Prevalent fractures are related to cortical bone geometry in young healthy men at age of peak bone mass

Pathways linking sports participation to bone density and geometry among adolescents: ABCD growth study

This study investigated variables linked to sports participation and its impacts on bone density and geometry among adolescents. This study shows that lean soft tissue was the main link between sports participation and bone density and geometry among adolescents of both sexes. Higher ground reaction force in sports impacts bone positively, while higher body fatness and bone resorption rate negatively, all these variables seem to assume complementary roles in this phenomenon, especially among boys.

INTRODUCTION

Sports participation boosts bone formation in early life, but the pathways are still unclear.

OBJECTIVE

To investigate which variables linked to sports participation are most consistently related to bone density and geometry among adolescents.

METHODS

A total of 86 adolescents (28 girls) aged from 11 to 17 years were classified as Control (12 adolescents) and Sport (74 adolescents). The outcomes were bone density and geometry from lower limbs measured using the bone densitometry technique. Variables linked to participation were intensity, ground reaction force, strength, lean soft tissue, and parameter of bone formation. Covariates were sex, somatic maturation, and body fatness.

RESULTS

Among boys, lean soft tissue (r = 0.861) remained the main determinant of bone density along with sport ground reaction force (r = 0.211). For bone geometry, lean soft tissue remained the main determinant, while blood concentration of bone resorption markers (r = - 0.262) and body fatness (r = - 0.205) were inversely related to it. For girls, the only determinant of bone density and geometry was lean soft tissue (ranging from r = 0.461 to r = 0.759). All models explained bone density and geometry better among boys (from 73.4 to 80.9%) than girls (from 47.6 to 62.6%).

CONCLUSION

Lean soft tissue is the main link of sports participation with bone density and geometry among adolescents of both sexes. Higher ground reaction force in sports impacts bone positively, while higher body fatness and bone resorption rate negatively, all these variables seem to assume complementary roles in this phenomenon, especially among boys.

Predicting complications and morbidities in PAD patients through lower extremity compositions with dual-energy CT and material decomposition: a 2-year follow-up observational study

BACKGROUND

Peripheral artery disease (PAD) is associated with various morbidities. This study aims to investigate the correlation between different lower extremity compositions and development of morbidities in PAD patients.

METHODS

Between January 2018 and December 2020, 108 subjects diagnosed of PAD were enrolled (mean age of 64.1 ± 13.5 years) and utilized dual-energy computed tomography (DECT) with material decomposition to measure the vessel volume, muscle volume, fat volume, and cortical-bone volume in lower extremity respectively. The association between each leg composition and developing complications or morbidities in PAD patients was analyzed over a two-year follow-up.

RESULTS

Fontaine stage 3 and 4 had lower muscle mass compared to stages 1 and 2. More severe vascular stenosis was associated with lower muscle, fat, and cortical-bone volume. Patients with severe Fontaine stages (3 and 4) and lower-leg vascular stenosis had a higher risk of developing infection or inflammation (OR 45.5, 95% CI: 13.5-166.7, and OR 11.7, 95% CI: 2.8-50, P < 0.05) and amputation (OR 18.2, 95% CI: 2.2-142.8, and OR 10.7, 95% CI: 1.11-100, P < 0.05). Lower thigh cortical-bone volume was associated with an increased risk of falls resulting in fractures (OR: 1.39, 95% CI: 1.13-2.19, P < 0.01). Thigh cortical-bone volume below 64.5 cm3 was identified as the cut-off value to predict fall-related fractures, with a sensitivity of 100% and specificity of 92%.

CONCLUSIONS

This study demonstrates the potential of DECT with material decomposition to assess lower extremity composition and its relevance in predicting complications and morbidities in PAD patients. Severe vascular stenosis may contribute to muscle wasting and subsequent complications, while lower thigh cortical-bone mass may serve as a predictor of fall-related fractures.

Bone Accrual Trajectories in Children and Adolescents with Perinatal HIV Infection

CONTEXT

Low bone mineral density (BMD) has been reported in children and adolescents living with perinatally-acquired HIV (PHIV). Little is known about their bone accrual through puberty compared to an uninfected healthy cohort.

OBJECTIVE

To compare bone accrual in PHIV and healthy children.

DESIGN

PHIV children aged 7-16 years had dual energy X-ray absorptiometry (DXA) at entry, 2 years, and then at least 2 years later. Bone accrual was compared to healthy children from the Bone Mineral Density in Childhood Study (BMDCS).

SETTING

United States academic clinical research centers.

PATIENTS

172 PHIV; 1321 BMDCS.

ANALYSIS

We calculated height-adjusted whole-body and spine BMD and bone mineral content (BMC) Z-scores in PHIV using BMDCS reference curves. We fit piecewise weighted linear mixed effects models with change points at 11 and 15 years, adjusted for age, sex, race, height Z-score, and Tanner stage, to compare BMD and BMC Z-scores across actual age by cohort.Main Outcome Measure: BMD/BMC Z-scores.

RESULTS

Height-adjusted whole-body BMD and BMC Z-scores in PHIV were lower across age compared to BMDCS children. Spine BMD Z-score across age was higher in PHIV after height adjustment. Whole-body and spine bone area tended to be lower in PHIV. PHIV had slower accrual in whole-body and spine bone area before 14 years. After 15 years, bone area accruals were similar, as were height-adjusted spine BMC Z-scores, across age.

CONCLUSIONS

PHIV had persistent deficits in all measures except height-adjusted spine BMD and BMC Z-scores. Data are needed on PHIV followed to adulthood.

Measuring Bone Healing: Parameters and Scores in Comparison

(1) Background: Bone healing is a complex process that can not be replicated in its entirety in vitro. Research on bone healing still requires the animal model. The critical size femur defect (CSFD) in rats is a well-established model for fractures in humans that exceed the self-healing potential. New therapeutic approaches can be tested here in vivo. Histological, biomechanical, and radiological parameters are usually collected and interpreted. However, it is not yet clear to what extent they correlate with each other and how necessary it is to record all parameters. (2) Methods: The basis for this study was data from three animal model studies evaluating bone healing. The µCT and histological (Movat pentachrome, osteocalcin) datasets/images were reevaluated and correlation analyses were then performed. Two image processing procedures were compared in the analysis of the image data. (3) Results: There was a significant correlation between the histologically determined bone fraction (Movat pentachrome staining) and bending stiffness. Bone fraction determined by osteocalcin showed no prognostic value. (4) Conclusions: The evaluation of the image datasets using ImageJ is sufficient and simpler than the combination of both programs. Determination of the bone fraction using Movat pentachrome staining allows conclusions to be drawn about the biomechanics of the bone. A standardized procedure with the ImageJ software is recommended for determining the bone proportion.

Exploring the Possibility of Measuring Vertebrae Bone Structure Metrics Using MDCT Images: An Unpaired Image-to-Image Translation Method

Bone structure metrics are vital for the evaluation of vertebral bone strength. However, the gold standard for measuring bone structure metrics, micro-Computed Tomography (micro-CT), cannot be used in vivo, which hinders the early diagnosis of fragility fractures. This paper used an unpaired image-to-image translation method to capture the mapping between clinical multidetector computed tomography (MDCT) and micro-CT images and then generated micro-CT-like images to measure bone structure metrics. MDCT and micro-CT images were scanned from 75 human lumbar spine specimens and formed training and testing sets. The generator in the model focused on learning both the structure and detailed pattern of bone trabeculae and generating micro-CT-like images, and the discriminator determined whether the generated images were micro-CT images or not. Based on similarity metrics (i.e., SSIM and FID) and bone structure metrics (i.e., bone volume fraction, trabecular separation and trabecular thickness), a set of comparisons were performed. The results show that the proposed method can perform better in terms of both similarity metrics and bone structure metrics and the improvement is statistically significant. In particular, we compared the proposed method with the paired image-to-image method and analyzed the pros and cons of the method used.

Is repeated childhood fracture related to areal bone density or body composition in middle age?

Childhood fracture is common, but whether it predicts adult fracture is not clear. Repeat childhood fracture was associated with adult (≤ 45 years) fracture, and in women, lower areal bone density was associated with repeat childhood fracture. Identifying fracture-prone children can modify adult fracture risk management.

INTRODUCTION

A quarter of boys and 15% of girls will suffer multiple fractures, but it is not clear whether multiple fractures during growth predict fracture risk and areal bone density in adulthood. This study evaluated whether children who repeatedly fracture were at increased risk of low areal bone density, abnormal body composition, and fractures by age 45.

METHODS

A subsample of a large birth cohort study with childhood fracture cases had areal bone density assessed at age 45 years. Participants were questioned regularly across their lifetime about fractures during childhood (ages 0-18 years of age) and adulthood (any fracture between 18 and 45 years). The number of fractures was collapsed into three categories: no fractures; 1 fracture; and > 1 fracture, separately for child and adult groups.

RESULTS

At age 45 years, areal bone mineral density (g/cm2) and body composition were measured with dual X-ray absorptiometry in n = 555 participants. Compared to no fractures, twice as many girls (14% vs 7%, P = 0.156) and boys (31.4% vs 14.1%, P = 0.004) who repeatedly fractured in childhood sustained multiple fractures as adults. Both girls and boys who were fracture-free tended to remain fracture-free as adults (79.8% compared with 62.8%, P = 0.045, and 64.8% compared with 51.4%, P = 0.025, in males and females, respectively). Participants were more than twice as likely to fracture repeatedly as adults if they had sustained multiple fractures as a child (OR 2.5 95% CI: 1.4, 4.6). Women who repeatedly fractured during childhood had lower areal bone density, whereas repeated fracturing during childhood was not associated with areal bone density or body composition in men, even after adjustment for other factors known to influence fracture history.

CONCLUSION

Childhood fracture history is associated with persistent skeletal fragility in adulthood (≤ 45 years), even after adjustment for behavioral and demographic factors known to influence fracture history.

A review on experimental and numerical investigations of cortical bone fracture

This paper comprehensively reviews the various experimental and numerical techniques, which were considered to determine the fracture characteristics of the cortical bone. This study also provides some recommendations along with the critical review, which would be beneficial for future research of fracture analysis of cortical bone. Cortical bone fractures due to sports activities, climbing, running, and engagement in transport or industrial accidents. Individuals having different diseases are also at high risk of cortical bone fracture. It has been observed that osteon orientation influences cortical bone fracture toughness and fracture mechanisms. Apart from this, recent studies indicate that fracture parameters of cortical bone also depend on many factors such as age, sex, temperature, osteoporosis, orientation, location, loading condition, strain rate, and storage facility, etc. The cortical bone regains its fracture toughness due to various toughening mechanisms. Owing to these factors, several experimental, clinical, and numerical investigations have been carried out to determine the fracture parameters of the cortical bone. Cortical bone is the dense outer surface of the bone and contributes to 80%–82% of the skeleton mass. Cortical bone experiences load far exceeding body weight due to muscle contraction and the dynamics of motion. It is very important to know the fracture pattern, direction of fracture, location of the fracture, and toughening mechanism of cortical bone. A basic understanding of the different factors that affect the fracture parameters and fracture mechanisms of the cortical bone is necessary to prevent the failure and fracture of cortical bone. This review has summarized the advancement considered in the various experimental techniques and numerical methods to get complete information about the fracture mechanisms of cortical bone.

How to manage osteoporosis before the age of 50

This narrative review discusses several aspects of the management of osteoporosis in patients under 50 years of age. Peak bone mass is genetically determined but can also be affected by lifestyle factors. Puberty constitutes a vulnerable period. Idiopathic osteoporosis is a rare, heterogeneous condition in young adults due in part to decreased osteoblast function and deficient bone acquisition. There are no evidence-based treatment recommendations. Drugs use can be proposed to elderly patients at very high risk. Diagnosis and management of osteoporosis in the young can be challenging, in particular in the absence of a manifest secondary cause. Young adults with low bone mineral density (BMD) do not necessarily have osteoporosis and it is important to avoid unnecessary treatment. A determination of BMD is recommended for premenopausal women who have had a fragility fracture or who have secondary causes of osteoporosis: secondary causes of excessive bone loss need to be excluded and treatment should be targeted. Adequate calcium, vitamin D, and a healthy lifestyle should be recommended. In the absence of fractures, conservative management is generally sufficient, but in rare cases, such as chemotherapy-induced osteoporosis, antiresorptive medication can be used. Osteoporosis in young men is most often of secondary origin and hypogonadism is a major cause; testosterone replacement therapy will improve BMD in these patients. Diabetes is characterized by major alterations in bone quality, implying that medical therapy should be started sooner than for other causes of osteoporosis. Primary hyperparathyroidism, hyperthyroidism, Cushing's syndrome and growth hormone deficiency or excess affect cortical bone more often than trabecular bone.

Ex Vivo Assessment of Cortical Bone Properties Using Low-Frequency Ultrasonic Guided Waves

The early diagnosis of osteoporosis through bone quality assessment is a major public health challenge. Research in axial transmission using ultrasonic guided waves has shown the method to be sensitive to the geometrical and mechanical properties of the cortical layer in long bones. However, because of the asymmetric nature of cortical bone, the introduction of a more elaborate numerical model than the analytical plate and cylinder models, as well as its inversion, continues to be challenging. The aim of this article is, therefore, to implement a bone-like geometry using semianalytical finite-element (SAFE) modeling to perform the inverse characterization of ex vivo radii at low frequencies (< 60 kHz). Five cadaveric radiuses were taken from donors aged between 53 and 88 and tested using a typical axial transmission configuration at the middle of the diaphysis. The dispersion curves of the propagating modes were measured experimentally and then systematically compared with the solutions obtained with the SAFE method. For each sample, four parameters were estimated using a parameter identification procedure: 1) the bulk density; 2) the thickness; 3) the outer diameter; and 4) a shape factor (SF). The results showed a moderate agreement between the predicted bulk density and the average voxel value calculated from X-ray computed tomography images. Furthermore, a good agreement was observed between the geometrical parameters (thickness, outer diameter, and SF) and the reference images.

The Association between First Fractures Sustained during Childhood and Adulthood and Bone Measures in Young Adulthood

OBJECTIVE

To describe the association between fractures sustained at different stages of growth and bone measures in early adulthood.

STUDY DESIGN

Participants (n = 201) in southern Tasmania were at birth at a higher risk of sudden infant death syndrome; they were followed to age 25. Outcomes were areal bone mineral density at the spine, hip, and total body (by dual-energy x-ray absorptiometry) and trabecular and cortical bone measures at the radius and tibia (by high-resolution peripheral quantitative computed tomography). Fractures were self-reported and confirmed by radiographs at 8, 16, and 25 years of age. Multivariable linear regression was used to analyze the association of the occurrence of prepubertal (<9 years of age), pubertal (9-16 years of age), and postpubertal (17-25 years of age) fractures with all bone measures.

RESULTS

Over 25 years, 99 participants had at least 1 fracture. For high-resolution peripheral quantitative computed tomography measures at age 25, prepubertal fractures were negatively associated with cortical and trabecular volumetric bone mineral density and most microarchitecture measures at both the tibia and radius. Prepubertal fractures had a significant association with smaller increase of areal bone mineral density from age 8 to 16 years and at 25 years of age compared with participants with no fractures. Pubertal fractures had no association with any bone measures and postpubertal fractures were only associated with a lower trabecular number at the tibia.

CONCLUSIONS

Prepubertal fractures are negatively associated with areal bone mineral density increases during growth and high-resolution peripheral quantitative computed tomography bone measures in young adulthood. There is little evidence that fractures occurring from age 8 years onward with bone measures in young adulthood, implying that prepubertal fractures may be associated with bone deficits later in life.

Metacarpal Indices and Their Association with Fracture in South African Children and Adolescents

This prospective study assessed whether metacarpal indices predict fracture risk in children and adolescents. Radiogrammetry was performed at the second metacarpal midshaft on annual hand-wrist radiographs of 359 South African (SA) children aged 10-17 years. Bone length, bone width, and medullary width were measured, and the following proxies for bone strength calculated: metacarpal index (MCI), bone mineral density (BMD), section modulus (SM), stress-strain index (SSI), and slenderness index (SLI). Height and weight were measured annually. Self-reported physical activity (PA) and fracture history were obtained at ages 15 years (for the preceding 12 months) and 17 years, respectively. At 17 years, 82 (23%) participants (black, 16%; white, 42%; p < 0.001) reported a previous fracture. None of the bone measures or indices were associated with fracture in black participants. In white females, after adjusting for PA, a 1 standard deviation (SD) greater SLI doubled the fracture risk [odds ratio (OR) 2.08; 95% confidence interval (CI) 1.08, 3.98]. In white males, a 1 SD greater BMD was associated with a 2.62-fold increase in fracture risk (OR 3.62; 95% CI 1.22, 10.75), whilst a 1 SD greater SM (OR 2.29; 95% CI 1.07, 4.89) and SSI (OR 2.23; 95% CI 1.11, 4.47) were associated with a more than twofold increase in fracture risk, after height, and PA adjustment. No single index consistently predicted fracture across the four groups possibly due to ethnic and sex differences in bone geometry, muscle mass, and skeletal loading. Metacarpal radiogrammetry did not reliably predict fracture in SA children.

A multi-factorial analysis of bone morphology and fracture strength of rat femur in response to ovariectomy

BACKGROUND

Postmenopausal osteoporosis develops due to a deficiency of estrogen that causes a decrease in bone mass and changes in the macro- and micro-architectural structure of the bone, leading to the loss of mechanical strength and an increased risk of fracture. Although the assessment of bone mineral density (BMD) has been widely used as a gold standard for diagnostic screening of bone fracture risks, it accounts for only a part of the variation in bone fragility; thus, it is necessary to consider other determinants of bone strength. Therefore, we aimed to comprehensively evaluate the architectural changes of the bone that influence bone fracture strength, together with the different sensitivities of cortical and trabecular bone in response to ovariectomy (OVX).

METHODS

Bone morphology parameters were separately analyzed both in cortical and in trabecular bones, at distal-metaphysis, and mid-diaphysis of OVX rat femurs. Three-point bending test was performed at mid-diaphysis of the femurs. Correlation of OVX-induced changes of morphological parameters with breaking force was analyzed using Pearson's correlation coefficient.

RESULTS

OVX resulted in a decline in the bone volume of distal-metaphysis trabecular bone, but an increase in distal-metaphysis and mid-diaphysis cortical bone volume. Tissue mineral density (TMD) remained unchanged in both the trabecular and cortical bone of the distal metaphysis but decreased in cortical bone of the mid-diaphysis. The OVX significantly increased the breaking force at mid-diaphysis of the femurs.

CONCLUSIONS

OVX decreased the trabecular bone volume of the distal-metaphysis and increased the cortical bone volume of the distal-metaphysis and mid-diaphysis. Despite the reduction in TMD and increased cortical porosity, bone fracture strength increased in the mid-diaphysis after OVX. These results indicate that analyzing a single factor, i.e., BMD, is not sufficient to predict the absolute fracture risk of the bone, as OVX-induced bone response vary, depending on the bone type and location. Our results strongly support the necessity of analyzing bone micro-architecture and site specificity to clarify the true etiology of osteoporosis in a clinical setting.

Tibia functionality and Division II female and male collegiate athletes from multiple sports

Background

Bone strength is developed through a combination of the size and shape (architecture) of a bone as well as the bone's material properties; and therefore, no one outcome variable can measure a positive or negative adaptation in bone. Skeletal robusticity (total area/ bone length) a measure of bones external size varies within the population and is independent of body size, but robusticity has been associated with bone strength. Athletes may have similar variability in robusticity values as the general population and thus have a wide range of bone strengths based on the robustness of their bones. Therefore, the purpose of this study was to determine if an athlete's bone strength and cortical area relative to body size was dependent on robusticity. The second aim was to determine if anthropometry or muscle function measurements were associated with bone robusticity.

Methods

Bone variables contributing to bone strength were measured in collegiate athletes and a reference group using peripheral quantitative computed tomography (pQCT) at the 50% tibial site. Bone functionality was assessed by plotting bone strength and cortical area vs body size (body weight x tibial length) and robustness (total area/length) vs body size. Bone strength was measured using the polar strength-strain index (SSIp). Based on the residuals from the regression, an athlete's individual functionality was determined, and two groups were formed "weaker for size" (WS) and "stronger for size" (SS). Grip strength, leg extensor strength and lower body power were also measured.

Results

Division II athletes exhibited a natural variation in (SSIp) relative to robusticity consistent with previous studies. Bone strength (SSIp) was dependent on the robusticity of the tibia. The bone traits that comprise bone strength (SSIp) were significantly different between the SS and WS groups, yet there were minimal differences in the anthropometric data and muscle function measures between groups. A lower percentage of athletes from ball sports were "weaker for size" (WS group) and a higher percentage of swimmers were in the WS group.

Discussion

A range of strength values based on robusticity occurs in athletes similar to general populations. Bones with lower robusticity (slender) were constructed with less bone tissue and had less strength. The athletes with slender bones were from all sports including track and field and ball sports but the majority were swimmers.

Conclusions

Athletes, even after optimal training for their sport, may have weaker bones based on robusticity. Slender bones may therefore be at a higher risk for fracture under extreme loading events but also yield benefits to some athletes (swimmers) due to their lower bone mass.

Regional Differences of Densitometric and Geometric Parameters of the Third Metacarpal Bone in Coldblood Horses - pQCT Study

Introduction

The aim of the study was to analyse selected densitometric and geometric parameters in the third metacarpal bone along the long axis in horses. The densitometric parameters included the cortical and trabecular bone mineral density, while the geometric parameters included the cortical, trabecular, and total areas, strength strain index X, strength strain index Y, and the polar strength strain index.

Material and Methods

The parameters were analysed using eight sections from 10% to 80% of the length of the bone. Peripheral quantitative computed tomography was used in the study. Statistical analysis was carried out using the Friedman analysis of variance and post-hoc tests.

Results

The proximal metaphyseal region showed the highest predicted resistance to bone fractures in the transverse (back-front) plane, the distal metaphyseal region had the highest predicted resistance to transverse and torsional fractures in the transverse (side-side) plane. The cross-sectional area and the shape of the cross-section of the cortical bone of the MCIII had the highest coefficient of variation. The density of the cortical bone was least variable.

Conclusions

The cortical area and cortical bone mineral density assumed the highest values in the diaphyseal region, while the highest total area, trabecular area and trabecular bone mineral density values were obtained in the metaphyseal proximal and distal region.

Early injury to cortical and cancellous bone from induction chemotherapy for adolescents and young adults treated for acute lymphoblastic leukemia

Diminished bone density and skeletal fractures are common morbidities during and following therapy for acute lymphoblastic leukemia (ALL). While cumulative doses of osteotoxic chemotherapy for ALL have been reported to adversely impact bone density, the timing of onset of this effect as well as other changes to bone structure is not well characterized. We therefore conducted a prospective cohort study in pre-adolescent and adolescent patients (10-21years) newly diagnosed with ALL (n=38) to explore leukemia-related changes to bone at diagnosis and the subsequent impact of the first phase of chemotherapy ("Induction"). Using quantitative computerized tomography (QCT), we found that pre-chemotherapy bone properties were similar to age- and sex-matched controls. Subsequently over the one month Induction period, however, cancellous volumetric bone mineral density (vBMD) decreased markedly (-26.8%, p<0.001) with sparing of cortical vBMD (tibia -0.0%, p=0.860, femur -0.7%, p=0.290). The tibia underwent significant cortical thinning (average cortical thickness-1.2%, p<0.001; cortical area-0.4%, p=0.014), while the femur was less affected. Areal BMD (aBMD) concurrently measured by dual-energy X-ray absorptiometry (DXA) underestimated changes from baseline as compared to vBMD. Biochemical evidence revealed prevalent Vitamin D insufficiency and a net resorptive state at start and end of Induction. Our findings demonstrate for the first time that significant alterations to cancellous and cortical bone develop during the first month of treatment, far earlier during ALL therapy than previously considered. Given that osteotoxic chemotherapy is integral to curative regimens for ALL, these results provide reason to re-evaluate traditional approaches toward chemotherapy-associated bone toxicity and highlight the urgent need for investigation into interventions to mitigate this common adverse effect.

Diminished bone strength is observed in adult women and men who sustained a mild trauma distal forearm fracture during childhood

Children and adolescents who sustain a distal forearm fracture (DFF) owing to mild, but not moderate, trauma have reduced bone strength and cortical thinning at the distal radius and tibia. Whether these skeletal deficits track into adulthood is unknown. Therefore, we studied 75 women and 75 men (age range, 20 to 40 years) with a childhood (age < 18 years) DFF and 150 sex-matched controls with no history of fracture using high-resolution peripheral quantitative computed tomography (HRpQCT) to examine bone strength (ie, failure load) by micro-finite element (µFE) analysis, as well as cortical and trabecular bone parameters at the distal radius and tibia. Level of trauma (mild versus moderate) was assigned using a validated classification scheme, blind to imaging results. When compared to sex-matched, nonfracture controls, women and men with a mild trauma childhood DFF (eg, fall from standing height) had significant reductions in failure load (p < 0.05) of the distal radius, whereas women and men with a moderate trauma childhood DFF (eg, fall while riding a bicycle) had values similar to controls. Consistent findings were observed at the distal tibia. Furthermore, women and men with a mild trauma childhood DFF had significant deficits in distal radius cortical area (p < 0.05), and significantly lower dual-energy X-ray absorptiometry (DXA)-derived bone density at the radius, hip, and total body regions compared to controls (all p < 0.05). By contrast, women and men with a moderate trauma childhood DFF had bone density, structure, and strength that did not differ significantly from controls. These findings in young adults are consistent with our observations in children/adolescents with DFF, and they suggest that a mild trauma childhood DFF may presage suboptimal peak bone density, structure, and strength in young adulthood. Children and adolescents who suffer mild trauma DFFs may need to be targeted for lifestyle interventions to help achieve improved skeletal health.

Bone quality: the determinants of bone strength and fragility

Bone fragility is a major health concern, as the increased risk of bone fractures has devastating outcomes in terms of mortality, decreased autonomy, and healthcare costs. Efforts made to address this problem have considerably increased our knowledge about the mechanisms that regulate bone formation and resorption. In particular, we now have a much better understanding of the cellular events that are triggered when bones are mechanically stimulated and how these events can lead to improvements in bone mass. Despite these findings at the molecular level, most exercise intervention studies reveal either no effects or only minor benefits of exercise programs in improving bone mineral density (BMD) in osteoporotic patients. Nevertheless, and despite that BMD is the gold standard for diagnosing osteoporosis, this measure is only able to provide insights regarding the quantity of bone tissue. In this article, we review the complex structure of bone tissue and highlight the concept that its mechanical strength stems from the interaction of several different features. We revisited the available data showing that bone mineralization degree, hydroxyapatite crystal size and heterogeneity, collagen properties, osteocyte density, trabecular and cortical microarchitecture, as well as whole bone geometry, are determinants of bone strength and that each one of these properties may independently contribute to the increased or decreased risk of fracture, even without meaningful changes in aBMD. Based on these findings, we emphasize that while osteoporosis (almost) always causes bone fragility, bone fragility is not always caused just by osteoporosis, as other important variables also play a major role in this etiology. Furthermore, the results of several studies showing compelling data that physical exercise has the potential to improve bone quality and to decrease fracture risk by influencing each one of these determinants are also reviewed. These findings have meaningful clinical repercussions as they emphasize the fact that, even without leading to improvements in BMD, exercise interventions in patients with osteoporosis may be beneficial by improving other determinants of bone strength.

Pathological fractures in paediatric patients with inflammatory bowel disease

Paediatric inflammatory bowel disease (IBD), especially Crohn's disease (CD), is commonly associated with poor skeletal health, related to the direct effects of chronic inflammation, prolonged use of glucocorticoid (GC), poor nutrition, delayed puberty and low muscle mass. Low bone mineral density is commonly reported, although the prevalence of long bone fractures may not be increased in these patients. Emerging evidence however suggests that there may be an increased risk of vertebral fractures (VFs) in this group. VFs presenting at diagnosis of paediatric CD, prior to any GC exposure, have been reported, highlighting the deleterious effect of inflammation on skeletal health. This paper reviews the published literature on pathophysiology of skeletal morbidity and fractures in paediatric IBD, illustrated with a new case report of multiple VFs in a prepubertal girl with CD, soon after diagnosis, who received minimal amounts of oral GC. Optimising control of disease, addressing vitamin D deficiency, encouraging physical activity and ensuring normal growth and pubertal progression are paramount to management of bone health in these patients. Despite the lack of evidence, there may be a place for bisphosphonate treatment, especially in the presence of symptomatic pathological fractures, but this requires close monitoring by clinicians with expertise in paediatric bone health.

CONCLUSION

Chronic inflammation mediated by pro-inflammatory cytokines may have adverse effects on skeletal health in paediatric patients with IBD. The risk of vertebral fractures may be increased, even without exposure to glucocorticoid. Clinical monitoring of these patients requires careful attention to the various factors that impact on bone health.

Exploring the determinants of fracture risk among individuals with spinal cord injury

In this cross-sectional study, we found that areal bone mineral density (aBMD) at the knee and specific tibia bone geometry variables are associated with fragility fractures in men and women with chronic spinal cord injury (SCI).

INTRODUCTION

Low aBMD of the hip and knee regions have been associated with fractures among individuals with chronic motor complete SCI; however, it is unclear whether these variables can be used to identify those at risk of fracture. In this cross-sectional study, we examined whether BMD and geometry measures are associated with lower extremity fragility fractures in individuals with chronic SCI.

METHODS

Adults with chronic [duration of injury ≥ 2 years] traumatic SCI (C1-L1 American Spinal Cord Injury Association Impairment Scale A-D) reported post injury lower extremity fragility fractures. Dual-energy X-ray absorptiometry (DXA) was used to measure aBMD of the hip, distal femur, and proximal tibia regions, while bone geometry at the tibia was assessed using peripheral quantitative computed tomography (pQCT). Logistic regression and univariate analyses were used to identify whether clinical characteristics or bone geometry variables were associated with fractures.

RESULTS

Seventy individuals with SCI [mean age (standard deviation [SD]), 48.8 (11.5); 20 females] reported 19 fragility fractures. Individuals without fractures had significantly greater aBMD of the hip and knee regions and indices of bone geometry. Every SD decrease in aBMD of the distal femur and proximal tibia, trabecular volumetric bone mineral density, and polar moment of inertia was associated with fracture prevalence after adjusting for motor complete injury (odds ratio ranged from 3.2 to 6.1).

CONCLUSION

Low knee aBMD and suboptimal bone geometry are significantly associated with fractures. Prospective studies are necessary to confirm the bone parameters reported to predict fracture risk in individuals with low bone mass and chronic SCI.

Idiopathic osteoporosis in men

Over the last decade, the increasingly significant problem of osteoporosis in men has begun to receive much more attention than in the past. In particular, recent observations from large scale population studies in males led to an advance in the understanding of morphologic basis of growth, maintenance and loss of bone in men, as well as new insights about the pathophysiology and treatment of this disorder. While fracture risk consistently increases after age 65 in men (with up to 50 % of cases due to secondary etiologies), osteoporosis and fractures may also occur in young or middle aged males in the absence of an identifiable etiology. For this category (so called idiopathic osteoporosis), there are still major gaps in knowledge, particularly concerning the etiology and the clinical management. This article provides a summary of recent developments in the acquisition and maintenance of bone strength in men, as well as new insights about the pathogenesis, diagnosis, and treatment of idiopathic osteoporosis.

X-ray-verified fractures are associated with finite element analysis-derived bone strength and trabecular microstructure in young adult men

It has been suggested that fracture during childhood could be a predictor of low peak bone mass and thereby a potential risk factor for osteoporosis and fragility fractures later in life. The aim of this cross-sectional, population-based study was to investigate whether prevalent fractures, occurring from birth to young adulthood, were related to high-resolution peripheral quantitative computed tomography (HR-pQCT)-derived trabecular and cortical microstructure, as well as bone strength estimated by finite element (FEA) analysis of the radius and tibia in 833 young adult men around the time of peak bone mass (ages 23 to 25 years). In total, 292 subjects with prevalent X-ray-verified fractures were found. Men with prevalent fractures had lower trabecular bone volume fraction (BV/TV) at the radius (5.5%, p < 0.001) and tibia (3.7%, p < 0.001), as well as lower cortical thickness (5.1%, p < 0.01) and cortical cross-sectional area (4.1%, p < 0.01) at the tibia. No significant differences were seen for the cortical porosity or mean pore diameter. Using a logistic regression model (including age, smoking, physical activity, calcium intake, height, and weight as covariates), every SD decrease of FEA-estimated failure load was associated with an increased prevalence of fractures at both the radius (odds ratio [OR] 1.22 [1.03-1.45]) and tibia (OR 1.32 [1.11-1.56]). Including dual-energy X-ray absorptiometry (DXA)-derived radius areal bone mineral density (aBMD), cortical thickness, and trabecular BV/TV simultaneously in a logistic regression model (with age, smoking, physical activity, calcium intake, height, and weight as covariates), BV/TV was inversely and independently associated with prevalent fractures (OR 1.28 [1.04-1.59]), whereas aBMD and cortical thickness were not (OR 1.19 [0.92-1.55] and OR 0.91 [0.73-1.12], respectively). In conclusion, prevalent fractures in young adult men were associated with impaired trabecular BV/TV at the radius, independently of aBMD and cortical thickness, indicating that primarily trabecular bone deficits are of greatest importance for prevalent fracture in this population.

Impaired bone microarchitecture at the distal radius in older men with low muscle mass and grip strength: the STRAMBO study

The aim was to study the association between bone microarchitecture and muscle mass and strength in older men. Volumetric bone mineral density (vBMD) and bone microarchitecture were assessed in 810 men aged ≥60 years at the distal radius by high-resolution peripheral computed tomography (HR-pQCT). Areal bone mineral density (aBMD) and appendicular muscle mass (ASM) were assessed by dual-energy X-ray absorptiometry (DXA). Relative ASM of the upper limbs (RASM-u.l.) was calculated as ASM of the upper limbs/(height)(2). Grip strength was measured by dynanometry. In multivariable models, men in the lowest RASM-u.l. quartile had lower cross-sectional area (CSA), cortical area (Ct.Ar), cortical thickness (Ct.Th), and trabecular area (Tb.Ar) at distal radius compared with men in the highest quartile. The trends remained significant after adjustment for grip strength. Men in the lowest quartile of the normalized grip strength (grip strength/[height](2)) had lower aBMD, total vBMD, Ct.Ar, Ct.Th, Tb.vBMD, and Tb.N, and higher Tb.Sp and Tb.Sp.SD. The associations for Ct.Ar, total vBMD, Ct.Th, Tb.vBMD, and Tb.Sp remained significant after adjustment for RASM-u.l. In the models including RASM-u.l. and normalized grip strength, CSA and Tb.Ar were associated with RASM-u.l. but not with the strength. Lower Ct.Th, Tb.vBMD, and Tb.N were associated with lower grip strength but not with RASM-u.l. Lower Ct.Ar was associated with lower grip strength and with lower RASM-u.l. In conclusion, in older men, low RASM-u.l. and low grip strength are associated with poor cortical and trabecular microarchitecture partly independently of each other, after adjustment for confounders.

Comparison of cortical bone measurements between pQCT and HR-pQCT

The primary purpose of this study was to determine the accuracy of tibial cortical thickness measurements derived from peripheral quantitative computed tomography (pQCT) with analysis based on the circular ring model, using high-resolution peripheral quantitative computed tomography (HR-pQCT) (isotopic voxel size of 82 μm) as a gold standard. The secondary objective was to evaluate whether the accuracy of the pQCT-based estimates of cortical thickness (CTh), cortical area (CoA), cortical density (CDen), and total area (TotA) improve with alterations of voxel size from the standard 0.5-0.2mm. Fifteen dry tibia specimens were immersed in saline in a sealed cylinder and scanned 22.5mm from the distal tibia plateau using pQCT and HR-pQCT. pQCT yielded higher values for CTh and CDen and lower values for CoA. The differences between imaging techniques increased as the average CTh increased. No systematic bias was observed for CDen, CoA, and TotA. Similar differences were found between pQCT with voxel size 0.2mm and HR-pQCT. Significant correlations were observed for CTh (R=0.97, p ≤ 0.0001), CDen (R=0.99, p ≤ 0.0001), CoA (R=0.98, p ≤ 0.0001), and TotA (R=1.0, p ≤ 0.0001) when pQCT- and HR-pQCT-derived values were compared irrespective of which voxel size was used. Measurement variability between the imaging techniques was evident. Future studies aimed at examining cortical structure with pQCT should note that there are differences between the 2 techniques.

Sexual dimorphism of femoral neck cross-sectional bone geometry in athletes and non-athletes: a hip structural analysis study

The characterisation of bone geometry in male and female athletes may increase our understanding of how physical loading may enhance bone strength in both sexes. This study investigated sexual dimorphism in hip geometry of athletes and age- and sex-matched non-athletes. Dual energy X-ray absorptiometry of the left proximal femur was performed in 62 male (n = 31; 30.2 ± 4.6 years) and female (n = 31; 27.9 ± 5.2 years) competitive endurance runners, and 36 male (n = 18; 28.7 ± 5.8 years) and female (n = 18; 29.1 ± 5.3 years) non-athletes. The hip structural analysis programme determined areal bone mineral density (aBMD), bone area (BA), hip axis length, cross-sectional area (CSA), and cross-sectional moment of inertia (CSMI) of the femoral neck. Strength indices were derived from the femoral strength index (FSI) (Yoshikawa et al., J Bone Miner Res 9:1053-1064, 1994). Despite similar size-adjusted aBMD, sexual dimorphism was apparent for BA, CSA and CSMI, with superior values in men compared to women (P < 0.01). FSI was greater in male and female athletes than non-athletes (P < 0.01). From all groups, results in male athletes inferred greatest resistance to axial (CSA) and bending loads (FSI). Estimates of bone strength (FSI) were greater in female athletes than male and female non-athletes, supporting the osteogenic value of regular loading of the hip.

Single nucleotide polymorphisms in sFRP4 are associated with bone and body composition related parameters in Danish but not in Belgian men

The senescence accelerated mouse P6 (SAMP6) has a low bone mass and has previously shown to be a good model for senile osteoporosis in humans. In addition to a reduced bone mass, SAMP6 mice are obese and have hyperlipidemia. Using positional cloning and expression studies, an increased expression of sfrp4 was found in these mice. SFRP4 is a modulator of the Wnt signalling pathway. This pathway has been previously shown to be involved in regulating bone mass. Additional evidence that sFRP4 has an influence on BMD was delivered by linkage and association studies mostly performed in Asian populations. Based on these data we decided to perform an association study between common variants in sFRP4, BMD, hip geometry parameters and body composition parameters in a population consisting of 1383 Danish men (783 aged 20-29 years; 600 aged 60-74 years). Afterwards we tried to replicate the significant results in a population of 994 Belgian men. In the Danish population we found 6 SNPs associated with BMD at the hip and/or femoral neck. Furthermore, all 6 SNPs were associated with several hip geometry parameters. The homozygous presence of the minor allele resulted for all SNPs (except rs4720265) in a decrease in bone density and bone strength. Finally, we observed in the Danish population age specific associations with height and fat mass. In the Belgian population we tried to replicate the results of three SNPs with BMD and body composition parameters. Unfortunately, we were not able to replicate the results found in the Danish cohort but we found one SNP (rs2598116) associated with height. In conclusion, genetic variation in sFRP4 has an influence on hip fracture risk, percentage body fat and height in a Danish male population. However, we were unable to replicate these results in an independent Belgian population.

Poor trabecular microarchitecture in male current smokers: the cross-sectional STRAMBO study

Current smoking (but not past smoking) is associated with higher risk of fracture independent of areal bone mineral density (aBMD); however, the pathophysiologic mechanism underlying this association is not clear. In 810 men aged 60-87, aBMD was measured by dual-energy X-ray absorptiometry. Bone microarchitecture at the distal radius and distal tibia was assessed by high-resolution peripheral quantitative computed tomography using the Xtreme CT Scanco device. Current smokers (n = 47) had lower trabecular volumetric density (Dtrab), lower trabecular number (TbN), more heterogenous trabecular network (higher trabecular spacing standard deviation [TbSpSD]), as well as higher urinary deoxypyridinoline and higher C-reactive protein levels in comparison with 261 men who never smoked (adjusted for age, weight, height, time spent outdoors, physical activity, and intake of alcohol, caffeine, and calcium). Abnormal values (lower Dtrab and TbN, higher TbSpSD, deoxypyridinoline, and C-reactive protein) were found mainly in 21 current smokers who smoked eight or more cigarettes per day. Cortical parameters and aBMD did not differ from the never-smokers. In 502 former smokers, aBMD and all bone microarchitectural parameters did not differ from the never-smokers. At the tibia (not radius), Dtrab decreased, whereas TbSpSD slightly increased across quartiles of smoking intensity (number of pack-years). In conclusion, older men who are moderate current smokers have poor trabecular (but not cortical) microarchitecture, which is not reflected by a decrease in aBMD.

Peripheral quantitative computed tomography: optimization of reproducibility measures of bone density, geometry, and strength at the radius and tibia

The aim of this study was to determine the reproducibility for in vivo measurements at the radius and tibia for trabecular and cortical parameters, bone geometry, and bone strength indices with the peripheral quantitative computed tomography (pQCT) XCT 3000. We performed 3 repeated scans within 2mo at the radius (N=18) and tibia (N=16) on healthy, premenopausal women, aged 22-35 yrs and report precision measures including %coefficient of variation (%CV) and least significant changes (LSCs). For the radius, we studied 2 sections (4% and 33% of total length) and for the tibia, 3 sections (4%, 38%, and 66% of total length). Reproducibility for radius at 33% and tibia at every site was good (%CV ranged from 0.02% to 2.19%). The precision error for the distal 4% radius was, however, higher. The reproducibility at the distal radius improved when we considered only the scans with a change of ± 10mm(2) in the radius total area at this site (%CV from 0.87% to 2.25%). This study showed that, when follow-up measurements are carefully obtained, pQCT yields excellent reproducibility at both the radius and tibia. These precision errors, in conjunction with changes in LSC for the pQCT measures, are useful for research and potential clinical applications.

Cross-sectional analysis of the association between fragility fractures and bone microarchitecture in older men: the STRAMBO study

Areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) identifies 20% of men who will sustain fragility fractures. Thus we need better fracture predictors in men. We assessed the association between the low-trauma prevalent fractures and bone microarchitecture assessed at the distal radius and tibia by high-resolution peripheral quantitative computed tomography (HR-pQCT) in 920 men aged 50 years of older. Ninety-eight men had vertebral fractures identified on the vertebral fracture assessment software of the Hologic Discovery A device using the semiquantitative criteria, whereas 100 men reported low-trauma peripheral fractures. Men with vertebral fractures had poor bone microarchitecture. However, in the men with vertebral fractures, only cortical volumetric density (D.cort) and cortical thickness (C.Th) remained significantly lower at both the radius and tibia after adjustment for aBMD of ultradistal radius and hip, respectively. Low D.cort and C.Th were associated with higher prevalence of vertebral fractures regardless of aBMD. Severe vertebral fractures also were associated with poor trabecular microarchitecture regardless of aBMD. Men with peripheral fractures had poor bone microarchitecture. However, after adjustment for aBMD, all microarchitectural parameters became nonsignificant. In 15 men with multiple peripheral fractures, trabecular spacing and distribution remained increased after adjustment for aBMD. Thus, in men, vertebral fractures and their severity are associated with impaired cortical bone, even after adjustment for aBMD. The association between peripheral fractures and bone microarchitecture was weaker and nonsignificant after adjustment for aBMD. Thus bone microarchitecture may be a determinant of bone fragility in men, which should be investigated in prospective studies.

Lower trabecular volumetric BMD at metaphyseal regions of weight-bearing bones is associated with prior fracture in young girls

Understanding the etiology of skeletal fragility during growth is critical for the development of treatments and prevention strategies aimed at reducing the burden of childhood fractures. Thus we evaluated the relationship between prior fracture and bone parameters in young girls. Data from 465 girls aged 8 to 13 years from the Jump-In: Building Better Bones study were analyzed. Bone parameters were assessed at metaphyseal and diaphyseal sites of the nondominant femur and tibia using peripheral quantitative computed tomography (pQCT). Dual-energy X-ray absorptiometry (DXA) was used to assess femur, tibia, lumbar spine, and total body less head bone mineral content. Binary logistic regression was used to evaluate the relationship between prior fracture and bone parameters, controlling for maturity, body mass, leg length, ethnicity, and physical activity. Associations between prior fracture and all DXA and pQCT bone parameters at diaphyseal sites were nonsignificant. In contrast, lower trabecular volumetric BMD (vBMD) at distal metaphyseal sites of the femur and tibia was significantly associated with prior fracture. After adjustment for covariates, every SD decrease in trabecular vBMD at metaphyseal sites of the distal femur and tibia was associated with 1.4 (1.1-1.9) and 1.3 (1.0-1.7) times higher fracture prevalence, respectively. Prior fracture was not associated with metaphyseal bone size (ie, periosteal circumference). In conclusion, fractures in girls are associated with lower trabecular vBMD, but not bone size, at metaphyseal sites of the femur and tibia. Lower trabecular vBMD at metaphyseal sites of long bones may be an early marker of skeletal fragility in girls.

Functional genomics complements quantitative genetics in identifying disease-gene associations

An ultimate goal of genetic research is to understand the connection between genotype and phenotype in order to improve the diagnosis and treatment of diseases. The quantitative genetics field has developed a suite of statistical methods to associate genetic loci with diseases and phenotypes, including quantitative trait loci (QTL) linkage mapping and genome-wide association studies (GWAS). However, each of these approaches have technical and biological shortcomings. For example, the amount of heritable variation explained by GWAS is often surprisingly small and the resolution of many QTL linkage mapping studies is poor. The predictive power and interpretation of QTL and GWAS results are consequently limited. In this study, we propose a complementary approach to quantitative genetics by interrogating the vast amount of high-throughput genomic data in model organisms to functionally associate genes with phenotypes and diseases. Our algorithm combines the genome-wide functional relationship network for the laboratory mouse and a state-of-the-art machine learning method. We demonstrate the superior accuracy of this algorithm through predicting genes associated with each of 1157 diverse phenotype ontology terms. Comparison between our prediction results and a meta-analysis of quantitative genetic studies reveals both overlapping candidates and distinct, accurate predictions uniquely identified by our approach. Focusing on bone mineral density (BMD), a phenotype related to osteoporotic fracture, we experimentally validated two of our novel predictions (not observed in any previous GWAS/QTL studies) and found significant bone density defects for both Timp2 and Abcg8 deficient mice. Our results suggest that the integration of functional genomics data into networks, which itself is informative of protein function and interactions, can successfully be utilized as a complementary approach to quantitative genetics to predict disease risks. All supplementary material is available at http://cbfg.jax.org/phenotype.

Many recent efforts to understand the genetic origins of complex diseases utilize statistical approaches to analyze phenotypic traits measured in genetically well-characterized populations. While these quantitative genetics methods are powerful, their success is limited by sampling biases and other confounding factors, and the biological interpretation of results can be challenging since these methods are not based on any functional information for candidate loci. On the other hand, the functional genomics field has greatly expanded in past years, both in terms of experimental approaches and analytical algorithms. However, functional approaches have been applied to understanding phenotypes in only the most basic ways. In this study, we demonstrate that functional genomics can complement traditional quantitative genetics by analytically extracting protein function information from large collections of high throughput data, which can then be used to predict genotype-phenotype associations. We applied our prediction methodology to the laboratory mouse, and we experimentally confirmed a role in osteoporosis for two of our predictions that were not candidates from any previous quantitative genetics study. The ability of our approach to produce accurate and unique predictions implies that functional genomics can complement quantitative genetics and can help address previous limitations in identifying disease genes.