[Show abstract][Hide abstract] ABSTRACT: The standard diagnostic technique for assessing osteoporosis is dual X-ray absorptiometry (DXA) measuring bone mass parameters. In this study, a combination of DXA and trabecular structure parameters (acquired by computed tomography [CT]) most accurately predicted the biomechanical strength of the proximal femur and allowed for a better prediction than DXA alone.
An automated 3D segmentation algorithm was applied to determine specific structure parameters of the trabecular bone in CT images of the proximal femur. This was done to evaluate the ability of these parameters for predicting biomechanical femoral bone strength in comparison with bone mineral content (BMC) and bone mineral density (BMD) acquired by DXA as standard diagnostic technique.
One hundred eighty-seven proximal femur specimens were harvested from formalin-fixed human cadavers. BMC and BMD were determined by DXA. Structure parameters of the trabecular bone (i.e., morphometry, fuzzy logic, Minkowski functionals, and the scaling index method [SIM]) were computed from CT images. Absolute femoral bone strength was assessed with a biomechanical side-impact test measuring failure load (FL). Adjusted FL parameters for appraisal of relative bone strength were calculated by dividing FL by influencing variables such as body height, weight, or femoral head diameter.
The best single parameter predicting FL and adjusted FL parameters was apparent trabecular separation (morphometry) or DXA-derived BMC or BMD with correlations up to r = 0.802. In combination with DXA, structure parameters (most notably the SIM and morphometry) added in linear regression models significant information in predicting FL and all adjusted FL parameters (up to R(adj) = 0.872) and allowed for a significant better prediction than DXA alone.
A combination of bone mass (DXA) and structure parameters of the trabecular bone (linear and nonlinear, global and local) most accurately predicted absolute and relative femoral bone strength.
Full-text · Article · Oct 2009 · Osteoporosis International
[Show abstract][Hide abstract] ABSTRACT: High-resolution magnetic resonance imaging (hrMRI) has recently made it possible to evaluate trabecular bone structure in vivo. Despite obvious gender differences in fracture incidence at the distal radius, little is known about gender differences in trabecular bone microarchitecture and its relationship to the structural strength of the forearm. The aim of this study was to determine trabecular bone structure in the distal radius of elderly women and men and its correlation with failure loads of the distal radius as determined in a fall configuration. Specifically, we tested the hypotheses that structural indices differ between women and men and that they offer information that is independent from BMD for predicting structural strength. Intact right arms were obtained from 73 formalin-fixed cadavers (age 80+/-11 years, 43 women, 30 men). Trabecular structural indices (apparent bone volume fraction [app. BV/TV], trabecular number [app. Tb.N], trabecular separation [app. Tb.Sp], trabecular thickness [app. Tb.Th] and fractal dimension [Frac.Dim]) were assessed in the distal metaphysis, using hrMRI with 156 microm in-plane resolution and proprietary digital image analysis, while BMD was measured with dual X-ray absorptiometry (DXA). Women displayed significantly lower BMD (-29.8%, p <0.001), app. BV/TV (-8.2%, p <0.05) and app. Tb.Th (-10.2%, p <0.001) than men, whereas app. Tb.N, app. Tb.Sp. and fractal dimension did not differ significantly. Structural parameters differed between normal and osteopenic women (BV/TV: -11%, p <0.01; Tb.Th: -8%, p <0.001) and between normal and osteoporotic women BV/TV: -21%, p <0.001; Tb.Th: -16%, p <0.001). App. BV/TV, app. Tb.Th and fractal dimension provided information independent from BMD in the prediction of radial failure loads in multiple regression models. These findings imply that it should be of clinical interest to monitor both bone mass and trabecular microstructure for predicting osteoporotic fracture risk.
No preview · Article · Sep 2005 · Osteoporosis International
[Show abstract][Hide abstract] ABSTRACT: Today, mothers-to-be with an uncomplicated pregnancy are advised to practice sports on a regular basis. If they follow this advice, they put on less weight and recover more quickly from the stresses and strains of parturition, thanks to their higher level of general fitness. In addition, practicing sports helps to prevent postural damage, back pain, varices and thrombosis. The most suitable forms of sport are those of the aerobic type, such as jogging, swimming, cycling or aerobic calisthenics. However, exercises in the fitness studio and moderate strength training are also admissible provided that consideration is given to contraindications and warning signals.
No preview · Article · May 2005 · MMW Fortschritte der Medizin
[Show abstract][Hide abstract] ABSTRACT: The diagnosis of osteoporosis is generally based on the assessment of bone mineral content with dual X-ray absorptiometry (DXA) but does not account for the spatial distribution and inherent material properties of the tissue. Peripheral quantitative computed tomography (pQCT) permits one to measure the compartment-specific density and geometry-based parameters of cortical bone. Quantitative ultrasound (QUS) parameters are associated with material properties of cortical bone. The purpose of this study was to test the hypothesis that pQCT and cortical QUS provide additional information to DXA in predicting structural strength of the distal radius. The intact right arm and the isolated left radius were harvested from 70 formalin-fixed cadavers (age 79+/-11 years). The bone mineral content (BMC) was assessed with DXA at the radial metaphysis and shaft. pQCT was also used at the metaphysis and the shaft, while QUS was employed only at the shaft. The failure loads of the radius were assessed by use of a 3-point bending test (isolated radius) and a complex fall simulation (intact arm). The BMC (DXA) displayed a correlation of r=0.96 with the failure moments in 3-point bending ( P<0.001). The correlation between failure load and geometry-based parameters (pQCT) ranged from r=0.85 to r=0.96 and was r=0.64 for the speed of sound (QUS) ( P <0.001). Cortical thickness (pQCT) improved the prediction marginally (r=0.964) in combination with DXA. For the fall simulation, the correlation coefficients were r=0.76 for BMC (DXA) of the shaft, r=0.83 for metaphyseal bone content (pQCT), r=0.55 for QUS, and ranged from r=0.59 to r=0.74 for geometry-based parameters at the shaft (pQCT). pQCT and QUS parameters provided no significant improvement versus DXA alone. Measurement of bone mass by DXA or pQCT thus appears to be sufficient as a surrogate of mechanical strength and fracture risk of the distal radius.
No preview · Article · Jun 2004 · Osteoporosis International
[Show abstract][Hide abstract] ABSTRACT: Der vorliegende bersichtsartikel beschreibt den aktuellen Stand des Themas Schwangerschaft und Sport und gibt konkrete Empfehlungen, welche Sportarten in der Schwangerschaft in welchem Umfang betrieben werden knnen. Zunchst werden relevante muskuloskelettale, kardiorespiratorische, thermoregulatorische und endokrine Vernderungen whrend der Schwangerschaft beschrieben. In den folgenden Abschnitten werden die Auswirkungen von sportlicher Aktivitt whrend der Schwangerschaft auf den mtterlichen Organismus und den Organismus des Ungeborenen diskutiert. Den Themen Leistungssport und Krperliche Aktivitt im Wasser sind eigene Abschnitte gewidmet. Der Artikel schliet mit Empfehlungen zu spezifischen Sportarten, dem Ausdauer- und Krafttraining in der Schwangerschaft. Kontraindikationen und Warnsignale whrend physischer Aktivitt werden beschrieben. Bei unaufflligem Schwangerschaftsverlauf berwiegen die Vorteile sportlicher Aktivitt klar die potenziellen Risiken. Sogar bislang krperlich inaktiven Schwangeren ist daher der Beginn von leichter sportlicher Aktivitt im 2. Trimenon zu empfehlen.This review article summarizes work on physical exercise and sports in pregnancy and gives specific recommendations, which types of sports can be performed to what extent during pregnancy. First we summarize relevant musculoskeletal, cardiorespiratory, theromoregulatory and endocrine changes during pregnancy. Subsequent parts of the article describe the effect of physical activity on the maternal and fetal organism. Distinct paragraphs discuss athletics and physical activity in water. The article gives recommendations with regard to specific types of sport, endurance training, and weight training during pregnancy. Contraindications and warning signals during physical activity are described. During uncomplicated pregnancy advantages of sportive activity clearly exceed potential risks. Therefore, previously inactive pregnant women are recommended to take up mild physical exercise during the 2nd trimenon.
[Show abstract][Hide abstract] ABSTRACT: Osteoporotic fractures are a severe medical problem that dominantly affects postmenopausal women. Effective therapy for reducing fracture rates is available today and, therefore, non-invasive estimates of the individual fracture risk represent an important challenge for medical diagnostics. The objective of the current article is to comprehensively review methods for quantitative measurements of bone properties and their value in predicting individual fracture risk. We report epidemiologic findings in the context of osteoporotic fractures and give a technical description of current diagnostic methods, including projectional X-ray techniques (DXA), tomographic X-ray techniques (QCT and pQCT), quantitative ultrasound (QUS), and magnetic resonance imaging (MRI). We summarize cross-sectional and prospective clinical trials and results of recent experimental findings in estimating mechanical failure loads, using different quantitative methods. Based on the existing data we conclude that DXA continues to be a reference method for diagnosing osteporosis. No improvement has so far been demonstrated for tomographic X-ray techniques. QUS is an attractive diagnostic tool in private practice in primary risk evaluation. However, measurements are confined to the peripheral skeleton; they must therefore be interpreted with caution and may have to be supplemented by DXA. Further improvements in evaluating fracture risk may be achieved by analyzing trabecular microarchitecture with high resolution CT, pQCT and MRI, and by computer simulation techniques. These methods are the focus of current research.
No preview · Article · Apr 2004 · Geburtshilfe und Frauenheilkunde
[Show abstract][Hide abstract] ABSTRACT: Osteoporotic vertebral fractures typically have a gradual onset, frequently remain clinically undetected, and do not seem to be related to traumatic events. The osteoporotic vertebrae may therefore be expected to display a less "optimal" bone architecture, leading to an uneven load distribution over the bone material. We evaluated the trabecular load distribution in an osteoporotic and a healthy vertebra under normal daily loading by combining three recent innovations: high resolution computed tomography (microCT) of entire bones, microfinite element analyses (microFEA), and parallel supercomputers. Much to our surprise, the number of highly loaded trabeculae was not higher in the osteoporotic vertebra than in the healthy one under normal daily loads (8% and 9%, respectively). The osteoporotic trabeculae were more oriented in the longitudinal direction, compensating for effects of bone loss and ensuring adequate stiffness for normal daily loading. The increased orientation did, however, make the osteoporotic structure less resistant against collateral "error" loads. In this case, the number of overloaded trabeculae in the osteoporotic vertebra was higher than in the healthy one (13% and 4%, respectively). These results strengthen the paradigm of a strong relationship between bone morphology and external loads applied during normal daily life. They also indicate that vertebral fractures result from actions like forward flexion or lifting, loads that may not be "daily" but are normally not traumatic either. If future clinical imaging techniques would enable such high-resolution images to be obtained in vivo, the combination of microCT and microFEA would produce a powerful tool to diagnose osteoporosis.
[Show abstract][Hide abstract] ABSTRACT: Osteoporotic fractures represent an important medical and socioeconomic problem. To determine the indivual risk before the advent of a fracture, several osteodensitometric measurement techniques have been developed. These methods differ in their physical background, in measurement site, output parameters, and costs. Biomechanical tests represent an efficient tool for preclinical evaluation of these techniques, because they permit to determine the mechanical competence of relevant bones and their correlation with densitometric parameters. The objective of this review was therefore to summarize experimental studies that have evaluated osteodensitometric techniques based on biomechanical testing. In vertebrae, tests have been performed on planoparallel sections (without endplates), on whole vertebral bodies with and without discs, and on functional 2- or 3-segment units. In the proximal femur, tests have been conducted with a vertical loading direction (parallel to the shaft), by simulating the stance phase of gate, or a sideways fall on the greater trochanter (side impact). At the distal radius, tests have been performed in axial compression, under 3-point-bending, and simulating a fall on the outstretched hand. Experimental studies show that site-specific measurements can predict the mechanical competence of relevant skeletal regions with moderate to high accuracy, relatively independent of the densitometric method and mechanical test employed. Due to a high degree of heterogeneity of mechanical competence throughout the skeleton, non-sitespecific measurements generally display a lower predictive value. Quantitative ultrasound, geometry-based cortical, and microstructural trabecular parameters can improve the prediction of failure loads, when being combined with the sitespecific bone mass.
[Show abstract][Hide abstract] ABSTRACT: This experimental study compares geometric and densitometric properties of cortical and trabecular bone at the lower limb and the distal radius with those at the femoral neck, and evaluates their ability to predict mechanical failure loads of the proximal femur. One hundred five cadavers were examined with peripheral quantitative computed tomography (LpQCT), with measurements being performed in situ at the distal radius (4%, 20%, 33%), at the distal and proximal tibia, at the tibial and femoral shaft, and at the distal femur. Ex situ measurements were obtained at the femoral neck and at the proximal femoral shaft. Pairs of femora were mechanically tested in a vertical loading and a side impact (fall) configuration. The total (cross-sectional) bone mineral content and trabecular density, but not the cortical properties, displayed a higher association between the femoral neck and the peripheral lower limb than between the neck and the distal radius. Approximately 50%-60% of the variability of femoral failure loads (and >80% of trochanteric side impact fractures) were predicted by in vitro measurements at the neck. Geometric cortical parameters and density contributed independently and significantly to femoral strength. Measurements at the peripheral skeleton explained, however, only 30%-45% of the variability of femoral failure, with no significant difference between the lower limb and the distal radius. At peripheral sites, a combination of geometric and densitometric variables was slightly superior to bone mineral content alone in predicting failure in vertical loading, but this was less evident for cervical side impact fractures. The results show that a stronger association of total bone mineral content and trabecular density between the femoral neck and the lower limb does not translate into improved prediction of femoral strength from measurements at the lower limb vs. those at the distal radius.
[Show abstract][Hide abstract] ABSTRACT: In this study we explore the hypothesis that estimates of failure loads in the thoracic spine by lumbar dual energy X-ray absorptiometry (DXA) are compromised of skeletal heterogeneity throughout the spine and artifacts of spinal DXA. We studied the correlation between mechanical failure loads of thoracic and lumbar vertebrae, and that of in situ vs. ex situ lumbar DXA with thoracic and lumbar fracture loads, respectively. One hundred and nineteen subjects (76 female, age 82+/-9yr; 43 male, age 77+/-11yr) were examined under in situ conditions (anterior-posterior direction), the scans being repeated ex situ (lateral projection) in 68 cases. The failure loads of thoracic vertebrae (T) 6 and 10, and lumbar vertebra (L) 3 were determined in axial compression, using a functional 3-segment unit. The correlation between thoracic failure loads (T6 vs. T10) was significantly (p<0.01) higher (r=0.85) than those between thoracic and lumbar vertebrae (r=0.68 and 0.61, respectively). Lateral ex situ DXA displayed a significantly higher correlation (p<0.05) with lumbar vertebral fracture loads than in situ anterior-posterior DXA (r=0.85 vs. 0.71), but the correlation of thoracic failure loads with lateral ex situ lumbar DXA was similar to that obtained in situ in anterior-posterior direction (r=0.69 vs. 0.69 for T10, and r=0.61 vs. 0.65 for T6). The correlation between fracture loads of different spinal segments, and between DXA and failure loads was not significantly different between men and women. The results demonstrate a substantial heterogeneity of mechanical competence throughout the spine in elderly individuals. Because of the high incidence of fractures in the thoracic spine, these findings suggest that, clinically, lateral DXA involves no relevant advantage over anterior-posterior measurements of the lumbar spine.
No preview · Article · May 2001 · Journal of Biomechanics
[Show abstract][Hide abstract] ABSTRACT: The objective of this study was to determine the effect of fixation, soft tissues, and scan projection on bone mineral measurements with dual energy X-ray absorptiometry (DXA). In seven fresh cadavers, DXA scans were obtained within 48 hours of death and after 10 months of fixation with 5% formalin/95% ethanol. The measurements showed a high linear relationship (r2 > 0.97; SEE% < 10%), with no significant deviation after fixation (except for total body BMD: -3.1%). In 14 specimens, the precision of femoral and spinal analyses was determined under in situ and ex situ conditions. There was no significant difference between ex situ and in situ reproducibility, the coefficient of variation being < 3% for the BMC and < 2% for the BMD (except at the greater trochanter). The effect of the soft tissues and scan projection was assessed in 83 cadavers aged 80.4 +/- 10.3 years. The soft tissues had only a small effect on analyses of the total femur (r2 > 0.90; SEE% < 9%), but led to more substantial deviations in regional femoral analyses and in the spine (r2 = 0.78-0.90; SEE% = 8-22%). Comparing lateral with anterior-posterior (AP) spinal scans, the vertebral bodies were found to occupy 40.2 +/- 7.2% of the BMC, and 62.0 +/- 11.2% of the BMD, the ranges being 26-58%, and 38-91%, respectively. There were large deviations from linearity between in situ AP and ex situ lateral spinal scans with r2 values of 0.63 and 0.73 for BMD and BMC (SEE% = 52% and 27% relative to the vertebral body), respectively.
No preview · Article · Apr 2001 · Calcified Tissue International