Angelika Stabrey

Results of a prospective pilot trial on mobility after whole body vibration in children and adolescents with osteogenesis imperfecta

Objective: To evaluate the effect of whole body vibration on the mobility of long-term immobilized children and adolescents with a severe form of osteogenesis imperfecta. Osteogenesis imperfecta is a hereditary primary bone disorder with a prevalence from 1 in 10000 to 1 in 20000 births. Most of these children are suffering from long-term immobilization after recurrent fractures. Due to the immobilization they are affected by loss of muscle (sarcopenia) and secondary loss of bone mass. Subjects: Whole body vibration was applied to eight children and adolescents (osteogenesis imperfecta type 3, N=5; osteogenesis imperfecta type 4, N=3) over a period of six months. Interventions and results: Whole body vibration was applied by a vibrating platform (Galileo Systems) constructed on a tilting-table. Success of treatment was assessed by measuring alterations of the tilting-angle and evaluating the mobility (Brief Assessment of Motor Function). All individuals were characterized by improved muscle force documented by an increased tilting-angle (median = 35 degrees) or by an increase in ground reaction force (median at start=30.0 [N/kg] (14.48—134.21); median after six months = 146.0 [N/kg] (42.46—245.25). Conclusions: Whole body vibration may be a promising approach to improve mobility in children and adolescents severely affected with osteogenesis imperfecta.

Local Body Composition Is Associated with Gender Differences of Bone Development at the Forearm in Puberty

Background/Aims: The present analyses intend to clarify if gender and puberty modify the relationship between bone development (modeling and remodeling) and fat mass at the forearm. Methods: Data were collected from participants (139 males, 157 females, age = 5–19 years) of the Dortmund Nutritional and Anthropometric Longitudinally Designed study in a cross-sectional investigation. The main outcome measures were total and trabecular bone mineral density (BMDtot and BMDtrab), strength strain index (SSI) and parameters associated with modeling (cortical area, CA; periosteal circumference, CP) and remodeling (cortical bone mineral density, BMDcort, endosteal circumference, CE) were analyzed in their relationship to cross-sectional fat (FA) and muscle area (MA) at the forearm. Results: BMDtot was correlated with FA in pubertal males (r = –0.25). BMDtrab was contrarily predicted by FA in pubertal males and females (r = –0.28 vs. 0.31). FA was correlated with BMDcort (r = –0.32) and CE (r = 0.26) in pubertal females. MA was positively correlated with CA, CP and SSI. Conclusions: Modeling and bone strength were primarily predicted by MA. Markers of remodeling were positively correlated with FA in pubertal females, but not in prepubertal individuals and pubertal males. Therefore, gender and puberty modify the relationship between FA and bone development.

Cross-Sectional Fat Area at the Forearm in Children and Adolescents

Background: Cross-sectional fat area (FA) and muscle area have been recently used to describe local body composition at the forearm in children and adolescents. The present analysis intends to characterize FA in a normal collective. Methods: FA was measured by peripheral quantitative computed tomography in a study collective (DONALD study) of 296 children and adolescents. FA was analyzed in relation to fat mass (FM) measured by 4 skinfold thicknesses. Results: FA was significantly correlated with FM (r = 0.8). FA was positively associated with height in prepubertal individuals and pubertal females, but negatively associated with height in pubertal males. Median and range of FA are displayed for different height ranges and pubertal stages in males and females to enable analyses of FA in subgroups. Conclusion: Because of the positive dependence of FA on height in prepubertal individuals and pubertal females, reference values of FA may be based on height. But reference values in pubertal males or in a mixed pubertal population should be rather based on pubertal stages than on height.

Do Bone Mineral Density, Bone Geometry and the Functional Muscle-Bone Unit Explain Bone Fractures in Healthy Children and Adolescents?

Background/Aims: Because the increasing fracture incidence has not been understood, the present study compares variables of the muscle-bone interaction to examine the hypothesis that an impaired adaptation of bone strength to muscle forces explains this phenomenon. Methods: The forearm of 220 individuals (mean age 11.1 ± 3.2 years; range 5.5–17.4 years) was analyzed by peripheral quantitative computed tomography. Bone mineral content (BMC), bone mineral density, periosteal circumference, cortical area, strength strain index (SSI) and muscle area (MA) were measured at the distal and proximal radius of the non-dominant forearm. Maximum isometric grip force was measured by a dynamometer. The fracture history was evaluated by a questionnaire after a period of 5 ± 1.7 years. Results: During the observational period at least one fracture appeared in 78 children and adolescents (35.5%). Individuals with and without fractures were not different in age, height, weight, and body mass index. Variables of bone mineral density, bone geometry and muscle force were not different between both groups. BMC, MA and SSI were dependent on age and sex. Conclusion: Fracture risk in healthy children and adolescents is not sufficiently explained by volumetric bone mineral density, the skeletal phenotype and indices of the functional muscle-bone unit.

High and Low Birth Weight and its Implication for Growth and Bone Development in Childhood and Adolescence

AIM To investigate the relationship of birth weight (BW) to anthropometric measures, local body composition and bone development. POPULATION AND METHODS 284 individuals (age 5-19 yr, 145 females) were recruited from the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study. Parameters of bone development (cortical bone mineral density [BMDcort], endosteal circumference [CE]) and of local body composition (cross-sectional fat area [FA]) were analyzed by pQCT at the forearm. Parameters were transformed into SD scores to adjust for age or height. RESULTS BW predicted weight-SDS (R = 0.221), height-SDS (R = 0.260) and FA-SDS (R = 0.150). Individuals with lower BW (< 10th percentile) had lower weight-SDS (p < 0.01), height-SDS (p < 0.01), BMDcort-SDS (p = 0.02) and higher CE-SDS (p = 0.05). BMDcort was correlated with BW (r = -0.319) and FA (r = -0.283) in pubertal females. CONCLUSION BW is characterized by direct and indirect effects on growth, body composition and bone development.

The ‘Functional Muscle-Cartilage Unit’: A Reasonable Approach to Describe a Putative Relationship between Muscle Force and Longitudinal Growth at the Forearm in Children and Adolescents?

Background: Several reports give evidence that the perichondral ossificiation of bone tubes (modeling) strongly depends on muscular forces in children and adolescents. The present analyses intend to investigate the hypothesis that muscular forces also partly determine enchondral ossification and, therefore, longitudinal growth of bone tubes. Subjects and Methods: Analyses were based on a single cross-sectional investigation with peripheral quantitative computed tomography in 296 individuals (age 5–19 years) participating in the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study. Results: Forearm length (FL) was correlated with body height in gender-related subgroups of prepubertal and pubertal individuals (rs between 0.76 and 0.86). Cross-sectional muscle area (MA) increased faster than FL and faster than cross-sectional bone area (BA) close to the distal growth plate in puberty. Close to the growth plate, longitudinal growth was faster than perichondral ossification in females. The ratio MA/BA (surrogate of pressure on the distal growth plate) was correlated with FL in prepubertal boys (r = –0.249, p = 0.043) and pubertal individuals (r = 0.153, p = 0.051). Conclusions: Results support the hypothesis that longitudinal growth precedes modeling at the distal forearm. Confounding variables such as puberty may modify the relationship between muscle forces and longitudinal growth at the forearm in boys.