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Biomedical subjects

Eckhard Schoenau

Publications and source records attributed to Eckhard Schoenau.

At least 19 recordsLinked to original sources
PubMed2006

The 'Functional Muscle-Bone Unit': probing the relevance of mechanical signals for bone development in children and adolescents.

The present text deals with the relationship of muscle force and mass to bone mass and geometry in the developing skeleton of children and adolescents. Recent results of the last ten years are discussed with reflection on Harold Frost's 'mechanostat hypothesis'. Bone mass and geometry follow the development of body size and muscle force in children and adolescents. Thereby, bone is adapted to the tissue strain due to biomechanical forces. This process is modified by hormonal signals (i.e., estrogens and androgens). Therefore, the quantified relationship of muscle force to bone stability is a reasonable approach to distinguish between primary and secondary bone diseases. Primary bone diseases are characterized by a disturbed adaptation of bone to biomechanical forces. In contrast, secondary bone diseases show a correct adaptation of bone to loaded forces in combination with a decline of muscle force. Therefore, the 'Functional Muscle-Bone Unit' was introduced into the diagnostics of pediatric bone diseases. The ratio of two parameters--referred to bone strength on the one and to biomechanical forces on the other side--is a reasonable diagnostic approach to distinguish between primary and secondary bone diseases.

Adolescent↗
PubMed2006

Bone mass increase in puberty: what makes it happen?

It is now thought that the critical property of bone is strength rather than weight, and that control of bone strength is mainly exercised through the effect of the mechanical loads brought to bear on bone. Muscle contraction places the greatest physiological load on bone, and so the strength of bone must be adapted to muscle strength (the functional muscle-bone unit). The Utah paradigm of skeletal physiology [J Hum Biol 1998;10:599-605] provides a model of bone development that describes how bone structure is regulated by local mechanical effects that can be adjusted by the effects of hormones. The DONALD (Dortmund Nutritional and Anthropometric Longitudinally Designed) study analysed the interaction between the muscle and bone systems in males and females before and during puberty. This study found that differences between the genders in bone adaptation during puberty are at least partly driven by the influence of oestrogen in females. Testosterone seems to have no direct relevant effect on bone during puberty, but may be implicated in the greater amount of muscle mass achieved in boys compared with girls.

Bone Density↗
PubMed2005

Mechanography--a new device for the assessment of muscle function in pediatrics.

The development of the musculoskeletal system in children and adolescents became an important topic in the field of pediatric research when the connections between muscle force and bone diseases were revealed. The present study focused on reference values of ground reaction forces, which derive from muscle forces of the lower limbs. Specifically, the study investigated the relationship between anthropometric characteristics and peak jump force (PJF), and peak jump power (PJP). The parameters were assessed by jumping mechanography using the Leonardo Jumping Platform. The entire study group was comprised of 135 school boys (ages 7-21 y) and 177 girls (ages 6-19 y), who were enrolled in a German primary school and a German high school. The analysis of the parameters revealed that forces deriving from the motor performance of jumping follow an exponential relationship to body size parameters. Therefore, with consideration of anthropometric characteristics, the assessment of ground reaction forces might provide a novel, inexpensive, and accurate approach for the assessment motor performance in children and adolescents.

Adolescent↗
PubMed2005

Outcome of muscle and bone development in congenital heart disease.

Muscles and bones of patients with congenital heart disease (CHD) are subject to various potentially deleterious influences during growth. The aim of the present study was to analyse the outcome of bone and muscle parameters in adolescents and young adults with a spectrum of CHD. Bone and muscle parameters of the forearm were examined at two standard sites, 4% and 65%, in 29 adolescents and young adults with CHD, aged 14-24 years, by quantitative computed tomography. For the entire study population, bone and muscle parameters did not deviate significantly from the reference values except for age- and gender-corrected body height (ASDS-height: -0.6+/-1.2, p=0.01). Both age- and gender- and height- and gender-corrected (HSDS) abnormal bone mass (BMC) was found at the distal radius in patients with Fontan repair (ASDS-BMC4%: -1.5+/-0.9, p=0.008; HSDS-BMC4%: -1.2+/-1.0, p=0.05) and in those in NYHA class III (ASDS-BMC4%: -1.3+/-0.4, p=0.001; HSDS-BMC4%: -1.4+/-0.5, p=0.004). There was minimal overlap between Fontan patients (n=6) and NYHA class III (5 Fontan patients were in NYHA class I or II). In conclusion, most patients with CHD show a normal muscle and bone development in proportion to their reduced body height. Further follow-up is required to determine whether patients in a worse clinical status (NYHA III) and those with single ventricle physiology are at increased risk of osteoporosis and fractures.

Adolescent↗
PubMed2005

A novel homozygous missense mutation in FGF23 causes Familial Tumoral Calcinosis associated with disseminated visceral calcification.

Hyperphosphatemic Familial Tumoral Calcinosis (HFTC; MIM211900) is a rare autosomal recessive disorder characterized by the progressive deposition of calcified masses in cutaneous and subcutaneous tissues, associated with elevated circulating levels of phosphate. The disease was initially found to result from mutations in GALNT3 encoding a glycosyltransferase. However, more recently, the S71G missense mutation in FGF23, encoding a potent phosphaturic protein, was identified in two families. In the present report, we describe a second mutation in FGF23 underlying a severe case displaying calcifications of cutaneous and numerous extracutaneous tissues. The mutation (M96T) was found to affect a highly conserved methionine residue at position 96 of the protein. These observations illustrate the extent of genetic and phenotypic heterogeneity in HFTC.

Amino Acid Substitution↗
PubMed2005

High and low density in the same bone: a study on children and adolescents with mild osteogenesis imperfecta.

Children and adolescents with osteogenesis imperfecta (OI) generally have low bone mineral density (BMD) at the lumbar spine and hip. However, the effects of the disease on diaphyseal bone have not been well characterized, even though long-bone fractures are common in such patients. In this study on 42 fully mobile children and adolescents with mild OI (age 6-19 years; 17 girls), lumbar spine, radius (metaphysis and diaphysis) and second metacarpal (diaphysis) were analyzed using dual-energy X-ray absorptiometry, peripheral quantitative computed tomography and radiogrammetry, respectively. Bone mineral content at the lumbar spine, radial metaphysis and radial diaphysis was between 25% and 31% lower than in age-matched healthy children and adolescents. At the lumbar spine and radial metaphysis, bone size (as estimated from projection area and cross-sectional area, respectively) was normal or only slightly below the results expected for healthy individuals, whereas bone size was very small at the diaphyseal sites of the radius and the second metacarpal. Total volumetric BMD is defined as the ratio between bone mineral content and bone volume. Therefore, these differences in bone size between skeletal locations led to markedly discrepant results for total volumetric BMD. Total volumetric BMD was low at the lumbar spine (23% below result expected for healthy subjects of the same age) and the radial metaphysis (-15%) but elevated at the radial diaphysis (+25%; all differences to controls significant at P < 0.001). Despite high volumetric BMD, estimated bending strength at the radial diaphysis was very low. These results demonstrate that volumetric BMD can be abnormally high and low within the same bone in the same individual and highlight the fact that volumetric BMD at diaphyseal sites does not provide a good estimate of bone strength when bone size is abnormal.

Absorptiometry, Photon↗
PubMed2005

The "functional muscle-bone unit": a two-step diagnostic algorithm in pediatric bone disease.

Bone densitometric data often are difficult to interpret in children and adolescents because of large inter- and intraindividual variations in bone size. Here we propose a functional approach to bone densitometry that addresses two questions. Is bone strength normally adapted to the largest physiological loads, i.e., muscle force? Is muscle force adequate for body size? Previously published reference data were used to evaluate results from children with preterminal chronic renal failure (n=11) and renal transplant recipients (n=15). In both groups mean height, muscle cross sectional area (MCSA), and bone mineral content (BMC) were low for age, but muscle MCSA was normal for height. In the renal transplant recipients the BMC/muscle MCSA ratio was decreased (P <0.05), suggesting that bone cortical strength was not adapted adequately to muscle force. In contrast, chronic renal failure patients had a normal cortical BMC/muscle MCSA ratio, suggesting that their musculoskeletal system was adapted normally to their (decreased) body size.

Adolescent↗
PubMed2005

Speed of sound: relation to geometric characteristics of bone in children, adolescents, and adults.

OBJECTIVES: To investigate the relation between volumetric bone mineral density (vBMD) and speed of sound (SOS). STUDY DESIGN: Total and trabecular vBMD were measured by peripheral quantitative computed tomography at the forearm in a population of 216 individuals of a pediatric outpatient clinic. Moreover, SOS was measured by a quantitative ultrasound device (QUS) at the thumb, patella, and os calcis. RESULTS: Linear regression analysis revealed that the prediction of SOS by vBMD is relatively weak (R2 < 0.1). Moreover, body height and measures of bone size have a stronger influence on SOS than vBMD. The influence of bone size on SOS also depends on the location of measurement (highest prediction of SOS by body height at patella with R2 = 0.56). Anthropometric characteristics have a stronger influence on SOS than measures of bone mineral density at the thumb and patella in comparison to os calcis (body height predicts SOS at os calcis, with R2 = 0.03). Conclusions QUS is not a suitable method to assess bone density. If QUS is applied for the assessment of bone development and of bone fracture risk, the measurement should be performed with consideration of anthropometric measurements.

Adolescent↗
PubMed2005

Long-term protein intake and dietary potential renal acid load are associated with bone modeling and remodeling at the proximal radius in healthy children.

BACKGROUND: Protein and alkalizing minerals are increasingly described as playing a major role in influencing bone status, not only in the elderly but also in children and adolescents. OBJECTIVE: We examined whether the long-term dietary protein intake and diet net acid load are associated with bone status in children. DESIGN: In a prospective study design in 229 healthy children and adolescents aged 6-18 y, long-term dietary intakes were calculated from 3-d weighed dietary records that were collected yearly over the 4-y period before a one-time bone analysis. Dietary acid load was characterized as potential renal acid load (PRAL) by using an algorithm including dietary protein, phosphorus, magnesium, and potassium. Proximal forearm bone variables were measured by peripheral quantitative computed tomography. RESULTS: After adjustment for age, sex, and energy intake and control for forearm muscularity, BMI, growth velocity, and pubertal development, we observed that long-term dietary protein intake was significantly positively associated with periosteal circumference (P < 0.01), which reflected bone modeling, and with cortical area (P < 0.001), bone mineral content (P < 0.01), and polar strength strain index (P < 0.0001), which reflected a combination of modeling and remodeling. Children with a higher dietary PRAL had significantly less cortical area (P < 0.05) and bone mineral content (P < 0.01). Long-term calcium intake had no significant effect on any bone variable. CONCLUSIONS: Long-term dietary protein intake appears to act anabolically on diaphyseal bone strength during growth, and this may be negated, at least partly, if dietary PRAL is high, ie, if the intake of alkalizing minerals is low.

Acid-Base Equilibrium↗
PubMed2004

L-arginine, the natural precursor of NO, is not effective for preventing bone loss in postmenopausal women.

UNLABELLED: NO is an important regulator of bone turnover. L-Arginine, the natural precursor of NO, can enhance NO production. However, no effect of L-arginine hydrochloride supplementation was found on bone metabolism or on BMD, bone mass, or bone structure of healthy postmenopausal women. INTRODUCTION: Recent studies indicate that NO exerts an anabolic effect on bone cell activity. The NO level of the human body can be elevated by administering pharmacological NO donors. Animal studies and the first human trial showed that NO donor administration had a positive effect on bone formation and a negative effect on bone resorption. L-arginine, the natural precursor of NO, can enhance NO production. This study was conducted to examine the effect of an oral L-arginine supplement on bone metabolism of healthy postmenopausal women. MATERIALS AND METHODS: The participants in this study were 30 healthy, age-matched postmenopausal women, divided into two groups. For 6 months, one group (54.5 +/- 4.1 years; 66.3 +/- 10.5 kg) received a daily oral supplement with 18 g L-arginine hydrochloride (14.8 g free L-arginine). The other 15 volunteers (55.3 +/- 4.4 years; 64.2 +/- 9.1 kg) received 18 g dextrose as a placebo. To verify compliance, 24-h urinary excretion of nitrogen was analyzed for 2 consecutive days at baseline and after 2, 4, and 6 months. At baseline and after 2, 4, and 6 months of supplementation, blood was drawn for analysis of insulin-like growth factor-I (IGF-I) and biomarkers of bone metabolism. At baseline, after 6 months, and after 1 year, pQCT measurements were performed at trabecular and cortical sites of the radius and tibia. The two groups of subjects were compared by repeated measures ANOVA. RESULTS: As expected, in the group with L-arginine hydrochloride supplementation, nitrogen excretion rose, and in the placebo group, it remained constant. Only bone formation marker, procollagen type I propeptides (PICP), increased significantly (p < 0.05) after 6 months of L-arginine supplementation. The results from pQCT showed no significant changes at any site in either group. No significant change in IGF-I concentration, which might have been caused by the L-arginine hydrochloride supplementation, was evident. CONCLUSIONS: We conclude from these results that supplementation with L-arginine hydrochloride is not effective for improving bone mass in humans.

Administration, Oral↗
PubMed2004

Adrenal steroid hormones and metaphyseal bone in children.

BACKGROUND/OBJECTIVES: The responses of metaphyseal bone tissue to physiological variations of endogenous adrenal steroid hormones during childhood are unclear. Therefore, we studied potential hormonal influences in children before the appearance of pubic hair (onset of pubarche). METHODS: Excretions of major glucocorticoid metabolites (C21), cortisol, sum of adrenarchal dehydroepiandrosterone and its immediate 16-hydroxylated metabolites (DHEA&M), and 5-androstene-3beta,17beta-diol (hermaphrodiol) were analyzed in a cross-sectional study in 24-hour urine samples of 109 healthy boys and girls, aged 6-13 years, using steroid profiling by gas chromatography-mass spectrometry. Total and trabecular volumetric bone mineral densities, bone mineral content (BMC) and bone strength strain index were determined with peripheral quantitative computed tomography at the distal forearm. RESULTS: In multiple regression analyses significant associations with the metaphyseal radius were seen for grip force, age, or BMI depending on gender and bone variable analyzed. DHEA&M did not contribute to the explanation of the variance of any bone variable. However, hermaphrodiol positively explained a significant part of variation of bone mineral densities, and BMC (p < 0.01) in girls. Significantly negative associations with all bone variables were seen in boys for cortisol. CONCLUSIONS: The steroid hormones, cortisol and hermaphrodiol, in their physiological ranges, but not the adrenarche marker DHEA&M, appear to associate with metaphyseal bone in a sex-dependent manner during childhood.

Adolescent↗
PubMed2004

Analysis of the functional muscle-bone unit of the forearm in pediatric renal transplant recipients.

BACKGROUND: Renal transplantation in children and adolescents is associated with various skeletal complications. The incidence of spontaneous fractures appears to be increased, but the reasons for this are not entirely clear. Our objective was therefore to evaluate macroscopic bone architecture, mass, and strength by peripheral quantitative computed tomography (pQCT), a method that is not influenced by size-related artifacts. In addition, we investigated the muscle-bone relationship in these patients because under physiologic conditions bone strength continually adapts to increasing mechanical loads, that is, muscle force. METHODS: In 55 patients (41 males) aged 15.8 +/- 4.1 years, we evaluated in a cross-sectional study 4.9 +/- 3.6 years after renal grafting bone mass, density, geometry, and strength of the radius, as well as forearm muscle size and strength, using pQCT at the proximal and distal radius, radiography of the second metacarpal shaft and hand dynamometry. Data were compared to a large cohort (N= 350) of healthy children. RESULTS: Muscle mass and force were adequate for body size in pediatric renal transplant recipients. However, the radial bone was characterized by an inadequately thin cortex in relation to muscular force, as shown by a reduced height-adjusted cortical thickness both at the proximal (-0.83 +/- 1.12 SDS) and distal radius (-0.52 +/- 1.69 SDS), the metacarpal shaft (-0.54 +/- 1.35 SDS), and by a reduced relative cortical area (-0.90 +/- 1.13 SDS), while the mineralization of trabecular bone was unaltered. As a consequence of cortical thinning, the Strength-Strain Index that reflects the combined strength of trabecular and cortical bone was reduced in these patients. CONCLUSION: While bone mineral density of the forearm is not decreased in pediatric renal transplant recipients, bone strength in relation to muscular force is reduced. This alteration may contribute to the increased propensity for fractures in these patients.

Adolescent↗
PubMed2003

Effect of pamidronate treatment on vertebral deformity in children with primary osteoporosis. A pilot study using radiographic morphometry.

OBJECTIVE: Bisphosphonates are effectively used in treatment for primary osteoporosis in children. In the present study, we quantitatively evaluated the effect of pamidronate treatment on lumbar vertebrae in children with primary osteoporosis using radiographic morphometry. METHODS: Paired lateral radiographs of the lumbar spine were obtained before and after pamidronate treatment in 5 children with primary osteoporosis. To characterize vertebral deformities, specific morphometrical ratios were calculated for vertebral bodies L1-L4. RESULTS: Significant reshape of lumbar vertebrae was observed: the concavity index (middle-anterior ratio) decreased from 55 to 36% (p = 0.006), and the anterior-posterior ratio (used as a surrogate of wedge deformity) decreased from 25 to 11% (p = 0.001). CONCLUSIONS: Pamidronate treatment significantly influences the restoration of vertebral fractures in children with primary osteoporosis. The present study demonstrates that radiographic morphometry is a suitable tool for quantitative assessment of the vertebral deformities in childhood.

Adolescent↗
PubMed2003

Adrenarche and bone modeling and remodeling at the proximal radius: weak androgens make stronger cortical bone in healthy children.

UNLABELLED: Adrenarche, the physiological increase in adrenal androgen secretion, may contribute to better bone status. Proximal radial bone and 24-h urinary steroid hormones were analyzed cross-sectionally in 205 healthy children and adolescents. Positive adrenarchal effects on radial diaphyseal bone were observed. Obviously, adrenarche is one determinant of bone mineral status in children. INTRODUCTION: Increased bone mass has been reported in several conditions with supraphysiological adrenal androgen secretion during growth. However, no data are available for normal children. Therefore, our aim was to examine whether adrenal androgens within their physiological ranges may be involved in the strengthening of diaphyseal bone during growth. METHODS: Periosteal circumference (PC), cortical density, cortical area, bone mineral content, bone strength strain index (SSI), and forearm cross-sectional muscle area were determined with peripheral quantitative computed tomography (pQCT) at the proximal radial diaphysis in healthy children and adolescents. All subjects, aged 6-18 years, who collected a 24-h urine sample around the time of their pQCT analysis (100 boys, 105 girls), were included in the present study, and major urinary glucocorticoid (C21) and androgen (C19) metabolites were quantified using gas chromatography-mass spectrometry. RESULTS AND CONCLUSIONS: We found a significant influence of muscularity, but not of hormones, on periosteal modeling (PC) before the appearance of pubic hair (prepubarche). Similarly, no influence of total cortisol secretion (C21) was seen on the other bone variables. However, positive effects of C19 on cortical density (p < 0.01), cortical area (p < 0.001), bone mineral content (p < 0.001), and SSI (p < 0.001)--reflecting, at least in part, reduction in intracortical remodeling-were observed in prepubarchal children after muscularity or age had been adjusted for. This early adrenarchal contribution to proximal radial diaphyseal bone strength was further confirmed for all cortical variables (except PC) when, instead of C19 and C21, specific dehydroepiandrosterone metabolites were included as independent variables in the multiple regression model. During development of pubic hair (pubarche), muscularity and pubertal stage rather than adrenarchal hormones seemed to influence bone variables. Our study shows that especially the prepubarchal increase in adrenal androgen secretion plays an independent role in the accretion of proximal radial diaphyseal bone strength in healthy children.

Adolescent↗
PubMed2002

Anthropometric assessment of muscularity during growth: estimating fat-free mass with 2 skinfold-thickness measurements is superior to measuring midupper arm muscle area in healthy prepubertal children.

BACKGROUND: Anthropometric measurements are widely used to determine body composition, especially in children. OBJECTIVE: Our aim was to compare 2 of the simplest anthropometry-based equations available for determining nutritional status and muscularity in children and adolescents, examined in relation to other methodologically independent muscle variables. DESIGN: Midupper arm muscle area (UAMA) and fat-free mass (FFM) according to the equations of Slaughter et al (Hum Biol 1988;60:709-23), as well as separate biochemical, physical, and radiologic muscle variables, were determined cross-sectionally in 91 males and 91 females aged 6-18 y. The ability of UAMA and FFM to estimate muscularity, as measured by 24-h creatinine excretion, grip force, and peripheral quantitative computer tomography analysis of forearm muscle, was compared after dividing the study population into prepubertal and pubertal groups. RESULTS: Before puberty, correlations of all 3 muscularity variables were higher with FFM than with UAMA in both males and females. Multiple regression analyses confirmed FFM to be the predominant predictor, with partial R(2) >/= 0.68 (P < 0.001). However, in puberty, FFM did not consistently show this major influence. Only before puberty did FFM provide a significantly better fit (P < 0.05) than did UAMA for 2 of the 3 muscularity variables in each sex. CONCLUSIONS: The FFM estimate proved to be the better predictor for muscularity in healthy prepubertal children and is on a par with UAMA during puberty. FFM can be recommended as a simple anthropometric method to assess nutritional status before puberty, at least in healthy children.

Adolescent↗
PubMed2002

Fibrous dysplasia.

DEFINITION: Fibrous dysplasia (FD) of bone is a non-inheritable congenital disorder affecting both genders. It is characterized by expanding fibrous lesions, which contain bone-forming mesenchymal cells. PATHOPHYSIOLOGY: FD is caused by a somatic activating mutation of the alpha subunit of the Gs protein (Gsalpha). Bone mesenchymal cells produce a matrix of randomly distributed collagen fibres and islands of woven bone. Osteoclasts are responsible for the spread of the lesions. CLINICAL FINDINGS: The symptoms are bone pain, fracture, bone deformities and neurological deficits. Spontaneous regression of lesions does not occur. TREATMENT: Recently, an observational study of treatment with bisphosphonate has yielded promising results. There was a decreased intensity of bone pain, a decrease in biochemical markers of bone turnover and a radiographically apparent 'refilling of osteolytic sites' in about half of the patients. CONCLUSIONS: Very little is known about the effects of bisphosphonate treatment in children and adolescents with FD. Most patients report decreased bone pain after the first pamidronate infusion, which, in our view, justifies the use of this drug in severely affected patients. The many unanswered questions regarding this form of treatment can only be addressed when a large number of patients is treated in a standardized fashion, and data on the outcome are collected.

Adolescent↗