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  • 1
    Electronic Resource
    Electronic Resource
    Ultrasound Velocity of Trabecular Cubes Reflects Mainly Bone Density and Elasticity (1999)
    Springer
    Calcified tissue international 64 (1999), S. 18-23 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Ultrasound—Velocity—Elasticity—Structure—Density.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Studies have indicated that quantitative ultrasound (QUS) variables may be influenced by the mechanical properties of bone which in turn are determined by bone's material and structural properties. However, from these studies it is unclear what role density, elasticity, and structure play in determining velocity. Eighteen defatted, 12-mm cubic trabecular bone specimens were cut from cadaveric specimens. Amplitude-dependent speed of sound (SOS) using a single point QUS system was assessed in three orthogonal axes. Magnetic resonance images were obtained, from which measures of apparent trabeuclar structure were derived. The specimens were nondestructively tested in compression along three orthogonal axes defined by the sides of the cubes. The elastic modulus (in the three directions) and the strength (in one direction) were determined. Trabecular BMD was measured by quantitative computed tomography. SOS varied significantly with direction of measurement, with the highest value in the axial direction (axial:1715 m/s, sagittal: 1662 m/second, and coronal: 1676 m/s). SOS of each of the three axes was generally associated with the various mechanical (r = 0.30–0.87), density (r = 0.81–0.93), and bone structural variables (0.3–0.8). However, after adjusting the SOS correlations by density, only the correlation with elasticity remained significant in the coronal direction. BMD alone explained 88–93% of variance in SOS whereas in the multivariate model, BMD plus elasticity and/or anisotropic variables explained 96–98% of the variance in SOS. Variability of SOS is explained mostly by density and to a small extent by elasticity or anisotropy. Since only 2–6% of the variance of the QUS measurement is not explained by density and elasticity, one could conclude that the remaining variance reflects other properties of bone or perhaps simply measurement error. Evidence that these other properties may be structure related is only found in the anisotropy of QUS parameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900572
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  • 2
    Electronic Resource
    Electronic Resource
    Power Spectral Analysis of Vertebral Trabecular Bone Structure from Radiographs: Orientation Dependence and Correlation with Bone Mineral Density and Mechanical Properties (1998)
    Springer
    Calcified tissue international 63 (1998), S. 482-489 
    Details
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Trabecular bone structure and bone density contribute to the strength of bone and are potentially important in the study of osteoporosis. Fourier transforms of the textural patterns in radiographs of trabecular bone have previously been used for the measurement of trabecular bone structure in subjects, however, the relationship between these measures and biomechanical properties of bone have not previously been established. In this study radiographs were acquired of 28 cubic specimens of spinal trabecular bone along each of the three anatomic axes: cranio-caudal or superior-inferior (SI), medial-lateral (ML), and anterior-posterior (AP). The radiographs were digitized, background corrected, and uniformly aligned. The Fast Fourier transform (FFT) was performed on a region comprised solely of trabecular bone for each image. The zero (DC), first (FMO), and second moments (SMO) of the Fourier power spectrum and the fractal dimension (FD) as determined from the Fourier power spectrum were correlated with stereology measures, with bone mineral density (BMD) as well as with measured biomechanical properties [Young's elastic modulus (YM) and ultimate strength] of the cubes. The results show that the power spectra-based measures, when compared with structural parameters determined using 3D stereology, show good correlations with bone volume fraction, trabecular spacing, thickness, and number. These power spectral measures showed fair to good correlations with BMD and the biomechanical properties. Moreover, the correlations between the power spectral measures of trabecular structure and the BMD, YM, and stereology measures of structure depend on the orientation of the radiographic image. Specifically, these were significant differences in the measured biomechanical properties and the power spectral measures of the trabecular structure between the SI and ML and the SI and AP directions. In addition, depending on the spatial frequency range for analysis, the fractal dimension showed opposite trends with changes in BMD and biomechanical properties. Multivariate regression models showed the correlation coefficients increasing with the inclusion of some of the power spectral measures, suggesting that FFT-based texture analysis may play a potential role in studies of osteoporosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900562
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  • 3
    Electronic Resource
    Electronic Resource
    Image-Based Assessment of Spinal Trabecular Bone Structure from High-Resolution CT Images (1998)
    Springer
    Osteoporosis international 8 (1998), S. 317-325 
    Details
    ISSN: 1433-2965
    Keywords: Key words:Connectivity – High-resolution CT – Trabecular structure – Vertebral fracture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: The goal of this study was to assess whether a high-resolution CT measure of trabecular bone structure can enhance the discrimination between subjects with or without a vertebral fracture and having overall low hip or spine bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA). Sixty-one women with low BMD by DXA (T-score 〈–2.5 at hip or spine) were examined. Twenty women had sustained a vertebral fracture. Quantitative CT (QCT) BMD and high-resolution CT spinal scans were performed on a whole-body CT scanner. For the high-resolution images (0.31 mm pixel, 1.5 mm thick slice), trabecular bone was segmented from marrow using an adaptive threshold, region growth and skeletonization step. From the processed image we measured the apparent trabecular bone fraction (BV/TV), apparent trabecular thickness (I.Th) and apparent trabecular spacing (I.Sp). We also assessed the connectivity of the marrow space using region growing to derive a mean (HA) and maximum (HM) hole size. Despite the fact that the study population was preselected to have a low BMD by DXA, QCT BMD was highly associated with (p 〈0.005) with fracture status. All structural parameters were correlated (r ~ 0.64 to 0.79) with BMD with p 〈0.003 and showed significant differences between the fracture and non-fracture group. However, except for HA, this difference did not remain significant after adjustment for BMD. When BMD and then HA was entered into a paired linear regression model to predict fracture outcome, HA contributed with p= 0.03 and BMD with p= 0.86. ROC analysis was applied and showed that HA, BMD, I.Th and I.Sp discriminated the two groups with areas of 0.76, 0.75, 0.71 and 0.68, respectively. These findings suggest that an assessment of vertebral trabecular structure from high-resolution CT images is useful in discriminating subjects with vertebral fractures and potentially useful for predicting future fractures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001980050070
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative Bone Mineral Assessment at the Forearm: A Review (1998)
    Springer
    Osteoporosis international 8 (1998), S. 299-310 
    Details
    ISSN: 1433-2965
    Keywords: Key words:Bone mineral density – Distal radius – Dual X-ray absorptiometry (DXA) – Osteoporosis – Peripheral quantitative computed tomography (pQCT)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: Bone mineral density and geometric properties of the human forearm can be measured to determine the amount of bone or bone loss at the scanning site and to predict the risk of forearm fractures. These forearm mesurements are also used to estimate bone mass at remote anatomical locations and thereby estimate the risk for spine, hip and other fractures. The peripheral location of the human forearm, with its relatively small amount of surrounding soft tissue, improves the accuracy and the precision of bone mass measurement and has made this site an early choice for the assessment of a subject's bone mineral status. Furthermore, the anatomy of the human radius enables the examination of both cortical and cancellous bone. This review describes the procedures for non-invasive bone assessment at peripheral sites including some of the more recently developed systems dedicated to assessment of the distal radius. The accuracy, precision and normative values they provide are presented. Responses to different forms of therapies as well as the ability to discriminate or predict osteoporotic fractures are also assessed. Low radiation dose, comfortable and fast handling, moderate cost, and a strong association with the risk of non-spine fractures, promote the use of forearm scanning as a widely applied screening procedure for the detection of generalised osteoporotic bone loss. However, a higher accuracy of fracture risk prediction at the spine or at the hip can be achieved by a direct bone density measurement at these sites. The monitoring of treatment at the distal forearm appears to require a longer follow-up time due to its decreased responsiveness compared with such highly trabecular load-bearing sites as the spine and the proximal femur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001980050068
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanische Einflüsse auf die Callusheilung (2000)
    Springer
    Der Chirurg 71 (2000), S. 989-994 
    Details
    ISSN: 1433-0385
    Keywords: Schlüsselwörter: Biomechanik ; Callus ; Knochenheilung ; Stabilität ; Biologie. ; Keywords: Biomechanics ; Callus ; Bone healing ; Stability ; Biology.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract. Interfragmentary movement and size of the fracture gap influence fracture healing. Limited movements promote callus formation and may result in increased mechanical stability. Although larger movements still promote callus formation, the bony consolidation of the fracture is hampered. Fracture healing is also hampered if the size of the fracture gap is too large. A combination of large movement and large gap bears the risk of non-union. Therefore, having in mind a minimally invasive surgical approach, one should strive for good reduction of the fracture ends and flexible yet stable osteosynthesis. Dynamization of the fracture by enabling axial movement will close the fracture gap, stimulate tissue differentiation and possibly accelerate the healing process. External mechanical stimulation, however, has not been shown to effectively enhance the healing process under flexible fixation or in load-bearing patients.
    Notes: Zusammenfassung. Kleine interfragmentäre Bewegungen stimulieren die Callusheilung während zu große Bewegungen häufig eine knöcherne Überbrückung verhindern. Bei großen Frakturspalten kommt es zu einer Verzögerung von Callusbildung und Frakturüberbrückung. Die Gefahr einer Pseudarthrose besteht bei zu großer interfragmentärer Bewegung (Instabilität) und zu großen Frakturspalten. Trotz aller Bestrebungen zu gewebeschonenden Operationstechniken ist deshalb eine gute Reposition und eine flexible aber stabile Osteosynthese die Voraussetzung für eine komplikationsfreie Callusheilung. Eine Dynamisierung durch zusätzliche axiale Bewegung kann sich positiv auswirken, weil dadurch Frakturspalten geschlossen werden und der Reiz zur Callusdifferenzierung erhöht wird. Eine externe mechanische Stimulation scheint bei flexiblen Osteosynthesen und aktiven Patienten nicht erforderlich.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001040051172
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitative Assessment of Experimental Fracture Repair by Peripheral Computed Tomography (1997)
    Springer
    Calcified tissue international 60 (1997), S. 194 -199 
    Details
    ISSN: 1432-0827
    Keywords: Key Words: Fracture repair — Biomechanics — Quantitative computed tomography — Histology — Radiography.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. An experimental fracture model was used to assess bone mineral density at the fracture site by peripheral computed tomography and to compare the model with biomechanical, histological, and radiographic methods for the quantification of the fracture repair process. Transverse osteotomies in the mid-diaphysis of 28 tibia of sheep were externally fixed and mineral densities, cross-sectional areas, flexural rigidities, tissue composition, and projected callus area were calculated after 9 weeks of healing time. BMD measured by pQCT was strongly correlated with histologically determined percentages of mineralized tissue in the osteotomy gap (R 2= 0.71) and in the periosteal callus (R 2= 0.62). The percentage of mineralized tissue in the osteotomy gap was the best predictor of the flexural rigidity of the tibiae (R 2= 0.74). Because of high correlations with the histological findings, the volumetric BMD at the level of the osteotomy gap was also strongly correlated with the biomechanical findings (R 2= 0.70). Neither the cross-sectional area in pQCT nor the projected callus area in plane film radiography were positively correlated to the flexural rigidity of the tibiae. Quantitative computed tomography proved to be a successful estimator for the prediction of the mechanical stability of healing bones. The noninvasive procedure is a reliable tool for the quantification of the fracture repair process in experimental studies and may be useful for treatment decisions in particular clinical situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900213
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  • 7
    Electronic Resource
    Electronic Resource
    Letters to the Editor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 285-287 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770020412
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    Paper (German National Licenses)
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