The Experts below are selected from a list of 15315 Experts worldwide ranked by ideXlab platform
David W. Dempster - One of the best experts on this subject based on the ideXlab platform.
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three dimensional Cancellous Bone structure in hypoparathyroidism
Bone, 2010Co-Authors: Mishaela R Rubin, Thomas Köhler, Elizabeth Shane, David W. Dempster, H. Zhou, M Stauber, Thomas L Nickolas, Emily M Stein, James Sliney, Shonni J. SilverbergAbstract:Abstract By conventional 2-dimensional histomorphometric analysis, we have shown that Cancellous Bone architecture is markedly altered in hypoparathyroidism. We have now extended these observations to a 3-dimensional analysis using microcomputed tomography. Percutaneous iliac crest Bone biopsies were analyzed by high-resolution microcomputed tomography from the following 25 subjects with hypoparathyroidism: 5 postmenopausal women, 13 premenopausal women and 7 men. Thirteen living premenopausal healthy controls and 12 cadaver subjects without Bone disease served as matched controls. Hypoparathyroid subjects had significantly greater Bone surface density (BS/TV: 5.74 ± 4.7 vs. 3.73 ± 1.01 mm 2 /mm 3 [mean ± SD]; p = 0.04), trabecular thickness (Tb.Th: 0.25 ± 0.19 vs. 0.17 ± 0.04 mm; p = 0.04), trabecular number (Tb.N: 2.99 ± 3.4 vs. 1.62 ± 0.39 mm − 1 ; p = 0.05) and connectivity density (Conn.D: 16.63 ± 18.7 vs. 8.39 ± 5.8 mm 3 ; p = 0.04) in comparison to matched controls. When an additional 8 hypoparathyroid (total n = 33) and 24 cadaver (total cadaver n = 36) subjects were added to the groups for an unmatched analysis, hypoparathyroid subjects had significantly greater Cancellous Bone volume (BV/TV: 26.98 ± 10 vs. 15.39 ± 4%; p p p
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Preserved three-dimensional Cancellous Bone structure in mild primary hyperparathyroidism
Bone, 2007Co-Authors: David W. Dempster, Thomas Köhler, Elizabeth Shane, Shonni J. Silverberg, May Parisien, H. Zhou, Ralph Müller, John P BilezikianAbstract:By conventional 2-dimensional, histomorphometric analysis, we and others have previously shown that Cancellous Bone architecture is preserved in mild primary hyperparathyroidism (PHPT). We have now extended these observations to a 3-dimensional analysis using microcomputed tomography (microCT). Iliac crest Bone biopsies were analyzed from the following subjects with PHPT: 22 postmenopausal women; 7 premenopausal women; similar numbers of normal pre- and postmenopausal women served as controls. Fifteen men with PHPT were also studied. Postmenopausal women with PHPT demonstrated features of preserved Cancellous Bone as shown by smaller age-related declines in Cancellous Bone volume (BV/TV) and connectivity density (Conn.D) and no change in Bone surface/total volume (BS/TV) as compared to normal women. In postmenopausal women with PHPT, Cancellous Bone volume (BV/TV), Bone surface/total volume, and connectivity density (Conn.D) were all higher, and trabecular separation (Tb.Sp) was lower than in postmenopausal controls. In sharp contrast to the findings in normal women, no structural variables in PHPT women were correlated with age. Also of note, there was no difference in any 3-dimensional index between women and men with PHPT. We conclude that three-dimensional, Cancellous Bone microarchitecture is preserved in patients with mild primary hyperparathyroidism.
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On the mechanism of Cancellous Bone preservation in postmenopausal women with mild primary hyperparathyroidism.
The Journal of clinical endocrinology and metabolism, 1999Co-Authors: David W. Dempster, Elizabeth Shane, Shonni J. Silverberg, May Parisien, X. G. Liang, M. Schnitzer, V. Shen, Donald B. Kimmel, Robert R. Recker, R. LindsayAbstract:Several studies have demonstrated that Cancellous Bone mass and architecture are preserved in postmenopausal women with primary hyperparathyroidism (PHPT). To investigate the mechanism(s) that could account for this observation, we analyzed features of Bone formation in 19 postmenopausal women with PHPT by Bone histomorphometry. The results were compared with those from a comparable group of 34 healthy, postmenopausal women. Patients with PHPT were similar to control subjects in Cancellous Bone area as well as in trabecular width, separation, and number. However, in PHPT, elevations were observed in indexes of Bone turnover, such as eroded surface, osteoid surface, mineralizing surface, Bone formation rate at the tissue level, and activation frequency. At the level of the Bone-remodeling unit, women with PHPT had significantly higher values for the wall width of trabecular Bone packets (40.26 +/- 0.36 vs. 34.58 +/- 0.45 mm), the adjusted apposition rate (0.40 +/- 0.04 vs. 0.29 +/- 0.03 mm/day), and the active formation period (67.8 +/- 5.1 vs. 57.3 +/- 2.3 days). These findings are consistent with a stimulatory action of elevated PTH levels on the duration of the active Bone formation phase in individual remodeling units and may account at least in part for the preservation of Cancellous Bone in postmenopausal women with mild PHPT.
R. Lindsay - One of the best experts on this subject based on the ideXlab platform.
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On the mechanism of Cancellous Bone preservation in postmenopausal women with mild primary hyperparathyroidism.
The Journal of clinical endocrinology and metabolism, 1999Co-Authors: David W. Dempster, Elizabeth Shane, Shonni J. Silverberg, May Parisien, X. G. Liang, M. Schnitzer, V. Shen, Donald B. Kimmel, Robert R. Recker, R. LindsayAbstract:Several studies have demonstrated that Cancellous Bone mass and architecture are preserved in postmenopausal women with primary hyperparathyroidism (PHPT). To investigate the mechanism(s) that could account for this observation, we analyzed features of Bone formation in 19 postmenopausal women with PHPT by Bone histomorphometry. The results were compared with those from a comparable group of 34 healthy, postmenopausal women. Patients with PHPT were similar to control subjects in Cancellous Bone area as well as in trabecular width, separation, and number. However, in PHPT, elevations were observed in indexes of Bone turnover, such as eroded surface, osteoid surface, mineralizing surface, Bone formation rate at the tissue level, and activation frequency. At the level of the Bone-remodeling unit, women with PHPT had significantly higher values for the wall width of trabecular Bone packets (40.26 +/- 0.36 vs. 34.58 +/- 0.45 mm), the adjusted apposition rate (0.40 +/- 0.04 vs. 0.29 +/- 0.03 mm/day), and the active formation period (67.8 +/- 5.1 vs. 57.3 +/- 2.3 days). These findings are consistent with a stimulatory action of elevated PTH levels on the duration of the active Bone formation phase in individual remodeling units and may account at least in part for the preservation of Cancellous Bone in postmenopausal women with mild PHPT.
Alain Meunier - One of the best experts on this subject based on the ideXlab platform.
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in vitro acoustic waves propagation in human and bovine Cancellous Bone
Journal of Bone and Mineral Research, 2003Co-Authors: Luis Cardoso, Frederic Teboul, L Sedel, C Oddou, Alain MeunierAbstract:The acoustic behavior of Cancellous Bone with regard to its complex poroelastic nature has been investigated. The existence of two longitudinal modes of propagation is demonstrated in both bovine and human Cancellous Bone. Failure to take into account the presence of these two waves may result in inaccurate material characterization. Introduction: Acoustic wave propagation is now a commonly used nondestructive method for Cancellous Bone characterization. However, wave propagation in this material may be affected by fluid-solid interactions inherent to its poroelastic nature, resulting in two different longitudinal waves. This phenomenon has been demonstrated in previous studies and is in agreement with Biot's theory. The purpose of this paper is to extend these findings to human trabecular Bone and to thoroughly investigate these two waves. Materials and Methods: Sixty human and 14 bovine Cancellous Bone cubic specimens were tested in vitro in three different directions using an immersion acoustic transmission method. Original procedures were developed to quantify both velocity and attenuation characteristics of each wave. In term of attenuation, a modified broadband ultrasound attenuation (BUA), describing the rate of change of the frequency-dependent attenuation, was defined for each wave (FDUA). Results: Both waves were identified in most of the specimens. The fast wave velocities demonstrated a negative linear correlation with porosity (1500–2300 m/s, R2 = 0.44, p < 10−3), whereas the slow wave velocities exhibited two different behaviors: (1) a first set of data clearly dependent on porosity showing a positive linear correlation (1150–1450 m/s, R2 = 0.26, p < 10−3) and (2) a second group independent on porosity. The fast wave FDUA (20–140 dB/cmMHz) showed a parabolic behavior and reached a maximum for 75% porosity (second degree relationship R2 = 0.41, p < 10−3), whereas a positive linear behavior was observed for the slow wave FDUA (15–40 dB/cmMHz; R2 = 0.15, p < 10−2). Conclusions: Existence of two wave propagation modes were demonstrated in human Cancellous Bone. Our data suggest that, in some cases, the amplitude of the slow wave is much larger than the amplitude of the fast wave. For this reason, care should be taken when using measurement systems that incorporate simple threshold detection because the fast wave could remain undetected. Moreover, failure to consider the presence of these two waves could result in an inaccurate quantification of Cancellous Bone physical properties.
Rik Huiskes - One of the best experts on this subject based on the ideXlab platform.
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the dependence of the elastic properties of osteoporotic Cancellous Bone on volume fraction and fabric
Journal of Biomechanics, 2003Co-Authors: Rik Huiskes, Jasper Homminga, Barbara R Mccreadie, Harrie WeinansAbstract:Osteoporosis is a progressive systemic skeletal condition characterized by low Bone mass and microarchitectural deterioration, with a consequent increase in susceptibility to fracture. Hence, osteoporosis would be best diagnosed by in vivo measurements of Bone strength. As this is not clinically feasible, our goal is to estimate Bone strength through the assessment of elastic properties, which are highly correlated to strength. Previously established relations between morphological parameters (volume fraction and fabric) and elastic constants could be applied to estimate Cancellous Bone stiffness in vivo. However, these relations were determined for normal Cancellous Bone. Cancellous Bone from osteoporotic patients may require different relations. In this study we set out to answer two questions. First, can the elastic properties of osteoporotic Cancellous Bone be estimated from morphological parameters? Second, do the relations between morphological parameters and elastic constants, determined for normal Bone, apply to osteoporotic Bone as well? To answer these questions we used Cancellous Bone cubes from femoral heads of patients with (n=26) and without (n=32) hip fractures. The elastic properties of the cubes were determined using micro-finite element analysis, assuming equal tissue moduli for all specimens. The morphological parameters were determined using microcomputed tomography. Our results showed that, for equal tissue properties, the elastic properties of Cancellous Bone from fracture patients could indeed be estimated from morphological parameters. The morphology-based relations used to estimate the elastic properties of Cancellous Bone are not different for women with or without fractures.
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constitutive relationships of fabric density and elastic properties in Cancellous Bone architecture
Bone, 1999Co-Authors: J Kabel, Anders Odgaard, B Van Rietbergen, Rik HuiskesAbstract:Abstract The hypothesis that trabecular morphology can predict the elastic properties of Cancellous Bone has only partly been verified and no predictive analytical model is currently available. Such models are becoming increasingly relevant as the resolution levels of three-dimensional scanning techniques approach the size of trabeculae. This study took advantage of micro-finite-element methods and tested the aforementioned hypothesis in normal Cancellous Bone material collected at six anatomical locations from 56 individuals. Numerical analysis was based on high-resolution three-dimensional computer reconstructions of Cancellous Bone specimens from which the complete elastic characteristics and trabecular morphology, represented by three different fabric measures (the mean intercept length and two volume-based ones), were calculated. Each fabric measure was analyzed individually using the tensorial relationships derived by Cowin ( Mech Mater 4:137–147; 1985). Models for both stiffness and compliance entries were developed. The models based on stiffness entries could explain 93.4%–95.6% of the variance, whereas those based on compliance entries could explain 89.2%–89.4%. When using the former model, the MIL (mean intercept length measure) performed slightly better than the two volume-based measures, VO (volume orientation) and SVD (star volume distribution), with 23% less remaining variance. The high correlations found strongly support the hypothesis and increase the hope that, on the basis of information on trabecular morphology, it will be possible to obtain considerably better estimates of Bone quality in vivo compared with the rough two-dimensional density measurements used today.
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fabric and elastic principal directions of Cancellous Bone are closely related
Journal of Biomechanics, 1997Co-Authors: A Odgaard, J Kabel, Bert Van Rietbergen, Michel Dalstra, Rik HuiskesAbstract:Abstract Cancellous Bone architecture and mechanics are intimately related. The trabecular architecture of Cancellous Bone is considered determined by its mechanical environment (Wolff's law), and the mechanical properties of Cancellous Bone are inversely determined by the trabecular architecture and material properties. Much effort has been spent in expressing these relations, but the techniques and variables necessary for this have not been fully identified. it is obvious, however, that some measure of architectural anisotropy (fabric) is needed. Within the last few years, volume-based measures of fabric have been introduced as alternatives to the mean intercept length method, which has some theoretical problems. This paper seeks to answer which of four different fabric measures best predicts finite element calculated mechanical anisotropy directions. Twenty-nine Cancellous Bone specimens were three-dimensionally reconstructed using the automated serial sectioning technique. A series of large-scale finite-element analyses were performed on each of the three-dimensional reconstructions to calculate the compliance matrix for each specimen, from which the mechanical principal directions were derived. The architcctural anisotropy was determined in three-dimensional space for each specimen using mean intercept length (MIL), volume orientation (VO), star volume distribution (SVD) and star length distribution (SLD). Each of the architectural anisotropy results were expressed by a fabric tensor. Architectural main directions were determined from the fabric tensors and compared with the FE-calculated mechanical anisotropy directions. All architectural measures predicted the mechanical main directions rather well, which supports the assumption that mechanical anisotropy directions are aligned with fabric directions. MIL showed a significant, though very small (1.4°), deviation from the primary mechanical direction. VO had difficulty in determining secondary and tertiary mechanical directions; its mcan deviation was 8.9°. SVD and SLD provided marginally better predictors of mechanical anisotropy directions than MIL and VO.
Shonni J. Silverberg - One of the best experts on this subject based on the ideXlab platform.
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three dimensional Cancellous Bone structure in hypoparathyroidism
Bone, 2010Co-Authors: Mishaela R Rubin, Thomas Köhler, Elizabeth Shane, David W. Dempster, H. Zhou, M Stauber, Thomas L Nickolas, Emily M Stein, James Sliney, Shonni J. SilverbergAbstract:Abstract By conventional 2-dimensional histomorphometric analysis, we have shown that Cancellous Bone architecture is markedly altered in hypoparathyroidism. We have now extended these observations to a 3-dimensional analysis using microcomputed tomography. Percutaneous iliac crest Bone biopsies were analyzed by high-resolution microcomputed tomography from the following 25 subjects with hypoparathyroidism: 5 postmenopausal women, 13 premenopausal women and 7 men. Thirteen living premenopausal healthy controls and 12 cadaver subjects without Bone disease served as matched controls. Hypoparathyroid subjects had significantly greater Bone surface density (BS/TV: 5.74 ± 4.7 vs. 3.73 ± 1.01 mm 2 /mm 3 [mean ± SD]; p = 0.04), trabecular thickness (Tb.Th: 0.25 ± 0.19 vs. 0.17 ± 0.04 mm; p = 0.04), trabecular number (Tb.N: 2.99 ± 3.4 vs. 1.62 ± 0.39 mm − 1 ; p = 0.05) and connectivity density (Conn.D: 16.63 ± 18.7 vs. 8.39 ± 5.8 mm 3 ; p = 0.04) in comparison to matched controls. When an additional 8 hypoparathyroid (total n = 33) and 24 cadaver (total cadaver n = 36) subjects were added to the groups for an unmatched analysis, hypoparathyroid subjects had significantly greater Cancellous Bone volume (BV/TV: 26.98 ± 10 vs. 15.39 ± 4%; p p p
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Preserved three-dimensional Cancellous Bone structure in mild primary hyperparathyroidism
Bone, 2007Co-Authors: David W. Dempster, Thomas Köhler, Elizabeth Shane, Shonni J. Silverberg, May Parisien, H. Zhou, Ralph Müller, John P BilezikianAbstract:By conventional 2-dimensional, histomorphometric analysis, we and others have previously shown that Cancellous Bone architecture is preserved in mild primary hyperparathyroidism (PHPT). We have now extended these observations to a 3-dimensional analysis using microcomputed tomography (microCT). Iliac crest Bone biopsies were analyzed from the following subjects with PHPT: 22 postmenopausal women; 7 premenopausal women; similar numbers of normal pre- and postmenopausal women served as controls. Fifteen men with PHPT were also studied. Postmenopausal women with PHPT demonstrated features of preserved Cancellous Bone as shown by smaller age-related declines in Cancellous Bone volume (BV/TV) and connectivity density (Conn.D) and no change in Bone surface/total volume (BS/TV) as compared to normal women. In postmenopausal women with PHPT, Cancellous Bone volume (BV/TV), Bone surface/total volume, and connectivity density (Conn.D) were all higher, and trabecular separation (Tb.Sp) was lower than in postmenopausal controls. In sharp contrast to the findings in normal women, no structural variables in PHPT women were correlated with age. Also of note, there was no difference in any 3-dimensional index between women and men with PHPT. We conclude that three-dimensional, Cancellous Bone microarchitecture is preserved in patients with mild primary hyperparathyroidism.
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On the mechanism of Cancellous Bone preservation in postmenopausal women with mild primary hyperparathyroidism.
The Journal of clinical endocrinology and metabolism, 1999Co-Authors: David W. Dempster, Elizabeth Shane, Shonni J. Silverberg, May Parisien, X. G. Liang, M. Schnitzer, V. Shen, Donald B. Kimmel, Robert R. Recker, R. LindsayAbstract:Several studies have demonstrated that Cancellous Bone mass and architecture are preserved in postmenopausal women with primary hyperparathyroidism (PHPT). To investigate the mechanism(s) that could account for this observation, we analyzed features of Bone formation in 19 postmenopausal women with PHPT by Bone histomorphometry. The results were compared with those from a comparable group of 34 healthy, postmenopausal women. Patients with PHPT were similar to control subjects in Cancellous Bone area as well as in trabecular width, separation, and number. However, in PHPT, elevations were observed in indexes of Bone turnover, such as eroded surface, osteoid surface, mineralizing surface, Bone formation rate at the tissue level, and activation frequency. At the level of the Bone-remodeling unit, women with PHPT had significantly higher values for the wall width of trabecular Bone packets (40.26 +/- 0.36 vs. 34.58 +/- 0.45 mm), the adjusted apposition rate (0.40 +/- 0.04 vs. 0.29 +/- 0.03 mm/day), and the active formation period (67.8 +/- 5.1 vs. 57.3 +/- 2.3 days). These findings are consistent with a stimulatory action of elevated PTH levels on the duration of the active Bone formation phase in individual remodeling units and may account at least in part for the preservation of Cancellous Bone in postmenopausal women with mild PHPT.
