Oliver Fricke

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.

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.

DBS in the basolateral amygdala improves symptoms of autism and related self-injurious behavior: a case report and hypothesis on the pathogenesis of the disorder

We treated a 13-year-old boy for life-threatening self-injurious behavior (SIB) and severe Kanners autism with deep brain stimulation (DBS) in the amygdaloid complex as well as in the supra-amygdaloid projection system. Two DBS-electrodes were placed in both structures of each hemisphere. The stimulation contacts targeted the paralaminar, the basolateral (BL), the central amygdala as well as the supra-amygdaloid projection system. DBS was applied to each of these structures, but only stimulation of the BL part proved effective in improving SIB and core symptoms of the autism spectrum in the emotional, social, and even cognitive domains over a follow up of now 24 months. These results, which have been gained for the first time in a patient, support hypotheses, according to which the amygdala may be pivotal in the pathogeneses of autism and point to the special relevance of the BL part.

The Use of Bone Age in Clinical Practice – Part 2

If height-limiting treatment is being considered for a child with tall stature, skeletal maturity is invaluable in the selection of appropriate patients for treatment, determining appropriate age of treatment commencement, monitoring progress of treatment, and determining the expected treatment effect on adult height. In precocious puberty, bone maturation can be usefully assessed at initial diagnosis and start of treatment and at regular intervals thereafter during treatment monitoring. Together with height, bone maturation is an essential parameter for long-term treatment monitoring in congenital adrenal hyperplasia. Bone age (BA) determination in children with skeletal dysplasia is only feasible in a few disorders and estimations should be treated with caution. Radiographs of the left hand and wrist are, however, essential in the diagnosis of many skeletal disorders. Bone mineralization and measures of bone lengths, width, thickness and cortical thickness should always be evaluated in relation to a child’s height and BA, especially around puberty. The use of skeletal maturity, assessed on a radiograph alone to estimate chronological age for immigration authorities or criminal courts is not recommended.

The effect of L-arginine administration on muscle force and power in postmenopausal women.

Previously published data (J Bone Miner Res (2005); 20: 471) did not give evidence that the administration of the nitric oxide precursor l‐arginine increases bone formation and decreases bone resorption in postmenopausal women. Data of this trial were reanalysed for putative effects of l‐arginine on muscle mass and muscular function. Therefore, 11 females of the former study group (n = 15; age 54·5 ± 4·1 years; daily oral administration of 18 g l‐arginine hydrochloride (equivalent of 14·2 g l‐arginine) over 6 months) and 12 females of the control group (n = 15; age 55·3 ± 4·4 years; daily administration of 18 g dextrose over 6 months) were analysed for biomechanical parameters (MIGF, maximal isometric grip force; PJF, peak jump force; PJP, peak jump power) and for the cross‐sectional muscle area (MA) and fat area (FA) at forearm and leg (calf) measured by peripheral quantitative computed tomography. The study was performed in a double‐blind design. The assessment of muscular and biomechanical parameters was undertaken before and after 6 months of l‐arginine versus placebo administration. l‐arginine‐supplemented females had a significant increase of PJF/kg in comparison with the control group. PJP/kg, MIGF, MA and FA were not significantly influenced by the administration of l‐arginine. In conclusion, the administration of l‐arginine increased maximal force in mechanographic analyses and may prevent a decline of muscle force in postmenopausal women.

Analysis of Cancellous Bone Turnover by Multiple Slice Analysis at Distal Radius: A Study Using Peripheral Quantitative Computed Tomography

We compared the results of peripheral quantitative computed tomography (pQCT) measurements (XCT-900; Stratec) at the 4% site of the distal radius (section 1; slice thickness of 2 mm) and in two proximally adjacent sections (sections 2 and 3). The study population consisted of 138 ambulatory patients (age 16.4 +/- 5.6 yr; mean +/- SD; 71 female) who were referred to a pediatric densitometry unit. Total volumetric bone mineral density (BMD) increased, whereas the area of the radial cross-section decreased in a proximal direction. There was a decrease in bone mineral content between sections 1 and 3, which was more pronounced in subjects under age 16. Cancellous BMD significantly decreased from section 1 to 3 only under the age of 16. In 12 patients under age 17 who suffered from increased bone fragility, cancellous BMD decreased about 2.5 times more between sections 1 and 3 than in age-matched patients who received anticonvulsant therapy but had a normal neurologic and musculoskeletal status (-21.4% +/- 16.9 vs -8.1% +/- 6.3; p = 0.02). This suggests that in the bone fragility group, trabeculae were removed faster during longitudinal growth of the radius. In conclusion, multiple slice analysis may provide information on the dynamic turnover of metaphyseal trabeculae during growth.

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.

Interaction between Muscle and Bone

Bone densitometric data are often 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, that is muscle force? Is muscle force adequate for body size? The theoretical background for this approach is provided by the mechanostat theory, which proposes that bones adapt their strength to keep the strain caused by physiological loads close to a set point. Because the largest physiological loads are caused by muscle contractions, there should be a close relationship between bone strength and muscle force or size. The proposed two-step diagnostic algorithm requires a measure of muscle force or size and a measure of bone mineral content at a corresponding location. The results can be combined into four diagnostic groups. In the first situation, muscle force or size is adequate for height. If the skeleton is adapted normally to the muscle system, the result is interpreted as ‘normal’. If it is lower than expected for muscle force or size, a ‘primary bone defect’ is diagnosed. In the second situation, muscle force or size is too low for height. Even if the skeleton is adapted adequately to the decreased mechanical challenge, this means that bone mass, and presumably strength, are still too low for body height. Therefore, a ‘secondary bone defect’ is diagnosed. Finally, if both muscle force or size and the skeleton are inadequately adapted, a ‘mixed bone defect’ is diagnosed. It is hoped that the more detailed insights thus gained could help to devise targeted strategies for the prevention and treatment of paediatric bone diseases.

Analyses of muscular mass and function: the impact on bone mineral density and peak muscle mass

Bone density and bone mass are commonly regarded as the essential parameters to describe fracture risk in osteology. Because fractures primarily depend on bone strength and secondarily on bone mass and density, bone strength should be the main parameter to describe fracture risk. The quantitative description of bone strength has the prerequisite that bone geometry is assessed despite bone density. Thus, volumetric osteodensitometric methods should be preferred, which enable the physician to evaluate parameters primarily associated with bone modeling or remodeling. Modeling describes the adaptation of bone geometry to applied muscular forces in contrast to remodeling representing bone turnover. The adaptation of bone geometry to muscle forces led to the term functional muscle–bone unit, which enables the physician to differentiate between primary and secondary bone diseases. Primary bone diseases are characterized by a defective adaptation of bone to muscle forces in contrast to secondary bone diseases, which are primary diseases of the neuromuscular system. Because muscle forces are essential in the feedback loop of bone adaptation to forces (mechanostat), the assessment of muscle function has become an essential part of osteologic diagnostics in pediatrics. Dynamometric and mechanographic methods have been introduced to properly characterize kinetic aspects of muscle function in children and adolescents. Therefore, emphasis should be put on the assessment of muscle function despite the evaluation of osteodensitometric parameters in pediatric osteology.

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.