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

Imaging methods for bone mass evaluation during childhood and adolescence: an update

The objective of the work was to prepare an update on imaging methods for bone evaluation during childhood and adolescence. The text was based on original and review articles on imaging methods for clinical evaluation of bone mass in children and adolescents up to 20 years old. They were selected from BIREME and PUBMED by means of the following keywords: bone density; osteoporosis/diagnosis; densitometry; tomography; ultrasonography; magnetic resonance imaging; and radiogrammetry and published in Portuguese or English, in the last 10 years (2006-2016). The article was organized into topics with the description of peculiarities, advantages and disadvantages of each imaging method and their possible clinical applicability. Despite the emergence of new technologies, dual energy X-ray absorptiometry (DXA) remains the gold standard method for low bone mass diagnosis in all age groups. However, interpretation is complex in children and adolescents and demands skilled people. Quantitative computed tomography (QCT) [central QCT, peripheral QCT (pQCT) and high resolution-pQCT (HR-pQCT)] and magnetic resonance imaging (MRI) evaluate real bone density, but are not yet available for routine use. Quantitative bone ultrasound (QUS) shows good perspectives for its use in primary prevention actions. Automated radiogrammetry shows promise as a method able to flag individuals who might benefit from a complete bone assessment, but the clinical value of the measures still needs to be established.

Bone speed of sound throughout lifetime assessed with quantitative ultrasound in a Mexican population

The purpose of this study was to assess the bone speed of sound (SoS) through lifetime of a large Mexican population sample by determining the SoS from the radius and tibia using quantitative ultrasound (QUS). This is a cross-sectional evaluation of participants in the Mexican Health Workers Cohort Study. QUS measurements were performed using Sunlight Omnisense 8000P; Z- and T-scores were calculated for both sexes at the distal third of the radius and midshaft tibia, both on the nondominant side. A locally weighted regression smoothing scatterplot model was used to identify different phases of bone accretion and loss. A total of 9128 participants aged 1-75 yr were measured with QUS. Bone SoS accretion began 5 yr earlier in girls than boys (p<0.05). Maximal SoS or peak bone SoS was noted at 28 yr in the radius and at 22 yr in the tibia. Postmenopausal women (45-50 yr) showed significant SOS decrease at both sites (p<0.05) compared with men. Using the locally weighted regression smoothing scatterplot model, we found 5 different phases that constitute the biological development of bone over the life course, from ages 1-6, 7-12, 12-25, 25-50, and 50-75 yr (p<0.05). Our study shows the age- and sex-dependent changes and different phases of bone development expressed by SoS measurements of the radius and tibia. The values reported in this study can be used as a reference for urban Mexican population.

Evaluation of ultrasound transmission velocity and 3-dimensional radiology in different bone types for dental implantology: a comparative ex vivo study

OBJECTIVE

To evaluate ultrasound transmission velocity (UTV) for assessment of mechanical bone quality, an ex vivo comparison of different bone types measured with UTV, 2-dimensional (2D) histomorphometry and with 3-dimensional (3D) radiology (cone-beam computerized tomography [CBCT], computerized microtomography [μCT]) was conducted.

STUDY DESIGN

Clinical cortical, cancellous, and mixed bone (each n = 6) was measured via UTV (m/s), CBCT (white pixel/black pixel ratio [WP/BP]), μCT (bone volume/total volume [μBV/TV]), and histomorphometry (bone volume/total volume [hBV/TV]). UTV values were correlated with 2D-histomorphometry and 3D-radiologic results.

RESULTS

For the cortical, cancellous, and mixed bone samples, respectively, UTV values were 1,945.17, 1,266.9,and 1472.2 m/s, WP/BP quotients were 0.96, 0.15, and 0.33, μBV/TV quotients were 0.94, 0.2, and 0.47, and hBV/TV quotients were 0.96, 0.24 and 0.39. Significant correlations between UTV and the other methods were seen (P < .0001).

CONCLUSIONS

Similar to the other methods, UTV is able to discriminate between different bone types ex vivo.

Ultrasound for the assessment of bone quality in preterm and term infants

OBJECTIVE

As 80% of intrauterine bone mineralization takes place during the last trimester of pregnancy, preterm infants should be supplemented postnatally with optimal doses of calcium, phosphate and vitamin D. Calcium and phosphate excretion in the urine may be used to monitor individual mineral requirements, but are sometimes difficult to interpret. The objective of this study was to assess the value of quantitative ultrasound (QUS) for the analysis of bone status in neonates.

STUDY DESIGN

All admissions to three independent tertiary neonatal intensive care units were studied. In 172 preterm and term infants with a gestational age between 23 and 42 weeks (mean 33.8±5.0) and a birth weight from 405 to 5130 g (mean 2132±1091 g) bone status was evaluated prospectively by quantitative ultrasound velocity using a standardized protocol. Infants were followed in regular intervals up to their first discharge home. While measurements were conducted in weekly intervals initially (n=55), 2-week intervals were regarded as sufficient thereafter due to limited changes in QUS values within the shorter period. Infants with a birth weight below 1500 g were followed during outpatient visits until up to 17 months of age.

RESULT

The intra-individual day-to-day reproducibility was 0.62%. QUS-values from the first week of life correlated significantly with gestational age and birth weight (r=0.5 and r=0.6; P<0.001). Small-for-gestational-age infants showed lower values for QUS than appropriate-for-gestational-age infants allowing for their gestational age. Follow-up measurements correlated positively with age and weight during the week of measurement (r=0.2 and r=0.4; P=0.001). Comparing bone quality at 40 weeks of age in infants born at term versus infants born at 24 to 28 weeks, preterm infants showed significantly lower QUS than term infants (P<.0001).There was a significant correlation of QUS with serum alkaline phosphatase (P=0.003), the supplementation with calcium, phosphate and vitamin D (P< 0.001 each), as well as risk factors for a reduced bone mineralization. No correlation was found between QUS and calcium or phosphate concentration in serum or urine.

CONCLUSION

QUS is a highly reproducible, easily applicable and radiation-free technique that can be used to monitor bone quality in individual newborns. Further prospective randomized-trials are necessary to evaluate, if therapeutic interventions based on QUS are able to prevent osteopenia of prematurity.

Quantitative ultrasound measurement of the calcaneus in Southeast Asian children with thalassemia: comparison with dual-energy X-ray absorptiometry

OBJECTIVES

The purpose of this study was to test the hypothesis that quantitative ultrasound properties of the calcaneus in Southeast Asian children treated for thalassemia have different characteristics than those of their healthy counterparts and thereby can be used for assessing the risk of osteoporosis.

METHODS

Broadband ultrasound attenuation and the speed of sound were measured from groups of thalassemic and healthy children and compared with bone mineral density (BMD) estimated from dual-energy X-ray absorptiometry to determine intergroup and intragroup dependencies of the measurements and variations with differences in sex and anthropometric characteristics.

RESULTS

Broadband ultrasound attenuation and speed of sound measurements were found to be independent of sex but dependent on age in the thalassemic children. Consistently, broadband ultrasound attenuation had lower values and the speed of sound had higher values compared with those of the healthy children in each age group. Broadband ultrasound attenuation correlated well with the speed of sound and also with age, weight, and height, but the speed of sound did not show an association with these parameters. Broadband ultrasound attenuation correlated moderately with BMD in the lumbar spine and whole body, but the corresponding association was much weaker for the speed of sound. In the thalassemic children, both broadband ultrasound attenuation and BMD increased with age as they grew older but not fast enough compared with the healthy children, and the risk of osteoporosis was greater at older ages.

CONCLUSIONS

Calcaneal quantitative ultrasound may be used as a diagnostic screening tool for assessing the bone status in thalassemic Southeast Asian children and for deciding whether further dual-energy X-ray absorptiometry is needed, particularly in those who are at a greater risk for osteoporosis as identified by low body weight and height.

Evidence-based review of bone strength in children and youth with cerebral palsy

Children with cerebral palsy have various risk factors for compromised bone health. Evidence concerning their bone fragility is gathering; however, there is no consensus regarding risk factors, indications for evaluation, follow-up, or treatment. We performed an evidence-based review targeted to address the following questions concerning children with cerebral palsy: Is bone strength impaired and what are the risk factors? Are these children at increased risk for bone fractures? What are the relations between bone mineral density and fracture risk? What methods can be used for bone health assessment? How can bone strength be improved? Currently, the most acceptable method for evaluating bone status in children is dual-energy x-ray absorptiometry. Evidence demonstrates reduced bone mass in children with cerebral palsy; yet, no clear association with fractures. Preventive methods are suggested.

Reference values for quantitative ultrasonography (QUS) of radius and tibia in healthy greek pediatric population: clinical correlations

The aim of this study was to provide reference standards for measurements of quantitative ultrasonography (QUS) of radius and tibia in normative Greek pediatric population. Analysis was performed in 1549 healthy subjects (814 girls and 735 boys) with a mean decimal age of 11.41+/-3.52 yr (range: 3.78-18.33 yr). Results showed a gradual increase of absolute values of radial and tibial speed of sound (SOS), with aging and with pubertal progressing, in both girls and boys. Gender comparison showed significantly increased SOS values measured both at radius and at tibia in girls more than 13 yr of age compared with aged-matched boys. Significant but mild correlation was noted between standard deviation scores (SDS) of SOS at radius and at tibia (r = 0.259, p < 0.001). Additionally, tibial SOS SDS were significantly negatively correlated with body mass index (BMI) SDS (r = -0.230, p < 0.001). Finally, subjects that spend more than 3h of daily "screen time" (television and personal computer) showed significantly decreased SOS values measured both at radius and at tibia. On the contrary, no correlation was observed between SOS values and the amount of physical activity reported.

Methods for measurement of pediatric bone

Many experts believe that optimizing bone mineral accrual early in life may prevent childhood fractures and possibly delay the development of osteoporosis later in life. Adequate nutrition and physical activity are environmental factors important in determining whether or not children acquire an appropriate amount of bone for their body size. Pediatric diseases, or therapeutic interventions used in their treatment, may interfere with normal bone development. Although there are specific methods available for assessing pediatric bone, there is no one method that can adequately assess bone health and identify the specific bone deficits that may be occurring. Understanding the biological basis for bone deficits and the ability of various bone assessment methods to discriminate or measure these deficits is important in understanding normal bone development and how to prevent and treat pediatric bone disease. The purpose of this review is to briefly describe changes in bone with growth, to define "bone density" in biological terms, to discuss some of the issues with pediatric bone measurements, and to review the three main methods for assessing bone parameters in pediatric populations. These methods, including dual energy X-ray absorptiometry (DXA), quantitative ultrasound (QUS) and peripheral quantitative computed tomography (pQCT) will be described, the advantages and disadvantages discussed, and the relationship between bone parameters and fracture risk presented for each of the methods.

Quantitative ultrasound methods to assess bone mineral status in children: technical characteristics, performance, and clinical application

Measurement of bone mineral status may be a useful tool in identifying the children who could be exposed to an increased risk of osteoporosis in adulthood. Dual energy x-ray absorptiometry and peripheral quantitative computed tomography may be used to this purpose, but the exposure to ionizing radiation is a limiting factor for preventive studies in large populations of children. In the last years, quantitative ultrasound (QUS) methods have been developed to assess bone mineral status in some peripheral skeletal sites such as calcaneus, phalanges of the hand, and tibia. QUS techniques are safe, easy to use, radiation-free, and devices are portable, so that they are particularly indicated to assess bone mineral status in children. This review will concentrate on the main methodological principles of ultrasounds and the QUS variables derived from their application to bone tissue, technical differences and performance of QUS methods, factors influencing QUS measurements, normative data and results obtained in children with disturbances of growth or affected by disorders of bone and mineral metabolism, including the assessment of fracture risk, and comparison among QUS, dual energy x-ray absorptiometry, and peripheral quantitative computed tomography methods.

Decreased neonatal tibial bone ultrasound velocity in term infants born after breech presentation

OBJECTIVE

Fetuses found to be in the breech presentation have limited motion of their lower limbs. The aim of this study was to test the hypothesis that bone speed of sound (SOS) would be lower in infants born after breech presentation than in those born after vertex presentation.

STUDY DESIGN

We studied 127 singleton, appropriate for gestational age, term infants delivered by a scheduled cesarean delivery at approximately 38 weeks of gestation because of breech presentation or repeat elective cesarean section with vertex presentation. We used the Sunlight Omnisense 7000p device to measure axially transmitted SOS of the right tibia within the first 96 h of life.

RESULT

Fifty-three infants studied (42%) were born by cesarean section after breech presentation compared to 74 vertex controls. Bone SOS was significantly lower in the breech presentation group, even after taking into account the effect of gender and parity (as well as gestational age at birth and birth weight).

CONCLUSION

Bone SOS is lower in infants born after breech presentation than in those born after vertex presentation. We speculate that limited motion of lower limbs in fetuses found to be in the breech presentation leads to a decrease in bone mineralization and strength.

Bone ultrasound velocity in small- versus appropriate-for-gestational age preterm infants

OBJECTIVE

To compare bone status of small-for-gestational age (SGA) versus appropriate-for-gestational age (AGA) newborn preterm infants.

STUDY DESIGN

Tibial speed of sound (SOS) was measured in 144 infants categorized as SGA or AGA using the reference tables of Lubchenco et al. and Alexander et al.

RESULTS

By the Lubchenco tables, 22% of infants were SGA and 75% were AGA. The mean gestational ages of SGA and AGA were similar (33.3+/-2.6 and 32.5+/-2.4 weeks, respectively, P = 0.09); however, SGA infant birth weights were lower (1329+/-392 and 1829+/-481 g, respectively, P<0.001). SOS values were higher for SGA versus AGA infants (3098+/-135 and 3003+/-122 m/s, respectively. P<0.001). Use of the Alexander tables yielded a twofold increase in the percent of infants categorized as SGA; SOS values remained significantly greater for SGA infants (P<0.001).

CONCLUSION

Higher tibial SOS values in SGA versus AGA infants indicate greater bone strength.

Normal DXA bone mineral density but frail cortical bone in Turner's syndrome

CONTEXT

Patients with Turner's syndrome have normal bone mineral density by dual energy X-ray absorptiometry (DXA), but a predisposition for fractures. Quantitative ultrasonography (QUS) measures cortical bone strength.

OBJECTIVE

To compare QUS with DXA in patients with Turner's syndrome.

PATIENTS AND METHODS

Twenty-seven Turner's syndrome patients, aged 21.1 +/- 6.3 years (mean +/- SD), were evaluated by DXA, measuring two-dimensional bone mineral density (BMD), and QUS, measuring speed of sound (SOS) of the radius and tibia. The results were compared to sex- and age-matched (Ctr A, n = 53) and height-matched (Ctr B, n = 34) control groups.

RESULTS

Fracture incidence per 1000 women years was 4.76 in Ctr A, 5 in Ctr B and 7.69 in Turner's patients. In Turner's syndrome patients, QUS results were significantly lower than in controls, whereas DXA Z-scores were not different from reference values. Correlation between tibia and radius SOS and height and age in controls (P < 0.0001) was not evident in Turner's syndrome. Oestrogen or growth hormone therapy had no effect on either QUS or DXA parameters.

CONCLUSIONS

Bone fragility in Turner's syndrome is reflected by low SOS but not by DXA BMD. Low QUS, which assesses the cortical bone only, supports a defect in cortical bone in Turner's syndrome. Lack of SOS correlation with age, height and hormonal therapy in Turner's syndrome suggests a primary bone defect, rather than enhanced resorption of endocrine origin.

Skeletal measurements by quantitative ultrasound in adolescents and young women with anorexia nervosa

OBJECTIVE

To compare quantitative ultrasound (QUS) measurements in adolescents with anorexia nervosa (AN) with that in healthy control subjects and to determine the utility of QUS as a tool to evaluate skeletal status in these patients.

STUDY DESIGN

Female adolescents with AN (n = 41) and healthy control subjects (n = 105) were recruited. Speed of sound (SOS) was measured at the radius and tibia. Participants with AN also had hip and spinal areal bone mineral density measurements by dual-energy x-ray absorptiometry (DXA); bone mineral apparent density (BMAD) was calculated.

RESULTS

Subjects with AN had higher mean radial SOS (4044 +/- 99 m/s) than did control subjects (3947 +/- 116 m/s; P < .0001). These results were replicated at the tibia (AN, 3918 +/- 85 m/s vs control subjects, 3827 +/- 106 m/s; P < .0001). Neither DXA measures of areal bone mineral density nor BMAD were correlated with SOS. Weight and body mass index were negative predictors of tibial but not radial SOS. AN status remained a significant predictor of SOS after controlling for body mass index, age, and race.

CONCLUSIONS

Subjects with AN had higher mean tibial and radial SOS than did control subjects. QUS variables did not correlate with DXA measures, calculated BMAD, or anthropometric variables. QUS measurements of SOS do not appear to be appropriate for bone density screening in patients with AN.

Assessing bone mass in children and adolescents

Growing awareness that osteoporosis may have its antecedents in childhood has led to increasing interest in assessing bone mass in children and adolescents. Several noninvasive imaging techniques are currently available to measure properties of the growing skeleton, including bone mass, density, cross-sectional area, and microarchitecture. Dual-energy x-ray absorptiometry (DXA) is the most widely used technique, but it has several major limitations associated with its dependence on two-dimensional projections. Quantitative CT and peripheral quantitative CT allow three-dimensional imaging but are more costly and have higher radiation exposure. Quantitative ultrasound is simple and inexpensive but can measure bone "quality" only at a single peripheral site. MRI techniques for measuring bone are still under development and not yet ready for clinical use. For all of these techniques, clinical interpretation of the bone measures obtained remains a significant challenge. Further research is needed to relate these measures to osteoporosis in the elderly and to short-term and long-term fracture risk.

Effects of nutrition, puberty, and gender on bone ultrasound measurements in adolescents and young adults

PURPOSE

Quantitative ultrasound (QUS) evaluation of bone is attractive for evaluating skeletal status in adolescents, but its use is limited in the United States due to sparse pediatric reference data. This study evaluated associations between radial and tibial speed of sound (SOS) measurements via QUS and demographic, anthropometric and nutritional variables.

METHODS

We enrolled 151 healthy participants, aged 11-26 years, during routine visits to an urban adolescent clinic. SOS measurements were obtained using the Omnisense 7000P (Sunlight Medical Ltd., Tel-Aviv, Israel) and correlated with weight, height, gender, race, sexual maturity rating (SMR), and reported nutritional intake.

RESULTS

The sample was 53% female; aged 17+/- 2.8 years (mean +/- SD); and 48% African-American, 21% Hispanic, and 21% Caucasian. Seventy percent of males and 91% of females had achieved SMR 5; 96% of females were postmenarchal. Males met the recommended daily allowance for calcium intake, on average; the females did not. Both the girls and boys reported consumption of inadequate vitamin D. Intake of neither calcium nor vitamin D was correlated with SOS. Radial and tibial SOS were significantly higher in those with SMR 5 (p < .001) and were moderately correlated with age in both genders (r = .42-.64, p < .001). In multivariate analyses, age was associated with SOS at both sites (p < .0001).

CONCLUSIONS

This study provides QUS measurements of the peripheral skeleton among healthy adolescents. QUS measurements followed similar age and pubertal distributions to dual-energy X-ray absorptiometry (DXA) bone density measurements; other variables did not follow expected trends. Further research is needed to clarify what skeletal properties are assessed by this technique. This study adds to accumulating evidence that many adolescents do not consume adequate vitamin D or calcium.

Longitudinal assessment of bone quality by quantitative ultrasonography in children and adolescents

Among the techniques available to assess bone quality, quantitative ultrasonography of the proximal phalanges of the hand (QUS) has emerged as particularly attractive. In this study, amplitude-dependent speed of sound (AD-SoS) and bone transmission time (BTT) were obtained by the sonographic device DBM Sonic BP IGEA in two sessions at two years' interval, in a school-age population (589 subjects, 290 mol/L and 299F, aged 3 to 16 y) with the aim to determine accuracy of QUS measurements, evaluate QUS variable changes during growth, relate these values with age and growth variables. Mean AD-SoS and BTT at age classes from 5 to 12 y as determined at the first and second measurement sessions were not significantly different. A significant increment (p < 0.0001) between the first and the second measurement was observed for both QUS variables. AD-SoS and BTT showed significantly different variations in the various age groups (ANOVA). Correlations were found of AD-SoS and BTT increments with age, height, weight, pubertal stage and with height growth velocity (p < 0.05). AD-SoS and BTT increment curves presented a very similar trend decreasing from 4 to 7 y of age. Thereafter a plateau was reached up to the age of 10 to 11 y in girls and 11 to 12 y in boys, when an increase was observed corresponding to pubertal growth rate acceleration. In conclusion, the present study would confirm that QUS measurements are accurate. Ad-SoS and BTT increment models are similar to most growth velocity curves and follow a strongly age- and growth-dependent pattern.

Monitoring bone mass, bone density and bone geometry in children and adolescents

The number of articles dealing with pediatric bone mass measurements has flourished during the last decade. The reasons include the awareness that bone gained early in life is an important factor in determining the risk of osteoporosis later in life and the expanding number of pediatric diseases associated with low bone mass. Dual-energy x-ray absorptiometry is the most common method for measurement of bone mineral content or bone mineral density. Quantitative computed tomography and quantitative ultrasound are the emerging techniques which offer the possibility of measuring bone mineral content, bone mineral density and quantitative ultrasound parameters that are unique to children and will be discussed in this review. The interpretation of bone mass measurements is also often difficult in growing individuals and the peculiar aspects pertaining to this problem are examined.

Bone health in pediatric rheumatic disease

PURPOSE OF REVIEW

Children with chronic rheumatic disease have decreased bone mass. In adults, lowered bone mineral density is associated with increased fracture risk. This morbidity is undetermined in pediatric rheumatic disease as osteoporosis has not been well-defined in children. This review compares methods for determining bone mass in children, examines insights into molecular mechanisms of bone metabolism, and discusses the prevention and treatment of decreased bone mass in children.

RECENT FINDINGS

Peak bone mass, attained during adolescence and early adulthood, is critical in determining fracture risk. Studies of children with chronic rheumatic disease demonstrate decreased bone mineral density, and potentially lowered peak bone mass. Dual energy x-ray absorptiometry is the most commonly used technique for monitoring bone mineral density and should be interpreted utilizing age-appropriate Z-scores. Recent studies suggest quantitative ultrasound may be as reliable as dual energy x-ray absorptiometry and lacks radiation exposure. The molecular mechanisms by which inflammation alters bone mineral density involve receptor activator of nuclear factor kappaB ligand (RANKL)/osteoprotegerin, tumor necrosis factor-alpha, and interleukin-1. Limited data on the use of bisphosphonates and calcitonin in children suggest they are safe and effective, but should be used cautiously.

SUMMARY

Children with chronic rheumatic disease should have bone mass monitored by dual energy x-ray absorptiometry Z-scores. Targeting the RANKL/osteoprotegerin pathway may lead to therapies that improve bone health in this population. More studies on the role of bisphosphonates and calcitonin must be pursued to establish guidelines for use in pediatric patients with chronic rheumatic disease. For now, supplemental calcium and vitamin D should be implemented in these children.