Biomedical subjects

N J Crabtree

Publications and source records attributed to N J Crabtree.

12 recordsLinked to original sources

PubMed2007

Body fat estimation using bioelectrical impedance.

BACKGROUND/AIMS: Although childhood obesity is a major problem, routine assessment methods do not reflect fat mass. Body mass index, which is most commonly used, gives an indication of weight for height and not a degree of adiposity. METHODS: Bioelectrical impedance and dual-energy X-ray absorptiometry (DEXA) were used in a group of obese children to assess body fat. RESULTS: Comparison between DEXA and commercial bioelectrical impedance scales in 46 children showed a highly significant correlation (R = 0.944, p < 0.001) in fat mass. Fat mass measured using bioelectrical impedance was 2.4 kg lower compared to measurement using DEXA. CONCLUSION: These bioelectrical scales may prove useful in the management of childhood obesity as they are able to provide important clinical information regarding fat mass and adiposity.

Absorptiometry, Photon↗

PubMed2006

Geographic and other determinants of BMD change in European men and women at the hip and spine. a population-based study from the Network in Europe for Male Osteoporosis (NEMO).

INTRODUCTION: While the determinants of BMD change have been studied in women, there have been few longitudinal studies in men. As part of the Network in Europe for Male Osteoporosis (NEMO) study, data were analysed from 1337 men and 1722 women aged 50-86y (mean=67 years) from 13 centres across Europe to assess determinants of BMD change and between-gender contrasts. METHODS: BMD was measured at the femoral neck, trochanter and/or L2-L4 spine on 2 occasions 0.8-8 years apart (mean=3.5 years) using DXA densitometers manufactured by Hologic (n=6), Lunar (n=5) and Norland (n=2). Each was cross-calibrated using the European Spine Phantom and annual rates of BMD change (g/cm(2)/year) were calculated from the standardised paired BMD values. The EPOS risk factor questionnaire was administered at baseline. RESULTS: In multivariate linear regression models, there were large between centre differences in the mean rates of BMD change in all 3 sites for both genders (P<0.0001) with the standard deviation of the between centre heterogeneity in the adjusted means being 0.005 g/cm(2)/year at the femoral neck. The overall adjusted mean annual rates of BMD change in g/cm(2)/year (95% CI) pooled across centres by random effects meta-analysis in men were: femoral neck -0.005 (-0.009, -0.001); trochanter -0.003 (-0.006, -0.001); and spine 0.000 (-0.004, 0.004). In women the respective estimates were: -0.007 (-0.009, -0.005); -0.004 (-0.006, -0.003); and -0.005 (-0.008, -0.001). The I(2) statistic for heterogeneity was between 81% and 94%, indicating strong evidence of between centre heterogeneity. Higher baseline BMD value was associated with subsequent greater decline in BMD (P<0.001). Preserved BMD was associated with higher baseline body weight in all 3 sites in men (P<0.012) but not in women. Weight gain preserved BMD (P<0.039) in all 3 sites for both genders, except the male spine. Increasing age was associated with faster BMD decline at the trochanter in both genders (P<0.026) and with a slower rate of decline at the female spine (P=0.002). Effects of lifestyle, physical activity, medications, and reproductive factors were not consistent across sites or between genders. CONCLUSION: These results show major geographic variations in rates of BMD change in men and women over 50 years of age across diverse European populations and demonstrate that body weight and weight gain are key determinants of BMD change in men.

Absorptiometry, Photon↗

PubMed2005

Bone density at the os calcis: reference values, reproducibility, and effects of fracture history and physical activity.

AIMS: To establish reference values for bone mineral density (BMD) measured at the os calcis (OC) in healthy UK Caucasian children. Secondary objectives were to assess the reproducibility of the measurement and the effects of fracture history and habitual physical activity. METHODS: A total of 403 children aged 5-18 were studied. Main outcome measures were: BMDoc measured by peripheral DXA, total BMD measured by whole body axial scanner, age, anthropometry, pubertal status, self-reported fracture history, and physical activity (PA) expressed as a three point score. RESULTS: Complete data were available on 171 girls and 123 boys free of a history of fracture. BMDoc was related positively to age, body size, and total BMD, and could be predicted using a proportional model based on height alone (R2: 65% girls, 77% boys). Mean BMDoc appears to plateau in girls at 15 years and attain a value that concurs with the mean peak value in adult women. The 95% limits of agreement in repeated measures were -0.029 to 0.029 g/cm2 (n = 53). Compared with sedentary children, those doing regular sports or PA for more than five hours a week had an increased BMDoc (by about 0.03 g/cm2 or about 7% of the overall mean). A history of fracture (n = 81) was associated with a reduced BMDoc in boys but not in girls, though our study may have been underpowered for a subgroup analysis. CONCLUSIONS: BMDoc can be measured easily and quickly in children older than 5 years and provides an objective measure of areal bone density for clinical and research studies using a reference range derived from its relation to height.

Absorptiometry, Photon↗

PubMed2004

From bone biology to bone analysis.

Bone development is one of the key processes characterizing childhood and adolescence. Understanding this process is not only important for physicians treating pediatric bone disorders, but also for clinicians and researchers dealing with postmenopausal and senile osteoporosis. Bone densitometry has great potential to enhance our understanding of bone development. The usefulness of densitometry in children and adolescents would be increased if the physiological mechanisms and structural features of bone were given more consideration in the design and interpretation of densitometric studies. This review gives an overview on the most relevant techniques of quantitative noninvasive bone analysis. Furthermore it describes the relationship between bone biology, selected surrogates describing the biological processes and the possibilities of measuring these surrogates specifically and precisely by the different devices. The overall recommendation for researchers in this field is to describe firstly the biological process to be analyzed (bone growth in length, remodeling or modeling, or all together), secondly the bone parameter which describes this process, and thirdly the reason for selecting a special device.

Absorptiometry, Photon↗

PubMed2004

Does hip strength analysis explain the lower incidence of hip fracture in the People's Republic of China?

To explore whether there are ethnic differences in calculated hip strength that might explain the low incidence of hip fracture in China, we used Lunar DPX 'beta' version of hip strength analysis (HAS) and hip axis length (HAL) programs to compare hip geometry, calculated strength and densitometric values from Chinese subjects in Shenyang to those of Caucasian subjects in Oslo and Leuven participating in the European Prospective Osteoporosis Study (EPOS). Subjects were 210 Chinese and 403 Caucasian men and women aged 53-77 years. Parameters investigated included bone mineral density (BMD), bone mineral content (BMC), bone area (BA), cross-sectional moment of inertia (CSMI) and section modulus (both indicating strength and rigidity of the femoral neck), HAL, neck length (NL), neck diameter, tensile stress (Tstress) and compressive stress (Cstress) (indicating the stress in the femoral neck at its weakest cross section arising from walking or a standard fall, respectively), safety factor (SF, indicating the resistance to fracture for forces generated during walking) and fall index (FI, indicating the resistance to fracture from force generated during a fall in the greater trochanter). The Chinese men and women were significantly shorter and lighter than their Caucasian counterparts (P<0.01) and had significantly lower BMD, BMC and BA of the femoral neck (P<0.01). After adjusting for BA, weight and height, there was no significant ethnic difference in either gender in BMC. CSMI and section modulus were significantly lower, and HAL, NL and neck diameter were significantly shorter in the Chinese men and women (P<0.01). These differences all remained after adjusting for weight and height. There were no significant differences in Tstress, Cstress, SF and FI between ethnic groups in either gender. Most of the parameters of calculated hip strength in the Chinese subjects were similar to or poorer than those in the Caucasian subjects. There was no evidence to indicate that Shenyang Chinese have superior BMD or BMC or better calculated hip strength. The short HAL and NL of the population, however, could be an independent factor contributing to the low incidence of hip fracture.

Aged↗

PubMed2004

The relationship between lean body mass and bone mineral content in paediatric health and disease.

INTRODUCTION: The correct interpretation of DXA data is critical to the diagnosis and management of children with suspected bone disease. This study examines the various influences on bone mineral content (BMC), as measured by dual-energy X-ray absorptiometry (DXA). MATERIALS AND METHODS: Six hundred and forty-six healthy school children and forty-three children with chronic diseases, aged 5-18 years, had their lumbar spine and whole body measured using a Lunar DPX-L DXA scanner. RESULTS: Stepwise linear regression identified lean body mass (LBM) as the strongest single predictor of BMC in the lumbar spine and the total body. A significant gender difference was observed in the relationship between BMC and LBM with girls having significantly more bone per unit LBM from 9 years of age in the spine and 13 years of age in the total body. To investigate the relationship between LBM and BMC in children with chronic disease, a two-stage algorithm based upon calculation of Z scores from the normative data was applied. Stage 1 assessed LBM for height and stage 2 assessed BMC for LBM. Ten children with spinal muscular atrophy had a mean LBM for height Z score of -1.8(1.4) but a mean BMC for LBM Z score of 1.2(1.3) indicating their primary abnormality was reduced muscle mass (sarcopenia) with no evidence of osteopenia. In contrast, 21 children with osteogenesis imperfecta had a mean LBM for height Z score of 0.4(1.7) but a mean BMC for LBM Z score of -2.5(1.8) indicating normal LBM for size but significantly reduced BMC for LBM (i.e. osteopenia) confirming a primary bone abnormality. A third group consisting of 12 children with low trauma fractures demonstrated little evidence of sarcopenia [mean LBM for height Z score -1.1(2.1)] but significant osteopenia [mean BMC for LBM Z score -1.9(1.5)]. CONCLUSION: The results from this study demonstrate how the relationship between height and lean body mass, and lean body mass and bone mineral content can be a useful method of diagnosing osteoporosis in children and how the relationships can be used to identify if the primary abnormality is in muscle or bone.

Adolescent↗

PubMed2004

Bone mineral density and markers of bone turnover in patients with glycogen storage disease types I, III and IX.

Patients with glycogen storage disease (GSD) types I, III and IX show reduced bone mineral content, but there is scarce data on new serum and urine markers of bone turnover or their relationship to bone densitometry. Six GSD I, four GSD III and four GSD IX patients underwent bone mineral density (BMD) measurement by dual-energy X-ray absorptiometry. Free pyridinoline (fPYD):creatinine and free deoxypyridinoline (fDPD):creatinine ratios were analysed on random urines. Procollagen type I C-terminal propeptide, procollagen type I N-terminal propeptide (PINP), carboxyterminal telopeptide of type I collagen and bone-specific alkaline phosphatase were analysed in serum. Some GSD I and GSD III patients had low or very low BMD. There was no difference in total body BMD z-score between the GSD types after adjusting for height (p=0.110). Bone marker analysis showed no consistent pattern. Urine fPYD:creatinine ratio was raised in four GSD I and two GSD III patients, while serum PINP was inappropriately low in some of these patients. There was no clear correlation between any markers of bone destruction and total body z-score, but the patient with the lowest total body z-score showed the highest concentrations of both urinary fPYD:creatinine and fDPD:creatinine ratios. We conclude that some GSD I and GSD III patients have very low bone mineral density. There is no correlation between mineral density and bone markers in GSD patients. The inappropriately low concentration of PINP in association with the raised urinary fPYD:creatinine and fDPD:creatinine ratios seen in two GSD I patients reflect uncoupling of bone turnover. All these findings taken together suggest that some GSD I and GSD III patients may be at an increased risk of osteoporosis.

Absorptiometry, Photon↗

PubMed2003

Bone density and body composition in children with growth hormone insensitivity syndrome receiving recombinant IGF-I.

OBJECTIVE: There are few reports of the metabolic action of insulin-like growth factor 1 (IGF-I) in vivo. Growth hormone insensitivity syndrome is a good model to examine the effects of IGF-I deficiency. This study was designed to assess body composition and bone density in children with growth hormone insensitivity syndrome before and after receiving treatment with recombinant IGF-I. DESIGN: A prospective longitudinal study. PATIENTS: Four prepubertal boys age 6.1-9.8 years with short stature due to growth hormone insensitivity syndrome. MEASUREMENTS: Assessment of body fat by skinfold thickness measurements and dual energy X-ray absorptiometry (DXA) was made during the first 6 months of recombinant IGF-I treatment. Assessment of lumbar spine bone density by DXA was performed prior to IGF-I treatment and during the subsequent five years. RESULTS: Each child showed a significant reduction in fat mass (0.26-1.22 kg) after 6 weeks of IGF-I treatment. Bone density prior to treatment was reduced in comparison to age-matched controls but calculated volumetric bone density was within the normal range. Volumetric bone density progressively improved over the 5-year treatment period. CONCLUSIONS: Children with growth hormone insensitivity syndrome exhibit a metabolic response to IGF-I within 6 weeks analogous to that seen in GH-deficient children receiving GH. Bone density when corrected for body size is within normal limits and demonstrates a response to IGF-I, confirming the anabolic action on bone.

Absorptiometry, Photon↗

PubMed2002

Improving risk assessment: hip geometry, bone mineral distribution and bone strength in hip fracture cases and controls. The EPOS study. European Prospective Osteoporosis Study.

Hip geometry and bone mineral density (BMD) have previously been shown to relate independently to hip fracture risk. Our objective was to determine by how much hip geometric data improved the identification of hip fracture. Lunar pencil beam scans of the proximal femur were obtained. Geometric and densitometric values from 800 female controls aged 60 years or more (from population samples which were participants in the European Prospective Osteoporosis Study, EPOS) were compared with data from 68 female hip fracture patients aged over 60 years who were scanned within 4 weeks of a contralateral hip fracture. We used Lunar DPX 'beta' versions of hip strength analysis (HSA) and hip axis length (HAL) applied to DPX(L) data. Compressive stress (Cstress), calculated by the HSA software to occur as a result of a typical fall on the greater trochanter, HAL, body mass index (BMI: weight/(height)2) and age were considered alongside femoral neck BMD (FN-BMD, g/cm2) as potential predictors of fracture. Logistic regression was used to generate predictors of fracture initially from FN-BMD. Next age, Cstress (as the most discriminating HSA-derived parameter), HAL and BMI were added to the model as potentially independent predictors. It was not necessary to include both HAL and Cstress in the logistic models, so the entire data set was examined without excluding the subjects missing HAL measurements. Cstress combined with age and BMI provided significantly better prediction of fracture than FN-BMD used alone as is current practice, judged by comparing areas under receiver operating characteristic (ROC) curves (p<0.001, deLong's test). At a specificity of 80%, sensitivity in identification was improved from 66% to 81%. Identifying women at high risk of hip fracture is thus likely to be substantially enhanced by combining bone density with age, simple anthropometry and data on the structural geometry of the hip. HSA might prove to be a valuable enhancement of DXA densitometry in clinical practice and its use could justify a more proactive approach to identifying women at high risk of hip fracture in the community.

Absorptiometry, Photon↗

PubMed2002

Prevalence of osteoporotic bone mineral density at the hip in Britain differs substantially from the US over 50 years of age: implications for clinical densitometry.

The purpose of this study was to compare hip bone mineral density (BMD) recorded in seven population based cohorts in Britain with the third National Health and Nutrition Examination Survey (NHANES III) US population-based reference data, in order to assess geographic variation in the prevalence of osteoporosis. Men and women aged 50-80+ years were randomly recruited from population and health registers. Dual X-ray absorptiometry (DXA) equipment was used to measure BMD at the hip, with the femoral neck and the trochanter regions studied. Prevalences of osteopenia and osteoporosis were estimated in accordance with World Health Organisation diagnostic criteria for women. Young normal data, used to establish cut-off criteria, was from NHANES III. Both male and female British subjects over 50-years-old were found to have significantly higher mean BMD at the femoral neck and trochanter than their US counterparts. Decline in BMD with age in British men appeared slower than in US men. Between British centres there were also statistically significant differences in BMD values in both sexes. British age-adjusted prevalences of osteopenia in women averaged 20% less than those of NHANES III, whereas the prevalence of osteoporosis was substantially lower in British subjects of both sexes (55% in women, 68% in men). Thus, applying the US NHANES III data as the referent, osteoporosis of the proximal femur in Britain appears to be less common than in the US, due primarily to differences in the lower tails of the BMD distributions. Providing that the relationship between fracture rates and BMD is the same in Britain and the US, it would still be appropriate to apply the reference data in fracture risk assessment in the UK.

Absorptiometry, Photon↗

PubMed2000

Ambulatory level and asymmetrical weight bearing after stroke affects bone loss in the upper and lower part of the femoral neck differently: bone adaptation after decreased mechanical loading.

The aim of this 1-year prospective study of acute stroke patients was to determine the effects of walking and asymmetrical weight bearing on the loss of bone mineral in the upper and lower femoral neck. Forty patients were followed. Eight remained unable to walk, whereas 32 relearned to walk independently within 7 months (12 shortly after the stroke, 15 by 2 months, 5 by 7 months). Bone mineral density (BMD) was measured in the proximal femur within the first week after stroke and 1 year later; regional BMD changes were computed for the lower and upper femoral neck. The lower part of the femoral neck is mainly influenced by compressive stresses of the hip, the upper part by tensile stresses during walking. When comparing mean BMD loss in groups of patients according to when they relearned to walk, a statistically significant trend in BMD loss was found in the lower femoral neck on both the paretic and nonparetic sides (p < 0.01 and p = 0.01, respectively), whereas, for the upper femoral neck, no significant trend was seen (p >/= 0.1). In addition, the body weight distribution during standing was assessed by use of a force-plate in 38 patients who could stand independently at the 7 month evaluation. The only significant correlation between changes in BMD and asymmetrical weight bearing was found in the lower femoral neck on the paretic side (r = 0.6, p < 0.001). In conclusion, this study shows that the reduction in BMD in the femoral neck occurs mainly in the lower part of the neck and on the paretic side. The BMD loss depended on when or if the patients relearned to walk, but also on the amount of body weight born on the paretic leg. Thus, measuring the lower part of the femoral neck gives a better estimate of the impact of gait and weight bearing than measuring the total femoral neck.

Absorptiometry, Photon↗

PubMed2000

Intravenous pamidronate in juvenile osteoporosis.

AIMS: To investigate the use of the aminobisphosphonate, disodium pamidronate, in children with vertebral osteoporosis. METHODS: Five children (aged 10-15 years) with vertebral osteoporosis who developed compression fractures in the thoracic and/or lumbar spine as a consequence of five different conditions, received treatment with intravenous disodium pamidronate in doses ranging from 0.5 to 12 mg/kg/y. RESULTS: Each child had rapid pain relief following the first treatment, followed by large increments in lumbar spine bone density over one year; the change in bone density standard deviation score ranged from 0.5 to 2.5 with percentage increments of 26% to 54%. CONCLUSION: Intravenous pamidronate appears to be a useful therapeutic option in childhood osteoporosis, but its use in children must still be regarded as experimental and therefore closely monitored.

Absorptiometry, Photon↗