Femoral Neck Bone Strength Research Articles

Association of bone-related biomarkers with femoral neck bone strength

BackgroundFemoral neck fractures are the worst consequence of osteoporosis (OP), and its early prevention and treatment have become a public health problem. This study aims to investigate the relationship of bone-related biomarkers, femoral neck bone mineral density (BMD) and maximum load (Lmax), selecting the indicator which can reflect femoral neck bone loss and reduced bone strength.MethodsA total of 108 patients were recruited from January 2017 to December 2019. Venous blood samples were collected from patients before total hip replacement, and femoral neck samples were collected during the surgery. Femoral neck BMD, femoral neck Lmax, bone-related markers (serum levels of bone turnover markers, protein expression of type I collagen (COL-I) and osteopontin (OPN) in femoral neck) were all measured and analyzed.ResultsThe expression of COL-I in femoral neck were significantly decreased, whereas other markers were all significantly increased with the decreasing of femoral neck BMD and Lmax (P < 0.05). Among them, serum C-terminal telopeptide of type I collagen (CTX) levels and OPN expression of femoral neck were increased in osteopenia. In multiple linear regression analysis, CTX and OPN were both negatively correlated with femoral neck BMD and Lmax, and they were independent factors of femoral neck BMD and Lmax, whereas COL-I was independent factor affecting Lmax (P < 0.05). Besides, CTX was negatively correlated with COL-I (β = -0.275, P = 0.012) and positively correlated with OPN (β = 0.295, P = 0.003).ConclusionsCompared with other indicators, serum CTX was more sensitive to differences in bone mass and bone strength of femoral neck, and could be considered as surrogate marker for OPN and COL-I.Early measurement of CTX could facilitate the diagnosis of osteopenia and provide a theoretical basis for delaying the occurrence of femoral neck OP and fragility fractures.

The Efficacy of PTH and Abaloparatide to Counteract Immobilization-Induced Osteopenia Is in General Similar.

Immobilization results in a substantial bone loss and increased fracture risk. Powerful bone anabolic therapies are necessary to counteract the bone loss and reduce fracture risk during periods with immobilization. Intermittent parathyroid hormone 1−34 (PTH) (teriparatide) and PTH related peptide analog abaloparatide (ABL) are potent bone anabolic therapies acting through the same receptor, but induce different durations of signaling response. We investigated the efficacy of PTH or ABL in preventing immobilization-induced bone loss in rats in a direct mole-to-mole comparison. Immobilization was achieved by injecting botulinum toxin type A (BTX) into the right hindlimb musculature. Sixty 14-week-old female Wistar rats were allocated to the following groups: Baseline, Control, BTX, BTX + PTH (80 μg/kg/day), and BTX + ABL (77 μg/kg/day). Immobilization resulted in a substantial and significant reduction in bone mineral density (aBMD), metaphyseal and epiphyseal trabecular bone volume fraction (BV/TV) and trabecular thickness (Tb.Th), metaphyseal trabecular number (Tb.N), and femoral neck bone strength. Both PTH and ABL prevented the immobilization-induced decrease in aBMD, metaphyseal and epiphyseal Tb.Th, and metaphyseal Tb.N. In addition, PTH rescued the reduction in metaphyseal BV/TV and femoral neck strength, while ABL did not. However, the effect of PTH and ABL did not differ significantly for serum calcium, aBMD, metaphyseal, and epiphyseal BV/TV, Tb.Th, or Tb.N. In conclusion, in a mole-to-mole comparison the efficacy of PTH and ABL is similar in counteracting immobilization-induced reduction in bone mineral density, deterioration in trabecular microarchitecture, and decrease in bone strength.

Hip geometry on femoral neck bone strength; a review article

Introduction: Low bone strength of the hip, which depends on both bone mass and bone geometry, leads to risk for fragility hip fracture. Anatomical adaptations of the proximal femoral structure are important to maintain higher bone strength because they predict the fracture risk independent of bone mass. Therefore, it is crucial to evaluate the bone strength of proximal femur to predict the likelihood of fragility fracture risk based on both bone mass and geometric adaptations, as well as the biomechanical strength of femoral neck (FN). Aim: To discuss the literature on geometric indices and biomechanical indices of the proximal femur to estimate FN strength. Material and methods: Dual energy xray absorptiometry (DXA) based hip structural analysis (HSA) technique derived indices of FN geometric adaptations and biomechanical strength at FN and their impact on FN bone strength were explored using the existing literature. Bone mineral content (BMC, gram) and areal bone mineral density (aBMD, g/cm2) can be measured using the HAS technique. The simple hip geometric indices such as hip axis length (HAL), femoral neck length (FNL), neck shaft angle (NSA), FN diameters, FN width and biomechanical indices such as cross-sectional moment of inertia (CSMI, cm4), section modulus (Z, cm3) and cross-sectional area (CSA, cm2) can be estimated using the HSA technique to estimate FN bone strength. Conclusion: Estimation of FN bone strength by HSA based geometric adaptations and biomechanical strength indices provides better understanding of bone strength at FN. HAL and FN bone size with BMD provide better hip fracture predictability.

Disuse-induced loss of bone mineral density and bone strength is attenuated by post-lactational bone gain in NMRI mice.

Lactation in mice is associated with a substantial bone loss, which almost completely recovers within four weeks after weaning. The post-lactational recovery mechanism is considered one of the most potent physiological bone anabolic responses in adult life. The aim of the study was to investigate whether the post-lactational bone anabolic response could attenuate or prevent a disuse bone loss induced by botulinum toxin (BTX) in mice. Eighty-one 10-week-old female NMRI mice were divided into the following groups: Pregnant, Lactation, Recovery + Vehicle, Recovery + BTX, No Lactation, No Lactation + Vehicle, No Lactation + BTX, and Virgin Control. The mice lactated for 12 days before weaning followed by 21 days of recovery. On the last day of lactation, disuse was induced by injecting 2 IU of BTX per 100 g body weight into the right hind limb. Mechanical testing, μCT, and dynamic bone histomorphometry were performed on the right femur. Lactation induced a loss of aBMD and of vBMD, Tb.Th, and MS/BS at the distal femoral metaphysis, Ct.Th and bone strength at the femoral mid-diaphysis, and femoral neck bone strength compared to pregnant mice. This bone loss was partly or fully reversed after 21 days of recovery from lactation. In non-lactating mice, BTX resulted in a loss of aBMD and of vBMD, BV/TV, Tb.Th, MS/BS, and BFR/BS at the distal femoral metaphysis, Ct.Th at the femoral mid-diaphysis, and femoral neck bone strength compared to ambulating non-lactating mice. The post-lactational response attenuated the BTX-induced loss of aBMD, Tb.Th, Ct.Th, trabecular MS/BS and BFR/BS, and femoral neck bone strength indicating that the recovery after lactation had reduced the negative effects of BTX on these parameters. In contrast, it was unable to counteract the loss of BV/TV and vBMD at the distal femoral metaphysis. In conclusion, the post-lactational response attenuated disuse-induced decrease of femoral aBMD, femoral neck bone strength, trabecular and cortical thickness, and trabecular MS/BS, BFR/BS, while it could not counteract the disuse-induced loss of BV/TV and vBMD.

Potential bone fragility of mid-shaft atypical femoral fracture: Biomechanical analysis by a CT-based nonlinear finite element method

IntroductionThe authors previously reported a CT-based nonlinear finite element analysis (nonlinear CT/FEA) model to investigate loading stress distribution in the femoral shaft of patients with atypical femoral fractures (AFFs). This showed that stress distribution, influenced primarily by femoral bowing, may determine the location of AFF. Here, we demonstrate the locational characteristics associated with AFFs in an Asian, specifically Japanese, population regarding bone strength. This is the second report from our multicentre research project suggesting a possible new concept of diagnostic criteria or treatment according to AFF subtype. Patients and methodsA multicentre prospective study was conducted at 12 hospitals in Japan from August 2015 through June 2018. We recruited three study groups composed of elderly females over the age of 60 years—the mid-shaft AFF group (n = 14; 80.0 ± 6.5 years), the subtrochanteric AFF group (n = 15; 73.9 ± 6.8 years), and the control group who had sustained unilateral hip fracture (n = 21; 82.1 ± 7.1 years)—and analysed femoral neck bone density and strength. Bone strength of the femoral neck was predicted with an evaluation method using nonlinear CT/FEA in both standing and falling configuration. ResultsFemoral neck bone density and strength were significantly higher in the subtrochanteric AFF group compared with the mid-shaft AFF and control groups (p < 0.0001). No significant difference was seen in bone strength between the mid-shaft AFF and control groups (standing, p = 0.7616; falling, p = 0.3803). ConclusionsAFF has different features, in terms of bone strength, depending on fracture location. At the very least, Japanese patients with mid-shaft AFF could be at high risk of hip fracture because of bone fragility, in contrast to the firm bone of subtrochanteric AFF. For internal fixation of mid-shaft AFF using an IM nail, cervical screw insertion toward the femoral head might be recommended to prevent possible hip fracture.

Circulating Levels of Inflammation and the Effect on Exercise-Related Changes in Bone Mass, Structure and Strength in Middle-Aged and Older Men.

Chronic, low-grade systematic inflammation has been associated with bone loss and increased fracture risk. We previously reported that exercise improved femoral neck bone mineral density (BMD), geometry and strength and lumbar spine trabecular BMD in middle-aged and older men, but had no effect on markers of inflammation. The aim of this study was to examine the association between basal inflammatory status and the adaptive skeletal responses to exercise. Secondary analysis was completed on 91 men aged 50-79years who participated in an 18-month program of progressive resistance training plus weight-bearing impact exercise (3day/week) with and without additional calcium-vitamin D3. Markers of inflammation (serum hs-CRP, TNF-α and IL-6) and DXA and QCT-derived BMD, bone structure and strength at the lumbar spine and proximal femur were measured at baseline and 18months. Multiple regression was used to assess associations between skeletal changes and both baseline levels of individual inflammatory markers and a composite inflammatory index derived from the number of markers categorized into the highest tertile. Baseline serum hs-CRP, TNFα and IL-6 and the composite inflammatory index score were not associated with skeletal changes at any site after adjusting for age, change in lean mass, disease(s)/medication use and adherence to the exercise intervention. In conclusion, this study indicates that basal inflammatory status does not influence the osteogenic response to exercise training in healthy middle-aged and older men.

A soluble activin type IIA receptor mitigates the loss of femoral neck bone strength and cancellous bone mass in a mouse model of disuse osteopenia.

Disuse causes a rapid and substantial bone loss distinct in its pathophysiology from the bone loss associated with cancers, age, and menopause. While inhibitors of the activin-receptor signaling pathway (IASPs) have been shown to prevent ovariectomy- and cancer-induced bone loss, their application in a model of disuse osteopenia remains to be tested. Here, we show that a soluble activin type IIA receptor (ActRIIA-mFc) increases diaphyseal bone strength and cancellous bone mass, and mitigates the loss of femoral neck bone strength in the Botulinum Toxin A (BTX)-model of disuse osteopenia in female C57BL/6J mice. We show that ActRIIA-mFc treatment preferentially stimulates a dual-effect (anabolic-antiresorptive) on the periosteal envelope of diaphyseal bone, demonstrating in detail the effects of ActRIIA-mFc on cortical bone. These observations constitute a previously undescribed feature of IASPs that mediates at least part of their ability to mitigate detrimental effects of unloading on bone tissue. The study findings support the application of IASPs as a strategy to combat bone loss during disuse.

Evaluation of 48-week daily teriparatide treatment with DXA-based hip structure analysis in elderly female patients with rheumatoid arthritis

Objectives: The purposes of the present study were to clarify the effects on the structural strength of the femoral neck bones in elderly RA patients being treated with teriparatide.Methods: Fifty female RA patients were enrolled. We investigated the bone mineral density (BMD) of the lumbar vertebrae and femoral neck, and performed a hip structure analysis (HSA) using dual-energy X-ray absorptiometry (DXA) during a 48-week treatment with teriparatide (20 µg/day).Results: The mean age was 74.5 years, and the mean duration of RA was 23.0 years. The percent change in the lumbar BMD was +5.8% (mean, 24 weeks, p<0.01) and +8.0% (mean, 48 weeks, p<0.01). On the other hand, there were no statistically significant differences in the femoral neck BMD changes at either 24 or 48 weeks (p=0.72 and p=0.56, respectively). The percentage change from baseline in the buckling ratio of the femoral neck was -16.8% (improve) at 48 weeks (p=0.004), because of cortical thickening. There were no significant differences in the section modulus (SM) or cross-sectional area (CSA).Conclusions: The femoral neck bone strength increased with teriparatide treatment in elderly female RA patients.

Adult bone strength of children from single-parent families: the Midlife in the United States Study.

Bone health may be negatively impacted by childhood socio-environmental circumstances. We examined the independent associations of single-parent childhood and parental death or divorce in childhood with adult bone strength indices. Longer exposure to a single-parent household in childhood was associated with lower bone strength in adulthood. Because peak bone mass is acquired during childhood, bone health may be negatively impacted by childhood socio-environmental disadvantage. The goal of this study was to determine whether being raised in a single-parent household is associated with lower bone strength in adulthood. Using dual-energy X-ray absorptiometry data from 708 participants (mean age 57 years) in the Midlife in the United States Biomarker Project, we examined the independent associations of composite indices of femoral neck bone strength relative to load (in three failure modes: compression, bending, and impact) in adulthood with the experience of single-parent childhood and parental death or divorce in childhood. After adjustment for gender, race, menopause transition stage, age, and body mass index, each additional year of single-parent childhood was associated with 0.02 to 0.03 SD lower indices of adult femoral neck strength. In those with 9-16 years of single-parent childhood, the compression strength index was 0.41 SD lower, bending strength index was 0.31 SD lower, and impact strength index was 0.25 SD lower (all p values < 0.05). In contrast, parental death or divorce during childhood was not by itself independently associated with adult bone strength indices. The magnitudes of these associations were unaltered by additional adjustment for lifestyle factors and socioeconomic status in childhood and adulthood. Independent of parental death or divorce, growing up in a single-parent household is associated with lower femoral neck bone strength in adulthood, and this association is not entirely explained by childhood or adult socioeconomic conditions or lifestyle choices.

Childhood socioeconomic status and adult femoral neck bone strength: Findings from the Midlife in the United States Study

PurposeBone acquisition in childhood impacts adult bone mass, and can be influenced by childhood socioeconomic conditions. Socioeconomic status is also associated with body weight which affects the load that bone is exposed to in a fall. We hypothesized that socioeconomic advantage in childhood is associated with greater bone strength relative to load in adulthood. MethodsHip dual x-ray absorptiometry scans from 722 participants in the Midlife in the United States Study were used to measure femoral neck size and bone mineral density, and combined with body weight and height to create composite indices of femoral neck strength relative to load in different failure modes: compression, bending, and impact. A childhood socioeconomic advantage score was created for the same participants from parental education, self-rated financial status relative to others, and not being on welfare. Multiple linear regression was used to determine the association of childhood socioeconomic advantage with femoral neck composite strength indices, stratified by gender and race (white/non-white), and adjusted for study site, age, menopause status in women, education, and current financial advantage. ResultsChildhood socioeconomic advantage was independently associated with higher indices of all three composite strength indices in white men (adjusted standardized effect sizes, 0.19 to 0.27, all p values<0.01), but not in the other three race/gender groups. Additional adjustment for adult obesity, physical activity in different life stages, smoking, and heavy drinking over the life-course significantly attenuated the associations in white men. ConclusionsSocioeconomic disadvantage in childhood is associated with lower hip strength relative to load in white men, and these influences are dampened by healthy lifestyle choices.

Femoral Neck Bone Strength Estimated by Hip Structural Analysis (HSA) in Swedish Caucasians Aged 6–90 Years

Dual-energy X-ray absorptiometry hip scans of 1,760 population-based Caucasians, 599 girls and 642 boys aged 6-19 years and 270 women and 249 men aged 20-90 years, were analyzed with the hip structural analysis (HSA) software to present age- and sex-specific normative HSA data of the femoral neck (FN). Measured traits included bone mineral density (BMD), cross-sectional area (CSA), section modulus (Z), periosteal diameter (PD), endosteal diameter (ED), cortical thickness (CT), and cross-sectional moment of inertia (CSMI). When plotting the measured traits versus age, the curves increased with higher ages until statistically significant break points were reached, for all traits at age 17 in girls and age 19 in boys. After the break points, PD and ED increased with higher ages but, as ED increased more than PD, BMD and CT decreased significantly with higher ages. The decline in BMD was counteracted by the increase in bone size so that there was only a nonstatistically significant decrease in bone strength, estimated as Z and CSMI, from break point to age 90. The partial preservation of bone strength was more obvious in men than in women as the decline in BMD was higher in women than in men, while the expansion in PD was larger in men than in women. The sex difference in the normative FN bone strength data seems to be related to sex discrepancies in the development of both bone mass and geometrical parameters during both growth and adulthood.

Quantitative computed tomographic assessment of the effects of 24 months of teriparatide treatment on 3D femoral neck bone distribution, geometry, and bone strength: Results from the EUROFORS study

We studied the changes in bone distribution, geometry, and bone strength based on 3D quantitative computed tomography (QCT) of the femoral neck (FN) in subjects receiving teriparatide (TPTD). Fifty-two postmenopausal women with severe osteoporosis were analyzed. Patients were divided into three subgroups based on their prior treatment with osteoporosis drugs: treatment-naive (Tx-naive; n = 8), pretreated (pre-Tx; n = 12), and pretreated showing an inadequate response to treatment (inad. pre-Tx; n = 32). QCT scans were performed at baseline and after 6, 12, and 24 months of treatment and were analyzed with Mindways QCT-PRO BIT software. Minimum and maximum section modulus, buckling ratio (BR), and cross-sectional area (CSA) were calculated as measurements of bending strength, risk of buckling, and bone apposition, respectively. After 24 months of TPTD treatment, areal and volumetric FN BMD increased significantly by 4.0% and 3.0%, respectively, compared with baseline. Decreases in cortical volumetric BMD occurred in locations not adversely affecting minimum bending strength indicators. Cortical CSA increased by 4.3%, whereas total CSA remained unchanged over the study duration, indicating that endosteal but no periosteal growth was observed. Strength parameters for buckling did not change at 6 and 12 months but improved significantly at 24 months. Measures of bending strength showed a trend toward improvement. Changes tended to be larger in individuals at higher risk of buckling failure. Prior antiresorptive treatment may delay response to TPTD, but based on the small magnitude of the mostly insignificant changes at 6 months, this does not appear to lead to an interim phase of reduced bone strength. In summary, FN QCT provides a tool for detailed longitudinal investigation of bone strength indices in vivo for different loading modes, yields insight into underlying structural changes, and provides relevant mechanostructural information beyond dual-energy X-ray absorptiometry. Continuous TPTD treatment for 24 months improves FN bone strength parameters.

Winning the Battle Against Childhood Physical Inactivity: The Key to Bone Strength?

Winning the Battle Against Childhood Physical Inactivity: The Key to Bone Strength?

Sex-Specific Genetic Loci for Femoral Neck Bone Mass and Strength Identified in Inbred COP and DA Rats

Hip fracture is the most devastating osteoporotic fracture type with significant morbidity and mortality. Several studies in humans identified chromosomal regions linked to hip size and bone mass. Animal models, particularly the inbred rat, serve as complementary approaches for studying the genetic influence on hip fragility. The purpose of this study is to identify sex-independent and sex-specific quantitative trait loci (QTLs) for femoral neck density, structure, and strength in inbred Copenhagen 2331 (COP) and Dark Agouti (DA) rats. A total of 828 (405 males and 423 females) F(2) progeny derived from the inbred COP and DA strains of rats were phenotyped for femoral neck volumetric BMD (vBMD), cross-sectional area, polar moment of inertia (Ip), neck width, ultimate force, and energy to break. A whole genome screen was performed using 93 microsatellite markers with an average intermarker distance of 20 cM. Recombination-based marker maps were generated using MAPMAKER/EXP from the COP x DA F(2) data and compared with published Rat Genome Database (RGD) maps. These maps were used for genome-wide linkage analyses to detect sex-independent and sex-specific QTLs. Significant evidence of linkage (p < 0.01) for sex-independent QTLs were detected for (1) femoral neck vBMD on chromosomes (Chrs) 1, 6, 10, and 12, (2) femoral neck structure on Chrs 5, 7, 10, and 18, and (3) biomechanical properties on Chrs 1 and 4. Male-specific QTLs were discovered on Chrs 2, 9, and 18 for total vBMD, on Chr 17 for trabecular vBMD, on Chr 9 for total bone area, and on Chr 15 for ultimate force. A female-specific QTL was discovered on Chr 2 for ultimate force. The effect size of the individual QTL varied between 1% and 4%. We detected evidence that sex-independent and sex-specific QTLs contribute to hip fragility in the inbred rat. Several QTLs regions identified in this study are homologous to human chromosomal regions previously linked to QTLs contributing to femoral neck and related phenotypes.

Does a novel school-based physical activity model benefit femoral neck bone strength in pre- and early pubertal children?

The effects of physical activity on bone strength acquisition during growth are not well understood. In our cluster randomized trial, we found that participation in a novel school-based physical activity program enhanced bone strength acquisition and bone mass accrual by 2-5% at the femoral neck in girls; however, these benefits depended on teacher compliance with intervention delivery. Our intervention also enhanced bone mass accrual by 2-4% at the lumbar spine and total body in boys. We investigated the effects of a novel school-based physical activity program on femoral neck (FN) bone strength and mass in children aged 9-11 yrs. We used hip structure analysis to compare 16-month changes in FN bone strength, geometry and bone mineral content (BMC) between 293 children who participated in Action Schools! BC (AS! BC) and 117 controls. We assessed proximal femur (PF), lumbar spine (LS) and total body (TB) BMC using DXA. We compared change in bone outcomes between groups using linear regression accounting for the random school effect and select covariates. Change in FN strength (section modulus, Z), cross-sectional area (CSA), subperiosteal width and BMC was similar between control and intervention boys, but intervention boys had greater gains in BMC at the LS (+2.7%, p = 0.05) and TB (+1.7%, p = 0.03) than controls. For girls, change in FN-Z tended to be greater (+3.5%, p = 0.1) for intervention girls than controls. The difference in change increased to 5.4% (p = 0.05) in a per-protocol analysis that included girls whose teachers reported 80% compliance. AS! BC benefits bone strength and mass in school-aged children; however, our findings highlight the importance of accounting for teacher compliance in classroom-based physical activity interventions.

Race and ethnic variation in proximal femur structure and BMD among older men.

Femoral neck dimensions and vBMD from QCT were compared among 3,305 black, Asian, Hispanic, and white men >or=65 yr of age. All had similar stature-adjusted mean femoral neck volume, but black and Asian men had thicker cortices and higher trabecular vBMD, which may increase bone strength. Hip fracture rates among elderly U.S. black and Asian men are lower than rates among white men. Structural characteristics or volumetric BMD (vBMD), which confer advantages for femoral neck bone strength, may vary by race/ethnicity. However, this topic has not been studied in detail. In a cross-sectional study, dimensions and vBMD in the femoral neck and shaft were obtained from QCT scans among 3,305 men >or=65 yr of age in the Osteoporotic Fractures in Men (MrOS) study. Femoral neck measures were cross-sectional area; integral, cortical, and medullary volumes and integral, cortical, and trabecular vBMD. Shaft measures were cross-sectional, cortical, and medullary areas and cortical vBMD. Self-reported race/ethnicity was classified as black, Asian, Hispanic, or white. We used multivariable linear regression models with adjustment for age, height, and body mass index to compare means of the outcome measures in black, Asian, and Hispanic men to those in whites. All groups had similar femoral neck integral volume. Among black and Asian men, mean cortical volume as a percent of integral volume was 6% greater, integral vBMD was 6-10% greater, and trabecular vBMD was 33-36% greater than means among whites. Shaft cross-sectional area was similar among blacks, but smaller among Asians, compared with whites. However, mean shaft cortical area was greater among blacks but similar among Asians and whites, resulting in mean cortical thickness being 5% greater among black and Asian men. Blacks also had greater mean cortical vBMD in both the femoral neck and shaft. Black and Asian men >or=65 yr of age have features in the proximal femur that may confer advantages for bone strength. Specifically, greater cortical thickness and higher trabecular vBMD among black and Asian men could help explain the lower hip fracture rates in these populations. Discerning the mechanisms underlying these differences could provide advances for the prevention and treatment of osteoporosis.

Physical activity and femoral neck bone strength during childhood: The Iowa Bone Development Study

Structural adaptations of bone to changing mechanical loads have recently been documented during adolescence. However, little is known about how bone adapts structurally during the earlier years. Using a longitudinal observational design spanning 6 years of growth (age range 4 to 12 years), we investigated associations between everyday physical activity and hip geometry in a cohort of healthy Midwestern children ( n = 468). Femoral neck (FN) cross sectional area (CSA, cm 2) and FN section modulus (Z, cm 3) were used to describe hip geometry. CSA and Z, indices of axial and bending strength, were assessed using dual-energy X-ray absorptiometry (DXA) scans and the hip structure analysis (HSA) program. Moderate and vigorous physical activity (MVPA) was assessed using accelerometry-based activity monitors and calculated as the number of minutes ≥ 3000 accelerometry movement counts. Data were analyzed using multilevel (random- and fixed-effects) regression models with adjustment for age (year), height (cm), and weight (kg) or lean mass (kg). For boys and girls, MVPA was a positive independent predictor of CSA and Z ( p < 0.05). On average, children who participated in 40 min of MVPA per day would be expected to have 3% to 5% greater CSA and Z than peers participating in 10 min of MVPA per day. Ten-minute increases in daily MVPA had similar effects on CSA in girls and Z in boys as did each additional 1 kg of body weight. When lean mass was substituted for weight, MVPA continued to be a positive independent predictor of CSA and Z for boys, but not girls. This study demonstrates that everyday amounts of physical activity in children are associated with indices of FN bone strength during childhood. Differences in lean mass mediate associations between physical activity and hip geometry in girls, but only somewhat in boys. These results suggest that physical activity is an important contributor to bone strength prior to adolescence and that increasing levels of physical activity during childhood are likely to enhance optimal bone strength.

Physical Activity and Femoral Neck Bone Strength from Early to Late Childhood

Physical Activity and Femoral Neck Bone Strength from Early to Late Childhood

A comparison of the effects of two anabolic agents (fluoride and PTH) on ash density and bone strength assessed in an osteopenic rat model

The aim of this investigation was to compare the effects of sodium fluoride (NaF) and parathyroid hormone (PTH) on ash density and strength in an osteopenic rat model. The study comprised 66 female virgin rats divided into the following 11 groups, each comprising six animals: baseline controls; baseline ovariectomized (ovx); intact controls (5 and 16 weeks), ovx controls (5 and 16 weeks); ovx-treated with PTH (0.02 mg/kg per day, 5 and 16 weeks); ovx treated with NaF (10 mg/kg per day, 5 and 16 weeks); ovx-treated with NaF (1.0 mg/kg per day, 16 weeks). Ovariectomy was performed at 12 weeks of age, 14 weeks prior to start of treatment. Ash density, bone fluoride content, and biomechanical analyses were performed on femoral cortical bone, the right femoral neck, and the sixth lumbar vertebral body. ovx had no effect on cortical bone, whereas the femoral neck displayed a significantly lower bone strength in ovx baseline animals compared with intact baseline rats ( p < 0.05). Vertebral ash density was found to be significantly decreased in ovx rats after 5 and 16 weeks ( p < 0.05). Treatment with fluoride had little effect on the osteopenic rat skeleton. Cortical ash density was significantly lower than ovx and intact groups in the high-dose-treated rats after 5 ( p < 0.01) but not after 16 weeks. High doses of fluoride for 16 weeks induced a significant increase in maximum load and normalized strength in cortical bone when compared with intact animals ( p < 0.05), but not at the other bone sites. Cortical bone strength was not different from the ovx animals at either timepoint. In fluoride-treated animals, femoral neck bone strength, vertebral body bone strength, bone quality, and ash density were found to be at about ovx levels and, in the vertebral body, significantly lower than intact animals ( p < 0.05, p < 0.01). In contrast, treatment with PTH increased ash density, bone strength, and bone quality to above ovx levels ( p < 0.01), and above the level of the intact animals also, although significant values were reached for cortical bone strength only ( p < 0.01). Additionally, biomechanical competence and ash density measurements were significantly higher in PTH-treated rats compared with fluoride-treated rats. In conclusion, this study has shown that PTH has a highly anabolic effect and is capable of effectively restoring ovx-induced loss of bone mass and biomechanical competence. In addition, in this osteopenic rat model, PTH proved much more advantageous than treatment with fluoride, which failed to restore the ovx-induced loss of bone strength.

Long-term exercise of young and adult female rats: Effect on femoral neck biomechanical competence and bone structure

The present study was designed to examine the effect of exercise on femoral neck bone structure and strength in female rats after 4 and 10 months of exercise. Female Fischer rats aged 2 months were exercised for 4 h a day, 5 days a week on a motor-driven treadmill the speed of which was gradually increased until a daily distance of 2 km was reached. The training level was maintained for 4 months (n = 15) and 10 months (n = 15). Sedentary age-matched rats served as controls (n = 30). At death the proximal third of both femora was obtained from each rat. The left femoral neck was tested in a materials-testing machine, and the right was used for either trabecular bone mass measurement (BV/TV) or scanning electron microscopy (SEM). Biomechanical testing revealed a significant training-induced increase in femoral neck bone strength after 4 months of exercise, which although not accelerated was preserved after 10 months of exercise. Histologic investigation revealed a significant training-induced increase in BV/TV, accounted for by a significantly smaller proportion of marrow space. No difference in cortical area was found. Both histology and SEM revealed a tendency to an earlier closure of the growth line in the exercised animals. However, the exercised animals aged 6 months had a significantly increased total femoral length compared with the sedentary rats. No difference was found in total femoral length between sedentary and exercised rats aged 12 months. On the basis of this study, it is concluded that exercise has a positive effect on femoral neck bone strength.(ABSTRACT TRUNCATED AT 250 WORDS)