The Influence of High‐Impact Exercise on Cortical and Trabecular Bone Mineral Content and 3D Distribution Across the Proximal Femur in Older Men: A Randomized Controlled Unilateral Intervention

Regular exercisers have lower fracture risk, despite modest effects of exercise on bone mineral content (BMC). Exercise may produce localized cortical and trabecular bone changes that affect bone strength independently of BMC. We previously demonstrated that brief, daily unilateral hopping exercises increased femoral neck BMC in the exercise leg versus the control leg of older men. This study evaluated the effects of these exercises on cortical and trabecular bone and its 3D distribution across the proximal femur, using clinical CT. Fifty healthy men had pelvic CT scans before and after the exercise intervention. We used hip QCT analysis to quantify BMC in traditional regions of interest and estimate biomechanical variables. Cortical bone mapping localized cortical mass surface density and endocortical trabecular density changes across each proximal femur, which involved registration to a canonical proximal femur model. Following statistical parametric mapping, we visualized and quantified statistically significant changes of variables over time in both legs, and significant differences between legs. Thirty‐four men aged mean (SD) 70 (4) years exercised for 12‐months, attending 92% of prescribed sessions. In traditional regions of interest, cortical and trabecular BMC increased over time in both legs. Cortical BMC at the trochanter increased more in the exercise than control leg, whereas femoral neck buckling ratio declined more in the exercise than control leg. Across the entire proximal femur, cortical mass surface density increased significantly with exercise (2.7%; p < 0.001), with larger changes (> 6%) at anterior and posterior aspects of the femoral neck and anterior shaft. Endocortical trabecular density also increased (6.4%; p < 0.001), with localized changes of > 12% at the anterior femoral neck, trochanter, and inferior femoral head. Odd impact exercise increased cortical mass surface density and endocortical trabecular density, at regions that may be important to structural integrity. These exercise‐induced changes were localized rather than being evenly distributed across the proximal femur. © 2015 American Society for Bone and Mineral Research.     

Curved beam model of the proximal femur for estimating stress using dual-energy x-ray absorptiometry derived structural geometry

The investigation of individual differences in hip strength requires a method to measure structural geometry in vivo and a valid analytical approach to calculate mechanical stress. We developed a method for deriving structural geometry of the femur from the proximal shaft through the femoral neck, using data from dual energy x-ray absorptiometry. The geometric properties are employed in a two-dimensional curved beam model of the proximal femur to estimate stresses on the lateral and medial bone surfaces. Stresses calculated by this method are compared with those from the conventional flexure formula and with results produced from a cadaver femur with use of three-dimensional finite element analysis of computed tomography data. Loading conditions simulating a one-legged stance and a fall on the greater trochanter are employed. Stresses calculated by curved beam theory are in much better agreement with three-dimensional finite element analysis than are those for which the conventional straight beam formula was used. In simulation of a fall on the greater trochanter, all three methods show peaks of stress at the femoral neck but only the curved beam and finite element analysis methods show an additional peak at the medial intertrochanteric margin. Both neck and trochanter regions correspond to common failure sites for hip fractures in the elderly. The curved beam treatment of hip structure derived from dual-energy x-ray absorptiometry provides an approach for the in vivo engineering analysis of hip structure that is not practical by other methods.     

老年股骨颈骨折骨密度、Singh指数的研究

目的研究骨密度和Singh指数在衡量股骨近端骨强度和预测股骨颈骨折中的意义.方法对21名60岁以上、因轻度创伤所致新鲜股骨颈骨折老年人进行股骨近端骨密度、Singh指数及Ward三角矿化骨体积进行测量.结果本组患者股骨近端骨密度减少规律,Ward三角>股骨颈>股骨粗隆,骨密度减少的下限(±s)是股骨颈1.14SD、粗隆部0.35SD、Ward三角2.04SD;Singh指数4级以下(含4级)20名(95.2%);Singh指数与MBV呈正相关(r=0.517P<0.05),与粗隆部骨密度及减少的标准差呈正相关(r=0.457,0.474P<0.05).结论骨密度较峰值骨量减少的标准差数在股骨颈大于1.14、粗隆部大于0.35、Ward三角大于2.04,加上Singh指数低于4级(含4级)提示股骨颈骨折的危险性明显增高.     

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. INTRODUCTION: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Proximal femoral density and geometry measurements by quantitative computed tomography: association with hip fracture

INTRODUCTION: Bone mineral density and geometry measurements by volumetric quantitative computed tomography (vQCT) have been utilized in clinical research studies of aging, pharmacologic intervention and mechanical unloading, but there is relatively little information about the association of these measures with hip fracture. To address this issue, we have carried out a study comparing vQCT parameters in elderly Chinese women with hip fractures with measurements in age-matched controls. MATERIALS AND METHODS: Forty-five women (mean age 74.71+/-5.94) with hip fractures were compared to 66 age-matched control subjects (mean age 70.70+/-4.66). vQCT was employed to characterize the volumetric bone mineral density in cortical, trabecular, and integral volumes of interest in the proximal femur. In addition to the volume of interest measurements, we computed the cross-sectional areas of the femoral neck and intertrochanteric planes, the femoral neck axis length, indices of femoral neck bending and compressive strength, and measures of femoral neck cortical geometry. To determine if cortical geometry measures were associated with hip fracture independently of trabecular vBMD, we carried out multi-variate analyses including these parameters in a logistic regression model. RESULTS AND CONCLUSIONS: All vQCT measurements discriminated between fractured subjects and age-matched controls. There was no significant difference in predictive strength between volumetric and areal representations of BMD and trabecular and integral vBMD showed comparable discriminatory power, although both of these measures were more correlated to fracture status than cortical vBMD. We found that fractured subjects had larger femoral neck cross-sectional areas, consistent with adaptation to lower BMD in these osteoporotic subjects. The larger neck cross-sectional areas resulted in bending strength indices in the fractured subjects that were comparable or larger than those of the control subjects. In multi-variate analyses, reduced femoral neck cortical thickness and buckling ratio indices were associated with fracture status independently of trabecular vBMD.     

The femoral neck lengthening osteotomy

Surgical Principles Premature closure of the epiphyseal plate can be a complication of hip dysplasia, Perthes disease, trauma or septic arthritis of the hip. As a result, the proximal femur may show a typical deformity with shortening of the neck of the femur and relative overgrowth of the greater trochanter. The femoral neck lengthening osteotomy aims at restoring the normal anatomy with restitution of the length of the femoral neck and leg length, and improving the lever arm of the abductors. The procedure includes three osteotomies parallel to the blade of a 130° or 120° blade plate. Lateralization of the shaft effectively lengthens the femoral neck. A part of the overgrown greater trochanter is used to fill the gap proximally to the lateralized shaft. The remaining trochanter is pulled distally and fixed to the femur. Revised Version from: Operat. Orthop. Traumatol. 1 (1989), 170–178 (German Edition).     

Effect of eldecalcitol, an active vitamin D analog, on hip structure and biomechanical properties: 3D assessment by clinical CT

The effects of an active vitamin D analog, eldecalcitol (ELD), on bone mineral density (BMD), bone geometry, and biomechanical properties of the proximal femur were investigated by using clinical CT. The subjects--a subgroup of a recent randomized, double-blind study comparing anti-fracture efficacy of ELD with alfacalcidol (ALF) - constituted 193 ambulatory patients with osteoporosis (189 postmenopausal women and 4 men aged 52-85 years, average ± SD: 70.9 ± 6.92 years) enrolled at 11 institutions. Multidetector-row CT data was acquired at baseline and at completion of 144 weeks' treatment. Cross-sectional densitometric and geometric parameters of the femoral neck were derived from three-dimensional CT data. Biomechanical properties including cross-sectional moment of inertia (CSMI), section modulus (SM) and buckling ratio (BR) of the femoral neck, and CSMI of the femoral shaft were also calculated. We found that, (1) with respect to the femoral neck cross-sectional parameters (total bone), in the ALF group, volumetric BMD (vBMD) decreased but bone mass was maintained and cross-sectional area (CSA) increased. In contrast, ELD maintained vBMD with a significant increase in bone mass and a trend toward increased CSA. (2) With respect to the femoral neck cross-sectional parameters (cortex), cortical thickness decreased in the ALF group, but was maintained in the ELD group. In the ALF group, vBMD and bone mass increased, and CSA was maintained. In the ELD group, vBMD, CSA, and bone mass increased. (3) With respect to the biomechanical properties of the femoral neck, ELD improved CSMI and SM to a greater extent than did ALF. BR increased in both the ALF and ELD groups. (4) With respect to the femoral shaft parameters, overall the results of bone geometry and CSMI of the femoral shaft were very consistent with the results for the femoral neck; however, cortical vBMD of the femoral shaft decreased significantly in both the ELD and ALF groups. In conclusion, our longitudinal analysis of hip geometry by clinical CT revealed the unexpected potential of ELD to increase cortical CSA, vBMD, and bone mass, and to maintain cortical thickness, probably through the more potent effect of ELD in mitigating endocortical bone resorption than ALF. By improving the biomechanical properties of the proximal femur, ELD may have the potential to reduce the risk of hip fractures.     

Odanacatib Treatment Affects Trabecular and Cortical Bone in the Femur of Postmenopausal Women: Results of a Two‐Year Placebo‐Controlled Trial

Odanacatib, a selective cathepsin K inhibitor, increases areal bone mineral density (aBMD) at the spine and hip of postmenopausal women. To gain additional insight into the effects on trabecular and cortical bone, we analyzed quantitative computed tomography (QCT) data of postmenopausal women treated with odanacatib using Medical Image Analysis Framework (MIAF; Institute of Medical Physics, University of Erlangen, Erlangen, Germany). This international, randomized, double‐blind, placebo‐controlled, 2‐year, phase 3 trial enrolled 214 postmenopausal women (mean age 64 years) with low aBMD. Subjects were randomized to odanacatib 50 mg weekly (ODN) or placebo (PBO); all participants received calcium and vitamin D. Hip QCT scans at 24 months were available for 158 women (ODN: n = 78 women; PBO: n = 80 women). There were consistent and significant differential treatment effects (ODN‐PBO) for total hip integral (5.4%), trabecular volumetric BMD (vBMD) (12.2%), and cortical vBMD (2.5%) at 24 months. There was no significant differential treatment effect on integral bone volume. Results for bone mineral content (BMC) closely matched those for vBMD for integral and trabecular compartments. However, with small but mostly significant differential increases in cortical volume (1.0% to 1.3%) and thickness (1.4% to 1.9%), the percentage cortical BMC increases were numerically larger than those of vBMD. With a total hip BMC differential treatment effect (ODN‐PBO) of nearly 1000 mg, the proportions of BMC attributed to cortical gain were 45%, 44%, 52%, and 40% for the total, neck, trochanter, and intertrochanter subregions, respectively. In postmenopausal women treated for 2 years, odanacatib improved integral, trabecular, and cortical vBMD and BMC at all femur regions relative to placebo when assessed by MIAF. Cortical volume and thickness increased significantly in all regions except the femoral neck. The increase in cortical volume and BMC paralleled the increase in cortical vBMD, demonstrating a consistent effect of ODN on cortical bone. Approximately one‐half of the absolute BMC gain occurred in cortical bone. © 2014 American Society for Bone and Mineral Research.     

Correlates of trabecular and cortical volumetric bone mineral density at the femoral neck and lumbar spine: The osteoporotic fractures in men study (MrOS)

The objective of this cross‐sectional analysis was to examine the correlates of trabecular and cortical volumetric bone mineral density (vBMD) in 3670 community‐dwelling men, mean age 73.6 ± 5.9 years. vBMD was measured by quantitative computed tomography (QCT) and areal BMD by dual‐energy X‐ray absorptiometry (DXA). Demographic, historical, and lifestyle information was obtained by interview, and height, weight, and neuromuscular function were determined by examination. To express the strength of the associations, percent differences (95% confidence interval) were calculated from multivariable linear regression models using the formula 100 (β × unit/mean BMD). Units for continuous variables were chosen to approximate 1 standard deviation (SD). The multivariable linear regression models predicted 15%, 21%, and 20% of the overall variance in trabecular and cortical vBMD of the femoral neck and vBMD of the lumbar spine, respectively. Diabetes was associated with a 16.5% greater trabecular vBMD at the femoral neck and 11% at the lumbar spine but less than 2% for cortical vBMD. For femoral neck trabecular vBMD, the strongest negative correlates were past smoking (?9%), fracture history (?15%), kidney stones (?7%), corticosteroids (?11%), and insulin therapy (?26%). For cortical vBMD, the strongest negative correlate was use of thyroid medication (?2.8%). The strongest negative correlates for lumbar spine trabecular vBMD were fracture history (?5%), antiandrogen use (?19%), height (?8%), and thiazoliainedione use (?22%). Bioavailable estradiol and testosterone levels were positively related and sex hormone–binding globulin was negatively related to trabecular vBMD of the spine. There was no relationship between sex hormones and femoral neck trabecular vBMD. Our conclusion is that correlates of trabecular vBMD and cortical vBMD appear to differ in older men. © 2010 American Society for Bone and Mineral Research     

抗阻力量训练对青年和老年女性骨密度的影响

目的探讨相同负荷强度的抗阻力量训练对青年和老年女性骨密度的影响。方法身高、体重相匹配的青年组(n=36)和老年组(n=34)进行16w躯干、上下肢的抗阻力量训练。测试受试者腰椎(L_2~L_4)、股骨近端(股骨颈、Ward三角区、大转子)骨密度,拉力和下肢肌力。结果 (1)(3)干预后青年组股骨颈、Ward三角区和腰椎(L_2~L_4)BMD和拉力显著增大(P0.05),大转子BMD无显著变化;老年组股骨颈、Ward三角区和腰椎(L_2~L_4)BMD、拉力和下肢肌力显著增大(P0.05),大转子BMD无显著变化。(2)拉力与腰椎(L_2~L_4)、股骨颈、Ward三角区和大转子BMD呈显著正相关(r=0.642、0.686、0.600、0.781)、下肢肌力与腰椎(L_2~L_4)和Ward三角区BMD呈显著正相关(r=0.526,r=0.619)。结论 16 w力量训练改善了青年和老年女性腰椎和股骨近端的骨密度且无年龄差异,但对大转子骨密度改善不显著。     

Dimensions and volumetric BMD of the proximal femur and their relation to age among older U.S. men.

We measured femoral neck and shaft dimensions and volumetric BMD with QCT. Relations of these measures to age were quantified in a cross-sectional study among 3358 men 65-100 years old. Relations of femoral neck dimensions and vBMD to age differed from those in the shaft, indicating that patterns of bone modeling and remodeling in the neck and shaft are distinct. INTRODUCTION: Little is known about population variation in dimensions and volumetric BMD of the proximal femur or the relation of these measures to age among older men. MATERIALS AND METHODS: In a cross-sectional study, dimensions and volumetric BMD (vBMD) in the femoral neck and shaft were obtained from QCT scans among 3358 men 65-100 years of age in the Osteoporotic Fractures in Men cohort. Total bone size and size of the cortical and medullary compartments were measured with volumes in the femoral neck and with areas in the shaft. We quantified distributions of these measures and examined their relations to age with multivariable linear regression. RESULTS: Population variation in femoral neck and shaft dimensions and vBMD was substantial. In the femoral neck, total volume was minimally related to age, whereas cortical volume was 5% smaller and medullary volume was 10% larger (both p < 0.0001) in the oldest (85+ years) compared with the youngest (65-69 years) men. Across these ages, the percent of cortical bone declined from 46% to 42% (p < 0.0001). Integral and trabecular vBMD were 9% and 22% lower, whereas DXA femoral neck BMD was 4% lower, in the older men. Neck cortical vBMD was unrelated to age. In the shaft, cross-sectional area and medullary area were 9% and 22% larger, respectively, in the oldest men (both p < 0.0001), but cortical area was unchanged with age. The percent of cortical bone declined from 69% to 65% across these ages (p < 0.0001). Shaft cortical BMD was 4% lower in the older men (p < 0.0001). CONCLUSIONS: There is substantial diversity of femoral morphology and vBMD among older U.S. men. Patterns indicative of modeling and remodeling in the femoral neck were distinct from those in the shaft. Notably, changes in periosteal and endosteal dimensions that underlie cortical thinning appear to differ in the neck and shaft.     

Bone Density and Cross-sectional Geometry of the Proximal Femur Are Bilaterally Elevated in Elite Cricket Fast Bowlers

The skeleton of a cricket fast bowler is exposed to a unique combination of gravitational and torsional loading in the form of substantial ground reaction forces delivered through the front landing foot, and anterior-posterior shear forces mediated by regional muscle contractions across the lumbo-pelvic region. The objectives of this study were to compare the hip structural characteristics of elite fast bowlers with recreationally active age-matched controls, and to examine unilateral bone properties in fast bowlers. Dual-energy X-ray absorptiometry of the proximal femur was performed in 26 elite male fast bowlers and 26 normally active controls. Hip structural analysis (GE Lunar; enCORE version 15.0) determined areal bone mineral density (BMD) of the proximal femur, and cross-sectional area, section modulus (Z), cross-sectional moment of inertia, and femoral strength index at the narrow region of the femoral neck. Mean femoral neck and trochanter BMD were greater in fast bowlers than in controls (p?<0.001). All bone geometry properties, except for cross-sectional moment of inertia, were superior in fast bowlers (p?<0.05) following adjustment for height and lean mass. There were no asymmetries in BMD or bone geometry when considering leg dominance of the fast bowlers (p?>?0.05). Elite fast bowlers have superior bone characteristics of the proximal femur, with results inferring enhanced resistance to axial compression (cross-sectional area), and bending (Z) forces, and enhanced strength to withstand a fall impact as indicated by their higher femoral strength index. No asymmetries in hip bone properties were identified, suggesting that both torsional and gravitational loading offer significant osteogenic potential.     

DXA and pQCT predict pertrochanteric and not femoral neck fracture load in a human side‐impact fracture model

The validity of dual energy X‐ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) measurements as predictors of pertrochanteric and femoral neck fracture loads was compared in an experimental simulation of a fall on the greater trochanter. 65 proximal femora were harvested from patients at autopsy. All specimens were scanned with use of DXA for areal bone mineral density and pQCT for volumetric densities at selected sites of the proximal femur. A three‐point bending test simulating a side‐impact was performed to determine fracture load and resulted in 16 femoral neck and 49 pertrochanteric fractures. Regression analysis revealed that DXA BMD trochanter was the best variable at predicting fracture load of pertrochanteric fractures with an adjusted R² of 0.824 (p < 0.0001). There was no correlation between densitometric parameters and the fracture load of femoral neck fractures. A significant correlation further was found between body weight, height, femoral head diameter, and neck length on the one side and fracture load on the other side, irrespective of the fracture type. Clinically, the DXA BMD trochanter should be favored and integrated routinely as well as biometric and geometric parameters, particularly in elderly people with known osteoporosis at risk for falls. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:31–38, 2014.     

Abaloparatide Effects on Cortical Volumetric BMD and Estimated Strength Indices of Hip Subregions by 3D-DXA in Women With Postmenopausal Osteoporosis

In ACTIVE, abaloparatide increased areal BMD (aBMD) of the hip and femoral neck vs teriparatide and placebo in women with osteoporosis. Previously, 3D-processing of dual X-ray absorptiometry (DXA) scans of a subgroup of ACTIVE subjects showed similar increases in trabecular volumetric BMD (Tb.vBMD) and greater increases in cortical vBMD (Ct.vBMD) of the total hip with abaloparatide vs teriparatide. The current analyses from this subgroup describe 2D- and 3D-DXA data for hip subregions. Randomly selected subjects from ACTIVE (n = 250/treatment group) who received 18 mo of placebo, abaloparatide 80 µg, or open-label teriparatide 20 µg by daily subcutaneous injection underwent hip DXA at baseline, and mo 6 and 18 of treatment. Areal BMD of the femoral neck, trochanter, and femoral shaft was determined using standard 2D-DXA and 3D-SHAPER software to retrospectively evaluate changes from baseline in volumetric parameters of these 3 hip subregions, including trabecular and cortical segmentation. Changes in biomechanical parameters cross-sectional moment of inertia (CSMI), section modulus (Z), and buckling ratio were also evaluated. Femoral neck, trochanter, and shaft aBMD increased in the abaloparatide and teriparatide groups at mo 6 and 18 vs placebo, with greater increases for abaloparatide vs teriparatide at the femoral neck at mo 6 and the shaft at mo 6 and 18. All 3 subregions showed similar significant increases in Tb.vBMD with abaloparatide and teriparatide vs placebo, whereas Ct.vBMD of all 3 subregions showed greater increases after 18 mo of abaloparatide vs teriparatide. Biomechanical parameters improved in all subregions with abaloparatide and teriparatide vs placebo, with greater improvements in CSMI and Z of the femoral neck and lower shaft after 6 and 18 mo of abaloparatide vs teriparatide. Differential femoral neck and shaft Ct.vBMD responses may explain the greater increases in CSMI and Z of those subregions with abaloparatide vs teriparatide.     

Mechanical strength of the proximal femur as predicted from geometric and densitometric bone properties at the lower limb versus the distal radius.

This experimental study compares geometric and densitometric properties of cortical and trabecular bone at the lower limb and the distal radius with those at the femoral neck, and evaluates their ability to predict mechanical failure loads of the proximal femur. One hundred five cadavers were examined with peripheral quantitative computed tomography (LpQCT), with measurements being performed in situ at the distal radius (4%, 20%, 33%), at the distal and proximal tibia, at the tibial and femoral shaft, and at the distal femur. Ex situ measurements were obtained at the femoral neck and at the proximal femoral shaft. Pairs of femora were mechanically tested in a vertical loading and a side impact (fall) configuration. The total (cross-sectional) bone mineral content and trabecular density, but not the cortical properties, displayed a higher association between the femoral neck and the peripheral lower limb than between the neck and the distal radius. Approximately 50%-60% of the variability of femoral failure loads (and >80% of trochanteric side impact fractures) were predicted by in vitro measurements at the neck. Geometric cortical parameters and density contributed independently and significantly to femoral strength. Measurements at the peripheral skeleton explained, however, only 30%-45% of the variability of femoral failure, with no significant difference between the lower limb and the distal radius. At peripheral sites, a combination of geometric and densitometric variables was slightly superior to bone mineral content alone in predicting failure in vertical loading, but this was less evident for cervical side impact fractures. The results show that a stronger association of total bone mineral content and trabecular density between the femoral neck and the lower limb does not translate into improved prediction of femoral strength from measurements at the lower limb vs. those at the distal radius.     

Femoral neck cortical geometry measured with magnetic resonance imaging is associated with proximal femur strength

Introduction Magnetic resonance imaging (MRI) is a promising medical imaging technique that we used to assess femoral neck cortical geometry.Objectives Our primary objective was to assess whether cortical bone in the femoral neck assessed by MRI was associated with failure load in a simulated sideways fall, with and without adjustment for total bone size. Our secondary objective was to assess the reliability of the MRI measurements.Materials and methods We imaged 34 human cadaveric proximal femora using MRI and dual-energy X-ray absorptiometry (DXA). MRI measurements of cross-sectional geometry at the femoral neck were the cortical cross-sectional area (CoCSA_MRI), second area moment of inertia (x axis; Ix_MRI), and section modulus (x axis; Zx_MRI). DXA images were analyzed with the standard Hologic protocol. From DXA, we report the areal bone mineral density (aBMD_DXA) in the femoral neck and trochanteric subregions of interest. The femora were loaded to failure at 100 mm/s in a sideways fall configuration (15° internal rotation, 10° adduction).Results and observations Failure load (N) was the primary outcome. We observed that the femoral neck CoCSA_MRI and Ix_MRI were strongly associated with failure load (r ²=0.46 and 0.48, respectively). These associations were similar to those between femoral neck aBMD and failure load (r ²=0.40), but lower than the associations between trochanteric aBMD and failure load (r ²=0.70).Conclusion We report that MRI holds considerable promise for measuring cortical bone geometry in the femoral neck and for predicting strength at the proximal femur.     

Distribution of bone density in the proximal femur and its association with hip fracture risk in older men: The osteoporotic fractures in men (MrOS) study

This prospective case‐cohort study aimed to map the distribution of bone density in the proximal femur and examine its association with hip fracture. We analyzed baseline quantitative computed tomography (QCT) scans in 250 men aged 65 years or older, which comprised a randomly‐selected subcohort of 210 men and 40 cases of first hip fracture during a mean follow‐up period of 5.5 years. We quantified cortical, trabecular, and integral volumetric bone mineral density (vBMD), and cortical thickness (CtTh) in four quadrants of cross‐sections along the length of the femoral neck (FN), intertrochanter (IT), and trochanter (TR). In most quadrants, vBMDs and CtTh were significantly (p < 0.05) lower in cases compared to the subcohort and these deficits were present across the entire proximal femur. To examine the association of QCT measurements with hip fracture, we merged the two quadrants in the medial and lateral aspects of the FN, IT, and TR. At most sites, QCT measurements were associated significantly (p < 0.001) with hip fracture, the hazard ratio (HR) adjusted for age, body mass index (BMI), and clinical site for a 1‐SD decrease ranged between 2.28 (95% confidence interval [CI], 1.44–3.63) to 6.91 (95% CI, 3.11–15.53). After additional adjustment for total hip (TH) areal BMD (aBMD), trabecular vBMDs at the FN, TR, and TH were still associated with hip fracture significantly (p < 0.001), the HRs ranged from 3.21 (95% CI, 1.65–6.24) for the superolateral FN to 6.20 (95% CI, 2.71–14.18) for medial TR. QCT measurements alone or in combination did not predict fracture significantly (p > 0.05) better than TH aBMD. With an area under the receiver operating characteristic curve (AUC) of 0.901 (95% CI, 0.852–0.950), the regression model combining TH aBMD, age, and trabecular vBMD predicted hip fracture significantly (p < 0.05) better than TH aBMD alone or TH aBMD plus age. These findings confirm that both cortical and trabecular bone contribute to hip fracture risk and highlight trabecular vBMD at the FN and TR as an independent risk factor. © 2012 American Society for Bone and Mineral Research.     

Effects of loading rate on strength of the proximal femur

Results from previous quasi-static mechanical tests indicate that femurs from elderly subjects fail in vitro at forces 50% below those available in a fall from standing height. However, bone is a rate-dependent material, and it is not known whether this imbalance is present at rates of loading which occur in a fall. Based on recent data on time to peak force and body positions at impact during simulated falls, we designed a high rate test of the femur in a loading configuration meant to represent a fall on the hip. We used elderly (mean age 73.5±7.4 (SD) years) and younger adult (32.7±12.8 years) cadaveric femurs to investigate whether (1) the strength, stiffness, and energy absorption capacity of the femur increases under high rate loading conditions; (2) elderly femurs have reduced strength, stiffness, and energy absorption capacity compared with younger adult femurs at this loading rate; and (3) densitometric and geometric measures taken at the hip correlate with the measured fracture loads. Femurs were scanned using dual-energy X-ray absorptiometry (DXA) and then tested to failure in a fall loading configuration at a displacement rate of 100 mm/second. The fracture load in elderly and younger adult femurs increased by about 20% with a 50-fold increase in displacement rate. However, energy absorption did not increase with displacement rate because of a twofold increase in stiffness at the higher loading rate. Age-related differences in strength and energy absorption capacity were consistent with those found previously for a displacement rate of 2 mm/second. There were moderate to strong correlations between fracture load and DXA variables, with the best correlation provided by cross-sectional area (r²=0.77) and bone mineral density (BMD) (r²=0.72) at the femoral neck. Our results indicate that, even at rates of loading applied during a fall, the estimated impact force in a fall on the hip is 35% greater than the average fracture load of the elderly femur. Moreover, the relationship we found between femoral neck BMD and fracture load indicates that an increase in femoral neck BMD of more than 20% would be required to raise the strength of the femur to the level of the impact load. As clinical trials of pharmacologic interventions have demonstrated increases in BMD of only a few percent at best, our results emphasize the continuing need for intervention strategies that focus on fall prevention and on reducing the severity of those falls that do occur.     

Bone mineral density of the proximal femur and lumbar spine in glucocorticoid-treated asthmatic patients

The importance of the proximal femur as a site of osteoporotic fractures, the development of techniques for bone mineral density (BMD) measurement at this site and the apparent selectivity of the osteopenic effects of glucorticoids have focused attention on the assessment of proximal femoral BMD in steroid-treated subjects. We have, therefore, measured BMD (Lunar DPX) in the lumbar spine and proximal femur of 31 asthmatic patients receiving long-term glucocorticoid therapy (mean ± SEM dose 16 ± 1 mg prednisone/day, mean duration 10 ± 2 years). BMD values expressed as the percentage of normal age- and sex-appropriate mean values, after weight adjustment, were as follows: lumbar spine 80 ± 2%, femoral neck 83 ± 2%, Ward's triangle 78 ± 3% and trochanter 86 ± 2%. All these values were significantly less than control (p<0.0001) and the decrement in BMD was more marked in Ward's triangle than at the other two femoral sites (p<0.05). In all regions BMD was unrelated to dose or duration of steroid treatment. It is concluded that there are reductions in the BMD of the lumbar spine and proximal femur in glucocorticoid-treated asthmatics, probably reflecting the mixed cortical/trabecular makeup of both regions.     

Right and left proximal femur analyses: Is there a need to do both?

The purpose of this study was to determine if differences existed between right and left proximal femur bone mineral density (BMD) in a group of women. Participants for the study were 198 women ranging in age from 16 to 73 years. Bone mineral densities of both proximal femurs (femoral neck, Ward's area, and trochanter) were assessed using dual energy X-ray absorptiometry (Lunar DPX). Mean (±SD) age, height, and weight of the participants were 32.9±18 years, 164±7.4 cm, and 64.9±12.1 kg, respectively. Significant differences between right and left femoral BMDs were found only in the trochanter. Overall, mean differences in BMD were low (neck=0.7%, Ward's =0.2%, and trochanter=1.9%) but individual variations were as high as 22%. Based on BMD z-scores of <−1.0, 84 women were classified as “at risk” for osteoporosis. When right and left z-scores were compared, misclassifications of at risk women were 4, 15, and 11 for neck, Ward's area, and trochanter, respectively. In conclusion, analyses of both right and left proximal femurs may not be necessary for either the researcher or the clinician.