Dual-photon X-ray Absorptiometry Research Articles

Comparison of methods for diagnosing sarcopenia in patients with rheumatoid arthritis

Background. Sarcopenia in patients with rheumatoid arthritis (RA) occurs in connection with the chronic inflammatory process, hormonal therapy, and limitation of physical activity due to pain syndrome. For RA patients, it is important to preserve muscle mass and function to reduce the risk of disability and improve quality of life. The research purposed to assess muscle mass and function in RA patients with a comparison of me­thods for determining skeletal muscle mass recommended by ­EWCSOP2. ­Materials and methods. A total of 44 persons were exa­mined, 32 were patients with RA, and 12 ones were healthy persons (the control group). The following methods were used in the study: the SARC-F questionnaire, the determination of the appendicular mass of skeletal muscles using dual-photon X-ray absorptiometry (DXA), the percentage of muscle and fat tissue using bioimpe­dancemetry, the determination of the cross-sectional area of the lumbar muscle using computer tomography (CT), physical performance tests. Patients with RA were divided into 3 groups: group A (11 persons) — questionnaire (SARC-F), assessment of skeletal muscle strength and determination of muscle mass using DXA was performed; group B (11 patients) — questionnaire (SARC-F), assessment of skeletal muscle strength and determination of muscle mass using bioimpedancemetry; group C (10 persons) — questionnaire (SARC-F), assessment of skeletal muscle strength and determination of muscle mass using CT. Results. All indices of physical performance tests and instrumental methods of assessing muscle mass were significantly worse in patients with RA compared to the control group. Sarcopenia was diagnosed in 50 % of patients with RA, 6 cases in group A (the average value of appendicular lean mass was 15.7 kg in them, in the control group — 21 kg), 5 in group B (the average values of the proportion of muscle mass were 21.2 compared to 29.3 % in the control group) and 5 in group C (the average percentage of muscle mass was 49.46 %, in the control group 58.32 %). ­Conclusions. Each of the methods of assessing the mass of skeletal muscles has proven its ability in the diagnosis of sarcopenia. Improving the efficiency of diagnosing sarcopenia in patients with RA will improve the response to the treatment of the underlying disease and improve the quality of life of patients.

Mathematical model of the bone biological age based on the bone mineral density and quality indicex and Ukrainian FRAX model

Background. It is well-known that with aging there is a loss of bone mass and its strength, which leads to the development of osteoporosis and its complications. The aim of the study was to create a modern mathematical model for determining the biological age of the bone system, taking into account indices of bone mineral density (BMD) and quality and the FRAX® questionnaire. Materials and methods. 77 women and 44 men aged 30 to 90 years without any significant somatic pathology were included in the study. Patients were divided into 4 age groups: 30–44 years old — young, 45–59 years — mature, 60–74 years — old age and 75–90 years— senile age. We measured the parameters of BMD in the different areas of the skeleton by means of the dual-photon X-ray absorptiometry (DXA, “Prodigy”). The 10-year probability of major osteoporotic and hip fractures was measured using the Ukrainian version of the FRAX®. Statistical analysis was performed in the Statistica 7.0 program (StatSoft Inc., USA). Results. The dependence of the indices of BMD and bone quality, risk of osteoporotic fractures on age and the need for their early determination in young people to predict the risk of osteoporosis and its complications have been proven. The coefficient of determination of the R2 model was 0.62, which indicates that 62% of the variance of the “Age” can be explained by the predictors included in the model (DXA and FRAX indices); adjusted R2 index was 0.59 (p<0.001), which indicates high significance of the model. Conclusions. The developed model for estimating the bone biological age has high accuracy and can be used to assess the risk of osteoporosis and its complications in young people for the purpose of predicting the disease.

Artificial neural network analysis of bone quality DXA parameters response to teriparatide in fractured osteoporotic patients.

Teriparatide is a bone-forming therapy for osteoporosis that increases bone quantity and texture, with uncertain action on bone geometry. No data are available regarding its influence on bone strain. To investigate teriparatide action on parameters of bone quantity and quality and on Bone Strain Index (BSI), also derived from DXA lumbar scan, based on the mathematical model finite element method. Forty osteoporotic patients with fractures were studied before and after two years of daily subcutaneous 20 mcg of teriparatide with dual X-ray photon absorptiometry to assess bone mineral density (BMD), hip structural analysis (HSA), trabecular bone score (TBS), BSI. Spine deformity index (SDI) was calculated from spine X-ray. Shapiro-Wilks, Wilcoxon and Student's t test were used for classical statistical analysis. Auto Contractive Map was used for Artificial Neural Network Analysis (ANNs). In the entire population, the ameliorations after therapy regarded BSI (-13.9%), TBS (5.08%), BMD (8.36%). HSA parameters of femoral shaft showed a worsening. Dividing patients into responders (BMD increase >10%) and non-responders, the first presented TBS and BSI ameliorations (11.87% and -25.46%, respectively). Non-responders presented an amelioration of BSI only, but less than in the other subgroup (-6.57%). ANNs maps reflect the mentioned bone quality improvements. Teriparatide appears to ameliorate not only BMD and TBS, but also BSI, suggesting an increase of bone strength that may explain the known reduction in fracture risk, not simply justified by BMD increase. BSI appears to be a sensitive index of TPD effect. ANNs appears to be a valid tool to investigate complex clinical systems.

Bone strain index reproducibility and soft tissue thickness influence: a dual x-ray photon absorptiometry phantom study

BackgroundBone strain index (BSI) is a tool measuring bone strain, derived from dual x-ray photon absorptiometry. It is able to characterise an aspect of bone quality that, joined to the quantity and quality parameters of bone mineral density (BMD) and trabecular bone score (TBS), permits an accurate definition of fracture risk. As no data are available about BSI precision, our aim was to assess its in vitro reproducibility.MethodsA Hologic spine phantom was used to perform BSI scans with three different scan modes: fast array (FA), array (A), and high definition (HD). Different soft tissue thicknesses (1, 3, 6 cm) of fresh pork rind layers as a surrogate of abdominal fat were interposed. For each scan mode, the phantom was consecutively scanned 25 times without repositioning.ResultsIn all scan modes (FA, A, HD) and at every fat thickness, BSI reproducibility was lower than that of BMD. The highest reproducibility was found using HD-mode with 1 cm of pork rind and the lowest one using HD-mode with 6 cm of pork rind. Increasing fat thickness, BSI reproducibility tended to decrease. BSI least significant change appeared to be about three times that of BMD in all modalities and fat thicknesses. Without pork rind superimposition and with 1-cm fat layer, BSI reproducibility was highest with HD-mode; with 3 or 6 cm fat thickness, it was higher with A-mode.ConclusionsBSI reproducibility was worse than that of BMD, but it is less sensitive to fat thickness increase, similarly to TBS.

Determinants of bone damage: An ex-vivo study on porcine vertebrae.

Bone’s resistance to fracture depends on several factors, such as bone mass, microarchitecture, and tissue material properties. The clinical assessment of bone strength is generally performed by Dual-X Ray Photon Absorptiometry (DXA), measuring bone mineral density (BMD) and trabecular bone score (TBS). Although it is considered the major predictor of bone strength, BMD only accounts for about 70% of fragility fractures, while the remaining 30% could be described by bone “quality” impairment parameters, mainly related to tissue microarchitecture. The assessment of bone microarchitecture generally requires more invasive techniques, which are not applicable in routine clinical practice, or X-Ray based imaging techniques, requiring a longer post-processing. Another important aspect is the presence of local damage in the bony tissue that may also affect the prediction of bone strength and fracture risk. To provide a more comprehensive analysis of bone quality and quantity, and to assess the effect of damage, here we adopt a framework that includes clinical, morphological, and mechanical analyses, carried out by means of DXA, μCT and mechanical compressive testing, respectively. This study has been carried out on trabecular bones, taken from porcine trabecular vertebrae, for the similarity with human lumbar spine. This study confirms that no single method can provide a complete characterization of bone tissue, and the combination of complementary characterization techniques is required for an accurate and exhaustive description of bone status. BMD and TBS have shown to be complementary parameters to assess bone strength, the former assessing the bone quantity and resistance to damage, and the latter the bone quality and the presence of damage accumulation without being able to predict the risk of fracture.

Assessment of Bone Quality in Osteoporosis Treatment with Bone Anabolic Agents: Really Something New?

Osteoporosis is a chronic pathologic condition, particularly of the elderly, in which a reduction of bone mineral density (BMD) weakens bone, leading to the so-called fragility fractures, most often of spine and femur. The gold standard exam for the quantitative measurement of BMD is the dual X-ray photon absorptiometry (DXA), a radiological method. However, a relevant number of fragility fractures occurs in the range of normal BMD values, meaning that also qualitative aspects of bone play a role, namely bone architecture and bone geometry. Bone structure is investigated by microCT and histomorphometry, which necessitate an invasive approach with a biopsy, usually taken at the iliac crest, not the typical site of fragility fractures. New tools, trabecular bone score (TBS) and hip structural analysis (HSA), obtained during DXA, can supply informations about bone structure of spine and femur, respectively, in a not invasive way. Therapy of osteoporosis is based on two types of drugs leading to an increase of BMD: antiresorptive and anabolic treatments. The antiresorptive drugs inhibit the osteoclasts, whereas teriparatide and, in part, strontium ranelate ameliorate bone structure. The present review deals with the relation between the anabolic drugs for osteoporosis and the cited new tools which investigate bone architecture and geometry, in order to clarify if they represent a real advantage in monitoring efficacy of osteoporosis' treatment. Data from the studies show that increases of TBS and HSA values after anabolic therapy are small and very close to their least significant change at the end of the usual period of treatment. Therefore, it is questionable if TBS and HSA are really helpful in monitoring bone quality and in defining reduction of individual fragility fracture risk during osteoporosis treatment with bone anabolic agents.

Judo Practice in Early Age Promotes High Level of Bone Mass Acquisition of Growing Boys' Skeleton

The current study aimed to exhibit effects of judo training for at least 2 yr on bone mass parameters in growing boys. Our population was composed of one hundred and thirty boys in tanner stage 1 and aged 10.52 ± 0.86 yr. Eleven judo players were therefore, excluded from the study because they do not have participate regularly to the judo training sessions during the last 2 yr. The resting sample was divided into two groups: 50 judo players (JU group) and 69 controls (C group). Bone mineral density (BMD), bone mineral content (BMC), and bone area (BA) were evaluated by using dual-photon X-ray absorptiometry on weight-bearing sites: the whole body, lumbar spine (L2-L4), legs, femoral necks and hips and on the non-weight bearing sites: arms and radiuses. Our findings displayed that judo participation was markedly associated with greater values of bone mass parameters in young judo players than control group. Accordingly, the BMD and BA results exhibited significant differences in the whole body, legs, dominant total hip, arms and both whole radiuses in addition to the dominant femoral neck, the non-dominant total hip and except the non-dominant whole radius for the BMC parameter. Additionally, data of the subject within t test has shown significant differences of bone mass parameters only in the non weight-bearing sites in the judo players without any obvious variation in the controls. Differences of BMD observed on the dominant arm and whole radius in addition to the increased BMC values showed in the dominant whole radius compared with their contra-lateral sites in judo players without any marked variation of BA parameters in all sites in both groups. In growing boys, judo practice was obviously associated with osteogenic effects in specific sites.

Long-Term Proton Pump Inhibitor Use Is Not Associated With Changes in Bone Strength and Structure.

Multiple studies have reported an association between proton pump inhibitor (PPI) use and fracture. However, the causality of this association is questionable, as there is not a well defined mechanism of action, nor is there evidence of an effect on PPIs on areal bone mineral density (aBMD) using dual photon X-ray absorptiometry (DXA). It is possible that PPIs may induce changes in bone structure which would predispose to fracture in the absence of changes in aBMD. We used three-dimensional quantitative computed tomography (3D-QCT) imaging to determine if long-term PPI use was associated with structural changes in bone independent of aBMD. We enrolled a sample of long-term (≥5 years) PPI users matched to a similar cohort of persons with no PPI use in the previous 5 years. All subjects underwent assessment of aBMD using DXA, volumetric BMD using 3D-QCT, as well as markers of bone metabolism. Measures of bone strength, including buckling ratio and section modulus, were also compared between the two samples. 104 subjects were enrolled (52 PPI users and 52 PPI non-users). There were no differences detected in standard BMD, volumetric BMD, markers of bone metabolism or measures of bone strength between the two groups. Long-term PPI use is not associated with any changes in bone mineral density or bone strength that would predispose to an increased risk of fracture. These findings provide further evidence that the association between PPI use and fracture is not causal.

Prevalence of low bone mineral density in adolescents and adults with cystic fibrosis.

The aim of this cross-sectional study was to evaluate the prevalence of low bone mass density in cystic fibrosis patients as well as to evaluate the factors associated with bone mass in such patients. Bone mass density was measured by dual-photon X-ray absorptiometry of lumbar spine (L1-L4), in patients ≤19 years old, or lumbar spine and femur (total and neck) in patients ≥20 years old. Evaluations of nutritional status, biochemical parameters, and lung function were performed. Medication data were obtained from medical records. Fifty-eight patients were included in the study (25 males/ 33 females), mean age 23.9 years (16-53 years). The prevalence of bone mass below the expected range for age at any site was 20.7%. None of the subjects had history of fracture. Lumbar spine Z-score in cystic fibrosis patients correlated positively with body mass index (r= 0.3, p=0.001), and forced expiratory volume in the first second (% predicted) (r=0.415, p=0.022). Mean lumbar spine Z-score was higher in women (p=0.001), in patients with no pancreatic insufficiency (p=0.032), and in patients with no hospitalization in the last 3 months (p=0.02). After multivariate analysis, body mass index (p= 0.001) and sex (p=0.001) were independently associated with Z-score in lumbar spine. Low bone mass is a frequent problem in patients with CF, being independently associated with body mass index, and male sex.

Thalassemic osteopathy: A new marker of bone deposition

Osteopathy represents a prominent cause of morbidity in patients with beta-thalassemia major (TM) and manifests as osteopenia/osteoporosis. Biochemical turnover markers (BTMs) are considered a useful, non-invasive tool for the clinical follow-up of osteoporotic patients; they can provide a dynamic view of the remodeling process and give information on the metabolic activity of bone tissue as well as on the pathogenesis of bone loss. The amino-terminal pro-peptide of type I procollagen (P1NP) is a recently introduced marker that is considered the most sensitive index of bone formation. Although demonstrated in several categories of patients with bone disease, there is little information on the clinical usefulness of this bone formation index in thalassemic patients. We evaluated the P1NP levels of 53 adult patients with b-thalassemia major (21 males and 32 females, mean age 34.5 ± 5.7, range 22-46 years) and associated osteopathy. We investigated the correlation between P1NP and bone condition as examined by dual X-ray photon absorptiometry and with BTMs expressing bone resorption and bone mineralization (carboxyterminal collagen cross-linked (CTX) terminal regions of type I collagen and osteocalcin, respectively). P1NP serum levels were correlated with CTX levels (r=0.545, p<0.001); the results were unchanged when males and females, as well as osteoporotic and osteopenic subgroups, were considered separately. No correlation was demonstrated neither between OC and CTX (r=0.17, p=ns), nor between P1NP and OC levels (r=0.11, p=ns). No correlation was demonstrated among the P1NP/CTX ratio and age, OC or densitometric values and no difference was found in the same ratio between osteopenic (0.19 ± 0.16) and osteoporotic (0.15 ± 0.14) patients. Similar results were obtained for the OC/CTX ratio, as it was not correlated with age, P1NP or densitometric values. This is the first report of circulating P1NP in patients with TM-associated osteoporosis. P1NP and CTX assays show good precision and low analytical CV, and, compared to other markers, they can acceptably reflect bone metabolic processes and promptly respond to antiosteoporotic treatments. We trust that this sensitive marker can be useful in the assessment of treatment efficacy and can overcome the pitfalls due to wide variability in the normal values of most BTMs that create difficulty in pinpointing the individual patient's response.

Specific sites of bone expansion depend on the level of volleyball practice in prepubescent boys.

The purpose of this study was to investigate the effect of 18 months of high and low levels of volleyball practice on bone acquisition. 130 prepubescent boys (mean age 11.4 ± 0.7) were divided into a high-level training group (HLG), low-level training group (LLG), and controls. Bone mineral content (BMC) and bone area at the whole body, lumbar spine L2-L4, femoral neck of the dominant leg, and right and left radius were measured using dual-photon X-ray absorptiometry. Enhanced BMC resulted from high-training volleyball activity in all measured sites except the third left and right distal radius, which is not modified by low-level training in prepubescent players but it was accompanied by a bone area expansion in radius and weight-bearing sites for the HLG, and in legs, whole right and left radius for the LLG. Significant improvement of skeletal tissues is associated with the intensity and duration of volleyball training.

Association between bile acid turnover and osteoporosis in postmenopausal women

The intestinal absorption of vitamin D is linked to bile acid absorption. This link may be abnormal in patients with osteoporosis. The aim of this study was to investigate a possible relation between osteoporosis and bile acid turnover, measured as whole-body Se-75-HCAT retention (WBR), in postmenopausal women. Whole-body counts were recorded using an uncollimated gamma camera 3 h and 7 days after oral administration of Se-75-homocholic acid taurine (Se-75-HCAT) in 16 women aged 58-85 years with dual-photon X-ray absorptiometry (DEXA)-proven osteoporosis. WBR was expressed as physical decay-corrected counts at 7 days as a percentage of the counts at 3 h. Seven patients had unexplained diarrhoea. Six patients (five with diarrhoea) had WBR less than 19%. There was a significant difference in DEXA t-score between women with and without diarrhoea (P<0.02). There was a significant negative correlation (R s=-0.58; P<0.02) between WBR and alcohol consumption rated on a three-point scale: <1, 2-7 and >7 U/week. Our results indicate an association between osteoporosis and diarrhoea that may be the result of abnormal bile acid turnover. The role of alcohol requires further investigation.

Frakturen bei verminderter Knochendichte, Hyperkalziurie und Osteolysen - Osteoporose oder Syndrom?

At first osteomalacia was presumed clinically and radiologically in a 49-year old female patient. Radiologically there were multiple suspected neoplastic osseous infiltrations, which was not confirmed by subsequent investigations. There were no indications of osteomalacia or malabsorption in the laboratory exams. The multiple microfractures and osteolysis of the fingers, the toes, the wrist and the tarsus detected with varius imaging techniques were ascribed to an acroosteolysis. Osteoporosis of both femoral necks was also present in dual photon X-ray absorptiometry densitometry. Cheney Syndrom (HCS) was diagnosed clinically and radiologically and a treatment with bisphosphonates was introduced.

Obesity, Overweight, and Their Life Course Trajectories in Veterans and Non‐Veterans

Veterans comprise a large and growing segment of the US population. Results from national telephone surveys suggest higher prevalence of overweight among Veterans compared with demographically similar non-Veterans, based on self-reported height and weight. Using 1999-2008 data from the National Health and Nutrition Examination Survey (NHANES), we compared 3,768 Veterans and 21,974 non-Veterans on: (i) several measures of adiposity based on direct anthropometry; (ii) life-course of self-reported BMI; and (iii) behaviors related to weight loss or maintenance. Whether Veterans were more likely than demographically similar non-Veterans to be obese or overweight depended on the adiposity measure employed. On BMI, Veterans were about equally likely to be obese (30+ kg/m(2)), but more likely to be overweight (25-29.9 kg/m(2)) by both self-report and by direct measurement (significantly so only by self-report). On waist-stature ratio, a roughly similar pattern was observed. On waist circumference, Veterans tended to have larger values than demographically similar non-Veterans, with more Veterans in the largest two categories. But on dual-photon X-ray absorptiometry, Veterans were less likely to have 35+% body fat than non-Veterans of similar age, gender, and race/ethnicity. Life-course trends in self-reported BMI suggested a possible burst of weight gain after military discharge. These results suggest that Veterans may, on average, have less excess body fat than non-Veterans--a pattern not revealed by standard anthropometric measures.

Negative association of acetate with visceral adipose tissue and insulin levels

BackgroundThe composition of gut flora has been proposed as a cause of obesity, a major risk factor for type 2 diabetes. The objective of this study was to assess whether serum short chain fatty acids, a major by-product of fermentation in gut flora, are associated with obesity and/or diabetes-related traits (insulin sensitivity and secretion).MethodsThe association of serum short chain fatty acids levels with measures of obesity was assessed using body mass index, computerized tomography scan, and dual photon X-ray absorptiometry scan. Insulin sensitivity and insulin secretion were both determined from an oral glucose tolerance test and insulin sensitivity was also determined from a hyperinsulinemic euglycemic clamp.ResultsIn this population of young, obese women, acetate was negatively associated with visceral adipose tissue determined by computerized tomography scan and dual photon X-ray absorptiometry scan, but not body mass index. The level of the short chain fatty acids acetate, but not propionate or butyrate, was also negatively associated with fasting serum insulin and 2 hour insulin levels in the oral glucose tolerance test.ConclusionsIn this population, serum acetate was negatively associated with visceral adipose tissue and insulin levels. Future studies need to verify these findings and expand on these observations in larger cohorts of subjects.

Effect of Strength Training and the Practice of Alpine Skiing on Bone Mass Density, Growth, Body Composition, and the Strength and Power of the Legs of Adolescent Skiers

This work examines the influence of practicing strength training and Alpine skiing over 2 years on bone mineral density (BMD), growth, body composition, and the strength and power of the legs of adolescent skiers. The study subjects were 20 adolescent skiers (10 girls and 10 boys) and 19 sedentary adolescents (9 girls and 10 boys), all 13-16 years of age. The BMDs of the lumbar column (L2-L4) and hip (neck of the femur, trochanter, and Ward's triangle) were determined by dual x-ray photon absorptiometry at the beginning and end of the experimental period. The increase in height and the percentage fat and muscular masses of the subjects were also recorded, as was their ability to jump (countermovement jump [CMJ]), their leg strength and power (squat test), and their leg anaerobic power (continuous jump test [CMJ15″]). No significant differences were seen in the increase in height, body weight, or percentage fat mass between the skiers and sedentary subjects, although the boy skiers showed a significant increase in percentage muscular mass (p < 0.05) compared to the sedentary boys. The improvement in the values of the different CMJ variables was significantly greater among the boy skiers than among the sedentary boys (p < 0.001-0.01). The same was true for the girls (p < 0.001), except for CMJ15″. The skiers experienced a significantly greater increase in L2-L4 BMD than the sedentary subjects (boys p < 0.05; girls p < 0.01). These results suggest that Alpine skiing combined with rational strength training involves no special risk for the physical development of young people, has a positive effect on the power and the percentage of muscle mass in the legs, and helps to have a higher bone density in the lumbar spine (L2-L4).

Bone mineral density in patients with thyroid cancer on suppressive therapy after total thyroidectomy.

e19739 Background: The standard therapy of thyroid carcinomas (TC) consists of total or nearly total thyroidectomy. Then the whole-life substitution therapy by oral thyroxine (T4) is given. Another goal of this therapy is to suppress serum thyroid stimulating hormone (TSH) to prevent the growth factor-like effect of TSH on TC cells. The recommendation is to administer supraphysiologic amounts of oral T4. This leads to hyperthyroidism, which is subclinical. Thyroid hormones are also involved in regulation of bone metabolism and longstanding subclinical hyperthyroidism may result in increased bone turnover and decreased bone mineral density (BMD). The aim of the study was to assign the damage of bone metabolism in TC patients. Methods: Bone mineral density (BMD) was measured by dual energy photon x-ray absorptiometry in the lumbar spine and hips. BMD was classified using T score in postmenopausal women and more than 50 years old men. We classified Z score in premenopausal women and younger than 50 years men. C-terminal cross-linked telopeptides of type I collagen (CTX) were measured using ELISA. Additionally serum TSH and fT4 (free T4) were measured. Relationships between baseline characteristics (age, menopausal status in women, TSH levels and duration of suppressive therapy) and BMD were assessed using univariate and multivariate analysis tools. Results: We included 165 TC patients in the study. There were 13 men and 152 women, the mean duration of thyroid suppressive therapy was 7. 2 years (0 – 24 years). The patients exhibit osteporosis in 31%, whereas 30% had normal BMD. The incidence of osteoporosis appeared to increase with age but did not correlate with duration of thyroid suppressive therapy. TSH levels slightly correlated with decrease in BMD. Conclusions: The long term survivors from TC after total thyroidectomy on thyroid suppressive therapy have higher risk of osteoporosis and therefore we recommend BMD testing and appropriate measures according to results.

Mechanical Function of Vertebral Body Osteophytes, as Revealed by Experiments on Cadaveric Spines

Mechanical testing of cadaveric spines. To determine whether vertebral body osteophytes act primarily to reduce compressive stress on the intervertebral discs, or to stabilize the spine in bending. The mechanical significance of vertebral osteophytes is unclear. Thoracolumbar spines were obtained from cadavers, aged 51 to 92 years, with vertebral body osteophytes, mostly anterolateral. Twenty motion segments, from T5-T6 to L3-L4, were loaded in compression to 1.5 kN, and then in flexion, extension, and lateral bending to 10 to 25 Nm (depending on specimen size) with a compressive preload. Vertebral movements were tracked using an optical 2-dimensional MacReflex system. Tests were performed in random order, and were repeated after excision of all osteophytes. Osteophyte function was inferred from (a) changes in the force or moment resisted and (b) changes in tangent stiffness, measured at maximum displacement or rotation angle. Volumetric bone mineral density (BMD) was measured using dual photon x-ray absorptiometry and water immersion. Results were analyzed using repeated measures analysis of variance. Resistance to compression was reduced by an average of 17% after osteophyte removal (P < 0.05), and resistance to bending moment in flexion, extension, and left and right lateral bending was reduced by 49%, 36%, 36%, and 35%, respectively (all P < 0.01). Changes in tangent stiffness were similar. Osteophyte removal increased the neutral zone in bending (P < 0.05) and, on average, reduced motion segment BMD by 7% to 9%. Results were insensitive to applied loads and moments, but several changes were proportional to osteophyte size. Vertebral body osteophytes resist bending movements more than compression. Because they reverse the instability in bending that can stimulate their formation, these osteophytes seem to be adaptive rather than degenerative. Results suggest that osteophytes could cause clinical BMD measurements to underestimate vertebral compressive strength.

Dual-Energy X-Ray Absorptiometry Analysis for the Determination of Moisture Content in Biomass

The aim of the present study was to describe and validate a novel method able to fast, accurately and with a high precision determine the moisture content of biological materials ranging 10% to 70%. A calibrated Dual X-ray photon absorptiometry technique is validated against moisture content in wood chips. Conventional criteria such as the Pearson correlation coefficient, the root mean square errors of calibration and coefficient of variation were used for the evaluation of the method. The method is independent of the thickness and density of the object but dependent of the effective atomic number of the material. The results shows that this photon absorptiometric method gives accurate (<2%) and precise (<1%) results for moisture content determination in wood chips.

Skeletal Muscle Mass in Acromegaly Assessed by Magnetic Resonance Imaging and Dual-Photon X-Ray Absorptiometry

GH and IGF-I are nitrogen retaining and anabolic, but the impact of long-term exposure to supraphysiological GH and IGF-I, either from endogenous overproduction in acromegaly or exogenous sources, on skeletal muscle (SM) mass is not clear. The objectives of the study were to assess SM mass by whole-body magnetic resonance imaging (MRI) in acromegaly and test the hypothesis that dual-energy x-ray absorptiometry (DXA) lean tissue mass-derived estimates of SM accurately estimate true SM mass. The design was a cross-sectional study in 27 acromegaly patients compared with predicted models developed in 315 nonacromegaly subjects and to matched controls. Mass of SM from whole-body MRI and lean tissue from DXA were measured. SM mass did not differ from predicted or control values in active acromegaly: 31.75 +/- 8.6 kg (acromegaly) vs. 33.06 +/- 8.9 kg (predicted); SM was 95.6 +/- 12.8% of predicted (range 66.7-122%) (P = 0.088). Lean tissue mass (DXA) was higher in acromegaly than controls: 65.91 +/- 15.2 vs. 58.73 +/- 13.5 kg (P < 0.0001). The difference between lean tissue mass (DXA) and SM in acromegaly patients was higher than that in controls (P < 0.0001) consistent with an enlarged non-SM lean compartment in acromegaly. SM mass predicted by DXA correlated highly with SM mass by MRI (r = 0.97, P < 0.0001). SM (MRI) to SM (DXA predicted) ratio was 1.018 (range 0.896-1.159), indicating high agreement of these measures of SM. SM mass in active acromegaly patients did not differ from predicted values. SM mass estimated from DXA agreed highly with SM by MRI, supporting the validity of the DXA model in assessing SM in acromegaly and other disorders of GH/IGF-I secretion.