Bone Strength Index Research Articles

Effects of Smoking on Tibial and Radial Bone Mass and Strength May Diminish with Age

The purpose of the study was to assess the effect of cigarette smoking on indicators of bone strength across a wide age range, controlling for physical activity and neuromuscular performance. We conducted a cross-sectional study with 41 smokers (mean age +/- SD, 41.0 +/- 16.1 yr) and 53 nonsmokers (47.5 +/- 18.2 yr) of both sexes. Bone strength indicators (BSI) were assessed in the lower leg and forearm by peripheral quantitative computed tomography along with physical activity, muscle cross-sectional area, and maximal voluntary muscle force. Physical activity level and muscle cross-sectional area of the leg and arm were similar in smokers and nonsmokers. Although trabecular volumetric bone mineral density and epiphyseal bone mineral content, both indicators of BSI, decreased with age in the nonsmokers' tibia (P < 0.001), this was not observed in the smokers (interaction age x smoking: P = 0.014 and P = 0.032 for density and content, respectively). Regression coefficients were nonsignificant in nonsmokers, whereas coefficients in smokers were -1.24 mg/cm x yr [95% confidence interval (CI) = -2.16-0.33; P = 0.01] for content and -1.20 mg/cm(3) x yr (95% CI = -1.76-0.62; P < 0.001) for trabecular density. The BSI values in the smokers were independent of their smoking history (r(2) = 0.000-0.021), and no effects of sex were observed in the smoking-related differences in BSI. Smoking compromises bone strength by diaphyseal marrow cavity expansion and epiphyseal trabecular bone content reductions. These effects seem to wane with age. The causes of the attenuated effect of smoking on bone at old age remain enigmatic but might be linked to an interaction between the smoke-related factors and senescence processes affecting bone.

Looking beyond bone mineral density

Bone fracture is related to bone strength. In current clinical practice, bone mineral density (BMD) is used as the prime indicator of bone strength, not infrequently at the neglect of an even more pertinent measure of reduced bone strength, namely the radiographic presence of an insufficiency fracture. Bone strength depends not just on BMD but also on bone quality, which relates to such factors as bone architecture, turnover, mineralization, and cellularity. The high resolution available from current imaging techniques, particularly computed tomography and magnetic resonance imaging, along with advanced analytical software has greatly enhanced evaluation of bone architecture and strength. This has improved our knowledge of the pathophysiological processes behind osteoporosis and its treatment beyond that provided by BMD measurement alone. Although still in the experimental stage, these techniques will no doubt be incorporated into clinical practice, leading to a more tailored approach to the screening, monitoring, and treatment of osteoporosis.

The effects of luteolin on osteoclast differentiation, function in vitro and ovariectomy-induced bone loss

Flavonoids, a group of polyphenolic compounds abundant in plants, are known to prevent bone loss in ovariectomized (OVX) animal models. Inhibition of osteoclast differentiation and bone resorption is considered as an effective therapeutic approach in the treatment of postmenopausal bone loss. Luteolin, a plant flavonoid, has potent anti-inflammatory properties both in vivo and vitro. In this study, we found that luteolin markedly decreased the differentiation of both bone marrow mononuclear cells and Raw264.7 cells into osteoclasts. Luteolin also inhibited the bone resorptive activity of differentiated osteoclasts. We further investigated the effects of luteolin on ovariectomy-induced bone loss using micro-computed tomography, biomechanical tests and serum markers assay for bone remodeling. Oral administration of luteolin (5 and 20 mg/kg per day) to OVX mice caused significant increase in bone mineral density and bone mineral content of trabecular and cortical bones in the femur as compared to those of OVX controls, and prevented decreases of bone strength indexes induced by OVX surgery. Serum biochemical markers assays revealed that luteolin prevents OVX-induced increases in bone turnover. These data strongly suggest that luteolin has the potential for prevention of bone loss in postmenopausal osteoporosis by reducing both osteoclast differentiation and function.

Papers Survey of cull sow bone and joint integrity in the Moorepark Research Farm herd

The objective of this study was to examine the effects of production (the number and weight of pigs produced over a lifetime) on the physical and mechanical properties of the...

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.

Neuromuscular performance and body mass as indices of bone loading in premenopausal and postmenopausal women

The strong association between body mass and skeletal robusticity has been attributed to increasing skeletal loading with increasing mass. However, it is unclear whether body mass is merely a coarse substitute for bone loading rather than a true independent predictor of bone strength. As indices of neuromuscular performance, impulse and peak power were determined from vertical ground reaction force during a maximal counter movement jump test in 221 premenopausal and 82 postmenopausal women. Bone compressive (BSI d g 2/cm 4) and bending (SSImax mid mm 3) strength indices were measured with peripheral quantitative computed tomography (pQCT) at the distal ( d) and midshaft ( mid) sites of the tibia. A two-step forced regression model for predicting bone strength indices was constructed. Age, height and body mass were entered first, followed by impulse as an indicator of skeletal loading. The basic model explained 14% ( P < 0.001) of the variance in BSI d in the premenopausal group and 16% ( P = 0.004) in the postmenopausal group, and 32% ( P < 0.001) and 25% ( P < 0.001) of the variance in SSImax nud respectively. Entering impulse into the model increased the explanatory power by 9% ( P < 0.001) and 7% ( P < 0.001) for BSI d and by 8% ( P < 0.001) and 12% ( P < 0.001) for SSImax mid. Furthermore, impulse replaced body mass as an independent significant factor explaining the variance in bone strength. These results indicate that neuromuscular performance should be measured and preferred over body mass in models predicting skeletal robusticity.

Relationship of total body fat mass to weight-bearing bone volumetric density, geometry, and strength in young girls

Understanding the influence of total body fat mass (TBFM) on bone during the peri-pubertal years is critical for the development of future interventions aimed at improving bone strength and reducing fracture risk. Thus, we evaluated the relationship of TBFM to volumetric bone mineral density (vBMD), geometry, and strength at metaphyseal and diaphyseal sites of the femur and tibia of young girls. Data from 396 girls aged 8–13 years from the “Jump-In: Building Better Bones” study were analyzed. Bone parameters were assessed using peripheral quantitative computed tomography (pQCT) at the 4% and 20% distal femur and 4% and 66% distal tibia of the non-dominant leg. Bone parameters at the 4% sites included trabecular vBMD, periosteal circumference, and bone strength index (BSI), while at the 20% femur and 66% tibia, parameters included cortical vBMD, periosteal circumference, and strength–strain index (SSI). Multiple linear regression analyses were used to assess associations between bone parameters and TBFM, controlling for muscle cross-sectional area (MCSA). Regression analyses were then repeated with maturity, bone length, physical activity, and ethnicity as additional covariates. Analysis of covariance (ANCOVA) was used to compare bone parameters among tertiles of TBFM. In regression models with TBFM and MCSA, associations between TBFM and bone parameters at all sites were not significant. TBFM explained very little variance in all bone parameters (0.2–2.3%). In contrast, MCSA was strongly related ( p < 0.001) to all bone parameters, except cortical vBMD. The addition of maturity, bone length, physical activity, and ethnicity did not alter the relationship between TBFM and bone parameters. With bone parameters expressed relative to total body mass, ANCOVA showed that all outcomes were significantly ( p < 0.001) greater in the lowest compared to the middle and highest tertiles of TBFM. Although TBFM is correlated with femur and tibia vBMD, periosteal circumference, and strength in young girls, this relationship is significantly attenuated after adjustment for MCSA. Nevertheless, girls with higher TBFM relative to body mass have markedly diminished vBMD, geometry, and bone strength at metaphyseal and diaphyseal sites of the femur and tibia.

Functional and association analysis of frizzled 1 (FZD1) promoter haplotypes with femoral neck geometry

Frizzleds are receptors for Wnt signaling and are involved in skeletal morphogenesis. Little is known about the transcriptional regulation of frizzleds in bone cells. In the current study, we determined if two common and potentially functional genetic variants (rs2232157, rs2232158) in the frizzled-1 ( FZD1) promoter region and their haplotypes influence FZD1 promoter activity in human osteoblast-like cells. We also determined if these variants are associated with femoral neck bone mineral density (BMD) and geometry in 1319 African ancestry men aged ≥ 40 years. Real-time quantitative PCR and western blot analysis demonstrated FZD1 mRNA and protein expression in the human osteoblast-like cell lines, MG63 and SaOS-2. Promoter activity was next assessed by transient expression of haplotype specific FZD1 promoter reporter plasmids in these cells. In comparison to the common GG haplotype, promoter activity was 3-fold higher for the TC haplotype in both cell lines ( p < 0.05). We previously demonstrated that rs2232158 is associated with differential FZD1 promoter activity and Egr1 binding and thus focused further functional analyses on the rs2232157 G-to-T polymorphism. Electrophoretic mobility shift assay demonstrated that distinct nuclear protein complexes were associated with rs2232157 in an allele specific manner. Bioinformatics analysis predicted that the G to T transversion creates an E2F1 binding site, further supporting the functional significance of rs2232157 in FZD1 promoter regulation. Individual SNPs and haplotypes were not associated with femoral neck BMD. The TC haplotype was associated with larger subperiosteal width and greater CSMI ( p < 0.05). These results suggest that FZD1 expression is regulated in a haplotype-dependent manner in osteoblasts and that these same haplotypes may be associated with biomechanical indices of bone strength.

Bone Geometry, Strength, and Muscle Size in Runners with a History of Stress Fracture

Our primary aim was to explore differences in estimates of tibial bone strength, in female runners with and without a history of stress fractures. Our secondary aim was to explore differences in bone geometry, volumetric density, and muscle size that may explain bone strength outcomes. A total of 39 competitive distance runners aged 18-35 yr, with (SFX, n = 19) or without (NSFX, n = 20) a history of stress fracture were recruited for this cross-sectional study. Peripheral quantitative computed tomography (XCT 3000; Orthometrix, White Plains, NY) was used to assess volumetric bone mineral density (vBMD, mg x mm(-3)), bone area (ToA, mm(2)), and estimated compressive bone strength (bone strength index (BSI) = ToA x total volumetric density (ToD(2))) at the distal tibia (4%). Total (ToA, mm(2)) and cortical (CoA, mm(2)) bone area, cortical vBMD, and estimated bending strength (strength-strain index (SSIp), mm(3)) were measured at the 15%, 25%, 33%, 45%, 50%, and 66% sites. Muscle cross-sectional area (MCSA) was measured at the 50% and 66% sites. Participants in the SFX group had significantly smaller (7%-8%) CoA at the 45%, 50%, and 66% sites (P <or= 0.05 for all), significantly lower SSIp (9%-10%) at the 50% and 66% sites, and smaller MCSA (7%-8%) at the 66% site. The remaining bone parameters including vBMD were not significantly different between groups. After adjusting for MCSA, there were no differences between groups for any measured bone outcomes. These findings suggest that cortical bone strength, cortical area, and MCSA are all lower in runners with a history of stress fracture. However, the lower strength was appropriate for the smaller muscle size, suggesting that interventions to reduce stress fracture risk might be aimed at improving muscle size and strength.

Anti-fracture efficacy of vitamin K

The objective of the present review of the literature was to evaluate the effect of vitamin K supplementation on the skeleton of postmenopausal women. PubMed was used to search the reliable literature for randomized controlled trials (RCTs) by using the inclusion criteria: >or= approximately 50 subjects per group and study period of >or= 2 years. The results of 7 RCTs that met the inclusion criteria showed that vitamin K (K(1) and K(2)) supplementation reduced serum undercarboxylated osteocalcin levels regardless of dose, but that it had inconsistent effects on serum total osteocalcin levels and no effect on bone resorption. Despite the lack of a significant change or the occurrence of only a modest increase in bone mineral density, high-dose vitamin K supplementation improved indices of bone strength in the femoral neck and reduced the incidence of clinical fractures. Furthermore, a post hoc analysis in a large RCT in Japan showed that high-dose vitamin K(2) supplementation decreased the subsequent incidence of vertebral fractures in osteoporotic postmenopausal women with a history of at least 5 vertebral fractures. The review of the reliable literature showed the effect of high-dose vitamin K supplementation on the skeleton of postmenopausal women mediated by mechanisms other than bone mineral density and bone turnover.

Effect of minodronic acid hydrate on hip geometry in Japanese women with postmenopausal osteoporosis

Dual-energy X-ray absorptiometry-based hip structural analysis was performed to evaluate the effect of a bisphosphonate, minodronic acid hydrate, on the geometry of the proximal femur in Japanese patients with osteoporosis. The subjects were 103 postmenopausal patients (average age 63.9 +/- 6.4 years) with primary osteoporosis. Minodronic acid hydrate was administered orally at a dose of 1 mg/day for 12 months. Significant early responses at 3-6 months after the start of administration were observed in all three regions of the proximal femur (narrow neck, intertrochanter, and shaft) in terms of bone density, geometry, and bone strength indices. The outcomes of therapy included a reduction of the internal diameter of the cortical bone (-0.1, -0.6, and -0.2% in the neck, intertrochanter, and shaft, respectively, at 12 months; not significant) and a significant increase in cortical thickness (3.1, 3.7, and 2.0% in the respective regions at 12 months). Furthermore, minodronic acid hydrate induced a significant enlargement of the cross-sectional bone area, which is related to compressive strength; a significant increase in cross-sectional moment of inertia and section modulus (SM 4.9, 5.8, and 2.9% in the neck, intertrochanter, and shaft, respectively, at 12 months; P < 0.001), which are related to the bending strength; and a significant reduction in buckling ratio (BR -3.0% (P < 0.001), -4.2% (P < 0.001), and -1.4% (P < 0.05) in the respective regions at 12 months), which reflects improved cortical stability. These findings show that minodronic acid hydrate reduces age-related endocortical bone resorption, leading to increased cortical thickness and sustained or enhanced bone strength.

Bone Volumetric Density, Geometry, and Strength in Female and Male Collegiate Runners

To explore differences in tibial bone geometry, volumetric density, and estimates of bone strength in runners and healthy controls. Male (n = 21) and female (n = 38) runners (49.1 +/- 13.2 miles x wk(-1)) and inactive healthy controls (17 males and 32 females; mean age = 22 +/- 3.3 yr) were recruited to participate. Peripheral quantitative computed tomography was used to assess total volumetric bone mineral density (vBMD, mg x mm(-3)), total bone area (ToA, mm2), and an estimate of compressive bone strength (bone strength index (BSI) = ToA x total bone volumetric density (ToD2)) at the distal (4%) site of the tibia. ToA (mm2) and cortical bone area (CoA, mm2), cortical vBMD (CoD, mg x mm(-3)), cortical thickness (CoTh, mm), and an estimate of bone bending strength (polar strength strain index (SSIp), mm3) were measured at 50% and 66% sites. ToA and BSI were significantly greater (+11%-19%, P < 0.05) in female runners than controls at the 4% site. At the proximal sites, female runners had significantly greater ToA, CoA, CoTh, and SSIp (+9%-19%, all P < 0.001) compared with female controls. vBMD was similar at all tibia sites. Compared with controls, male runners had significantly greater CoTh at the 50% and 66% sites (+8% and 14%, respectively, P < 0.05) as well as greater CoA (+11%, P < 0.009) at the 66% site. There were no differences in bone strength or density at any site in the male runners. Greater bone strength in female runners was attributable to greater bone area rather than density. Although male runners did not show greater bone strength, they did exhibit favorable bone geometric properties. These data further document that running has osteogenic potential.

Compromised bone strength index in the hemiparetic distal tibia epiphysis among chronic stroke patients: the association with cardiovascular function, muscle atrophy, mobility, and spasticity

The purpose of this study was to identify the determinants of the bone strength index of the distal tibia epiphysis in chronic stroke patients. The results showed that lower cardiovascular fitness, more muscle atrophy, poorer mobility, and more severe spasticity were independently associated with lower tibial bone strength index. To identify the determinants of the bone strength index (BSI) at the distal tibia in chronic stroke patients Sixty-three chronic stroke survivors underwent scanning of the distal tibia at the 4% site on both sides using peripheral quantitative computed tomography. The primary outcomes were trabecular bone mineral density (BMD; milligram per cubic centimeter), total BMD (milligram per cubic centimeter), total bone area (square millimeter), and BSI (square gram per centimeter to the power of four). Cardiovascular fitness, leg lean mass, gait velocity, and spasticity were also measured. Scans from 45 subjects were deemed to have acceptable quality and were included for subsequent analysis. The paretic side had significantly lower trabecular BMD, total BMD, and BSI than the nonparetic side (p < 0.05). However, the total bone area demonstrated no significant side-to-side difference (p > 0.05). After adjusting for relevant biological factors, peak oxygen consumption, leg muscle mass, and gait velocity remained positively associated with tibial BSI on both sides (R (2) change = 6.9-14.2%), whereas spasticity of the paretic leg was negatively associated with tibial BSI on the same side (R (2) change = 4.8%). Cardiovascular function, muscle atrophy, mobility, and spasticity are independently associated with BSI of the distal tibia epiphysis among chronic stroke patients.

History of amenorrhoea compromises some of the exercise-induced benefits in cortical and trabecular bone in the peripheral and axial skeleton: A study in retired elite gymnasts

Background Female gymnasts frequently present with overt signs of hypoestrogenism, such as late menarche or menstrual dysfunction. The objective was to investigate the impact of history of amenorrhoea on the exercise-induced skeletal benefits in bone geometry and volumetric density in retired elite gymnasts. Subjects and methods 24 retired artistic gymnasts, aged 17–36 years, who had been training for at least 15 h/week at the peak of their career and had been retired for 3–18 years were recruited. They had not been engaged in more than 2 h/week of regular physical activity since retirement. Former gymnasts who reported history of amenorrhoea (‘AME’, n = 12: either primary or secondary amenorrhoea) were compared with former gymnasts (‘NO-AME’, n = 12) and controls (‘C’, n = 26) who did not report history of amenorrhoea. Bone mineral content (BMC), total bone area (ToA) and total volumetric density (ToD) were measured by pQCT at the radius and tibia (4% and 66%). Trabecular volumetric density (TrD) and bone strength index (BSI) were measured at the 4% sites. Cortical area (CoA), cortical thickness (CoTh), medullary area (MedA), cortical volumetric density (CoD), stress–strain index (SSI) and muscle and fat area were measured at the 66% sites. Spinal BMC, areal BMD and bone mineral apparent density (BMAD) were measured by DXA. Results Menarcheal age was delayed in AME when compared to NO-AME (16.4 ± 0.5 years vs. 13.3 ± 0.4 years, p < 0.001). No differences were detected between AME and C for height-adjusted spinal BMC, aBMD and BMAD, TrD and BSI at the distal radius and tibia, CoA at the proximal radius, whereas these parameters were greater in NO-AME than C ( p < 0.05–0.005). AME had lower TrD and BSI at the distal radius, and lower spinal BMAD than NO-AME ( p < 0.05) but they had greater ToA at the distal radius ( p < 0.05). Conclusion Greater spinal BMC, aBMD and BMAD as well as trabecular volumetric density and bone strength in the peripheral skeleton were found in former gymnasts without a history of menstrual dysfunction but not in those who reported either primary or secondary amenorrhoea. History of amenorrhoea may have compromised some of the skeletal benefits associated with high-impact gymnastics training.

Correlation of pQCT bone strength index with mechanical testing in distraction osteogenesis

Distraction osteogenesis is an established method of treatment of non-unions and limb length discrepancies. Despite improvements in surgical techniques and fixation devices there is still a considerable possibility of failure of the regenerate bone after frame removal. The hypothesis of the present experimental study was that a noninvasive bone strength marker, the strength–strain index (SSI) measured by peripheral quantitative computerized tomography (pQCT), could be significantly correlated with a biomechanical bone strength index, the maximum load at bone failure ( F max), assessed in a three-point bending test. The right tibias of fifteen male New Zealand White rabbits were subjected to gradual lengthening using an external fixator. At the end of the consolidation phase (55th day) the animals were sacrificed and the lengthened tibiae were collected free of soft tissue, after removal of the lengthener, for immediate scanning and mechanical testing. The values of cortical bone mineral density, cortical bone area, and the corresponding SSI y, as measured by pQCT, were assessed for statistically significant correlation relative to the values of the F max and stiffness as evaluated by the three-point bending test were assessed. SSI y showed a statistically significant positive correlation with the maximum load ( F max) with a correlation value R = 0.846 ( p < 0.001), and it was a good predictor of F max since it was able to describe the 71.6% of variability of F max( R 2 = 0.716). Furthermore, cortical bone area appeared to be highly correlated with F max ( p < 0.005), but it was a less efficient predictor of F max ( R 2 = 0.471). There was, also, a statistically significant correlation between SSI y and bone stiffness as assessed in the 3-point bending test ( p < 0.005). In conclusion, the present study reveals that the SSI can be used as a sensitive index of adequate consolidation of the regenerate bone, possibly able to reduce mechanical failure due to premature frame removal. In clinical relevance, the aforementioned hypothesis should be applied in studies of human populations and possible confirmation of its validity would establish pQCT as a valuable diagnostic tool not only in distraction osteogenesis but also in other techniques of bone healing.

Serum Estradiol Is Associated With Volumetric BMD and Modulates the Impact of Physical Activity on Bone Size at the Age of Peak Bone Mass: A Study in Healthy Male Siblings

This study investigates determinants of peak bone mass (PBM) in healthy men, focusing on effects and interactions of parameters reflecting mechanical loading and sex steroids. Healthy male siblings (n = 677; 25-45 yr) were recruited in a cross-sectional, population-based study. Physical activity score was assessed by a self-reported questionnaire. Cross-sectional muscle area (CSMA) and bone parameters of radius (4% and 66% site) and tibia (66% site) were assessed using pQCT. Peak torque of biceps and quadriceps muscles was assessed by isokinetic dynamometry. Serum testosterone (T) and estradiol (E(2)) levels were measured using immunoassays; free hormone fractions were calculated. Relations between indices of bone strength, CSMA, muscle strength, and sex steroids were studied using linear mixed-effects modeling. Physical activity, CSMA, and muscle strength were positively associated with indices of bone strength, except for volumetric BMD (vBMD). After controlling for age, weight, and height, free E(2) levels were positively associated with trabecular and cortical vBMD, negatively associated with endosteal circumference at the radius, and positively associated with cortical vBMD at the tibia. In addition, positive interactions between physical activity and serum E(2) concentrations were observed for bone size at the tibia. No associations between free T levels and pQCT bone parameters were found. In this population of healthy men at the age of PBM, parameters reflecting mechanical loading are confirmed as important determinants of bone size. E(2), but not T, levels are positively associated with vBMD and modulate the impact of physical activity on bone size at the tibia.

Tibial And Radial Bone Strength In Women Is Predicted By Muscle Load And Sex Steroids

Mechanical loading and sex steroids are hypothesized to play an important role in bone metabolism and to influence bone health in premenopausal women. PURPOSE: To determine predictors of bone strength, geometry and volumetric bone mineral density (vBMD) in sedentary premenopausal women. METHODS: Baseline data was used from a subset of healthy, sedentary, premenopausal women (n = 67, aged 18-30 years; mean BMI 23.96 ± 3.1) enrolled in a study of physical activity and ovulation (WISER). Estrogen status was determined by 3-day urine collection. Menstrual cycle length (MCL) and luteal phase length (LPL) were assessed by questionnaire and confirmed with ovulation kits over 2 menstrual cycles. LPL was used as a surrogate of progesterone exposure. Total body lean mass (LM) and fat mass (FM) were measured by dual energy x-ray absorptiometry (DXA). Volumetric bone mineral density (vBMD), bone geometry (total and cortical area), estimated bone strength (polar strength strain index, SSIp, and bone strength index, BSI) and muscle cross-sectional area (MCSA) were assessed by pQCT (XCT 3000) at the distal (4, 8%) sites and midshaft (50, 66%) sites of the tibia and radius. Trabecular and total vBMD, total area and BSI were reported for distal sites; cortical vBMD, total and cortical area, and SSI were reported for midshaft sites. Linear regression, adjusted for limb length and age, was used to determine predictors of bone variables. RESULTS: The primary determinant of SSI and geometry at the midshaft tibia was LM while FM was the primary predictor of vBMD (P < 0.01). At the distal tibia, LM was the primary determinant of BSI, bone geometry, and vBMD (P < 0.01). MCSA was the primary determinant of both bone strength and geometry of the radius midshaft, while LPL predicted vBMD (P < 0.01). At the distal radius, menstrual cycle characteristics, MCSA and LM were the primary predictors of all bone variables (P < 0.05). CONCLUSION: Since sedentary premenopausal women likely have lower MCSA and LM compared to active women, these data suggest bone health may be compromised in this population. Also, luteal phase length and menstrual cycle length may significantly affect bone health. Thus, less muscle along with subtle alterations in menstrual cycle characteristics may lead to compromised bone strength in sedentary women. Supported by NCI Grant NCT00393172

High-dose vitamin K supplementation reduces fracture incidence in postmenopausal women: a review of the literature

Although systematic review and meta-analysis of randomized controlled trials (RCTs) have concluded that vitamin K is effective in preventing fractures, the effect of vitamin K on the skeleton remains a matter of controversy. The objective of the present review of the literature was to evaluate the effect of vitamin K supplementation on the skeleton of postmenopausal women. PubMed was used to search the reliable literature for RCTs by using the search terms "vitamin K(1) or vitamin K(2)," "bone," and "postmenopausal women" and the following inclusion criteria: approximately 50 or more subjects per group and study period of 2 years or longer. Seven RCTs met the inclusion criteria. The results of these RCTs showed that vitamin K(1) and vitamin K(2) supplementation reduced serum undercarboxylated osteocalcin levels regardless of dose but that it had inconsistent effects on serum total osteocalcin levels and no effect on bone resorption. Despite the lack of a significant change or the occurrence of only a modest increase in bone mineral density, high-dose vitamin K(1) and vitamin K(2) supplementation improved indices of bone strength in the femoral neck and reduced the incidence of clinical fractures. The review of the reliable literature confirmed the effect of vitamin K(1) and vitamin K(2) supplementation on the skeleton of postmenopausal women mediated by mechanisms other than bone mineral density and bone turnover.

Bone mass and geometry of the tibia and the radius of master sprinters, middle and long distance runners, race-walkers and sedentary control participants: A pQCT study

Mechanical loading is thought to be a determinant of bone mass and geometry. Both ground reaction forces and tibial strains increase with running speed. This study investigates the hypothesis that surrogates of bone strength in male and female master sprinters, middle and long distance runners and race-walkers vary according to discipline-specific mechanical loading from sedentary controls.Bone scans were obtained by peripheral Quantitative Computed Tomography (pQCT) from the tibia and from the radius in 106 sprinters, 52 middle distance runners, 93 long distance runners and 49 race-walkers who were competing at master championships, and who were aged between 35 and 94 years. Seventy-five age-matched, sedentary people served as control group.Most athletes of this study had started to practice their athletic discipline after the age of 20, but the current training regime had typically been maintained for more than a decade. As hypothesised, tibia diaphyseal bone mineral content (vBMC), cortical area and polar moment of resistance were largest in sprinters, followed in descending order by middle and long distance runners, race-walkers and controls. When compared to control people, the differences in these measures were always >13% in male and >23% in female sprinters (p<0.001). Similarly, the periosteal circumference in the tibia shaft was larger in male and female sprinters by 4% and 8%, respectively, compared to controls (p<0.001). Epiphyseal group differences were predominantly found for trabecular vBMC in both male and female sprinters, who had 15% and 18% larger values, respectively, than controls (p<0.001). In contrast, a reverse pattern was found for cortical vBMD in the tibia, and only few group differences of lower magnitude were found between athletes and control people for the radius.In conclusion, tibial bone strength indicators seemed to be related to exercise-specific peak forces, whilst cortical density was inversely related to running distance. These results may be explained in two, non-exclusive ways. Firstly, greater skeletal size may allow larger muscle forces and power to be exerted, and thus bias towards engagement in athletics. Secondly, musculoskeletal forces related to running can induce skeletal adaptation and thus enhance bone strength.

Effects of 8 months of twice-weekly high versus low intensity whole body vibration on risk factors for hip fracture in postmenopausal women: A randomized controlled trial

INTRODUCTION Whole body vibration (WBV) may improve bone mass and reduce fall risk in postmenopausal women at risk of hip fracture, however, the minimum effective dose and relative efficacy of high versus low intensity vibration, are unknown. METHODS Forty-seven postmenopausal women were randomised to control, low intensity (LV) or high intensity (HV) vibration. At baseline and follow-up, biometrics, whole body, proximal femur (PF), lumbar spine (LS) and forearm bone mineral content (BMC), bone mineral density (BMD), LS area, FN area, cortical width, index of bone strength, cross sectional moment of inertia (XR36, Norland), calcaneal broadband ultrasound attenuation (BUA) (QUS-2, Quidel), and functional muscle (chair rise, wall squat) and balance (single leg stance, tandem walk) performance were tested. Dietary calcium was determined via questionnaire and FoodWorks analysis (2007, Xyris, Brisbane). Current and historical bone-relevant physical activity was determined using the BPAQ (1). Treatment groups attended supervised WBV sessions twice weekly for 8 months (LV - 1 x 15 minute session at 30Hz, 0.2g; HV - 2 x 3 minute sessions at 12.5 Hz, ~1g). Treatment effects were examined by repeated measures ANOVA and multiple regression analyses controlling for age, weight, height, calcium consumption and physical activity. RESULTS No significant between-group effects were found for any measure, however, trends were evident and within group effects were observed. Significant bone loss occurred at the hip and spine in control (p=0.02) but not WBV groups. Wall squat time (muscle strength/endurance) and single leg stance (static balance) improved in the HV group (p=0.004) and a similar trend was evident for the LV group but not controls. A significant difference in calcaneal ultrasound between control and HV groups at baseline disappeared at follow-up as a result of bone loss in controls and gain in the HV group. CONCLUSIONS Findings suggest that twice-weekly WBV cannot entirely prevent age-related skeletal loss, but that loss may be considerably muted. Muscle and balance function can be improved with very minimal exposure to high intensity WBV. Findings have important clinical implications for groups at high risk of hip fracture who are unable or unwilling to adopt traditional therapeutic options. 1 Weeks BK and Beck BR: The BPAQ: A bone-specific physical activity assessment instrument. Osteoporosis International, 19(11):1567-1577, 2008.