Age estimation based on magnetic resonance imaging of the ankle joint in a modern Chinese Han population.

OBJECTIVES: To expand the database on magnetic resonance imaging (MRI) analysis of distal tibial and calcaneal epiphyses as proposed by Saint-Martin et al. and investigate a more elaborate staging technique to establish regression models for age estimation in a modern Chinese Han population. MATERIALS AND METHODS: T1-weighted ankle MRIs were retrospectively collected from April 2008 to July 2019, and data from 590 individuals (372 males and 218 females; aged from 8 to 25 years old) were obtained. One-sided sagittal images were assessed because data from both sides were considered coincidental, as no significant differences were found (P > 0.05). Three-stage and six-stage staging techniques were applied separately and subsequently compared. A subset was re-assessed a second time and by a different observer. Regression models were established accordingly. RESULTS: Our results showed very good repeatability and consistency of two staging techniques (all Cohen's kappa values were more than 0.8). By comparison, the values of the coefficient of determination (R2) of the six-stage technique were generally higher than those of the three-stage technique. Compared with the distal tibia and two ankle bones combined, the calcaneus decreased the mean absolute deviation (MAD) with the six-stage technique. In males, incorporating only the calcaneus resulted in a MAD of 2.15 years, with correct classification rates of 87.5% adults and 50.0% among minors. In females, the corresponding results were 1.67 years, 100.0%, and 44.4%, respectively. CONCLUSIONS: The six-stage technique may outperform the three-stage technique in MRI analysis of ankle bones for age estimation, while age estimation based on the calcaneus may perform better than that based on the distal tibia or both ankle bones in a modern Chinese Han population.

Calcaneal elongation and bone strength in leaping galagids.

OBJECTIVES: Small-bodied vertical clinging and leaping primates have elongated calcanei which enhance leap performance by optimizing leap velocity, distance, and acceleration, but at the expense of experiencing relatively large forces during takeoff and landing. This study tests the hypothesis that the elongated calcaneus of leaping galagids is adapted to resist larger and more stereotyped bending loads compared to more quadrupedal galagids. MATERIALS AND METHODS: The calcanei of 14 individuals of Otolemur and 14 individuals of Galago (three species of each genus) were µCT scanned. Calcaneal cross-sectional properties (maximum and minimum second moments of area and polar section modulus) were obtained from a slice representing the 50% position of bone segment length and dimensionless ratios were created for each variable using calcaneal cuboid facet area as a proxy for body mass. RESULTS: There were no significant differences in size-adjusted bending strength between Galago and Otolemur. Galago exhibited more elliptically shaped calcaneal cross sections, however, suggesting that its calcanei are more adapted to stereotyped loading regimes than those of Otolemur. DISCUSSION: The results suggest that the calcaneus of specialized leapers is adapted to more stereotyped loading patterns. The lack of predicted bone strength differences between Galago and Otolemur may be related to body size differences between these taxa, or it may indicate that loads encountered by Galago during naturalistic leaping are not reflected in the available experimental force data.

Relationship Between Sever Disease and Skeletal Maturity.

BACKGROUND: Sever disease is a common condition in active, growing children. This condition presents as pain in the heel and is thought to be an overuse condition of the calcaneal apophysis. There are currently no defined radiographic diagnostic criteria for evaluation of Sever disease, with radiographs generally showing normal appearance of the calcaneal apophysis. A better understanding of the relationship of Sever disease and skeletal maturity may allow for improved interpretation of radiographs when trying to diagnose this condition. METHODS: ICD-9 code 732.5 was used to search for patients diagnosed with Sever disease from 2007 to 2015 at a single hospital. For every patient with Sever disease with available calcaneal imaging within 40 days of diagnosis, heel x-rays were staged for calcaneal maturity score using a previously described calcaneal skeletal maturity assessment system. Controls matched by age, race, and sex were evaluated for calcaneal stage to compare with the Sever patients. RESULTS: The chart review yielded 78 patients diagnosed with Sever disease by the orthopaedic attending, 39 of which have x-rays around the time of diagnosis. Calcaneal scores averaged 2.2±0.8 for all patients, 2.1±0.9 for male individuals, and 2.3±0.8 for female individuals. The average age for male individuals was 10.4±1.9 years and for female individuals, 9.2±2.2 years. The ages of diagnosis were similar for patients with and without x-rays. Twenty-two of 39 patients with Sever disease were calcaneal stage 2, and 37 of 39 were stages 1, 2, or 3. We calculated the absolute difference from stage 2 for the Sever and control groups. Mean difference from stage 2 was 0.51±0.68 for the Sever patients and 0.95±0.79 for control patients (P=0.01). CONCLUSION: Sever disease occurs in a very narrow range of skeletal maturity, as measured by the calcaneal skeletal maturity assessment system and our observations with chronological age. When compared with age-matched and race-matched controls, stage 2 was seen more frequently in the Sever patients. If a child is not within calcaneal stages 1, 2, or 3, then a different diagnosis should be considered. LEVEL OF EVIDENCE: Level III-retrospective case-control study.

Applicability of the Calcaneal Apophysis Ossification Staging System to the Modern Pediatric Population.

BACKGROUND: The calcaneal apophysis ossification staging system is a novel method for assessing skeletal maturity. However, it was created using the same historic patient population that was used to create the Greulich and Pyle atlas of the hand and wrist, predominantly white children. It is unclear if the calcaneal apophysis ossification staging system is still applicable to the modern pediatric population and to children of other races. METHODS: We retrospectively studied 1327 benign lateral foot x-rays from modern white and black children. Calcaneal stage was determined and age, race, and sex were collected for each patient. A 2-tailed Student t test was used to compare between cohorts the differences in age for each calcaneal stage. RESULTS: Mean age was 11.55±4.39 years. Modern white females graded as stage 3 and 4 were significantly delayed in their bone age (stage 3 P<0.002; stage 4 P<0.003) when compared with their historic counterparts. Skeletal maturity was consistent between modern and historic white males for stages 1 to 4. Modern black females graded as stage 1 to 4 were significantly advanced in their skeletal age when compared with modern white females (stage 1 P<0.038; stage 2 P<0.005; stage 3 P<0.002; stage 4 P<0.002). Modern black males graded as stages 1, 3, and 4 were also significantly advanced in their bone age when compared with their modern white counterparts (stage 1 P<0.003; stage 3 P<0.012; stage 4 P<0.029). CONCLUSIONS: Modern white females mature more slowly in the later stages when compared with their historic counterparts. No significant difference is seen between modern and historic white males. Modern black females and males were skeletally advanced compared with modern white females and males. We have shown that the calcaneal ossification staging system can be used to assess for skeletal maturity in the modern pediatric population with only mild corrections for white females and more significant adjustments for black females and males. LEVEL OF EVIDENCE: Level III-retrospective chart review.

Age estimation by magnetic resonance imaging of the distal tibial epiphysis and the calcaneum.

Age estimation of living individuals is of critical importance in forensic practice, especially because of the increased migration in developed countries. Recently, the contribution of magnetic resonance imaging (MRI) to age evaluation has been studied, as it seems to be an efficient technique to analyze growth plate maturation and epiphyseal fusion. We developed an MRI staging system for the distal tibial epiphysis and the calcaneal epiphysis and evaluated its reliability on 180 MRI scans of the ankle and foot in a sample of individuals aged from 8 to 25 years old. For both bones, the degree of union between the metaphysis and epiphysis was classified in three stages. Intra- and inter-observer variabilities were good, showing the validity and reproducibility of the method. Our results were consistent with data in the literature indicating that both epiphyses mature earlier in females than in males. Bayesian predictive probabilities were used to assess the validity of our method in estimating the age of an individual in relation to the 18-year threshold. MRI of the ankle and foot can be used in association with other methods to estimate age in living individuals.

Talar maturity determined by epiphyseal closure of the calcaneus.

The talus is used in many kinds of studies on primates including fossil species, and most of the individuals studied are adults. One of the most important indicators of adult individuals is epiphyseal closure; however, because the talus has no epiphysis, it is difficult to determine the maturity of the talus. The calcaneus has one epiphysis, and it has been used along with the talus in some analyses. The objective of this study was to quantify the maturation trajectory of the talus using epiphyseal closure of the calcaneus as a benchmark. We used 71 skeletons of free-ranging Macaca fuscata fuscata males of known day-age. We did not identify any size increase with age in talar dimensions among specimens with complete calcaneal epiphyseal closure. Thus, in male M. fuscatafuscata, the maturation trajectory of the talus can be quantified using epiphyseal closure of the calcaneus as a benchmark.

Postnatal growth of the calcaneus does not simulate growth of the foot.

BACKGROUND: In the absence of age and sex-specific normative data for postnatal growth of the calcaneus, it has been hypothesized that the growth of the calcaneus would simulate growth of the foot. METHODS: A total of 860 normal lateral foot radiographs, 50 (25 female and 25 male) for each year of development from 1 to 18 years, and 10 radiographs from birth till 1 year, were measured for the length and height of the calcaneus, Bohler angle, the appearance, fusion and fragmentation of calcaneus apophysis, and the height and width of apophysis. Nonlinear curves were fit to a growth chart of the calcaneus, and the results were superimposed on the historical growth charts of the foot, stature, and long bones (femur, tibia). The ratio of calcaneus length to apophysis height was calculated. RESULTS: Growth of the calcaneus does not simulate growth of the foot (which attains 50% of its mature dimension by the age of 1 y in girls and 1.5 y in boys), but simulates the growth of the long bones, which attain 50% of their mature length after the age of 3 years in girls and 4 years in boys. Bohler angle remains within normal limits across all ages. When the length of calcaneus is triple the height of its apophysis, 80% of calcaneus growth is complete. CONCLUSIONS: We provide normative data for postnatal growth of the calcaneus. On the basis of these data, the assumption that growth disturbance in children affects the length of the calcaneus proportionately less than similar disturbances in the long bones, is false. Children <3 years have at least 50% of growth remaining. Bohler angle should be maintained at all ages. CLINICAL RELEVANCE: This study of postnatal growth of the calcaneus provides age and sex-based normative data to predict growth pattern of calcaneus.

Longitudinal changes in calcaneal quantitative ultrasound measures during childhood.

UNLABELLED: This longitudinal study examined how calcaneal quantitative ultrasound (QUS) measures change during childhood while taking into account skeletal maturation, body mass index (BMI), and physical activity. The study reported sex differences in QUS growth curves and an inverse relationship between BMI and speed of sound (SOS) measures. INTRODUCTION: The aim of this study was to examine how calcaneal QUS parameters change over time during childhood and to determine what factors influence these changes. METHODS: The study sample consisted of a total of 192 Caucasian children participating in the Fels Longitudinal Study. A total of 548 calcaneal broadband ultrasound attenuation (BUA) and SOS observations were obtained between the ages of 7.6 and 18 years. The best fitting growth curves were determined using statistical methods for linear mixed effect models. RESULTS: There are significant sex differences in the pattern of change in QUS parameters (p < 0.05). The relationship between QUS measures and skeletal age is best described by a cubic growth curve in boys and a linear pattern among girls. Boys experience their most rapid growth in BUA and SOS in early and late adolescence, while girls experience constant growth throughout childhood. Adiposity levels were significantly associated with the changes in SOS among boys (p < 0.001) and girls (p < 0.01), indicating that children with higher BMI are likely to have lower SOS over time compared to children with lower BMI. For girls, physical activity levels showed positive associations with changes in QUS measures (p < 0.05). CONCLUSION: This study documents significant sex differences in the pattern of change in QUS measures over childhood and adolescence. Our study also shows significant influences of adiposity and physical activity on the pattern of change in QUS measures during childhood.

Physical activity is the strongest predictor of calcaneal peak bone mass in young Swedish men.

SUMMARY: In a highly representative sample of young adult Swedish men (n = 2,384), we demonstrate that physical activity during childhood and adolescence was the strongest predictor of calcaneal bone mineral density (BMD), and that peak bone mass was reached at this site at the age of 18 years. INTRODUCTION: The purpose of the present study was to determine if physical activity during growth is associated with peak calcaneal BMD in a large, highly representative cohort of young Swedish men. METHODS: In this study, 2,384 men, 18.3 +/- 0.3 (mean +/- SD) years old, were included from a population attending the mandatory tests for selection to compulsory military service in Sweden. BMD (g/cm(2)) of the calcaneus was measured using dual-energy X-ray absorptiometry. Training habits were investigated using a standardized questionnaire. RESULTS: Regression analysis (with age, height, weight, smoking, and calcium intake as covariates) demonstrated that history of regular physical activity was the strongest predictor and could explain 10.1% of the variation in BMD (standardized beta = 0.31, p < 0.001). A regression model with quadratic age effect revealed maximum BMD at 18.4 years. CONCLUSIONS: We found that history of physical activity during growth was the strongest predictor of peak calcaneal BMD in young men.

Normative calcaneal quantitative ultrasound data as an estimation of skeletal development in Swedish children and adolescents.

We present age- and gender-specific normative bone status data evaluated by quantitative ultrasound (QUS) in the calcaneus with the Lunar Achilles device and compare these estimates with bone mineral content (BMC) and bone mineral density (BMD) estimated by dual X-ray absorptiometry (DXA). Included were a sample of 518 population-based collected Swedish girls and 558 boys aged 6-19 years. QUS measurements included speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI) in the calcaneus. DXA measurements included BMC and BMD in the femoral neck (FN), lumbar spine (L2-L4), and total body (TB). Height and weight were measured with standard equipment. Age, height, and weight were significantly associated with SOS, BUA, and SI. Compared to SOS, in both girls and boys there was a higher correlation between BUA and FN BMC (r = 0.71 and r = 0.73, respectively), FN BMD (r = 0.68 and r = 0.67, respectively), L2-L4 BMC (r = 0.70 and r = 0.64, respectively), L2-L4 BMD (r = 0.69 and r = 0.64, respectively), TB BMC (r = 0.76 and r = 0.75, respectively), and TB BMD (r = 0.74 and r = 0.74, respectively). The correlations between SOS and FN BMC (r = 0.38 and r = 0.52, respectively), FN BMD (r = 0.41 and r = 0.52, respectively), L2-L4 BMC (r = 0.31 and r = 0.40, respectively), L2-L4 BMD (r = 0.32 and r = 0.41, respectively), TB BMC (r = 0.42 and r = 0.49, respectively), and TB BMD (r = 0.48 and r = 0.54, respectively) were lower, although still significant (all P < 0.001). BUA seems to be the QUS parameter that best resembles the changes in BMC during growth.

Correlation of body growth and bone mineral density measured by ultrasound densitometry of the calcaneus in children and adolescents.

The assessment of growth, including the developmental change in bone mass, is crucial for child health care. We herein report normative values of bone mineral density (BMD) for calcaneus obtained from a large cross-section sample in Japanese school children. To investigate yearly physical growth from pre-school age to adulthood, we measured height, weight, body mass index (BMI), and BMD in 3,835 school children aged 3 to 18 (1,886 boys and 1,949 girls). Participating institutions included kindergarten, junior high schools, high schools, and a college of technology. The growth pattern (or velocity) of BMD (the ratio of trabecular bone area of the calcaneum) shows 3 phases according to the age rage: 3-10, 11-15, and 16-18 years for boys, and 3-7, 8-15, and 16-18 years for girls, both peaking at age 16 years. Likewise, that of weight shows 3 phases: 3-4, 5-15 and 16-18 years for boys, and 3-4, 5-14 and 15-18 years for girls, while the growth pattern of height shows 2 phases: 3-15 and 16-18 years for boys, and 3-13 and 14-18 years for girls, both sexes peaking at approximately 16 years. Therefore, the physical growth pattern of the school children shows progressive growth until 16 years, at which time growth is generally completed. In children under 16 years old, BMD of the calcaneus is higher in girls than in boys. Boys and girls show a similar growth pattern in body height and weight before peak development; however, the physical growth of boys eventually exceeds that of girls.

Knockout of hyaluronan synthase 1, but not 3, impairs formation of the retrocalcaneal bursa.

Hyaluronan (HA), a high molecular weight non-sulfated glycosaminoglycan, is an integral component of the extracellular matrix of developing and mature connective tissues including tendon. There are few published reports quantifying HA content during tendon growth and maturation, or detailing its effects on the mechanical properties of the tendon extracellular matrix. Therefore, the goal of the current study was to examine the role of HA synthesis during post-natal skeletal growth and maturation, and its influence on tendon structure and biomechanical function. For this purpose, the morphological, biochemical, and mechanical properties of Achilles tendons from wild type (WT) and hyaluronan synthase 1 and 3 deficient mouse strains (Has1-/- (Has1KO), Has3-/- (Has3KO), and Has1-/- 3-/- (Has1/3KO)) were determined at 4, 8, and 12 weeks of age. Overall, HAS-deficient mice did not show any marked differences from WT mice in Achilles tendon morphology or in the HA and chondroitin/dermatan sulfate (CS/DS) contents. However, HAS1-deficiency (in the single or Has1/3 double KO) impeded post-natal formation of the retrocalcaneal bursa, implicating HAS1 in regulating HA metabolism by cells lining the bursal cavity. Together, these data suggest that HA metabolism via HAS1 and HAS3 does not markedly influence the extracellular matrix structure or function of the tendon body, but plays a role in the formation/maintenance of peritendinous bursa. Additional studies are warranted to elucidate the relationship of HA and CS/DS metabolism to tendon healing and repair in vivo. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2622-2632, 2018.

Are distributions of secondary osteon variants useful for interpreting load history in mammalian bones?

BACKGROUND/AIMS: In cortical bone, basic multicellular units (BMUs) produce secondary osteons that mediate adaptations, including variations in their population densities and cross-sectional areas. Additional important BMU-related adaptations might include atypical secondary osteon morphologies (zoned, connected, drifting, elongated, multiple canal). These variants often reflect osteonal branching that enhances toughness by increasing interfacial (cement line) complexity. If these characteristics correlate with strain mode/magnitude-related parameters of habitual loading, then BMUs might produce adaptive differences in unexpected ways. METHODS: We carried out examinations in bones loaded in habitual torsion (horse metacarpals) or bending: sheep, deer, elk, and horse calcanei, and horse radii. Atypical osteons were quantified in backscattered images from anterior, posterior, medial, and lateral cortices. Correlations were determined between atypical osteon densities, densities of all secondary osteons, and associations with habitual strain mode/magnitude or transcortical location. RESULTS: Osteon variants were not consistently associated with 'tension', 'compression', or neutral axis ('shear') regions, even when considering densities or all secondary osteons, or only osteon variants associated with relatively increased interfacial complexity. Similarly, marrow- and strain-magnitude-related associations were not consistent. CONCLUSION: These data do not support the hypothesis that spatial variations in these osteon variants are useful for inferring a habitual bending or torsional load strain history.

Pediatric reference data for bone mineral density in the calcaneus for healthy children 2, 4, and 7 years of age by dual-energy x-ray absorptiometry and laser.

Dual-energy X-ray absorptiometry and laser (DXL) Calscan measures bone mineral density (BMD) in the calcaneus. In the present study, the DXL Calscan device has been modified for use in pediatric practice. It includes a function for measuring calcaneal height, which makes it possible to calculate volumetric bone mineral apparent density (BMAD). The aims of the present study were to evaluate the method when used in children, to create pediatric reference values in healthy Swedish 2-, 4-, and 7-yr-old children for BMD, bone mineral content (BMC), and BMAD, and to study whether these parameters were related to auxological data. The method was well tolerated by all children. Intraindividual coefficients of variation for BMC and BMD decreased with increasing age. The mean BMD was 0.17+/-0.003 g/cm2 in 2-yr-old children, 0.22+/-0.003 g/cm2 in 4-yr-old children, and 0.30+/-0.005 g/cm2 in 7-yr-old children. This study provides normative data as percentile values for BMD, BMC, and BMAD in young children measured with DXL Calscan. BMD was significantly correlated with age (p<0.001), height (p=0.001), weight (p<0.001), and body mass index standard deviation score (p<0.001). Seven-year-old girls showed significantly higher BMD than boys.

Ultrasonography of the calcaneus in Sever's disease.

Severs disease (calcaneal apophysitis) is a self-limiting condition seen in physically active children. Although there is controversy about the radiographic appearance, some reports propose the importance of fragmentation of the secondary nucleus in the diagnosis of Severs disease. We studied secondary nucleus of the calcaneus with ultrasonography. Twenty-one symptomatic heels of 14 children were examined. All these heels showed fragmentation of the secondary nucleus on both conventional radiograph and sonography. Ultrasonographic examination also showed 2 retrocalcaneal bursitis. Our initial data showed that sonography may be valuable in the diagnosis of Severs disease.

The relationship of calcaneal apophyseal ossification and Sanders hand scores to the timing of peak height velocity in adolescents.

The accurate assessment of skeletal maturity is essential in the management of orthopaedic conditions in the growing child. In order to identify the time of peak height velocity (PHV) in adolescents, two systems for assessing skeletal maturity have been described recently; the calcaneal apophyseal ossification method and the Sanders hand scores. The purpose of this study was to compare these methods in assessing skeletal maturity relative to PHV. We studied the radiographs of a historical group of 94 healthy children (49 females and 45 males), who had been followed longitudinally between the ages of three and 18 years with serial radiographs and physical examination. Radiographs of the foot and hand were undertaken in these children at least annually between the ages of ten and 15 years. We reviewed 738 radiographs of the foot and 694 radiographs of the hand. PHV was calculated from measurements of height taken at the time of the radiographs. Prior to PHV we observed four of six stages of calcaneal apophyseal ossification and two of eight Sanders stages. Calcaneal stage 3 and Sanders stage 2 was seen to occur about 0.9 years before PHV, while calcaneal stage 4 and Sanders stage 3 occurred approximately 0.5 years after PHV. The stages of the calcaneal and Sanders systems can be used in combination, offering better assessment of skeletal maturity with respect to PHV than either system alone.

Changes in the expression of type-X collagen in the fibrocartilage of rat Achilles tendon attachment during development.

This study histologically and immunohistochemically demonstrated developmental changes in cell morphology and expression of type-X collagen in the attachment of the Achilles tendon to the calcaneus in the rat. Although the site of attachment in the mature rat showed a well organized, direct insertion that was composed of tendon, fibrocartilage, calcified fibrocartilage, and bone, this four-zone structure was not observed in the immature 1-week-old rat. Formation of fibrocartilage was observed at 2 weeks, together with the hypertrophy of chondrocytes and the appearance of the secondary center of ossification. Type-X collagen was not detected either in chondrocytes in the attachment area at 1 week or in hypertrophic chondrocytes at the attachment at 2 weeks. In the 3-week-old rat, the secondary center of ossification extended to the area of attachment and type-X collagen was detected both in cartilage spicules within the secondary center of ossification and in cells found at the attachment adjacent to the secondary center of ossification. A four-zone structure had been established by 6 weeks and remained through 20 weeks. After 6 weeks, type-X collagen was identified both in the attachment of the tendon and beneath the calcaneal fibrocartilage. Type-X collagen is produced by cells in transitional zones between calcified and noncalcified tissue, such as the interface between articular cartilage and subchondral bone. In these areas, the expression of this protein persists through maturity and is not transient.

Relationships of loading history and structural and material characteristics of bone: development of the mule deer calcaneus.

If a bone's morphologic organization exhibits the accumulated effects of its strain history, then the relative contributions of a given strain stimulus to a bone's development may be inferred from a bone's hierarchical organization. The artiodactyl calcaneus is a short cantilever, loaded habitually in bending, with prevalent compression in the cranial (Cr) cortex, tension in the caudal (Cd) cortex, and shear in the medial and lateral cortices (i.e., neutral axis). Artiodactyl calcanei demonstrate unusually heterogeneous structural and material organization between these cortices. This study examines potential relationships between developmental morphologic variations and the functional strain distribution of the deer calcaneus. One calcaneus was obtained from each of 36 (fetus to adult) wild deer. Predominant collagen fiber orientation (CFO), microstructural characteristics, mineral content (% ash), and geometric parameters were determined from transversely cut segments. Radiographs were examined for arched trabeculae, which may reflect tension/compression stress trajectories. Results showed that cross-sectional shape changes with age from quasi-circular to quasi-elliptical, with the long axis in the cranial-caudal direction of habitual bending. Cranial ("compression") cortical thickness increased at a greater rate than the Cd ("tension") cortex. Fetal bones exhibited arched trabeculae. Percent ash was not uniform (Cr > Cd), and this disparity increased with age (absolute differences: 2.5% fetuses, 4.3% adults). Subadult bones showed progressively more secondary osteons and osteocyte lacunae in the Cr cortex, but the Cd cortex tended to have more active remodeling in the subadult and adult bones. Nonuniform Cr:Cd CFO patterns first consistently appear in the subadults, and are correlated with secondary bone formation and habitual strain mode. Medial and lateral cortices in these groups exhibited elongated secondary osteons. These variations may represent "strain-mode-specific" (i.e., tension, compression, shear) adaptations. The heterogeneous organization may also be influenced by variations in longitudinal strain magnitude (highest in the Cr cortex) and principal strain direction-oblique in medial-lateral cortices (where shear strains also predominate). Other factors such as local reductions in longitudinal strain may influence the increased remodeling activity of the Cd cortex. Some structural variations, such as arched trabeculae, that are established early in ontogeny may be strongly influenced by genetic- or epigenetic-derived processes. Material variations, such as secondary osteon population densities and CFO, which appear later, may be products of extragenetic factors, including microdamage.

A prospective study of quantitative ultrasound in children and adolescents.

The accrual of optimal bone mass during childhood and adolescence is essential for the formation of a skeleton that will meet structural needs throughout life. Assessing bone health of children is becoming increasingly important in order to identify those who require interventions, and quantitative ultrasound (QUS) has appeal for these assessments. The purpose of this prospective study was to characterize changes in QUS values in 328 healthy children and adolescents over a 3-yr period. Measurements of QUS, height, weight, nutrient intake, fracture history, and Tanner stage were made at baseline and 3 yr later. Both females and males experienced significant increases in QUS values during the study. The rate of change of QUS peaked at an earlier age in females than in males, and maximum accumulation rates in both genders occurred at ages at which highest accumulation rates are seen with densitometry. Females exhibited higher QUS values than males during puberty, also similar to results for dual X-ray absorptiometry (DXA). This is the first report of prospective data of QUS in children and adolescents. Our findings that QUS values change during childhood and adolescence in a manner similar to DXA values, the "gold standard," provide support for the validity of using QUS to assess bone health in children and adolescents.