Structural and cellular changes during bone growth in healthy children

Trabecular bone variation in the gorilla calcaneus

OBJECTIVES

Calcaneal external shape differs among nonhuman primates relative to locomotion. Such relationships between whole-bone calcaneal trabecular structure and locomotion, however, have yet to be studied. Here we analyze calcaneal trabecular architecture in Gorilla gorilla gorilla, Gorilla beringei beringei, and G. b. graueri to investigate general trends and fine-grained differences among gorilla taxa relative to locomotion.

MATERIALS AND METHODS

Calcanei were micro-CT scanned. A three-dimensional geometric morphometric sliding semilandmark analysis was carried out and the final landmark configurations used to position 156 volumes of interest. Trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), and bone volume fraction (BV/TV) were calculated using the BoneJ plugin for ImageJ and MATLAB. Non-parametric MANOVAs were run to test for significant differences among taxa in parameter raw values and z-scores. Parameter distributions were visualized using color maps and summarized using principal components analysis.

RESULTS

There are no significant differences in raw BV/TV or Tb.Th among gorillas, however G. b. beringei significantly differs in z-scores for both parameters (p = <0.0271). All three taxa exhibit relatively lower BV/TV and Tb.Th in the posterior half of the calcaneus. This gradation is exacerbated in G. b. beringei. G. b. graueri significantly differs from other taxa in Tb.Sp z-scores (p < 0.001) indicating a different spacing distribution.

DISCUSSION

Relatively higher Tb.Th and BV/TV in the anterior calcaneus among gorillas likely reflects higher forces associated with body mass (transmitted through the subtalar joint) relative to forces transferred through the posterior calcaneus. The different Tb.Sp pattern in G. b. graueri may reflect proposed differences in foot positioning during locomotion.

Investigating the causal relationship between thyroid dysfunction diseases and osteoporosis: a two-sample Mendelian randomization analysis

The prevalence of thyroid dysfunction diseases (TDFDs) and osteoporosis (OP) is high. Previous studies have indicated a potential association between TDFDs and OP, yet the causal direction remains unclear. This study aimed to investigate the potential causal relationship between TDFDs and the risk of developing OP and related fractures. We obtained pooled data from genome-wide association studies (GWASs) conducted on TDFDs and OP in European populations and identified single-nucleotide polymorphisms (SNPs) with genome-wide significance levels associated with exposure to TDFDs as instrumental variables. Inverse variance weighted (IVW) was employed as the primary method for Mendelian randomization (MR) analysis, supplemented by MR‒Egger, weighted median, simple mode and weighted mode methods. Sensitivity analyses were conducted to evaluate the robustness of the findings. The IVW method demonstrated an increased risk of OP in patients with TDFDs, including hyperthyroidism and hypothyroidism (TDFDs: OR = 1.11; 95% CI 1.09, 1.13; hypothyroidism: OR = 1.14; 95% CI 1.10, 1.17; hyperthyroidism: OR = 1.09; 95% CI 1.06, 1.12). These findings were supported by supplementary analysis, which revealed a positive correlation between TDFDs and the risk of OP. Multiple sensitivity analyses confirmed the absence of horizontal pleiotropy in the study, thus indicating the robustness of our results. The causal relationship between TDFDs and increased risk of OP implies the need for early bone mineral density (BMD) screening and proactive prevention and treatment strategies for individuals with TDFDs.

Mandibular Cortical Bone Evaluation in a Healthy Paediatric Population

BACKGROUND

Changes in mandibular cortical bone have been documented in children with chronic diseases but not in healthy populations.

AIM

We aimed to qualitatively and quantitatively evaluate the mandibular cortical bone of a healthy paediatric population using dental panoramic radiographs (DPTs). The secondary objective was to assess the effect of dental status on cortical bone.

DESIGN

The DPTs of 660 individuals, aged 6-18 years, were evaluated by two blinded examiners. Bone was qualitatively categorized according to the Mandibular Cortical Index (MCI), and its width was calculated using the Mandibular Cortical Width Index (MCW). Differences between gender and age were tested using Fisher's exact and correlation with dental status with the chi-square test.

RESULTS

A significant correlation was observed between bone morphology and gender, with girls having more frequent even and sharp endosteal margins than boys, who showed semilunar defects. The degree of erosion increased with age, as did bone thickness. A positive correlation between thickness and type of dentition was recorded, with normal bone predominating in children in the mixed dentition stage. Νο correlation was found between bone morphology or thickness and the factors associated with dental status.

CONCLUSIONS

Bone quality and quantity vary significantly between different genders and age groups. Dental needs and treatment characteristics did not seem to affect the above parameters.

Bone Material Properties in Bone Diseases Affecting Children

PURPOSE OF REVIEW

Metabolic and genetic bone disorders affect not only bone mass but often also the bone material, including degree of mineralization, matrix organization, and lacunar porosity. The quality of juvenile bone is moreover highly influenced by skeletal growth. This review aims to provide a compact summary of the present knowledge on the complex interplay between bone modeling and remodeling during skeletal growth and to alert the reader to the complexity of bone tissue characteristics in children with bone disorders.

RECENT FINDINGS

We describe cellular events together with the characteristics of the different tissues and organic matrix organization (cartilage, woven and lamellar bone) occurring during linear growth. Subsequently, we present typical alterations thereof in disorders leading to over-mineralized bone matrix compared to those associated with low or normal mineral content based on bone biopsy studies. Growth spurts or growth retardation might amplify or mask disease-related alterations in bone material, which makes the interpretation of bone tissue findings in children complex and challenging.

Combination of osteogenesis imperfecta and hypophosphatasia in three children with multiple fractures, low bone mass and severe osteomalacia, a challenge for therapeutic management

Osteogenesis imperfecta (OI) and hypophosphatasia (HPP) are rare skeletal disorders caused by mutations in the genes encoding collagen type I (COL1A, COL1A2) and tissue-non-specific isoenzyme of alkaline phosphatase (ALPL), respectively. Both conditions result in skeletal deformities and bone fragility although bone tissue abnormalities differ considerably. Children with OI have low bone mass and hypermineralized matrix, whereas HPP children develop rickets and osteomalacia. We report a family, father and three children, affected with growth retardation, low bone mass and recurrent fractures. None of them had rickets, blue sclera or dentinogenesis imperfecta. ALP serum levels were low and genetics revealed in the four probands heterozygous pathogenic mutations in COL1A2 c.838G > A (p.Gly280Ser) and in ALPL c.1333T > C (p.Ser445Pro). After multidisciplinary meeting, a diagnostic transiliac bone biopsy was indicated for each sibling for therapeutic decision. Bone histology and histomorphometry, as compared to reference values of children with OI type I as well as, to a control pediatric patient harboring the same COL1A2 mutation, revealed similarly decreased trabecular bone volume, increased osteocyte lacunae, but additionally severe osteomalacia. Quantitative backscattered electron imaging demonstrated that bone matrix mineralization was not as decreased as expected for osteomalacia. In summary, we observed within each biopsy samples classical features of OI and classical features of HPP. The apparent nearly normal bone mineralization density distribution results presumably from divergent effects of OI and HPP on matrix mineralization. A combination therapy was initiated with ALP enzyme-replacement and one month later with bisphosphonates. The ongoing treatment led to improved skeletal growth, increased BMD and markedly reduced fracture incidence.

Comparison of bone microstructure and strength in the distal radius and tibia between the different types of primary hypertrophic osteoarthropathy: an HR-pQCT study

Primary hypertrophic osteoarthropathy (PHO) is a hereditary bone disease that is grouped into PHO autosomal recessive 1 (PHOAR1) and PHO autosomal recessive 2 (PHOAR2) due to different causative genes. Data comparing bone microstructure between the two subtypes are scarce. This is the first study to find that PHOAR1 patients had inferior bone microstructure compared with PHOAR2 patients.

PURPOSE

The primary goal of this study was to assess bone microarchitecture and strength in PHOAR1 and PHOAR2 patients and to compare them with age- and sex-matched healthy controls (HCs). The secondary goal was to assess the differences between PHOAR1 and PHOAR2 patients.

METHODS

Twenty-seven male Chinese PHO patients (PHOAR1 = 7; PHOAR2 = 20) were recruited from Peking Union Medical College Hospital. The areal bone mineral density (aBMD) was assessed by dual-energy X-ray absorptiometry (DXA). Peripheral bone microarchitecture at the distal radius and tibia were evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT). Biochemical markers of PGE2, bone turnover, and Dickkopf-1 (DKK1) were investigated.

RESULTS

Compared with HCs, PHOAR1 and PHOAR2 patients had distinctively larger bone geometry, substantially lower vBMD at the radius and tibia, and compromised cortical microstructure at the radius. For trabecular bone, PHOAR1 and PHOAR2 patients showed different changes at the tibia. PHOAR1 patients had significant deficits in the trabecular compartment, resulting in lower estimated bone strength. Conversely, PHOAR2 patients showed a higher trabecular number, narrower trabecular separation, and lower trabecular network inhomogeneity than HCs, translating into preserved or slightly high estimated bone strength.

CONCLUSION

PHOAR1 patients had inferior bone microstructure and strength compared with PHOAR2 patients and HCs. Additionally, this study was the first to find differences in the bone microstructure between PHOAR1 and PHOAR2 patients.

Bone Turnover Markers in Children: From Laboratory Challenges to Clinical Interpretation

Bone turnover markers (BTMs) have been developed many years ago to study, in combination with imaging techniques, bone remodeling in adults. In children and adolescents, bone metabolism differs from adults since it implies both growth and bone remodeling, suggesting an age- and gender-dependent BTM concentration. Therefore, specific studies have evaluated BTMs in not only physiological but also pathological conditions. However, in pediatrics, the use of BTMs in clinical practice is still limited due to these many children-related specificities. This review will discuss about physiological levels of BTMs as well as their modifications under pathological conditions in children and adolescents. A focus is also given on analytical and clinical challenges that restrain BTM usefulness in pediatrics.

Bone Turnover Markers: Basic Biology to Clinical Applications

Bone turnover markers (BTMs) are used widely, in both research and clinical practice. In the last 20 years, much experience has been gained in measurement and interpretation of these markers, which include commonly used bone formation markers bone alkaline phosphatase, osteocalcin, and procollagen I N-propeptide; and commonly used resorption markers serum C-telopeptides of type I collagen, urinary N-telopeptides of type I collagen and tartrate resistant acid phosphatase type 5b. BTMs are usually measured by enzyme-linked immunosorbent assay or automated immunoassay. Sources contributing to BTM variability include uncontrollable components (e.g., age, gender, ethnicity) and controllable components, particularly relating to collection conditions (e.g., fasting/feeding state, and timing relative to circadian rhythms, menstrual cycling, and exercise). Pregnancy, season, drugs, and recent fracture(s) can also affect BTMs. BTMs correlate with other methods of assessing bone turnover, such as bone biopsies and radiotracer kinetics; and can usefully contribute to diagnosis and management of several diseases such as osteoporosis, osteomalacia, Paget's disease, fibrous dysplasia, hypophosphatasia, primary hyperparathyroidism, and chronic kidney disease-mineral bone disorder.

SMAD3 mutation in LDS3 causes bone fragility by impairing the TGF-β pathway and enhancing osteoclastogenesis

Loss-of-function mutations in SMAD3 cause Loeys-Dietz syndrome type 3 (LDS3), a rare autosomal-dominant connective tissue disorder characterized by vascular pathology and skeletal abnormalities. Dysregulation of TGF-β/SMAD signaling is associated with abnormal skeletal features and bone fragility. To date, histomorphometric and ultrastructural characteristics of bone with SMAD3 mutations have not been reported in humans and the exact mechanism by which SMAD3 mutations cause the LDS3 phenotype is poorly understood. Here, we investigated bone histomorphometry and matrix mineralization in human bone with a SMAD3 mutation and explored the associated cellular defect in the TGF-β/SMAD pathway in vitro. The index patient had recurrent fractures, mild facial dysmorphism, arachnodactyly, pectus excavatum, chest asymmetry and kyphoscoliosis. Bone histomorphometry revealed markedly reduced cortical thickness (−68 %), trabecular thickness (−32 %), bone formation rate (−50 %) and delayed mineralization. Quantitative backscattered electron imaging demonstrated undermineralized bone matrix with increased heterogeneity in mineralization. The patient's SMAD3 mutation (c.200 T > G; p.I67S), when expressed from plasmid vectors in HEK293 cells, showed reduced phosphorylation and transcription factor activity compared to normal control and SMAD3 (p.S264Y), a gain-of-function mutation, somatic mosaicism of which causes melorheostosis. Transfection study of the patients' SMAD3 (p.I67S) mutation displayed lower luciferase reporter activity than normal SMAD3 and reduced expression of TGF-β signaling target genes. Patient fibroblasts also demonstrated impaired SMAD3 protein stability. Osteoclastogenic differentiation significantly increased and osteoclast-associated genes, including ACP5 (encoding TRAP), ATP6V0D2, and DCSTAMP, were up-regulated in CD14 (+) peripheral blood mononuclear cells (PBMCs) with the SMAD3 (p.I67S) mutation. Upregulation of osteoclastogenic genes was associated with decreased expression of TGF-β signaling target genes. We conclude that bone with the SMAD3 (p.I67S) mutation features reduced bone formation, and our functional studies revealed decreased SMAD3 activation and protein stability as well as increased osteoclastogenesis. These findings enhance our understanding of the pathophysiology of LDS3 caused by SMAD3 mutations. Emerging therapies targeting in the TGF-β/SMAD pathway also raise hope for treatment of LDS3.

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Increased bone fragility

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Low bone matrix mineralization

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SMAD3 (p.I67S) decreased TGF-b signaling and SMAD3 activity.

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SMAD3 (p.I67S) reduced SMAD3 protein stability.

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SMAD3 (p.I67S) mediated osteoclastogenesis.

Cortical bone material / compositional properties in growing children and young adults aged 1.5-23 years, as a function of gender, age, metabolic activity, and growth spurt

Bone material / compositional properties are significant determinants of bone quality, thus strength. Raman spectroscopic analysis provides information on the quantity and quality of all three bone tissue components (mineral, organic matrix, and tissue water). The overwhelming majority of the published reports on the subject concern adults. We have previously reported on these properties in growing children and young adults, in the cancellous compartment. The purpose of the present study was to create normative reference data of bone material / compositional properties for children and young adults, in the cortical compartment. We performed Raman (Senterra (Bruker Optik GmbH), 50× objective, with an excitation of 785 nm (100 mW) and a lateral resolution of ~0.6 μm) microspectroscopic analysis of transiliac bone samples from 54 individuals between 1.5 and 23 years of age, with no known metabolic bone disease, and which have been previously used to establish histomorphometric, bone mineralization density distribution, and cancellous bone quality reference values. The bone quality indices that were determined were: mineral/matrix ratio (MM) from the integrated areas of the v₂PO₄ (410-460 cm^-1) and the amide III (1215-1300 cm^-1) bands, tissue water in nanopores approximated by the ratio of the integrated spectral area ~ 494-509 cm^-1 to Amide III band, the glycosaminoglycan (GAG) content (ratio of integrated area 1365-1390 cm^-1 to the Amide III band, the sulfated proteoglycan (sPG) content as the ratio of the integrated peaks ~1062 cm^-1 and 1365-1390 cm^-1, the pyridinoline (Pyd) content estimated from the ratio of the absorbance height at 1660 cm^-1 / area of the amide I (1620-1700 cm^-1) band, and the mineral maturity / crystallinity (MMC) estimated from the inverse of the full width at half height of the v₁PO₄ (930-980 cm^-1) band. Analyses were performed at the three distinct cortical surfaces (endosteal, osteonal, periosteal) at specific anatomical microlocations, namely the osteoid, and the three precisely known tissue ages based on the presence of fluorescence double labels. Measurements were also taken in interstitial bone, a much older tissue that has undergone extensive secondary mineralization. Overall, significant dependencies of the measured parameters on tissue age were observed, while at any given tissue age, sex and subject age were minimal confounders. The established Raman database in the cortical compartments complements the previously published one in cancellous bone, and provides healthy baseline bone quality indices that may serve as a valuable tool to identify alterations due to pediatric disease.

Pamidronate Therapy Increases Trabecular Bone Complexity of Mandibular Condyles in Individuals with Osteogenesis Imperfecta

Patients with Osteogenesis Imperfecta (OI) present extra-skeletal manifestations, including important orodental and craniofacial features as dentinogenesis imperfecta, dental agenesis, failure of maxilla growth and hypotonia of masticatory muscles. These features may compromise vital functions speech and mastication. Studies have demonstrated that cyclic pamidronate infusion, the standard therapy for patients with moderate to severe OI, influences the histomorphometric pattern of different body bones. The present study aimed to investigate the condyle trabecular bone pattern in OI patients. We used fractal dimension (FD) analysis on dental panoramic radiographic images to characterize the mandibular condyle trabecular bone in adolescents diagnosed with OI and treated with pamidronate. Imaging exam of 33 adolescents of both sexes, aged between 12 and 17 years, were analyzed and compared with 99 age- and sex-matched healthy adolescents. FD in patients was significantly lower (1.23 ± 0.15) than in healthy controls (1.29 ± 0.11; p < 0.01). Type of OI, age at treatment onset, and the duration of therapy were variables that showed a statistically significant effect on the FD results. This study demonstrated that the bone architecture of mandibular condyles may be altered in pediatric patients with moderate and severe forms of OI. Also, pamidronate treatment seems to have a positive effect on condyle trabecular bone in these patients. This is supported by our finding that FD values were positively influenced by the length of cyclic pamidronate treatment at the time of imaging, as well as by the age of the individual at treatment onset.

Growth and development of trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata) reflects locomotor behavior, life history, and neuromuscular development

Bone structure dynamically adapts to its mechanical environment throughout ontogeny by altering the structure of trabecular bone, the three-dimensional mesh-like structure found underneath joint surfaces. Trabecular structure, then, can provide a record of variation in loading directions and magnitude; and in ontogenetic samples, it can potentially be used to track developmental shifts in limb posture. We aim to broaden the analysis of trabecular bone ontogeny by incorporating interactions between ontogenetic variation in locomotor repertoire, neuromuscular maturation, and life history. We examine the associations between these variables and age-related variation in trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata). We used high-resolution micro-computed tomography scanning to image the calcaneus in a cross-sectional sample of 34 juvenile M. fuscata aged between 0 and 7 years old at the Primate Research Institute, Japan. We calculated whole bone averages of standard trabecular properties and generated whole-bone morphometric maps of bone volume fraction and Young's modulus. Trabecular structure becomes increasingly heterogeneous in older individuals. Bone volume fraction (BV/total volume [TV]) decreases during the first month of life and increases afterward, coinciding with the onset of independent locomotion in M. fuscata. At birth, primary Young's modulus is oriented orthogonal to the ossification center, but after locomotor onset bone structure becomes stiffest in the direction of joint surfaces and muscle attachments. Age-related variation in bone volume fraction is best predicted by an interaction between the estimated percentage of adult brain size, body mass, and locomotor onset. To explain our findings, we propose a model where interactions between age-related increases in body weight and maturation of the neuromuscular system alter the loading environment of the calcaneus, to which the internal trabecular structure dynamically adapts. This model cannot be directly tested based on our cross-sectional data. However, confirmation of the model by longitudinal experiments and in multiple species would show that trabecular structure can be used both to infer behavior from fossil morphology and serve as a valuable proxy for neuromuscular maturation and life history events like locomotor onset and the achievement of an adult-like gait. This approach could significantly expand our knowledge of the biology and behavior of fossil species.

The effect of denosumab and alendronate on trabecular plate and rod microstructure at the distal tibia and radius: A post-hoc HR-pQCT study

BACKGROUND

Age-related trabecular microstructural deterioration and conversion from plate-like trabeculae to rod-like trabeculae occur because of unbalanced rapid remodeling. As denosumab achieves greater remodeling suppression and lower cortical porosity than alendronate, we hypothesized that denosumab might also preserve trabecular plate microstructure, bone stiffness and strength more effectively than alendronate.

METHODS

In this post hoc analysis of a phase 2 study, postmenopausal women randomized to placebo (P, n = 74), denosumab (D, n = 72), or alendronate (A, n = 68). HR-pQCT scans of the distal radius and tibia were performed at baseline and Month-12 (M12). Trabecular compartment was subjected to Individual Trabecula Segmentation while finite element analysis was performed to estimate stiffness and strength. Percent change from baseline at M12 of each parameter was compared between patient groups.

RESULTS

At the distal tibia, in the placebo group, plate surface area (pTb.S, -1.3%) decreased while rod bone volume fraction (rBV/TV, +4.5%) and number (rTb.N, +2.1%) increased. These changes were prevented by denosumab but persisted despite alendronate therapy (pTb.S: -1.7%; rBV/TV: +6.9%; rTb.N: +3.0%). Both treatments improved whole bone stiffness (D: +3.1%; A: +1.8%) and failure load (D: +3.0%; A: +2.2%); improvements using denosumab was significant compared to placebo (stiffness: p = 0.004; failure load: p = 0.003). At the distal radius, denosumab increased total trabecular bone volume fraction (BV/TV, +3.4%) and whole bone failure load (+4.0%), significantly different from placebo (BV/TV: p = 0.044; failure load: p = 0.046). Significantly different effects of either drug on plate and rod microstructure were not detected.

CONCLUSIONS

Denosumab preserved trabecular plate microstructure. Alendronate did not. However, estimated strength did not differ between denosumab and alendronate treated groups.

Clinical Phenotype and Bone Biopsy Characteristics in a Child with Proteus Syndrome

Proteus syndrome is a rare genetic disorder, which is characterized by progressive, segmental, or patchy overgrowth of diverse tissues of all germ layers, including the skeleton. Here, we present a 9-year-old girl with a somatic-activating mutation (c.49G > A; p.Glu17Lys) in AKT1 gene in a mosaic status typical for Proteus syndrome. She presented with hemihypertrophy of the right lower limb and a "moccasin" lesion among others. A transiliac bone biopsy was analyzed for bone histology/histomorphometry as well as bone mineralization density distribution (BMDD) and osteocyte lacunae sections (OLS) characteristics based on quantitative backscattered electron imaging. Bone histomorphometry revealed highly increased mineralizing surface (Z-score + 2.3) and mineral apposition rate (Z-score + 19.3), no osteoclasts (Z-score - 2.1), and an increased amount of primary bone in the external cortex. BMDD abnormalities included a decreased mode calcium concentration in cancellous bone (Z-score - 1.7) and an increased percentage of highly mineralized cortical bone area (Z-score + 2.4) compared to reference. OLS characteristics showed several differences compared to reference data; among them, there were the highly increased OLS-porosity, OLS-area, and OLS-perimeter on the external cortex (Z-scores + 6.8, + 4.4 and 5.4, respectively). Our findings suggest that increased bone formation reduced matrix mineralization in cancellous bone while the enhanced amount of primary bone in the external cortex increased the portion of highly mineralized cortical bone and caused OLS-characteristics abnormalities. Our results indicate further that remodeling of primary bone might be disturbed or delayed in agreement with the decreased number of osteoclasts observed in this child with Proteus syndrome.

From Neural Command to Robotic Use: The Role of Symmetry/Asymmetry in Postural and Locomotor Activities

This article deepens a reflection on why and how symmetry/asymmetry affects the motor and postural behavior from the neural source, uterine development, child maturation, and how the notion of symmetry/asymmetry has been applied to walking robot design and control. The concepts of morphology and tensegrity are also presented to illustrate how the biological structures have been used in both sciences and arts. The development of the brain and the neuro-fascia-musculoskeletal system seems to be quite symmetric from the beginning of life through to complete maturity. The neural sources of movements (i.e., central pattern generators) are able to produce both symmetric or asymmetric responses to accommodate to environmental constraints and task requirements. Despite the fact that the human development is mainly symmetric, asymmetries already regulate neurological and physiological development. Laterality and sports training could affect natural musculoskeletal symmetry. The plasticity and flexibility of the nervous system allows the abilities to adapt and compensate for environmental constraints and musculoskeletal asymmetries in order to optimize the postural and movement control. For designing humanoid walking robots, symmetry approaches have been mainly used to reduce the complexity of the online calculation. Applications in neurological retraining and rehabilitation should also be considered.

Mathematical modeling of the role of bone turnover in pH regulation in bone interstitial fluid

BACKGROUND AND AIMS

Bone turnover is strongly affected by pH of surrounding fluid, and in turn plays a role in maintaining systemic pH, however the quantitative contribution of bone processes to pH regulation is not known. Our goal was to develop a mathematical model describing pH regulation in the interstitial fluid and to examine the contribution of hydroxyapatite dissolution and precipitation to pH regulation.

MATERIALS AND METHODS

We modeled twelve reversible equilibrium reactions of sixteen calcium, phosphate, hydrogen and carbonate species in the interstitial fluid and examined the buffering capacity and range. The effect of hydroxyapatite dissolution and precipitation was modeled by assuming that the calcium, phosphate and hydroxide contained in the bone volume adjacent to the interstitial fluid is instantaneously added to or removed from the interstitial fluid.

RESULTS

The carbonate buffer was found to dominate electrochemical buffering system of the bone interstitial fluid. Nevertheless, the phosphate added during dissolution of bone hydroxyapatite significantly improved the interstitial fluid buffering capacity. In contrast, hydroxyapatite precipitation had limited effect on the interstitial fluid pH regulation.

CONCLUSION

This study provides mechanistic insights into the physicochemical processes underlying the known role of bone turnover processes in regulation of body pH homeostasis.

Bone material properties and response to teriparatide in osteoporosis due to WNT1 and PLS3 mutations

CONTEXT

Patients with osteoporosis-associated WNT1 or PLS3 mutations have unique bone histomorphometric features and osteocyte-specific hormone expression patterns.

OBJECTIVE

To investigate the effects of WNT1 and PLS3 mutations on bone material properties.

DESIGN

Transiliac bone biopsies were evaluated by quantitative backscattered electron imaging, immunohistochemistry, and bone histomorphometry.

SETTING

Ambulatory patients.

PATIENTS

Three pediatric and eight adult patients with WNT1 or PLS3 mutations.

INTERVENTION

Bone mineralization density distribution and osteocyte protein expression was evaluated in 11 patients and repeated in six patients who underwent repeat biopsy after 24 months of teriparatide treatment.

MAIN OUTCOME MEASURE

Bone mineralization density distribution and protein expression.

RESULTS

Children with WNT1 or PLS3 mutations had heterogeneous bone matrix mineralization, consistent with bone modeling during growth. Bone matrix mineralization was homogenous in adults and increased throughout the age spectrum. Teriparatide had very little effect on matrix mineralization or bone formation in patients with WNT1 or PLS3 mutations. However, teriparatide decreased trabecular osteocyte lacunae size and increased trabecular bone FGF23 expression.

CONCLUSION

The contrast between preserved bone formation with heterogeneous mineralization in children and low bone turnover with homogenous bone mineral content in adults suggests that WNT1 and PLS3 have differential effects on bone modeling and remodeling. The lack of change in matrix mineralization in response to teriparatide, despite clear changes in osteocyte lacunae size and protein expression, suggests that altered WNT1 and PLS3 expression may interfere with coupling of osteocyte, osteoblast, and osteoclast function. Further studies are warranted to determine the mechanism of these changes.

Increased Osteocyte Lacunae Density in the Hypermineralized Bone Matrix of Children with Osteogenesis Imperfecta Type I

Osteocytes are terminally differentiated osteoblasts embedded within the bone matrix and key orchestrators of bone metabolism. However, they are generally not characterized by conventional bone histomorphometry because of their location and the limited resolution of light microscopy. OI is characterized by disturbed bone homeostasis, matrix abnormalities and elevated bone matrix mineralization density. To gain further insights into osteocyte characteristics and bone metabolism in OI, we evaluated 2D osteocyte lacunae sections (OLS) based on quantitative backscattered electron imaging in transiliac bone biopsy samples from children with OI type I (n = 19) and age-matched controls (n = 24). The OLS characteristics were related to previously obtained, re-visited histomorphometric parameters. Moreover, we present pediatric bone mineralization density distribution reference data in OI type I (n = 19) and controls (n = 50) obtained with a field emission scanning electron microscope. Compared to controls, OI has highly increased OLS density in cortical and trabecular bone (+50.66%, +61.73%; both p < 0.001), whereas OLS area is slightly decreased in trabecular bone (−10.28%; p = 0.015). Correlation analyses show a low to moderate, positive association of OLS density with surface-based bone formation parameters and negative association with indices of osteoblast function. In conclusion, hyperosteocytosis of the hypermineralized OI bone matrix associates with abnormal bone cell metabolism and might further impact the mechanical competence of the bone tissue.

Early ontogeny of humeral trabecular bone in Neandertals and recent modern humans

Trabecular bone ontogeny is well known in modern humans and unknown in Neandertals. Yet the bone developmental pattern is useful for interpreting fossils from evolutionary and functional perspectives. Interestingly, microstructure in early ontogeny is supposedly not influenced by high and specific mechanical loading related to the lifestyle of a human group and consequently does not directly depend on the activities of hunter-gatherers. Here, we specifically explored the early growth trajectories of the trabecular bone structure of the humerus and emphasized in particular how bone fraction (bone volume/total volume [BV/TV]) was built up in Neandertals, given the specific modern human bone loss after birth and the use of BV/TV in functional studies. Six Neandertals and 26 recent modern humans ranging from perinates to adolescents were included in this study. Six trabecular parameters were measured within a cubic region of interest extracted from the proximal metaphysis of the humerus. We found that the microstructural changes in Neandertals during early ontogeny (<1 year) fit with modern human growth trajectories for each parameter. The specific bone loss occurring immediately after birth in modern humans also occurred in Neandertals (but not in chimpanzees). However, the early childhood fossil Ferrassie 6 presented unexpectedly high BV/TV, whereas the high BV/TV in the Crouzade I adolescent was predictable. These results suggest that Neandertals and modern humans shared predetermined early growth trajectories and developmental mechanisms. We assume that the close relationship between skeletal characteristics in early ontogeny and adults in modern humans also existed in Neandertals. However, it was difficult to ensure that the high BV/TV in Neandertal early childhood, represented by only one individual, was at the origin of the high BV/TV observed in adults. Consequently, our study does not challenge the mechanical hypothesis that explains the trabecular gracilization of the humerus during the Holocene.

Resect or Retain Bone Fragments in Children and Teenagers with Severe Open Fractures?: A Case Report

CASE

A 14-year-old pedestrian was hit by a car and encountered similar bilateral Gustilo IIIB open tibial fractures. The right tibial fracture involved a large borderline vital butterfly fragment without periosteal contact, which was retained and proceeded to sufficient healing within 12 weeks. The left tibial fracture was treated according to the principles for the treatment of severe open fractures in adults, involving resection of devitalized fragments and bone transport, and healed within 15 months.

CONCLUSIONS

Teenagers do possess larger bone healing potential than adults. Therefore, a rapid bone union can be achieved even with apparently devitalized bone fragments if sufficient soft-tissue closure and stable fracture fixation is established early in the treatment of open limb fractures.

The Characteristics of Adjacent Anatomy of Mandibular Third Molar Germs: A CBCT Pilot Study in Patients with Osteogenesis Imperfecta

(1) Objectives: The aim of our study was to investigate the anatomical features of lower third molar and its adjacent anatomical connections in type I Osteogenesis Imperfecta (OI) patients through cone beam computed tomography (cbct). (2) Methods: The study was conducted among 25 patients, 13 patients with type I OI and 12 control patients (individuals with no disorders and no treatment); average age was 15.44 ± 2.06, 23 third molar germs for each group. The germs have been compared to the parameters using the Mann-Whitney test. A chi-square test was also used to investigate the correlation between the status case/control and tooth development stage. (3) Results: Mann-Whitney test showed significant differences between cases and controls: diameter of the tooth germ in toto (U = 93.5; p < 0.001), tooth development stage, (U = 145; p < 0.01), roots length (U = 44.5; p < 0.01), cementoenamel junction diameter (U = 157.5; p < 0.05), size of the pulp chamber (U = 95.5; p < 0.05). Type I OI is not associated with the relationship between the germ of mandibular third molar and alveolar canal on axial plane (χ² = 4.095; p = 0.129), and parasagittal (χ² = 4.800; p = 0.091). The association between type I OI and relationship with the germ of mandibular third molar and alveolar canal on the coronal plane has been significant (χ² = 9.778; p < 0.05) as the perforation of the lingual cortical bone in the region of mandibular third molar tooth germ (χ² = 11.189; p < 0.01). (4) Conclusions: The results confirm the cbct accuracy in the evaluation of bone density in type I OI patients giving also the opportunity to study the tridimensional anatomy of germs and the adjacent anatomical structures in order to avoid any perioperative complications.

Hip Arthrography Complicated by Air Embolism in Infants: A Report of 2 Cases

CASE

We report 2 cases of infants with developmental dysplasia of the hip who underwent arthrography of the hip with use of air for structure identification, which resulted in a presumed air embolism and deep oxygen desaturation. This led to the hypothesis that there is an increased potential of air embolism in the pediatric population given the vascular anatomy of the hip.

CONCLUSION

These 2 cases document the important and not well-known complication of air embolism during air arthrography, which resulted in a change of practice for the authors. We strongly recommend against the use of air as an adjunct to routine arthrography in children.

Aging and menopause reprogram osteoclast precursors for aggressive bone resorption

Women gradually lose bone from the age of ~35 years, but around menopause, the rate of bone loss escalates due to increasing bone resorption and decreasing bone formation levels, rendering these individuals more prone to developing osteoporosis. The increased osteoclast activity has been linked to a reduced estrogen level and other hormonal changes. However, it is unclear whether intrinsic changes in osteoclast precursors around menopause can also explain the increased osteoclast activity. Therefore, we set up a protocol in which CD14+ blood monocytes were isolated from 49 female donors (40-66 years old). Cells were differentiated into osteoclasts, and data on differentiation and resorption activity were collected. Using multiple linear regression analyses combining in vitro and in vivo data, we found the following: (1) age and menopausal status correlate with aggressive osteoclastic bone resorption in vitro; (2) the type I procollagen N-terminal propeptide level in vivo inversely correlates with osteoclast resorption activity in vitro; (3) the protein level of mature cathepsin K in osteoclasts in vitro increases with age and menopause; and (4) the promoter of the gene encoding the dendritic cell-specific transmembrane protein is less methylated with age. We conclude that monocytes are "reprogrammed" in vivo, allowing them to "remember" age, the menopausal status, and the bone formation status in vitro, resulting in more aggressive osteoclasts. Our discovery suggests that this may be mediated through DNA methylation. We suggest that this may have clinical implications and could contribute to understanding individual differences in age- and menopause-induced bone loss.

Effect of anthropometry scaling on the response of the piper child scalable human body model subject to pelvic impact

The Open Source PIPER child scalable human body model was publicly released in April 2017 (www.piper-project.org) along with frontal and side impact validation conditions. The objective of this paper is to investigate the effect of anthropometry scaling on the response of the model in side pelvic impact. Three setups from two published studies were used: (1) a lateral drop test (2) a greater trochanter impact with a rigid pendulum (3) a pelvis side impact with a flat surface. The first study used scaling assumption developed for crash test dummy design (setups 1 and 2) and the second performed tests on post mortem human surrogates. The baseline 6 years old child model was scaled using a model morphing methodology to match the stature and weight of the surrogates used in the two published studies. Overall, the main trends observed in the three setups can be approached using the baseline model. Although the model morphing did not account for specific skeletal dimensions, it reduced some of the discrepancies between model response and reference for the drop test and flat plate impact. However, it had little effect on the pendulum test. In that case, the model response was in the corridor at low speed but above at higher speeds. Possible reasons for this difference should be further investigated.

Internal architecture of the mandibular condyle of rabbits is related to dietary resistance during growth

Although there is considerable evidence that bone responds to the loading environment in which it develops, few analyses have examined phenotypic plasticity or bone functional adaptation in the masticatory apparatus. Prior work suggests that masticatory morphology is sensitive to differences in food mechanical properties during development; however, the importance of the timing/duration of loading and variation in naturalistic diets is less clear. Here, we examined microstructural and macrostructural differences in the mandibular condyle in four groups of white rabbits (Oryctolagus cuniculus) raised for a year on diets that varied in mechanical properties and timing of the introduction of mechanically challenging foods, simulating seasonal variation in diet. We employed sliding semilandmarks to locate multiple volumes of interest deep to the mandibular condyle articular surface, and compared bone volume fraction, trabecular thickness and spacing, and condylar size/shape among experimental groups. The results reveal a shared pattern of bony architecture across the articular surface of all treatment groups, while also demonstrating significant among-group differences. Rabbits raised on mechanically challenging diets have significantly increased bone volume fraction relative to controls fed a less challenging diet. The post-weaning timing of the introduction of mechanically challenging foods also influences architectural properties, suggesting that bone plasticity can extend well into adulthood and that bony responses to changes in loading may be rapid. These findings demonstrate that bony architecture of the mandibular condyle in rabbits responds to variation in mechanical loading during an organism's lifetime and has the potential to track dietary variation within and among species.

Thyroid Hormone Diseases and Osteoporosis

Thyroid hormones are essential for normal skeletal development and normal bone metabolism in adults but can have detrimental effects on bone structures in states of thyroid dysfunction. Untreated severe hyperthyroidism influences the degree of bone mass and increases the probability of high bone turnover osteoporosis. Subclinical hyperthyroidism, defined as low thyrotropin (TSH) and free hormones within the reference range, is a subtler disease, often asymptomatic, and the diagnosis is incidentally made during screening exams. However, more recent data suggest that this clinical condition may affect bone metabolism resulting in decreased bone mineral density (BMD) and increased risk of fracture, particularly in postmenopausal women. The main causes of exogenous subclinical hyperthyroidism are inappropriate replacement dose of thyroxin and TSH suppressive L-thyroxine doses in the therapy of benign thyroid nodules and thyroid carcinoma. Available data similarly suggest that a long-term TSH suppressive dose of thyroxin may decrease BMD and may induce an increased risk of fracture. These effects are particularly observed in postmenopausal women but are less evident in premenopausal women. Overt hypothyroidism is known to lower bone turnover by reducing both osteoclastic bone resorption and osteoblastic activity. These changes in bone metabolism would result in an increase in bone mineralization. At the moment, there are no clear data that demonstrate any relationship between BMD in adults and hypothyroidism. Despite these clinical evidences, the cellular and molecular actions of thyroid hormones on bone structures are not complete clear.

Baby steps towards linking calcaneal trabecular bone ontogeny and the development of bipedal human gait

Trabecular bone structure in adulthood is a product of a process of modelling during ontogeny and remodelling throughout life. Insight into ontogeny is essential to understand the functional significance of trabecular bone structural variation observed in adults. The complex shape and loading of the human calcaneus provides a natural experiment to test the relationship between trabecular morphology and locomotor development. We investigated the relationship between calcaneal trabecular bone structure and predicted changes in loading related to development of gait and body size in growing children. We sampled three main trabecular regions of the calcanei using micro-computed tomography scans of 35 individuals aged between neonate to adult from the Norris Farms #36 site (1300 AD, USA) and from Cambridge (1200-1500 AD, UK). Trabecular properties were calculated in volumes of interest placed beneath the calcaneocuboid joint, plantar ligaments, and posterior talar facet. At birth, thin trabecular struts are arranged in a dense and relatively isotropic structure. Bone volume fraction strongly decreases in the first year of life, whereas anisotropy and mean trabecular thickness increase. Dorsal compressive trabecular bands appear around the onset of bipedal walking, although plantar tensile bands develop prior to predicted propulsive toe-off. Bone volume fraction and anisotropy increase until the age of 8, when gait has largely matured. Connectivity density gradually reduces, whereas trabeculae gradually thicken from birth until adulthood. This study demonstrates that three different regions of the calcaneus develop into distinct adult morphologies through varying developmental trajectories. These results are similar to previous reports of ontogeny in human long bones and are suggestive of a relationship between the mechanical environment and trabecular bone architecture in the human calcaneus during growth. However, controlled experiments combined with more detailed biomechanical models of gait maturation are necessary to establish skeletal markers linking growth to loading. This has the potential to be a novel source of information for understanding loading levels, activity patterns, and perhaps life history in the fossil record.

Trabecular architecture of the capitate and third metacarpal through ontogeny in chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla)

Chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla) both knuckle-walk in adulthood but are known to develop their locomotor strategies differently. Using dentally defined age-groups of both Pan and Gorilla and behavioral data from the literature, this study presents an internal trabecular bone approach to better understand the morphological ontogeny of knuckle-walking in these taxa. Capitate and third metacarpal bones were scanned by μCT at 23-43 μm resolution with scaled volumes of interest placed centrally within the head of the capitate and base of the third metacarpal. Trabecular measures related to activity level (size-adjusted bone volume/total volume, trabecular number, and bone surface area/bone volume) met expectations of decreasing through ontogeny in both taxa. Degree of anisotropy did not show statistical support for predicted species differences, but this may be due to the sample size as observed changes through ontogeny reflect expected trends in the capitate. Analyses of principal trabecular orientation corroborated known behavioral differences related to variation of hand use in these taxa, but only Pan showed directional patterning associated with suggested wrist posture. Assessment of allometry showed that the trabecular bone of larger animals is characterized by fewer and thinner trabeculae relative to bone size. In combination, these findings confirm the efficacy of trabecular bone in reflecting locomotor ontogeny differences between closely related taxa. These techniques show promise for use within the hominin fossil record, particularly for taxa hypothesized to be arboreal in some capacity.

Compositional and mechanical properties of growing cortical bone tissue: a study of the human fibula

Human cortical bone contains two types of tissue: osteonal and interstitial tissue. Growing bone is not well-known in terms of its intrinsic material properties. To date, distinctions between the mechanical properties of osteonal and interstitial regions have not been investigated in juvenile bone and compared to adult bone in a combined dataset. In this work, cortical bone samples obtained from fibulae of 13 juveniles patients (4 to 18 years old) during corrective surgery and from 17 adult donors (50 to 95 years old) were analyzed. Microindentation was used to assess the mechanical properties of the extracellular matrix, quantitative microradiography was used to measure the degree of bone mineralization (DMB), and Fourier transform infrared microspectroscopy was used to evaluate the physicochemical modifications of bone composition (organic versus mineral matrix). Juvenile and adult osteonal and interstitial regions were analyzed for DMB, crystallinity, mineral to organic matrix ratio, mineral maturity, collagen maturity, carbonation, indentation modulus, indicators of yield strain and tissue ductility using a mixed model. We found that the intrinsic properties of the juvenile bone were not all inferior to those of the adult bone. Mechanical properties were also differently explained in juvenile and adult groups. The study shows that different intrinsic properties should be used in case of juvenile bone investigation.

Ontogenetic changes to bone microstructure in an archaeologically derived sample of human ribs

There is considerable variation in the gross morphology and tissue properties among the bones of human infants, children, adolescents, and adults. Using 18 known-age individuals (n_female  = 8, n_male  = 9, n_unknown  = 1; birth to 21 years old), from a well-documented cemetery collection, Spitalfields Christ Church, London, UK, this study explores growth-related changes in cortical and trabecular bone microstructure. Micro-CT scans of mid-shaft middle thoracic ribs are used for quantitative analysis. Results are then compared to previously quantified conventional histomorphometry of the same sample. Total area (Tt.Ar), cortical area (Ct.Ar), cortical thickness (Ct.Th), and the major (Maj.Dm) and minor (Min.Dm) diameters of the rib demonstrate positive correlations with age. Pore density (Po.Dn) increases, but age-related changes to cortical porosity (Ct.Po) appear to be non-linear. Trabecular thickness (Tb.th) and trabecular separation (Tb.Sp) increase with age, whereas trabecular bone pattern factor (Tb.Pf), structural model index (SMI), and connectivity density (Conn.D) decrease with age. Sex-based differences were not identified for any of the variables included in this study. Some samples display clear evidence of diagenetic alteration without corresponding changes in radiopacity, which compromises the reliability of bone mineral density (BMD) data in the study of past populations. Cortical porosity data are not correlated with two-dimensional measures of osteon population density (OPD). This suggests that unfilled resorption spaces contribute more significantly to cortical porosity than do the Haversian canals of secondary osteons. Continued research using complementary imaging techniques and a wide array of histological variables will increase our understanding of age- and sex-specific ontogenetic patterns within and among human populations.

Negative pressure wound therapy in reconstructing extensive leg and foot soft tissue loss in a child: a case study

Open fractures of the leg with large loss of tissue require extensive reconstructive methods that can injure the donor area. The use of negative pressure wound therapy (NPWT) may minimise the impact of these reconstructive methods because of its capacity to create granulation tissue that will form a wound bed for the skin graft, thus reducing the volume of soft tissue defect and saving the donor region. This case study describes the effectiveness of NPWT in the treatment and reconstruction of an open fracture of the leg, with massive loss of soft tissue, associated with elastic intramedullary nailing in a 10-year-old female patient, who was a victim of a car accident. Clinical examination revealed a Gustilo-Anderson IIIB open fracture of the left leg, with the avulsion of the fifth toe, disarticulation of the fifth metatarsal bone, extensively damaged skin and subcutaneous tissue in the medium and distal third of the left leg and left foot. The bone was exposed in the distal part of the leg, external malleolus and left calcaneus. Profuse lavage, reduction of the tibial fracture and elastic intramedullary nailing, amputation of the fifth left toe, necrectomy and debridement of devitalised tissue were performed. NPWT was started, with the dressing changed every five days. After 55 days of using NPWT, granulation tissue covered the soft tissue defect and created a wound bed for the skin graft. NPWT helped the management of this open wound, achieving a wound bed for the skin graft, avoiding the use of complex reconstructive methods.

Meniscal allograft transplantation in the paediatric population: early referral is justified

PURPOSE

The need for meniscal allograft transplantation (MAT) in children is rare, and as a result, there is a paucity of evidence detailing survivorship and clinical outcome. MAT has been shown to significantly reduce pain and improve function in the adult population. The aim of this study was to document the outcomes of a single surgeon case series of MAT in the paediatric population.

METHODS

Analysis of a prospective meniscal allograft transplantation (MAT) group database of 280 patients was performed. Twenty-three patients met the inclusion criteria-undergoing MAT aged 18 years or younger.

RESULTS

Fourteen were female and nine were male with median age of 17 (range 8-18). Thirteen (57%) were right knee and nineteen (83%) were lateral. Additional procedures included high tibial osteotomy, anterior cruciate ligament reconstruction, and microfracture procedures. The median follow-up was 3.8 years (range of 0.2 to 7.8 years). There have been no cases of graft failure. All patients demonstrated improvement in all the modalities of the KOOS outcome scores. At 5 years, the Lysholm score had improved from 57.9 to 87.6 (SD 12.1), Tegner activity score had improved from 2 to 5 (range 4-7) and IKDC score had improved from 40.6 to 78.6 (SD 15.8). Four patients required secondary surgical intervention. No patients developed a superficial or deep infection.

CONCLUSION

Meniscal allograft transplantation in children is founded on the successful results of MAT in the adult population. We have demonstrated in this series that MAT can improve function and reduce pain in the paediatric population, and is, therefore, a viable treatment option for the management of the symptomatic paediatric meniscal-deficient knee. Early referral should be considered in the patients with post-meniscectomy syndrome, pain on weight bearing with a history of previous menisectomy.

LEVEL OF EVIDENCE

IV.

Sleep-Disordered Breathing Is Associated with Reduced Mandibular Cortical Width in Children

INTRODUCTION

Evidence from the adult population suggests that sleep-disordered breathing (SDB) (i.e., obstructive sleep apnea [OSA]) is negatively associated with bone mineral density. Whether a similar association exists in children with SDB has not been investigated. Using the mandibular cortical width (MCW) as a proxy for skeletal bone density, we investigated if children at risk of SDB or diagnosed with OSA have a reduced mandibular cortical width compared to children without SDB.

METHODS

Two retrospective cross-sectional studies were performed. The first study included comparison of MCW between 24 children with polysomnographically (PSG) diagnosed OSA and 72 age- and sex-matched control children. The second study included a cohort of children in which SDB was suggested by the Pediatric Sleep Questionnaire (PSQ) ( n = 101). MCW was measured from panoramic radiographs.

RESULTS

Multiple-predictors regression analysis from the first study indicated that in children with a severe form of SDB, as induced by OSA severity, there was a negative association with MCW (β = -0.290, P = 0.049). Moreover, PSG-diagnosed OSA children had thinner MCW (2.9. ± 0.6mm) compared to healthy children (3.5 ± 0.6 mm; P = 0.002). These findings were further supported by the second study illustrating that PSQ total scores were negatively associated with MCW (β = -0.391, P < 0.001).

CONCLUSIONS

Findings suggest that children at risk for or diagnosed with SDB exhibit reduced mandibular cortical width that purportedly may reflect alterations in bone homeostasis.

KNOWLEDGE TRANSFER STATEMENT

We report that sleep-disordered breathing (including its severe form, obstructive sleep apnea) in children is associated with reduced mandibular cortical width. This association might be a direct consequence of reduced bone health to sleep-disordered breathing or a reflection that reduced bone formation underlies the development of sleep-disordered breathing. Our findings suggest that mandibular cortical width can be used as an adjunct diagnostic parameter for the diagnosis of sleep-disordered breathing.

Acute continuous moderate-intensity exercise, but not low-volume high-intensity interval exercise, attenuates postprandial suppression of circulating osteocalcin in young overweight and obese adults

Bone remodeling markers (BRMs) are suppressed following the consumption of a meal. Our findings indicate that a single session of continuous moderate-intensity exercise, but not low-volume high-intensity interval exercise, performed 1 h after a meal attenuates the postprandial suppression of BRMs.

INTRODUCTION

Acute exercise transiently increases BRMs including osteocalcin (tOC) and the undercarboxylated form of osteocalcin (ucOC), a hormone that is implicated in glucose regulation. The effects of acute exercise and exercise-intensity on postprandial levels of tOC and ucOC are unknown.

METHODS

Twenty-seven adults that were overweight or obese (age 30 ± 1 years; BMI 30 ± 1 kg∙m^-2; mean ± SEM) were randomly allocated to perform a single session of low-volume high-intensity interval exercise (LV-HIIE; nine females, five males) or continuous moderate-intensity exercise (CMIE; eightfemales, five males) 1 h after consumption of a standard breakfast. Serum tOC, ucOC, and ucOC/tOC were measured at baseline, 1 h, and 3 h after breakfast consumption on a rest day (no exercise) and the exercise day (exercise 1 h after breakfast).

RESULTS

Compared to baseline, serum tOC and ucOC were suppressed 3 h after breakfast on the rest day (- 10 ± 1% and - 6 ± 2%, respectively; p < 0.05), whereas ucOC/tOC was elevated (2.5 ± 1%; p = 0.08). Compared to the rest day, CMIE attenuated the postprandial-induced suppression of tOC (rest day - 10 ± 2% versus CMIE - 5 ± 2%, p < 0.05) and ucOC (rest day - 6 ± 4% versus CMIE 11 ± 2%, p < 0.05), and increased postprandial ucOC/tOC (rest day 3 ± 2% versus CMIE 15 ± 1%, p < 0.05). In contrast, LV-HIIE did not alter postprandial tOC, ucOC, or ucOC/tOC (all p > 0.1).

CONCLUSIONS

Acute CMIE, but not LV-HIIE, attenuates the postprandial-induced suppression of tOC and ucOC. CMIE may be an effective tool to control the circulating levels of BRMs following meal consumption in overweight/obese adults.

Bone mineral density, hand grip strength, smoking status and physical activity in Polish young men

The human skeleton undergoes constant changes encompassing the phases of growth, consolidation and involution of the bone tissue. The aim of the research was to assess the relationship between bone mineral density (BMD) and such factors as hand grip strength, somatic structure or attitudes to tobacco smoking in men with different levels of physical activity. The study included 172 males aged 20-30 years. Mineral density and forearm bone mass were measured using the dual-energy X-ray absorptiometry method. Physical activity levels were assessed with the use of the International Physical Activity Questionnaire. Hand grip strength was measured with Jamar hand dynamometer. Attitudes towards smoking were assessed using the Global Adult Tobacco Survey. The correlation between a high level of physical activity among men and higher BMD and bone mass both in the distal and proximal parts of the forearm was statistically significantly greater compared to individuals with an insufficient level of physical activity. A better state of BMD and higher bone mass in both forearm bones was noted among non-smoking men. A high level of physical activity was the most significant predictor of BMD in the distal part of the forearm. The regression analysis in the proximal part revealed that body mass and a high level of physical activity were the most important predictors of BMD. The lack of physical activity was associated with more frequent occurrence of low bone mass in men. Tobacco smoking may be one of the most important risk factors of poor bone mineralization in young men.

Translational studies provide insights for the etiology and treatment of cortical bone osteoporosis

Increasing attention is being focused on the important contributions of cortical bone to bone strength, fractures and osteoporosis therapies. Recent progress in human genome wide association studies in combination with high-throughput mouse gene knockout phenotyping efforts of multiple genes and advanced conditional gene inactivation in mouse models have successfully identified genes with crucial roles in cortical bone homeostasis. Particular attention in this review is given to genes, such as WNT16, POSTN and SFRP4, that differentially affect cortical and trabecular bone architecture. We propose that animal models of cortical bone metabolism will substantially contribute to developing anabolic osteoporosis therapies that improve cortical bone mass and reduce non-vertebral fracture risk.

Indian girls have higher bone mineral content per unit of lean body than boys through puberty

Our aim is to describe changes in the muscle-bone unit assessed as a ratio of bone mineral content (BMC) to lean body mass (LBM) through puberty at total body and various skeletal sites in Indian boys and girls. A cross-sectional study was conducted (888 children, 480 boys, aged 5-17 years) in Pune, India. Pubertal staging was assessed. BMC, LBM and fat percentage at the arms, legs, android, gynoid and total body (less the head) were assessed by dual energy X-ray absorptiometry. The amount of BMC per unit LBM (BMC/LBM) was computed. Changes in mean BMC/LBM at 5 Tanner (pubertal) stages after adjustment for age and fat percentage were calculated. In boys, adjusted BMC/LBM was significantly higher with successive Tanner stages [legs (TS-II vs TS-I), android (TS-III vs TS-II, TS-IV vs TS-III) and gynoid region (TS-III vs TS-II and TS-II vs TS-I) (p < 0.05)]. In girls, adjusted BMC/LBM was significantly higher with successive Tanner stages at total body, legs and gynoid (TS-III vs TS-II; TS-II vs TS-I; TS-V vs TS-IV), arms (TS-I to TS-V) and android regions (TS-V vs TS-IV) (p < 0.05). Boys had significantly higher adjusted BMC/LBM than girls at earlier Tanner stages (TS-I to TS-III), whereas girls had significantly higher adjusted BMC/LBM than boys at later Tanner stages (TS-IV, TS-V) (p < 0.05). Indian boys and girls showed higher total and regional body, and age- and fat percentage-adjusted BMC/LBM with successive pubertal stages. Girls had higher BMC/LBM than boys which may possibly act as a reservoir for later demands of pregnancy and lactation.

Trabecular bone microarchitecture analysis, a way for an early detection of genetic dwarfism? Case study of a dwarf mother's offspring

A 66 year-old woman with a disproportionate dwarfism and who bore seven children was discovered at the Middenbeemster archaeological site (The Netherlands). Three are perinates and show no macroscopic or radiological evidence for a FGFR3 mutation causing hypo-or achondroplasia. This mutation induces dysfunction of the growth cartilage, leading to abnormalities in the development of trabecular bone. Because the mutation is autosomal dominant, these perinates have a 50% risk of having been affected. This study determines whether trabecular bone microarchitecture (TBMA) analysis is useful for detecting genetic dwarfism. Proximal metaphyses of humeri were μCT-scanned with a resolution of 7-12 μm. Three volumes of interest were segmented from each bone with TIVMI© software. The TBMA was quantified in BoneJ© using six parameters on which a multivariate analysis was then performed. Two of the Middenbeemster perinates show a quantitatively different TBMA organization. These results and the family's medical history suggest a diagnosis of genetic dwarfism for this two perinates. This study provides evidence to support the efficacy of μCT for diagnosing early-stage bone disease.

Bone Turnover in Young Adult Men: Cross-Sectional Determinants and Associations With Prospectively Assessed Bone Loss

Biochemical markers of bone turnover are higher in young adult men than in middle-aged men or young adult women. Nonetheless, little is known about the determinants and clinical significance hereof. The present study examined determinants of serum bone turnover markers in men around peak bone mass age, and explored whether bone turnover at this age predicts subsequent changes in bone mass. We used cross-sectional and longitudinal data from 973 and 428 healthy men, respectively, aged 25 to 45 years at baseline, including baseline procollagen type I amino-terminal propeptide (P1NP), osteocalcin, and C-terminal telopeptide of type I collagen (CTX) from fasting serum samples, baseline questionnaire-assessed physical activity levels, and baseline and follow-up dual-energy X-ray absorptiometry-derived areal bone mineral density (aBMD) and body composition. Mean follow-up time was 12.4 ± 0.4 years. At baseline, all bone turnover markers were inversely associated with total body fat mass (β ≤ -0.20, p < 0.001), and positively with physical activity during sports activities (β ≥ 0.09, p ≤ 0.003), and, albeit not independently from fat mass, total body lean mass (β ≥ 0.20, p ≤ 0.003). Mean annual aBMD changes in the longitudinal cohort were -0.19% ± 0.24% at the total body, -0.14% ± 0.42% at the spine, -0.49% ± 0.47% at the femoral neck, and -0.25% ± 0.37% at the total hip (all p < 0.001). Higher bone turnover markers at baseline were associated with larger decreases in aBMD at all measurement sites (β ≤ -0.08, p ≤ 0.081 for P1NP; β ≤ -0.16, p ≤ 0.002 for osteocalcin; and β ≤ -0.21, p < 0.001 for CTX). In conclusion, our findings show that sports activities and body composition, primarily fat mass, are the main identified determinants of bone turnover in men around peak bone mass age. Further, bone turnover at this age is an important determinant of subsequent changes in bone mass, with higher levels of bone turnover markers being associated with greater decreases in aBMD. © 2017 American Society for Bone and Mineral Research.

New insights into the biomechanics of Legg-Calvé-Perthes' disease: The Role of Epiphyseal Skeletal Immaturity in Vascular Obstruction

Objectives

Legg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition.

Methods

Finite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP.

Results

The results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression.

Conclusion

The findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease.

Cite this article: M. Pinheiro, C. A. Dobson, D. Perry, M. J. Fagan. New insights into the biomechanics of Legg-Calvé-Perthes’ disease: The Role of Epiphyseal Skeletal Immaturity in Vascular Obstruction. Bone Joint Res 2018;7:148–156. DOI: 10.1302/2046-3758.72.BJR-2017-0191.R1.

Trabecular Bone Morphology Correlates With Skeletal Maturity and Body Composition in Healthy Adolescent Girls

Context

Growth in healthy children is associated with changes in bone density and microarchitecture. Trabecular morphology is an additional important determinant of bone strength, but little is currently known about trabecular morphology in healthy young people.

Objective

To investigate associations of trabecular morphology with increasing maturity and with body composition in healthy girls.

Design

Cross-sectional study.

Setting

Academic research center.

Participants

Eighty-six healthy girls aged 9 to 18 years.

Main Outcome Measures

High-resolution peripheral quantitative computed tomography and individual trabecula segmentation were used to assess volumetric bone density, microarchitecture, and trabecular morphology (plate-like vs rod-like) at the distal radius and tibia.

Results

Plate-like bone volume divided by total volume (pBV/TV) increased statistically significantly at the tibia (R = 0.41, P < 0.001), whereas rod-like BV/TV (rBV/TV) decreased statistically significantly at both the radius and tibia (R = -0.34, P = 0.003 and R = -0.28, P = 0.008, respectively) with increasing bone age. In multivariable models, lean mass positively correlated with pBV/TV and plate number at the radius and with plate thickness at both sites. In contrast, fat mass negatively correlated with plate thickness at the tibia and plate surface at both sites. In addition, fat mass positively correlated with rBV/TV and number at the tibia. pBV/TV at both the distal radius and tibia was positively correlated with spine bone mineral density.

Conclusions

Increasing maturity across late childhood and adolescence is associated with changes in trabecular morphology anticipated to contribute to bone strength. Body composition correlates with trabecular morphology, suggesting that muscle mass and adiposity in youth may contribute to long-term skeletal health.

Record of Nile seasonality in Nubian neonates

The oxygen isotope compositions of bones (n = 11) and teeth (n = 20) from 12 Sudanese individuals buried on Sai Island (Nubia) were analysed to investigate the registration of the evolution of the Nile environment from 3700 to 500 years BP and the potential effects of ontogeny on the oxygen isotope ratios. The isotopic compositions were converted into the composition of drinking water, ultimately originating from the Nile. δ¹⁸O values decrease during ontogeny; this is mainly related to breastfeeding and physiology. Those of neonates present very large variations. Neonates have a very high bone turnover and are thus able to record seasonal δ¹⁸O variations of the Nile waters. These variations followed a pattern very similar to the present one. Nile δ¹⁸O values increased from 1.4 to 4.4 ‰ (Vienna Standard Mean Ocean Water) from the Classic Kerma (∼3500 BP) through the Christian period (∼1000 BP), traducing a progressive drying of Northeast Africa.

Abnormally High and Heterogeneous Bone Matrix Mineralization After Childhood Solid Organ Transplantation: A Complex Pathology of Low Bone Turnover and Local Defects in Mineralization

Chronic renal, liver, and heart failure in children associates with multiple skeletal complications. Increased fracture incidence often persists after transplantation and could be related to alterations in bone material properties. In the present cohort study we evaluated bone mineralization density distribution (BMDD) by quantitative backscattered electron imaging (qBEI) in 23 pediatric solid organ allograft recipients with suspected osteoporosis. We measured BMDD in the entire cross-sectional area of transiliac bone biopsies obtained from kidney (n = 9), liver (n = 9), and heart (n = 5) transplant recipients (aged 7.6 to 19.7 years; 6.0 ± 5.6 years posttransplantation, patients with a history of clinical fractures: n = 14). The BMDD findings were compared with age-appropriate references and with a previously presented cohort of children with chronic kidney disease on dialysis (CKD5D, n = 18). Furthermore, we related the BMDD parameters with patients' clinical and bone histomorphometric outcomes. Compared to healthy children, qBEI results for cancellous and cortical bone in transplant recipients revealed an increase in the most frequently occurring calcium concentration (+2.9%, p = 0.001; +3.5%, p = 0.014), in the portion of fully mineralized bone (fivefold; 10-fold, both p < 0.0001) and in heterogeneity of mineralization (+26,5% and +27.8%, both p < 0.0001), respectively. Moreover, the BMDD parameters were nonsignificantly distinct from CKD5D cohort except that the heterogeneity in mineralization was higher posttransplantation. There was a strong inverse correlation between the average calcium content of the bone matrix and patients' biochemical ALP levels, histomorphometric indices of bone formation and resorption. The abnormally high bone matrix mineralization in transplant recipients, consistent with serum and histomorphometric outcomes, suggests a history of low bone turnover with accumulation of fully mineralized bone packets. Additionally, the increased heterogeneity of mineralization suggests local alterations in mineralization kinetics, which may be linked to dysfunctional osteocytes that were recently shown to accumulate within the bone matrix during organ failure and concomitant glucocorticoid and immunosuppressive medication. © 2017 American Society for Bone and Mineral Research.