Application of high-resolution skeletal imaging to measurements of volumetric BMD and skeletal microarchitecture in Chinese-American and white women: explanation of a paradox

Evaluation of bone microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT) in hemodialysis patients

Hemodialyzed patients have decreased bone strength not completely characterized. We evaluated bone microarchitecture in hemodialysis patients and compared it to that of subjects without renal disease by high-resolution peripheral quantitative computed tomography (HR-pQCT). Hemodialysis patients have a marked decreased in cortical density, thickness, and area with significant reduction in trabecular parameters that correlated with the severity of secondary hyperparathyroidism only in women.

INTRODUCTION

Although fracture risk is greatly increased in dialysis patients, the corresponding decreased in bone strength has not been completely characterized.

METHODS

We evaluated volumetric bone mineral density (vBMD) and bone microstructure by HR-pQCT at the distal radius and tibia in 50 hemodialyzed (HD) patients (30 females, mean age 53.2 ± 6 years and 20 males, mean age 59.1 ± 11 years) and 50 sex- and age-matched controls.

RESULTS

At the distal radius HD, women showed a 29% reduction in total and trabecular density and trabecular bone volume fraction (p < 0.0001) compared to controls. Trabecular number was reduced by 25% (p < 0.0001), while trabecular separation was increased by 51%. Cortical thickness (-40%, p < 0.0001) and cortical area (-42%, p < 0.0001) were the parameters most reduced, while compact density was the parameter least reduced (-15%, p < 0.0001). Similar findings were found at the tibia. In HD men, HR-pQCT at the distal radius and tibia showed a reduction in volumetric density and microstructure parameters to a lesser extent than in women. In the hemodialyzed group, cortical thickness at the radius was negatively correlated with age both in women and men. At the distal radius and tibia, we found significant negative correlations between Log iPTH and total alkaline phosphatase with cortical vBMD(r = -0.48, p < 0.01; r = -0.69, p < 0.001), thickness (-0.37, p < 0.05; r = -0.60, p < 0.001), and area ((r = -0.43, p = 0.02; r = -0.65, p < 0.001) but only in women.

CONCLUSION

We conclude that hemodialysis patients have a marked decreased in cortical density, thickness, and area with significant reduction in trabecular parameters that correlated with the severity of secondary hyperparathyroidism only in women.

Study of stress distribution in pedicle screws along a continuum of diameters: a three-dimensional finite element analysis

OBJECTIVE

To create a three-dimensional finite element model to identify the biomechanically optimal diameter of pedicle screws for placement in L1 vertebral bone.

METHODS

The effects of pedicle screws with different diameters on the maximum Von Mises stress in L1 vertebra bone were evaluated by a finite element method. Pedicle screw diameters ranging from 4.0 to 6.5 mm were assessed.

RESULTS

The simulation showed that, under axially oriented pullout forces, stress was decreased in all models when the diameter of screws was in the range of 4.0 mm to 6.5 mm. With a standard external load and a 6.5 mm diameter screw, load transferred to cortical and cancellous bone was reduced by 47.24% and 34.28%, respectively, and displacement of the screw was reduced by 21.35%. When the diameter was ≥5.0 mm, the variable of stress was stable in all models.

CONCLUSION

When the diameter of the screws is in the range of 4.0 mm to 6.5 mm, increasing the diameter of pedicle screw can improve the distribution of axial pullout stress on the screws, cortical bone and cancellous bone. Provided the bone mass permits it, pedicle screws with a diameter of not less than 5.0 mm should be chosen.

Epidemiology and structural basis of racial differences in fragility fractures in Chinese and Caucasians

Chinese have similar vertebral fracture prevalence but lower incidence of hip and distal forearm fractures than in Caucasians. The underlying structural and biomechanical basis of racial differences in bone fragility is still largely undefined but Chinese assemble their smaller appendicular skeleton with thicker cortices and trabeculae compared with Caucasians. Vertebral fracture prevalence is similar by race, but the incidence of hip and distal forearm fractures is lower in Chinese than in Caucasians. This racial dimorphism cannot be explained by differences in areal bone mineral density (aBMD) as aBMD is lower in Chinese mainly due to their smaller size. The underlying structural and biomechanical basis of racial differences in bone fragility is still largely undefined but Chinese assemble their smaller appendicular skeleton with more mineralised bone matrix within it; the cortices are thicker and perhaps less porous while trabeculae are fewer but thicker and more connected. This configuration produces a bone with a lower surface/volume ratio, which in turn reduces the surface available for remodelling to occur upon so that the lower surface/volume ratio may make the bone less exposed to remodelling and the thicker cortices and trabeculae less vulnerable to remodelling when it does occur during advancing age. However, prospective studies are needed to define racial differences at the age of onset, rate of bone loss from the intracortical, endocortical and trabecular components of the endosteal envelope and bone formation upon the periosteal envelope; notions of bone 'loss' are derived mainly from cross-sectional studies. Studies of the site- and surface-specific changes in bone modelling and remodelling are needed to better define racial differences in bone fragility in old age.

Bone structure and turnover in type 2 diabetes mellitus

SUMMARY

We compared skeletal parameters in type 2 diabetic (T2DM) and non-diabetic postmenopausal women. Bone structure by dual energy x-ray absorptiometry (DXA) and HR-pQCT was not different, although procollagen type 1 amino-terminal propeptide (P1NP) and osteocalcin levels were lower in T2DM.

INTRODUCTION

T2DM is associated with increased fracture risk, but, paradoxically, with higher cross-sectional bone density (BMD) as measured by DXA. We sought explanations to this puzzle by investigating detailed structural and biochemical skeletal parameters in T2DM.

METHODS

Cross-sectional comparison of 25 postmenopausal T2DM women and 25 matched controls using DXA, high-resolution peripheral quantitative computed tomography (HR-pQCT) and biochemical bone turnover markers.

RESULTS

BMD by DXA did not differ between T2DM and controls. HR-pQCT assessment also did not differ, with the exception of cortical area at the tibia, which tended to be lower in the diabetics (difference of 12 ± 6 [mean ± SD] mm, p = 0.06). P1NP and osteocalcin levels were lower in T2DM as compared to controls (P1NP, 34.3 ± 16 vs. 57.3 ± 28 ng/ml; p = 0.005; osteocalcin, 4.5 ± 2 vs. 6.2 ± 2 nmol/L; p = 0.001).

CONCLUSIONS

Postmenopausal women with T2DM had lower levels of bone formation markers as compared to controls. Aside from a possible decrease in cortical bone area at a weight-bearing site, bone structure was not altered in T2DM. Lower bone turnover may be a skeletal parameter that is present in T2DM.

Individual trabecula segmentation (ITS)-based morphological analysis of microscale images of human tibial trabecular bone at limited spatial resolution

Individual trabecula segmentation (ITS), a rigorous model-independent 3D morphological analysis, has been developed to assess trabecular plate and rod microstructure separately based on micro-computed tomographic (µCT) images. We examined the influence of the limited spatial resolution, noise, and artifact of high-resolution peripheral quantitative CT (HR-pQCT) on ITS measurements of human tibial trabecular bone. In comparison with measurements from "gold standard" µCT images (25 µm), decreased spatial resolution (40, 60, and 80 µm) of µCT had minimal influence on the correlations of the scale of trabecular plates (ie, plate bone volume fraction, thickness, and surface area) and the orientation (ie, axial bone volume fraction) and structural type (ie, plate tissue fraction) of the trabecular network. ITS measurements of HR-pQCT images correlated significantly with those of µCT images at a similar voxel size (80 µm, r = 0.71-0.94); correlations were stronger for plate-related parameters, suggesting that measurements of trabecular rods are more subject to noise and artifact associated with HR-pQCT imaging technology. In comparison with measurements of "gold standard" µCT images, the percent absolute errors of HR-pQCT measurements such as axial and plate bone volume fraction, plate number and tissue fraction, and plate and rod thickness (3.5% to 10.3%) were comparable with those of bone volume fraction (9.3%). For both HR-pQCT and µCT images, measurements of the scale and junction densities of trabecular plates and orientation and structural type were strong and positive indicators of the elastic modulus of trabecular bone (r = 0.59-0.95). We conclude that ITS measurements of HR-pQCT images are highly reflective of trabecular bone microarchitecture from a biomechanical perspective.

High-resolution computed tomography for clinical imaging of bone microarchitecture

BACKGROUND

The role of bone structure, one component of bone quality, has emerged as a contributor to bone strength. The application of high-resolution imaging in evaluating bone structure has evolved from an in vitro technology for small specimens to an emerging clinical research tool for in vivo studies in humans. However, many technical and practical challenges remain to translate these techniques into established clinical outcomes.

QUESTIONS/PURPOSES

We reviewed use of high-resolution CT for evaluating trabecular microarchitecture and cortical ultrastructure of bone specimens ex vivo, extension of these techniques to in vivo human imaging studies, and recent studies involving application of high-resolution CT to characterize bone structure in the context of skeletal disease.

METHODS

We performed the literature review using PubMed and Google Scholar. Keywords included CT, MDCT, micro-CT, high-resolution peripheral CT, bone microarchitecture, and bone quality.

RESULTS

Specimens can be imaged by micro-CT at a resolution starting at 1 μm, but in vivo human imaging is restricted to a voxel size of 82 μm (with actual spatial resolution of ~ 130 μm) due to technical limitations and radiation dose considerations. Presently, this mode is limited to peripheral skeletal regions, such as the wrist and tibia. In contrast, multidetector CT can assess the central skeleton but incurs a higher radiation burden on the subject and provides lower resolution (200-500 μm).

CONCLUSIONS

CT currently provides quantitative measures of bone structure and may be used for estimating bone strength mathematically. The techniques may provide clinically relevant information by enhancing our understanding of fracture risk and establishing the efficacy of antifracture for osteoporosis and other bone metabolic disorders.

Better skeletal microstructure confers greater mechanical advantages in Chinese-American women versus white women

Despite lower areal bone mineral density (aBMD), Chinese-American women have fewer fractures than white women. We hypothesized that better skeletal microstructure in Chinese-American women in part could account for this paradox. Individual trabecula segmentation (ITS), a novel image-analysis technique, and micro-finite-element analysis (µFEA) were applied to high-resolution peripheral quantitative computed tomography (HR-pQCT) images to determine bone microarchitecture and strength in premenopausal Chinese-American and white women. Chinese-American women had 95% and 80% higher plate bone volume fraction at the distal radius and tibia, respectively, as well as 20% and 18% higher plate number density compared with white women (p < .001). With similar rodlike characteristics, the plate-to-rod ratio was twice as high in the Chinese-American than in white trabecular bone (p < .001). Plate-rod junction density, a parameter indicating trabecular network connections, was 37% and 29% greater at the distal radius and tibia, respectively, in Chinese-American women (p < .002). Moreover, the orientation of the trabecular bone network was more axially aligned in Chinese-American women because axial bone volume fraction was 51% and 32% higher at the distal radius and tibia, respectively, than in white women (p < .001). These striking differences in trabecular bone microstructure translated into 55% to 68% (distal radius, p < .001) and 29% to 43% (distal tibia, p < .01) greater trabecular bone strength, as assessed by Young's moduli, in the Chinese-American versus the white group. The observation that Chinese-American women have a major microstructural advantage over white women may help to explain why their risk of fracture is lower despite their lower BMD.

Differences in bone microarchitecture between postmenopausal Chinese-American and white women

Chinese-American women have lower rates of hip and forearm fracture than white women despite lower areal bone density (aBMD) by dual X-ray absorptiometry (DXA). We recently reported higher trabecular (D(trab) ) and cortical (D(comp) ) bone density as well as greater trabecular (Tb.Th) and cortical thickness (C.Th) but smaller bone area (CSA), as measured by high-resolution peripheral quantitative computed tomography (HR-pQCT), in premenopausal Chinese-American compared with white women. These findings may help to account for the lower fracture rate among Chinese-American women but were limited to measurements in premenopausal women. This study was designed to extend these investigations to postmenopausal Chinese-American (n = 29) and white (n = 68) women. Radius CSA was 10% smaller in the Chinese-American versus the white group (p = .008), whereas their C.Th and D(comp) values were 18% and 6% greater (p < .001 for both). Tibial HR-pQCT results for cortical bone were similar to the radius, but Tb.Th was 11% greater in Chinese-American versus white women (p = .007). Tibial trabecular number and spacing were 17% lower and 20% greater, respectively, in Chinese-American women (p < .0001 for both). There were no differences in trabecular or whole-bone stiffness estimated by microstructural finite-element analysis, but Chinese-American women had a greater percentage of load carried by the cortical bone compartment at the distal radius and tibia. There was no difference in load distribution at the proximal radius or tibia. Whole-bone finite-element analysis may indicate that the thicker, more dense cortical bone and thicker trabeculae in postmenopausal Chinese-American women compensate for fewer trabeculae and smaller bone size.

Defining ethnic and racial differences in osteoporosis and fragility fractures

BACKGROUND

Osteoporotic fractures are a major public health issue. The literature suggests there are variations in occurrence of fractures by ethnicity and race.

QUESTIONS/PURPOSES

My purpose is to review current literature related to the influence of ethnicity and race on the (1) epidemiology of fracture; (2) prevalence of osteoporosis by bone mineral density; (3) consequences of osteoporotic hip fracture; (4) differences in risk fracture for fracture; and (5) disparities in screening, diagnosis, and treatment of osteoporosis.

METHODS

Current literature was selectively reviewed related to osteoporosis, ethnicity, and race.

RESULTS

Ethnicity and race, like sex, influence the epidemiology of fractures, with highest fracture rates in white women. Bone mineral density is higher in African Americans; however, these women are more likely to die after hip fracture, have longer hospital stays, and are less likely to be ambulatory at discharge. Consistent risk factors for fracture across ethnicity include older age, lower bone mineral density, previous history of fracture, and history of two or more falls. Ethnic and racial disparities exist in the screening, diagnosis, and treatment of osteoporosis.

CONCLUSIONS

Across ethnic and racial groups, more women experience fractures than the combined number of women who experience breast cancer, myocardial infarction, and coronary death in 1 year. Prevention efforts should target all women, irrespective of their race/ethnicity, especially if they have multiple risk factors.

Distribution of cortical bone in the femoral neck and hip fracture: a prospective case-control analysis of 143 incident hip fractures; the AGES-REYKJAVIK Study

In this prospective nested case-control study we analyzed the circumferential differences in estimated cortical thickness (Est CTh) of the mid femoral neck as a risk factor for osteoporotic hip fractures in elderly women and men. Segmental QCT analysis of the mid femoral neck was applied to assess cortical thickness in anatomical quadrants. The superior region of the femoral neck was a stronger predictor for hip fracture than the inferior region, particularly in men. There were significant gender differences in Est CTh measurements in the control group but not in the case group. In multivariable analysis for risk of femoral neck (FN) fracture, Est CTh in the supero-anterior (SA) quadrant was significant in both women and men, and remained a significant predictor after adjustment for FN areal BMD (aBMD, dimensions g/cm², DXA-like), (p=0.05 and p<0.0001, respectively). In conclusion, Est CTh in the SA quadrant best discriminated cases (n=143) from controls (n=298), especially in men. Cortical thinning superiorly in the hip might be of importance in determining resistance to fracture.

Trabecular bone deficits among Vietnamese immigrants

SUMMARY

Compared to white women, lower areal bone mineral density (aBMD) in middle-aged Vietnamese immigrants is due to reduced trabecular volumetric bone mineral density (vBMD), which in turn is associated with greater trabecular separation along with lower estrogen levels.

INTRODUCTION

The epidemiology of osteoporosis in Asian populations is still poorly known, but we previously found a deficit in lumbar spine aBMD among postmenopausal Southeast Asian women, compared to white women, that persisted after correction for bone size. This issue was revisited using more sophisticated imaging techniques.

METHODS

Twenty Vietnamese immigrants (age, 44-79 years) were compared to 162 same-aged white women with respect to aBMD at the hip, spine and wrist, vBMD at the hip and spine by quantitative computed tomography and vBMD and bone microstructure at the ultradistal radius by high-resolution pQCT. Bone turnover and sex steroid levels were assessed in a subset (20 Vietnamese and 40 white women).

RESULTS

The aBMD was lower at all sites among the Vietnamese women, but femoral neck vBMD did not differ from middle-aged white women. Significant differences in lumbar spine and ultradistal radius vBMD in the Vietnamese immigrants were due to lower trabecular vBMD, which was associated with increased trabecular separation. Bone resorption was elevated and bone formation depressed among the Vietnamese immigrants, although trends were not statistically significant. Serum estradiol was positively associated with trabecular vBMD in the Vietnamese women, but their estrogen levels were dramatically lower compared to white women.

CONCLUSIONS

Although reported discrepancies in aBMD among Asian women are mainly an artifact of smaller bone size, we identified a specific deficit in the trabecular bone among a sample of Vietnamese immigrants that may be related to low estrogen levels and which needs further study.

Radiological diagnostic progress in skeletal diseases

High-resolution bone imaging has made tremendous progress in the recent past. Both imaging modalities, computed tomography as well as MR imaging, have improved image quality. New developments such as HR-pQCT now make it possible to acquire in vivo images at peripheral sites with isotropic voxel size in a very short time. Further enhancements in the MR field have made it possible to image more central body sites such as the proximal femur with very high spatial resolution. New analysis methods can obtain direct estimates of biomechanical properties and important information related to bone's topology, as well as parameters of scale and orientation. These accomplishments will be essential in the noninvasive assessment of osteoporosis and fracture risk, will provide insight into the mechanisms behind bone loss, and will increasingly play a role as a tool for assessing treatment efficacy.

Abnormal microarchitecture and reduced stiffness at the radius and tibia in postmenopausal women with fractures

Measurement of areal bone mineral density (aBMD) by dual-energy x-ray absorptiometry (DXA) has been shown to predict fracture risk. High-resolution peripheral quantitative computed tomography (HR-pQCT) yields additional information about volumetric BMD (vBMD), microarchitecture, and strength that may increase understanding of fracture susceptibility. Women with (n = 68) and without (n = 101) a history of postmenopausal fragility fracture had aBMD measured by DXA and trabecular and cortical vBMD and trabecular microarchitecture of the radius and tibia measured by HR-pQCT. Finite-element analysis (FEA) of HR-pQCT scans was performed to estimate bone stiffness. DXA T-scores were similar in women with and without fracture at the spine, hip, and one-third radius but lower in patients with fracture at the ultradistal radius (p < .01). At the radius fracture, patients had lower total density, cortical thickness, trabecular density, number, thickness, higher trabecular separation and network heterogeneity (p < .0001 to .04). At the tibia, total, cortical, and trabecular density and cortical and trabecular thickness were lower in fracture patients (p < .0001 to .03). The differences between groups were greater at the radius than at the tibia for inner trabecular density, number, trabecular separation, and network heterogeneity (p < .01 to .05). Stiffness was reduced in fracture patients, more markedly at the radius (41% to 44%) than at the tibia (15% to 20%). Women with fractures had reduced vBMD, microarchitectural deterioration, and decreased strength. These differences were more prominent at the radius than at the tibia. HR-pQCT and FEA measurements of peripheral sites are associated with fracture prevalence and may increase understanding of the role of microarchitectural deterioration in fracture susceptibility. © 2010 American Society for Bone and Mineral Research.

Bone density, geometry, microstructure, and stiffness: Relationships between peripheral and central skeletal sites assessed by DXA, HR-pQCT, and cQCT in premenopausal women

High-resolution peripheral quantitative computed tomography (HR-pQCT) is a new in vivo imaging technique for assessing 3D microstructure of cortical and trabecular bone at the distal radius and tibia. No studies have investigated the extent to which measurements of the peripheral skeleton by HR-pQCT reflect those of the spine and hip, where the most serious fractures occur. To address this research question, we performed dual-energy X-ray absorptiometry (DXA), central QCT (cQCT), HR-pQCT, and image-based finite-element analyses on 69 premenopausal women to evaluate relationships among cortical and trabecular bone density, geometry, microstructure, and stiffness of the lumbar spine, proximal femur, distal radius, and distal tibia. Significant correlations were found between the stiffness of the two peripheral sites (r = 0.86), two central sites (r = 0.49), and between the peripheral and central skeletal sites (r = 0.56-0.70). These associations were explained in part by significant correlations in areal bone mineral density (aBMD), volumetric bone mineral density (vBMD), and cross-sectional area (CSA) between the multiple skeletal sites. For the prediction of proximal femoral stiffness, vBMD (r = 0.75) and stiffness (r = 0.69) of the distal tibia by HR-pQCT were comparable with direct measurements of the proximal femur: aBMD of the hip by DXA (r = 0.70) and vBMD of the hip by cQCT (r = 0.64). For the prediction of vertebral stiffness, trabecular vBMD (r = 0.58) and stiffness (r = 0.70) of distal radius by HR-pQCT were comparable with direct measurements of lumbar spine: aBMD by DXA (r = 0.78) and vBMD by cQCT (r = 0.67). Our results suggest that bone density and microstructural and mechanical properties measured by HR-pQCT of the distal radius and tibia reflect the mechanical competence of the central skeleton.

Bone mass and microarchitecture in CKD patients with fracture

Patients with predialysis chronic kidney disease (CKD) have increased risk for fracture, but the structural mechanisms underlying this increased skeletal fragility are unknown. We measured areal bone mineral density (aBMD) by dual-energy x-ray absorptiometry at the spine, hip, and radius, and we measured volumetric BMD (vBMD), geometry, and microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT) at the radius and tibia in patients with CKD: 32 with fracture and 59 without fracture. Patients with fracture had lower aBMD at the spine, total hip, femoral neck, and the ultradistal radius, the last having the strongest association with fracture. By HR-pQCT of the radius, patients with fracture had lower cortical area and thickness, total and trabecular vBMD, and trabecular number and greater trabecular separation and network heterogeneity. At the tibia, patients with fracture had significantly lower cortical area, thickness, and total and cortical density. Total vBMD at both radius and tibia most strongly associated with fracture. By receiver operator characteristic curve analysis, patients with longer duration of CKD had area under the curve of >0.75 for aBMD at both hip sites and the ultradistal radius, vBMD and geometry at the radius and tibia, and microarchitecture at the tibia. In summary, patients with predialysis CKD and fractures have lower aBMD by dual-energy x-ray absorptiometry and lower vBMD, thinner cortices, and trabecular loss by HR-pQCT. These density and structural differences may underlie the increased susceptibility to fracture among patients with CKD.

High-resolution imaging techniques for the assessment of osteoporosis

The importance of assessing the bone's microarchitectural make-up in addition to its mineral density in the context of osteoporosis has been emphasized in several publications. The high spatial resolution required to resolve the bone's microstructure in a clinically feasible scan time is challenging. At present, the best suited modalities meeting these requirements in vivo are high-resolution peripheral quantitative imaging (HR-pQCT) and magnetic resonance imaging (MRI). Whereas HR-pQCT is limited to peripheral skeleton regions like the wrist and ankle, MRI can also image other sites like the proximal femur but usually with lower spatial resolution. In addition, multidetector computed tomography has been used for high-resolution imaging of trabecular bone structure; however, the radiation dose is a limiting factor. This article provides an overview of the different modalities, technical requirements, and recent developments in this emerging field. Details regarding imaging protocols as well as image postprocessing methods for bone structure quantification are discussed.

Age- and gender-related differences in the geometric properties and biomechanical significance of intracortical porosity in the distal radius and tibia

Cortical bone contributes the majority of overall bone mass and bears the bulk of axial loads in the peripheral skeleton. Bone metabolic disorders often are manifested by cortical microstructural changes via osteonal remodeling and endocortical trabecularization. The goal of this study was to characterize intracortical porosity in a cross-sectional patient cohort using novel quantitative computational methods applied to high-resolution peripheral quantitative computed tomography (HR-pQCT) images of the distal radius and tibia. The distal radius and tibia of 151 subjects (57 male, 94 female; 47 +/- 16 years of age, range 20 to 78 years) were imaged using HR-pQCT. Intracortical porosity (Ct.Po) was calculated as the pore volume normalized by the sum of the pore and cortical bone volume. Micro-finite element analysis (microFE) was used to simulate 1% uniaxial compression for two scenarios per data set: (1) the original structure and (2) the structure with intracortical porosity artificially occluded. Differential biomechanical indices for stiffness (Delta K), modulus (Delta E), failure load (Delta F), and cortical load fraction (Delta Ct.LF) were calculated as the difference between original and occluded values. Regression analysis revealed that cortical porosity, as depicted by HR-pQCT, exhibited moderate but significant age-related dependence for both male and female cohorts (radius rho = 0.7; tibia rho = 0.5; p < .001). In contrast, standard cortical metrics (Ct.Th, Ct.Ar, and Ct.vBMD) were more weakly correlated or not significantly correlated with age in this population. Furthermore, differential microFE analysis revealed that the biomechanical deficit (Delta K) associated with cortical porosity was significantly higher for postmenopausal women than for premenopausal women (p < .001). Finally, porosity-related measures provided the only significant decade-wise discrimination in the radius for females in their fifties versus females in their sixties (p < .01). Several important conclusions can be drawn from these results. Age-related differences in cortical porosity, as detected by HR-pQCT, are more pronounced than differences in standard cortical metrics. The biomechanical significance of these structural differences increases with age for men and women and provides discriminatory information for menopause-related bone quality effects.