jim; Galvin, Rose; O'Brien, Fergal; Mc Grath, Frank; Mullett, Hannan

    2012-05-01

    Fractures of the proximal humerus represent a major osteoporotic burden. Recent developments in CT imaging have emphasized the importance of cortical bone thickness distribution in the prevention and management of fragility fractures. We aimed to experimentally define the CT density of cortical bone in the proximal humerus for building cortical geometry maps. With ethical approval, we used ten fresh-frozen human proximal humeri. These were stripped of all soft tissue and high-resolution CT images were then taken. The humeral heads were then subsequently resected to allow access to the metaphyseal area. Using curettes, cancellous bone was removed down to hard cortical bone. Another set of CT images of the reamed specimen was then taken. Using CT imaging software and a CAD interface, we then compared cortical contours at different CT density thresholds to the reference inner cortical contour of our reamed specimens. Working with 3D model representations of these cortical maps, we were able to accurately make distance comparison analyses based on different CT thresholds. We could compute a single closest value at 700 HU. No difference was found in the HU-based contours generated along the 500-900 HU pixels (p = 1.000). The contours were significantly different from those generated at 300, 400, 1,000, and 1,100 HU. A Hounsfield range of 500-900 HU can accurately depict cortical bone geometry in the proximal humerus. Thresholding outside this range leads to statistically significant inaccuracies. Our results concur with a similar range reported in the literature for the proximal femur. Knowledge of regional variations in cortical bone thickness has direct implications for basic science studies on osteoporosis and its treatment, but is also important for the orthopedic surgeon since our decision for treatment options is often guided by local bone quality.

  17. In vitro study of adhesive polymethylmethacrylate bone cement bonding to cortical bone in maxillofacial surgery.

    PubMed

    Smeets, Ralf; Marx, Rudolf; Kolk, Andreas; Said-Yekta, Sareh; Grosjean, Maurice B; Stoll, Christian; Tinschert, Joachim; Wirtz, Dieter C; Riediger, Dieter; Endres, Kira

    2010-12-01

    In the treatment of midface fractures, the fragments are immobilized using screws and plates for osteosynthesis until reunion has occurred. This method involves drilling holes for the insertion of the screws, which can be associated with additional fracturing of the corresponding bone owing to the complex architecture and thin layers of facial bone. To alleviate this problem, new adhesive techniques for fixing the plates for osteosynthesis have been investigated, mitigating the detrimental effects of screw hole drilling. In the present experimental study, the strength of this adhesive bond and its resistance to hydrolysis were investigated. To determine the adhesive bonding strength, a tension test was implemented. Osteosynthesis plates with screw holes 1.3 mm in diameter were fixed to cortical bone samples of bovine femur using ultraviolet (UV) light-curing polymethylmethacrylate bone cement. To facilitate bonding, the surface of the bone was conditioned with an amphiphilic bonding agent before cementing. UV light curing was implemented using either a conventional UV unit, such as is used in dentistry, or with a specialized UV unit with a limited emission spectrum but high luminosity. Reference control samples were prepared without application of the bone bonding agent. After this procedure, the samples were stored for 1 to 7 days at 37°C submerged in 0.9% saline solution before being subjected to the tension test. Without the bone bonding agent, the bonding strength was 0.2 MPa. The primary average bonding strength at day 0 was 8.5 MPa when cured with the conventional UV unit and 14 MPa for the samples cured with the specialized UV unit. An almost constant average bond strength of 8 and 16 MPa was noted for all samples stored up to 7 days after curing with the conventional and specialized UV unit, respectively. With the development of a new bone bonding agent, a method is now available to promote the bonding between the hydrophilic bone surface and the

  18. Post-traumatic transient cortical blindness in a child with occipital bone fracture.

    PubMed

    Ng, Rachel H C

    2016-12-01

    Cortical blindness as sequelae of trauma has been reported in literature but mostly in the setting of occipital cortex or visual tract damages. We present a case of transient cortical blindness in a child following a closed head injury with a non-displaced occipital bone fracture and underlying occipital lobe contusion. We discuss the pathophysiology behind Post-traumatic transient cortical blindness, relevant investigations, and current management. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Chemical and structural characterization of the mineral phase from cortical and trabecular bone.

    PubMed

    Bigi, A; Cojazzi, G; Panzavolta, S; Ripamonti, A; Roveri, N; Romanello, M; Noris Suarez, K; Moro, L

    1997-10-01

    X-ray diffraction, infrared spectroscopy and chemical investigations have been carried out on the inorganic phases from rat cortical and trabecular bone. Although both inorganic phases consist of poorly crystalline B carbonated apatite, several significant differences have been observed. In particular, trabecular bone apatite displays reduced crystallite sizes, Ca/P molar ratio, and carbonate content, and exhibits a greater extent of thermal conversion into beta-tricalcium phosphate than cortical bone apatite. These differences can be related to the different extents of collagen posttranslational modifications exhibited by the two types of bone, in agreement with their different biological functions.

  20. The high bone mass phenotype is characterised by a combined cortical and trabecular bone phenotype: findings from a pQCT case-control study.

    PubMed

    Gregson, Celia L; Sayers, Adrian; Lazar, Victor; Steel, Sue; Dennison, Elaine M; Cooper, Cyrus; Smith, George Davey; Rittweger, Jörn; Tobias, Jon H

    2013-01-01

    High bone mass (HBM), detected in 0.2% of DXA scans, is characterised by a mild skeletal dysplasia largely unexplained by known genetic mutations. We conducted the first systematic assessment of the skeletal phenotype in unexplained HBM using pQCT in our unique HBM population identified from screening routine UK NHS DXA scans. pQCT measurements from the mid and distal tibia and radius in 98 HBM cases were compared with (i) 65 family controls (constituting unaffected relatives and spouses), and (ii) 692 general population controls. HBM cases had substantially greater trabecular density at the distal tibia (340 [320, 359] mg/cm(3)), compared to both family (294 [276, 312]) and population controls (290 [281, 299]) (p<0.001 for both, adjusted for age, gender, weight, height, alcohol, smoking, malignancy, menopause, steroid and estrogen replacement use). Similar results were obtained at the distal radius. Greater cortical bone mineral density (cBMD) was observed in HBM cases, both at the midtibia and radius (adjusted p<0.001). Total bone area (TBA) was higher in HBM cases, at the distal and mid tibia and radius (adjusted p<0.05 versus family controls), suggesting greater periosteal apposition. Cortical thickness was increased at the mid tibia and radius (adjusted p<0.001), implying reduced endosteal expansion. Together, these changes resulted in greater predicted cortical strength (strength strain index [SSI]) in both tibia and radius (p<0.001). We then examined relationships with age; tibial cBMD remained constant with increasing age amongst HBM cases (adjusted β -0.01 [-0.02, 0.01], p=0.41), but declined in family controls (-0.05 [-0.03, -0.07], p<0.001) interaction p=0.002; age-related changes in tibial trabecular BMD, CBA and SSI were also divergent. In contrast, at the radius HBM cases and controls showed parallel age-related declines in cBMD and trabecular BMD. HBM is characterised by increased trabecular BMD and by alterations in cortical bone density and

  1. Functional adaptation to mechanical loading in both cortical and cancellous bone is controlled locally and is confined to the loaded bones

    PubMed Central

    Sugiyama, Toshihiro; Price, Joanna S.; Lanyon, Lance E.

    2010-01-01

    In order to validate whether bones' functional adaptation to mechanical loading is a local phenomenon, we randomly assigned 21 female C57BL/6 mice at 19 weeks of age to one of three equal numbered groups. All groups were treated with isoflurane anesthesia three times a week for 2 weeks (approximately 7 min/day). During each anaesthetic period, the right tibiae/fibulae in the DYNAMIC + STATIC group were subjected to a peak dynamic load of 11.5 N (40 cycles with 10-s intervals between cycles) superimposed upon a static “pre-load” of 2.0 N. This total load of 13.5 N engendered peak longitudinal strains of approximately 1400 microstrain on the medial surface of the tibia at a middle/proximal site. The right tibiae/fibulae in the STATIC group received the static “pre-load” alone while the NOLOAD group received no artificial loading. After 2 weeks, the animals were sacrificed and both tibiae, fibulae, femora, ulnae and radii analyzed by three-dimensional high-resolution (5 μm) micro-computed tomography (μCT). In the DYNAMIC + STATIC group, the proximal trabecular percent bone volume and cortical bone volume at the proximal and middle levels of the right tibiae as well as the cortical bone volume at the middle level of the right fibulae were markedly greater than the left. In contrast, the left bones in the DYNAMIC + STATIC group showed no differences compared to the left or right bones in the NOLOAD or STATIC group. These μCT data were confirmed by two-dimensional examination of fluorochrome labels in bone sections which showed the predominantly woven nature of the new bone formed in the loaded bones. We conclude that the adaptive response in both cortical and trabecular regions of bones subjected to short periods of dynamic loading, even when this response is sufficiently vigorous to stimulate woven bone formation, is confined to the loaded bones and does not involve changes in other bones that are adjacent, contra-lateral or remote to them

  2. Functional adaptation to mechanical loading in both cortical and cancellous bone is controlled locally and is confined to the loaded bones.

    PubMed

    Sugiyama, Toshihiro; Price, Joanna S; Lanyon, Lance E

    2010-02-01

    In order to validate whether bones' functional adaptation to mechanical loading is a local phenomenon, we randomly assigned 21 female C57BL/6 mice at 19 weeks of age to one of three equal numbered groups. All groups were treated with isoflurane anesthesia three times a week for 2 weeks (approximately 7 min/day). During each anaesthetic period, the right tibiae/fibulae in the DYNAMIC+STATIC group were subjected to a peak dynamic load of 11.5 N (40 cycles with 10-s intervals between cycles) superimposed upon a static "pre-load" of 2.0 N. This total load of 13.5 N engendered peak longitudinal strains of approximately 1400 microstrain on the medial surface of the tibia at a middle/proximal site. The right tibiae/fibulae in the STATIC group received the static "pre-load" alone while the NOLOAD group received no artificial loading. After 2 weeks, the animals were sacrificed and both tibiae, fibulae, femora, ulnae and radii analyzed by three-dimensional high-resolution (5 mum) micro-computed tomography (microCT). In the DYNAMIC+STATIC group, the proximal trabecular percent bone volume and cortical bone volume at the proximal and middle levels of the right tibiae as well as the cortical bone volume at the middle level of the right fibulae were markedly greater than the left. In contrast, the left bones in the DYNAMIC+STATIC group showed no differences compared to the left or right bones in the NOLOAD or STATIC group. These microCT data were confirmed by two-dimensional examination of fluorochrome labels in bone sections which showed the predominantly woven nature of the new bone formed in the loaded bones. We conclude that the adaptive response in both cortical and trabecular regions of bones subjected to short periods of dynamic loading, even when this response is sufficiently vigorous to stimulate woven bone formation, is confined to the loaded bones and does not involve changes in other bones that are adjacent, contra-lateral or remote to them. (c) 2009 Elsevier Inc

  3. Damage mechanisms and failure modes of cortical bone under components of physiological loading.

    PubMed

    George, W T; Vashishth, D

    2005-09-01

    Fatigue damage development in cortical bone was investigated in vitro under different mechanical components of physiological loading including tension, compression, and torsion. During each test, stress and strain data were collected continuously to monitor and statistically determine the occurrence of the primary, secondary, and tertiary stages associated with fatigue and/or creep failure of bone. The resultant microdamage and failure modes were identified by histological and fractographic analysis, respectively. The tensile group demonstrated Mode I cracking and the three classic stages of fatigue and creep suggesting a low crack initiation threshold, steady crack propagation and final failure by coalescence of microcracks. In contrast, the compressive group displayed Mode II cracking and a two-stage fatigue behavior with limited creep suggesting a high crack initiation threshold followed by a sudden fracture. The torsion group also displayed a two-stage fatigue profile but demonstrated extensive damage from mixed mode (Modes II and III) microcracking and predominant time-dependent damage. Thus, fatigue behavior of bone was found to be uniquely related to the individual mechanical components of physiological loading and the latter determined the specific damage mechanisms associated with fatigue fracture.

  4. Lipids and collagen matrix restrict the hydraulic permeability within the porous compartment of adult cortical bone.

    PubMed

    Wen, Demin; Androjna, Caroline; Vasanji, Amit; Belovich, Joanne; Midura, Ronald J

    2010-03-01

    In vivo the hydraulic permeability of cortical bone influences the transport of nutrients, waste products and signaling molecules, thus influencing the metabolic functions of osteocytes and osteoblasts. In the current study two hypotheses were tested: the presence of (1) lipids and (2) collagen matrix in the porous compartment of cortical bone restricts its permeability. Our approach was to measure the radial permeability of adult canine cortical bone before and after extracting lipids with acetone-methanol, and before and after digesting collagen with bacterial collagenase. Our results showed that the permeability of adult canine cortical bone was below 4.0x10(-17) m2, a value consistent with prior knowledge. After extracting lipids, permeability increased to a median value of 8.6x10(-16) m2. After further digesting with collagenase, permeability increased to a median value of 1.4x10(-14) m2. We conclude that the presence of both lipids and collagen matrix within the porous compartment of cortical bone restricts its radial permeability. These novel findings suggest that the chemical composition of the tissue matrix within the porous compartment of cortical bone influences the transport and exchange of nutrients and waste products, and possibly influences the metabolic functions of osteocytes and osteoblasts.

  5. Assessment of simulated and functional disuse on cortical bone by nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Ni, Qingwen; De Los Santos, Armando; Lam, Hoyan; Qin, Yi-Xian

    A nuclear magnetic resonance (NMR) spin ( T2) relaxation technique has been described for determining water distribution changes on turkey cortical bone tissue of simulated weightlessness (disuse) in vitro. The advantages of using NMR T2 relaxation techniques for bone water distribution are illustrated. The Carr-Purcell-Meiboom-Gill (CPMG) T2 relaxation data can be used to determine the porosity of bone, and can be inverted to T2 relaxation distribution, and this distribution then can be transformed to a pore size distribution with the longer relaxation times corresponding to larger pores. The free induction delay (FID) T2 relaxation data can be inverted to T2 relaxation distribution and this distribution then can be transformed to bound and mobile water distribution with the longest relaxation time corresponding to mobile water and the middle relaxation time corresponding to bound water. The technique is applied to quantify apparent changes in porosity, bound and mobile water in normal and disuse cortical bone. Overall bone porosity is determined using the calibrated NMR fluid volume from the proton relaxation data divided by overall bone volume. The NMR bound and mobile water changes were determined from cortical bone specimens obtained from normal and disuse turkey bones. Differences in porosity and water distribution were found between specimens from normal and disuse. Our results show that the ratio of the average bound to mobile water in bone from normal turkey is higher than in bone from disuse turkey, and the porosity is lower in normal than in disuse turkey. We also show that the average bone porosity multiplied by the ratio of bound to mobile water may be constant for both normal and disuse bone groups. Currently, the influence of water removal on the strength and toughness of cortical bone has been studied by some researchers. Therefore, the porosity, bound and mobile water distribution changes could provide further information directly related to bone

  6. Hierarchical analysis and multi-scale modelling of rat cortical and trabecular bone

    PubMed Central

    Oftadeh, Ramin; Entezari, Vahid; Spörri, Guy; Villa-Camacho, Juan C.; Krigbaum, Henry; Strawich, Elsa; Graham, Lila; Rey, Christian; Chiu, Hank; Müller, Ralph; Hashemi, Hamid Nayeb; Vaziri, Ashkan; Nazarian, Ara

    2015-01-01

    The aim of this study was to explore the hierarchical arrangement of structural properties in cortical and trabecular bone and to determine a mathematical model that accurately predicts the tissue's mechanical properties as a function of these indices. By using a variety of analytical techniques, we were able to characterize the structural and compositional properties of cortical and trabecular bones, as well as to determine the suitable mathematical model to predict the tissue's mechanical properties using a continuum micromechanics approach. Our hierarchical analysis demonstrated that the differences between cortical and trabecular bone reside mainly at the micro- and ultrastructural levels. By gaining a better appreciation of the similarities and differences between the two bone types, we would be able to provide a better assessment and understanding of their individual roles, as well as their contribution to bone health overall. PMID:25808343

  7. Effects of age and loading rate on equine cortical bone failure.

    PubMed

    Kulin, Robb M; Jiang, Fengchun; Vecchio, Kenneth S

    2011-01-01

    Although clinical bone fractures occur predominantly under impact loading (as occurs during sporting accidents, falls, high-speed impacts or other catastrophic events), experimentally validated studies on the dynamic fracture behavior of bone, at the loading rates associated with such events, remain limited. In this study, a series of tests were performed on femoral specimens obtained post-mortem from equine donors ranging in age from 6 months to 28 years. Fracture toughness and compressive tests were performed under both quasi-static and dynamic loading conditions in order to determine the effects of loading rate and age on the mechanical behavior of the cortical bone. Fracture toughness experiments were performed using a four-point bending geometry on single and double-notch specimens in order to measure fracture toughness, as well as observe differences in crack initiation between dynamic and quasi-static experiments. Compressive properties were measured on bone loaded parallel and transverse to the osteonal growth direction. Fracture propagation was then analyzed using scanning electron and scanning confocal microscopy to observe the effects of microstructural toughening mechanisms at different strain rates. Specimens from each horse were also analyzed for dry, wet and mineral densities, as well as weight percent mineral, in order to investigate possible influences of composition on mechanical behavior. Results indicate that bone has a higher compressive strength, but lower fracture toughness when tested dynamically as compared to quasi-static experiments. Fracture toughness also tends to decrease with age when measured quasi-statically, but shows little change with age under dynamic loading conditions, where brittle "cleavage-like" fracture behavior dominates.

  8. The influence of water removal on the strength and toughness of cortical bone

    PubMed Central

    Nyman, Jeffry S.; Roy, Anuradha; Shen, Xinmei; Acuna, Rae L.; Tyler, Jerrod H.; Wang, Xiaodu

    2007-01-01

    Although the effects of dehydration on the mechanical behavior of cortical bone are known, the underlying mechanisms for such effects are not clear. We hypothesize that the interactions of water with the collagen and mineral phases each have a unique influence on mechanical behavior. To study this, strength, toughness, and stiffness were measured with three-point bend specimens made from the mid-diaphysis of human cadaveric femurs and divided into six test groups: control (hydrated), drying in a vacuum oven at room temperature (21 °C) for 30 min and at 21, 50, 70, or 110 °C for 4 h. The experimental data indicated that water loss significantly increased with each increase in drying condition. Bone strength increased with a 5% loss of water by weight, which was caused by drying at 21 °C for 4 h. With water loss exceeding 9%, caused by higher drying temperatures (≥70 °C), strength actually decreased. Drying at 21 °C (irrespective of time in vacuum) significantly decreased bone toughness through a loss of plasticity. However, drying at 70 °C and above caused toughness to decrease through decreases in strength and fracture strain. Stiffness linearly increased with an increase in water loss. From an energy perspective, the water–mineral interaction is removed at higher temperatures than the water–collagen interaction. Therefore, we speculate that loss of water in the collagen phase decreases the toughness of bone, whereas loss of water associated with the mineral phase decreases both bone strength and toughness. PMID:16488231

  9. Changes in the stiffness, strength, and toughness of human cortical bone with age.

    PubMed

    Zioupos, P; Currey, J D

    1998-01-01

    Aging adversely affects the elastic and ultimate properties of human cortical bone as seen in uniaxial tests in quasi static loading, high strain rate impact or fatigue. Little is known about the full effects of aging on toughness and its relationship with strength. In the present article the elastic modulus (E), strength (sigma f), fracture toughness (KC and J-integral), and work of fracture (Wf) were determined in specimens of male human femoral bone aged between 35-92 years. In this way we investigated whether fracture of bone in three situations, allowing various amounts of damage prior to fracture, can provide a better insight into the fracture process and also the relative importance of these experimental methods for assessing the soundness of bone material. We found a steady and significant decrease with age for all these mechanical measures. E fell by 2.3%, from its value of 15.2 GPa at 35 years of age, per decade of later life; sigma f fell similarly from 170 MPa by 3.7%; KC from 6.4 MPa m1/2 by 4.1%; J-integral from 1.2 kJ m-2 by 3%, and the Wf from 3.4 kJ m-2 by 8.7%. In aging bone there was a deterioration in the elastic properties of the material. This reduced the (elastically calculated) critical stress intensity level (KC) required to initiate a macrocrack, or the nonlinear energy associated with the onset of fracture (J). The macrocrack was preceded by less damage, and once created needed less energy to drive through the tissue (Wf).

  10. Factors affecting stresses in cortical bone around miniscrew implants: a three-dimensional finite element study.

    PubMed

    Duaibis, Ramzi; Kusnoto, Budi; Natarajan, Raghu; Zhao, Linping; Evans, Carla

    2012-09-01

    To evaluate various types of stress in cortical bone around miniscrew implants using finite element analysis. Twenty-six three-dimensional assemblies of miniscrew models placed in alveolar bone blocks were constructed using Abaqus (Dassault Systèmes Simulia Corp, Providence, RI), a commercial finite element analysis software package. The model variables included implant design factors and bone-related factors. All miniscrew implants were loaded in the mesial direction with a linear force equal to 2 N. Peak von Mises and principal stress values in cortical bone were compared between the different models for each factor. The results demonstrated that some factors affected the stresses in bone (implant diameter, implant head length, thread size, and elastic modulus of cancellous bone), while other factors did not (thread shape, thread pitch, and cortical bone thickness). Miniscrew implant diameter, head length, and thread size as well as the elastic modulus of cancellous bone affect the stresses in cortical bone layer surrounding the miniscrew implant and may therefore affect its stability.

  11. Effects of vitamin K2 on cortical and cancellous bone mass, cortical osteocyte and lacunar system, and porosity in sciatic neurectomized rats.

    PubMed

    Iwamoto, Jun; Matsumoto, Hideo; Takeda, Tsuyoshi; Sato, Yoshihiro; Yeh, James K

    2010-09-01

    The purpose of the present study was to examine the effects of vitamin K2 on cortical and cancellous bone mass, cortical osteocyte and lacunar system, and porosity in sciatic neurectomized rats. Thirty-four female Sprague-Dawley retired breeder rats were randomized into three groups: age-matched control, sciatic neurectomy (NX), and NX + vitamin K2 administration (menatetrenone, 30 mg/kg/day p.o., three times a week). At the end of the 8-week experiment, bone histomorphometric analysis was performed on cortical and cancellous bone of the tibial diaphysis and proximal metaphysis, respectively, and osteocyte lacunar system and porosity were evaluated on cortical bone of the tibial diaphysis. NX decreased cortical and cancellous bone mass compared with age-matched controls as a result of increased endocortical and trabecular bone erosion and decreased trabecular mineral apposition rate (MAR). Vitamin K2 ameliorated the NX-induced increase in bone erosion, prevented the NX-induced decrease in MAR, and increased bone formation rate (BFR/bone surface) in cancellous bone, resulting in an attenuation of NX-induced cancellous bone loss. However, vitamin K2 did not significantly influence cortical bone mass. NX also decreased osteocyte density and lacunar occupancy and increased porosity in cortical bone compared with age-matched controls. Vitamin K2 ameliorated the NX-induced decrease in lacunar occupancy by viable osteocytes and the NX-induced increase in porosity. The present study showed the efficacy of vitamin K2 for cancellous bone mass and cortical lacunar occupancy by viable osteocytes and porosity in sciatic NX rats.

  12. Assessing temperature changes in cortical bone using variable flip-angle ultrashort echo-time MRI

    NASA Astrophysics Data System (ADS)

    Han, Misung; Scott, Serena J.; Ozhinsky, Eugene; Salgaonakar, Vasant A.; Jones, Peter D.; Larson, Peder E. Z.; Diederich, Chris J.; Rieke, Viola; Krug, Roland

    2017-03-01

    MR-guided high-intensity focused ultrasound ablation is a promising, noninvasive method for treatment of bone tumors and palliation of pain. During thermal therapy, temperature mapping is necessary to ensure proper heat deposition in targeted tumors as well as to prevent unnecessary heating in surrounding tissues. Conventional MR thermometry exploits the proton resonant frequency shift of water protons, which normally requires a long echo time; therefore, this method is not appropriate for cortical bone due to its short T2* relaxation time. This work demonstrates that ultrashort echo-time MRI can characterize T1 changes in cortical bone caused by temperature changes. Ex vivo experiments were performed to heat diaphysis segments of bovine femurs with an interstitial ultrasound applicator. The T1 increase in the heated parts of cortical bone was observed. The temerature dependence of T1 in cortical born was also assessed by heating bovine bone samples in a temperature-controlled water bath. T1 mapping of cortical bone enabled by ultrashort echo-time MRI might allow for more accurate characterization of thermal dose during treatment of bone tumors.

  13. Ovariectomy-induced changes in aged beagles : histomorphometry of rib cortical bone.

    SciTech Connect

    Wilson, A. K.; Bhattacharyya, M. H.; Miller, S.; Sacco-Gibson, N.; Center for Mechanistic Biology and Biotechnology; Univ. of Utah; Procter & Gamble Pharmaceuticals

    1998-03-01

    Bone loss associated with estrogen depletion is well documented in cancellous bone but less well characterized in cortical bone. The effects of ovariectomy on the aged beagle skeleton were studied by histomorphometric analysis of the cortical bone in sequential rib biopsies. Biopsies were taken from each ovariectomized or sham-operated dog at the time of surgery and at 1, 4, and 8.5 months after surgery. Just prior to each postoperative biopsy, tetracycline, calcein, and xylenol orange, respectively, were administered by a fluorochrome labeling procedure (2d-10d-2d) to provide markers of bone formation. Analysis of sequential rib biopsies provided a means to follow the ovariectomy response over time and to compare each animal against its own baseline. Though ovariectomy did not influence histomorphometric indices at 1 month after surgery, a transient increase in cortical bone formation occurred thereafter, with a sixfold increase over that of sham-operated dogs at 4 months (P < 0.001) and a return to near control levels at 8.5 months. Cortical porosity increased by the fourth month after ovariectomy and remained high at 8.5 months. These data demonstrate for the first time that rib cortical bone is a responsive site for the effects of ovariectomy in aged female dogs.

  14. Predicting cortical bone adaptation to axial loading in the mouse tibia

    PubMed Central

    Pereira, A. F.; Javaheri, B.; Pitsillides, A. A.; Shefelbine, S. J.

    2015-01-01

    The development of predictive mathematical models can contribute to a deeper understanding of the specific stages of bone mechanobiology and the process by which bone adapts to mechanical forces. The objective of this work was to predict, with spatial accuracy, cortical bone adaptation to mechanical load, in order to better understand the mechanical cues that might be driving adaptation. The axial tibial loading model was used to trigger cortical bone adaptation in C57BL/6 mice and provide relevant biological and biomechanical information. A method for mapping cortical thickness in the mouse tibia diaphysis was developed, allowing for a thorough spatial description of where bone adaptation occurs. Poroelastic finite-element (FE) models were used to determine the structural response of the tibia upon axial loading and interstitial fluid velocity as the mechanical stimulus. FE models were coupled with mechanobiological governing equations, which accounted for non-static loads and assumed that bone responds instantly to local mechanical cues in an on–off manner. The presented formulation was able to simulate the areas of adaptation and accurately reproduce the distributions of cortical thickening observed in the experimental data with a statistically significant positive correlation (Kendall's τ rank coefficient τ = 0.51, p < 0.001). This work demonstrates that computational models can spatially predict cortical bone mechanoadaptation to a time variant stimulus. Such models could be used in the design of more efficient loading protocols and drug therapies that target the relevant physiological mechanisms. PMID:26311315

  15. Increased intra-cortical porosity reduces bone stiffness and strength in pediatric patients with osteogenesis imperfecta.

    PubMed

    Vardakastani, V; Saletti, D; Skalli, W; Marry, P; Allain, J M; Adam, C

    2014-12-01

    Osteogenesis imperfecta (OI) is a heritable disease occurring in one out of every 20,000 births. Although it is known that Type I collagen mutation in OI leads to increased bone fragility, the mechanism of this increased susceptibility to fracture is not clear. The aim of this study was to assess the microstructure of cortical bone fragments from patients with osteogenesis imperfecta (OI) using polarized light microscopy, and to correlate microstructural observations with the results of previously performed mechanical compression tests on bone from the same source. Specimens of cortical bone were harvested from the lower limbs of three (3) OI patients at the time of surgery, and were divided into two groups. Group 1 had been subjected to previous micro-mechanical compression testing, while Group 2 had not been subjected to any prior testing. Polarized light microscopy revealed disorganized bone collagen architecture as has been previously observed, as well as a large increase in the areal porosity of the bone compared to typical values for healthy cortical bone, with large (several hundred micron sized), asymmetrical pores. Importantly, the areal porosity of the OI bone samples in Group 1 appears to correlate strongly with their previously measured apparent Young's modulus and compressive strength. Taken together with prior nanoindentation studies on OI bone tissue, the results of this study suggest that increased intra-cortical porosity is responsible for the reduction in macroscopic mechanical properties of OI cortical bone, and therefore that in vivo imaging modalities with resolutions of ~100 μm or less could potentially be used to non-invasively assess bone strength in OI patients. Although the number of subjects in this study is small, these results highlight the importance of further studies in OI bone by groups with access to human OI tissue in order to clarify the relationship between increased porosity and reduced macroscopic mechanical integrity

  16. Propagation of time-reversed Lamb waves in bovine cortical bone in vitro.

    PubMed

    Lee, Kang Il; Yoon, Suk Wang

    2015-01-01

    The present study aims to investigate the propagation of time-reversed Lamb waves in bovine cortical bone in vitro. The time-reversed Lamb waves were successfully launched at 200 kHz in 18 bovine tibiae through a time reversal process of Lamb waves. The group velocities of the time-reversed Lamb waves in the bovine tibiae were measured using the axial transmission technique. They showed a significant correlation with the cortical thickness and tended to follow the theoretical group velocity of the lowest order antisymmetrical Lamb wave fairly well, consistent with the behavior of the slow guided wave in long cortical bones.

  17. Correlation between ultrasound velocity and densitometry in fresh and demineralized cortical bone

    PubMed Central

    de Mesquita, Alessandro Queiroz; Barbieri, Giuliano; Barbieri, Claudio Henrique

    2016-01-01

    OBJECTIVE: To compare ultrasound propagation velocity with densitometry in the diaphyseal compact cortical bone of whole sheep metatarsals. METHODS: The transverse ultrasound velocity and bone mineral density of 5-cm-long diaphyseal bone segments were first measured. The bone segments were then divided into four groups of 15 segments each and demineralized in an aqueous 0.5 N hydrochloric acid solution for 6, 12, 24 or 36 hours. All measurements were repeated after demineralization for each time duration and the values measured before and after demineralization were compared. RESULTS: Ultrasound velocity and bone mineral density decreased with demineralization time, and most differences in the pre- and post-demineralization values within each group and between groups were significant: A moderate correlation coefficient (r=0.75956) together with a moderate agreement was determined between both post-demineralization parameters, detected by the Bland-Altman method. CONCLUSION: We conclude that both ultrasound velocity and bone mineral density decrease as a result of demineralization, thus indicating that bone mineral content is of great importance for maintaining the acoustic parameters of cortical bone, as observed for cancellous bone. Ultrasound velocity can be used to evaluate both compact cortical bone quality and bone mineral density. PMID:27982167

  18. Correlation between ultrasound velocity and densitometry in fresh and demineralized cortical bone.

    PubMed

    Mesquita, Alessandro Queiroz de; Barbieri, Giuliano; Barbieri, Claudio Henrique

    2016-11-01

    To compare ultrasound propagation velocity with densitometry in the diaphyseal compact cortical bone of whole sheep metatarsals. The transverse ultrasound velocity and bone mineral density of 5-cm-long diaphyseal bone segments were first measured. The bone segments were then divided into four groups of 15 segments each and demineralized in an aqueous 0.5 N hydrochloric acid solution for 6, 12, 24 or 36 hours. All measurements were repeated after demineralization for each time duration and the values measured before and after demineralization were compared. Ultrasound velocity and bone mineral density decreased with demineralization time, and most differences in the pre- and post-demineralization values within each group and between groups were significant: A moderate correlation coefficient (r=0.75956) together with a moderate agreement was determined between both post-demineralization parameters, detected by the Bland-Altman method. We conclude that both ultrasound velocity and bone mineral density decrease as a result of demineralization, thus indicating that bone mineral content is of great importance for maintaining the acoustic parameters of cortical bone, as observed for cancellous bone. Ultrasound velocity can be used to evaluate both compact cortical bone quality and bone mineral density.

  19. A grape-enriched diet increases bone calcium retention and cortical bone properties in ovariectomized rats.

    PubMed

    Hohman, Emily E; Weaver, Connie M

    2015-02-01

    Grapes and their associated phytochemicals have been investigated for beneficial effects on cardiovascular health, cancer prevention, and other chronic diseases, but the effect of grape consumption on bone health has not been fully determined. We previously found short-term benefits of grape products on reducing bone turnover in ovariectomized rats. The objective of this study was to determine the long-term benefits of a grape-enriched diet on bone in ovariectomized rats. Rats were ovariectomized at 3 mo of age and were administered a single dose of (45)Ca to prelabel bones at 4 mo of age. After a 1-mo equilibration period, baseline urinary (45)Ca excretion was determined. Rats (n = 22/group) were then randomly assigned to a modified AIN93M diet containing 25% freeze-dried grape powder or to a control diet for 8 wk. Urinary (45)Ca excretion was monitored throughout the study to determine changes in bone (45)Ca retention. Calcium balance was assessed after 1 and 8 wk of consuming the experimental diets, and a calcium kinetic study was performed at 8 wk. After 8 wk, femurs were collected for micro-computed tomographic imaging, 3-point bending, and reference point indentation. Rats fed the grape-enriched diet had 44% greater net bone calcium retention than did rats fed the control diet. There were no differences in calcium balance due to diet at either week 1 or week 8, but there was a significant increase in net calcium absorption (10.6%) and retention (5.7%) from week 1 to week 8 in the grape-enriched diet group only. Grape-enriched diet-fed rats had 3% greater cortical thickness and 11% greater breaking strength. There were no differences in femur bone mineral density, trabecular microarchitecture, or reference point indentation variables due to diet. This study of ovariectomized rats indicates that the consumption of grape products may improve calcium utilization and suppress bone turnover, resulting in improvements in bone quality. © 2015 American Society for

  20. Molecular Genetic Studies of Bone Mechanical Strain and of Pedigrees with Very High Bone Density

    DTIC Science & Technology

    2007-11-01

    30-46 Col8a1 EphA3 Pit1 Increased in bone in response to mechanical loading. Involved in tooth development. Mediates bone formation by...osteoclast resorption . KO mice show increased bone density and cortical thickness. Involved in MEKK3 signaling and apoptosis. Important in...osteoclastogenesis. Involved in tooth development. Involved in angiogenesis of bone. Involved in skeletal development. 18 15-40 Lox Pdgfrb Adrb2 Mc4r

  1. Midline lumbar fusion using cortical bone trajectory screws. Preliminary report

    PubMed Central

    Bielecki, Mateusz; Prokopienko, Marek; Nowak, Arkadiusz; Czernicki, Tomasz; Marchel, Andrzej

    2016-01-01

    Introduction Midline lumbar fusion (MIDLF) using cortical bone trajectory is an alternative method of transpedicular spinal fusion for degenerative disease. The new entry points’ location and screwdriving direction allow the approach-related morbidity to be reduced. Aim To present our preliminary experience with the MIDLF technique on the first 5 patients with lumbar degenerative disease and with follow-up of at least 6 months. Material and methods Retrospective analysis was performed on the first 5 patients with foraminal (4) or central (1) stenosis operated on between December 2014 and February 2015. Three patients were fused at L4–L5 and two at the L5–S1 level. Results No intra- or post-operative complications occurred with this approach. An improvement regarding the leading symptom in the early postoperative period (sciatica 4/4, claudication 1/1) was achieved in all patients. The mean improvements in the visual analogue scale for low back and leg pain were 2.2 and 4.8 respectively. The mean Oswestry Disability Index scores were 52% (range: 16–82%) before surgery and 33% (range: 12–56%) at 3-month follow-up (mean improvement 19%). At the most recent follow-up, 4 patients reported the maintenance of the satisfactory result. The early standing and follow-up X-rays showed satisfactory screw placement in all patients. Conclusions In our initial experience, the MIDLF technique seems to be an encouraging alternative to traditional transpedicular trajectory screws when short level lumbar fusion is needed. Nevertheless, longer observations on larger groups of patients are needed to reliably evaluate the safety of the method and the sustainability of the results. PMID:27829938

  2. Greater association of peak neuromuscular performance with cortical bone geometry, bone mass and bone strength than bone density: A study in 417 older women.

    PubMed

    Belavý, Daniel L; Armbrecht, Gabriele; Blenk, Tilo; Bock, Oliver; Börst, Hendrikje; Kocakaya, Emine; Luhn, Franziska; Rantalainen, Timo; Rawer, Rainer; Tomasius, Frederike; Willnecker, Johannes; Felsenberg, Dieter

    2016-02-01

    We evaluated which aspects of neuromuscular performance are associated with bone mass, density, strength and geometry. 417 women aged 60-94years were examined. Countermovement jump, sit-to-stand test, grip strength, forearm and calf muscle cross-sectional area, areal bone mineral content and density (aBMC and aBMD) at the hip and lumbar spine via dual X-ray absorptiometry, and measures of volumetric vBMC and vBMD, bone geometry and section modulus at 4% and 66% of radius length and 4%, 38% and 66% of tibia length via peripheral quantitative computed tomography were performed. The first principal component of the neuromuscular variables was calculated to generate a summary neuromuscular variable. Percentage of total variance in bone parameters explained by the neuromuscular parameters was calculated. Step-wise regression was also performed. At all pQCT bone sites (radius, ulna, tibia, fibula), a greater percentage of total variance in measures of bone mass, cortical geometry and/or bone strength was explained by peak neuromuscular performance than for vBMD. Sit-to-stand performance did not relate strongly to bone parameters. No obvious differential in the explanatory power of neuromuscular performance was seen for DXA aBMC versus aBMD. In step-wise regression, bone mass, cortical morphology, and/or strength remained significant in relation to the first principal component of the neuromuscular variables. In no case was vBMD positively related to neuromuscular performance in the final step-wise regression models. Peak neuromuscular performance has a stronger relationship with leg and forearm bone mass and cortical geometry as well as proximal forearm section modulus than with vBMD. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. High-acceleration whole body vibration stimulates cortical bone accrual and increases bone mineral content in growing mice.

    PubMed

    Gnyubkin, Vasily; Guignandon, Alain; Laroche, Norbert; Vanden-Bossche, Arnaud; Malaval, Luc; Vico, Laurence

    2016-06-14

    Whole body vibration (WBV) is a promising tool for counteracting bone loss. Most WBV studies on animals have been performed at acceleration <1g and frequency between 30 and 90Hz. Such WBV conditions trigger bone growth in osteopenia models, but not in healthy animals. In order to test the ability of WBV to promote osteogenesis in young animals, we exposed seven-week-old male mice to vibration at 90Hz and 2g peak acceleration for 15min/day, 5 days/week. We examined the effects on skeletal tissues with micro-computed tomography and histology. We also quantified bone vascularization and mechanosensitive osteocyte proteins, sclerostin and DMP1. Three weeks of WBV resulted in an increase of femur cortical thickness (+5%) and area (+6%), associated with a 25% decrease of sclerostin expression, and 35% increase of DMP1 expression in cortical osteocytes. Mass-structural parameters of trabecular bone were unaltered in femur or vertebra, while osteoclastic parameters and bone formation rate were increased at both sites. Three weeks of WBV resulted in higher blood vessel numbers (+23%) in the distal femoral metaphysis. After 9-week WBV, we have not observed the difference in structural cortical or trabecular parameters. However, the tissue mineral density of cortical bone was increased by 2.5%. Three or nine weeks of 2g/90Hz WBV treatment did not affect longitudinal growth rate or body weight increase under our experimental conditions, indicating that these are safe to use. These results validate a potential of 2g/90Hz WBV to stimulate trabecular bone cellular activity, accelerate cortical bone growth, and increase bone mineral density. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Connexin 43 deficiency attenuates loss of trabecular bone and prevents suppression of cortical bone formation during unloading.

    PubMed

    Lloyd, Shane A; Lewis, Gregory S; Zhang, Yue; Paul, Emmanuel M; Donahue, Henry J

    2012-11-01

    Connexin 43 (Cx43) is the most abundant gap junction protein in bone and has been demonstrated as an integral component of skeletal homeostasis. In the present study, we sought to further refine the role of Cx43 in the response to mechanical unloading by subjecting skeletally mature mice with a bone-specific deletion of Cx43 (cKO) to 3 weeks of mechanical unloading via hindlimb suspension (HLS). The HLS model was selected to recapitulate the effects of skeletal unloading due to prolonged bed rest, reduced activity associated with aging, and spaceflight microgravity. At baseline, the cortical bone of cKO mice displayed an osteopenic phenotype, with expanded cortices, decreased cortical thickness, decreased bone mineral density, and increased porosity. There was no baseline trabecular phenotype. After 3 weeks of HLS, wild-type (WT) mice experienced a substantial decline in trabecular bone volume fraction, connectivity density, trabecular thickness, and trabecular tissue mineral density. These deleterious effects were attenuated in cKO mice. Conversely, there was a similar and significant amount of cortical bone loss in both WT and cKO. Interestingly, mechanical testing revealed a greater loss of strength and rigidity for cKO during HLS. Analysis of double-label quantitative histomorphometry data demonstrated a substantial decrease in bone formation rate, mineralizing surface, and mineral apposition rate at both the periosteal and endocortical surfaces of the femur after unloading of WT mice. This suppression of bone formation was not observed in cKO mice, in which parameters were maintained at baseline levels. Taken together, the results of the present study indicate that Cx43 deficiency desensitizes bone to the effects of mechanical unloading, and that this may be due to an inability of mechanosensing osteocytes to effectively communicate the unloading state to osteoblasts to suppress bone formation. Cx43 may represent a novel therapeutic target for investigation as

  5. Racial differences in cortical bone and their relationship to biochemical variables in Black and White children in the early stages of puberty.

    PubMed

    Warden, S J; Hill, K M; Ferira, A J; Laing, E M; Martin, B R; Hausman, D B; Weaver, C M; Peacock, M; Lewis, R D

    2013-06-01

    Osteoporotic fracture rates differ according to race with Blacks having up to half the rate of Whites. The current study demonstrates that racial divergence in cortical bone properties develops in early childhood despite lower serum 25-hydroxyvitamin D in Blacks. Racial differences in bone structure likely have roots in childhood as bone size develops predominantly during growth. This study aimed to compare cortical bone health within the tibial diaphysis of Black and White children in the early stages of puberty and explore the contributions of biochemical variables in explaining racial variation in cortical bone properties. A cross-sectional study was performed comparing peripheral quantitative computed tomography-derived cortical bone measures of the tibial diaphysis and biochemical variables in 314 participants (n = 155 males; n = 164 Blacks) in the early stages of puberty. Blacks had greater cortical volumetric bone mineral density, mass, and size compared to Whites (all p < 0.01), contributing to Blacks having 17.0 % greater tibial strength (polar strength-strain index (SSIP)) (p < 0.001). Turnover markers indicated that Blacks had higher bone formation (osteocalcin (OC) and bone-specific alkaline phosphatase) and lower bone resorption (N-terminal telopeptide) than Whites (all p < 0.01). Blacks also had lower 25-hydroxyvitamin D (25(OH)D) and higher 1,25-dihydroxyvitamin D (1,25(OH)2D) and parathyroid hormone (PTH) (all p < 0.05). There were no correlations between tibial bone properties and 25(OH)D and PTH in Whites (all p ≥ 0.10); however, SSIP was negatively and positively correlated with 25(OH)D and PTH in Blacks, respectively (all p ≤ 0.02). Variation in bone cross-sectional area and SSIP attributable to race was partially explained by tibial length, 25(OH)D/PTH, and OC. Divergence in tibial cortical bone properties between Blacks and Whites is established by the early stages of puberty with the enhanced cortical bone

  6. Trabecular bone of growth plate origin influences both trabecular and cortical morphology in adulthood.

    PubMed

    Wang, Qingju; Ghasem-Zadeh, Ali; Wang, Xiao-Fang; Iuliano-Burns, Sandra; Seeman, Ego

    2011-07-01

    Skeletal fragility is common at metaphyseal regions of long bones. The cortices of this region are derived by coalescence of trabeculae around the periphery of the growth plate, not by periosteal apposition, as occurs in the diaphyses. We therefore hypothesized that trabecular bone in childhood predicted both cortical and trabecular morphology in adulthood. To test this hypothesis, we measured distal radial and tibial structure using high-resolution peripheral quantitative computed tomography in 61 daughter-mother pairs, mean age 12.5 years (range 7 to 19 years) and 44.1 years (range 32 to 50 years), respectively. The daughters' trabecular bone volume (BV/TV), thickness, number, and separation predicted the corresponding traits in their mothers. Their trabecular BV/TV also predicted their mothers' cortical thickness (r = 0.32, p = .02). By contrast, the daughters' cortical thickness did not predict their mothers' cortical thickness. The daughters had higher trabecular BV/TV than their mothers (mean ± SD, radius 0.134 ± 0.024 versus 0.124 ± 0.033, p = .03; tibia 0.145 ± 0.021 versus 0.135 ± 0.032, p < .01) owing to greater trabecular number, not thickness, and less trabecular separation. Abnormalities in the development of metaphyseal trabecular bone are likely to influence fragility in both trabecular and cortical bone of this region in adulthood.

  7. AN INVESTIGATION OF THE MINERAL IN DUCTILE AND BRITTLE CORTICAL MOUSE BONE

    PubMed Central

    Rodriguez-Florez, Naiara; Garcia-Tunon, Esther; Mukadam, Quresh; Saiz, Eduardo; Oldknow, Karla J.; Farquharson, Colin; Millán, José Luis; Boyde, Alan; Shefelbine, Sandra J.

    2015-01-01

    Bone is a strong and tough material composed of apatite mineral, organic matter and water. Changes in composition and organization of these building blocks affect bone’s mechanical integrity. Skeletal disorders often affect bone’s mineral phase, either by variations in the collagen or directly altering mineralization. The aim of the current study was to explore the differences in the mineral of brittle and ductile cortical bone at the mineral (nm) and tissue (µm) levels using two mouse phenotypes. Osteogenesis imperfecta murine (oim−/−) mice were used to model brittle bone; PHOSPHO1 mutants (Phospho1−/−) had ductile bone. They were compared to their respective wild-type controls. Femora were defatted and ground to powder to measure average mineral crystal size using X-ray diffraction (XRD), and to monitor the bulk mineral to matrix ratio via thermogravimetric analysis (TGA). XRD scans were run after TGA for phase identification, to assess the fractions of hydroxyapatite and β-tricalcium phosphate. Tibiae were embedded to measure elastic properties with nanoindentation and the extent of mineralization with backscattered electron microscopy (qbSEM). Interestingly, the mineral of brittle oim−/− and ductile Phospho1−/− bones had many similar characteristics. Both pathology models had smaller apatite crystals, lower mineral to matrix ratio, and showed more thermal conversion to β-tricalcium phosphate than their wild-types, indicating deviations from stoichiometric hydroxyapatite in the original mineral. The degree of mineralization of the bone matrix was different for each strain: oim−/− were hypermineralized, while Phospho1−/− were hypomineralized. However, alterations in the mineral were associated with reduced tissue elastic moduli in both pathologies. Results revealed that despite having extremely different whole bone mechanics, the mineral of oim−/− and Phospho1−/− has several similar trends at smaller length scales. This

  8. Skeletal effects of constant and terminated use of risedronate on cortical bone in ovariectomized rats.

    PubMed

    Li, Q N; Liang, N C; Huang, L F; Wu, T; Hu, B; Mo, L E

    1999-01-01

    To study the skeletal effects of continual and terminated use of risedronate treatment on cortical bone in ovariectomized (Ovx) rats, we used risedronate (Ris), 5 microg x kg(-1), by subcutaneous injections, twice per week. The middle part of the tibial shafts (Tx) were processed undecalcified for quantitive bone histomorphometry. Cortical bone and the marrow areas of the tibial shaft did not change in either sham-Ovx or Ovx rats during the 150-day experimental period. Continued administration of Ris for 150 days decreased the marrow area and increased the percentage of cortical area compared with the matching sham and Ovx group. A decrease in bone formation indices in both periosteal and endocortical surfaces of Tx in sham-operated rats between the age of 5 and 8 months was seen. Ovariectomy increased the percentage of labeled perimeter in the periosteal area, and markedly increased the percentage of eroded perimeter in the endocortical surface compared with sham control groups in 81 and 150 days. Bone formation indices of Ris treatment were increased in periosteal surfaces, and percentages of eroded perimeter were decreased more in endocortical surfaces in 150 days than in the matching sham and Ovx groups. These data matched our static data, which showed a significantly increased percentage of cortical bone area and decreased percentage of marrow area. These bone gains were not maintained in the 90-day Ris withdrawal group. For cancellous bone, the 60-day Ris-treated high bone mass was maintained in the withdrawal group and not maintained in Ris continmuously treated group. These results indicate the effects of constant and terminated use of Ris in cortical bone were different from those in trabecular bone in the proximal tibial metaphysis.

  9. Reduced Bone Cortical Thickness in Boys with Autism or Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Hediger, Mary L.; England, Lucinda J.; Molloy, Cynthia A.; Yu, Kai F.; Manning-Courtney, Patricia; Mills, James L.

    2008-01-01

    Bone development, casein-free diet use, supplements, and medications were assessed for 75 boys with autism or autism spectrum disorder, ages 4-8 years. Second metacarpal bone cortical thickness (BCT), measured on hand-wrist radiographs, and % deviations in BCT from reference medians were derived. BCT increased with age, but % deviations evidenced…

  10. Reduced Bone Cortical Thickness in Boys with Autism or Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Hediger, Mary L.; England, Lucinda J.; Molloy, Cynthia A.; Yu, Kai F.; Manning-Courtney, Patricia; Mills, James L.

    2008-01-01

    Bone development, casein-free diet use, supplements, and medications were assessed for 75 boys with autism or autism spectrum disorder, ages 4-8 years. Second metacarpal bone cortical thickness (BCT), measured on hand-wrist radiographs, and % deviations in BCT from reference medians were derived. BCT increased with age, but % deviations evidenced…

  11. Penetration of cutting tool into cortical bone: experimental and numerical investigation of anisotropic mechanical behaviour.

    PubMed

    Li, Simin; Abdel-Wahab, Adel; Demirci, Emrah; Silberschmidt, Vadim V

    2014-03-21

    An anisotropic mechanical behaviour of cortical bone and its intrinsic hierarchical microstructure act as protective mechanisms to prevent catastrophic failure due to natural loading conditions; however, they increase the extent of complexity of a penetration process in the case of orthopaedic surgery. Experimental results available in literature provide only limited information about processes in the vicinity of a tool-bone interaction zone. Also, available numerical models the bone-cutting process do not account for material anisotropy or the effect of damage mechanisms. In this study, both experimental and numerical studies were conducted to address these issues and to elucidate the effect of anisotropic mechanical behaviour of cortical bone tissue on penetration of a sharp cutting tool. First, a set of tool-penetration experiments was performed in directions parallel and perpendicular to bone axis. Also, these experiments included bone samples cut from four different cortices to evaluate the effect of spatial variability and material anisotropy on the penetration processes. Distinct deformation and damage mechanisms linked to different microstructure orientations were captured using a micro-lens high-speed camera. Then, a novel hybrid FE model employing a smoothed-particle-hydrodynamic domain embedded into a continuum FE one was developed based on the experimental configuration to characterise the anisotropic deformation and damage behaviour of cortical bone under a penetration process. The results of our study revealed a clear anisotropic material behaviour of the studied cortical bone tissue and the influence of the underlying microstructure. The proposed FE model reflected adequately the experimental results and demonstrated the need for the use of the anisotropic and damage material model to analyse cutting of the cortical-bone tissue. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Automated cortical bone segmentation for multirow-detector CT imaging with validation and application to human studies

    PubMed Central

    Li, Cheng; Jin, Dakai; Chen, Cheng; Letuchy, Elena M.; Janz, Kathleen F.; Burns, Trudy L.; Torner, James C; Levy, Steven M.; Saha, Punam K

    2015-01-01

    Purpose: Cortical bone supports and protects human skeletal functions and plays an important role in determining bone strength and fracture risk. Cortical bone segmentation at a peripheral site using multirow-detector CT (MD-CT) imaging is useful for in vivo assessment of bone strength and fracture risk. Major challenges for the task emerge from limited spatial resolution, low signal-to-noise ratio, presence of cortical pores, and structural complexity over the transition between trabecular and cortical bones. An automated algorithm for cortical bone segmentation at the distal tibia from in vivo MD-CT imaging is presented and its performance and application are examined. Methods: The algorithm is completed in two major steps—(1) bone filling, alignment, and region-of-interest computation and (2) segmentation of cortical bone. After the first step, the following sequence of tasks is performed to accomplish cortical bone segmentation—(1) detection of marrow space and possible pores, (2) computation of cortical bone thickness, detection of recession points, and confirmation and filling of true pores, and (3) detection of endosteal boundary and delineation of cortical bone. Effective generalizations of several digital topologic and geometric techniques are introduced and a fully automated algorithm is presented for cortical bone segmentation. Results: An accuracy of 95.1% in terms of volume of agreement with manual outlining of cortical bone was observed in human MD-CT scans, while an accuracy of 88.5% was achieved when compared with manual outlining on postregistered high resolution micro-CT imaging. An intraclass correlation coefficient of 0.98 was obtained in cadaveric repeat scans. A pilot study was conducted to describe gender differences in cortical bone properties. This study involved 51 female and 46 male participants (age: 19–20 yr) from the Iowa Bone Development Study. Results from this pilot study suggest that, on average after adjustment for height

  13. Experimental and numerical investigation of cracking behavior of cortical bone in cutting.

    PubMed

    Alam, K

    2014-01-01

    Bone cutting is a well-known surgical procedure in orthopaedics and dentistry for fracture treatment and reconstruction. Common complications associated with the process are mechanical damage linked with excessive levels of penetration force. Larger forces may produce minor cracks in bone which may seriously affect strength of fixation and may delay the healing process. This paper investigates cracking behavior in the microstructure of cortical bone in cutting using experimental and numerical techniques. Experiments were performed on cortical bone to study the mechanics of crack propagation and evaluate the extent of crack with the drilling force and amount of penetration. Finite element (FE) simulations were performed to visualize the extension and arrest of the cracks in bone microstructure. The length of crack was found to be strongly influenced by the drilling force and amount of drill penetration. Osteon were seen to deflect the cracks at their boundaries. Crack propagation in bone microstructure was observed to depend on anatomical direction. Numerical simulations predicted the direction of crack propagation and found osteon boundaries to act as barrier to the cracks. Lower drilling force may be used in cutting the bone to avoid cracks in the bone tissue. A detailed FE model based on fracture data of cortical bone is to be produced to simulate cracking of bone microstructure.

  14. Bisphosphonates Improve Trabecular Bone Mass and Normalize Cortical Thickness in Ovariectomized, Osteoblast Connexin43 Deficient Mice

    PubMed Central

    Watkins, Marcus P.; Norris, Jin Yi; Grimston, Susan K.; Zhang, Xiaowen; Phipps, Roger J.; Ebetino, Frank H.; Civitelli, Roberto

    2012-01-01

    The gap junction protein, connexin43 (Cx43) controls both bone formation and osteoclastogenesis via osteoblasts and/or osteocytes. Cx43 has also been proposed to mediate an anti-apoptotic effect of bisphosphonates, potent inhibitors of bone resorption. We studied whether bisphosphonates are effective in protecting mice with a conditional Cx43 gene deletion in osteoblasts and osteocytes (cKO) from the consequences of ovariectomy on bone mass and strength. Ovariectomy resulted in rapid loss of trabecular bone followed by a slight recovery in wild type (WT) mice, and a similar degree of trabecular bone loss, albeit slightly delayed, occurred in cKO mice. Treatment with either risedronate (20µg/kg) or alendronate (40µg/kg) prevented ovariectomy-induced bone loss in both genotypes. In basal conditions, bones of cKO mice have larger marrow area, higher endocortical osteoclast number, and lower cortical thickness and strength relative to WT. Ovariectomy increased endocortical osteoclast number in WT but not in cKO mice. Both bisphosphonates prevented these increases in WT mice, and normalized endocortical osteoclast number, cortical thickness and bone strength in cKO mice. Thus, lack of osteoblast/osteocyte Cx43 does not alter bisphosphonate action on bone mass and strength in estrogen deficiency. These results support the notion that one of the main functions of Cx43 in cortical bone is to restrain osteoblast and/or osteocytes from inducing osteoclastogenesis at the endocortical surface. PMID:22750450

  15. Bisphosphonates improve trabecular bone mass and normalize cortical thickness in ovariectomized, osteoblast connexin43 deficient mice.

    PubMed

    Watkins, Marcus P; Norris, Jin Yi; Grimston, Susan K; Zhang, Xiaowen; Phipps, Roger J; Ebetino, Frank H; Civitelli, Roberto

    2012-10-01

    The gap junction protein, connexin43 (Cx43) controls both bone formation and osteoclastogenesis via osteoblasts and/or osteocytes. Cx43 has also been proposed to mediate an anti-apoptotic effect of bisphosphonates, potent inhibitors of bone resorption. We studied whether bisphosphonates are effective in protecting mice with a conditional Cx43 gene deletion in osteoblasts and osteocytes (cKO) from the consequences of ovariectomy on bone mass and strength. Ovariectomy resulted in rapid loss of trabecular bone followed by a slight recovery in wild type (WT) mice, and a similar degree of trabecular bone loss, albeit slightly delayed, occurred in cKO mice. Treatment with either risedronate (20 μg/kg) or alendronate (40 μg/kg) prevented ovariectomy-induced bone loss in both genotypes. In basal conditions, bones of cKO mice have larger marrow area, higher endocortical osteoclast number, and lower cortical thickness and strength relative to WT. Ovariectomy increased endocortical osteoclast number in WT but not in cKO mice. Both bisphosphonates prevented these increases in WT mice, and normalized endocortical osteoclast number, cortical thickness and bone strength in cKO mice. Thus, lack of osteoblast/osteocyte Cx43 does not alter bisphosphonate action on bone mass and strength in estrogen deficiency. These results support the notion that one of the main functions of Cx43 in cortical bone is to restrain osteoblast and/or osteocytes from inducing osteoclastogenesis at the endocortical surface.

  16. Eldecalcitol improves mechanical strength of cortical bones by stimulating the periosteal bone formation in the senescence-accelerated SAM/P6 mice - a comparison with alfacalcidol.

    PubMed

    Shiraishi, Ayako; Sakai, Sadaoki; Saito, Hitoshi; Takahashi, Fumiaki

    2014-10-01

    Eldecalcitol (ELD), a 2β-hydroxypropyloxy derivative of 1α,25(OH)2D3, is a potent inhibitor of bone resorption that has demonstrated a greater effect at reducing the risk of fracture in osteoporotic patients than alfacalcidol (ALF). In the present study, we used the senescence-accelerated mouse strain P6 (SAM/P6), which has low bone mass caused by osteoblast dysfunction, to evaluate the effect of ELD on cortical bone in comparison with ALF. Four-month-old SAM/P6 mice were given either ELD (0.025 or 0.05μg/kg) or ALF (0.2 or 0.4μg/kg) by oral gavage 5 times/week for 6 weeks. Both ELD and ALF increased serum calcium (Ca) in a dose-dependent manner. Serum Ca levels in the ELD 0.05μg/kg group were comparable to those of the ALF 0.2μg/kg group. ELD 0.05μg/kg significantly improved the bone biomechanical properties of the femur compared with the vehicle control group (p<0.001) and the ALF 0.2μg/kg group (p<0.05) evaluated by 3-point bending test. The cortical area of the mid-femur in the ELD 0.05μg/kg group but not the ALF 0.2μg/kg group was significantly higher than those of the vehicle control group (p<0.001). Bone histomorphometry revealed that in the femoral endocortical surface, the suppression of bone resorption parameters (N.Oc/BS) and bone formation parameters (MS/BS) by ELD (0.05μg/kg) was greater than that by ALF (0.2μg/kg). In contrast, in the femoral periosteal surface, ELD 0.05μg/kg significantly increased bone formation parameters (BFR/BS, MS/BS) compared with the vehicle control group (p<0.05, p<0.01, respectively), whereas ALF 0.2μg/kg did not alter these parameters. These results indicate that ELD improved the biomechanical properties of femoral cortical bone not only by inhibiting endocortical bone resorption but also by stimulating the periosteal bone formation in SAM/P6 mice. This article is part of a Special Issue entitled '16th Vitamin D Workshop'. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Temperature Values Variability in Piezoelectric Implant Site Preparation: Differences between Cortical and Corticocancellous Bovine Bone

    PubMed Central

    Lamazza, Luca; Garreffa, Girolamo; Laurito, Domenica; Lollobrigida, Marco; Palmieri, Luigi; De Biase, Alberto

    2016-01-01

    Purpose. Various parameters can influence temperature rise and detection during implant site preparation. The aim of this study is to investigate local temperature values in cortical and corticocancellous bovine bone during early stages of piezoelectric implant site preparation. Materials and Methods. 20 osteotomies were performed using a diamond tip (IM1s, Mectron Medical Technology, Carasco, Italy) on two different types of bovine bone samples, cortical and corticocancellous, respectively. A standardized protocol was designed to provide constant working conditions. Temperatures were measured in real time at a fixed position by a fiber optic thermometer. Results. Significantly higher drilling time (154.90 sec versus 99.00 sec; p < 0.0001) and temperatures (39.26°C versus 34.73°C; p = 0.043) were observed in the cortical group compared to the corticocancellous group. A remarkable variability of results characterized the corticocancellous blocks as compared to the blocks of pure cortical bone. Conclusion. Bone samples can influence heat generation during in vitro implant site preparation. When compared to cortical bone, corticocancellous samples present more variability in temperature values. Even controlling most experimental factors, the impact of bone samples still remains one of the main causes of temperature variability. PMID:27110567

  18. Temperature Values Variability in Piezoelectric Implant Site Preparation: Differences between Cortical and Corticocancellous Bovine Bone.

    PubMed

    Lamazza, Luca; Garreffa, Girolamo; Laurito, Domenica; Lollobrigida, Marco; Palmieri, Luigi; De Biase, Alberto

    2016-01-01

    Various parameters can influence temperature rise and detection during implant site preparation. The aim of this study is to investigate local temperature values in cortical and corticocancellous bovine bone during early stages of piezoelectric implant site preparation. 20 osteotomies were performed using a diamond tip (IM1s, Mectron Medical Technology, Carasco, Italy) on two different types of bovine bone samples, cortical and corticocancellous, respectively. A standardized protocol was designed to provide constant working conditions. Temperatures were measured in real time at a fixed position by a fiber optic thermometer. Significantly higher drilling time (154.90 sec versus 99.00 sec; p < 0.0001) and temperatures (39.26°C versus 34.73°C; p = 0.043) were observed in the cortical group compared to the corticocancellous group. A remarkable variability of results characterized the corticocancellous blocks as compared to the blocks of pure cortical bone. Bone samples can influence heat generation during in vitro implant site preparation. When compared to cortical bone, corticocancellous samples present more variability in temperature values. Even controlling most experimental factors, the impact of bone samples still remains one of the main causes of temperature variability.

  19. Effect of Cortical Bone Thickness on Detection of Intraosseous Lesions by Ultrasonography

    PubMed Central

    Adibi, Sadaf; Shakibafard, Alireza; Karimi Sarvestani, Zohreh; Saadat, Najmeh; Khojastepour, Leila

    2015-01-01

    Background. Usefulness of ultrasound (US) in detection of intrabony lesions has been showed. A cortical bone perforation or a very thin and intact cortical bone is prerequisite for this purpose. Objective. The current in vitro study was aimed at measuring the cut-off thickness of the overlying cortical bone which allows ultrasonic assessment of bony defects. Materials and Methods. 20 bovine scapula blocks were obtained. Samples were numbered from 1 to 20. In each sample, 5 artificial lesions were made. The lesions were made in order to increase the overlying bone thickness, from 0.1 mm in the first sample to 2 mm in the last one (with 0.1 mm interval). After that, the samples underwent ultrasound examinations by two practicing radiologists. Results. All five lesions in samples numbered 1 to 11 were detected as hypoechoic area. Cortical bone thickness more than 1.1 mm resulted in a failure in the detection of central lesions. Conclusion. We can conclude that neither bony perforation nor very thin cortical bones are needed to consider US to be an effective imaging technique in the evaluation of bony lesion. PMID:26366296

  20. Drilling in cortical bone: a finite element model and experimental investigations.

    PubMed

    Lughmani, Waqas A; Bouazza-Marouf, Kaddour; Ashcroft, Ian

    2015-02-01

    Bone drilling is an essential part of many orthopaedic surgery procedures, including those for internal fixation and for attaching prosthetics. Estimation and control of bone drilling forces are critical to prevent drill-bit breakthrough, excessive heat generation, and mechanical damage to the bone. An experimental and computational study of drilling in cortical bone has been conducted. A 3D finite element (FE) model for prediction of thrust forces experienced during bone drilling has been developed. The model incorporates the dynamic characteristics involved in the process along with geometrical considerations. An elastic-plastic material model is used to predict the behaviour of cortical bone during drilling. The average critical thrust forces and torques obtained using FE analysis are found to be in good agreement with the experimental results.

  1. Cortical Bone Morphological and Trabecular Bone Microarchitectural Changes in the Mandible and Femoral Neck of Ovariectomized Rats

    PubMed Central

    Hsu, Pei-Yu; Tsai, Ming-Tzu; Wang, Shun-Ping; Chen, Ying-Ju; Wu, Jay; Hsu, Jui-Ting

    2016-01-01

    Objective This study used microcomputed tomography (micro-CT) to evaluate the effects of ovariectomy on the trabecular bone microarchitecture and cortical bone morphology in the femoral neck and mandible of female rats. Materials and Methods Twelve female Wister rats were divided into two groups: the control and ovariectomized groups. The rats in the ovariectomized group received ovariectomy at 8 weeks of age; all the rats were sacrificed at 20 weeks of age, and their mandibles and femurs were removed and scanned using micro-CT. Four microstructural trabecular bone parameters were measured for the region below the first mandibular molar and the femoral neck region: bone volume fraction (BV/TV), trabecular thickness (TbTh), trabecular separation (TbSp), and trabecular number (TbN). In addition, four cortical bone parameters were measured for the femoral neck region: total cross-sectional area (TtAr), cortical area (CtAr), cortical bone area fraction (CtAr/TtAr), and cortical thickness (CtTh). The CtTh at the masseteric ridge was used to assess the cortical bone morphology in the mandible. The trabecular bone microarchitecture and cortical bone morphology in the femoral necks and mandibles of the control group were compared with those of the ovariectomized group. Furthermore, Spearman’s correlation (rs) was conducted to analyze the correlation between the osteoporosis conditions of the mandible and femoral neck. Results Regarding the trabecular bone microarchitectural parameters, the BV/TV of the trabecular bone microarchitecture in the femoral necks of the control group (61.199±11.288%, median ± interquartile range) was significantly greater than that of the ovariectomized group (40.329±5.153%). Similarly, the BV/TV of the trabecular bone microarchitecture in the mandibles of the control group (51.704±6.253%) was significantly greater than that of the ovariectomized group (38.486±9.111%). Furthermore, the TbSp of the femoral necks in the ovariectomized group

  2. Specifications for machining the bovine cortical bone in relation to its microstructure.

    PubMed

    Sugita, Naohiko; Mitsuishi, Mamoru

    2009-12-11

    Until date, many devices have been developed for cutting human bones during orthopedic surgeries. However, bones are anisotropic material, and their machining characteristics depend on the tool feed direction. In this study, microcutting of the bovine cortical bone is performed and its structure observed under a microscope. Furthermore, the formation of cutting chips and measurement of the cutting force during bone machining are dynamically observed while considering the anisotropy of bone tissue. In particular, the fracture of secondary osteons and crack propagation in bones are observed and analyzed. The results indicate that when the cut depth exceeds 20mum and is greater than the interval of concentric lamellae, cracks are formed together with chips. A new method for bone machining is proposed. This method is based on the characteristics of crack propagation in bones and is expected to produce low mechanical stress and realize highly efficient and precise machining of living tissues such as bones.

  3. Bone defect regeneration and cortical bone parameters of type 2 diabetic rats are improved by insulin therapy.

    PubMed

    Picke, A-K; Gordaliza Alaguero, I; Campbell, G M; Glüer, C-C; Salbach-Hirsch, J; Rauner, M; Hofbauer, L C; Hofbauer, C

    2016-01-01

    Zucker Diabetic Fatty (ZDF) rats represent an established model of type 2 diabetes mellitus (T2DM) and display several features of human diabetic bone disease, including impaired osteoblast function, decreased bone strength, and delayed bone healing. Here, we determined whether glycemic control by insulin treatment prevents skeletal complications associated with diabetes. Subcritical femur defects were created in diabetic (fa/fa) and non-diabetic (+/+) ZDF rats. Diabetic rats were treated once daily with long-lasting insulin glargin for 12weeks for glycemic control. Insulin treatment successfully maintained serum levels of glycated hemoglobin, while untreated diabetic rats showed a 2-fold increase. Trabecular and cortical bone mass measured by μCT were decreased in diabetic rats. Insulin treatment increased bone mass of the cortical, but not of the trabecular bone compartment. Dynamic histomorphometry revealed a lower bone formation rate at the trabecular and periosteal cortical bone in diabetic animals and decreased serum procollagen type 1 N-terminal propeptide (P1NP, -49%) levels. Insulin treatment partially improved these parameters. In T2DM, serum levels of tartrate-resistant acid phosphatase (TRAP, +32%) and C-terminal telopeptide (CTX, +49%) were increased. Insulin treatment further elevated TRAP levels, but did not affect CTX levels. While diabetes impaired bone defect healing, glycemic control with insulin fully reversed these negative effects. In conclusion, insulin treatment reversed the adverse effects of T2DM on bone defect regeneration in rats mainly by improving osteoblast function and bone formation. This article is part of a Special Issue entitled Bone and diabetes.

  4. Current Physical Activity Is Independently Associated With Cortical Bone Size and Bone Strength in Elderly Swedish Women.

    PubMed

    Nilsson, Martin; Sundh, Daniel; Mellström, Dan; Lorentzon, Mattias

    2017-03-01

    Physical activity is believed to have the greatest effect on the skeleton if exerted early in life, but whether or not possible benefits of physical activity on bone microstructure or geometry remain at old age has not been investigated in women. The aim of this study was to investigate if physical activity during skeletal growth and young adulthood or at old age was associated with cortical geometry and trabecular microarchitecture in weight-bearing and non-weight-bearing bone, and areal bone mineral density (aBMD) in elderly women. In this population-based cross-sectional study 1013 women, 78.2 ± 1.6 (mean ± SD) years old, were included. Using high-resolution 3D pQCT (XtremeCT), cortical cross-sectional area (Ct.CSA), cortical thickness (Ct.Th), cortical periosteal perimeter (Ct.Pm), volumetric cortical bone density (D.Ct), trabecular bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp) were measured at the distal (14% level) and ultra-distal tibia and radius, respectively. aBMD was assessed using DXA (Hologic Discovery A) of the spine and hip. A standardized questionnaire was used to collect information about previous exercise and the Physical Activity Scale for the Elderly (PASE) was used for current physical activity. A linear regression model (including levels of exercise during skeletal growth and young adulthood [10 to 30 years of age], PASE score, and covariates) revealed that level of current physical activity was independently associated with Ct.CSA (β = 0.18, p < 0.001) and Ct.Th (β = 0.15, p < 0.001) at the distal tibia, Tb.Th (β = 0.11, p < 0.001) and BV/TV (β = 0.10, p = 0.001) at the ultra-distal tibia, and total hip aBMD (β = 0.10, p < 0.001). Current physical activity was independently associated with cortical bone size, in terms of thicker cortex but not larger periosteal circumference, and higher bone strength at the distal

  5. Local Variation in Femoral Neck Cortical Bone: In Vitro Measured Bone Mineral Density, Geometry and Mechanical Properties.

    PubMed

    Coutts, Louise V; Jenkins, Thomas; Oreffo, Richard O C; Dunlop, Doug G; Cooper, Cyrus; Harvey, Nicholas C; Thurner, Philipp J

    2015-12-17

    Age- and disease (osteoporotic fractured and osteoarthritic tissue)-related changes in the distribution of cortical bone were examined, using a multimodality approach, including measurement of local density, geometry and mechanical properties, where changes in these properties can give rise to instability and increasing probability of fracture. In contrast to the majority of previously reported research, this study also focuses on the characteristic non-circular femoral neck cross-sectional geometry and variation in bone mineral density (BMD) around the femoral neck. Twenty-two osteoarthritic and 7 osteoporotic femoral neck slices, collected from elective and trauma-related arthroplasty, and 16 cadaveric donor tissue controls were tested mechanically using Reference Point Indentation (BioDent™, Active Life Technologies®, Santa Barbara, CA) and then scanned with in vitro-based radiography intended to replicate the dual-energy X-ray absorptiometry technique. All parameters were measured regionally around the circumference of the femoral neck, allowing examination of spatial variability within the cortical bone. Fractured tissue was less resistant to indentation in the thinner superolateral segment compared to other segments and other groups. BMD around the fractured femoral necks appeared more consistent than that of nonfractured tissue, where BMD was reduced in the superolateral segment for the other groups. Cortical bone was thin in the superolateral segment for all groups except for the osteoarthritic group, and was thicker in the inferomedial segment for both osteoarthritic and fractured groups, resulting in the largest variation in buckling ratio (ratio of cortical bone diameter to cortical bone thickness) around the femoral neck for the fractured group. With age, healthy controls appeared to have lower inferomedial cortical thickness, whereas no significant differences in Reference Point Indentation measurements and density were observed. The study has

  6. Effect of microstructure on micromechanical performance of dry cortical bone tissues

    SciTech Connect

    Yin Ling; Venkatesan, Sudharshan; Kalyanasundaram, Shankar; Qin Qinghua

    2009-12-15

    The mechanical properties of bone depend on composition and structure. Previous studies have focused on macroscopic fracture behavior of bone. In the present study, we performed microindentation studies to understand the deformation properties and microcrack-microstructure interactions of dry cortical bone. Dry cortical bone tissues from lamb femurs were tested using Vickers indentation with loads of 0.245-9.8 N. We examined the effect of bone microstructure on deformation and crack propagation using scanning electron microscopy (SEM). The results showed the significant effect of cortical bone microstructure on indentation deformation and microcrack propagation. The indentation deformation of the dry cortical bone was basically plastic at any applied load with a pronounced viscoelastic recovery, in particular at lower loads. More microcracks up to a length of approximately 20 {mu}m occurred when the applied load was increased. At loads of 4.9 N and higher, most microcracks were found to develop from the boundaries of haversian canals, osteocyte lacunae and canaliculi. Some microcracks propagated from the parallel direction of the longitudinal interstitial lamellae. At loads 0.45 N and lower, no visible microcracks were observed.

  7. Rapid increase of carbonate in cortical bones of hens during laying period.

    PubMed

    Li, Z; Li, Q; Wang, S-J; Zhang, L; Qiu, J-Y; Wu, Y; Zhou, Z-L

    2016-12-01

    The incorporation of carbonate has been recognized as an evident change in bone mineral (bioapatite) during aging. Laying hens (Gushi layer) at 4 stages of age (8 hens each stage) were studied by Raman spectroscopy and X-ray radiography to investigate the mineralogical changes and bone density, respectively. Cortical bones of the humerus and femur show a rapid increase of carbonate (∼1.9 wt.%) from sexual maturity to the peak of hens' laying period, while the densities of the cortical bones are relatively stable. Before sexual maturity, the density of the cortical bones increases considerably during aging. However, after the peak of the laying period, only femoral density continues elevating. Carbonate contents in the cortical bones reach the maximum at the peak of the laying period. Two pathways (halted growth of density and Ca-release due to the CO3 incorporation) could both contribute to the intense Ca requirement for egg laying. Crystallization, however, has no significant changes during aging and the laying period. This study could shed light on the mechanism of mineral losses due to CO3 incorporation, and also shows the advantages of Raman spectroscopy in tracking mineral loss in poultry bone.

  8. Effect of cryo-induced microcracks on microindentation of hydrated cortical bone tissue

    SciTech Connect

    Yin Ling; Venkatesan, Sudharshan; Webb, Daryl; Kalyanasundaram, Shankar; Qin Qinghua

    2009-08-15

    Microcracks accumulate in cortical bone tissue as a consequence of everyday cyclic loading. However, it remains unclear to what extent microdamage accumulation contributes to an increase in fracture risk. A cryo-preparation technique was applied to induce microcracks in cortical bone tissue. Microcracks with lengths up to approximately 20 {mu}m, which were initiated mainly on the boundaries of haversian canals, were observed with cryo-scanning electron microscopy. A microindentation technique was applied to study the mechanical loading effect on the microcracked hydrated bone tissue. The microindentation patterns were section-scanned using confocal laser scanning microscopy to understand the deformation and bone damage mechanisms made by mechanical loading. The results show that there was no significant difference with respect to microhardness between the original and microcracked hydrated cortical bone tissues (ANOVA, p > 0.05). The cryo-induced microcracks in the bone tissue were not propagated further under the mechanical loads applied. The deformation mechanism of the microcracked cortical bone tissue was plastic deformation, not brittle fracture.

  9. An approach to the histomorphological and histochemical variations of the humerus cortical bone through human ontogeny

    PubMed Central

    Cambra-Moo, Oscar; Nacarino Meneses, Carmen; Rodríguez Barbero, Miguel Ángel; García Gil, Orosia; Rascón Pérez, Josefina; Rello-Varona, Santiago; D'Angelo, Manuel; Campo Martín, Manuel; González Martín, Armando

    2014-01-01

    For many years, clinical and non-clinical investigations have investigated cortical bone structure in an attempt to address questions related to normal bone development, mineralisation, pathologies and even evolutionary trends in our lineage (adaptations). Research in the fields of medicine, materials science, physical anthropology, palaeontology, and even archaeobiology has contributed interesting data. However, many questions remain regarding the histomorphological and histochemical variations in human cortical bone during different stages of life. In the present work, we describe a study of long bone cortex transformations during ontogeny. We analysed cross-sections of 15 human humeri histomorphologically and histochemically from perinatal to adult age, marking and quantifying the spatial distribution of bone tissue types using GIS software and analysing the mineral composition and crystallinity of the mineralised cortex using Raman spectroscopy and X-ray diffraction. Our results allowed us to propose that human cortical bone undergoes three main ‘events’ through ontogeny that critically change the proportions and structure of the cortex. In early development, bone is not well mineralised and proportionally presents a wide cortex that narrows through the end of childhood. Before reaching complete maturity, the bone mineral area increases, allowing the bone to nearly reach the adult size. The medullary cavity is reduced, and the mineral areas have a highly ordered crystalline structure. The last event occurs in adulthood, when the ‘oldest’ individuals present a reduced mineralised area, with increasing non-mineralised cavities (including the medullary cavity) and reduced crystalline organisation. PMID:24660964

  10. Effect of aging on the transverse toughness of human cortical bone: evaluation by R-curves.

    PubMed

    Koester, K J; Barth, H D; Ritchie, R O

    2011-10-01

    The age-related deterioration in the quality (e.g., strength and fracture resistance) and quantity (e.g., bone-mineral density) of human bone, together with increased life expectancy, is responsible for increasing incidence of bone fracture in the elderly. The present study describes ex vivo fracture experiments to quantitatively assess the effect of aging on the fracture toughness properties of human cortical bone specifically in the transverse (breaking) orientation. Because bone exhibits rising crack-growth resistance with crack extension, the aging-related transverse toughness is evaluated in terms of resistance-curve (R-curve) behavior, measured for bone taken from a wide range of age groups (25-74 years). Using this approach, both the ex vivo crack-initiation and crack-growth toughness are determined and are found to deteriorate with age; however, the effect is far smaller than that reported for the longitudinal toughness of cortical bone. Whereas the longitudinal crack-growth toughness has been reported to be reduced by almost an order of magnitude for human cortical bone over this age range, the corresponding age-related decrease in transverse toughness is merely ~14%. Similar to that reported for X-ray irradiated bone, with aging cracks in the transverse direction are subjected to an increasing incidence of crack deflection, principally along the cement lines, but the deflections are smaller and result in a generally less tortuous crack path.

  11. Alendronate treatment alters bone tissues at multiple structural levels in healthy canine cortical bone.

    PubMed

    Acevedo, Claire; Bale, Hrishikesh; Gludovatz, Bernd; Wat, Amy; Tang, Simon Y; Wang, Mingyue; Busse, Björn; Zimmermann, Elizabeth A; Schaible, Eric; Allen, Matthew R; Burr, David B; Ritchie, Robert O

    2015-12-01

    Bisphosphonates are widely used to treat osteoporosis, but have been associated with atypical femoral fractures (AFFs) in the long term, which raises a critical health problem for the aging population. Several clinical studies have suggested that the occurrence of AFFs may be related to the bisphosphonate-induced changes of bone turnover, but large discrepancies in the results of these studies indicate that the salient mechanisms responsible for any loss in fracture resistance are still unclear. Here the role of bisphosphonates is examined in terms of the potential deterioration in fracture resistance resulting from both intrinsic (plasticity) and extrinsic (shielding) toughening mechanisms, which operate over a wide range of length-scales. Specifically, we compare the mechanical properties of two groups of humeri from healthy beagles, one control group comprising eight females (oral doses of saline vehicle, 1 mL/kg/day, 3 years) and one treated group comprising nine females (oral doses of alendronate used to treat osteoporosis, 0.2mg/kg/day, 3 years). Our data demonstrate treatment-specific reorganization of bone tissue identified at multiple length-scales mainly through advanced synchrotron x-ray experiments. We confirm that bisphosphonate treatments can increase non-enzymatic collagen cross-linking at molecular scales, which critically restricts plasticity associated with fibrillar sliding, and hence intrinsic toughening, at nanoscales. We also observe changes in the intracortical architecture of treated bone at microscales, with partial filling of the Haversian canals and reduction of osteon number. We hypothesize that the reduced plasticity associated with BP treatments may induce an increase in microcrack accumulation and growth under cyclic daily loadings, and potentially increase the susceptibility of cortical bone to atypical (fatigue-like) fractures.

  12. Loss of Prostaglandin E2-induced Extra Cortical Bone After its Withdrawal in Rats

    NASA Technical Reports Server (NTRS)

    Jee, Webster S. S.; Ke, Hua Zhu; Li, Xiao Jian

    1992-01-01

    The object of this study was to determine the fate of PGE2-(Prostaglandin E2) induced new cortical bone mass after withdrawal of PGE2 administration. Seven-month-old male Sprague-Dawley rats were given subcutaneous injections of 1, 3 and 6 mg PGE2/kg/day for 60 days and then withdrawn for 60 and 120 days (on/off treatment). Histomorphometric analyses were performed on double-fluorescent-labeled undecalcified tibial shaft sections (proximal to the tibiofibular junction). In a previous report we showed that after 60, 120 and 180 days of daily PGE2 (on)treatment, a new steady state was achieved marked by increased total bone area (+16%, +25% and +34% with 1, 3 and 6 mg PGE2/kg/day) when compared to age-matched controls. The continuous PGE2 treatment stimulated periosteal and endocortical lamellar bone formation, activated endocortical woven trabecular bone formation and intracortical bone resorption. These responses increased cortical bone mass since the bone formation exceeded bone resorption. The current study showed that after withdrawal of PGE2 for 60 and 120 days, the extra endocortical bone, which was induced by the first 60-days treatment, was resorbed, but the new subperiosteal bone persisted resulting in a tibial shaft with larger cross sectional and marrow areas. Despite that, there was still the same amount of bone mass in these shafts as in age-related controls. A new steady state was achieved after 60 days of withdrawal, in which the bone mass and bone formation activity approximated that of age-related controls. It was concluded that maintaining the extra PGE2-induced cortical bone mass depends on continuous daily administration of PGE2.

  13. Loss of Prostaglandin E2-induced Extra Cortical Bone after its Withdrawal in Rats

    NASA Technical Reports Server (NTRS)

    Jee, Webster S. S.; Ke, Hua Zhu; Li, Xiao Jian

    1992-01-01

    The object of this study was to determine the fate of PGE2-induced new cortical bone mass after withdrawal of PGE2 administration. Seven-month-old male Sprague-Dawley rats were given subcutaneous injections of 1, 3 and 6 mg PGE2/kg/day for 60 days and then withdrawn for 60 and 120 days (on/off treatment). Histomorphometric analyses were performed on double-fluorescent-labeled undecalcified tibial shaft sections (proximal to the tibiofibular junction). In a previous report we showed that after 60, 120 and 180 days of daily PGE2 (on)treatment, a new steady state was achieved marked by increased total bone area (+ 16%, +25% and + 34% with 1, 3 and 6 mg PGE2/kg/day) when compared to age-matched controls. The continuous PGE2 treatment stimulated periosteal and endocortical lamellar bone formation, activated endocortical woven trabecular bone formation and intracortical bone resorption. These responses increased cortical bone mass since the bone formation exceeded bone resorption. The current study showed that after withdrawal of PGE2 for 60 and 120 days, the extra endocortical bone, which was induced by the first 60-days treatment, was resorbed, but the new subperiosteal bone persisted resulting in a tibial shaft with larger cross sectional and marrow areas. Despite that, there was still the same amount of bone mass in these shafts as in age-related controls. A new steady state was achieved after 60 days of withdrawal, in which the bone mass and bone formation activity approximated that of age-related controls. It was concluded that maintaining the extra PGE2-induced cortical bone mass depends on continuous daily administration of PGE2.

  14. A comparative study of young and mature bovine cortical bone.

    PubMed

    Manilay, Zherrina; Novitskaya, Ekaterina; Sadovnikov, Ernest; McKittrick, Joanna

    2013-02-01

    The mechanical properties and microstructure of young and mature bovine femur bone were investigated by optical microscopy and compression testing in the longitudinal and transverse directions for untreated, deproteinized and demineralized cases. Optical microscopy revealed that mature bone has a more established and less porous microstructure compared to young bone. Mature bone was found to be stronger in both directions for the untreated and deproteinized cases. Mature untreated bone was also found to be stiffer and less tough compared to young bone in both directions. These results are related to the increase in mineralization of mature bone and significant microstructural differences. Young bone was found to be stronger in both directions for the demineralized case, which is attributed to alterations in the collagen network with age.

  15. Mechanistic fracture criteria for the failure of human cortical bone

    SciTech Connect

    Nalla, Ravi K.; Kinney, John H.; Ritchie, Robert O.

    2002-12-13

    A mechanistic understanding of fracture in human bone is critical to predicting fracture risk associated with age and disease. Despite extensive work, a mechanistic framework for describing how the underlying microstructure affects the failure mode in bone is lacking.

  16. Regional variability in secondary remodeling within long bone cortices of catarrhine primates: the influence of bone growth history

    PubMed Central

    McFarlin, Shannon C; Terranova, Carl J; Zihlman, Adrienne L; Enlow, Donald H; Bromage, Timothy G

    2008-01-01

    Secondary intracortical remodeling of bone varies considerably among and within vertebrate skeletons. Although prior research has shed important light on its biomechanical significance, factors accounting for this variability remain poorly understood. We examined regional patterning of secondary osteonal bone in an ontogenetic series of wild-collected primates, at the midshaft femur and humerus of Chlorocebus (Cercopithecus) aethiops (n = 32) and Hylobates lar (n = 28), and the midshaft femur of Pan troglodytes (n = 12). Our major objectives were: 1) to determine whether secondary osteonal bone exhibits significant regional patterning across inner, mid-cortical and outer circumferential cortical rings within cross-sections; and if so, 2) to consider the manner in which this regional patterning may reflect the influence of relative tissue age and other circumstances of bone growth. Using same field-of-view images of 100-µm-thick cross-sections acquired in brightfield and circularly polarized light microscopy, we quantified the percent area of secondary osteonal bone (%HAV) for whole cross-sections and across the three circumferential rings within cross-sections. We expected bone areas with inner and middle rings to exhibit higher %HAV than the outer cortical ring within cross-sections, the latter comprising tissues of more recent depositional history. Observations of primary bone microstructural development provided an additional context in which to evaluate regional patterning of intracortical remodeling. Results demonstrated significant regional variability in %HAV within all skeletal sites. As predicted,%HAV was usually lowest in the outer cortical ring within cross-sections. However, regional patterning across inner vs. mid-cortical rings showed a more variable pattern across taxa, age classes, and skeletal sites examined. Observations of primary bone microstructure revealed that the distribution of endosteally deposited bone had an important influence on the

  17. Regional variability in secondary remodeling within long bone cortices of catarrhine primates: the influence of bone growth history.

    PubMed

    McFarlin, Shannon C; Terranova, Carl J; Zihlman, Adrienne L; Enlow, Donald H; Bromage, Timothy G

    2008-09-01

    Secondary intracortical remodeling of bone varies considerably among and within vertebrate skeletons. Although prior research has shed important light on its biomechanical significance, factors accounting for this variability remain poorly understood. We examined regional patterning of secondary osteonal bone in an ontogenetic series of wild-collected primates, at the midshaft femur and humerus of Chlorocebus (Cercopithecus) aethiops (n = 32) and Hylobates lar (n = 28), and the midshaft femur of Pan troglodytes (n = 12). Our major objectives were: 1) to determine whether secondary osteonal bone exhibits significant regional patterning across inner, mid-cortical and outer circumferential cortical rings within cross-sections; and if so, 2) to consider the manner in which this regional patterning may reflect the influence of relative tissue age and other circumstances of bone growth. Using same field-of-view images of 100-microm-thick cross-sections acquired in brightfield and circularly polarized light microscopy, we quantified the percent area of secondary osteonal bone (%HAV) for whole cross-sections and across the three circumferential rings within cross-sections. We expected bone areas with inner and middle rings to exhibit higher %HAV than the outer cortical ring within cross-sections, the latter comprising tissues of more recent depositional history. Observations of primary bone microstructural development provided an additional context in which to evaluate regional patterning of intracortical remodeling. Results demonstrated significant regional variability in %HAV within all skeletal sites. As predicted,%HAV was usually lowest in the outer cortical ring within cross-sections. However, regional patterning across inner vs. mid-cortical rings showed a more variable pattern across taxa, age classes, and skeletal sites examined. Observations of primary bone microstructure revealed that the distribution of endosteally deposited bone had an important influence on

  18. Evaluation of bound and pore water in cortical bone using ultrashort-TE MRI.

    PubMed

    Chen, Jun; Grogan, Shawn P; Shao, Hongda; D'Lima, Darryl; Bydder, Graeme M; Wu, Zhihong; Du, Jiang

    2015-12-01

    Bone water exists in different states with the majority bound to the organic matrix and to mineral, and a smaller fraction in 'free' form in the pores of cortical bone. In this study, we aimed to develop and evaluate ultrashort-TE (UTE) MRI techniques for the assessment of T2*, T1 and concentration of collagen-bound and pore water in cortical bone using a 3-T clinical whole-body scanner. UTE MRI, together with an isotope study using tritiated and distilled water (THO-H2O) exchange, as well as gravimetric analysis, were performed on ten sectioned bovine bone samples. In addition, 32 human cortical bone samples were prepared for comparison between the pore water concentration measured with UTE MRI and the cortical porosity derived from micro-computed tomography (μCT). A short T2* of 0.27 ± 0.03 ms and T1 of 116 ± 6 ms were observed for collagen-bound water in bovine bone. A longer T2* of 1.84 ± 0.52 ms and T1 of 527 ± 28 ms were observed for pore water in bovine bone. UTE MRI measurements showed a pore water concentration of 4.7-5.3% by volume and collagen-bound water concentration of 15.7-17.9% in bovine bone. THO-H2O exchange studies showed a pore water concentration of 5.9 ± 0.6% and collagen-bound water concentration of 18.1 ± 2.1% in bovine bone. Gravimetric analysis showed a pore water concentration of 6.3 ± 0.8% and collagen-bound water concentration of 19.2 ± 3.6% in bovine bone. A mineral water concentration of 9.5 ± 0.6% was derived in bovine bone with the THO-H2O exchange study. UTE-measured pore water concentration is highly correlated (R(2) = 0.72, p < 0.0001) with μCT porosity in the human cortical bone study. Both bovine and human bone studies suggest that UTE sequences could reliably measure collagen-bound and pore water concentration in cortical bone using a clinical scanner.

  19. Quantitative genetics of cortical bone mass in healthy 10-year-old children from the Fels Longitudinal Study

    PubMed Central

    Duren, Dana L.; Sherwood, Richard J.; Choh, Audrey C.; Czerwinski, Stefan A.; Chumlea, Wm. Cameron; Lee, Miryoung; Sun, Shumei S.; Demerath, Ellen W.; Siervogel, Roger M.; Towne, Bradford

    2007-01-01

    The genetic influences on bone mass likely change throughout the life span, but most genetic studies of bone mass regulation have focused on adults. There is, however, a growing awareness of the importance of genes influencing the acquisition of bone mass during childhood on lifelong bone health. The present investigation examines genetic influences on childhood bone mass by estimating the residual heritabilities of different measures of second metacarpal bone mass in a sample of 600 10-year-old participants from 144 families in the Fels Longitudinal Study. Bivariate quantitative genetic analyses were conducted to estimate genetic correlations between cortical bone mass measures, and measures of bone growth and development. Using a maximum likelihood-based variance components method for pedigree data, we found a residual heritability estimate of 0.71 for second metacarpal cortical index. Residual heritability estimates for individual measures of cortical bone (e.g., lateral cortical thickness, medial cortical thickness) ranged from 0.47 to 0.58, at this pre-pubertal childhood age. Low genetic correlations were found between cortical bone measures and both bone length and skeletal age. However, after Bonferonni adjustment for multiple testing, ρG was not significantly different from 0 for any of these pairs of traits. Results of this investigation provide evidence of significant genetic control over bone mass largely independent of maturation while bones are actively growing and before rapid accrual of bone that typically occurs during puberty. PMID:17056310

  20. Quantifying Temperature-Dependent T1 Changes in Cortical Bone Using Ultrashort Echo-Time MRI

    PubMed Central

    Han, Misung; Rieke, Viola; Scott, Serena J; Ozhinsky, Eugene; Salgaonkar, Vasant A; Jones, Peter D; Larson, Peder E Z; Diederich, Chris J; Krug, Roland

    2015-01-01

    Purpose To demonstrate the feasibility of using ultrashort echo-time (UTE) MRI to quantify T1 changes in cortical bone due to heating. Methods Variable flip-angle T1 mapping combined with 3D UTE imaging was used to measure T1 in cortical bone. A calibration experiment was performed to detect T1 changes with temperature in ex vivo cortical bone samples from a bovine femur. Ultrasound heating experiments were performed using an interstitial applicator in ex vivo bovine femur specimens, and heat-induced T1 changes were quantified. Results The calibration experiment demonstrated that T1 increases with temperature in cortical bone. We observed a linear relationship between temperature and T1 with a linear coefficient of 0.67–0.84 ms/°C over a range of 25–70°C. The ultrasound heating experiments showed increased T1 changes in the heated regions, and the relationship between the temperature changes and T1 changes was similar to that of the calibration. Conclusion We demonstrated a temperature dependence of T1 in ex vivo cortical bone using a variable flip-angle UTE T1 mapping method. PMID:26390357

  1. A histological investigation on tissue responses to titanium implants in cortical bone of the rat femur.

    PubMed

    Ohtsu, A; Kusakari, H; Maeda, T; Takano, Y

    1997-03-01

    Implant materials are placed under various sites-including cortical bone, spongy bone, and bone marrow-at the same time according to the depth at implantation. Although cortical bone is an important site for the prognosis of implantation, detailed reports on tissue responses to implantation have been meager. The present study aims to reveal tissue responses to pure titanium implantation in rat femoris cortical bone. The rats received titanium bars surgically in their femurs and were sacrificed 1 day to 40 weeks post-implantation. The prepared tissue specimens were processed for light and transmission electron microscopy (TEM). Further histochemical detections were performed. One day post-implantation, empty osteocytic lacunae indicating degeneration of osteocytes were found in pre-existing cortical bone around the implant. Such pre-existing bone was replaced by new bone, but remained in part even 40 weeks post-implantation. Light microscopy showed that direct contact between the implant and new bone was identified 12 weeks post-implantation. Chronological and ultrastructural observation showed that new bone deposition appeared to proceed toward the implant, and that the intervening layer at the interface was derived from the degenerated debris of multinucleated giant cells and/or osteoblasts. Furthermore, it seemed that the width of intervening layer varied in relation to the distance from the blood vessels. The cells showing tartrate resistant acid phosphatase activity possessed cytological features of osteoclasts under TEM; they were frequently observed in perivascular sites near the implants even after osseointegration, suggesting that bone remodeling took place steadily around the implant.

  2. Simulation study of axial ultrasound transmission in heterogeneous cortical bone model

    NASA Astrophysics Data System (ADS)

    Takano, Koki; Nagatani, Yoshiki; Matsukawa, Mami

    2017-07-01

    Ultrasound propagation in a heterogeneous cortical bone was studied. Using a bovine radius, the longitudinal wave velocity distribution in the axial direction was experimentally measured in the MHz range. The bilinear interpolation and piecewise cubic Hermite interpolation methods were applied to create a three-dimensional (3D) precise velocity model of the bone using experimental data. By assuming the uniaxial anisotropy of the bone, the distributions of all elastic moduli of a 3D heterogeneous model were estimated. The elastic finite-difference time-domain method was used to simulate axial ultrasonic wave propagation. The wave propagation in the initial model was compared with that in the thinner model, where the inner part of the cortical bone model was removed. The wave front of the first arriving signal (FAS) slightly depended on the heterogeneity in each model. Owing to the decrease in bone thickness, the propagation behavior also changed and the FAS velocity clearly decreased.

  3. Hindlimb unloading has a greater effect on cortical compared with cancellous bone in mature female rats

    NASA Technical Reports Server (NTRS)

    Allen, Matthew R.; Bloomfield, Susan A.

    2003-01-01

    This study was designed to determine the effects of 28 days of hindlimb unloading (HU) on the mature female rat skeleton. In vivo proximal tibia bone mineral density and geometry of HU and cage control (CC) rats were measured with peripheral quantitative computed tomography (pQCT) on days 0 and 28. Postmortem pQCT, histomorphometry, and mechanical testing were performed on tibiae and femora. After 28 days, HU animals had significantly higher daily food consumption (+39%) and lower serum estradiol levels (-49%, P = 0.079) compared with CC. Proximal tibia bone mineral content and cortical bone area significantly declined over 28 days in HU animals (-4.0 and 4.8%, respectively), whereas total and cancellous bone mineral densities were unchanged. HU animals had lower cortical bone formation rates and mineralizing surface at tibial midshaft, whereas differences in similar properties were not detected in cancellous bone of the distal femur. These results suggest that cortical bone, rather than cancellous bone, is more prominently affected by unloading in skeletally mature retired breeder female rats.

  4. Early cortical bone healing around loaded titanium implants: a histological study in the rabbit.

    PubMed

    Slaets, Elke; Naert, Ignace; Carmeliet, Geert; Duyck, Joke

    2009-02-01

    To identify the role of immediate implant loading on the early phases of the bone healing responses. Implants were placed in rabbit tibial diaphyses and left to heal for 3, 7, 14, 28 or 42 days. Half of the animals received an immediate loading protocol of 2.2 N at 3 Hz for 1800 cycles and 5 days/week, whereas the others served as unloaded controls. Histological assessment was combined with histomorphometrical measurements. At early time-points, an endosteal and periosteal new bone formation was found, while the cortex itself contained damaged osteocytes. At later time-points, new bone formation was also found at the cortical level itself. Differences between groups were found mainly in this new bone formation process, with larger reactions for the endosteal and periosteal bone in the loaded group after 28 and 42 days, respectively. At the end-point of the experiment, bone formation at the cortical level was reduced in the loaded group compared with the control group. These results show that the immediate loading protocol caused no differences in the sequential events leading to osseointegration in cortical bone. However, the processes of new bone formation originating from the endosteum and the periosteum lasted longer compared with the unloaded controls.

  5. Hindlimb unloading has a greater effect on cortical compared with cancellous bone in mature female rats

    NASA Technical Reports Server (NTRS)

    Allen, Matthew R.; Bloomfield, Susan A.

    2003-01-01

    This study was designed to determine the effects of 28 days of hindlimb unloading (HU) on the mature female rat skeleton. In vivo proximal tibia bone mineral density and geometry of HU and cage control (CC) rats were measured with peripheral quantitative computed tomography (pQCT) on days 0 and 28. Postmortem pQCT, histomorphometry, and mechanical testing were performed on tibiae and femora. After 28 days, HU animals had significantly higher daily food consumption (+39%) and lower serum estradiol levels (-49%, P = 0.079) compared with CC. Proximal tibia bone mineral content and cortical bone area significantly declined over 28 days in HU animals (-4.0 and 4.8%, respectively), whereas total and cancellous bone mineral densities were unchanged. HU animals had lower cortical bone formation rates and mineralizing surface at tibial midshaft, whereas differences in similar properties were not detected in cancellous bone of the distal femur. These results suggest that cortical bone, rather than cancellous bone, is more prominently affected by unloading in skeletally mature retired breeder female rats.

  6. Clinical, haematological and radiological evaluation of fragmented autogenous cortical bone grafting of radius in dogs.

    PubMed

    Grover, R K; Sobti, V K

    1998-07-01

    In eight clinically healthy dogs, a midshaft diaphyseal defect of 2 cm was created in the right radius ulna. This gap was maintained by fixing a four hole sherman bone plate on the radius. In four dogs, the gap was filled with autogenous cancellous bone grafts (2-5 mm in diameter) harvested from the proximal end of the tibia (group 1). In the remaining 4 dogs, the fracture gap was filled with autogenous cortical bone fragments (ACBF) of 2-5 mm diameter made from the same 2 cm piece of bone removed from the radius. While comparing various clinical observations, it appeared that healing of the wounds and bearing of the weight on the grafted limb in dogs subjected to ACBF graft were similar to those given autogenous cancellous bone graft. In radiographs, taken on the 30th day in group 1, a fairly good amount of callus was found emerging from fracture ends but the whole of the bone graft area was not covered by bony density even on the 60th day. In group 2 (ACBF), 45th day radiograph revealed that the callus from the fracture end was mixing up with the cortical bone fragments, and at the 60th day, the callus was clearly found invading the cortical bone fragments grafted in the fracture gap.

  7. Variations of mechanical property of out circumferential lamellae in cortical bone along the radial by nanoindentation

    NASA Astrophysics Data System (ADS)

    Sun, Xingdong; Zhao, Hongwei; Yu, Yang; Zhang, Shizhong; Ma, Zhichao; Li, Ning; Yu, Miao; Hou, Pengliang

    2016-11-01

    Because the out circumferential lamellae have a special protective effect on the cortical bone, it is very important to understand the variations of the mechanical property of the out circumferential lamellae in cortical bone. For the purpose, the elasticity modulus and hardness of out circumferential lamellae in cortical bone were investigated in two orthogonal planes by nanoindentation, and the comparisons were made for both elasticity modulus and hardness between the two orthogonal planes. From the experiments, the decreasing trend was discovered for elasticity modulus from inside to outside in the transverse plane and ruleless variations tendency was presented in the longitudinal plane. The hardness presented the same variations in two orthogonal planes with elasticity modulus in respective plane. In the same layer, the elasticity modulus in the transverse plane was higher than that in the longitudinal plane, and the difference values between them turned to be smaller. In contrast, the hardness in the longitudinal plane was higher than that in the transverse plane in all the layers. From the heterogeneity and the microstructure of the material, the influence factors were discussed. A soft to hard structure model was put forward, and the coordinating protection mechanism of buffer and support was described. Investigation of variations of mechanical properties of out circumferential lamellae in cortical bone can provide some new understanding in researches of fracture of bone, interface load effect and design of bone graft.

  8. A new algorithm to improve assessment of cortical bone geometry in pQCT.

    PubMed

    Cervinka, Tomas; Sievänen, Harri; Lala, Deena; Cheung, Angela M; Giangregorio, Lora; Hyttinen, Jari

    2015-12-01

    High-resolution peripheral quantitative computed tomography (HR-pQCT) is now considered the leading imaging modality in bone research. However, access to HR-pQCT is limited and image acquisition is mainly constrained only for the distal third of appendicular bones. Hence, the conventional pQCT is still commonly used despite inaccurate threshold-based segmentation of cortical bone that can compromise the assessment of whole bone strength. Therefore, this study addressed whether the use of an advanced image processing algorithm, called OBS, can enhance the cortical bone analysis in pQCT images and provide similar information to HR-pQCT when the same volumes of interest are analyzed. Using pQCT images of European Forearm Phantom (EFP), and pQCT and HR-pQCT images of the distal tibia from 15 cadavers, we compared the results from the OBS algorithm with those obtained from common pQCT analyses, HR-pQCT manual analysis (considered as a gold standard) and common HR-pQCT analysis dual threshold technique.We found that the use of OBS segmentation method for pQCT image analysis of EFP data did not result in any improvement but reached similar performance in cortical bone delineation as did HR-pQCT image analyses. The assessments of cortical cross-sectional bone area and thickness by OBS algorithm were overestimated by less than 4% while area moments of inertia were overestimated by ~5–10%, depending on reference HR-pQCT analysis method. In conclusion, this study showed that the OBS algorithm performed reasonably well and it offers a promising practical tool to enhance the assessment of cortical bone geometry in pQCT.

  9. Ultrasound strain elastography in assessment of cortical mechanical behavior in acute renal vein occlusion: in vivo animal model.

    PubMed

    Gao, Jing; He, Wen; Cheng, Ling-Gang; Li, Xiao-Ya; Zhang, Xiou-Ru; Juluru, Krishna; Al Khori, Noor; Coya, Adrienne; Min, Robert

    2015-01-01

    To assess the correlation of quantitative ultrasound strain parameters with the severity of cortical edema in renal vein occlusion, we prospectively performed ultrasound strain elastography on a canine acute renal vein occlusion model prior to and following 10, 20, and 40min of renal vein ligation. Strain and strain relaxation time representing the deformation and relaxation of the renal cortices and reference soft tissue were produced by the external compression with the ultrasound transducer and estimated using commercially available 2-D speckle tracking software. Cortical thickness was additionally measured. Repeated-measures analysis of variance was used to examine the difference in cortical thickness, strain ratio (mean cortical strain divided by mean reference tissue strain), and strain relaxation time ratio (cortical relaxation time divided by reference tissue relaxation time) prior to and after renal vein ligation. Pearson's correlation coefficient was applied to test the relationship between strain parameters and the time of the renal vein ligation. There was a strong positive correlation between the duration of renal vein ligation and strain (R(2)=0.97) and strain relaxation time (R(2)=0.98) ratios. Significant differences in strain and strain relaxation time ratios were found at all measured timepoints (all P≪.001). Cortical thickness, however, showed no significant difference between timepoints (P=.065). Our result suggest that strain and strain relaxation time ratios may be used as quantitative markers for the assessment of the renal cortical mechanical behavior in subclinical acute renal vein occlusion.

  10. Three-dimensional mapping of cortical bone thickness in subjects with different vertical facial dimensions.

    PubMed

    Sadek, Mais Medhat; Sabet, Noha Ezat; Hassan, Islam Tarek

    2016-12-01

    The purpose of this study was to determine differences in cortical bone thickness among subjects with different vertical facial dimensions using cone beam computed tomography (CBCT). From 114 pre-treatment CBCT scans, 48 scans were selected to be included in the study. CBCT-synthesized lateral cephalograms were used to categorize subjects into three groups based on their vertical skeletal pattern. Cortical bone thickness (CBT) at two vertical levels (4 and 7 mm) from the alveolar crest were measured in the entire tooth-bearing region in the maxilla and mandible. Significant group differences were detected with high-angle subjects having significantly narrower inter-radicular CBT at some sites as compared to average- and low-angle subjects. Inter-radicular cortical bone is thinner in high-angle than in average- or low-angle subjects in few selected sites at the vertical height in which mini-implants are commonly inserted for orthodontic anchorage.

  11. Mandibular Inferior Cortical Bone Thickness on Panoramic Radiographs in Patients using Bisphosphonates

    PubMed Central

    Torres, Sandra R.; Chen, Curtis S. K.; Leroux, Brian G.; Lee, Peggy P.; Hollender, Lars G.; Lloid, Michelle; Drew, Shane Patrick; Schubert, Mark M.

    2015-01-01

    Objective To detect dimensional changes in the mandibular cortical bone associated with bisphosphonate (BP) use and to correlate the measurements of the cortical bone with the cumulative dose of BP therapy. Methods Mandibular inferior cortical bone thickness (MICBT) was measured under the mental foramen from panoramic radiographs of subjects using BP with and without bisphosphonate related osteonecrosis of the jaws (BRONJ) and controls. Results The highest mean MICBT was observed in BRONJ subjects 6.81 (± 1.35 mm), when compared to subjects using BP 5.44 (± 1.09 mm) and controls 4.79 (± 0.85 mm; p<0.01). The mean MICBT of BRONJ subjects was significantly higher than that of subjects using BP without BRONJ. There was a correlation between MICBT and cumulative dose of zolendronate. Conclusion The MICBT on panoramic radiograph is a potentially useful tool for the detection of dimensional changes associated with BP therapy. PMID:25864820

  12. Bone stress and strain modification in diastema closure: 3D analysis using finite element method.

    PubMed

    Geramy, Allahyar; Bouserhal, Joseph; Martin, Domingo; Baghaeian, Pedram

    2015-09-01

    The aim of this study was to analyse the stress and strain distribution in the alveolar bone between two central incisors in the process of diastema closure with a constant force. A 3-dimensional computer modeling based on finite element techniques was used for this purpose. A model of an anterior segment of the mandible containing cortical bone, spongy bone, gingivae, PDL and two central incisors with a bracket in the labial surface of each tooth were designed. The von Mises stress and strain was evaluated in alveolar bone along a path of nodes defined in a cresto-apical direction in the midline between two teeth. It was observed that stress and strain of alveolar bone increased in midline with a constant force to close the diastema regardless of the type of movement in gradual steps of diastema closure, however the stress was higher in the tipping movement than the bodily so it can be suggested that a protocol of force system modification should be introduced to compensate for the stress and strain changes caused by the reduced distance to avoid the unwanted stress alteration during the diastema closure.

  13. The relationship between porosity and specific surface in human cortical bone is subject specific.

    PubMed

    Lerebours, C; Thomas, C D L; Clement, J G; Buenzli, P R; Pivonka, P

    2015-03-01

    A characteristic relationship for bone between bone volume fraction (BV/TV) and specific surface (BS/TV) has previously been proposed based on 2D histological measurements. This relationship has been suggested to be bone intrinsic, i.e., to not depend on bone type, bone site and health state. In these studies, only limited data comes from cortical bone. The aim of this paper was to investigate the relationship between BV/TV and BS/TV in human cortical bone using high-resolution micro-CT imaging and the correlations with subject-specific biometric data such as height, weight, age and sex. Images from femoral cortical bone samples of the Melbourne Femur Collection were obtained using synchrotron radiation micro-CT (SPring8, Japan). Sixteen bone samples from thirteen individuals were analysed in order to find bone volume fraction values ranging from 0.20 to 1. Finally, morphological models of the tissue microstructure were developed to help explain the relationship between BV/TV and BS/TV. Our experimental findings indicate that the BV/TV vs BS/TV relationship is subject specific rather than intrinsic. Sex and pore density were statistically correlated with the individual curves. However no correlation was found with body height, weight or age. Experimental cortical data points deviate from interpolating curves previously proposed in the literature. However, these curves are largely based on data points from trabecular bone samples. This finding challenges the universality of the curve: highly porous cortical bone is significantly different to trabecular bone of the same porosity. Finally, our morphological models suggest that changes in BV/TV within the same sample can be explained by an increase in pore area rather than in pore density. This is consistent with the proposed mechanisms of age-related endocortical bone loss. In addition, these morphological models highlight that the relationship between BV/TV and BS/TV is not linear at high BV/TV as suggested in the

  14. Modalities for Visualization of Cortical Bone Remodeling: The Past, Present, and Future.

    PubMed

    Harrison, Kimberly D; Cooper, David M L

    2015-01-01

    Bone's ability to respond to load-related phenomena and repair microdamage is achieved through the remodeling process, which renews bone by activating groups of cells known as basic multicellular units (BMUs). The products of BMUs, secondary osteons, have been extensively studied via classic two-dimensional techniques, which have provided a wealth of information on how histomorphology relates to skeletal structure and function. Remodeling is critical in maintaining healthy bone tissue; however, in osteoporotic bone, imbalanced resorption results in increased bone fragility and fracture. With increasing life expectancy, such degenerative bone diseases are a growing concern. The three-dimensional (3D) morphology of BMUs and their correlation to function, however, are not well-characterized and little is known about the specific mechanisms that initiate and regulate their activity within cortical bone. We believe a key limitation has been the lack of 3D information about BMU morphology and activity. Thus, this paper reviews methodologies for 3D investigation of cortical bone remodeling and, specifically, structures associated with BMU activity (resorption spaces) and the structures they create (secondary osteons), spanning from histology to modern ex vivo imaging modalities, culminating with the growing potential of in vivo imaging. This collection of papers focuses on the theme of "putting the 'why' back into bone architecture." Remodeling is one of two mechanisms "how" bone structure is dynamically modified and thus an improved 3D understanding of this fundamental process is crucial to ultimately understanding the "why."

  15. Some basic relationships between density values in cancellous and cortical bone.

    PubMed

    Zioupos, Peter; Cook, Richard B; Hutchinson, John R

    2008-01-01

    Density is a salient property of bone and plays a crucial role in determining the mechanical properties of both its cancellous and cortical structural forms. Density is defined in a number of ways at either the bone tissue (D(app), apparent) or the bone material level (D(mat), material). The concept of density is relatively simple, but measuring it in the context of bone is a complex issue. The third dimension of the problem is the concept of porosity, or BV/TV (ratio of bone material volume over tissue volume). Recent investigations from our laboratory have revealed an interdependence of D(app) and D(mat) in the cancellous bone of at least four different cohorts of human patients. To clarify the underlying causes of this behaviour, we produced here equivalent relationships from specimens originating from cortical and cancellous areas of the same bone. Plots of D(app) vs. D(mat) showed that D(mat) was not a monotonic function of increasing D(app), but instead showed a 'boomerang'-like pattern. By empirically dissecting the data in two regions for D(app) above and below a value equal to 1.3gcm(-3), we were able to objectively isolate the bone in trabecular and compact forms. Our findings may have implications not only for the segregation of bone in these two structural forms, but also for the mechanobiological and physiological processes that govern the regulation of compact and trabecular bone areas.

  16. Abnormalities in Cortical Bone, Trabecular Plates, and Stiffness in Postmenopausal Women Treated With Glucocorticoids

    PubMed Central

    Sutter, Stephanie; Nishiyama, Kyle K.; Kepley, Anna; Zhou, Bin; Wang, Ji; McMahon, Donald J.; Guo, X. Edward

    2014-01-01

    Context: The mechanisms by which glucocorticoids (GCs) increase skeletal fragility are not well understood. Objective: The objective of the study was to evaluate the microarchitecture, trabecular morphology, and biomechanical properties of bone in postmenopausal women treated with GCs. Design: This was a case-control study. Setting: The study was conducted at a university hospital outpatient facility. Patients: Postmenopausal women treated with oral GCs for longer than 3 months (n = 30) and age/race-matched controls (n = 60) participated in the study. Main Outcome Measures: Areal bone mineral density aBMD (BMD) by dual-energy x-ray absorptiometry (DXA) was measured. Trabecular and cortical volumetric BMD (vBMD) and microarchitecture by high-resolution peripheral computed tomography of the distal radius and tibia were also measured. Whole-bone stiffness was estimated by finite element analysis. A novel technique, individual trabecula segmentation, was used to evaluate trabecular type (as plate or rod), orientation, and connectivity. Results: DXA T-scores did not differ significantly at any site. GC subjects had significantly lower total, cortical, and trabecular vBMD and thinner cortices, fewer, thinner, more widely, and irregularly spaced trabeculae. They had fewer trabecular plates, fewer axially aligned trabeculae, and lower trabecular connectivity. Differences ranged from 4% to 65% for these trabecular measures and 5% to 17% for the cortical measures. Whole-bone stiffness was significantly lower (11%–16%) in GC subjects. Markers of bone formation (osteocalcin and amino-terminal propeptide of type I procollagen) and resorption (C-telopeptide) were lower in the GC subjects. Conclusions: Despite similar areal BMD by DXA, GC-treated women had abnormal cortical and trabecular vBMD and microarchitecture at both the radius and tibia, including fewer trabecular plates, a less axially aligned trabecular network, lower trabecular connectivity, thinner cortices, and

  17. Nonlinear hierarchical multiscale modeling of cortical bone considering its nanoscale microstructure.

    PubMed

    Ghanbari, J; Naghdabadi, R

    2009-07-22

    We have used a hierarchical multiscale modeling scheme for the analysis of cortical bone considering it as a nanocomposite. This scheme consists of definition of two boundary value problems, one for macroscale, and another for microscale. The coupling between these scales is done by using the homogenization technique. At every material point in which the constitutive model is needed, a microscale boundary value problem is defined using a macroscopic kinematical quantity and solved. Using the described scheme, we have studied elastic properties of cortical bone considering its nanoscale microstructural constituents with various mineral volume fractions. Since the microstructure of bone consists of mineral platelet with nanometer size embedded in a protein matrix, it is similar to the microstructure of soft matrix nanocomposites reinforced with hard nanostructures. Considering a representative volume element (RVE) of the microstructure of bone as the microscale problem in our hierarchical multiscale modeling scheme, the global behavior of bone is obtained under various macroscopic loading conditions. This scheme may be suitable for modeling arbitrary bone geometries subjected to a variety of loading conditions. Using the presented method, mechanical properties of cortical bone including elastic moduli and Poisson's ratios in two major directions and shear modulus is obtained for different mineral volume fractions.

  18. Optical phase analysis in drilled cortical porcine bones using digital holographic interferometry

    NASA Astrophysics Data System (ADS)

    Tavera R., César G.; De la Torre I., Manuel H.; Flores M., J. Mauricio; Luna H., Juan M.; Briones R., Manuel de J.; Mendoza S., Fernando

    2016-03-01

    A study in porcine femoral bones with and without the presence of cortical drilling is presented. An out of plane digital holographic interferometer is used to retrieve the optical phase during the controlled compression tests. These tests try to simulate physiological deformations in postmortem healthy bones and compare their mechanical response with those having a cortical hole. The cortical drilling technique is widely used in medical procedures to fix plaques and metallic frames to a bone recovering from a fracture. Several materials and drilling techniques are used for this purpose. In this work we analyze the superficial variations of the bone when different drilling diameters are used. By means of the optical phase it is possible to recover the superficial deformation of the tissue during a controlled deformation with high resolution. This information could give a better understand about the micro structural variations of the bone instead of a bulk response. As proof of principle, several tests were performed to register the modes and ranges of the displacements for compressive loads. From these tests notorious differences are observed between both groups of bones, having less structural stiffness the drilled ones as expected. However, the bone's characteristic to absorb and adjust itself due the load is also highly affected according to the number of holes. Results from different kind of samples (undrilled and drilled) are presented and discussed in this work.

  19. A Case of Giant Osteoma Developed from the Mastoid Cortical Bone

    PubMed Central

    Park, Sung Joon

    2012-01-01

    An osteoma of the temporal bone is a rare benign tumor. External auditory canal is the most common site of osteomas arising from temporal bone, and mastoid osteoma is very rare. A case of a 42-year-old female with a huge osteoma which developed from mastoid cortical bone is presented and the review of the temporal bone osteomas is discussed. The patient showed a huge and hard mass in the right mastoid area growing over a 20-year period. A temporal bone computed tomography scan demonstrated 2.3×2.3×4.3 cm sized bony tumor on surface of the right mastoid and squama. The resection of whole bony tumor with mastoid cortical bone was performed using retroauricular approach. Pathologic evaluation revealed the osteoma. The huge osteoma in the mastoid area may induce a cosmetic deformity. Early diagnosis and surgical removal of the osteoma may ensure an easy and complete treatment. The total resection of bony tumor including mastoid cortical bone is recommended to avoid recurrence. PMID:24653880

  20. Endogenous estrogen levels and calcium intakes in postmenopausal women. Relationships with cortical bone measures.

    PubMed

    Cauley, J A; Gutai, J P; Kuller, L H; LeDonne, D; Sandler, R B; Sashin, D; Powell, J G

    1988-12-02

    To examine the interactions between hormone levels and calcium with cortical bone, we have attempted to combine risk factors for the development of peak skeletal mass with factors that may be related to the maintenance of bone integrity after menopause. A total of 174 postmenopausal women participated in our study. There was little relationship found between androgen hormones and radial bone density. Estrone levels were independently related to radial bone density. Examination of the relationship of calcium intake to bone revealed a protective effect solely in women who reported high "lifetime" calcium intakes. Taking calcium and estrone together revealed an additive relationship between the two factors, in that women with high estrone and high calcium levels had significantly greater bone density than women with less calcium and/or estrone. The results suggest that a lifetime of adequate calcium intake coupled with adequate levels of serum estrogens could maximize bone density after menopause.

  1. Volumetric Cortical Bone Porosity Assessment with MR Imaging: Validation and Clinical Feasibility

    PubMed Central

    Bashoor-Zadeh, Mahdieh; Li, Cheng; Sun, Wenli; Wright, Alexander C.; Wehrli, Felix W.

    2015-01-01

    Purpose To develop a method to assess volumetric cortical bone porosity in clinically practical acquisition times by measuring the signal decay at only two echo times (TEs) as part of a single three-dimensional ultrashort TE (UTE) magnetic resonance (MR) examination. Materials and Methods The study was approved by the institutional review board and complied with HIPAA guidelines. Written informed consent was obtained from all subjects. A marker of cortical bone porosity called porosity index was defined as the ratio of UTE image intensities at a long and short TE, and the results were compared with biexponential analysis. Porosity index of midtibia cortical bone samples obtained from 16 donors was compared with ground-truth porosity by using micro–computed tomographic (CT) imaging and bone mineral density by peripheral quantitative CT scanner. Reproducibility of porosity index were tested in volunteers, and clinical feasibility was evaluated in postmenopausal women. Interparameter associations were assessed by using Pearson or Spearman correlation coefficient. Results Bone specimen porosity index was correlated with micro-CT imaging porosity (R2 = 0.79) and pore size (R2 = 0.81); age (R2 = 0.64); peripheral quantitative CT scanner density (R2 = 0.49, negatively); and pore water fraction (R2 = 0.62) and T2* (R2 = 0.64) by biexponential analysis. The reproducibility study yielded a coefficient of variation of 2.2% and intraclass correlation coefficient of 0.97. The study that involved postmenopausal women showed a wide range of porosity index (15%–38%). Conclusion A two-point MR imaging method to assess cortical bone porosity in humans was conceived and validated. This approach has the potential for clinical use to assess changes in cortical bone porosity that result from disease or in response to therapy. © RSNA, 2015 Online supplemental material is available for this article. PMID:26203710

  2. Micromechanical modeling of elastic properties of cortical bone accounting for anisotropy of dense tissue.

    PubMed

    Salguero, Laura; Saadat, Fatemeh; Sevostianov, Igor

    2014-10-17

    The paper analyzes the connection between microstructure of the osteonal cortical bone and its overall elastic properties. The existing models either neglect anisotropy of the dense tissue or simplify cortical bone microstructure (accounting for Haversian canals only). These simplifications (related mostly to insufficient mathematical apparatus) complicate quantitative analysis of the effect of microstructural changes - produced by age, microgravity, or some diseases - on the overall mechanical performance of cortical bone. The present analysis fills this gap; it accounts for anisotropy of the dense tissue and uses realistic model of the porous microstructure. The approach is based on recent results of Sevostianov et al. (2005) and Saadat et al. (2012) on inhomogeneities in a transversely-isotropic material. Bone's microstructure is modeled according to books of Martin and Burr (1989), Currey (2002), and Fung (1993) and includes four main families of pores. The calculated elastic constants for porous cortical bone are in agreement with available experimental data. The influence of each of the pore types on the overall moduli is examined. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Exploring thermal anisotropy of cortical bone using temperature measurements in drilling.

    PubMed

    Alam, Khurshid

    2016-05-12

    Bone drilling is widely used in orthopaedics for fracture treatment, reconstructive surgery and bone biopsy. Heat generation in bone drilling can cause rise in bone temperature resulting in prolonged healing time or loosening of fixation. The purpose of this study was to investigate thermal anisotropy of bone by measuring the level of temperature in bone drilling with and without cooling conditions in two anatomical directions. Drilling tests were performed on bovine cortical bone. A total of fifteen specimens were used to obtain data for statistical analysis. Temperature near the cutting zone was measured in two anatomical directions. i.e. along the longitudinal and circumferential direction. Temperature distribution was also found in the two prescribed directions. Analysis of variance (ANOVA) was used to identify significant drilling parameter affecting bone temperature. Drilling speed, feed rate and drill size were found influential parameters affecting bone temperature. Higher drilling speed, feed rate, and large drill size were found to cause elevated temperature in bone. Much lower temperature was measured in bone when cooling fluid was supplied to the drilling region. Experimental results revealed lower temperatures in the circumferential direction compared to the longitudinal direction. Thermal anisotropy for heat transport was found in the bone. This study recommends lower drilling speed and feed rate and cooling for controlling rise in bone temperature.

  4. The effect of high voltage, high frequency pulsed electric field on slain ovine cortical bone.

    PubMed

    Asgarifar, Hajarossadat; Oloyede, Adekunle; Zare, Firuz

    2014-04-01

    High power, high frequency pulsed electric fields known as pulsed power (PP) has been applied recently in biology and medicine. However, little attention has been paid to investigate the application of pulse power in musculoskeletal system and its possible effect on functional behavior and biomechanical properties of bone tissue. This paper presents the first research investigating whether or not PP can be applied safely on bone tissue as a stimuli and what will be the possible effect of these signals on the characteristics of cortical bone by comparing the mechanical properties of this type of bone pre and post expose to PP and in comparison with the control samples. A positive buck-boost converter was applied to generate adjustable high voltage, high frequency pulses (up to 500 V and 10 kHz). The functional behavior of bone in response to pulse power excitation was elucidated by applying compressive loading until failure. The stiffness, failure stress (strength) and the total fracture energy (bone toughness) were determined as a measure of the main bone characteristics. Furthermore, an ultrasonic technique was applied to determine and comprise bone elasticity before and after pulse power stimulation. The elastic property of cortical bone samples appeared to remain unchanged following exposure to pulse power excitation for all three orthogonal directions obtained from ultrasonic technique and similarly from the compression test. Nevertheless, the compressive strength and toughness of bone samples were increased when they were exposed to 66 h of high power pulsed electromagnetic field compared to the control samples. As the toughness and the strength of the cortical bone tissue are directly associated with the quality and integrity of the collagen matrix whereas its stiffness is primarily related to bone mineral content these overall results may address that although, the pulse power stimulation can influence the arrangement or the quality of the collagen network

  5. Prostaglandin E2 Increased Rat Cortical Bone Mass When Administered Immediately Following Ovariectomy

    NASA Technical Reports Server (NTRS)

    Ke, Hua Zhu; Jee, Webster S.S.; Zeng, Qing Qiang; Li, Mei; Lin, Bai Yun

    1993-01-01

    To investigate the effects of ovariectomy and the simultaneous administration of prostaglandin E2 (PGE2) on rat tibial shaft cortical bone histomorphometry, thirty-five 3 month-old female Sprague-Dawley rats were either ovariectomized (OVX), or sham ovariectomy (sham-OVX). The OVX rats were divided into three groups and treated with 0, 1 and 6 mg PGE2/kg/day for 90 days. The double fluorescent labeled undecalcified tibial shaft cross sections (proximal to the tibiofibular junction) of all the subjects were used for histomorphometry analysis. No differences in cross-sectional area and cortical bone area were found between sham-OVX and OVX controls, but OVX increased marrow area, intracortical porosity area and endocortical eroded perimeter. Periosteal and endocortical bone formation rates decreased with aging yet OVX prevented these changes. These OVX-induced increases in marrow area and endocortical eroded perimeter were prevented by 1 mg PGE2/kg/day treatment and added bone to periosteal and endocortical surfaces and to the marrow cavity. At the 6 mg/kg/day dose level, PGE2-treated OVX rats increased total tissue area, cortical bone area, marrow trabmular bone area, minimal cortical width and intracortical porosity area, and decreased marrow area compared to basal, sham-OVX and OVX controls. In addition, periosteal bone formation was elevated in the 6 mg PGE2/kg/day-treated OVX rats compared to OVX controls. Endocortical eroded perimeter increased from basal and sham-OVX control levels, but decreased from OVX control levels in the 6 mg PGE2/kg/day-treated OVX rats. Our study confirmed that ovariectomy does not cause osteopenia in tibial shaft cortical bone in rats, but it does stimulate endocortical bone resorption and enlarges marrow area. The new findings from the present study demonstrate that PGE2 prevents the OVX-induced increases in endocortical bone resorption and marrow area and adds additional bone to periosteal and endocortical surfaces and to marrow

  6. Evaluation of loading parameters for murine axial tibial loading: Stimulating cortical bone formation while reducing loading duration.

    PubMed

    Sun, David; Brodt, Michael D; Zannit, Heather M; Holguin, Nilsson; Silva, Matthew J

    2017-09-09

    Classic studies in bone mechanobiology have established the importance of loading parameters on the anabolic response. Most of these early studies were done using loading methods not currently in favor, and using non-murine species. Our objective was to re-examine the effects of several loading parameters on the response of cortical bone using the contemporary murine axial tibial compression model. We subjected tibias of 5-month old, female C57Bl/6 mice to cyclic (4 Hz) mechanical loading and examined bone formation responses using dynamic and static histomorphometry. First, using a reference protocol of 1200 cycles/day, 5 days/week for 2 weeks, we confirmed the significant influence of peak strain magnitude on periosteal mineralizing surface (Ps.MS/BS) and bone formation rate (Ps.BFR/BS) (p < 0.05, ANOVA). There was a significant induction of periosteal lamellar bone at a lower threshold of approx. -1000 μϵ and a transition from lamellar-woven bone near -2000 μϵ. In contrast, on the endocortical surface, bone formation indices did not exhibit a load magnitude-dependent response and no incidence of woven bone. Next, we found that reducing daily cycle number from 1200 to 300 to 60 did not diminish the bone formation response (p > 0.05). On the other hand, reducing the daily frequency of loading from 5 consecutive days/week to 3 alternate days/week significantly diminished the periosteal response, from a loading-induced increase in Ps.MS/BS of 38% (loaded vs. control) for 5 days/week to only 15% for 3 days/week (p < 0.05). Finally, we determined that reducing the study duration from 2 to 1 weeks of loading did not affect bone formation outcomes. In conclusion, cyclic loading to -1800 μϵ peak strain, at 4 Hz and 60 cycles/day for 5 consecutive days (1 week) induces an increase in periosteal lamellar bone formation with minimal incidence of woven bone in 5-month old C57Bl/6 female mice. Our results provide a basis for reduction of loading

  7. Internal strain gradients quantified in bone under load using high-energy X-ray scattering.

    PubMed

    Stock, S R; Yuan, Fang; Brinson, L C; Almer, J D

    2011-01-11

    High-energy synchrotron X-ray scattering (>60 keV) allows noninvasive quantification of internal strains within bone. In this proof-of-principle study, wide angle X-ray scattering maps internal strain vs position in cortical bone (murine tibia, bovine femur) under compression, specifically using the response of the mineral phase of carbonated hydroxyapatite. The technique relies on the response of the carbonated hydroxyapatite unit cells and their Debye cones (from nanocrystals correctly oriented for diffraction) to applied stress. Unstressed, the Debye cones produce circular rings on the two-dimensional X-ray detector while applied stress deforms the rings to ellipses centered on the transmitted beam. Ring ellipticity is then converted to strain via standard methods. Strain is measured repeatedly, at each specimen location for each applied stress. Experimental strains from wide angle X-ray scattering and an attached strain gage show bending of the rat tibia and agree qualitatively with results of a simplified finite element model. At their greatest, the apatite-derived strains approach 2500 με on one side of the tibia and are near zero on the other. Strains maps around a hole in the femoral bone block demonstrate the effect of the stress concentrator as loading increased and agree qualitatively with the finite element model. Experimentally, residual strains of approximately 2000 με are present initially, and strain rises to approximately 4500 με at 95 MPa applied stress (about 1000 με above the strain in the surrounding material). The experimental data suggest uneven loading which is reproduced qualitatively with finite element modeling.

  8. Internal strain gradients quantified in bone under load using high-energy X-ray scattering.

    SciTech Connect

    Stock, S.R.; Yuan, F.; Brinson, L.C.; Almer, J.D.

    2011-01-01

    High-energy synchrotron X-ray scattering (>60 keV) allows noninvasive quantification of internal strains within bone. In this proof-of-principle study, wide angle X-ray scattering maps internal strain vs position in cortical bone (murine tibia, bovine femur) under compression, specifically using the response of the mineral phase of carbonated hydroxyapatite. The technique relies on the response of the carbonated hydroxyapatite unit cells and their Debye cones (from nanocrystals correctly oriented for diffraction) to applied stress. Unstressed, the Debye cones produce circular rings on the two-dimensional X-ray detector while applied stress deforms the rings to ellipses centered on the transmitted beam. Ring ellipticity is then converted to strain via standard methods. Strain is measured repeatedly, at each specimen location for each applied stress. Experimental strains from wide angle X-ray scattering and an attached strain gage show bending of the rat tibia and agree qualitatively with results of a simplified finite element model. At their greatest, the apatite-derived strains approach 2500 {micro}{var_epsilon} on one side of the tibia and are near zero on the other. Strains maps around a hole in the femoral bone block demonstrate the effect of the stress concentrator as loading increased and agree qualitatively with the finite element model. Experimentally, residual strains of approximately 2000 {micro}{var_epsilon} are present initially, and strain rises to approximately 4500 {micro}{var_epsilon} at 95 MPa applied stress (about 1000 {micro}{var_epsilon} above the strain in the surrounding material). The experimental data suggest uneven loading which is reproduced qualitatively with finite element modeling.

  9. Bilateral patellar fractures and increased cortical bone thickness associated with long-term oral alendronate treatment in a cat

    PubMed Central

    Council, Nicola; Dyce, Jon; Drost, Wm Tod; de Brito Galvao, Joao Felipe; Rosol, Thomas J; Chew, Dennis J

    2017-01-01

    Case summary A 14-year-old cat presented with bilateral patellar fractures and radiographically thickened tibial cortices. This cat had been treated with alendronate for 8 years prior to presentation. To remove the subjectivity of the radiographic evaluation, tibial radiographs from 35 apparently healthy geriatric cats were used for comparison. Cortical and diaphyseal thickness were measured at the proximal and distal thirds of the tibia. Our cat had increased cortical bone thickness compared to that of the control cats. Relevance and novel information Treatment with bisphosphonates can lead to brittle bones and fractures after prolonged use in humans. This is the first description of fractures and cortical bone changes that may have been associated with prolonged bisphosphonate use in a cat. Radiographic measurements of cortical bone thickness may identify cats that are at increased risk for bone pathology secondary to prolonged alendronate use. PMID:28890795

  10. Calorie restriction aggravated cortical and trabecular bone architecture in ovariectomy-induced estrogen-deficient rats.

    PubMed

    Ahn, Hyejin; Seo, Dong-Hyun; Kim, Han Sung; Choue, Ryowon

    2014-08-01

    We hypothesized that calorie restriction (CR) and estrogen deficiency (ovariectomy [OVX]) would aggravate bone biomarkers and structural parameters in rats. Seven-week-old female Sprague-Dawley rats were randomized to sham-operated groups and fed either an ad libitum diet (SHAM-AL) or a CR diet (SHAM-CR); ovariectomy-operated groups were fed an ad libitum diet (OVX-AL) or a CR diet (OVX-CR). For 8 weeks, the OVX-AL and SHAM-AL groups were fed the same diet, whereas CR groups were fed a diet containing 50% fewer calories. Bone-related biomarkers and structural parameters (OC; deoxypyridinoline [DPD]; N-terminal telopeptide, NTx; architecture and mineralization; and microcomputed tomography images) were analyzed at the end of the experiment. The serum OC levels of calorie-restricted groups (SHAM-CR and OVX-CR) were significantly lower than those of the AL groups (SHAM-AL and OVX-AL) (P < .05). Urinary DPD levels of calorie-restricted and ovariectomized groups were higher than those of their counterparts (P < .05), whereas urinary NTx levels of calorie-restricted groups were higher than those of AL groups (P < .05). In regard to trabecular bone, the calorie-restricted and ovariectomized groups had lower values of bone volume to total volume, trabecular number, and bone mineral density, but higher values of trabecular separation than those of their counterparts (P < .05). Regarding cortical bone, the calorie-restricted groups had reduced values of bone volume, mean polar moment of inertia, and cortical thickness compared to the AL groups (P < .05). In conclusion, severe CR with or without OVX during the growth period in rats is equally detrimental to bone; CR has detrimental effects on trabecular and cortical bone; and estrogen deficiency only had an effect on trabecular bone. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Experimental and numerical analysis of Izod impact test of cortical bone tissue

    NASA Astrophysics Data System (ADS)

    Abdel-Wahab, A. A.; Silberschmidt, V. V.

    2012-05-01

    Bones can only sustain loads until a certain limit, beyond which they fail. Usually, the reasons for bone fracture are traumatic falls, sports injuries, and engagement in transport or industrial accidents. A proper treatment of bones and prevention of their fracture can be supported by in-depth understanding of deformation and fracture behavior of this tissue in such dynamic events. In this paper, a combination of experimental and numerical analysis was carried out in order to comprehend the fracture behavior of cortical bone tissue. Experimental tests were performed to study the transient dynamic behavior of cortical bone tissue under impact bending loading. The variability of absorbed energy for different cortex positions and notch depths was studied using Izod impact tests. Also, Extended Finite-Element Method implemented into the commercial finite-element software Abaqus was used to simulate the crack initiation and growth processes in a cantilever beam of cortical bone exposed to impact loading using the Izod loading scheme. The simulation results show a good agreement with the experimental data.

  12. Non-nuclear-initiated actions of the estrogen receptor protect cortical bone mass.

    PubMed

    Bartell, Shoshana M; Han, Li; Kim, Ha-neui; Kim, Sung Hoon; Katzenellenbogen, John A; Katzenellenbogen, Benita S; Chambliss, Ken L; Shaul, Philip W; Roberson, Paula K; Weinstein, Robert S; Jilka, Robert L; Almeida, Maria; Manolagas, Stavros C

    2013-04-01

    Extensive evidence has suggested that at least some of the effects of estrogens on bone are mediated via extranuclear estrogen receptor α signaling. However, definitive proof for this contention and the extent to which such effects may contribute to the overall protective effects of estrogens on bone maintenance have remained elusive. Here, we investigated the ability of a 17β-estradiol (E2) dendrimer conjugate (EDC), incapable of stimulating nuclear-initiated actions of estrogen receptor α, to prevent the effects of ovariectomy (OVX) on the murine skeleton. We report that EDC was as potent as an equimolar dose of E2 in preventing bone loss in the cortical compartment that represents 80% of the entire skeleton, but was ineffective on cancellous bone. In contrast, E2 was effective in both compartments. Consistent with its effect on cortical bone mass, EDC partially prevented the loss of both vertebral and femoral strength. In addition, EDC, as did E2, prevented the OVX-induced increase in osteoclastogenesis, osteoblastogenesis, and oxidative stress. Nonetheless, the OVX-induced decrease in uterine weight was unaltered by EDC but was restored by E2. These results demonstrate that the protection of cortical bone mass by estrogens is mediated, at least in part, via a mechanism that is distinct from the classic mechanism of estrogen action on reproductive organs.

  13. How Tough is Human Cortical Bone? In-Situ Measurements on Realistically Short Cracks

    SciTech Connect

    Ritchie, Robert O; Koester, K. J.; Ager III, J. W.; Ritchie, R.O.

    2008-05-10

    Bone is more difficult to break than to split. Although this is well known, and many studies exist on the behavior of long cracks in bone, there is a need for data on the orientation-dependent crack-growth resistance behavior of human cortical bone which accurately assesses its toughness at appropriate size-scales. Here we use in-situ mechanical testing in the scanning electron microscope and x-ray computed tomography to examine how physiologically-pertinent short (<600 mu m) cracks propagate in both the transverse and longitudinal orientations in cortical bone, using both crack-deflection/twist mechanics and nonlinear-elastic fracture mechanics to determine crack-resistance curves. We find that after only 500 mu m of cracking, the driving force for crack propagation was more than five times higher in the transverse (breaking) direction than in the longitudinal (splitting) direction due to major crack deflections/twists principally at cement sheathes. Indeed, our results show that the true transverse toughness of cortical bone is far higher than previously reported. However, the toughness in the longitudinal orientation, where cracks tend to follow the cement lines, is quite low at these small crack sizes; it is only when cracks become several millimeters in length that bridging mechanisms can develop leading to the (larger-crack) toughnesses generally quoted for bone.

  14. Computer modelling of bone's adaptation: the role of normal strain, shear strain and fluid flow.

    PubMed

    Tiwari, Abhishek Kumar; Prasad, Jitendra

    2017-04-01

    Bone loss is a serious health problem. In vivo studies have found that mechanical stimulation may inhibit bone loss as elevated strain in bone induces osteogenesis, i.e. new bone formation. However, the exact relationship between mechanical environment and osteogenesis is less clear. Normal strain is considered as a prime stimulus of osteogenic activity; however, there are some instances in the literature where osteogenesis is observed in the vicinity of minimal normal strain, specifically near the neutral axis of bending in long bones. It suggests that osteogenesis may also be induced by other or secondary components of mechanical environment such as shear strain or canalicular fluid flow. As it is evident from the literature, shear strain and fluid flow can be potent stimuli of osteogenesis. This study presents a computational model to investigate the roles of these stimuli in bone adaptation. The model assumes that bone formation rate is roughly proportional to the normal, shear and fluid shear strain energy density above their osteogenic thresholds. In vivo osteogenesis due to cyclic cantilever bending of a murine tibia has been simulated. The model predicts results close to experimental findings when normal strain, and shear strain or fluid shear were combined. This study also gives a new perspective on the relation between osteogenic potential of micro-level fluid shear and that of macro-level bending shear. Attempts to establish such relations among the components of mechanical environment and corresponding osteogenesis may ultimately aid in the development of effective approaches to mitigating bone loss.

  15. Effect of high-energy X-ray doses on bone elastic properties and residual strains.

    PubMed

    Singhal, A; Deymier-Black, Alix C; Almer, J D; Dunand, D C

    2011-11-01

    Bone X-ray irradiation occurs during medical treatments, sterilization of allografts, space travel and in vitro studies. High doses are known to affect the post-yield properties of bone, but their effect on the bone elastic properties is unclear. The effect of such doses on the mineral-organic interface has also not been adequately addressed. Here, the evolution of elastic properties and residual strains with increasing synchrotron X-ray dose (5-3880 kGy) is examined on bovine cortical bone. It is found that these doses affect neither the degree of nanometer-level load transfer between the hydroxyapatite (HAP) platelets and the collagen up to stresses of -60 MPa nor the microscopic modulus of collagen fibrils (both measured by synchrotron X-ray scattering during repeated in situ loading and unloading). However, the residual elastic strains in the HAP phase decrease markedly with increased irradiation, indicating damage at the HAP-collagen interface. The HAP residual strain also decreases after repeated loading/unloading cycles. These observations can be explained by temporary de-bonding at the HAP/collagen interface (thus reducing the residual strain), followed by rapid re-bonding (so that load transfer capability is not affected). Copyright © 2011 Elsevier Ltd. All rights reserved.

  16. The effects of immobilization on cortical bone in monkeys (M. nemestrina)

    NASA Technical Reports Server (NTRS)

    Niklowitz, W. J.; Bunch, T. E.; Young, D. R.

    1983-01-01

    Rhesus and pigtail monkeys were restrained for up to seven months in a hypogravic-hypodynamic environment for the purpose of studying the osteoporotic process and its reversibility, particularly in relation to humans. In vivo bending, radiography and tomography are among the techniques that were used. Bone deterioration within one month was detectable only in histological preparation, where resorption and subsequent cavity formation were demonstrated in addition to demineralization of the remaining hard tissue. Norland bone mineral analysis showed the greatest bone demineralization in the proximal tibia (23 percent to 31 percent after six months restraint), recovery did not even necessarily occur after 15 months. The largest bone stiffness decrease was 36 to 40 percent after a six months restraint; normal bending properties but not mineral content were restored after 8-1/2 months. Contrary to earlier studies, it is concluded that bone recovery, though a lengthy process, is possible: cortical bone in the tibia required 40 months.

  17. Mesenchymal stem cells from cortical bone demonstrate increased clonal incidence, potency, and developmental capacity compared to their bone marrow-derived counterparts.

    PubMed

    Blashki, Daniel; Murphy, Matthew B; Ferrari, Mauro; Simmons, Paul J; Tasciotti, Ennio

    2016-01-01

    In this study, we show that matrix dense cortical bone is the more potent compartment of bone than bone marrow as a stromal source for mesenchymal stem cells as isolated from adult rats. Lineage-depleted cortical bone-mesenchymal stem cells demonstrated >150-fold enrichment of colony forming unit-fibroblasts per cell incidence. compared to lineage-depleted bone marrow-mesenchymal stem cells, corresponding to a 70-fold increase in absolute recovered colony forming unit-fibroblasts. The composite phenotype Lin(-)/CD45(-)/CD31(-)/VLA-1(+)/Thy-1(+) enriched for clonogenic mesenchymal stem cells solely from cortical bone-derived cells from which 70% of clones spontaneously differentiated into all lineages of bone, cartilage, and adipose. Both populations generated vascularized bone tissue within subcutaneous implanted collagen scaffolds; however, cortical bone-derived cells formed significantly more osteoid than bone marrow counterparts, quantified by histology. The data demonstrate that our isolation protocol identifies and validates mesenchymal stem cells with superior clonal, proliferative, and developmental potential from cortical bone compared to the bone marrow niche although marrow persists as the typical source for mesenchymal stem cells both in the literature and current pre-clinical therapies.

  18. Anisotropic mode-dependent damage of cortical bone using the extended finite element method (XFEM).

    PubMed

    Feerick, Emer M; Liu, Xiangyi Cheryl; McGarry, Patrick

    2013-04-01

    Anisotropic damage initiation criteria were developed for extended finite element method (XFEM) prediction of crack initiation and propagation in cortical bone. This anisotropic damage model was shown to accurately predict the dependence of crack propagation patterns and fracture toughness on mode mixity and on osteon orientations, as observed experimentally. Four initiation criteria were developed to define crack trajectories relative to osteon orientations and max principal stress for single and mixed mode fracture. Alternate failure strengths for tensile and compressive loading were defined to simulate the asymmetric failure of cortical bone. The dependence of cortical bone elasticity and failure properties on osteon orientation is analogous to the dependence of composite properties on fibre orientation. Hence, three of the criteria developed in the present study were based upon the Hashin damage criteria. The fourth criterion developed was defined in terms of the max principal stress. This criterion initiated off axis crack growth perpendicular to the direction of the max principal stress. The unique set of parameters calibrated accurately predicted; (i) the relationship between fracture energy and osteon alignment, (ii) the alternate crack patterns for both varying osteon orientations and loading angle. Application of the developed anisotropic damage models to cortical bone screw pullout highlights the potential application for orthopaedic device design evaluation.

  19. Ultrasonic wave velocity measurement in small polymeric and cortical bone specimens

    NASA Technical Reports Server (NTRS)

    Kohles, S. S.; Bowers, J. R.; Vailas, A. C.; Vanderby, R. Jr

    1997-01-01

    A system was refined for the determination of the bulk ultrasonic wave propagation velocity in small cortical bone specimens. Longitudinal and shear wave propagations were measured using ceramic, piezoelectric 20 and 5 MHz transducers, respectively. Results of the pulse transmission technique were refined via the measurement of the system delay time. The precision and accuracy of the system were quantified using small specimens of polyoxymethylene, polystyrene-butadiene, and high-density polyethylene. These polymeric materials had known acoustic properties, similarity of propagation velocities to cortical bone, and minimal sample inhomogeneity. Dependence of longitudinal and transverse specimen dimensions upon propagation times was quantified. To confirm the consistency of longitudinal wave propagation in small cortical bone specimens (< 1.0 mm), cut-down specimens were prepared from a normal rat femur. Finally, cortical samples were prepared from each of ten normal rat femora, and Young's moduli (Eii), shear moduli (Gij), and Poisson ratios (Vij) were measured. For all specimens (bone, polyoxymethylene, polystyrene-butadiene, and high-density polyethylene), strong linear correlations (R2 > 0.997) were maintained between propagation time and distance throughout the size ranges down to less than 0.4 mm. Results for polyoxymethylene, polystyrene-butadiene, and high-density polyethylene were accurate to within 5 percent of reported literature values. Measurement repeatability (precision) improved with an increase in the wave transmission distance (propagating dimension). No statistically significant effect due to the transverse dimension was detected.

  20. Ultrasonic wave velocity measurement in small polymeric and cortical bone specimens.

    PubMed

    Kohles, S S; Bowers, J R; Vailas, A C; Vanderby, R

    1997-08-01

    A system was refined for the determination of the bulk ultrasonic wave propagation velocity in small cortical bone specimens. Longitudinal and shear wave propagations were measured using ceramic, piezoelectric 20 and 5 MHz transducers, respectively. Results of the pulse transmission technique were refined via the measurement of the system delay time. The precision and accuracy of the system were quantified using small specimens of polyoxymethylene, polystyrene-butadiene, and high-density polyethylene. These polymeric materials had known acoustic properties, similarity of propagation velocities to cortical bone, and minimal sample inhomogeneity. Dependence of longitudinal and transverse specimen dimensions upon propagation times was quantified. To confirm the consistency of longitudinal wave propagation in small cortical bone specimens (< 1.0 mm), cut-down specimens were prepared from a normal rat femur. Finally, cortical samples were prepared from each of ten normal rat femora, and Young's moduli (Eii), shear moduli (Gij), and Poisson ratios (Vij) were measured. For all specimens (bone, polyoxymethylene, polystyrene-butadiene, and high-density polyethylene), strong linear correlations (R2 > 0.997) were maintained between propagation time and distance throughout the size ranges down to less than 0.4 mm. Results for polyoxymethylene, polystyrene-butadiene, and high-density polyethylene were accurate to within 5 percent of reported literature values. Measurement repeatability (precision) improved with an increase in the wave transmission distance (propagating dimension). No statistically significant effect due to the transverse dimension was detected.

  1. Genetic algorithms-based inversion of multimode guided waves for cortical bone characterization

    NASA Astrophysics Data System (ADS)

    Bochud, N.; Vallet, Q.; Bala, Y.; Follet, H.; Minonzio, J.-G.; Laugier, P.

    2016-10-01

    Recent progress in quantitative ultrasound has exploited the multimode waveguide response of long bones. Measurements of the guided modes, along with suitable waveguide modeling, have the potential to infer strength-related factors such as stiffness (mainly determined by cortical porosity) and cortical thickness. However, the development of such model-based approaches is challenging, in particular because of the multiparametric nature of the inverse problem. Current estimation methods in the bone field rely on a number of assumptions for pairing the incomplete experimental data with the theoretical guided modes (e.g. semi-automatic selection and classification of the data). The availability of an alternative inversion scheme that is user-independent is highly desirable. Thus, this paper introduces an efficient inversion method based on genetic algorithms using multimode guided waves, in which the mode-order is kept blind. Prior to its evaluation on bone, our proposal is validated using laboratory-controlled measurements on isotropic plates and bone-mimicking phantoms. The results show that the model parameters (i.e. cortical thickness and porosity) estimated from measurements on a few ex vivo human radii are in good agreement with the reference values derived from x-ray micro-computed tomography. Further, the cortical thickness estimated from in vivo measurements at the third from the distal end of the radius is in good agreement with the values delivered by site-matched high-resolution x-ray peripheral computed tomography.

  2. Influence of cortical endplate on speed of sound in bovine femoral trabecular bone in vitro.

    PubMed

    Hwang, Kyo Seung; Lee, Kang Il

    2012-12-01

    Speed of sound (SOS) was measured in 14 bovine femoral trabecular bone samples with and without the cortical endplates with various thicknesses of 1.00, 1.31, 1.47, 1.75, and 2.00 mm. The presence of the cortical endplates resulted in an increase in the mean SOS of 16 m/s (+0.9%) to 91 m/s (+5.3%). The mean SOS measured in the samples with and without the cortical endplates exhibited similar significant correlations with apparent bone density (r = 0.86-0.91). All the SOS measurements were also found to be highly correlated with each other (r = 0.89-0.99).

  3. [ANATOMICAL PLATE COMBINED WITH CORTICAL BONE PLATE ALLOGRAFTS FOR TREATMENT OF COMMINUTED FRACTURES OF FEMORAL CONDYLES].

    PubMed

    Guo, Zhimin; Gong, Xingxing; Li, Yanwei; Qiu, Xiaochun; Zhang, Meng; Shangguan, Tiancheng; Ao, Qingfang; Liu, Qiang

    2015-01-01

    To summarize the effectiveness of anatomical plate combined with cortical bone plate allografts in the treatment of comminuted fractures of the femoral condyles. Between January 2008 and December 2012, 18 patients with comminuted fractures of the femoral condyles were treated, including 13 males and 5 females with an average age of 45 years (range, 23-65 years). Fractures were caused by traffic accident in 11 cases, by falling from height in 4 cases, and by the other in 3 cases. The locations were the left side in 7 cases and the right side in 11 cases. Of 18 fractures, 12 were open fractures and 6 were closed fractures. The mean time from injury to operation was 6 days (range, 4-15 days). The fixation was performed by anatomical plate combined with cortical bone plate allografts, and autograft bone or allogeneic bone grafting were used. Superficial local skin necrosis occurred in 1 case, and was cured after skin graft, and other incisions achieved primary healing. All patients were followed up 12-36 months (mean, 23 months). X-ray films showed that bone union was achieved within 3-12 months (5.6 months on average). No related complication occurred, such as fixation loosening, refracture, infection, or immunological rejection. According to Merchan et al. criteria for knee joint function evaluation, the results were excellent in 7 cases, good in 9 cases, fair in 1 case, and poor in 1 case at last follow-up; the excellent and good rate was 88.9%. Anatomical plate combined with cortical bone plate allograft fixation is a good method to treat comminuted fractures of the femoral condyles. This method can effectively achieve complete cortical bone on the inside of the femur as well as provide rigid fixation.

  4. Physical activity when young provides lifelong benefits to cortical bone size and strength in men

    PubMed Central

    Warden, Stuart J.; Mantila Roosa, Sara M.; Kersh, Mariana E.; Hurd, Andrea L.; Fleisig, Glenn S.; Pandy, Marcus G.; Fuchs, Robyn K.

    2014-01-01

    The skeleton shows greatest plasticity to physical activity-related mechanical loads during youth but is more at risk for failure during aging. Do the skeletal benefits of physical activity during youth persist with aging? To address this question, we used a uniquely controlled cross-sectional study design in which we compared the throwing-to-nonthrowing arm differences in humeral diaphysis bone properties in professional baseball players at different stages of their careers (n = 103) with dominant-to-nondominant arm differences in controls (n = 94). Throwing-related physical activity introduced extreme loading to the humeral diaphysis and nearly doubled its strength. Once throwing activities ceased, the cortical bone mass, area, and thickness benefits of physical activity during youth were gradually lost because of greater medullary expansion and cortical trabecularization. However, half of the bone size (total cross-sectional area) and one-third of the bone strength (polar moment of inertia) benefits of throwing-related physical activity during youth were maintained lifelong. In players who continued throwing during aging, some cortical bone mass and more strength benefits of the physical activity during youth were maintained as a result of less medullary expansion and cortical trabecularization. These data indicate that the old adage of “use it or lose it” is not entirely applicable to the skeleton and that physical activity during youth should be encouraged for lifelong bone health, with the focus being optimization of bone size and strength rather than the current paradigm of increasing mass. The data also indicate that physical activity should be encouraged during aging to reduce skeletal structural decay. PMID:24706816

  5. PROGRESSIVE MECHANICAL BEHAVIOR OF HUMAN CORTICAL BONE IN TENSION FOR TWO AGE GROUPS

    PubMed Central

    Nyman, Jeffry S.; Roy, Anuradha; Reyes, Michael J.; Wang, Xiaodu

    2007-01-01

    The capacity of bone for post-yield energy dissipation decreases with age. To gain information on the cause of such changes, we examined the mechanical behavior of human cadaveric bone as a function of progressive deformation. In this study, tensile specimens from tibiae of 9 middle aged and 8 elderly donors were loaded till failure in an incremental and cyclic (load-dwell-unload-dwell-reload) scheme. The elastic modulus, maximum stress, permanent strain, stress relaxation, viscoelastic time constant, plastic strain energy, elastic release strain energy, and hysteresis energy were determined at incremental strains of each loading cycle. Experimental results showed that elderly bone failed at much lower strains compared to middle aged bone, but little age-related differences were observed in the mechanical behavior of bone until the premature failure of elderly bone. Energy dissipation and permanent strain appeared to linearly increase with increasing strain, while non-linear changes occurred in the modulus loss and stress relaxation/time constant with increasing strain. Such changes suggest that two distinct stages may exist in the progressive deformation of bone. In Stage I, rapid damage accumulation and increased involvement of collagen in load bearing appeared to dominate the mechanical behavior of bone with limited energy dissipation (<20% of total energy dissipated), whereas Stage II is dominated by continuous plastic deformation, accompanied by major energy dissipation through all three pathways till failure. This study suggests that damaging mechanisms in bone vary with deformation and age affects the post-yield mechanisms causing a significant decline in the capacity of aged bone to dissipate energy. PMID:18437693

  6. GBR and autogenous cortical bone particulate by bone scraper for alveolar ridge augmentation: a 2-case report.

    PubMed

    Trombelli, Leonardo; Farina, Roberto; Marzola, Andrea; Itro, Angelo; Calura, Giorgio

    2008-01-01

    Scientific literature describes autogenous bone as the gold standard among graft materials for alveolar reconstructive procedures. Alveolar ridge augmentation has been clinically achieved with different forms of autogenous bone, including autogenous cortical bone particulate (ACBP). However, few histologic studies demonstrating the biologic potential and healing dynamics following the use of ACBP are currently available. This case report presents 2 patients in whom atrophic edentulous alveolar crests were submitted to a vertical/lateral ridge augmentation prior to implant placement. The technique was performed through the use of a titanium-reinforced expanded polytetrafluoroethylene (e-PTFE) membrane with an ACBP graft obtained from the retromolar region with a specially designed bone scraper. Bone biopsy specimens were harvested at 9 months after graft placement. Analysis of the reconstructed bone revealed bone with a lamellar quality characterized by a mature osteonic structure. Sparse particles of grafted bone were evident in direct contact with the regenerated bone. Marrow spaces showed a normal stromal component with limited grafted particles.

  7. Characterization of the effects of x-ray irradiation on the hierarchical structure and mechanical properties of human cortical bone

    SciTech Connect

    Barth, Holly; Zimmermann, Elizabeth; Schaible, Eric; Tang, Simon; Alliston, Tamara; Ritchie, Robert

    2011-08-19

    Bone comprises a complex structure of primarily collagen, hydroxyapatite and water, where each hierarchical structural level contributes to its strength, ductility and toughness. These properties, however, are degraded by irradiation, arising from medical therapy or bone-allograft sterilization. We provide here a mechanistic framework for how irradiation affects the nature and properties of human cortical bone over a range of characteristic (nano to macro) length-scales, following x-­ray exposures up to 630 kGy. Macroscopically, bone strength, ductility and fracture resistance are seen to be progressively degraded with increasing irradiation levels. At the micron-­scale, fracture properties, evaluated using in-situ scanning electron microscopy and synchrotron x-ray computed micro-tomography, provide mechanistic information on how cracks interact with the bone-matrix structure. At sub-micron scales, strength properties are evaluated with in-situ tensile tests in the synchrotron using small-/wide-angle x-ray scattering/diffraction, where strains are simultaneously measured in the macroscopic tissue, collagen fibrils and mineral. Compared to healthy bone, results show that the fibrillar strain is decreased by ~40% following 70 kGy exposures, consistent with significant stiffening and degradation of the collagen. We attribute the irradiation-­induced deterioration in mechanical properties to mechanisms at multiple length-scales, including changes in crack paths at micron-­scales, loss of plasticity from suppressed fibrillar sliding at sub-­micron scales, and the loss and damage of collagen at the nano-­scales, the latter being assessed using Raman and Fourier-Transform-Infrared spectroscopy and a fluorometric assay.

  8. Characterization of the effects of x-ray irradiation on the hierarchical structure and mechanical properties of human cortical bone.

    PubMed

    Barth, Holly D; Zimmermann, Elizabeth A; Schaible, Eric; Tang, Simon Y; Alliston, Tamara; Ritchie, Robert O

    2011-12-01

    Bone comprises a complex structure of primarily collagen, hydroxyapatite and water, where each hierarchical structural level contributes to its strength, ductility and toughness. These properties, however, are degraded by irradiation, arising from medical therapy or bone-allograft sterilization. We provide here a mechanistic framework for how irradiation affects the nature and properties of human cortical bone over a range of characteristic (nano to macro) length-scales, following x-ray exposures up to 630 kGy. Macroscopically, bone strength, ductility and fracture resistance are seen to be progressively degraded with increasing irradiation levels. At the micron-scale, fracture properties, evaluated using insitu scanning electron microscopy and synchrotron x-ray computed micro-tomography, provide mechanistic information on how cracks interact with the bone-matrix structure. At sub-micron scales, strength properties are evaluated with insitu tensile tests in the synchrotron using small-/wide-angle x-ray scattering/diffraction, where strains are simultaneously measured in the macroscopic tissue, collagen fibrils and mineral. Compared to healthy bone, results show that the fibrillar strain is decreased by ∼40% following 70 kGy exposures, consistent with significant stiffening and degradation of the collagen. We attribute the irradiation-induced deterioration in mechanical properties to mechanisms at multiple length-scales, including changes in crack paths at micron-scales, loss of plasticity from suppressed fibrillar sliding at sub-micron scales, and the loss and damage of collagen at the nano-scales, the latter being assessed using Raman and Fourier Transform Infrared spectroscopy and a fluorometric assay.

  9. Characterization of the effects of x-ray irradiation on the hierarchical structure and mechanical properties of human cortical bone

    PubMed Central

    Barth, Holly D.; Zimmermann, Elizabeth A.; Schaible, Eric; Tang, Simon Y.; Alliston, Tamara; Ritchie, Robert O.

    2012-01-01

    Bone comprises a complex structure of primarily collagen, hydroxyapatite and water, where each hierarchical structural level contributes to its strength, ductility and toughness. These properties, however, are degraded by irradiation, arising from medical therapy or bone-allograft sterilization. We provide here a mechanistic framework for how irradiation affects the nature and properties of human cortical bone over a range of characteristic (nano to macro) length-scales, following x-ray exposures up to 630 kGy. Macroscopically, bone strength, ductility and fracture resistance are seen to be progressively degraded with increasing irradiation levels. At the micron-scale, fracture properties, evaluated using insitu scanning electron microscopy and synchrotron x-ray computed micro-tomography, provide mechanistic information on how cracks interact with the bone-matrix structure. At sub-micron scales, strength properties are evaluated with insitu tensile tests in the synchrotron using small-/wide-angle x-ray scattering/diffraction, where strains are simultaneously measured in the macroscopic tissue, collagen fibrils and mineral. Compared to healthy bone, results show that the fibrillar strain is decreased by ~40% following 70 kGy exposures, consistent with significant stiffening and degradation of the collagen. We attribute the irradiation-induced deterioration in mechanical properties to mechanisms at multiple length-scales, including changes in crack paths at micron-scales, loss of plasticity from suppressed fibrillar sliding at sub-micron scales, and the loss and damage of collagen at the nano-scales, the latter being assessed using Raman and Fourier Transform Infrared spectroscopy and a fluorometric assay. PMID:21885114

  10. Extra-nuclear effects of estrogen on cortical bone in males require ERαAF-1

    PubMed Central

    Wu, J; Gustafsson, K L; Windahl, S H; Kim, S H; Katzenellenbogen, J A; Ohlsson, C; Lagerquist, M K

    2017-01-01

    Estradiol (E2) signaling via estrogen receptor alpha (ERα) is important for the male skeleton as demonstrated by ERα inactivation in both mice and man. ERα mediates estrogenic effects not only by translocating to the nucleus and affecting gene transcription but also by extra-nuclear actions e.g., triggering cytoplasmic signaling cascades. ERα contains various domains, and the role of activation function 1 (ERαAF-1) is known to be tissue specific. The aim of this study was to determine the importance of extra-nuclear estrogen effects for the skeleton in males and to determine the role of ERαAF-1 for mediating these effects. Five-month-old male wild-type (WT) and ERαAF-1-inactivated (ERαAF-10) mice were orchidectomized and treated with equimolar doses of 17β-estradiol (E2) or an estrogen dendrimer conjugate (EDC), which is incapable of entering the nucleus and thereby only initiates extra-nuclear ER actions or their corresponding vehicles for 3.5 weeks. As expected, E2 treatment increased cortical thickness and trabecular bone volume per total volume (BV/TV) in WT males. EDC treatment increased cortical thickness in WT males, whereas no effect was detected in trabecular bone. In ERαAF-10 males, E2 treatment increased cortical thickness, but did not affect trabecular bone. Interestingly, the effect of EDC on cortical bone was abolished in ERαAF-10 mice. In conclusion, extra-nuclear estrogen signaling affects cortical bone mass in males, and this effect is dependent on a functional ERαAF-1. Increased knowledge regarding estrogen signaling mechanisms in the regulation of the male skeleton may aid the development of new treatment options for male osteoporosis. PMID:28057769

  11. Extra-nuclear effects of estrogen on cortical bone in males require ERαAF-1.

    PubMed

    Farman, H H; Wu, J; Gustafsson, K L; Windahl, S H; Kim, S H; Katzenellenbogen, J A; Ohlsson, C; Lagerquist, M K

    2017-02-01

    Estradiol (E2) signaling via estrogen receptor alpha (ERα) is important for the male skeleton as demonstrated by ERα inactivation in both mice and man. ERα mediates estrogenic effects not only by translocating to the nucleus and affecting gene transcription but also by extra-nuclear actions e.g., triggering cytoplasmic signaling cascades. ERα contains various domains, and the role of activation function 1 (ERαAF-1) is known to be tissue specific. The aim of this study was to determine the importance of extra-nuclear estrogen effects for the skeleton in males and to determine the role of ERαAF-1 for mediating these effects. Five-month-old male wild-type (WT) and ERαAF-1-inactivated (ERαAF-1(0)) mice were orchidectomized and treated with equimolar doses of 17β-estradiol (E2) or an estrogen dendrimer conjugate (EDC), which is incapable of entering the nucleus and thereby only initiates extra-nuclear ER actions or their corresponding vehicles for 3.5 weeks. As expected, E2 treatment increased cortical thickness and trabecular bone volume per total volume (BV/TV) in WT males. EDC treatment increased cortical thickness in WT males, whereas no effect was detected in trabecular bone. In ERαAF-1(0) males, E2 treatment increased cortical thickness, but did not affect trabecular bone. Interestingly, the effect of EDC on cortical bone was abolished in ERαAF-1(0) mice. In conclusion, extra-nuclear estrogen signaling affects cortical bone mass in males, and this effect is dependent on a functional ERαAF-1. Increased knowledge regarding estrogen signaling mechanisms in the regulation of the male skeleton may aid the development of new treatment options for male osteoporosis.

  12. In situ observation of fracture behavior of canine cortical bone under bending.

    PubMed

    Lin, Zilan X; Xu, Zhi-Hui; An, Yuehuei H; Li, Xiaodong

    2016-05-01

    Cortical bone provides many important body functions and maintains the rigidness and elasticity of bone. A common failure mode for bone structure is fracture under a bending force. In the current study, the fracture behavior of canine cortical bone under three-point bending was observed in situ using an atomic force microscope (AFM), a scanning electron microscope (SEM), and an optical microscope to examine the fracture process in detail. Nanoindentation was carried out to determine the elastic modulus and hardness of different building blocks of the canine cortical bone. The results have shown that the special structure of Haversian systems has significant effects on directing crack propagation. Although Haversian systems contain previously believed weak points, and micro-cracks initiate within Haversian systems, our findings have demonstrated that macro-cracks typically form around the boundaries of Haversian systems, i.e. the cement lines. Micro-cracks that developed inside Haversian systems have the functions of absorbing and dissipating energy and slow down on expanding when interstitial tissue cannot hold any more pressure, then plastic deformation and fracture occur.

  13. Femoral cortical index: an indicator of poor bone quality in patient with hip fracture.

    PubMed

    Feola, M; Rao, C; Tempesta, V; Gasbarra, E; Tarantino, U

    2015-10-01

    Osteoporosis is a common disease in elderly, characterized by poor bone quality as a result of alterations affecting trabecular bone. However, recent studies have described also an important role of alterations of cortical bone in the physiopathology of osteoporosis. Although dual-energy X-ray absorptiometry (DXA) is a valid method to assess bone mineral density, in the presence of comorbidities real bone fragility is unable to be evaluated. The number of hip fractures is rising, especially in people over 85 years old. The aim is to evaluate an alternative method so that it can indicate fracture risk, independent of bone mineral density (BMD). Femoral cortical index (FCI) assesses cortical bone stock using femur X-ray. A retrospective study has been conducted on 152 patients with hip fragility fractures. FCI has been calculated on fractured femur and on the opposite side. The presence of comorbidities, osteoporosis risk factors, vitamin D levels, and BMD have been analyzed for each patient. Average values of FCI have been 0.42 for fractured femurs and 0.48 at the opposite side with a statistically significant difference (p = 0.002). Patients with severe hypovitaminosis D had a minor FCI compared to those with moderate deficiency (0.41 vs. 0.46, p < 0.011). 42 patients (27.6%) with osteopenic or normal BMD have presented low values of FCI. A significant correlation among low values of FCI, comorbidities, severe hypovitaminosis D. and BMD in patients with hip fractures has been found. FCI could be a useful tool to evaluate bone fragility and to predict fracture risk even in the normal and osteopenic BMD patients.

  14. Suppression of Autophagy in Osteocytes Does Not Modify the Adverse Effects of Glucocorticoids on Cortical Bone

    PubMed Central

    Piemontese, Marilina; Onal, Melda; Xiong, Jinhu; Wang, Yiying; Almeida, Maria; Thostenson, Jeff D.; Weinstein, Robert S.; Manolagas, Stavros C.; O’Brien, Charles A.

    2015-01-01

    Glucocorticoid excess decreases bone mass and strength in part by acting directly on osteoblasts and osteocytes, but the mechanisms remain unclear. Macroautophagy (herein referred to as autophagy) is a lysosome-based recycling pathway that promotes the turnover of intracellular components and can promote cell function and survival under stressful conditions. Recent studies have shown that glucocorticoids stimulate autophagy in osteocytes, suggesting that autophagy may oppose the negative actions of glucocorticoids on this cell type. To address this possibility, we compared the impact of prednisolone administration on the skeletons of adult mice in which autophagy was suppressed in osteocytes, via deletion of Atg7 with a Dmp1-Cre transgene, to their control littermates. In control mice, prednisolone increased autophagic flux in osteocyte-enriched bone as measured by LC3 conversion, but this change did not occur in the mice lacking Atg7 in osteocytes. Nonetheless, prednisolone reduced femoral cortical thickness, increased cortical porosity, and reduced bone strength to similar extents in mice with and without autophagy in osteocytes. Prednisolone also suppressed osteoblast number and bone formation in the cancellous bone of control mice. As shown previously, Atg7 deletion in osteocytes reduced osteoblast number and bone formation in cancellous bone, but these parameters were not further reduced by prednisolone administration. In cortical bone, prednisolone elevated osteoclast number to a similar extent in both genotypes. Taken together, these results demonstrate that although glucocorticoids stimulate autophagy in osteocytes, suppression of autophagy in this cell type does not worsen the negative impact of glucocorticoids on the skeleton. PMID:25700544

  15. Suppression of autophagy in osteocytes does not modify the adverse effects of glucocorticoids on cortical bone.

    PubMed

    Piemontese, Marilina; Onal, Melda; Xiong, Jinhu; Wang, Yiying; Almeida, Maria; Thostenson, Jeff D; Weinstein, Robert S; Manolagas, Stavros C; O'Brien, Charles A

    2015-06-01

    Glucocorticoid excess decreases bone mass and strength in part by acting directly on osteoblasts and osteocytes, but the mechanisms remain unclear. Macroautophagy (herein referred to as autophagy) is a lysosome-based recycling pathway that promotes the turnover of intracellular components and can promote cell function and survival under stressful conditions. Recent studies have shown that glucocorticoids stimulate autophagy in osteocytes, suggesting that autophagy may oppose the negative actions of glucocorticoids on this cell type. To address this possibility, we compared the impact of prednisolone administration on the skeletons of adult mice in which autophagy was suppressed in osteocytes, via deletion of Atg7 with a Dmp1-Cre transgene, to their control littermates. In control mice, prednisolone increased autophagic flux in osteocyte-enriched bone as measured by LC3 conversion, but this change did not occur in the mice lacking Atg7 in osteocytes. Nonetheless, prednisolone reduced femoral cortical thickness, increased cortical porosity, and reduced bone strength to similar extents in mice with and without autophagy in osteocytes. Prednisolone also suppressed osteoblast number and bone formation in the cancellous bone of control mice. As shown previously, Atg7 deletion in osteocytes reduced osteoblast number and bone formation in cancellous bone, but these parameters were not further reduced by prednisolone administration. In cortical bone, prednisolone elevated osteoclast number to a similar extent in both genotypes. Taken together, these results demonstrate that although glucocorticoids stimulate autophagy in osteocytes, suppression of autophagy in this cell type does not worsen the negative impact of glucocorticoids on the skeleton. Published by Elsevier Inc.

  16. Measurement of Crestal Cortical Bone Thickness at Implant Site: A Cone Beam Computed Tomography Study.

    PubMed

    Gupta, Ajai; Rathee, Suprabha; Agarwal, Jaihans; Pachar, Renu B

    2017-09-01

    Dental implants have emerged as a new treatment modality for the majority of patients complaining of missing teeth. Bone quantity and bone quality are among various factors which ensure the longevity of dental implant in the patient's mouth. The assessment of cortical bone thickness of the outer layer and the cancellous bone density by cone beam computed tomography (CBCT) has proved beneficial for the patient. This study aimed at presurgical measurement of crestal bone thickness at various implant sites using CBCT images. This study was conducted in the Department of Prosthodontics in the year 2015. It included 218 patients who wanted to replace missing teeth. Patients were subjected to CBCT scan using NewTom CBCT machine operating at 120 kVp and 5 mA with a resolution of 0.1 × 0.1 × 0.1 mm(3). New Net Technologies (NNT) software with a slice thickness of 0.1 mm was used in this study. A total of 780 implant sites were identified on images of 218 patients. In all patients, the measurement of crestal bone thickness in the region of implant site was performed with NNT software. The buccolingual measurement of crestal bone was done in cross sections obtained after CBCT Results: Out of 218 patients, males were 110 and females were 108. The difference between gender was nonsignificant (p > 0.05). Out of 780 implant sites, 370 were in the maxilla and 410 were in mandible. The difference was nonsignificant (p > 0.05). Out of 780 implant sites, 210 were in anterior maxilla and 160 were in the posterior maxilla. Totally, 235 sites were in anterior mandible and 175 were in the posterior mandible. The distribution was nonsignificant (p = 0.15). The mean crestal bone thickness in anterior maxilla was 0.82 mm, in posterior maxilla was 0.76 mm, in anterior mandible was 1.08 mm, and in posterior mandible was 1.18 mm. The difference among regions was significant (p = 0.01). The highest thickness of cortical bone was observed in posterior mandible followed by anterior mandible

  17. Time Related Changes of Mineral and Collagen and Their Roles in Cortical Bone Mechanics of Ovariectomized Rabbits

    PubMed Central

    Xu, Chao; Wu, Zi-Xiang; Zhang, Yang; Feng, Ya-Fei; Yan, Ya-Bo; Lei, Wei

    2015-01-01

    As cortical bone has a hierarchical structure, the macroscopic bone strength may be affected by the alterations of mineral crystal and collagen, which are main components of cortical bone. Limited studies focused on the time related alterations of these two components in osteoporosis, and their contributions to bone mechanics at tissue level and whole-bone level. Therefore, the purpose of this study was to elucidate the time related changes of mineral and collagen in cortical bone of ovariectomized (OVX) rabbits, and to relate these changes to cortical bone nanomechanics and macromechanics. 40 Rabbits (7-month-old) were randomly allocated into two groups (OVX and sham). OVX group received bilateral ovariectomy operation. Sham group received sham-OVX operation. Cortical bone quality of five rabbits in each group were assessed by DXA, μCT, nanoindentation, Fourier transform infrared (FTIR) spectroscopy and biomechanical tests (3-point bending of femoral midshaft) at pre-OVX, 4, 6, and 8 weeks after OVX. As time increased from pre-OVX to 8 weeks, the mineral to matrix ratio decreased with time, while both collagen crosslink ratio and crystallinity increased with time in OVX group. Elastic modulus and hardness measured by nanoindentation, whole-bone strength measured by biomechanical tests all decreased in OVX group with time. Bone material properties measured by FTIR correlated well with nano or whole-bone level mechanics. However, bone mineral density (BMD), structure, tissue-level and whole-bone mechanical properties did not change with age in sham group. Our study demonstrated that OVX could affect the tissue-level mechanics and bone strength of cortical bone. And this influence was attributed to the time related alterations of mineral and collagen properties, which may help us to design earlier interventions and more effective treatment strategies on osteoporosis. PMID:26046792

  18. Early cellular responses in cortical bone healing around unloaded titanium implants: an animal study.

    PubMed

    Slaets, Elke; Carmeliet, Geert; Naert, Ignace; Duyck, Joke

    2006-06-01

    A clear understanding of the early cellular events leading to osseointegration of implants is currently lacking. To gain better insight, titanium implants were inserted in a rabbit model and histologic and histomorphometric analyses were performed at early time points after insertion. Thirty-six cylindrical implants were inserted in the tibial diaphysis of six rabbits and left to heal for 1 to 42 days. Samples were processed into paraffin or methylmethacrylate sections, on which the surface of new bone, region of altered nuclear morphology, relative surface of basic multicellular units (BMUs) and blood vessels, and bone-to-implant contact were measured. After coagulum formation, osteoclasts and osteoblasts were observed at the bone surface 1 week after healing. In the preexisting bone, osteocytic lacunae appeared to be devoid of cells. This region of altered nuclear morphology continued to extend for 28 days (P <0.05) after implant insertion. This expansion was accompanied by an invasion of the damaged bone by BMUs that initiated intensive bone remodeling, which reached its maximum after 4 weeks (P <0.05) but was ongoing after 6 weeks of implant insertion. This study evaluated the early cellular events in cortical bone surrounding titanium implants. The insertion of an implant into bone initiates a series of biologic processes, including the formation of a hematoma, altered nuclear morphology of the osteocytes surrounding the implantation site, intensive bone remodeling, and the formation of new bone, eventually leading to the osseointegration of the implant.

  19. Combined estimation of thickness and velocities using ultrasound guided waves: a pioneering study on in vitro cortical bone samples.

    PubMed

    Foiret, Josquin; Minonzio, Jean-Gabriel; Chappard, Christine; Talmant, Maryline; Laugier, Pascal

    2014-09-01

    This paper reports for the first time on inverse estimation of several bone properties from guided-wave measurements in human bone samples. Previously, related approaches have focused on ultrasonic estimation of a single bone property at a time. The method is based on two steps: the multi-Lamb mode response is analyzed using the singular value decomposition signal processing method recently introduced in the field, then an identification procedure is run to find thickness and anisotropic elastic properties of the considered specimen. Prior to the measurements on bone, the method is validated on cortical bone-mimicking phantoms. The repeatability and the trueness of the estimated parameters on bone-mimicking phantoms were found around a few percent. Estimation of cortical thickness on bone samples was in good agreement with cortical thickness derived from high-resolution peripheral quantitative computed tomography data analysis of the samples.

  20. Mesenchymal stem cells from cortical bone demonstrate increased clonal incidence, potency, and developmental capacity compared to their bone marrow–derived counterparts

    PubMed Central

    Blashki, Daniel; Murphy, Matthew B; Ferrari, Mauro; Simmons, Paul J; Tasciotti, Ennio

    2016-01-01

    In this study, we show that matrix dense cortical bone is the more potent compartment of bone than bone marrow as a stromal source for mesenchymal stem cells as isolated from adult rats. Lineage-depleted cortical bone-mesenchymal stem cells demonstrated >150-fold enrichment of colony forming unit–fibroblasts per cell incidence. compared to lineage-depleted bone marrow-mesenchymal stem cells, corresponding to a 70-fold increase in absolute recovered colony forming unit–fibroblasts. The composite phenotype Lin−/CD45−/CD31−/VLA-1+/Thy-1+ enriched for clonogenic mesenchymal stem cells solely from cortical bone–derived cells from which 70% of clones spontaneously differentiated into all lineages of bone, cartilage, and adipose. Both populations generated vascularized bone tissue within subcutaneous implanted collagen scaffolds; however, cortical bone–derived cells formed significantly more osteoid than bone marrow counterparts, quantified by histology. The data demonstrate that our isolation protocol identifies and validates mesenchymal stem cells with superior clonal, proliferative, and developmental potential from cortical bone compared to the bone marrow niche although marrow persists as the typical source for mesenchymal stem cells both in the literature and current pre-clinical therapies. PMID:27579159

  1. Effects of Habitual Physical Activity and Fitness on Tibial Cortical Bone Mass, Structure and Mass Distribution in Pre-pubertal Boys and Girls: The Look Study.

    PubMed

    Duckham, Rachel L; Rantalainen, Timo; Ducher, Gaele; Hill, Briony; Telford, Richard D; Telford, Rohan M; Daly, Robin M

    2016-07-01

    Targeted weight-bearing activities during the pre-pubertal years can improve cortical bone mass, structure and distribution, but less is known about the influence of habitual physical activity (PA) and fitness. This study examined the effects of contrasting habitual PA and fitness levels on cortical bone density, geometry and mass distribution in pre-pubertal children. Boys (n = 241) and girls (n = 245) aged 7-9 years had a pQCT scan to measure tibial mid-shaft total, cortical and medullary area, cortical thickness, density, polar strength strain index (SSIpolar) and the mass/density distribution through the bone cortex (radial distribution divided into endo-, mid- and pericortical regions) and around the centre of mass (polar distribution). Four contrasting PA and fitness groups (inactive-unfit, inactive-fit, active-unfit, active-fit) were generated based on daily step counts (pedometer, 7-days) and fitness levels (20-m shuttle test and vertical jump) for boys and girls separately. Active-fit boys had 7.3-7.7 % greater cortical area and thickness compared to inactive-unfit boys (P < 0.05), which was largely due to a 6.4-7.8 % (P < 0.05) greater cortical mass in the posterior-lateral, medial and posterior-medial 66 % tibial regions. Cortical area was not significantly different across PA-fitness categories in girls, but active-fit girls had 6.1 % (P < 0.05) greater SSIpolar compared to inactive-fit girls, which was likely due to their 6.7 % (P < 0.05) greater total bone area. There was also a small region-specific cortical mass benefit in the posterior-medial 66 % tibia cortex in active-fit girls. Higher levels of habitual PA-fitness were associated with small regional-specific gains in 66 % tibial cortical bone mass in pre-pubertal children, particularly boys.

  2. The Beneficial Effects of Bisphosphonate-enoxacin on Cortical Bone Mass and Strength in Ovariectomized Rats.

    PubMed

    Liu, Xuqiang; Qu, Xinhua; Nie, Tao; Zhai, Zanjing; Li, Haowei; Ouyang, Zhengxiao; Qin, An; Zhang, Shuhong; Zhang, Shuangyan; Fan, Qiming; Tang, Tingting; Yu, Zhifeng; Dai, Min

    2017-01-01

    Osteoporosis is a major age-related bone disease characterized by low bone mineral density and a high risk of fractures. Bisphosphonates are considered as effective agents treating osteoporosis. However, long-term use of bisphosphonates is associated with some serious side effects, which limits the widespread clinical use of bisphosphonates. Here, we demonstrate a novel type of bone-targeting anti-resorptive agent, bisphosphonate-enoxacin (BE). In this study, ovariectomized rat model was established and treated with PBS, zoledronate (50 μg/kg) and different dose of BE (5 mg/kg and 10 mg/kg), respectively. The rats subjected to sham-operation and PBS treatment were considered as control group. Then, micro-computed tomography scanning, biomechanical tests, nano-indentation test and Raman analysis were used to compare the effects of zoledronate and BE on cortical bone mass, strength, and composition in ovariectomized rats. We found that both zoledronate and BE were beneficial to cortical bone strength. Three-point bending and nano-indentation tests showed that zoledronate- and BE-treated groups had superior general and local biomechanical properties compared to the ovariectomized groups. Interestingly, it seemed that BE-treated group got a better biomechanical property than the zoledronate-treated group. Also, BE-treated group showed significantly increased proteoglycan content compared with the zoledronate-treated group. We hypothesized that the increased bone strength and biomechanical properties was due to altered bone composition after treatment with BE. BE, a new bone-targeting agent, may be considered a more suitable anti-resorptive agent to treat osteoporosis and other bone diseases associated with decreased bone mass.

  3. Lattice strains and load partitioning in bovine trabecular bone.

    SciTech Connect

    Akhtar, R.; Daymond, M. R.; Almer, J. D.; Mummery, P. M.

    2012-02-01

    Microdamage and failure mechanisms have been well characterized in bovine trabecular bone. However, little is known about how elastic strains develop in the apatite crystals of the trabecular struts and their relationship with different deformation mechanisms. In this study, wide-angle high-energy synchrotron X-ray diffraction has been used to determine bulk elastic strains under in situ compression. Dehydrated bone is compared to hydrated bone in terms of their response to load. During compression, load is initially borne by trabeculae aligned parallel to loading direction with non-parallel trabeculae deforming by bending. Ineffective load partitioning is noted in dehydrated bone whereas hydrated bone behaves like a plastically yielding foam

  4. Lattice strains and load partitioning in bovine trabecular bone.

    PubMed

    Akhtar, R; Daymond, M R; Almer, J D; Mummery, P M

    2011-02-01

    Microdamage and failure mechanisms have been well characterized in bovine trabecular bone. However, little is known about how elastic strains develop in the apatite crystals of the trabecular struts and their relationship with different deformation mechanisms. In this study, wide-angle high-energy synchrotron X-ray diffraction has been used to determine bulk elastic strains under in situ compression. Dehydrated bone is compared to hydrated bone in terms of their response to load. During compression, load is initially borne by trabeculae aligned parallel to loading direction with non-parallel trabeculae deforming by bending. Ineffective load partitioning is noted in dehydrated bone whereas hydrated bone behaves like a plastically yielding foam.

  5. Effects of estrogen with micronized progesterone on cortical and trabecular bone mass and microstructure in recently postmenopausal women.

    PubMed

    Farr, Joshua N; Khosla, Sundeep; Miyabara, Yuko; Miller, Virginia M; Kearns, Ann E

    2013-02-01

    In women, cortical bone mass decreases significantly at menopause. By contrast, loss of trabecular bone begins in the third decade and accelerates after menopause. The aim of the study was to investigate the effects of estrogen on cortical and trabecular bone. The Kronos Early Estrogen Prevention Study is a double-blind, randomized, placebo-controlled trial of menopausal hormone treatment (MHT) in women, enrolled within 6-36 months of their final menstrual period. The study was conducted at the Mayo Clinic, Rochester, Minnesota. Subjects were treated with placebo (n = 31), or .45 mg/d conjugated equine estrogens (n = 20), or transdermal 50 μg/d 17β-estradiol (n = 25) with pulsed micronized progesterone. Cortical and trabecular microarchitecture at the distal radius was assessed by high-resolution peripheral quantitative computed tomography. At the distal radius, cortical volumetric bone mineral density (vBMD) decreased, and cortical porosity increased in the placebo group; MHT prevented these changes. By contrast, MHT did not prevent decreases in trabecular microarchitecture at the radius. However, MHT prevented decreases in trabecular vBMD at the thoracic spine (assessed in a subset of subjects; n = 51). These results indicate that MHT prevents deterioration in radial cortical vBMD and porosity in recently menopausal women. The maintenance of cortical bone in response to estrogen likely has important clinical implications because cortical bone morphology plays an important role in bone strength. However, effects of MHT on trabecular bone at the radius differ from those at the thoracic spine. Underlying mechanisms for these site-specific effects of MHT on cortical vs trabecular bone require further investigation.

  6. Effects of Estrogen with Micronized Progesterone on Cortical and Trabecular Bone Mass and Microstructure in Recently Postmenopausal Women

    PubMed Central

    Farr, Joshua N.; Khosla, Sundeep; Miyabara, Yuko; Miller, Virginia M.

    2013-01-01

    Context: In women, cortical bone mass decreases significantly at menopause. By contrast, loss of trabecular bone begins in the third decade and accelerates after menopause. Objective: The aim of the study was to investigate the effects of estrogen on cortical and trabecular bone. Design: The Kronos Early Estrogen Prevention Study is a double-blind, randomized, placebo-controlled trial of menopausal hormone treatment (MHT) in women, enrolled within 6–36 months of their final menstrual period. Setting: The study was conducted at the Mayo Clinic, Rochester, Minnesota. Intervention: Subjects were treated with placebo (n = 31), or .45 mg/d conjugated equine estrogens (n = 20), or transdermal 50 μg/d 17β-estradiol (n = 25) with pulsed micronized progesterone. Main Outcome Measures: Cortical and trabecular microarchitecture at the distal radius was assessed by high-resolution peripheral quantitative computed tomography. Results: At the distal radius, cortical volumetric bone mineral density (vBMD) decreased, and cortical porosity increased in the placebo group; MHT prevented these changes. By contrast, MHT did not prevent decreases in trabecular microarchitecture at the radius. However, MHT prevented decreases in trabecular vBMD at the thoracic spine (assessed in a subset of subjects; n = 51). These results indicate that MHT prevents deterioration in radial cortical vBMD and porosity in recently menopausal women. Conclusion: The maintenance of cortical bone in response to estrogen likely has important clinical implications because cortical bone morphology plays an important role in bone strength. However, effects of MHT on trabecular bone at the radius differ from those at the thoracic spine. Underlying mechanisms for these site-specific effects of MHT on cortical vs trabecular bone require further investigation. PMID:23322818

  7. Metastasin S100A4 is a mediator of sex hormone-dependent formation of the cortical bone.

    PubMed

    Erlandsson, Malin C; Bian, Li; Jonsson, Ing-Marie; Andersson, Karin M; Bokarewa, Maria I

    2013-08-01

    S100A4 is a Ca-binding protein participating in regulation of cell growth, survival, and motility. Here we studied the role of S100A4 protein in sex hormone-regulated bone formation. Bone mineral density in the trabecular and cortical compartments was evaluated in female S100A4 knockout (KO), in matched wild-type (WT) counterparts, and in WT mice treated with lentiviral small hairpin RNA construct inhibiting the S100A4 gene transcription or with a nontargeting construct, by peripheral quantitative computed tomography. The effect of sex hormones on bone was measured 5 weeks after ovariectomy (OVX) and/or dehydroepiadrosterone treatment. S100A4KO had an excessive trabecular and cortical bone formation compared with the age- and sex-matched WT mice. S100A4KO had an increased periosteal circumference (P = .001), cortical thickness (P = .056), and cortical area (P = .003), which predicted 20% higher bone strength in S100A4KO (P = .013). WT mice treated with small hairpin RNA-S100A4 showed an increase of the cortical bone parameters in a fashion identical with S100A4KO mice, indicating the key role of S100A4 in the changed bone formation. S100A4KO mice had higher serum levels of osteocalcin and a higher number of osteocalcin-positive osteoblasts under the periosteum. OVX-S100A4 resulted in the loss of the cortical bone supported by high CTX-I levels, whereas no such changes were observed in OVX-WT mice. S100A4KO mice resisted the dehydroepiadrosterone -induced bone formation observed in the WT counterparts. Our study indicates that S100A4 is a regulator of bone formation, which inhibits bone excess in the estrogen-sufficient mice and prevents the cortical bone loss in the estrogen-deprived mice.

  8. Cortical-Bone Fragility — Insights from sFRP4 Deficiency in Pyle’s Disease

    PubMed Central

    Unger, Sheila; Hesse, Eric; Yamana, Kei; Kiviranta, Riku; Solban, Nicolas; Liu, Jeff; Brommage, Robert; Boduroglu, Koray; Bonafé, Luisa; Campos-Xavier, Belinda; Dikoglu, Esra; Eastell, Richard; Gossiel, Fatma; Harshman, Keith; Nishimura, Gen; Girisha, Katta M.; Stevenson, Brian J.; Takita, Hiroyuki; Rivolta, Carlo

    2016-01-01

    BACKGROUND Cortical-bone fragility is a common feature in osteoporosis that is linked to nonvertebral fractures. Regulation of cortical-bone homeostasis has proved elusive. The study of genetic disorders of the skeleton can yield insights that fuel experimental therapeutic approaches to the treatment of rare disorders and common skeletal ailments. METHODS We evaluated four patients with Pyle’s disease, a genetic disorder that is characterized by cortical-bone thinning, limb deformity, and fractures; two patients were examined by means of exome sequencing, and two were examined by means of Sanger sequencing. After a candidate gene was identified, we generated a knockout mouse model that manifested the phenotype and studied the mechanisms responsible for altered bone architecture. RESULTS In all affected patients, we found biallelic truncating mutations in SFRP4, the gene encoding secreted frizzled-related protein 4, a soluble Wnt inhibitor. Mice deficient in Sfrp4, like persons with Pyle’s disease, have increased amounts of trabecular bone and unusually thin cortical bone, as a result of differential regulation of Wnt and bone morphogenetic protein (BMP) signaling in these two bone compartments. Treatment of Sfrp4-deficient mice with a soluble Bmp2 receptor (RAP-661) or with antibodies to sclerostin corrected the cortical-bone defect. CONCLUSIONS Our study showed that Pyle’s disease was caused by a deficiency of sFRP4, that cortical-bone and trabecular-bone homeostasis were governed by different mechanisms, and that sFRP4-mediated cross-regulation between Wnt and BMP signaling was critical for achieving proper cortical-bone thickness and stability. (Funded by the Swiss National Foundation and the National Institutes of Health.) PMID:27355534

  9. Ontogeny of bone strain: the zygomatic arch in pigs

    PubMed Central

    Pedersen, Scott C.; Huang, Xiaofeng

    2006-01-01

    Summary At the time of weaning, infant animals have little experience with hard food, and thus their skulls are not likely to be epigenetically adapted for the loads imposed by mastication. We examined bone strain in the zygomatic arch of 4-week-old weanling piglets. Functional strains in piglets differed from those previously reported for older pigs (Herring et al., 1996; Rafferty et al., 2000) in that the squamosal bone was not bent in the horizontal plane and the principal tensile strain on the zygomatic bone did not correspond to the direction of masseter muscle pull. Strain patterns were more variable in piglets than in older pigs. In older pigs masticatory strains can be reproduced by stimulating the masseter muscles. When the piglet masseter was stimulated, strain patterns were more similar to those of older pigs, but shear strain magnitudes were the largest yet recorded from mammalian skull bones, up to 4000 με. To put these findings in the context of skeletal adaptation, 45 dry skulls, including some animals from the strain study, were measured. Reduced major axis regressions indicated that the infant arch was rounder in cross section and straighter than that of older animals. With growth the arch became dorsoventrally higher, while mediolateral thickness decreased in the squamosal bone. Overall, these changes should make strain more predictable, explaining the lower variability in older animals. Other factors likely to be important in causing unique strain regimes in piglets include (1) unfamiliarity with hard food, (2) greater importance of muscles other than the same-side masseter, and (3) greater proximity of molariform teeth to the arch. Collectively, these data indicate that the skeleton is not pre-adapted for specific functional loads. PMID:16339870

  10. Acoustic emission based monitoring of the microdamage evolution during fatigue of human cortical bone.

    PubMed

    Agcaoglu, Serife; Akkus, Ozan

    2013-08-01

    Stress fractures are frequently observed in physically active populations, and they are believed to be associated with microcrack accumulation. There are not many tools for real-time monitoring of microdamage formation during fatigue of bone, in vivo or in vitro. Acoustic emission (AE) based detection of stress waves resulting from microdamage formation is a promising method to assess the rate and energetics of microdamage formation during fatigue. The current study aims to assess the time history of the occurrence of AE events during fatigue loading of human tibial cortical bone and to determine the associations between AE variables (energy content of waves, number of AE waveforms, etc.), fatigue life, and bone ash content. Fatigue test specimens were prepared from the distal diaphysis of human tibial cortical bone (N = 32, 22 to 52 years old, male and female). The initiation of acoustic emissions was concomitant with the nonlinear increase in sample compliance and the cumulative number of AE events increased asymptotically in the prefailure period. The results demonstrated that AE method was able to predict the onset of failure by 95% of the fatigue life for the majority of the samples. The variation in the number of emissions until failure ranged from 6 to 1861 implying a large variation in crack activity between different samples. The results also revealed that microdamage evolution was a function of the level of tissue mineralization such that more mineralized bone matrix failed with fewer crack events with higher energy whereas less mineralized tissue generated more emissions with lower energy. In conclusion, acoustic emission based surveillance during fatigue of cortical bone demonstrates a large scatter, where some bones fail with substantial crack activity and a minority of samples fail without significant amount of crack formation.

  11. Spaceflight-relevant types of ionizing radiation and cortical bone: Potential LET effect?

    PubMed Central

    Lloyd, Shane A.J.; Bandstra, Eric R.; Travis, Neil D.; Nelson, Gregory A.; Bourland, J. Daniel; Pecaut, Michael J.; Gridley, Daila S.; Willey, Jeffrey S.; Bateman, Ted A.

    2008-01-01

    Extended exposure to microgravity conditions results in significant bone loss. Coupled with radiation exposure, this phenomenon may place astronauts at a greater risk for mission-critical fractures. In a previous study, we identified a profound and prolonged loss of trabecular bone (29−39%) in mice following exposure to an acute, 2 Gy dose of radiation simulating both solar and cosmic sources. However, because skeletal strength depends on trabecular and cortical bone, accurate assessment of strength requires analysis of both bone compartments. The objective of the present study was to examine various properties of cortical bone in mice following exposure to multiple types of spaceflight-relevant radiation. Nine-week old, female C57BL/6 mice were sacrificed 110 days after exposure to a single, whole body, 2 Gy dose of gamma, proton, carbon, or iron radiation. Femora were evaluated with biomechanical testing, microcomputed tomography, quantitative histomorphometry, percent mineral content, and micro-hardness analysis. Compared to non-irradiated controls, there were significant differences compared to carbon or iron radiation for only fracture force, medullary area and mineral content. A greater differential effect based on linear energy transfer (LET) level may be present: high-LET (carbon or iron) particle irradiation was associated with a decline in structural properties (maximum force, fracture force, medullary area, and cortical porosity) and mineral composition compared to low-LET radiation (gamma and proton). Bone loss following irradiation appears to be largely specific to trabecular bone and may indicate unique biological microenvironments and microdosimetry conditions. However, the limited time points examined and non-haversian skeletal structure of the mice employed highlight the need for further investigation. PMID:19122806

  12. Spaceflight-relevant types of ionizing radiation and cortical bone: Potential LET effect?

    NASA Astrophysics Data System (ADS)

    Lloyd, Shane A. J.; Bandstra, Eric R.; Travis, Neil D.; Nelson, Gregory A.; Bourland, J. Daniel; Pecaut, Michael J.; Gridley, Daila S.; Willey, Jeffrey S.; Bateman, Ted A.

    2008-12-01

    Extended exposure to microgravity conditions results in significant bone loss. Coupled with radiation exposure, this phenomenon may place astronauts at a greater risk for mission-critical fractures. In a previous study, we identified a profound and prolonged loss of trabecular bone (29-39%) in mice following exposure to an acute, 2 Gy dose of radiation simulating both solar and cosmic sources. However, because skeletal strength depends on trabecular and cortical bone, accurate assessment of strength requires analysis of both bone compartments. The objective of the present study was to examine various properties of cortical bone in mice following exposure to multiple types of spaceflight-relevant radiation. Nine-week old, female C57BL/6 mice were sacrificed 110 days after exposure to a single, whole body, 2 Gy dose of gamma, proton, carbon, or iron radiation. Femora were evaluated with biomechanical testing, microcomputed tomography, quantitative histomorphometry, percent mineral content, and micro-hardness analysis. Compared to non-irradiated controls, there were significant differences compared to carbon or iron radiation for only fracture force, medullary area and mineral content. A greater differential effect based on linear energy transfer (LET) level may be present: high-LET (carbon or iron) particle irradiation was associated with a decline in structural properties (maximum force, fracture force, medullary area, and cortical porosity) and mineral composition compared to low-LET radiation (gamma and proton). Bone loss following irradiation appears to be largely specific to trabecular bone and may indicate unique biological microenvironments and microdosimetry conditions. However, the limited time points examined and non-haversian skeletal structure of the mice employed highlight the need for further investigation.

  13. Bone mineral density in children and adolescents with juvenile diabetes: selective measurement of bone mineral density of trabecular and cortical bone using peripheral quantitative computed tomography.

    PubMed

    Lettgen, B; Hauffa, B; Möhlmann, C; Jeken, C; Reiners, C

    1995-01-01

    Bone mineral density (BMD) was studied in 21 children and adolescents with type I diabetes and in age- and sex-matched healthy controls. BMD was selectively measured in trabecular and total bone using peripheral quantitative computed tomography (pQCT). Cortical bone density was calculated. There was a decrease of trabecular bone density (-18.9%, p < 0.01), total bone density (-9.0%, NS) and cortical bone density (-5.1%, NS) in diabetes. Trabecular bone density was inversely correlated with the duration of diabetes and the concentration of glycosylated hemoglobin (HbA1) (r = -0.48, p = 0.027 and r = -0.63, p = 0.002, respectively). Total BMD correlated inversely with HbA1 (r = -0.52, p = 0.017). pQCT allows the selective measurement of metabolically active trabecular bone where changes of mineralization first occur. We conclude that pQCT is a useful method for investigating BMD in diabetes.

  14. Development of cortical bone geometry in the human femoral and tibial diaphysis.

    PubMed

    Gosman, James H; Hubbell, Zachariah R; Shaw, Colin N; Ryan, Timothy M

    2013-05-01

    Ontogenetic growth processes in human long bones are key elements, determining the variability of adult bone structure. This study seeks to identify and describe the interaction between ontogenetic growth periods and changes in femoral and tibial diaphyseal shape. Femora and tibiae (n = 46) ranging developmentally from neonate to skeletally mature were obtained from the Norris Farms No. 36 archeological skeletal series. High-resolution X-ray computed tomography scans were collected. Whole-diaphysis cortical bone drift patterns and relative bone envelope modeling activity across ages were assessed in five cross-sections per bone (total bone length: 20%, 35%, 50%, 65%, and 80%) by measuring the distance from the section centroid to the endosteal and periosteal margins in eight sectors using ImageJ. Pearson correlations were performed to document and interpret the relationship between the cross-sectional shape (Imax /Imin ), total subperiosteal area, cortical area, and medullary cavity area for each slice location and age for both the femur and the tibia. Differences in cross-sectional shape between age groups at each cross-sectional position were assessed using nonparametric Mann-Whitney U tests. The data reveal that the femoral and tibial midshaft shape are relatively conserved throughout growth; yet, conversely, the proximal and distal femoral diaphysis and proximal tibial diaphysis appear more sensitive to developmentally induced changes in mechanical loading. Two time periods of accelerated change are identified: early childhood and prepuberty/adolescence.

  15. Cortical bone growth and maturational changes in dwarf rats induced by recombinant human growth hormone

    NASA Technical Reports Server (NTRS)

    Martinez, D. A.; Orth, M. W.; Carr, K. E.; Vanderby, R. Jr; Vailas, A. C.

    1996-01-01

    The growth hormone (GH)-deficient dwarf rat was used to investigate recombinant human (rh) GH-induced bone formation and to determine whether rhGH facilitates simultaneous increases in bone formation and bone maturation during rapid growth. Twenty dwarf rats, 37 days of age, were randomly assigned to dwarf plus rhGH (GH; n = 10) and dwarf plus vehicle (n = 10) groups. The GH group received 1.25 mg rhGH/kg body wt two times daily for 14 days. Biochemical, morphological, and X-ray diffraction measurements were performed on the femur middiaphysis. rhGH stimulated new bone growth in the GH group, as demonstrated by significant increases (P < 0.05) in longitudinal bone length (6%), middiaphyseal cross-sectional area (20%), and the amount of newly accreted bone collagen (28%) in the total pool of middiaphyseal bone collagen. Cortical bone density, mean hydroxyapatite crystal size, and the calcium and collagen contents (microgram/mm3) were significantly smaller in the GH group (P < 0.05). Our findings suggest that the processes regulating new collagen accretion, bone collagen maturation, and mean hydroxyapatite crystal size may be independently regulated during rapid growth.

  16. Cortical bone growth and maturational changes in dwarf rats induced by recombinant human growth hormone

    NASA Technical Reports Server (NTRS)

    Martinez, D. A.; Orth, M. W.; Carr, K. E.; Vanderby, R. Jr; Vailas, A. C.

    1996-01-01

    The growth hormone (GH)-deficient dwarf rat was used to investigate recombinant human (rh) GH-induced bone formation and to determine whether rhGH facilitates simultaneous increases in bone formation and bone maturation during rapid growth. Twenty dwarf rats, 37 days of age, were randomly assigned to dwarf plus rhGH (GH; n = 10) and dwarf plus vehicle (n = 10) groups. The GH group received 1.25 mg rhGH/kg body wt two times daily for 14 days. Biochemical, morphological, and X-ray diffraction measurements were performed on the femur middiaphysis. rhGH stimulated new bone growth in the GH group, as demonstrated by significant increases (P < 0.05) in longitudinal bone length (6%), middiaphyseal cross-sectional area (20%), and the amount of newly accreted bone collagen (28%) in the total pool of middiaphyseal bone collagen. Cortical bone density, mean hydroxyapatite crystal size, and the calcium and collagen contents (microgram/mm3) were significantly smaller in the GH group (P < 0.05). Our findings suggest that the processes regulating new collagen accretion, bone collagen maturation, and mean hydroxyapatite crystal size may be independently regulated during rapid growth.

  17. In vivo imaging of rat cortical bone porosity by synchrotron phase contrast micro computed tomography.

    PubMed

    Pratt, I V; Belev, G; Zhu, N; Chapman, L D; Cooper, D M L

    2015-01-07

    Cortical bone is a dynamic tissue which undergoes adaptive and pathological changes throughout life. Direct longitudinal tracking of this remodeling process holds great promise for improving our understanding of bone development, maintenance and senescence. The application of in vivo micro-computed tomography (micro-CT) has enabled longitudinal tracking of trabecular bone microarchitecture with commercially available scanners generally operating in the 10-20 µm voxel range with absorbed doses reported between 0.5 and 1 Gy. Imaging of cortical bone microarchitecture (porosity) requires higher resolution and thus in vivo imaging of these structures has not been achieved due to excessive radiation dose. In this study we tested the hypothesis that synchrotron propagation phase contrast micro-CT can enable in vivo imaging of cortical porosity in rats at doses comparable to those currently employed for trabecular bone imaging. Synchrotron imaging experiments were conducted at the Canadian Light Source using the bending magnet beamline of the BioMedical Imaging and Therapy (BMIT) facility. Protocol optimization (propagation distance, projection number) was conducted ex vivo on rat (Sprague-Dawley) forelimbs with dose determined by ion chamber and lithium fluoride crystal thermoluminescent dosimeters. Comparative ex vivo imaging was performed using laboratory in vivo scanning systems, identifying a range of doses between 1.2-3.6 Gy for common protocols. A final in vivo synchrotron protocol involving a 2.5 Gy dose was implemented with live rats. The resulting images demonstrated improved delineation of cortical porosity through the improved edge enhancement effect of phase contrast, opening the door to novel experimental studies involving the longitudinal tracking of remodeling.

  18. Microarchitectural Deterioration of Cortical and Trabecular Bone: Differing Effects of Denosumab and Alendronate

    PubMed Central

    Seeman, Ego; Delmas, Pierre D; Hanley, David A; Sellmeyer, Deborah; Cheung, Angela M; Shane, Elizabeth; Kearns, Ann; Thomas, Thierry; Boyd, Steven K; Boutroy, Stephanie; Bogado, Cesar; Majumdar, Sharmila; Fan, Michelle; Libanati, Cesar; Zanchetta, Jose

    2015-01-01

    The intensity of bone remodeling is a critical determinant of the decay of cortical and trabecular microstructure after menopause. Denosumab suppresses remodeling more than alendronate, leading to greater gains in areal bone mineral density (aBMD). These greater gains may reflect differing effects of each drug on bone microarchitecture and strength. In a phase 2 double-blind pilot study, 247 postmenopausal women were randomized to denosumab (60mg subcutaneous 6 monthly), alendronate (70mg oral weekly), or placebo for 12 months. All received daily calcium and vitamin D. Morphologic changes were assessed using high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius and distal tibia and QCT at the distal radius. Denosumab decreased serum C-telopeptide more rapidly and markedly than alendronate. In the placebo arm, total, cortical, and trabecular BMD and cortical thickness decreased (−2.1% to −0.8%) at the distal radius after 12 months. Alendronate prevented the decline (−0.6% to 2.4%, p = .051 to < .001 versus placebo), whereas denosumab prevented the decline or improved these variables (0.3% to 3.4%, p < .001 versus placebo). Changes in total and cortical BMD were greater with denosumab than with alendronate (p ≤ .024). Similar changes in these parameters were observed at the tibia. The polar moment of inertia also increased more in the denosumab than alendronate or placebo groups (p < .001). Adverse events did not differ by group. These data suggest that structural decay owing to bone remodeling and progression of bone fragility may be prevented more effectively with denosumab. PMID:20222106

  19. In vivo imaging of rat cortical bone porosity by synchrotron phase contrast micro computed tomography

    NASA Astrophysics Data System (ADS)

    Pratt, I. V.; Belev, G.; Zhu, N.; Chapman, L. D.; Cooper, D. M. L.

    2015-01-01

    Cortical bone is a dynamic tissue which undergoes adaptive and pathological changes throughout life. Direct longitudinal tracking of this remodeling process holds great promise for improving our understanding of bone development, maintenance and senescence. The application of in vivo micro-computed tomography (micro-CT) has enabled longitudinal tracking of trabecular bone microarchitecture with commercially available scanners generally operating in the 10-20 µm voxel range with absorbed doses reported between 0.5 and 1 Gy. Imaging of cortical bone microarchitecture (porosity) requires higher resolution and thus in vivo imaging of these structures has not been achieved due to excessive radiation dose. In this study we tested the hypothesis that synchrotron propagation phase contrast micro-CT can enable in vivo imaging of cortical porosity in rats at doses comparable to those currently employed for trabecular bone imaging. Synchrotron imaging experiments were conducted at the Canadian Light Source using the bending magnet beamline of the BioMedical Imaging and Therapy (BMIT) facility. Protocol optimization (propagation distance, projection number) was conducted ex vivo on rat (Sprague-Dawley) forelimbs with dose determined by ion chamber and lithium fluoride crystal thermoluminescent dosimeters. Comparative ex vivo imaging was performed using laboratory in vivo scanning systems, identifying a range of doses between 1.2-3.6 Gy for common protocols. A final in vivo synchrotron protocol involving a 2.5 Gy dose was implemented with live rats. The resulting images demonstrated improved delineation of cortical porosity through the improved edge enhancement effect of phase contrast, opening the door to novel experimental studies involving the longitudinal tracking of remodeling.

  20. Relating Crack-tip Deformation to Mineralization and Fracture Resistance in Human Femur Cortical Bone

    PubMed Central

    Chan, Kwai S.; Chan, Candace K.; Nicolella, Daniel P.

    2009-01-01

    The risk of bone fracture increases with age because of a variety of factors that include, among others, decreasing bone quantity and quality. Despite recent advances, the roles of bone microstructure and trace mineralization in the fracture process are not well understood. In this study, we utilize a combination of in-situ fracture toughness testing, digital strain mapping, and x-ray photoelectron spectroscopy techniques to characterize the near-tip strain field, fracture toughness, and chemical elements on the fracture surface of bone specimens from donors of two ages (48-year-old and 78-year-old females). We show that age-related embrittlement of bone fracture is associated with higher near-tip strains by lamellar shear and crack defection at lamellar interfaces in the young bone and their absence in the old bone. The different near-tip deformation behaviors may be associated with the presence of Si and Zn in the young bone but more Ca and P and the lack of Si and Zn in the old bone. PMID:19497396

  1. Both resistance and agility training increase cortical bone density in 75- to 85-year-old women with low bone mass: a 6-month randomized controlled trial.

    PubMed

    Liu-Ambrose, Teresa Y L; Khan, Karim M; Eng, Janice J; Heinonen, Ari; McKay, Heather A

    2004-01-01

    A randomized, controlled, single-blinded 25-wk prospective study was conducted to compare the effects of group-based resistance and agility training on bone, as measured by both dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT), in older women with low bone mass. Ninety-eight community-dwelling women aged 75-85 yr were randomized to one of three experimental groups: resistance training (n = 32), agility training (n = 34), or stretching (sham exercise) (n = 32). Total hip, femoral neck, and trochanteric bone mineral density (BMD) were measured by DXA. Peripheral QCT measurements were performed at the tibia and radius. The pQCT outcome measures at the shaft regions were cortical bone content, cortical bone cross-sectional area, cortical bone density, and density-weighted polar section modulus (SSI). The pQCT outcome measures at the distal sites were total bone content, total bone cross-sectional area, and total bone density. At trial completion, the agility training group significantly increased cortical bone density by 0.5 +/- 0.2% (SE) at the tibial shaft compared with a 0.4 +/- 0.3% loss in the stretching group. The resistance training group significantly increased cortical bone density (1.4 +/- 0.6%) at the radial shaft compared, with a 0.4 +/- 0.5% loss in the agility training group. No significant between-group differences were observed in the other bone outcome measures (by DXA or pQCT). Future research is needed to determine the mechanism(s) responsible for the observed adaptation of the cortical bone to mechanical loading.

  2. T1 correlates age: A short-TE MR relaxometry study in vivo on human cortical bone free water at 1.5T.

    PubMed

    Akbari, Atena; Abbasi-Rad, Shahrokh; Rad, Hamidreza Saligheh

    2016-02-01

    Large pores of human cortical bone (>30μm) are filled with fluids, essentially consisting of water, suggesting that cortical bone free water can be considered as a reliable surrogate measure of cortical bone porosity and hence quality. Signal from such pores can be reliably captured using Short Echo Time (STE) pulse sequence with echo-time in the range of 1-1.5msec (which should be judiciously selected correspond to T2(⁎) value of free water molecules). Furthermore, it is well-known that cortical bone T1-relaxivity is a function of its geometry, suggesting that cortical bone free water increases with age. In this work, we quantified cortical bone free water longitudinal relaxation time (T1) by a Dual-TR technique using STE pulse sequence. In the sequel, we investigated relationship between STE-derived cortical bone free water T1-values and age in a group of healthy volunteers (thirty subjects covering the age range of 20-70years) at 1.5T. Preliminary results showed that cortical bone free water T1 highly correlates with age (r(2)=0.73, p<0.0001), representing cortical bone free water T1 as a reliable indicator of cortical bone porosity and age-related deterioration. It can be concluded that STE-MRI can be utilized as proper alternative in quantifying cortical bone porosity parameters in-vivo, with the advantages of widespread clinical availability and being cost-effective.

  3. The effect of staining on the monotonic tensile mechanical properties of human cortical bone

    PubMed Central

    Kayacan, Ramazan

    2007-01-01

    Microdamage in the form of microcracks has been observed in cortical bone following in vivo and in vitro fatigue loading. It has been suggested that bone has an inherent ability to repair microdamage at physiological activity levels. If the biological remodelling and repair process cannot keep up with the rate of damage accumulation, as in ageing bone and in individuals such as athletes and military recruits, microdamage may accumulate even at physiological activity levels. Such microdamage accumulation is thought to contribute to stress and fragility fractures. It is therefore important to obtain quantitative data on the rate of damage accumulation so as to understand the etiology of skeletal fractures. Sequential labelling of microdamage using fluorochrome stains at different stages of mechanical loading is becoming standard for assessing damage evolution. Although verification of this staining technique is provided in the literature, it has not yet been reported if the stains change the mechanical properties of cortical bone. In this study, monotonic tensile tests were performed to investigate the effect of the staining on the monotonic tensile mechanical properties of cortical bone. Forty-eight specimens were machined from human femora obtained from three male subjects, aged 52–55 years, and all 48 specimens were systematically divided into one control and three treatment groups. Specimens in the first (n = 12) and second treatment groups (n = 12) were stained with alizarin complexone and calcein (0.0005 m), respectively, for 16 h under 50 mmHg vacuum. Specimens in the third treatment group (n = 12) were kept in calcium-supplemented saline solution under the same conditions of the first and second treatment groups. Specimens in the control group (n = 12) were removed from the freezer prior to testing and allowed to thaw at room temperature in saline solution. Differences among the mean values of the mechanical properties for four testing groups were

  4. The effect of staining on the monotonic tensile mechanical properties of human cortical bone.

    PubMed

    Kayacan, Ramazan

    2007-11-01

    Microdamage in the form of microcracks has been observed in cortical bone following in vivo and in vitro fatigue loading. It has been suggested that bone has an inherent ability to repair microdamage at physiological activity levels. If the biological remodelling and repair process cannot keep up with the rate of damage accumulation, as in ageing bone and in individuals such as athletes and military recruits, microdamage may accumulate even at physiological activity levels. Such microdamage accumulation is thought to contribute to stress and fragility fractures. It is therefore important to obtain quantitative data on the rate of damage accumulation so as to understand the etiology of skeletal fractures. Sequential labelling of microdamage using fluorochrome stains at different stages of mechanical loading is becoming standard for assessing damage evolution. Although verification of this staining technique is provided in the literature, it has not yet been reported if the stains change the mechanical properties of cortical bone. In this study, monotonic tensile tests were performed to investigate the effect of the staining on the monotonic tensile mechanical properties of cortical bone. Forty-eight specimens were machined from human femora obtained from three male subjects, aged 52-55 years, and all 48 specimens were systematically divided into one control and three treatment groups. Specimens in the first (n = 12) and second treatment groups (n = 12) were stained with alizarin complexone and calcein (0.0005 M), respectively, for 16 h under 50 mmHg vacuum. Specimens in the third treatment group (n = 12) were kept in calcium-supplemented saline solution under the same conditions of the first and second treatment groups. Specimens in the control group (n = 12) were removed from the freezer prior to testing and allowed to thaw at room temperature in saline solution. Differences among the mean values of the mechanical properties for four testing groups were determined

  5. Estrogen regulates the rate of bone turnover but bone balance in ovariectomized rats is modulated by prevailing mechanical strain

    NASA Technical Reports Server (NTRS)

    Westerlind, K. C.; Wronski, T. J.; Ritman, E. L.; Luo, Z. P.; An, K. N.; Bell, N. H.; Turner, R. T.

    1997-01-01

    Estrogen deficiency induced bone loss is associated with increased bone turnover in rats and humans. The respective roles of increased bone turnover and altered balance between bone formation and bone resorption in mediating estrogen deficiency-induced cancellous bone loss was investigated in ovariectomized rats. Ovariectomy resulted in increased bone turnover in the distal femur. However, cancellous bone was preferentially lost in the metaphysis, a site that normally experiences low strain energy. No bone loss was observed in the epiphysis, a site experiencing higher strain energy. The role of mechanical strain in maintaining bone balance was investigated by altering the strain history. Mechanical strain was increased and decreased in long bones of ovariectomized rats by treadmill exercise and functional unloading, respectively. Functional unloading was achieved during orbital spaceflight and following unilateral sciatic neurotomy. Increasing mechanical loading reduced bone loss in the metaphysis. In contrast, decreasing loading accentuated bone loss in the metaphysis and resulted in bone loss in the epiphysis. Finally, administration of estrogen to ovariectomized rats reduced bone loss in the unloaded and prevented loss in the loaded limb following unilateral sciatic neurotomy in part by reducing indices of bone turnover. These results suggest that estrogen regulates the rate of bone turnover, but the overall balance between bone formation and bone resorption is influenced by prevailing levels of mechanical strain.

  6. Toughness and damage susceptibility in human cortical bone is proportional to mechanical inhomogeneity at the osteonal-level.

    PubMed

    Katsamenis, Orestis L; Jenkins, Thomas; Thurner, Philipp J

    2015-07-01

    Limitations associated with current clinical fracture risk assessment tools highlight the need for increased understanding of the fracture mechanisms of the bone and, ideally, a means of assessing this in vivo. Being a multi-layered hierarchical structure, the overall properties of the bone are dictated by its structural and compositional properties over multiple length scales. In this study, we investigate the osteonal-, micro- and tissue-level mechanical behaviour of cortical bone tissue samples from young and elderly donors through atomic force microscope (AFM) cantilever-based nanoindentation, reference point microindentation (RPI) and fracture toughness experiments respectively. We demonstrate that bone's fracture toughness and crack growth resistance at the tissue-level are significantly correlated to damage susceptibility at the micro-level, and mechanical inhomogeneity between lamellae and interlamellar areas at the osteonal-level. In more detail, reduced nanoelasticity inhomogeneity of lamellar/interlamellar layers within the osteons correlated to increased indentation depth at the micro-level and an overall reduction in crack-growth toughness and fracture toughness of the tissue. Our data also suggest that deterioration of bone's mechanical properties is expressed concurrently at these three levels, and that mechanical inhomogeneity between the principal structural units of the cortical tissue holds a key role on bone's toughness behaviour. We hypothesise that the reduction in nanoelasticity inhomogeneity is--at least to some extent--responsible for the inability of the microstructure to effectively adapt to the applied load, e.g. by redistributing strains, in a non-catastrophic manner preventing damage formation and propagation. Our hypothesis is further supported by synchrotron radiation micro-computed tomography (SRμCT) data, which show that failure of tougher bone specimens is governed by increased deflection of the crack path and broadly spread

  7. Stochastic multiscale modelling of cortical bone elasticity based on high-resolution imaging.

    PubMed

    Sansalone, Vittorio; Gagliardi, Davide; Desceliers, Christophe; Bousson, Valérie; Laredo, Jean-Denis; Peyrin, Françoise; Haïat, Guillaume; Naili, Salah

    2016-02-01

    Accurate and reliable assessment of bone quality requires predictive methods which could probe bone microstructure and provide information on bone mechanical properties. Multiscale modelling and simulation represent a fast and powerful way to predict bone mechanical properties based on experimental information on bone microstructure as obtained through X-ray-based methods. However, technical limitations of experimental devices used to inspect bone microstructure may produce blurry data, especially in in vivo conditions. Uncertainties affecting the experimental data (input) may question the reliability of the results predicted by the model (output). Since input data are uncertain, deterministic approaches are limited and new modelling paradigms are required. In this paper, a novel stochastic multiscale model is developed to estimate the elastic properties of bone while taking into account uncertainties on bone composition. Effective elastic properties of cortical bone tissue were computed using a multiscale model based on continuum micromechanics. Volume fractions of bone components (collagen, mineral, and water) were considered as random variables whose probabilistic description was built using the maximum entropy principle. The relevance of this approach was proved by analysing a human bone sample taken from the inferior femoral neck. The sample was imaged using synchrotron radiation micro-computed tomography. 3-D distributions of Haversian porosity and tissue mineral density extracted from these images supplied the experimental information needed to build the stochastic models of the volume fractions. Thus, the stochastic multiscale model provided reliable statistical information (such as mean values and confidence intervals) on bone elastic properties at the tissue scale. Moreover, the existence of a simpler "nominal model", accounting for the main features of the stochastic model, was investigated. It was shown that such a model does exist, and its relevance

  8. CD44 deficiency inhibits unloading-induced cortical bone loss through downregulation of osteoclast activity

    PubMed Central

    Li, Yuheng; Zhong, Guohui; Sun, Weijia; Zhao, Chengyang; Zhang, Pengfei; Song, Jinping; Zhao, Dingsheng; Jin, Xiaoyan; Li, Qi; Ling, Shukuan; Li, Yingxian

    2015-01-01

    The CD44 is cellular surface adhesion molecule that is involved in physiological processes such as hematopoiesis, lymphocyte homing and limb development. It plays an important role in a variety of cellular functions including adhesion, migration, invasion and survival. In bone tissue, CD44 is widely expressed in osteoblasts, osteoclasts and osteocytes. However, the mechanisms underlying its role in bone metabolism remain unclear. We found that CD44 expression was upregulated during osteoclastogenesis. CD44 deficiency in vitro significantly inhibited osteoclast activity and function by regulating the NF-κB/NFATc1-mediated pathway. In vivo, CD44 mRNA levels were significantly upregulated in osteoclasts isolated from the hindlimb of tail-suspended mice. CD44 deficiency can reduce osteoclast activity and counteract cortical bone loss in the hindlimb of unloaded mice. These results suggest that therapeutic inhibition of CD44 may protect from unloading induced bone loss by inhibiting osteoclast activity. PMID:26530337

  9. Guided bone regeneration (GBR) using cortical bone pins in combination with leukocyte- and platelet-rich fibrin (L-PRF).

    PubMed

    Toffler, Michael

    2014-03-01

    Two of the fundamental requisites for guided bone regeneration (GBR) are space maintenance and primary soft-tissue closure. Allogeneic cortical bone pins measuring 2 mm in diameter in customized lengths can protect surrounding graft materials, support bioresorbable membrane barriers, and resist wound compression from the overlying soft tissues. In addition, a second-generation platelet concentrate, leukocyte- and platelet-rich fibrin (L-PRF), may be incorporated into the augmentation procedure to provide multiple growth factors, accelerate wound healing, and aid in the maintenance of primary closure over the grafted materials. Highlighting two case reports, this article features a GBR technique that uses bone pins in combination with L-PRF membranes to provide both horizontal and vertical ridge augmentation at severely compromised implant sites.

  10. Linear measurements of cortical bone and dental enamel by computed tomography: applications and problems.

    PubMed

    Spoor, C F; Zonneveld, F W; Macho, G A

    1993-08-01

    This paper explores the potential of high-resolution computed tomography (CT) as a morphometric tool in paleoanthropology. The accuracy of linear measurements of enamel thickness and cortical bone thickness taken from CT scans is evaluated by making comparison with measurements taken directly from physical sections. The measurements of cortical bone are taken on extant and fossil specimens with and without attached matrix, and the dental specimens studied include a sample of 12 extant human molars. Local CT numbers (representing X-ray attenuation) are used to determine the exact position of the boundaries of a structure. Using this technique most studied dimensions, including four of human molar enamel thickness, could be obtained from CT scans with a maximum error range of +/- 0.1 mm. The limitations of the method are discussed with special reference to problems associated with highly mineralized fossils.

  11. Cortical and trabecular bone mineral loss from the spine and hip in long-duration spaceflight.

    PubMed

    Lang, Thomas; LeBlanc, Adrian; Evans, Harlan; Lu, Ying; Genant, Harry; Yu, Alice

    2004-06-01

    We measured cortical and trabecular bone loss using QCT of the spine and hip in 14 crewmembers making 4- to 6-month flights on the International Space Station. There was no compartment-specific loss of bone in the spine. Cortical bone mineral loss in the hip occurred primarily by endocortical thinning. In an earlier study, areal BMD (aBMD) measurements by DXA showed that cosmonauts making flights of 4- to 12-month duration on the Soviet/Russian MIR spacecraft lost bone at an average rate of 1%/month from the spine and 1.5%/month from the hip. However, because DXA measurements represent the sum of the cortical and trabecular compartments, there is no direct information on how these bone envelopes are affected by spaceflight. To address this, we performed a study of crewmembers (13 males and 1 female; age range, 40-55 years) on long-duration missions (4-6 months) on the International Space Station (ISS). We used DXA to obtain aBMD of the hip and spine and volumetric QCT (vQCT) to assess integral, cortical, and trabecular volumetric BMD (vBMD) in the hip and spine. In the heel, DXA was used to measure aBMD, and quantitative ultrasound (QUS) was used to measure speed of sound (SOS) and broadband ultrasound attenuation (BUA). aBMD was lost at rates of 0.9%/month at the spine (p < 0.001) and 1.4-1.5%/month at the hip (p < 0.001). Spinal integral vBMD was lost at a rate of 0.9%/month (p < 0.001), and trabecular vBMD was lost at 0.7%/month (p < 0.05). In contrast to earlier reports, these changes were generalized across the vertebrae and not focused in the posterior elements. In the hip, integral, cortical, and trabecular vBMD was lost at rates of 1.2-1.5%/month (p < 0.0001), 0.4-0.5%/month (p < 0.01), and 2.2-2.7%/month (p < 0.001), respectively. The cortical bone loss in the hip occurred primarily by cortical thinning. Calcaneal aBMD measurements by DXA showed smaller mean losses (0.4%/month) than hip or spine measurements, with SOS and BUA showing no change. In summary

  12. Micropillar fabrication on bovine cortical bone by direct-write femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Lim, Yong C.; Altman, Katrina J.; Farson, Dave F.; Flores, Katharine M.

    2009-11-01

    We investigated fabrication of cylindrical micropillars on bovine cortical bone using direct-write femtosecond laser ablation. The ablation threshold of the material was measured by single-pulse ablation tests, and the incubation coefficient was measured from linear scanned ablation tests. A motion system was programmed to apply multiple layers of concentric rings of pulses to machine pillars of various diameters and heights. The diameter of the top surface of the pillar was found to steadily decrease due to incubation of damage from successive layers of pulses during the machining process. Pillar top diameter was predicted based on a paraxial beam fluence approximation and single-pulse ablation threshold and incubation coefficient measurements. Pillar diameters predicted as successive layers of pulses were applied were well-matched to experiments, confirming that femtosecond laser ablation of the cortical bone was well-modeled by single-pulse ablation threshold measurements and an incubation coefficient.

  13. Measurement of the microstructural fracture toughness of cortical bone using indentation fracture.

    PubMed

    Mullins, L P; Bruzzi, M S; McHugh, P E

    2007-01-01

    The purpose of this work is to investigate the use of indentation fracture as a method of measuring toughness at the microscale in cortical bone. Indentation fracture employs sharp indenters to initiate cracks, whose length can be used to calculate the toughness of the material. Only a cube corner indenter tip is found to initiate cracks at a suitable size scale for microstructural measurement. Cracks from 7 to 56 microm in length are produced using loads from 0.05 to 3N. Preliminary data predicts rising toughness with increasing crack length (rising R-curve behaviour) at the microscale. This technique provides a new insight into fracture in cortical bone since it allows the investigator to observe mechanisms and measure toughness at a size scale at which in vivo damage is known to exist.

  14. Design and validation of bending test method for characterization of miniature pediatric cortical bone specimens.

    PubMed

    Albert, Carolyne I; Jameson, John; Harris, Gerald

    2013-02-01

    Osteogenesis imperfecta is a genetic disorder of bone fragility; however, the effects of this disorder on bone material properties are not well understood. No study has yet measured bone material strength in humans with osteogenesis imperfecta. Small bone specimens are often extracted during routine fracture surgeries in children with osteogenesis imperfecta. These specimens could provide valuable insight into the effects of osteogenesis imperfecta on bone material strength; however, their small size poses a challenge to their mechanical characterization. In this study, a validated miniature three-point bending test is described that enables measurement of the flexural material properties of pediatric cortical osteotomy specimens as small as 5 mm in length. This method was validated extensively using bovine bone, and the effect of span/depth aspect ratio (5 vs 6) on the measured flexural properties was examined. The method provided reasonable results for both Young's modulus and flexural strength in bovine bone. With a span/depth ratio of 6, the median longitudinal modulus and flexural strength results were 16.1 (range: 14.4-19.3)GPa and 251 (range: 219-293)MPa, respectively. Finally, the pilot results from two osteotomy specimens from children with osteogenesis imperfecta are presented. These results provide the first measures of bone material strength in this patient population.

  15. The Effect of Osteoporosis Treatments on Fatigue Properties of Cortical Bone Tissue.

    PubMed

    Brock, Garry R; Chen, Julia T; Ingraffea, Anthony R; MacLeay, Jennifer; Pluhar, G Elizabeth; Boskey, Adele L; van der Meulen, Marjolein C H

    2015-06-01

    Bisphosphonates are commonly prescribed for treatment of osteoporosis. Long-term use of bisphosphonates has been correlated to atypical femoral fractures (AFF). AFFs arise from fatigue damage to bone tissue that cannot be repaired due to pharmacologic treatments. Despite fatigue being the primary damage mechanism of AFFs, the effects of osteoporosis treatments on fatigue properties of cortical bone are unknown. To examine if fatigue-life differences occur in bone tissue after different pharmacologic treatments for osteoporosis, we tested bone tissue from the femurs of sheep given a metabolic acidosis diet to induce osteoporosis, followed by treatment with a selective estrogen reception modulator (raloxifene), a bisphosphonate (alendronate or zoledronate), or parathyroid hormone (teriparatide, PTH). Beams of cortical bone tissue were created and tested in four-point bending fatigue to failure. Tissues treated with alendronate had reduced fatigue life and less modulus loss at failure compared to other treatments, while tissue treated with PTH had a prolonged fatigue life. No loss of fatigue life occurred with zoledronate treatment despite its greater binding affinity and potency compared to alendronate. Tissue mineralization measured by microCT did not explain the differences seen in fatigue behavior. Increased fatigue life with PTH suggests that current treatment methods for AFF could have beneficial effects for restoring fatigue life. These results indicate that fatigue life differs with each type of osteoporosis treatment.

  16. Effect of Aging on the Toughness of Human Cortical Bone: Evaluation by R-Curves

    SciTech Connect

    Kinney, J

    2004-10-08

    Age-related deterioration of the fracture properties of bone, coupled with increased life expectancy, are responsible for increasing incidence of bone fracture in the elderly, and hence, an understanding of how its fracture properties degrade with age is essential. The present study describes ex vivo fracture experiments to quantitatively assess the effect of aging on the fracture toughness properties of human cortical bone in the longitudinal direction. Because cortical bone exhibits rising crack-growth resistance with crack extension, unlike most previous studies the toughness is evaluated in terms of resistance-curve (R-curve) behavior, measured for bone taken from wide range of age groups (34-99 years). Using this approach, both the ex vivo crack-initiation and crack-growth toughness are determined and are found to deteriorate with age; the initiation toughness decreases some 40% over six decades from 40 to 100 years, while the growth toughness is effectively eliminated over the same age range. The reduction in crack-growth toughness is considered to be associated primarily with a degradation in the degree of extrinsic toughening, in particular involving crack bridging in the wake of the crack.

  17. Effects of cortical bone perforation on periosteal distraction: an experimental study in the rabbit mandible.

    PubMed

    Oda, Tomoo; Kinoshita, Kazuhiko; Ueda, Minoru

    2009-07-01

    To investigate tissue reactions using periosteal distraction with decorticating holes in a rabbit model. Twenty-five Japanese white rabbits weighing 3.2 to 3.7 kg were used. The periosteum was carefully detached, and the buccal cortical bone was porously perforated by drilling in the decortication group. Titanium mesh was placed between the periosteum and the cortical bone, with or without holes. A distraction screw was placed rigidly under the center of the mesh. After a 7-day latency period, the periosteum was distracted 0.5 mm per day for 8 consecutive days. Rabbits were sacrificed after consolidation periods of 4 and 8 weeks. Cross-sectional radiographs were evaluated with densitometry. Specimens were fixed, decalcified, and stained with hematoxylin and eosin. At 8 weeks after periosteal distraction, the area of new bone formation averaged 25.7 +/- 5.1 mm2 and 12.9 +/- 3.2 mm2 (mean +/- SD) with and without decortication, respectively. In this study, periosteal distraction showed better bone regeneration on the lateral aspect of mandibles with rather than without decorticating holes. Periosteal distraction with decorticating holes can be effective in augmenting atrophic bone.

  18. Effect of surface topography on removal of cortical bone screws in a novel sheep model.

    PubMed

    Pearce, Alexandra I; Pearce, Simon G; Schwieger, Karsten; Milz, Stefan; Schneider, Erich; Archer, Charles W; Richards, R Goeff

    2008-10-01

    Difficulty in removing implants used in trauma patients can be a complication, and increased bone-implant adhesion likely is a major contributing factor. In vitro studies have shown that surface morphology of implant materials has the ability to influence cellular responses, with polished surfaces decreasing the potential for mineralization. This study examined the effect of polishing commercially pure titanium (cpTi) and the titanium alloy TAN on the removal torque and percentage bone-implant contact in cortical and cancellous bone of sheep. Polishing had a significant effect on both removal torque and percentage bone-implant contact, with the polished implants demonstrating a lower removal torque in both cortical and cancellous bone. Polished cpTi and stainless steel were similar in terms of surface roughness and removal torque. However, polished TAN, which was not as smooth as polished cpTi, did not show the same low level for reducing removal torque. Improved polishing of TAN should reduce the removal torque further. The results of the study show that polishing is promising in improving the ease of implant removal after fracture fixation and repair.

  19. Effect of aging on the toughness of human cortical bone:Evaluation by R-curves

    SciTech Connect

    Nalla, Ravi K.; Kruzic, Jamie J.; Kinney, John H.; Ritchie,Robert O.

    2005-04-05

    Age-related deterioration of the fracture properties of bone, coupled with increased life expectancy, is responsible for increasing incidence of bone fracture in the elderly, and hence, an understanding of how its fracture properties degrade with age is essential. The present study describes ex vivo fracture experiments to quantitatively assess the effect of aging on the fracture toughness properties of human cortical bone in the longitudinal direction. Because cortical bone exhibits rising crack-growth resistance with crack extension, unlike most previous studies, the toughness is evaluated in terms of resistance-curve (R-curve) behavior, measured for bone taken from wide range of age groups (34-99 years). Using this approach, both the ex vivo crack-initiation and crack-growth toughness are determined and are found to deteriorate with age; the initiation toughness decreases some 40 percent over 6 decades from 40 to 100 years, while the growth toughness is effectively eliminated over the same age range. The reduction in crack-growth toughness is considered to be associated primarily with a degradation in the degree of extrinsic toughening, in particular, involving crack bridging in the wake of the crack.

  20. Effect of cortical thickness and cancellous bone density on the holding strength of internal fixator screws.

    PubMed

    Seebeck, J; Goldhahn, J; Städele, H; Messmer, P; Morlock, M M; Schneider, E

    2004-11-01

    Internal fixators are a new class of implants designed to preserve the periosteal blood supply of the bone. In contrast to conventional plate fixation in which the screws have spherical heads and are loaded mainly by axial pullout forces, screws in internal fixators are "locked" within the plate and therefore subjected to axial as well as bending loads. In this study the ultimate loads of screws of a commercially available internal fixator system were tested in a pullout (n = 72) and cantilever bending mode (n = 72) in metaphyseal and diaphyseal regions of four pairs of human tibiae with different bone qualities. Cortical thickness and cancellous bone density were determined at the screw insertion sites. Stepwise multiple linear regression revealed that cortical thickness and cancellous density can explain 93% and 98% of the variance of the ultimate load of the screws in an axial pullout and cantilever bending mode. Screws in internal fixators are better suited to transmit shear forces and thereby make better use of the strength potential of bone than screws used in conventional plate fixation: this is especially advantageous when bone strength is reduced, e.g. due to osteoporosis.

  1. Qualitative and quantitative ultrashort echo time (UTE) imaging of cortical bone

    NASA Astrophysics Data System (ADS)

    Du, Jiang; Carl, Michael; Bydder, Mark; Takahashi, Atsushi; Chung, Christine B.; Bydder, Graeme M.

    2010-12-01

    We describe the use of two-dimensional ultrashort echo time (2D UTE) sequences with minimum TEs of 8 μs to image and quantify cortical bone on a clinical 3T scanner. An adiabatic inversion pulse was used for long T2 water and fat signal suppression. Adiabatic inversion prepared UTE acquisitions with varying TEs were used for T2∗ measurement. Saturation recovery UTE acquisitions were used for T1 measurement. Bone water concentration was measured with the aid of an external reference phantom. UTE techniques were evaluated on cadaveric specimens and healthy volunteers. A signal-to-noise ratio of around 30, contrast-to-noise ratio of around 27/20 between bone and muscle/fat were achieved in tibia in vivo with a nominal voxel size of 0.23 × 0.23 × 6.0 mm 3 in a scan time of 5 min. A mean T1 of 223 ± 11 ms and mean T2∗ of 390 ± 19 μs were found. Mean bone water concentrations of 23.3 ± 1.6% with UTE and 21.7 ± 1.3% with adiabatic inversion prepared UTE sequences were found in tibia in five normal volunteers. The results show that in vivo qualitative and quantitative evaluation of cortical bone is feasible with 2D UTE sequences.

  2. Variability in reference point microindentation and recommendations for testing cortical bone: location, thickness and orientation heterogeneity.

    PubMed

    Coutts, L V; Jenkins, T; Li, T; Dunlop, D G; Oreffo, R O C; Cooper, C; Harvey, N C; Thurner, P J

    2015-06-01

    Reference Point Indentation (RPI) has been proposed as a new clinical tool to aid the diagnosis of Osteoporosis. This study has examined the performance of the tool within entire femurs to improve the understanding of the mechanical properties of bone and also to guide future RPI testing to optimize repeatability of results obtained using the technique. Human, bovine, porcine and rat femurs were indented along three longitudinal axes: anterior and posterior: medial and lateral as well as around the circumference of the femoral head and neck. Cortical and subchondral bone thickness was measured using CT and radiography. The study shows that in some samples, bone is too thin to support the high loads applied with the technique and in these cases, RPI values are highly influenced by thickness. The technique will be useful in the mid-shaft region where cortical thickness is greatest, providing previously established guidelines are followed to optimize measurement repeatability, including performing multiple measurements per sample and investigating multiple samples. The study has also provided evidence that RPI values vary significantly with test site, hence mechanical properties should not be inferred from RPI findings alone away from the test site, even within the same bone. In conclusion, RPI appears to be a useful tool for scientific investigation; however further work is required to examine the feasibility of using RPI for assessing differences between healthy and diseased bone in a clinical setting.

  3. Effect of aging on the toughness of human cortical bone: evaluation by R-curves.

    PubMed

    Nalla, R K; Kruzic, J J; Kinney, J H; Ritchie, R O

    2004-12-01

    Age-related deterioration of the fracture properties of bone, coupled with increased life expectancy, is responsible for increasing incidence of bone fracture in the elderly, and hence, an understanding of how its fracture properties degrade with age is essential. The present study describes ex vivo fracture experiments to quantitatively assess the effect of aging on the fracture toughness properties of human cortical bone in the longitudinal direction. Because cortical bone exhibits rising crack-growth resistance with crack extension, unlike most previous studies, the toughness is evaluated in terms of resistance-curve (R-curve) behavior, measured for bone taken from wide range of age groups (34-99 years). Using this approach, both the ex vivo crack-initiation and crack-growth toughness are determined and are found to deteriorate with age; the initiation toughness decreases some 40% over 6 decades from 40 to 100 years, while the growth toughness is effectively eliminated over the same age range. The reduction in crack-growth toughness is considered to be associated primarily with a degradation in the degree of extrinsic toughening, in particular, involving crack bridging in the wake of the crack.

  4. Towards assessing cortical bone porosity using low-frequency quantitative acoustics: A phantom-based study.

    PubMed

    Vogl, Florian; Bernet, Benjamin; Bolognesi, Daniele; Taylor, William R

    2017-01-01

    Cortical porosity is a key characteristic governing the structural properties and mechanical behaviour of bone, and its quantification is therefore critical for understanding and monitoring the development of various bone pathologies such as osteoporosis. Axial transmission quantitative acoustics has shown to be a promising technique for assessing bone health in a fast, non-invasive, and radiation-free manner. One major hurdle in bringing this approach to clinical application is the entanglement of the effects of individual characteristics (e.g. geometry, porosity, anisotropy etc.) on the measured wave propagation. In order to address this entanglement problem, we therefore propose a systematic bottom-up approach, in which only one bone property is varied, before addressing interaction effects. This work therefore investigated the sensitivity of low-frequency quantitative acoustics to changes in porosity as well as individual pore characteristics using specifically designed cortical bone phantoms. 14 bone phantoms were designed with varying pore size, axial-, and radial pore number, resulting in porosities (bone volume fraction) between 0% and 15%, similar to porosity values found in human cortical bone. All phantoms were manufactured using laser sintering, measured using axial-transmission acoustics and analysed using a full-wave approach. Experimental results were compared to theoretical predictions based on a modified Timoshenko theory. A clear dependence of phase velocity on frequency and porosity produced by increasing pore size or radial pore number was demonstrated, with the velocity decreasing by between 2-5 m/s per percent of additional porosity, which corresponds to -0.5% to -1.0% of wave speed. While the change in phase velocity due to axial pore number was consistent with the results due to pore size and radial pore number, the relative uncertainties for the estimates were too high to draw any conclusions for this parameter. This work has shown the

  5. Differential β3 and β1 Integrin Expression in Bone Marrow and Cortical Bone of Estrogen Deficient Rats.

    PubMed

    Voisin, Muriel; McNamara, Laoise M

    2015-09-01

    Integrin-based (β3 ) attachments to the extracellular matrix (ECM) on osteocyte cell processes have recently been proposed to play an important role in facilitating osteocyte mechanosensation. However, it is not yet known whether integrin expression is altered in the mechanoregulatory osteocytes during osteoporosis. The objective of this study was to test the hypothesis that the expression of integrin-based mechanosensory complexes (β1 and β3 integrins) is altered as a direct response to estrogen deficiency, in an estrogen deficient animal model of osteoporosis. Four weeks post-operatively, immunohistochemistry was used to detect for β1 and β3 integrin subunits in bone tissue and marrow of ovariectomized (OVX; N = 4) and SHAM (N = 4) operated animals. A tartrate resistant acid phosphatase (TRAP) control stain was performed to quantify the presence of osteoclasts in the bone marrow and bone surfaces. Image analysis was performed to quantify expression patterns in different biological compartments, that is, bone marrow, endosteum, and cortical bone. Our results showed that β1 integrins were ubiquitously expressed throughout the bone and marrow, for both OVX and SHAM groups. β3 integrin subunit expression was lower in bone cells from osteoporotic animals compared to controls, whereas β3 expression in marrow cells did not differ significantly between groups. At the endosteum no difference was observed in β3 integrin subunit expression. As expected, the number of osteoclasts was higher in the OVX group validating an imbalance in bone remodeling. We propose that a reduction in β3 integrin expression in osteocytes might impair mechanosensation by bone cells during estrogen deficiency.

  6. Cortical Bone Water: In Vivo Quantification with Ultrashort Echo-Time MR Imaging1

    PubMed Central

    Techawiboonwong, Aranee; Song, Hee Kwon; Leonard, Mary B.; Wehrli, Felix W.

    2008-01-01

    Purpose: To develop and evaluate a method based on ultrashort echo-time radial magnetic resonance (MR) imaging to quantify bone water (BW) concentration as a new metric of bone quality in human cortical bone in vivo. Materials and Methods: Human subject studies were institutional review board approved and HIPAA compliant; informed consent was obtained. Cortical BW concentration was determined with custom-designed MR imaging sequences at 3.0 T and was validated in sheep and human cortical bone by using exchange of native water with deuterium oxide (D2O). The submillisecond T2* of BW requires correction for relaxation losses during the radiofrequency pulse. BW was measured at the tibial midshaft in healthy pre- and postmenopausal women (mean age, 34.6 and 69.4 years, respectively; n = 5 in each group) and in patients receiving maintenance hemodialysis (mean age, 51.8 years; n = 6) and was compared with bone mineral density (BMD) at the same site at peripheral quantitative computed tomography, as well as with BMD of the lumbar spine and hip at dual x-ray absorptiometry. Data were analyzed by using the Pearson correlation coefficient and two-sided t tests as appropriate. Results: Excellent agreement was obtained ex vivo between the water displaced by using D2O exchange and water measured with respect to a reference sample (r2 = 0.99, P < .001). In vivo, BW in the postmenopausal group was greater by 65% (28.7% ± 1.3 [standard deviation] vs 17.4% ± 2.2, P < .001) than in the premenopausal group, and patients with renal osteodystrophy had higher BW (41.4% ± 9.6) than the premenopausal group by 135% (P < .001) and the postmenopausal group by 43% (P = .02). BMD showed an opposite behavior, with much smaller group differences. Because the majority of BW is in the pore system of cortical bone, this parameter provides a surrogate measure for cortical porosity. Conclusion: A new MR imaging–based method for quantifying BW noninvasively has been demonstrated. © RSNA, 2008

  7. The resistance of cortical bone tissue to failure under cyclic loading is reduced with alendronate.

    PubMed

    Bajaj, Devendra; Geissler, Joseph R; Allen, Matthew R; Burr, David B; Fritton, J C

    2014-07-01

    Bisphosphonates are the most prescribed preventative treatment for osteoporosis. However, their long-term use has recently been associated with atypical fractures of cortical bone in patients who present with low-energy induced breaks of unclear pathophysiology. The effects of bisphosphonates on the mechanical properties of cortical bone have been exclusively studied under simple, monotonic, quasi-static loading. This study examined the cyclic fatigue properties of bisphosphonate-treated cortical bone at a level in which tissue damage initiates and is accumulated prior to frank fracture in low-energy situations. Physiologically relevant, dynamic, 4-point bending applied to beams (1.5 mm × 0.5 mm × 10 mm) machined from dog rib (n=12/group) demonstrated mechanical failure and micro-architectural features that were dependent on drug dose (3 groups: 0, 0.2, 1.0mg/kg/day; alendronate [ALN] for 3 years) with cortical bone tissue elastic modulus (initial cycles of loading) reduced by 21% (p<0.001) and fatigue life (number of cycles to failure) reduced in a stress-life approach by greater than 3-fold with ALN1.0 (p<0.05). While not affecting the number of osteons, ALN treatment reduced other features associated with bone remodeling, such as the size of osteons (-14%; ALN1.0: 10.5±1.8, VEH: 12.2±1.6, ×10(3) μm2; p<0.01) and the density of osteocyte lacunae (-20%; ALN1.0: 11.4±3.3, VEH: 14.3±3.6, ×10(2) #/mm2; p<0.05). Furthermore, the osteocyte lacunar density was directly proportional to initial elastic modulus when the groups were pooled (R=0.54, p<0.01). These findings suggest that the structural components normally contributing to healthy cortical bone tissue are altered by high-dose ALN treatment and contribute to reduced mechanical properties under cyclic loading conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Automated classification of mandibular cortical bone on dental panoramic radiographs for early detection of osteoporosis

    NASA Astrophysics Data System (ADS)

    Horiba, Kazuki; Muramatsu, Chisako; Hayashi, Tatsuro; Fukui, Tatsumasa; Hara, Takeshi; Katsumata, Akitoshi; Fujita, Hiroshi

    2015-03-01

    Findings on dental panoramic radiographs (DPRs) have shown that mandibular cortical index (MCI) based on the morphology of mandibular inferior cortex was significantly correlated with osteoporosis. MCI on DPRs can be categorized into one of three groups and has the high potential for identifying patients with osteoporosis. However, most DPRs are used only for diagnosing dental conditions by dentists in their routine clinical work. Moreover, MCI is not generally quantified but assessed subjectively. In this study, we investigated a computer-aided diagnosis (CAD) system that automatically classifies mandibular cortical bone for detection of osteoporotic patients at early stage. First, an inferior border of mandibular bone was detected by use of an active contour method. Second, regions of interest including the cortical bone are extracted and analyzed for its thickness and roughness. Finally, support vector machine (SVM) differentiate cases into three MCI categories by features including the thickness and roughness. Ninety eight DPRs were used to evaluate our proposed scheme. The number of cases classified to Class I, II, and III by a dental radiologist are 56, 25 and 17 cases, respectively. Experimental result based on the leave-one-out cross-validation evaluation showed that the sensitivities for the classes I, II, and III were 94.6%, 57.7% and 94.1%, respectively. Distribution of the groups in the feature space indicates a possibility of MCI quantification by the proposed method. Therefore, our scheme has a potential in identifying osteoporotic patients at an early stage.

  9. Use of Cortical Bone Screws in Maxillofacial Surgery - A Prospective Study

    PubMed Central

    Satish, Madatanapalli; Rahman, NM Mujeeb; Reddy, V Sridhar; Yuvaraj, A; Muliyar, Sabir; Razak, P Abdul

    2014-01-01

    Background: The aim of this study is to evaluate the various applications of cortical bone screws in oral and maxillofacial surgery. Materials & Methods: The study was conducted in a teaching hospital located in, Bangalore, India, on 20 patients. These patients were categorized into three groups depending on the applications of these screws like, for achieving intermaxillary fixation in Group-1, for treatment of simple, undisplaced fractures by “Tension wire” method in Group-2, and further application of these screws were evaluated in Group-3. Different parameters were used to evaluate the efficacy of these screws. Results: In Group-1(n=12) there was satisfactory occlusion in all the patients with minimal incidence of complications. In Group-2 (n=4) post-operative reduction and fixation was satisfactory and in Group-3 (n=4) the function of these screws was satisfactory when it was used for vestibuloplasty and also as a suspension wiring in treatment of comminuted fracture of zygoma with minimal incidence of complications. Conclusion: Use of cortical bone screws is a valid alternative for achieving intermaxillary fixation, reduction and fixation of simple, undisplaced or minimally displaced fractures through Tension wire method owing to its simplicity, economy and ease of use, and as a fixation method for apically positioned flap in vestibuloplasty procedure. How to cite the article: Satish M, Rahman NM, Reddy VS, Yuvaraj A, Muliyar S, Razak PA. Use of Cortical Bone Screws in Maxillofacial Surgery - A Prospective Study. J Int Oral Health 2014;6(2):62-7. PMID:24876704

  10. Effects of fatigue induced damage on the longitudinal fracture resistance of cortical bone.

    PubMed

    Fletcher, Lloyd; Codrington, John; Parkinson, Ian

    2014-07-01

    As a composite material, cortical bone accumulates fatigue microdamage through the repetitive loading of everyday activity (e.g. walking). The accumulation of fatigue microdamage is thought to contribute to the occurrence of fragility fractures in older people. Therefore it is beneficial to understand the relationship between microcrack accumulation and the fracture resistance of cortical bone. Twenty longitudinally orientated compact tension fracture specimens were machined from a single bovine femur, ten specimens were assigned to both the control and fatigue damaged groups. The damaged group underwent a fatigue loading protocol to induce microdamage which was assessed via fluorescent microscopy. Following fatigue loading, non-linear fracture resistance tests were undertaken on both the control and damaged groups using the J-integral method. The interaction of the crack path with the fatigue induced damage and inherent toughening mechanisms were then observed using fluorescent microscopy. The results of this study show that fatigue induced damage reduces the initiation toughness of cortical bone and the growth toughness within the damage zone by three distinct mechanisms of fatigue-fracture interaction. Further analysis of the J-integral fracture resistance showed both the elastic and plastic component were reduced in the damaged group. For the elastic component this was attributed to a decreased number of ligament bridges in the crack wake while for the plastic component this was attributed to the presence of pre-existing fatigue microcracks preventing energy absorption by the formation of new microcracks.

  11. Intrinsic mechanical behavior of femoral cortical bone in young, osteoporotic and bisphosphonate-treated individuals in low- and high energy fracture conditions

    DOE PAGES

    Zimmermann, Elizabeth A.; Schaible, Eric; Gludovatz, Bernd; ...

    2016-02-16

    Bisphosphonates are a common treatment to reduce osteoporotic fractures. This treatment induces osseous structural and compositional changes accompanied by positive effects on osteoblasts and osteocytes. Here, we test the hypothesis that restored osseous cell behavior, which resembles characteristics of younger, healthy cortical bone, leads to improved bone quality. Microarchitecture and mechanical properties of young, treatment-naïve osteoporosis, and bisphosphonate-treated cases were investigated in femoral cortices. Tissue strength was measured using three-point bending. Collagen fibril-level deformation was assessed in non-traumatic and traumatic fracture states using synchrotron small-angle x-ray scattering (SAXS) at low and high strain rates. The lower modulus, strength and fibrilmore » deformation measured at low strain rates reflects susceptibility for osteoporotic low-energy fragility fractures. Independent of age, disease and treatment status, SAXS revealed reduced fibril plasticity at high strain rates, characteristic of traumatic fracture. We find the significantly reduced mechanical integrity in osteoporosis may originate from porosity and alterations to the intra/extrafibrillar structure, while the fibril deformation under treatment indicates improved nano-scale characteristics. In conclusion, losses in strength and fibril deformation at low strain rates correlate with the occurrence of fragility fractures in osteoporosis, while improvements in structural and mechanical properties following bisphosphonate treatment may foster resistance to fracture during physiological strain rates.« less

  12. Intrinsic mechanical behavior of femoral cortical bone in young, osteoporotic and bisphosphonate-treated individuals in low- and high energy fracture conditions

    SciTech Connect

    Zimmermann, Elizabeth A.; Schaible, Eric; Gludovatz, Bernd; Schmidt, Felix N.; Riedel, Christoph; Krause, Matthias; Vettorazzi, Eik; Acevedo, Claire; Hahn, Michael; Püschel, Klaus; Tang, Simon; Amling, Michael; Ritchie, Robert O.; Busse, Björn

    2016-02-16

    Bisphosphonates are a common treatment to reduce osteoporotic fractures. This treatment induces osseous structural and compositional changes accompanied by positive effects on osteoblasts and osteocytes. Here, we test the hypothesis that restored osseous cell behavior, which resembles characteristics of younger, healthy cortical bone, leads to improved bone quality. Microarchitecture and mechanical properties of young, treatment-naïve osteoporosis, and bisphosphonate-treated cases were investigated in femoral cortices. Tissue strength was measured using three-point bending. Collagen fibril-level deformation was assessed in non-traumatic and traumatic fracture states using synchrotron small-angle x-ray scattering (SAXS) at low and high strain rates. The lower modulus, strength and fibril deformation measured at low strain rates reflects susceptibility for osteoporotic low-energy fragility fractures. Independent of age, disease and treatment status, SAXS revealed reduced fibril plasticity at high strain rates, characteristic of traumatic fracture. We find the significantly reduced mechanical integrity in osteoporosis may originate from porosity and alterations to the intra/extrafibrillar structure, while the fibril deformation under treatment indicates improved nano-scale characteristics. In conclusion, losses in strength and fibril deformation at low strain rates correlate with the occurrence of fragility fractures in osteoporosis, while improvements in structural and mechanical properties following bisphosphonate treatment may foster resistance to fracture during physiological strain rates.

  13. Intrinsic mechanical behavior of femoral cortical bone in young, osteoporotic and bisphosphonate-treated individuals in low- and high energy fracture conditions

    NASA Astrophysics Data System (ADS)

    Zimmermann, Elizabeth A.; Schaible, Eric; Gludovatz, Bernd; Schmidt, Felix N.; Riedel, Christoph; Krause, Matthias; Vettorazzi, Eik; Acevedo, Claire; Hahn, Michael; Püschel, Klaus; Tang, Simon; Amling, Michael; Ritchie, Robert O.; Busse, Björn

    2016-02-01

    Bisphosphonates are a common treatment to reduce osteoporotic fractures. This treatment induces osseous structural and compositional changes accompanied by positive effects on osteoblasts and osteocytes. Here, we test the hypothesis that restored osseous cell behavior, which resembles characteristics of younger, healthy cortical bone, leads to improved bone quality. Microarchitecture and mechanical properties of young, treatment-naïve osteoporosis, and bisphosphonate-treated cases were investigated in femoral cortices. Tissue strength was measured using three-point bending. Collagen fibril-level deformation was assessed in non-traumatic and traumatic fracture states using synchrotron small-angle x-ray scattering (SAXS) at low and high strain rates. The lower modulus, strength and fibril deformation measured at low strain rates reflects susceptibility for osteoporotic low-energy fragility fractures. Independent of age, disease and treatment status, SAXS revealed reduced fibril plasticity at high strain rates, characteristic of traumatic fracture. The significantly reduced mechanical integrity in osteoporosis may originate from porosity and alterations to the intra/extrafibrillar structure, while the fibril deformation under treatment indicates improved nano-scale characteristics. In conclusion, losses in strength and fibril deformation at low strain rates correlate with the occurrence of fragility fractures in osteoporosis, while improvements in structural and mechanical properties following bisphosphonate treatment may foster resistance to fracture during physiological strain rates.

  14. Intrinsic mechanical behavior of femoral cortical bone in young, osteoporotic and bisphosphonate-treated individuals in low- and high energy fracture conditions

    PubMed Central

    Zimmermann, Elizabeth A.; Schaible, Eric; Gludovatz, Bernd; Schmidt, Felix N.; Riedel, Christoph; Krause, Matthias; Vettorazzi, Eik; Acevedo, Claire; Hahn, Michael; Püschel, Klaus; Tang, Simon; Amling, Michael; Ritchie, Robert O.; Busse, Björn

    2016-01-01

    Bisphosphonates are a common treatment to reduce osteoporotic fractures. This treatment induces osseous structural and compositional changes accompanied by positive effects on osteoblasts and osteocytes. Here, we test the hypothesis that restored osseous cell behavior, which resembles characteristics of younger, healthy cortical bone, leads to improved bone quality. Microarchitecture and mechanical properties of young, treatment-naïve osteoporosis, and bisphosphonate-treated cases were investigated in femoral cortices. Tissue strength was measured using three-point bending. Collagen fibril-level deformation was assessed in non-traumatic and traumatic fracture states using synchrotron small-angle x-ray scattering (SAXS) at low and high strain rates. The lower modulus, strength and fibril deformation measured at low strain rates reflects susceptibility for osteoporotic low-energy fragility fractures. Independent of age, disease and treatment status, SAXS revealed reduced fibril plasticity at high strain rates, characteristic of traumatic fracture. The significantly reduced mechanical integrity in osteoporosis may originate from porosity and alterations to the intra/extrafibrillar structure, while the fibril deformation under treatment indicates improved nano-scale characteristics. In conclusion, losses in strength and fibril deformation at low strain rates correlate with the occurrence of fragility fractures in osteoporosis, while improvements in structural and mechanical properties following bisphosphonate treatment may foster resistance to fracture during physiological strain rates. PMID:26879146

  15. Relationships between cortical bone properties and head wave ultrasonic velocity at 1 MHz: An in vitro investigation

    NASA Astrophysics Data System (ADS)

    Bossy, Emmanuel; Talmant, Maryline; Peyrin, Françoise; Cloetens, Peter; Akrout, Leila; Laugier, Pascal

    2003-10-01

    The axial transmission technique provides a measurement of the velocity (SOS) of elastic waves propagating along the surface of cortical bone. Currently, SOS is derived from the time of flight of the first arriving signal. Our goal was to investigate the relationship between SOS and several bone properties that independently contribute to bone strength. One-MHz SOS measurements were performed with a proprietary probe on 41 excised human radius with soft tissue removed. Small pieces of cortical bone were removed from the site of ultrasonic testing to be investigated using synchrotron radiation microtomography (resolution 10 μm). Cortical thickness, cortical porosity, and tissue mineralization were derived from the 3-D data set. Mean SOS values were 3940 (3796-4120) ms-1. The reproducibility of the SOS measurements expressed as a variation coefficient (CV) was 0.5%. The relationships between SOS and bone properties were assessed using linear regression and displayed significant correlations : R2=0.20 (p<10-5) for cortical thickness, R2=0.30 (p<10-3) for cortical porosity, R2=0.37 (p<10-4) for tissue mineralization. A multiple regression analysis showed that cortical porosity and tissue mineralization in the periosteal region were the most predictive variables and explained 60% of the total variance of the SOS. These results are in agreement with predictions obtained using 3-D numerical computations based on a finite-difference method.

  16. Influence of bacterial strains on bone infection.

    PubMed

    Cordero, J; Munuera, L; Folgueira, M D

    1996-07-01

    Experiments were performed on 120 rabbits to compare the probability of infection after bone surgery without an implant, with polymethylmethacrylate, and with autografts. Staphylococcus aureus phage type 94/96, isolated from a human osteomyelitis, was instilled into the intramedullar cavity after reaming of the femoral canal and before insertion of the implant. The different 50% infective doses were determined for each of the groups for comparative purposes. The bacterial concentrations required to produce infection in femora without an implant were two times less than those necessary in femora implanted with polymethylmethacrylate. The bone graft required bacterial concentrations nine times less than those necessary to infect femora containing polymethylmethacrylate and four times less than those required to infect femora without an implant. The results presented here confirm that the susceptibility to infection in orthopaedic surgery is not only material dependent but also bacteria dependent.

  17. Does Removal of Subchondral Cortical Bone Provide Sufficient Resection Depth for Treatment of Cam Femoroacetabular Impingement?

    PubMed

    Atkins, Penny R; Aoki, Stephen K; Whitaker, Ross T; Weiss, Jeffrey A; Peters, Christopher L; Anderson, Andrew E

    2017-08-01

    Residual impingement resulting from insufficient resection of bone during the index femoroplasty is the most-common reason for revision surgery in patients with cam-type femoroacetabular impingement (FAI). Development of surgical resection guidelines therefore could reduce the number of patients with persistent pain and reduced ROM after femoroplasty. We asked whether removal of subchondral cortical bone in the region of the lesion in patients with cam FAI could restore femoral anatomy to that of screened control subjects. To evaluate this, we analyzed shape models between: (1) native cam and screened control femurs to observe the location of the cam lesion and establish baseline shape differences between groups, and (2) cam femurs with simulated resections and screened control femurs to evaluate the sufficiency of subchondral cortical bone thickness to guide resection depth. Three-dimensional (3-D) reconstructions of the inner and outer cortical bone boundaries of the proximal femur were generated by segmenting CT images from 45 control subjects (29 males; 15 living subjects, 30 cadavers) with normal radiographic findings and 28 nonconsecutive patients (26 males) with a diagnosis of cam FAI based on radiographic measurements and clinical examinations. Correspondence particles were placed on each femur and statistical shape modeling (SSM) was used to create mean shapes for each cohort. The geometric difference between the mean shape of the patients with cam FAI and that of the screened controls was used to define a consistent region representing the cam lesion. Subchondral cortical bone in this region was removed from the 3-D reconstructions of each cam femur to create a simulated resection. SSM was repeated to determine if the resection produced femoral anatomy that better resembled that of control subjects. Correspondence particle locations were used to generate mean femur shapes and evaluate shape differences using principal component analysis. In the region of

  18. The influence of mesoscale porosity on cortical bone anisotropy. Investigations via asymptotic homogenization

    PubMed Central

    Parnell, William J; Grimal, Quentin

    2008-01-01

    Recently, the mesoscale of cortical bone has been given particular attention in association with novel experimental techniques such as nanoindentation, micro-computed X-ray tomography and quantitative scanning acoustic microscopy (SAM). A need has emerged for reliable mathematical models to interpret the related microscopic and mesoscopic data in terms of effective elastic properties. In this work, a new model of cortical bone elasticity is developed and used to assess the influence of mesoscale porosity on the induced anisotropy of the material. Only the largest pores (Haversian canals and resorption cavities), characteristic of the mesoscale, are considered. The input parameters of the model are derived from typical mesoscale experimental data (e.g. SAM data). We use the method of asymptotic homogenization to determine the local effective elastic properties by modelling the propagation of low-frequency elastic waves through an idealized material that models the local mesostructure. We use a novel solution of the cell problem developed by Parnell & Abrahams. This solution is stable for the physiological range of variation of mesoscopic porosity and elasticity found in bone. Results are computed efficiently (in seconds) and the solutions can be implemented easily by other workers. Parametric studies are performed in order to assess the influence of mesoscopic porosity, the assumptions regarding the material inside the mesoscale pores (drained or undrained bone) and the shape of pores. Results are shown to be in good qualitative agreement with existing schemes and we describe the potential of the scheme for future use in modelling more complex microstructures for cortical bone. In particular, the scheme is shown to be a useful tool with which to predict the qualitative changes in anisotropy due to variations in the structure at the mesoscale. PMID:18628200

  19. Changes in cortical bone channels network and osteocyte organization after the use of zoledronic acid.

    PubMed

    Rabelo, Gustavo Davi; Travençolo, Bruno Augusto Nassif; Oliveira, Marcio Augusto; Beletti, Marcelo Emílio; Gallottini, Marina; Silveira, Fernando Ricardo Xavier da

    2015-12-01

    The aim of this study was to evaluate the effects of zoledronic acid (ZA) on the cortical bone channels network (CBCN) and osteocyte organization in relation to the bone channels. Eighteen male Wistar rats were divided into control (CG) and test groups (TG). Twelve animals from TG received 3 ZA doses (7.5 µg/kg), and 6 animals from CG did not receive any medication. TG animals were euthanized at 14 (n = 6) and 75 (n = 6) dadys after drug injection. CBCN was analyzed in mandibles and tibias using computational routines. The osteocyte organization was qualitatively evaluated in tibias using a three-dimensional reconstruction of images from serial histological sections. Significant differences in CBCN of tibia were found between the treated and untreated rats, with a wider range of sizes and shapes of the channels after the use of ZA (channels area p = 0.0063, channels area SD p = 0.0276) and less bone matrix (bone volume p = 0.0388). The alterations in the channels' morphology were more evident at 75 days after the drug injection (channels perimeter p = 0.0286). No differences were found in mandibles CBCN. The osteocyte distribution revealed more variable patterns of cell distribution in ZA groups, with non-homogeneous distribution of cells in relation to the bone channels. Zoledronic acid induces structural changes in CBCN and modifies the osteocyte arrangement in cortical bone in the tibia; also, the variability in the morphology of bone channels became more evident after a certain time of the use of the drug.

  20. Relationships of the group velocity of the time-reversed Lamb wave with bone properties in cortical bone in vitro.

    PubMed

    Lee, Kang Il; Yoon, Suk Wang

    2017-04-11

    The present study aims to investigate the feasibility of using the time-reversed Lamb wave as a new method for noninvasive characterization of long cortical bones. The group velocity of the time-reversed Lamb wave launched by using the modified time reversal method was measured in 15 bovine tibiae, and their correlations with the bone properties of the tibia were examined. The group velocity of the time-reversed Lamb wave showed significant positive correlations with the bone properties (r=0.55-0.81). The best univariate predictor of the group velocity of the time-reversed Lamb wave was the cortical thickness, yielding an adjusted squared correlation coefficient (r(2)) of 0.64. These results imply that the group velocity of the time-reversed Lamb wave, in addition to the velocities of the first arriving signal and the slow guided wave, could potentially be used as a discriminator for osteoporosis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Connexin37 deficiency alters organic bone matrix, cortical bone geometry, and increases Wnt/β-catenin signaling.

    PubMed

    Pacheco-Costa, Rafael; Kadakia, Jay R; Atkinson, Emily G; Wallace, Joseph M; Plotkin, Lilian I; Reginato, Rejane D

    2017-04-01

    Deletion of connexin (Cx) 37 in mice leads to increased cancellous bone mass due to defective osteoclast differentiation. Paradoxically; however, Cx37-deficient mice exhibit reduced cortical thickness accompanied by higher bone strength, suggesting a contribution of Cx37 to bone matrix composition. Thus, we investigated whether global deletion of Cx37 alters the composition of organic bone extracellular matrix. Five-month-old Cx37(-/-) mice exhibited increased marrow cavity area, and periosteal and endocortical bone surface resulting in higher total area in tibia compared to Cx37(+/+) control mice. Deletion of Cx37 increased genes involved in collagen maturation (loxl3 and loxl4) and glycosaminoglycans- (chsy1, chpf and has3) proteoglycans- associated genes (biglycan and decorin). In addition, expression of type II collagen assessed by immunostaining was increased by 82% whereas collagen maturity by picrosirius-polarizarion tended to be reduced (p=0.071). Expression of glycosaminoglycans by histochemistry was decreased, whereas immunostaining revealed that biglycan was unchanged and decorin was slightly increased in Cx37(-/-) bone sections. Consistent with these in vivo findings, MLO-Y4 osteocytic cells silenced for Cx37 gene exhibited increased mRNA levels for collagen synthesis (col1a1 and col3a1) and collagen maturation (lox, loxl1 and loxl2 genes). Furthermore, mechanistic studies showed Wnt/β-catenin activation in MLO-Y4 osteocytic cells, L5 vertebra, and authentic calvaria-derived osteocytes isolated by fluorescent-activated cell sorter. Our findings demonstrate that altered profile of the bone matrix components in Cx37-deficient mice acts in favor of higher resistance to fracture in long bones.

  2. Intensive glycemic control and thiazolidinedione use: effects on cortical and trabecular bone at the radius and tibia.

    PubMed

    Schwartz, Ann V; Vittinghoff, Eric; Margolis, Karen L; Scibora, Lesley M; Palermo, Lisa; Ambrosius, Walter T; Hue, Trisha F; Ensrud, Kristine E

    2013-05-01

    Factors that contribute to bone fragility in type 2 diabetes are not well understood. We assessed the effects of intensive glycemic control, thiazolidinediones (TZDs), and A1C levels on bone geometry and strength at the radius and tibia. In a substudy of the Action to Control Cardiovascular Risk in Diabetes trial, peripheral quantitative computed tomographic (pQCT) scans of the radius and tibia were obtained 2 years after randomization on 73 participants (intensive n = 35, standard n = 38). TZD use and A1C levels were measured every 4 months during the trial. Effects of intervention assignment, TZD use, and A1C on pQCT parameters were assessed in linear regression models. Intensive, compared with standard, glycemic control was associated with 1.3 % lower cortical volumetric BMD at the tibia in men (p = 0.02) but not with other pQCT parameters. In women, but not men, each additional year of TZD use was associated with an 11 % lower polar strength strain index (SSIp) at the radius (p = 0.04) and tibia (p = 0.002) in models adjusted for A1C levels. In women, each additional 1 % increase in A1C was associated with an 18 % lower SSIp at the ultradistal radius (p = 0.04) in models adjusted for TZD use. There was no consistent evidence of an effect of intensive, compared with standard, glycemic control on bone strength at the radius or tibia. In women, TZD use may reduce bone strength at these sites. Higher A1C may also be associated with lower bone strength at the radius, but not tibia, in women.

  3. Capacitive Extensometer Particularly Suited for Measuring in Vivo Bone Strain

    NASA Technical Reports Server (NTRS)

    Perusek, Gail P. (Inventor)

    2000-01-01

    The present invention provides for in vivo measurements of the principal strain magnitudes and directions, and maximum shear strain that occurs in a material, such as human bone, when it is loaded (or subjected to a load). In one embodiment the invention includes a capacitive delta extensometer arranged with six sensors in a three piece configuration, with each sensor of each pair spaced apart from each other by 120 degrees.

  4. Relationships between the anisotropy of longitudinal wave velocity and hydroxyapatite crystallite orientation in bovine cortical bone.

    PubMed

    Yamamoto, Kazufumi; Nakatsuji, Tomohiro; Yaoi, Yuichiro; Yamato, Yu; Yanagitani, Takahiko; Matsukawa, Mami; Yamazaki, Kaoru; Matsuyama, Yukihiro

    2012-03-01

    Quantitative ultrasound (QUS) is now widely used for evaluating bone in vivo, because obtained ultrasonic wave properties directly reflect the visco-elasticity. Bone tissue is composed of minerals like hydroxyapatite (HAp) and a collagen matrix. HAp crystallites orientation is thus one parameter of bone elasticity. In this study, we experimentally investigated the anisotropy of ultrasonic wave velocity and the HAp crystallites orientation in the axial-radial and axial-tangential planes in detail, using cylindrical specimens obtained from the cortical bone of three bovine femurs. Longitudinal bulk wave propagation was investigated by using a conventional ultrasonic pulse system. We used the one cycle of sinusoidal pulse which was emitted from wide band transmitter. The nominal frequency of the pulse was 1MHz. First, we investigated the anisotropy of longitudinal wave velocity, measuring the anisotropy of velocity in two planes using cylindrical specimens obtained from identical bone areas. The wave velocity changed due to the rotation angle, showing the maximum value in the direction a little off the bone axis. Moreover, X-ray pole figure measurements also indicated that there were small tilts in the HAp crystallites orientation from the bone axis. The tilt angles were similar to those of the highest velocity direction. There were good correlations between velocity and HAp crystallites orientation obtained in different directions. However, a comparatively low correlation was found in posterior bone areas, which shows the stronger effects of bone microstructure. In the radial-tangential plane, where the HAp crystallites hardly ever align, weak anisotropy of velocity was found which seemed to depend on the bone microstructure. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Effects of parathyroid hormone on cortical porosity, non-enzymatic glycation and bone tissue mechanics in rats with type 2 diabetes mellitus.

    PubMed

    Campbell, G M; Tiwari, S; Hofbauer, C; Picke, A-K; Rauner, M; Huber, G; Peña, J A; Damm, T; Barkmann, R; Morlock, M M; Hofbauer, L C; Glüer, C-C

    2016-01-01

    Type 2 diabetes mellitus increases skeletal fragility; however, the contributing mechanisms and the efficacy of bone-forming agents are unclear. We studied diabetes and parathyroid hormone (PTH) treatment effects on cortical porosity (Ct.Po), non-enzymatic glycation (NEG) and bone mechanics in Zucker diabetic fatty (ZDF) rats. Eleven-week old ZDF diabetic (DB) and non-diabetic (ND) rats were given 75μg/kg PTH (1-84) or vehicle 5days per week over 12weeks. The right femora and L4 vertebrae were excised, micro-CT scanned, and tested in 3-point bending and uniaxial compression, respectively. NEG of the samples was determined using fluorescence. Diabetes increased Ct.Po (vertebra (vert): +40.6%, femur (fem): +15.5% vs. ND group, p<0.05) but had no effect on NEG. PTH therapy reduced vertebral NEG in the ND animals only (-73% vs untreated group, p<0.05), and increased femoral NEG in the DB vs. ND groups (+63%, p<0.05). PTH therapy had no effect on Ct.Po. Diabetes negatively affected bone tissue mechanics where reductions in vertebral maximum strain (-22%) and toughness (-42%) were observed in the DB vs. ND group (p<0.05). PTH improved maximum strain in the vertebra of the ND animals (+21%, p<0.05) but did not have an effect in the DB group. PTH increased femoral maximum strain (+21%) and toughness (+28%) in ND and decreased femoral maximum stress (-13%) and toughness (-27%) in the DB animals (treated vs. untreated, p<0.05). Ct.Po correlated negatively with maximum stress (fem: R=-0.35, p<0.05, vert: R=-0.57, p<0.01), maximum strain (fem: R=-0.35, p<0.05, vert: R=-0.43, p<0.05) and toughness (fem: R=-0.34, p<0.05, vert: R=-0.55, p<0.01), and NEG correlated negatively with toughness at the femur (R=-0.34, p<0.05) and maximum strain at the vertebra (R=-0.49, p<0.05). Diabetes increased cortical porosity and reduced bone mechanics, which were not improved with PTH treatment. PTH therapy alone may worsen diabetic bone mechanics through formation of new bone with high AGEs

  6. Vitamin K therapy for cortical bone fragility caused by reduced mechanical loading in a child with hemiplegia.

    PubMed

    Sugiyama, T; Takaki, T; Saito, T; Taguchi, T

    2007-01-01

    Fractures frequently occur at cortical bone sites in children with cerebral palsy, but there is no established therapy. We previously found that treatment with vitamins D and K increased cortical bone mass in children with severe physical disability, and have hypothesized that vitamin K could play a significant role in pediatric cortical bones under conditions with reduced mechanical loading. In the present case report, we treated a right hemiplegic ambulant eight-year-old boy with oral vitamin K (15 mg per day) for eight months. Cortical bone geometries at mid-diaphyseal sites in bilateral tibiae were evaluated before and after the treatment. The cross-sectional total, bone and marrow areas of non-hemiplegic tibia increased by 8.8%, 7.4% and 12.0%, respectively, while those of hemiplegic tibia changed by 9.0%, 14.9% and -3.4%, respectively. As a result, the polar moment of inertia, an indicator of the resistance to torsion forces, increased by 13.0% in the non-hemiplegic tibia and by 63.7% in the hemiplegic tibia. Vitamin K may restrict cortical bone fragility, caused by reduced mechanical loading, through its actions at the endosteal bone marrow interface. Further studies are needed to confirm these findings and to clarify the mechanisms involved.

  7. Previous sport activity during childhood and adolescence is associated with increased cortical bone size in young adult men.

    PubMed

    Nilsson, Martin; Ohlsson, Claes; Mellström, Dan; Lorentzon, Mattias

    2009-01-01

    Physical activity during growth has been associated with altered cortical bone geometry, but it remains uncertain if the physical activity-induced increments in cortical bone size remain when the level of physical activity is diminished or ceased. The aim of this study was to investigate if physical activity during growth is associated with cortical bone geometry in currently inactive young men. In this study, 1068 men (18.9 +/- 0.6 [SD] yr) were included. Cortical bone geometry at the tibia and radius were measured using pQCT. A standardized questionnaire was used to collect information about current and previous sport activity. Subjects who continued to be active (n = 678) and who had been previously active (n = 285) in sports had a wider cortical bone (periosteal circumference [PC], 4.5% and 3.2%, respectively) with increased cross-sectional area (CSA; 12.5% and 6.9%) of the tibia than the always inactive subjects (n = 82). In the currently inactive men (n = 367), regression analysis (including covariates age, height, weight, calcium intake, smoking, and duration of inactivity) showed that previous sport activity was independently associated with cortical bone size of the tibia (CSA and PC). Amount of previous sport activity explained 7.3% of the total variation in cortical CSA. Subjects, who ceased their sport activity for up to 6.5 yr previously, still had greater cortical PC and CSA of the tibia than always inactive subjects. The results from this study indicate that sport activity during growth confers positive effects on bone geometry even though sport activity is ceased.

  8. Elastic properties of external cortical bone in the craniofacial skeleton of the rhesus monkey.

    PubMed

    Wang, Qian; Dechow, Paul C

    2006-11-01

    Knowledge of elastic properties and of their variation in the cortical bone of the craniofacial skeleton is indispensable for creating accurate finite-element models to explore the biomechanics and adaptation of the skull in primates. In this study, we measured elastic properties of the external cortex of the rhesus monkey craniofacial skeleton, using an ultrasonic technique. Twenty-eight cylindrical cortical specimens were removed from each of six craniofacial skeletons of adult Macaca mulatta. Thickness, density, and a set of longitudinal and transverse ultrasonic velocities were measured on each specimen to allow calculation of the elastic properties in three dimensions, according to equations derived from Newton's second law and Hooke's law. The axes of maximum stiffness were determined by fitting longitudinal velocities measured along the perimeter of each cortical specimen to a sinusoidal function. Results showed significant differences in elastic properties between different functional areas of the rhesus cranium, and that many sites have a consistent orientation of maximum stiffness among specimens. Overall, the cortical bones of the rhesus monkey skull can be modeled as orthotropic in many regions, and as transversely isotropic in some regions, e.g., the supraorbital region. There are differences from human crania, suggesting that structural differences in skeletal form relate to differences in cortical material properties across species. These differences also suggest that we require more comparative data on elastic properties in primate craniofacial skeletons to explore effectively the functional significance of these differences, especially when these differences are elucidated through modeling approaches, such as finite-element modeling. (c) 2006 Wiley-Liss, Inc.

  9. Cortical and trabecular bone density in X-linked hypophosphatemic rickets.

    PubMed

    Cheung, Moira; Roschger, Paul; Klaushofer, Klaus; Veilleux, Louis-Nicolas; Roughley, Peter; Glorieux, Francis H; Rauch, Frank

    2013-05-01

    X-linked hypophosphatemic rickets is caused by mutations in PHEX. Even though the disease is characterized by disordered skeletal mineralization, detailed bone densitometric studies are lacking. The aim of the study was to assess volumetric bone mineral density (vBMD) in X-linked hypophosphatemic rickets using forearm peripheral quantitative computed tomography. The study was conducted in the metabolic bone clinic of a pediatric orthopedic hospital. Thirty-four patients (age, 6 to 60 years; 24 female) with PHEX mutations were studied, of whom 7 children (age, 6 to 11 years) were actively being treated with calcitriol and phosphate supplementation. Twenty-one patients (age, 16 to 40 years) had received the same therapy before but had discontinued the treatment; 6 patients (age, 12 to 60 years) had never received this treatment. Trabecular and cortical vBMD of the radius. Trabecular vBMD was elevated (mean age-specific and sex-specific z-score: +1.0) when all patients were analyzed together, due to very high results in currently treated patients (mean z-score: +2.4) and slightly above-average mean values in the other patients. Cortical vBMD was low when the entire cohort was analyzed together (mean z-score: -3.3), but was higher in currently treated patients (mean z-score: -1.3) than in patients who had discontinued therapy (mean z-score: -3.8) or who had never been treated (mean z-score: -4.1). Patients with PHEX mutations have elevated trabecular vBMD at the distal radius while receiving calcitriol and phosphate supplementation, but low cortical vBMD at the radius diaphysis. Low cortical vBMD presumably reflects the underlying mineralization defect that is not entirely corrected by current treatment approaches.

  10. Decreased bone turnover with balanced resorption and formation prevent cortical bone loss during disuse (hibernation) in grizzly bears (Ursus arctos horribilis).

    PubMed

    McGee, Meghan E; Maki, Aaron J; Johnson, Steven E; Nelson, O Lynne; Robbins, Charles T; Donahue, Seth W

    2008-02-01

    Disuse uncouples bone formation from resorption, leading to increased porosity, decreased bone geometrical properties, and decreased bone mineral content which compromises bone mechanical properties and increases fracture risk. However, black bear bone properties are not adversely affected by aging despite annual periods of disuse (i.e., hibernation), which suggests that bears either prevent bone loss during disuse or lose bone and subsequently recover it at a faster rate than other animals. Here we show decreased cortical bone turnover during hibernation with balanced formation and resorption in grizzly bear femurs. Hibernating grizzly bear femurs were less porous and more mineralized, and did not demonstrate any changes in cortical bone geometry or whole bone mechanical properties compared to active grizzly bear femurs. The activation frequency of intracortical remodeling was 75% lower during hibernation than during periods of physical activity, but the normalized mineral apposition rate was unchanged. These data indicate that bone turnover decreases during hibernation, but osteons continue to refill at normal rates. There were no changes in regional variation of porosity, geometry, or remodeling indices in femurs from hibernating bears, indicating that hibernation did not preferentially affect one region of the cortex. Thus, grizzly bears prevent bone loss during disuse by decreasing bone turnover and maintaining balanced formation and resorption, which preserves bone structure and strength. These results support the idea that bears possess a biological mechanism to prevent disuse osteoporosis.

  11. Decreased bone turnover with balanced resorption and formation prevent cortical bone loss during disuse (hibernation) in grizzly bears (Ursus arctos horribilis)

    PubMed Central

    McGee, Meghan E.; Maki, Aaron J.; Johnson, Steven E.; Lynne Nelson, O.; Robbins, Charles T.; Donahue, Seth W.

    2008-01-01

    Disuse uncouples bone formation from resorption, leading to increased porosity, decreased bone geometrical properties, and decreased bone mineral content which compromises bone mechanical properties and increases fracture risk. However, black bear bone properties are not adversely affected by aging despite annual periods of disuse (i.e., hibernation), which suggests that bears either prevent bone loss during disuse or lose bone and subsequently recover it at a faster rate than other animals. Here we show decreased cortical bone turnover during hibernation with balanced formation and resorption in grizzly bear femurs. Hibernating grizzly bear femurs were less porous and more mineralized, and did not demonstrate any changes in cortical bone geometry or whole bone mechanical properties compared to active grizzly bear femurs. The activation frequency of intracortical remodeling was 75% lower during hibernation than during periods of physical activity, but the normalized mineral apposition rate was unchanged. These data indicate bone turnover decreases during hibernation, but osteons continue to refill at normal rates. There were no changes in regional variation of porosity, geometry, or remodeling indices in femurs from hibernating bears, indicating that hibernation did not preferentially affect one region of the cortex. Thus, grizzly bears prevent bone loss during disuse by decreasing bone turnover and maintaining balanced formation and resorption, which preserves bone structure and strength. These results support the idea that bears possess a biological mechanism to prevent disuse osteoporosis. PMID:18037367

  12. Improved accuracy of cortical bone mineralization measured by polychromatic microcomputed tomography using a novel high mineral density composite calibration phantom

    SciTech Connect

    Deuerling, Justin M.; Rudy, David J.; Niebur, Glen L.; Roeder, Ryan K.

    2010-09-15

    Purpose: Microcomputed tomography (micro-CT) is increasingly used as a nondestructive alternative to ashing for measuring bone mineral content. Phantoms are utilized to calibrate the measured x-ray attenuation to discrete levels of mineral density, typically including levels up to 1000 mg HA/cm{sup 3}, which encompasses levels of bone mineral density (BMD) observed in trabecular bone. However, levels of BMD observed in cortical bone and levels of tissue mineral density (TMD) in both cortical and trabecular bone typically exceed 1000 mg HA/cm{sup 3}, requiring extrapolation of the calibration regression, which may result in error. Therefore, the objectives of this study were to investigate (1) the relationship between x-ray attenuation and an expanded range of hydroxyapatite (HA) density in a less attenuating polymer matrix and (2) the effects of the calibration on the accuracy of subsequent measurements of mineralization in human cortical bone specimens. Methods: A novel HA-polymer composite phantom was prepared comprising a less attenuating polymer phase (polyethylene) and an expanded range of HA density (0-1860 mg HA/cm{sup 3}) inclusive of characteristic levels of BMD in cortical bone or TMD in cortical and trabecular bone. The BMD and TMD of cortical bone specimens measured using the new HA-polymer calibration phantom were compared to measurements using a conventional HA-polymer phantom comprising 0-800 mg HA/cm{sup 3} and the corresponding ash density measurements on the same specimens. Results: The HA-polymer composite phantom exhibited a nonlinear relationship between x-ray attenuation and HA density, rather than the linear relationship typically employed a priori, and obviated the need for extrapolation, when calibrating the measured x-ray attenuation to high levels of mineral density. The BMD and TMD of cortical bone specimens measured using the conventional phantom was significantly lower than the measured ash density by 19% (p<0.001, ANCOVA) and 33% (p<0

  13. Labeling studies on cortical bone formation in the antlers of red deer (Cervus elaphus).

    PubMed

    Gomez, S; Garcia, A J; Luna, S; Kierdorf, U; Kierdorf, H; Gallego, L; Landete-Castillejos, T

    2013-01-01

    The formation and mineralization process of antlers, which constitute the fastest growing bones in vertebrates, is still not fully understood. We used oxytetracycline injections to label different stages of bone formation in antlers of 14 red deer between days 28 and 156 of antler growth. Results show that initially a trabecular scaffold of woven bone is formed which largely replaces a pre-existing scaffold of mineralized cartilage. Lamellar bone is then deposited and from about day 70 onwards, primary osteons fill in the longitudinal tubes lined by the scaffold in a proximal to distal sequence. Mineral apposition rate (MAR) in early stages of primary osteon formation is very high (average 2.15 μm/d). Lower MARs were recorded for later stages of primary osteon formation (1.56 μm/d) and for the smaller secondary osteons (0.89 μm/d). Results suggest a peak in mineral demand around day 100 when the extent of mineralizing surfaces is maximal. A few secondary osteons were formed in a process of antler modeling rather than remodeling, as it occurred simultaneously with formation of primary osteons. The degree of cortical porosity reflects a reduction in MAR during later stages of osteonal growth, whereas cortical thickness is determined earlier. Injections given when the antlers were largely or completely clean from velvet produced no labels in antler bone, strongly suggesting that antlers are dead after velvet shedding. The rapidity of antler mineralization and the short lifespan of antlers make them an extraordinary model to assess the effects of chemicals impairing or promoting bone mineralization. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Cluster analysis of infrared spectra of rabbit cortical bone samples during maturation and growth.

    PubMed

    Kobrina, Yevgeniya; Turunen, Mikael J; Saarakkala, Simo; Jurvelin, Jukka S; Hauta-Kasari, Markku; Isaksson, Hanna

    2010-12-01

    Bone consists of an organic and an inorganic matrix. During development, bone undergoes changes in its composition and structure. In this study we apply three different cluster analysis algorithms [K-means (KM), fuzzy C-means (FCM) and hierarchical clustering (HCA)], and discriminant analysis (DA) on infrared spectroscopic data from developing cortical bone with the aim of comparing their ability to correctly classify the samples into different age groups. Cortical bone samples from the mid-diaphysis of the humerus of New Zealand white rabbits from three different maturation stages (newborn (NB), immature (11 days-1 month old), mature (3-6 months old)) were used. Three clusters were obtained by KM, FCM and HCA methods on different spectral regions (amide I, phosphate and carbonate). The newborn samples were well separated (71-100% correct classifications) from the other age groups by all bone components. The mature samples (3-6 months old) were well separated (100%) from those of other age groups by the carbonate spectral region, while by the phosphate and amide I regions some samples were assigned to another group (43-71% correct classifications). The greatest variance in the results for all algorithms was observed in the amide I region. In general, FCM clustering performed better than the other methods, and the overall error was lower. The discriminate analysis results showed that by combining the clustering results from all three spectral regions, the ability to predict the correct age group for all samples increased (from 29-86% to 77-91%). This study is the first to compare several clustering methods on infrared spectra of bone. Fuzzy C-means clustering performed best, and its ability to study the degree of memberships of samples to each cluster might be beneficial in future studies of medical diagnostics.

  15. Defective cancellous bone structure and abnormal response to PTH in cortical bone of mice lacking Cx43 cytoplasmic C-terminus domain.

    PubMed

    Pacheco-Costa, Rafael; Davis, Hannah M; Sorenson, Chad; Hon, Mary C; Hassan, Iraj; Reginato, Rejane D; Allen, Matthew R; Bellido, Teresita; Plotkin, Lilian I

    2015-12-01

    Connexin 43 (Cx43) forms gap junction channels and hemichannels that allow the communication among osteocytes, osteoblasts, and osteoclasts. Cx43 carboxy-terminal (CT) domain regulates channel opening and intracellular signaling by acting as a scaffold for structural and signaling proteins. To determine the role of Cx43 CT domain in bone, mice in which one allele of full length Cx43 was replaced by a mutant lacking the CT domain (Cx43(ΔCT/fl)) were studied. Cx43(ΔCT/fl) mice exhibit lower cancellous bone volume but higher cortical thickness than Cx43(fl/fl) controls, indicating that the CT domain is involved in normal cancellous bone gain but opposes cortical bone acquisition. Further, Cx43(ΔCT) is able to exert the functions of full length osteocytic Cx43 on cortical bone geometry and mechanical properties, demonstrating that domains other than the CT are responsible for Cx43 function in cortical bone. In addition, parathyroid hormone (PTH) failed to increase endocortical bone formation or energy to failure, a mechanical property that indicates resistance to fracture, in cortical bone in Cx43(ΔCT) mice with or without osteocytic full length Cx43. On the other hand, bone mass and bone formation markers were increased by the hormone in all mouse models, regardless of whether full length or Cx43(ΔCT) were or not expressed. We conclude that Cx43 CT domain is involved in proper bone acquisition; and that Cx43 expression in osteocytes is dispensable for some but not all PTH anabolic actions.

  16. The relationship between the mechanical anisotropy of human cortical bone tissue and its microstructure

    NASA Astrophysics Data System (ADS)

    Espinoza Orias, Alejandro A.

    Orthopedics research has made significant advances in the areas of biomechanics, bone implants and bone substitute materials. However, to date there is no definitive model to explain the structure-property relationships in bone as a material to enable better implant designs or to develop a true biomechanical analog of bone. The objective of this investigation was to establish a relationship between the elastic anisotropy of cortical bone tissue and its microstructure. Ultrasonic wave propagation was used to measure stiffness coefficients for specimens sectioned along the length of a human femur. The elastic constants were orthotropic and varied with anatomical location. Stiffness coefficients were generally largest at the midshaft and stiffness anisotropy ratios were largest at the distal and proximal ends. These tests were run on four additional human femurs to assess the influence of phenotypic variation, and in most cases, it was found that phenotypes do not exert a significant effect. Stiffness coefficients were shown to be correlated as a power law relation to apparent density, but anisotropy ratios were not. Texture analysis was performed on selected samples to measure the orientation distribution of the bone mineral crystals. Inverse pole figures showed that bone mineral crystals had a preferred crystallographic orientation, coincident with the long axis of the femur, which is its principal loading direction. The degree of preferred orientation was represented in Multiples of a Random Distribution (MRD), and correlated to the anisotropy ratios. Variation in elastic anisotropy was shown to be primarily due to the bone mineral orientation. The results found in this work can be used to incorporate anisotropy into structural analysis for bone as a material.

  17. Structural and Mechanical Repair of Diffuse Damage in Cortical Bone in vivo

    PubMed Central

    Seref-Ferlengez, Zeynep; Basta-Pljakic, Jelena; Kennedy, Oran D.; Philemon, Claudy J.; Schaffler, Mitchell B.

    2014-01-01

    Physiological wear and tear causes bone microdamage at several hierarchical levels, and these have different biological consequences. Bone remodeling is widely held to be the mechanism by which bone microdamage is repaired. However, recent studies showed that unlike typical linear microcracks, small crack damage, the clusters of submicron-sized matrix cracks also known as diffuse damage (Dif.Dx), does not activate remodeling. Thus, the fate of diffuse damage in vivo is not known. To examine this, we induced selectively Dif.Dx in rat ulnae in vivo by using end-load ulnar bending creep model. Changes in damage content were assessed by histomorphometry and mechanical testing immediately after loading (i.e., acute loaded) or at 14 days after damage induction (i.e., survival ulnae). Dif.Dx area was markedly reduced over the 14-day survival period after loading (p<0.02). We did not observe any intracortical resorption and there was no increase in cortical bone area in survival ulnae. The reduction in whole bone stiffness in acute loaded ulnae was restored to baseline levels in survival ulnae (p>0.6). Microindentation studies showed that Dif.Dx caused a highly localized reduction in elastic modulus in diffuse damage regions of the ulnar cortex. Moduli in these previously damaged bone areas were restored to control values by 14 days after loading. Our current findings indicate that small crack damage in bone can be repaired without bone remodeling, and suggest that alternative repair mechanisms exist in bone to deal with submicron-sized matrix cracks. Those mechanisms are currently unknown and further investigations are needed to elucidate the mechanisms by which this direct repair occurs. PMID:25042459

  18. The Role of Water Compartments in the Material Properties of Cortical Bone

    PubMed Central

    Granke, Mathilde; Does, Mark D.; Nyman, Jeffry S.

    2015-01-01

    Comprising ~20% of the volume, water is a key determinant of the mechanical behavior of cortical bone. It essentially exists in 2 general compartments: within pores and bound to the matrix. The amount of pore water – residing in vascular-lacunar-canalicular space – primarily reflects intracortical porosity (i.e., open spaces within the matrix largely due to Haversian canals and resorption sites), and as such, is inversely proportional to most mechanical properties of bone. Movement of water according to pressure gradients generated during dynamic loading likely confers hydraulic stiffening to the bone as well. Nonetheless, bound water is a primary contributor to mechanical behavior of bone in that it is responsible for giving collagen the ability to confer ductility or plasticity to bone (i.e., allows deformation to continue once permanent damage begins to form in the matrix) and decreases with age along with fracture resistance. Thus, dehydration by air-drying or by solvents with less hydrogen bonding capacity causes bone to become brittle, but interestingly, it also increases stiffness and strength across the hierarchical levels of organization. Despite the importance of matrix hydration to fracture resistance, little is known about why bound water decreases with age in hydrated human bone. Using 1H nuclear magnetic resonance (NMR), both bound and pore water concentrations in bone can be measured ex vivo because the proton relaxation times differ between the two water compartments giving rise to two distinct signals. There are also emerging techniques to measure bound and pore water in vivo with magnetic resonance imaging (MRI). NMR/MRI-derived bound water concentration is positively correlated with both strength and toughness of hydrated bone, and may become a useful clinical marker of fracture risk. PMID:25783011

  19. Histological analysis of the alterations on cortical bone channels network after radiotherapy: A rabbit study.

    PubMed

    Rabelo, Gustavo Davi; Beletti, Marcelo Emílio; Dechichi, Paula

    2010-10-01

    The aim of this study was to evaluate the effects of radiotherapy in cortical bone channels network. Fourteen rabbits were divided in two groups and test group received single dose of 15 Gy cobalt-60 radiation in tibia, bilaterally. The animals were sacrificed and a segment of tibia was removed and histologically processed. Histological images were taken and had their bone channels segmented and called regions of interest (ROI). Images were analyzed through developed algorithms using the SCILAB mathematical environment, getting percentage of bone matrix, ROI areas, ROI perimeters, their standard deviations and Lacunarity. The osteocytes and empty lacunae were also counted. Data were evaluated using Kolmogorov-Smirnov, Mann Whitney, and Student's t test (P < 0.05). Significant differences in bone matrix percentage, area and perimeters of the channels, their respective standard deviations and lacunarity were found between groups. In conclusion, the radiotherapy causes reduction of bone matrix and modifies the morphology of bone channels network. © 2010 Wiley-Liss, Inc.

  20. Bone Microarchitecture in Men and Women with Diabetes: The Importance of Cortical Porosity.

    PubMed

    Paccou, Julien; Ward, Kate A; Jameson, Karen A; Dennison, Elaine M; Cooper, Cyrus; Edwards, Mark H

    2016-05-01

    High-resolution peripheral quantitative computed tomography (HR-pQCT) captures novel aspects of bone geometry, volumetric bone mineral density and offers the ability to measure bone microarchitecture, but data relating measures obtained from this technique to diabetic status are inconsistent in women and lacking in men. Here, we report an analysis from the Hertfordshire Cohort Study, where we were able to study associations between bone microarchitecture from HR-pQCT of distal radius and distal tibia in 332 participants (177 men and 155 women) aged 72.1-81.4 years with or without diabetes mellitus (DM); n = 29 (18 men and 11 women) and n = 303, respectively. Statistical analyses were performed separately for women and men. The mean (SD) age of participants was 76.4 (2.6) and 76.1 (2.5) years in women and men, respectively. Participants with DM differed significantly in terms of weight in both women (70.4 ± 12.3 vs. 80.3 ± 18.3 kg; p = 0.015) and men (81.7 ± 11.4 vs. 92.8 ± 16.3 kg; p < 0.001) but no differences were found in height, smoking status, alcohol intake, social class and physical activity among women or men. Analyses in women revealed that cortical pore volume (Ct.Po.V) was higher in participants with DM and close to statistical significance for cortical porosity (Ct.Po) (β = 0.76 [0.12, 1.41] z-score, p = 0.020 and β = 0.62 [-0.02, 1.27] z-score, p = 0.059, respectively) at the distal radius. Adjustment for weight did not materially affect the relationship described for Ct.Po.V (β = 0.74 [0.09, 1.39], p = 0.027) and Ct.Po (β = 0.65 [-0.01, 1.30], p = 0.053) at the distal radius. After adjustment for weight, analyses in men revealed that Ct.Po and Ct.Po.V were higher in participants with DM (β = 0.57 [0.09, 1.06] z-score, p = 0.021 and β = 0.48 [0.01, 0.95] z-score, p = 0.044, respectively) at the distal tibia. Analyses of distal radial and tibial trabecular bone parameters according to diabetic status

  1. Osteoblast-derived WNT16 represses osteoclastogenesis and prevents cortical bone fragility fractures

    PubMed Central

    Movérare-Skrtic, Sofia; Henning, Petra; Liu, Xianwen; Nagano, Kenichi; Saito, Hiroaki; Börjesson, Anna E; Sjögren, Klara; Windahl, Sara H; Farman, Helen; Kindlund, Bert; Engdahl, Cecilia; Koskela, Antti; Zhang, Fu-Ping; Eriksson, Emma E; Zaman, Farasat; Hammarstedt, Ann; Isaksson, Hanna; Bally, Marta; Kassem, Ali; Lindholm, Catharina; Sandberg, Olof; Aspenberg, Per; Sävendahl, Lars; Feng, Jian Q; Tuckermann, Jan; Tuukkanen, Juha; Poutanen, Matti; Baron, Roland; Lerner, Ulf H; Gori, Francesca; Ohlsson, Claes

    2015-01-01

    The WNT16 locus is a major determinant of cortical bone thickness and nonvertebral fracture risk in humans. The disability, mortality and costs caused by osteoporosis-induced nonvertebral fractures are enormous. We demonstrate here that Wnt16-deficient mice develop spontaneous fractures as a result of low cortical thickness and high cortical porosity. In contrast, trabecular bone volume is not altered in these mice. Mechanistic studies revealed that WNT16 is osteoblast derived and inhibits human and mouse osteoclastogenesis both directly by acting on osteoclast progenitors and indirectly by increasing expression of osteoprotegerin (Opg) in osteoblasts. The signaling pathway activated by WNT16 in osteoclast progenitors is noncanonical, whereas the pathway activated in osteoblasts is both canonical and noncanonical. Conditional Wnt16 inactivation revealed that osteoblast-lineage cells are the principal source of WNT16, and its targeted deletion in osteoblasts increases fracture susceptibility. Thus, osteoblast-derived WNT16 is a previously unreported key regulator of osteoclastogenesis and fracture susceptibility. These findings open new avenues for the specific prevention or treatment of nonvertebral fractures, a substantial unmet medical need. PMID:25306233

  2. A Piece of the Puzzle: The Bone Health Index of the BoneXpert Software Reflects Cortical Bone Mineral Density in Pediatric and Adolescent Patients.

    PubMed

    Schündeln, Michael M; Marschke, Laura; Bauer, Jens J; Hauffa, Pia K; Schweiger, Bernd; Führer-Sakel, Dagmar; Lahner, Harald; Poeppel, Thorsten D; Kiewert, Cordula; Hauffa, Berthold P; Grasemann, Corinna

    2016-01-01

    Suspected osteopathology in chronically ill children often necessitates the assessment of bone mineral density. The most frequently used methods are dual-energy X-ray-absorption (DXA) and peripheral quantitative computed tomography (pQCT). The BoneXpert software provides an automated radiogrammatic method to assess skeletal age from digitalized X-rays of the left hand. Furthermore, the program calculates the Bone Health Index (BHI), a measure of cortical thickness and mineralization, which is obtained from indices of three metacarpal bones. In our study, we analyzed the manner in which BHI information provided by BoneXpert compares with DXA or pQCT measurements in youths. The BHI was retrospectively obtained using digitalized X-rays of the left hand and compared with the results of 203 corresponding DXA readings (Lunar Prodigy, GE Healthcare) of the lumbar vertebrae and femur as well as 117 pQCT readings (XCT 900, Stratec) of the distal radius. The BHI values showed a strong positive correlation with the DXA readings at each and all lumbar vertebrae (L1 -L4: r = 0.73; P < 0.0001). The age-adjusted Z-score of L1 -L4 and the height-adjusted score showed a positive correlation with the BHI-SDS (standard deviation score, r = 0.23; P < 0.002 and r = 0.27; P < 0.001, respectively). Total bone mineral density, as assessed via pQCT, also positively correlated with the BHI (r = 0.39; P < 0.0001), but the trabecular values displayed only a weak correlation. The BHI obtained using BoneXpert can be a useful parameter in the assessment of bone health in children in most cases. This technique provides observer-independent information on cortical thickness and mineralization based on X-ray imaging of the hands.

  3. A Piece of the Puzzle: The Bone Health Index of the BoneXpert Software Reflects Cortical Bone Mineral Density in Pediatric and Adolescent Patients

    PubMed Central

    Schündeln, Michael M.; Marschke, Laura; Bauer, Jens J.; Hauffa, Pia K.; Schweiger, Bernd; Führer-Sakel, Dagmar; Lahner, Harald; Poeppel, Thorsten D.; Kiewert, Cordula; Hauffa, Berthold P.; Grasemann, Corinna

    2016-01-01

    Introduction Suspected osteopathology in chronically ill children often necessitates the assessment of bone mineral density. The most frequently used methods are dual-energy X-ray-absorption (DXA) and peripheral quantitative computed tomography (pQCT). The BoneXpert software provides an automated radiogrammatic method to assess skeletal age from digitalized X-rays of the left hand. Furthermore, the program calculates the Bone Health Index (BHI), a measure of cortical thickness and mineralization, which is obtained from indices of three metacarpal bones. In our study, we analyzed the manner in which BHI information provided by BoneXpert compares with DXA or pQCT measurements in youths. Study Design The BHI was retrospectively obtained using digitalized X-rays of the left hand and compared with the results of 203 corresponding DXA readings (Lunar Prodigy, GE Healthcare) of the lumbar vertebrae and femur as well as 117 pQCT readings (XCT 900, Stratec) of the distal radius. Results The BHI values showed a strong positive correlation with the DXA readings at each and all lumbar vertebrae (L1 –L4: r = 0.73; P < 0.0001). The age-adjusted Z-score of L1 –L4 and the height-adjusted score showed a positive correlation with the BHI-SDS (standard deviation score, r = 0.23; P < 0.002 and r = 0.27; P < 0.001, respectively). Total bone mineral density, as assessed via pQCT, also positively correlated with the BHI (r = 0.39; P < 0.0001), but the trabecular values displayed only a weak correlation. Conclusions The BHI obtained using BoneXpert can be a useful parameter in the assessment of bone health in children in most cases. This technique provides observer-independent information on cortical thickness and mineralization based on X-ray imaging of the hands. PMID:27014874

  4. Cortical bone water changes in ovariectomized rats during the early postoperative period: Objective evaluation using sweep imaging with Fourier transform.

    PubMed

    Sukenari, Tsuyoshi; Horii, Motoyuki; Ikoma, Kazuya; Kido, Masamitsu; Hayashi, Shigeki; Hara, Yusuke; Yamasaki, Tetsuro; Matsuda, Ken-Ichi; Kawata, Mitsuhiro; Kubo, Toshikazu

    2015-07-01

    To evaluate the cortical bone signal-to-noise ratio (SNR) in ovariectomized (OVX) rats during the early postoperative period as a method to measure bone quality using the sweep imaging with Fourier transform (SWIFT) technique. Twelve-week-old female Sprague-Dawley rats (n = 64) were divided into sham and OVX groups. Preoperative tetracycline was immediately administered subcutaneously to distinguish new cortical bone area, and tibial samples were collected at 2, 4, 8, and 12 weeks postoperatively. Magnetic resonance imaging (MRI) was performed using proton density-weighted imaging (PDWI) and SWIFT to obtain cross-sectional images of the tibial diaphysis. The cortical bone SNR was calculated. Bone histomorphometry was performed. Histomorphometry findings showed that the new bone area was significantly greater at 8 and 12 weeks postoperatively in the OVX group (P < 0.05) while the porosity area decreased gradually in both groups (P < 0.001). The difference of SNR receiving PDWI did not reach statistical significance (P = 0.057). The SWIFT technique showed that the SNR was significantly higher at 8 and 12 weeks postoperatively in the OVX group (P < 0.05) and was correlated with the new bone area (R(2) = 0.430). The SWIFT findings suggest that the SWIFT technique may depict early changes in cortical bone quality. © 2014 Wiley Periodicals, Inc.

  5. Development of new criteria for cortical bone histomorphometry in femoral neck: intra- and inter-observer reproducibility.

    PubMed

    Tong, Xiao-Yu; Malo, Markus; Tamminen, Inari S; Isaksson, Hanna; Jurvelin, Jukka S; Kröger, Heikki

    2015-01-01

    Histomorphometry is commonly applied to study bone remodeling. Histological definitions of cortical bone boundaries have not been consistent. In this study, new criteria for specific definition of the transitional zone between the cortical and cancellous bone in the femoral neck were developed. The intra- and inter-observer reproducibility of this method was determined by quantitative histomorphometry and areal overlapping analysis. The undecalcified histological sections of femoral neck specimens (n = 6; from men aged 17-59 years) were processed and scanned to acquire histological images of complete bone sections. Specific criteria were applied to define histological boundaries. "Absolute cortex area" consisted of pure cortical bone tissue only, and was defined mainly based on the size of composite canals and their distance to an additional "guide" boundary (so-called "preliminary cortex boundary," the clear demarcation line of density between compact cortex and sparse trabeculae). Endocortical bone area was defined by recognizing characteristic endocortical structures adjacent to the preliminary cortical boundary. The present results suggested moderate to high reproducibility for low-magnification parameters (e.g., cortical bone area). The coefficient of variation (CV %) ranged from 0.02 to 5.61 in the intra-observer study and from 0.09 to 16.41 in the inter-observer study. However, the intra-observer reproducibility of some high-magnification parameters (e.g., osteoid perimeter/endocortical perimeter) was lower (CV %, 0.33-87.9). The overlapping of three histological areas in repeated analyses revealed highest intra- and inter-observer reproducibility for the absolute cortex area. This study provides specific criteria for the definition of histological boundaries for femoral neck bone specimens, which may aid more precise cortical bone histomorphometry.

  6. Strain rate does not affect cortical microtubule orientation in the isolated epidermis of sunflower hypocotyls.

    PubMed

    Burian, A; Hejnowicz, Z

    2010-05-01

    A hypothesis exists that external and internal factors affect the orientation of cortical microtubules in as much as these lead to changes in cell elongation rate. Factors that stimulate elongation are proposed to lead to transverse microtubule orientation, whereas factors that inhibit elongation lead to longitudinal orientation. The elongation rate is equal to the rate of longitudinal irreversible strain in cell walls. Incubated epidermis peeled from sunflower hypocotyls does not extend unless it is stretched by loading and the pH of the incubation medium is appropriately low. Thus, peels provide a convenient model to investigate the relationship between longitudinal strain rate and cortical microtubule orientation. In the present study, it was found that peeling affects microtubule orientation. Peels were incubated for several hours in Murashige & Skoog medium (both unbuffered and buffered) to attain a steady state of microtubule orientation before loading. The effects of loading and pH on strain rate and orientation of microtubules under the outer epidermal walls were examined in three portions of peels positioned with respect to the cotyledonary node. Appropriate loading caused longitudinal strain of peels at pH 4.5 but not at pH 6.5. However, no clear effect of strain rate on microtubule orientation in the peels was observed. Independent of applied load and pH of the incubation medium, the microtubule orientation remained unchanged, i.e. orientation was mainly oblique. Our results show that strain rate does not affect cortical microtubule orientation in isolated epidermis of the sunflower hypocotyl model system, although orientation could be changed by white light.

  7. Ultrasound strain zero-crossing elasticity measurement in assessment of renal allograft cortical hardness: a preliminary observation.

    PubMed

    Gao, Jing; Rubin, Jonathan M

    2014-09-01

    To determine whether ultrasound strain zero-crossing elasticity measurement can be used to discriminate moderate cortical fibrosis or inflammation in renal allografts, we prospectively assessed cortical hardness with quasi-static ultrasound elastography in 38 renal transplant patients who underwent kidney biopsy from January 2013 to June 2013. With the Banff score criteria for renal cortical fibrosis as gold standard, 38 subjects were divided into two groups: group 1 (n = 18) with ≤25% cortical fibrosis and group 2 (n = 20) with >26% cortical fibrosis. We then divided this population again into group 3 (n = 20) with ≤ 25% inflammation and group 4 (n = 18) with >26% inflammation based on the Banff score for renal parenchyma inflammation. To estimate renal cortical hardness in both population divisions, we propose an ultrasound strain relative zero-crossing elasticity measurement (ZC) method. In this technique, the relative return to baseline, that is zero strain, of strain in the renal cortex is compared with that of strain in reference soft tissue (between the abdominal wall and pelvic muscles). Using the ZC point on the reference strain decompression slope as standard, we determined when cortical strain crossed zero during decompression. ZC was negative when cortical strain did not return or returned after the reference, whereas ZC was positive when cortical strain returned ahead of the reference. Fisher's exact test was used to examine the significance of differences in ZC between groups 1 and 2 and between groups 3 and 4. The accuracy of ZC in determining moderate cortical fibrosis and moderate inflammation was examined by receiver operating characteristic analysis. The intra-class correlation coefficient and analysis of variance were used to test inter-rater reliability and reproducibility. ZC had good inter-observer agreement (ICC = 0.912) and reproducibility (p = 0.979). ZCs were negative in 18 of 18 cases in group 1 and positive in 19 of 20 cases in

  8. In Situ Mechanical Behavior of Mineral Crystals in Human Cortical Bone under Compressive Load Using Synchrotron X-Ray Scattering Techniques

    PubMed Central

    Giri, Bijay; Almer, Jon D.; Dong, X. Neil; Wang, Xiaodu

    2012-01-01

    Mineral crystals, the major strength-bearing component of bone, are aligned in longitudinal bone with (00l) axes preferentially along the longitudinal axis, which in concert with crystal anisotropy leads to macroscopic anisotropy in mechanical behavior. Thus, it is of great interest to delineate the contributions of different subsets of mineral crystals as a function of orientation, on the bulk mechanical behavior of bone. Using a unique synergistic approach combining a progressive loading scheme and synchrotron X-ray scattering techniques, human cortical bone specimens were loaded in compression to examine the in situ mechanical behavior of mineral crystals as the function of orientation. The orientation distribution of mineral crystals was quantitatively estimated by measuring the X-ray diffraction intensity from the crystallographic (002) plane in different orientations. In addition, the average longitudinal (c-axis), transverse (a-axis), and shear strains of the subset of mineral crystals aligned in each orientation were determined by measuring the lattice deformation in the crystals normal to three distinct crystallographic planes (i.e. 002, 310, and 213). The experimental results indicated that the in situ strain and stress of mineral crystals varied with orientation. The normal strain and stress exerted on the longitudinally aligned mineral crystals were markedly greater than those on the transversely oriented crystals, whereas the shear stress reached a maximum for the crystals aligned in ±30° with respect to the loading direction, which coincided with the long axis of bone. The maximum principal strain and stress were observed in the mineral crystals oriented along the loading axis, with a similar trend observed in the maximum shear strain and stress. By examining their in situ behavior, the contribution of mineral crystals to load bearing and the bulk behavior of bone are discussed. PMID:22982959

  9. Evaluation of tibial cortical bone by ultrasound velocity in oriental females.

    PubMed

    Wang, S F; Chang, C Y; Shih, C; Teng, M M

    1997-11-01

    In order to evaluate the feasibility of detecting bone status by measuring cortical ultrasound velocity, ultrasonic transmission velocity of the anterior cortex of shin was measured on 175 normal Chinese females aged 31-75 years (mean 52.3 +/- SD 9.1 years). The data were compared with bone mineral density (BMD) of the lumbar spine and/or hip measured by dual energy X-ray absorptiometry (DXA), which was performed on the same day as speed of sound (SOS) examination. Comparison was made with SOS of Caucasian women previously reported in the literature. SOS of three volunteers measured by two different operators were also enrolled in our study for precision testing. The mean value of SOS of the 175 females was 3850.7 +/- 119.3 m s-1 (range: 3411.7-4220.5 m s-1), the peak value being in the fourth decade. The rate of decrease of transmission velocity per decade from fourth decade to fifth decade was 1.7%, while that of fifth decade to sixth decade was 2.2% and that of sixth decade to seventh decade was 4.0%. The interoperative and intraoperative coefficient variance with and without reposition were under 0.32%. SOS moderately correlated with BMD at different sites, the best correlation being with the lumbar spine anteroposterior projection (r = 0.509; p < 0.0001, Pearson's test). There were significant differences in SOS between pre- and post-menopausal groups (p = 0.01, ANOVA test), and between peri- and post-menopausal groups (p = 0.02), but there was no correlation of body weight and height with SOS. SOS also inversely correlated with age and post-menopausal duration. The mean value of SOS in our study was similar to that of Caucasians, but the rate of decrease over 50 years of age was faster. The rate of decline of tibial cortical SOS was similar to that of trabecular bone as previously reported in the literature. As there is a significant decrease of SOS in older females, and older Oriental females suffer from an accelerated cortical bone loss, it is concluded

  10. Effect of cutting flute design on cortical bone screw insertion torque and pullout strength.

    PubMed

    Yerby, S; Scott, C C; Evans, N J; Messing, K L; Carter, D R

    2001-01-01

    To determine the effect of the number and length of cutting flutes on the insertion torque and pullout strength for self-tapping 4.5-millimeter cortical bone screws. Screws were self-tapped in the diaphysis of human cadaver femurs. Each of the six screw types studied had different designs with varying cutting flute lengths and numbers. Bone mineral density, insertion torque, and pullout strength were measured. The study was conducted at an experimental biomechanics laboratory associated with a university medical center. Insertion torque and pullout strength were normalized by the local bone mineral density. The mean normalized insertion torque of the design with four full-length cutting flutes was less than the design with three full-length flutes and the two designs with one-third length flutes (p < 0.05). The mean normalized pullout strength of the screw with four full-length flutes was significantly greater than that of all screws with fewer than three flutes (p < 0.05). Priorities for a cutting flute design should ideally include ease of screw insertion, minimal soft tissue irritation, and maximal screw holding power. Screws with more than two flutes were easier to insert and did not cause cortical damage during insertion. The screw with four full-length flutes showed a trend toward being the easiest to insert and having the greatest holding strength.

  11. Non destructive characterization of cortical bone micro-damage by nonlinear resonant ultrasound spectroscopy.

    PubMed

    Haupert, Sylvain; Guérard, Sandra; Peyrin, Françoise; Mitton, David; Laugier, Pascal

    2014-01-01

    The objective of the study was to evaluate the ability of a nonlinear ultrasound technique, the so-called nonlinear resonant ultrasound spectroscopy (NRUS) technique, for detecting early microdamage accumulation in cortical bone induced by four-point bending fatigue. Small parallelepiped beam-shaped human cortical bone specimens were subjected to cyclic four-point bending fatigue in several steps. The specimens were prepared to control damage localization during four-point bending fatigue cycling and to unambiguously identify resonant modes for NRUS measurements. NRUS measurements were achieved to follow the evolution of the nonlinear hysteretic elastic behavior during fatigue-induced damage. After each fatigue step, a small number of specimens was removed from the protocol and set apart to quantitatively assess the microcrack number density and length using synchrotron radiation micro-computed tomography (SR-µCT). The results showed a significant effect of damage steps on the nonlinear hysteretic elastic behavior. No significant change in the overall length of microcracks was observed in damaged regions compared to the load-free control regions. Only an increased number of shortest microcracks, those in the lowest quartile, was noticed. This was suggestive of newly formed microcracks during the early phases of damage accumulation. The variation of nonlinear hysteretic elastic behavior was significantly correlated to the variation of the density of short microcracks. Our results suggest that the nonlinear hysteretic elastic behavior is sensitive to early bone microdamage. Therefore NRUS technique can be used to monitor fatigue microdamage progression in in vitro experiments.

  12. Mechanistic aspects of fracture and R-curve behavior in human cortical bone

    SciTech Connect

    Nalla, Ravi K.; Kruzic, Jamie J.; Kinney, John H.; Ritchie, Robert O.

    2004-04-28

    An understanding of the evolution of toughness is essential for the mechanistic interpretation of the fracture of cortical bone. In the present study, in vitro fracture experiments were conducted on human cortical bone in order to identify and quantitatively assess the salient toughening mechanisms. The fracture toughness was found to rise linearly with crack extension (i.e., rising resistance- or R-curve behavior) with a mean crack-initiation toughness, K0 of B2MPaOm for crack growth in the proximal distal direction. Uncracked ligament bridging, which was observed in the wake of the crack, was identified as the dominant toughening mechanism responsible for the observed R-curve behavior. The extent and nature of the bridging zone was examined quantitatively using multicutting compliance experiments in order to assess the bridging zone length and estimate the bridging stress distribution. Additionally, time-dependent cracking behavior was observed at stress intensities well below those required for overload fracture; specifically, slow crack growth occurred at growth rates of approx. 2 x 10-9 m/s at stress intensities approx. 35 percent below the crack-initiation toughness. In an attempt to measure slower growth rates, it was found that the behavior switched to a regime dominated by time dependent crack blunting, similar to that reported for dentin; however, such blunting was apparent over much slower time scales in bone, which permitted subcritical crack growth to readily take place at higher stress intensities.

  13. Mechanistic aspects of fracture and R-curve behavior in human cortical bone.

    PubMed

    Nalla, R K; Kruzic, J J; Kinney, J H; Ritchie, R O

    2005-01-01

    An understanding of the evolution of toughness is essential for the mechanistic interpretation of the fracture of cortical bone. In the present study, in vitro fracture experiments were conducted on human cortical bone in order to identify and quantitatively assess the salient toughening mechanisms. The fracture toughness was found to rise linearly with crack extension (i.e., rising resistance- or R-curve behavior) with a mean crack-initiation toughness, K0 of approximately 2 MPa square root m for crack growth in the proximal-distal direction. Uncracked ligament bridging, which was observed in the wake of the crack, was identified as the dominant toughening mechanism responsible for the observed R-curve behavior. The extent and nature of the bridging zone was examined quantitatively using multi-cutting compliance experiments in order to assess the bridging zone length and estimate the bridging stress distribution. Additionally, time-dependent cracking behavior was observed at stress intensities well below those required for overload fracture; specifically, slow crack growth occurred at growth rates of approximately 2 x 10(-9) m/s at stress intensities approximately 35% below the crack-initiation toughness. In an attempt to measure slower growth rates, it was found that the behavior switched to a regime dominated by time-dependent crack blunting, similar to that reported for dentin; however, such blunting was apparent over much slower time scales in bone, which permitted subcritical crack growth to readily take place at higher stress intensities.

  14. Glycation of Human Cortical and Cancellous Bone Captures Differences in the Formation of Maillard Reaction Products between Glucose and Ribose

    PubMed Central

    Sroga, Grażyna E.; Siddula, Alankrita; Vashishth, Deepak

    2015-01-01

    To better understand some aspects of bone matrix glycation, we used an in vitro glycation approach. Within two weeks, our glycation procedures led to the formation of advanced glycation end products (AGEs) at the levels that corresponded to approx. 25–30 years of the natural in vivo glycation. Cortical and cancellous bones from human tibias were glycated in vitro using either glucose (glucosylation) or ribose (ribosylation). Both glucosylation and ribosylation led to the formation of higher levels of AGEs and pentosidine (PEN) in cancellous than cortical bone dissected from all tested donors (young, middle-age and elderly men and women). More efficient glycation of bone matrix proteins in cancellous bone most likely depended on the higher porosity of this tissue, which facilitated better accessibility of the sugars to the matrix proteins. Notably, glycation of cortical bone from older donors led to much higher AGEs levels as compared to young donors. Such efficient in vitro glycation of older cortical bone could result from aging-related increase in porosity caused by the loss of mineral content. In addition, more pronounced glycation in vivo would be driven by elevated oxidation processes. Interestingly, the levels of PEN formation differed pronouncedly between glucosylation and ribosylation. Ribosylation generated very high levels of PEN (approx. 6- vs. 2.5-fold higher PEN level than in glucosylated samples). Kinetic studies of AGEs and PEN formation in human cortical and cancellous bone matrix confirmed higher accumulation of fluorescent crosslinks for ribosylation. Our results suggest that in vitro glycation of bone using glucose leads to the formation of lower levels of AGEs including PEN, whereas ribosylation appears to support a pathway toward PEN formation. Our studies may help to understand differences in the progression of bone pathologies related to protein glycation by different sugars, and raise awareness for excessive sugar supplementation in food

  15. Osteogenic effect of a gastric pentadecapeptide, BPC-157, on the healing of segmental bone defect in rabbits: a comparison with bone marrow and autologous cortical bone implantation.

    PubMed

    Sebecić, B; Nikolić, V; Sikirić, P; Seiwerth, S; Sosa, T; Patrlj, L; Grabarević, Z; Rucman, R; Petek, M; Konjevoda, P; Jadrijević, S; Perović, D; Slaj, M

    1999-03-01

    Gastrectomy often results in increased likelihood of osteoporosis, metabolic aberration, and risk of fracture, and there is a need for a gastric peptide with osteogenic activity. A novel stomach pentadecapeptide, BPC-157, improves wound and fracture healing in rats in addition to having an angiogenic effect. Therefore, in the present study, using a segmental osteoperiosteal bone defect (0.8 cm, in the middle of