Idiopathic juvenile osteoporosis--an analysis of the muscle-bone relationship.

INTRODUCTION: Idiopathic Juvenile Osteoporosis (IJO), a disease of unknown etiology, manifests typically by pain, bone deformities and fractures. Due to limits in BMD data interpretation, evaluation of the muscle-bone functional unit has recently been proposed as a means to assess the general competence of the skeleton. The aim of this study was to evaluate skeletal status during the acute phase of IJO and during recovery from the disease in relation to muscles. MATERIALS AND METHODS: The study population comprised 61 IJO children, including 34 girls (mean age: 13.6+/-3.1 years; range: 7-18) and 27 boys (14.3+/-3.3; 5-18 years). DXA total body (TB) and lumbar spine (S) bone mineral content (BMC) and density (BMD) were measured. Lean body mass (LBM) was employed to calculate SBMC/LBM, TBBMC/LBM, body height (BH)/LBM and LBM/body weight (BW) ratios. Previously established references for healthy controls were utilized for the calculation of Z-score values in IJO cases in respect to phase of the disease. RESULTS: IJO patients had significantly decreased Z-score values for TBBMD, SBMD, SBMC/LBM and TBBMC/LBM ratios but not for the LBM and BH/LBM or LBM/BW ratios. During the acute phase IJO girls had mean Z-scores for TBBMD and SBMD of -2.49+/-0.61 and -3.27+/-1.03, respectively, which were significantly lower than Z-scores during the recovery phase: -0.90+/-0.66, -1.38+/-0.95 (p<0.0001). IJO boys during the acute phase had Z-scores of -2.08+/-0.65 and -2.75+/-1.19 for TBBMD and SBMD, respectively, which were significantly lower than those during the recovery phase (-0.51+/-1.04 and -1.39+/-1.49; p<0.0001). Further, during the acute phase, TBBMC/LBM Z-scores of -2.95+/-1.15 and -2.56+/-1.49 were noted in girls and boys, respectively; the corresponding SBMC/LBM Z-scores were -2.66+/-1.07 and -2.22+/-1.62. During the recovery from IJO, TBBMC/LBM and SBMC/LBM Z-scores of -1.07+/-0.99 and -0.91+/-1.16 and of -1.15+/-1.40 and -0.68+/-1.45 were noted in girls and boys, respectively, and all were significantly higher than those during the acute phase (p<0.0001). CONCLUSIONS: The results of this study indicate that IJO is a bone disorder characterized by an imbalanced muscle-bone relationship and fractures at onset and during the acute phase and by at least a partial recovery without bone pain and new fractures. Implementation of the BH/LBM, TBBMC/LBM and SBMC/LBM ratios to the armamentarium of pediatricians diagnosing bone disorders will provide mechanically meaningful data for diagnostic purposes and, hopefully, for proper therapeutic decisions.

[Measurements of calcaneus bone density by ultrasonography in children and adolescents]. / Pomiary gestosci kosci pietowej metoda ultrasonograficzna u dzieci i mlodziezy.

In recent years the interest in growing in the use of ultrasonographic method for the assessment of bony tissue density. However, studies using this method were conducted almost exclusively in adult patients. The aim of this study was to apply this method for measurements in children in wide age range (7-18 years) and to determine value range of the parameters SOS, BUA and Stiffness for children in Warsaw in age and sex groups. The studies included 233 children of either sex, aged 7-18 years, healthy on medical examination coming from Warsaw schools. Achilles (Lunar Corp. WI, USA) bone densitometer was used with producer's software, 1.5c version. During examination with the Achilles device, the velocities of ultrasound beam passage through the calcaneus (SOS m/s) and the damping factor of ultrasound wave depending on its frequency (BUA db/MHz) were measured. Additionally the so called "stiffness factor" was calculated. The Achilles device was adapted for measurements in children reducing the diameter of the measuring beam to 1 cm and using pads positioning the child's foot in the device. Equal increase of SOS, BUA and Stiffness parameters with age was observed with the exception of the SOS parameter in girls which increased intensively from 7 to 12 years of age while over 12 years of age its increase was slight. Using linear regression analysis it was found that the values of SOS, BUA and Stiffness parameters depended directly proportionally on age, body weight and height. Respective correlation factors (r) were from 0.49 (body weight-SOS to 0.80 (height-BUA). The observed dependence of the SOS, BUA and Stiffness parameters on body weight, height and especially age enables presuming that the results of calcaneus density measurements by ultrasonographic method reflect the skeletal development in children.

Ultrasound bone measurement in pediatric subjects.

Ultrasound bone measurement in healthy (n = 71) and osteopenic (n = 18) children aged 6 through 13 years of both sexes has been evaluated using the Achilles densitometer (Lunar Corporation). Measurements on the os calcis included speed of sound (SOS), broadband ultrasound attenuation (BUA), and a calculated "stiffness" index. The Achilles was adapted for children by a special positioning procedure that included the use of foot shims, and beam collimation on the receiving transducer. The precision of ultrasound results was comparable to that in adults (0.2% for SOS, 1.5% for BUA, and 1.8% for stiffness). SOS, BUA, and stiffness values increased with age in both sexes. Ultrasound measurements were correlated with bone mineral density (BMD in g/cm2) of the heel, AP spine (L2-L4), and total body by dual X-ray absorptiometry (DXA) densitometry (Lunar DPX-L). SOS, BUA, and stiffness measurements were significantly lower in osteopenic children (Z approximately -1.9 to -2.5) (P < 0.0001) than in normal age-matched controls. Total body BMD showed a higher Z-score than stiffness (-3.3 versus -2.5), but stiffness showed a greater percentage decrease (-30% versus -18%). In conclusion, ultrasound measurements of bone in children provide both good precision and discrimination of normals from osteopenic patients.

Potential of densitometric measurement in selected pediatric subject.

On the aim to recognize bone mineral measurements as somatic development parameter as well as its clinical usefulness in pediatric clinic, the investigations with of DPX-L were performed. Material consisted of 302 healthy scholars both sex and 85 patients aged 6.0-18.9 yrs children diagnosed as idiopathic juvenile osteoporosis (IJO) and osteogenesis imperfecta (OI). Total body mineral density (TBBMD) was evaluated as developmental parameter in normal children population and utilized in differential diagnosis and monitoring of bone pathology in children with IJO and OI.

[Evaluation of bone mass in children in a national sample of the population]. / Ocena masy kostnej u dzieci w krajowej próbie populacyjnej.

Dual energy X-ray absorptiometry (DEXA) was used to measure a mean bone mineral density (BMD) and bone mineral content (BMC) in total body and lumbar spine (L2-L4--BMD; L2-L4--BMC) in a group of 306 healthy children of both sexes, aged between 6 and 18 years. Step-wise increase in BMD in peripubertal age was noted. A degree of an increase in BMD at the age of 10 and 16 years was higher in boys than in girls. Bone mineral density of the spine was lower in the Polish population than that in USA. A high degree correlation between densitometric measurements and calendar age, and body height and weight was noted.

[Dynamics of the course of idiopathic juvenile osteoporosis]. / Dynamika przebiegu idiopatycznego osteoporozy mlodzienczej.

Clinical course of the idiopathic juvenile osteoporosis (IJO) was monitored in the group of 45 patients of both sexes with diagnosed disease, verified during follow-up period. The aim of the study was to evaluate the relationship between clinical symptoms and the results of biochemical, anthropometric, and densitometric measurements. An analysis of the obtained data enabled to distinguish the acute and chronic IJO phases. Evolution of the acute phase into chronic one was manifested by the cessation of pain and pathological gait stereotype, normalization of muscular strength, anthropometric parameters and urinary Pyr and DPyr excretion, as well as improvement in bone density. Hypercalciuria and increased urinary excretion of Pyr and DPyr, observed in the acute phase of IJO, may indicate that bone resorption exceeded bone formation. Tendency to maintain of alkaline phosphatase activity within lower limits of the normal values with slight increase during an improvement of densitometric parameters suggested transient osteoblast dysfunction.

[Measurements of bone mineral density of the calcaneus in children with ultrasonic methods]. / Pomiary gestosci kosci pietowej u dzieci metoda ultrasonograficzna.

The study aimed at determining precision and accuracy of the ultrasound technique measuring bone mineral density in the calcaneus bone in children. Bone densitometer of Achilles type was adapted for measurements in children. Ultrasound beam was narrowed and a system of special pads positioning the foot were used for this purpose. Precision (CV (%) SOS: phantom 0.42, patients -0.42; BUA: phantom 1.46, patients -3.03) and accuracy of this technique were determined in comparison with dual energy X-ray absorptiometry as well as its value in diagnosis of osteopenia in childhood. An increase in SOS and BUA with the age was found. A decrease in these parameters was noted in children with osteopenia, comparing with the values in healthy children. Significant correlations (r ranging from 0.50 to 0.91) between ultrasound and DEXA techniques were seen. The results suggest that ultrasound technique might be useful in pediatric densitometry.

[Pyridinoline and deoxypyridinoline excretion in urine of healthy children--dependence on age]. / Wydalanie pirydynoliny i dezoksypirydynoliny w moczu dzieci zdrowych--zaleznosc od wieku.

Pyridinoline (Pyr) and deoxypyridinoline (DPyr) are crosslinking compounds of bone collagen. Their urinary excretion is considered to be the first sensitive and specific marker of bone resorption in a number of metabolic bone diseases in adults. Application of crosslinks measurements to evaluate bone turnover rate in pediatric patients is so far limited because of lack of reference values. Therefore, the aim of our study was to determine urinary excretion of Pyr and DPyr in healthy children aged 3-18 yrs, and to evaluate the possible relationship between the levels of both compounds and body height, weight, BMC, and BMD. Pyr and DPyr levels were determined in first void urine samples obtained from 249 children (124 boys, 125 girls). Urine aliquots were hydrolysed, Pyr and DPyr extracted on CF1 cellulose, and analysed by HPLC with fluorimetric detection. Bone mineral content (BMC) and density (BMD) were measured with Lunar DPX-L apparatus in 205 children (104 boys, 101 girls) from the same population, aged over 5.5 yrs. In prepubertal children, a tendency towards lowering of urinary Pyr and DPyr levels with advancing age was shown. At puberty, urinary excretion of both crosslinks markedly decreased. This phenomenon was observed at various calendar age in girls as compared to boys, reflecting sex-dependent differences. Significant negative correlation (p < 0.0001) between urinary Pyr and DPyr levels and calendar age, body height and weight, BMC and BMD, were also found. The obtained results suggest that references values for Pyr and DPyr excretion in growing children should be related to calendar age, sex, and--in case of adolescents--phase of puberty.

[Rehabilitation procedures for osteoporosis in children: practical advice]. / Postepowanie rehabilitacyjne w osteoporozie u dzieci: uwagi praktyczne.

The authors, basing on their own experience, propose rehabilitation program for osteoporotic children. Such a program may restore basic locomotive system functions in the period of time up to 12 weeks. Efficacy of the proposed rehabilitation program was evaluated with orthopaedic examination, X-ray, densitometry, and biochemical measurements in 210 children of both sexes who were followed-up for 3 years. The program includes motoric rehabilitation with specifically designed exercises. Basic exercises include active exercises without loading, isotonic resistive exercises and exercises in water whereas auxiliary program includes relaxing and active-passive exercises. The authors discuss rehabilitation priorities in osteoporosis such as the use of analgesics and early erect positioning. An effective rehabilitation requires, however, hospitalization.