Eckhard Schönau

Problems of bone analysis in childhood and adolescence

Abstract. The monitoring of bone metabolism and skeletal development during childhood and adolescence is becoming increasingly important in the prevention of osteoporosis. This is especially important in patients with chronic disorders. The predominant changes in the skeletal system during growth occur as geometric adaptation processes which lead to an increase in bone mass and bone strength. These changes can be measured with linear absorption methods (single-photon absorptiometry, dual-photon absorptiometry, dual-energy X-ray absorptiometry), computed tomographic procedures (peripheral quantitative computed tomography, quantitative computed tomography), and sonographic procedures. The aim of this review is to explain the problems of interpretation of the investigations due to growth-dependent changes. Almost all methods and their parameters, such as bone density, spongiosa density, cortical density, ultrasound transmission velocity, etc., are influenced, in varying degree, by growth-dependent skeletal changes.

The determination of ultrasound velocity in the os calcis, thumb and patella during childhood

Maximising the accumulation of bone tissue during growth and puberty is one of the most important aims in the prevention of osteoporosis. For prevention studies in children it is necessary to develop methods for skeletal status without radiation. Ultrasonic velocity (speed of sound=SOS) has been proposed as an alternative method. Using a new ultrasonic system (Osteoson K4, Minhorst, Germany), we investigated the reproducibility and age-dependency of SOS in several peripheral bones in 218 children and young adults. Intra-observer (day to day) reproducibility: calcaneus CV=0.64%, patella CV=1.18% and thumb CV=0.43% (n=25). Inter-observer reproducibility: calcaneus CV=1.1%, patella CV=2.48% and thumb CV=0.62% (n=16). SOS in thumb and patella increased with age and peaked at 20–25 years. SOS in the calcaneus showed no increase after puberty. Studies in bones from pigs show no dependency of SOS from the thickness of analysed cortical or trabecular bone slices. We conclude that the reproducibility of SOS measurements especially in the thumb is comparable with those of radiation methods. The SOS data in growing, healthy children and the independency from bone dimensions provides more evidence that SOS describes the elastic qualities of the bones.

Whole-body vibration training in children with Duchenne muscular dystrophy and spinal muscular atrophy

INTRODUCTION Whole-body-vibration training is used to improve muscle strength and function and might therefore constitute a potential supportive therapy for neuromuscular diseases. OBJECTIVE To evaluate safety of whole-body vibration training in ambulatory children with Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA). METHODS 14 children with DMD and 8 with SMA underwent an 8-week vibration training programme on a Galileo MedM at home (3 × 3 min twice a day, 5 days a week). Primary outcome was safety of the training, assessed clinically and by measuring serum creatine kinase levels. Secondary outcome was efficacy as measured by changes in time function tests, muscle strength and angular degree of dorsiflexion of the ankles. RESULTS All children showed good clinical tolerance. In boys with DMD, creatine kinase increased by 56% after the first day of training and returned to baseline after 8 weeks of continuous whole-body vibration training. No changes in laboratory parameters were observed in children with SMA. Secondary outcomes showed mild, but not significant, improvements with the exception of the distance walked in the 6-min walking test in children with SMA, which rose from 371.3 m to 402.8 m (p < 0.01). INTERPRETATION Whole-body vibration training is clinically well tolerated in children with DMD and SMA. The relevance of the temporary increase in creatine kinase in DMD during the first days of training is unclear, but it is not related to clinical symptoms or deterioration.

Analysis of the functional muscle–bone unit of the forearm in patients with phenylketonuria by peripheral quantitative computed tomography

Bone disease in patients with phenylketonuria (PKU) is incompletely characterized. We therefore analyzed, in a cross-sectional study radius macroscopic bone architecture and forearm muscle size by peripheral quantitative computed tomography (pQCT) and muscle strength by hand dynamometry in a large cohort (n = 56) of adolescent and adult patients with PKU aged 26.0 ± 8.9 (range, 11.8–41.5) years. Data were compared with a reference population (n = 700) from the DONALD study using identical methodology. We observed a significant reduction of cortical thickness (z-score −1.01 ± 0.79), Strength–Strain Index (SSI) (z-score −0.81 ± 1.03), and total bone mineral density (BMD) of the distal radius (z-score −1.05 ± 1.00). Mean muscle cross-sectional area (z-score −0.98 ± 1.19) and muscle grip force (z-score −0.64 ± 1.26) were also significantly reduced, indicating an impaired muscular system as part of the clinical phenotype of PKU. SSI positively correlated (r = 0.53, P < 0.001) with the corresponding muscle cross-sectional area in the reference population; however, the regression line slope in PKU patients was less steep (P < 0.001), indicating that bone strength is not adequately adapted to muscle force. In conclusion, the radial bone in PKU patients is characterized by reduced bone strength in relation to muscular force, decreased cortical thickness, and impaired total BMD at the metaphyseal site. These alterations indicate a mixed bone defect in PKU, both of which are due to primary alterations of bone metabolism and to secondary alterations in response to neuromuscular abnormalities.

Knochengesundheit bei Kindern

„Knochenstoffwechselstörungen“ aufgrund von Mangelernährung, wie sie zu Beginn des letzten Jahrhunderts häufig auftraten, sind heute in den Hintergrund getreten. Jedoch führen Änderungen des Lebensstils in den westlichen Nationen mit ihren Ernährungsgewohnheiten und dem veränderten Konzept von Arbeit und Freizeit zu Störungen im Knochenstoffwechsel und Wachstum.

Einflussfaktoren auf die Entwicklung des Skeletts

ZusammenfassungMuskeln und Knochen sind ein funktionelles System, das sich immer wieder den neuen Gegebenheiten anpasst. Der Aufbau der Knochenmasse erfolgt im Kindes- und Jugendalter. Körperliche Aktivität und gesunde Ernährung sind dafür wichtige Voraussetzungen.