Response to High-Dose Vitamin D Supplementation Is Specific to Imaging Modality and Skeletal Site

High-dose vitamin D supplementation (4000 or 10,000 IU/d) in vitamin D-sufficient individuals results in a dose-dependent decrease in radius and tibia total bone mineral density (Tt.BMD) compared with 400 IU/d. This exploratory analysis examined whether the response to high-dose vitamin D supplementation depends on imaging modality and skeletal site. Participants were aged 55 to 70 years, not osteoporotic, with serum 25(OH)D 30 to 125 nM. Participants' radius and tibia were scanned on high-resolution peripheral quantitative computed tomography (HR-pQCT) to measure Tt.BMD, trabecular bone volume fraction (Tb.BV/TV), trabecular separation (Tb.Sp), cortical thickness (Ct.Th), and finite element analysis (FEA) estimated failure load. Three-dimensional image registration was used. Dual-energy X-ray absorptiometry (DXA) scans of the hip, spine, and radius measured areal BMD (aBMD) and trabecular bone score (TBS). Constrained linear mixed-effects models determined treatment group-by-time and treatment group-by-time-by-sex interactions. The treatment group-by-time interaction previously observed for radial Tt.BMD was observed at both ultradistal (UD, p < 0.001) and 33% (p < 0.001) aBMD sites. However, the treatment group-by-time-by-sex interaction observed for radial Tt.BMD was not observed with aBMD at either the UD or 33% site, and the 4000 and 400 groups did not differ. Registered radial FEA results mirrored Tt.BMD. An increase in Tb.Sp and decrease in Ct.Th underpinned dose-dependent changes in radial BMD and strength. We observed no effects in DXA-based aBMD at the hip or spine or TBS. At the tibia, we observed a time-by-treatment group effect for Tb.BV/TV. Given that DXA measures at the radius did not detect sex differences or differences between the 4000 and 400 groups, HR-pQCT at the radius may be more sensitive for examining bone changes after vitamin D supplementation. Although DXA did not reveal treatment effects at the hip or spine, whether that is a true skeletal site difference or a lack of modality sensitivity remains unclear. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Bone Microarchitecture in Transgender Adults: A Cross-Sectional Study

Gender-affirming hormone therapy aligns physical characteristics with an individual's gender identity, but sex hormones regulate bone remodeling and influence bone morphology. We hypothesized that trans men receiving testosterone have compromised bone morphology because of suppression of ovarian estradiol production, whereas trans women receiving estradiol, with or without anti-androgen therapy, have preserved bone microarchitecture. We compared distal radial and tibial microarchitecture using high-resolution peripheral quantitative computed tomography images in a cross-sectional study of 41 trans men with 71 cis female controls, and 40 trans women with 51 cis male controls. Between-group differences were expressed as standardized deviations (SD) from the mean in age-matched cisgender controls with 98% confidence intervals adjusted for cross-sectional area (CSA) and multiple comparisons. Relative to cis women, trans men had 0.63 SD higher total volumetric bone mineral density (vBMD; both p = 0.01). Cortical vBMD and cortical porosity did not differ, but cortices were 1.11 SD thicker (p < 0.01). Trabeculae were 0.38 SD thicker (p = 0.05) but otherwise no different. Compared with cis men, trans women had 0.68 SD lower total vBMD (p = 0.01). Cortical vBMD was 0.70 SD lower (p < 0.01), cortical thickness was 0.51 SD lower (p = 0.04), and cortical porosity was 0.70 SD higher (p < 0.01). Trabecular bone volume (BV/TV) was 0.77 SD lower (p < 0.01), with 0.57 SD fewer (p < 0.01) and 0.30 SD thicker trabeculae (p = 0.02). There was 0.56 SD greater trabecular separation (p = 0.01). Findings at the distal radius were similar. Contrary to each hypothesis, bone microarchitecture was not compromised in trans men, perhaps because aromatization of administered testosterone prevented bone loss. Trans women had deteriorated bone microarchitecture either because of deficits in microstructure before treatment or because the estradiol dosage was insufficient to offset reduced aromatizable testosterone. Prospective studies are needed to confirm these findings. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Impaired bone microarchitecture and strength in patients with tumor-induced osteomalacia

Some studies based on bone biopsy have demonstrated that in patients with tumor-induced osteomalacia (TIO) the mineralization process of the bone matrix is profoundly disturbed. However, the interrelationship between clinical and biochemical features and bone microarchitecture in this disease needs further analysis. With this purpose in mind, we set out three objectives: (i) to determine bone microarchitecture and estimated bone strength in a group of patients with tumor-induced osteomalacia using high-resolution peripheral quantitative computed tomography (HR-pQCT) and finite element analysis (FEA), (ii) to investigate correlations between duration of disease, biochemical features, bone density, HR-pQCT and FEA parameters, and (iii) to compare HR-pQCT and FEA parameters with a healthy control group. Ten patients with TIO were included. All patients had non-resolved disease. At the distal radius, all bone microarchitecture parameters were significantly affected in patients with TIO in comparison with healthy controls. At the distal tibia, all parameters were significantly impaired, except for trabecular thickness. All the parameters were more affected in the distal tibia than in the distal radius. Women with TIO (n = 7) had significantly lower bone strength parameters than healthy controls. In men (n = 3), bone strength parameters were significantly lower than in the control group at the distal tibia. Alkaline phosphatase levels exhibited a negative correlation with microarchitecture parameters, failure load, and stiffness. Higher levels of parathyroid hormone correlated with poorer microarchitecture parameters. We believe that in TIO, hormonal disturbances and the lack of mechanical stimulus specially converge to generate an extremely harmful combination for bone health. © 2021 American Society for Bone and Mineral Research (ASBMR).

Adverse Effects of High-Dose Vitamin D Supplementation on Volumetric Bone Density Are Greater in Females than Males

Three years of high-dose vitamin D supplementation (400 IU, 4000 IU, 10,000 IU) in healthy vitamin D-sufficient individuals aged 55 to 70 years (serum 25(OH)D 30-125 nmol/L at baseline), resulted in a negative dose-response relationship for bone density and strength. This study examined whether response differed between males and females. A total of 311 participants (53% male) were randomized to 400 IU (male = 61, female = 48), 4000 IU (male = 51, female = 49), or 10,000 IU (male = 53, female = 49) daily vitamin D₃ . Participants were scanned with high-resolution peripheral quantitative computed tomography (HR-pQCT) to measure total volumetric BMD (TtBMD) at baseline, 6, 12, 24, and 36 months. Finite element analysis estimated bone strength. Balance, physical function, and clinical biochemistry parameters were also assessed. Constrained linear mixed effects models determined time-by-treatment group-by-sex interactions. Baseline, 3-month, and 3-year levels of 25(OH)D were 76.3, 76.7, and 77.4 nmol/L (400 IU); 81.3, 115.3, and 132.2 (4000 IU); and 78.4, 188.0, and 144.4 (10,000 IU), respectively. There were significant time-by-treatment group-by-sex interactions for TtBMD at the radius (p = .002) and tibia (p = .005). Treatment with 4000 IU or 10,000 IU compared to 400 IU resulted in TtBMD losses in females, but this was not observed with males. After 3 years, females lost 1.8% (400 IU), 3.8% (4000 IU), and 5.5% (10,000 IU), whereas males lost 0.9% (400 IU), 1.3% (4000 IU), and 1.9% (10,000 IU) at the radius. At the tibia, losses in TtBMD were smaller, but followed a similar trend. There were no significant bone strength interactions. Vitamin D supplementation with 4000 IU or 10,000 IU, compared with 400 IU daily, resulted in greater losses of TtBMD over 3 years in healthy vitamin D-sufficient females, but not males. These results are clinically relevant, because vitamin D supplementation is widely administered to postmenopausal females for osteoporosis prevention. Our findings do not support a benefit of high-dose vitamin D supplementation for bone health, and raise the possibility of harm for females. © 2020 American Society for Bone and Mineral Research (ASBMR).

Age-, Site-, and Sex-Specific Normative Centile Curves for HR-pQCT-Derived Microarchitectural and Bone Strength Parameters in a Chinese Mainland Population

High-resolution peripheral quantitative computed tomography (HR-pQCT) is an advanced 3D imaging technology that has the potential to contribute to fracture risk assessment and early diagnosis of osteoporosis. However, to date no studies have sought to establish normative reference ranges for HR-pQCT measures among individuals from the Chinese mainland, significantly restricting its use. In this study, we collected HR-pQCT scans from 863 healthy Chinese men and women aged 20 to 80 years using the latest-generation scanner (Scanco XtremeCT II, Scanco Medical AG, Brüttisellen, Switzerland). Parameters including volumetric bone mineral density, bone geometry, bone microarchitecture, and bone strength were evaluated. Age-, site-, and sex-specific centile curves were established using generalized additive models for location, scale, and shape with age as the only explanatory variable. Based on established models, age-related variations for different parameters were also quantified. For clinical purposes, the expected values of HR-pQCT parameters for a defined age and a defined percentile or Z-score were provided. We found that the majority of trabecular and bone strength parameters reached their peak at 20 years of age, regardless of sex and site, then declined steadily thereafter. However, most of the cortical bone loss was observed after the age of 50 years. Among the measures, cortical porosity changed most dramatically, and overall, changes were more notable at the radius than the tibia and among women compared with men. Establishing such normative HR-pQCT reference data will provide an important basis for clinical and research applications in mainland China aimed at elucidating microstructural bone damage driven by different disease states or nutritional status. © 2020 American Society for Bone and Mineral Research.

Differing Effects of Zoledronic Acid on Bone Microarchitecture and Bone Mineral Density in Men Receiving Androgen Deprivation Therapy: A Randomized Controlled Trial

Androgen deprivation therapy (ADT) given to men with prostate cancer causes rapid and severe sex steroid deficiency, leading to increased bone remodeling and accelerated bone loss. To examine the effects of a single dose of zoledronic acid on bone microarchitecture, we conducted a 2-year randomized placebo controlled trial in 76 men, mean age (interquartile range [IQR]) 67.8 years (63.8 to 73.9) with non-metastatic prostate cancer commencing adjuvant ADT; 39 were randomized to zoledronic acid and 37 to matching placebo. Bone microarchitecture was measured using high-resolution peripheral quantitative computed tomography (HR-pQCT). Using a mixed model, mean adjusted differences (MAD; 95% confidence interval [95% CI]) between the groups are reported as the treatment effect at several time points. Over 24 months, zoledronic acid showed no appreciable treatment effect on the primary outcomes for total volumetric bone mineral density (vBMD); radius (6.7 mg HA/cm³ [-2.0 to 15.4], p = 0.21) and tibia (1.9 mg HA/cm³ [-3.3 to 7.0], p = 0.87). Similarly, there were no between-group differences in other measures of microarchitecture, with the exception of a modest effect of zoledronic acid over placebo in total cortical vBMD at the radius over 12 months (17.3 mgHA/cm³ [5.1 to 29.5]). In contrast, zoledronic acid showed a treatment effect over 24 months on areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry (DXA) at all sites, including lumbar spine (0.10 g/cm² [0.07 to 0.13]), p < 0.001), and total hip (0.04 g/cm² [0.03 to 0.05], p < 0.001). Bone remodeling markers were initially suppressed in the treatment group then increased but remained lower relative to placebo (MADs at 24 months CTX -176 ng/L [-275 to -76], p < 0.001; P1NP -18 mg/L [-32 to -5], p < 0.001). These findings suggest that a single dose of zoledronic acid over 2 years is ineffective in preventing the unbalanced bone remodeling and severe microstructural deterioration associated with ADT therapy. © 2020 American Society for Bone and Mineral Research.

Bone Mineral Is More Heterogeneously Distributed in the Femoral Heads of Osteoporotic and Diabetic Patients: A Pilot Study

Osteoporosis is associated with systemic bone loss, leading to a significant deterioration of bone microarchitecture and an increased fracture risk. Although recent studies have shown that the distribution of bone mineral becomes more heterogeneous because of estrogen deficiency in animal models of osteoporosis, it is not known whether osteoporosis alters mineral distribution in human bone. Type 2 diabetes mellitus (T2DM) can also increase bone fracture risk and is associated with impaired bone cell function, compromised collagen structure, and reduced mechanical properties. However, it is not known whether alterations in mineral distribution arise in diabetic (DB) patients’ bone. In this study, we quantify mineral content distribution and tissue microarchitecture (by μCT) and mechanical properties (by compression testing) of cancellous bone from femoral heads of osteoporotic (OP; n = 10), DB (n = 7), and osteoarthritic (OA; n = 7) patients. We report that though OP cancellous bone has significantly deteriorated compressive mechanical properties and significantly compromised microarchitecture compared with OA controls, there is also a significant increase in the mean mineral content. Moreover, the heterogeneity of the mineral content in OP bone is significantly higher than controls (+25%) and is explained by a significant increase in bone volume at high mineral levels. We propose that these mineral alterations act to exacerbate the already reduced bone quality caused by reduced cancellous bone volume during osteoporosis. We show for the first time that cancellous bone mineralization is significantly more heterogeneous (+26%) in patients presenting with T2DM compared with OA (non‐DB) controls, and that this heterogeneity is characterized by a significant increase in bone volume at low mineral levels. Despite these mineralization changes, bone microarchitecture and mechanical properties are not significantly different between OA groups with and without T2DM. Nonetheless, the observed alterations in mineral heterogeneity may play an important tissue‐level role in bone fragility associated with OP and DB bone. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Comparative Effect of rhPTH(1-84) on Bone Mineral Density and Trabecular Bone Score in Hypoparathyroidism and Postmenopausal Osteoporosis

Parathyroid hormone (PTH) (1-84) improves lumbar spine (LS) areal bone mineral density (aBMD) and trabecular bone score (TBS) in hypoparathyroidism over a 2-year treatment period. Studies in osteoporosis have shown that with PTH(1-34) there is a significant increase in LS aBMD and TBS. In this article, we provide new data comparing the effects of the same form of PTH, namely recombinant human PTH, rhPTH(1-84), on aBMD and TBS in hypoparathyroid and osteoporotic patients over an 18-month treatment period. We studied 19 premenopausal (mean age 45.8 ± 11.8 years) and 16 postmenopausal (71 ± 8.4 years) hypoparathyroid women and 38 women with postmenopausal osteoporosis (71 ± 8.3 years). DXA (hologic) at LS, femoral neck, total hip, and distal one-third radius was assessed. Site-matched LS TBS data were extracted from deidentified spine DXA scans using the TBS iNsight software (version 2.1; Medimaps, Geneva, Switzerland). We observed a significant increase in LS aBMD in premenopausal and postmenopausal hypoparathyroid (3 ± 1.1%, p < 0.02 and 3.1 ± 1.4%, p < 0.05, respectively) and osteoporosis (6.2 ± 1.1%, p < 0.0001) patients after 18 months. There was a significant increase (3 ± 1.5%, p = 0.05) in TBS in premenopausal hypoparathyroid patients. A change in TBS was not observed in either postmenopausal group. One-third radius aBMD significantly declined in postmenopausal hypoparathyroid (-3.6 ± 1.1%, p < 0.01) and osteoporosis (-8 ± 1.4%, p < 0.0001) patients. Overall, there was a significantly greater increase in TBS in premenopausal hypoparathyroid than in osteoporosis patients (p < 0.0001) after adjusting for baseline values, age, BMI, and average daily dose of rhPTH(1-84). Comparing only postmenopausal women, the LS aBMD increase was greater in osteoporotic than hypoparathyroid subjects (p < 0.01). Our results demonstrate that rhPTH(1-84) administered for 18 months increases trabecular aBMD in hypoparathyroidism and postmenopausal osteoporosis with greater gains observed in the subjects with osteoporosis. The data suggest different effects of PTH on bone depending on the baseline skeletal structure, skeletal dynamics, compartments, and menopausal status. © 2018 American Society for Bone and Mineral Research.

Chinese Women in Both the United States and Hong Kong Have Cortical Microstructural Advantages and More Trabecular Plates Compared With White Women

We cross-sectionally compared racial differences in bone quality between Chinese women in the United States (US) and Hong Kong (HK) with white women. A total of 514 women were included. We measured bone geometry, mass, microstructure, and stiffness by high-resolution peripheral quantitative computed tomography (HR-pQCT), individual trabecula segmentation (ITS), and microfinite element analysis (μFEA). After adjustment for age and body mass index (BMI), premenopausal Chinese women in the US and HK had smaller bone area but greater radial cortical (Ct.) thickness and Ct. and trabecular (Tb.) volumetric bone mineral density (vBMD) versus white women but did not differ from each other. At the radius, Tb. number was lower and spacing greater in Chinese women from HK and the US versus white women, whereas Chinese women did not differ from each other. Tb. thickness was highest in Chinese women from HK, intermediate in Chinese-Americans, and lowest in white women. Chinese women had more trabecular plates versus white women, leading to greater age- and BMI-adjusted stiffness for premenopausal Chinese women in HK and the US (both p < 0.05) versus white women. Tibial differences were similar in premenopausal women; analogous trends in microstructure were present in postmenopausal women at the tibia, although stiffness did not differ. In contrast, at the radius, cortical, plate-to-rod ratio, and stiffness were similar between postmenopausal HK and white women. Adjusting for age, weight, and height rather than age and BMI tended to reduce differences in bone size and Tb. parameters but accentuate cortical differences such that Chinese premenopausal women in both locations and postmenopausal women from HK had higher stiffness at both skeletal sites compared with white women. Compared with white women, Chinese women in the US and HK have vBMD and microstructural advantages leading to higher or similar mechanical competence in pre- and postmenopausal women, respectively, despite smaller bone size.

Single-Limb Irradiation Induces Local and Systemic Bone Loss in a Murine Model

Increased fracture risk is commonly reported in cancer patients receiving radiotherapy, particularly at sites within the field of treatment. The direct and systemic effects of ionizing radiation on bone at a therapeutic dose are not well-characterized in clinically relevant animal models. Using 20-week-old male C57Bl/6 mice, effects of irradiation (right hindlimb; 2 Gy) on bone volume and microarchitecture were evaluated prospectively by microcomputed tomography and histomorphometry and compared to contralateral-shielded bone (left hindlimb) and non-irradiated control bone. One week postirradiation, trabecular bone volume declined in irradiated tibias (-22%; p < 0.0001) and femurs (-14%; p = 0.0586) and microarchitectural parameters were compromised. Trabecular bone volume declined in contralateral tibias (-17%; p = 0.003), and no loss was detected at the femur. Osteoclast number, apoptotic osteocyte number, and marrow adiposity were increased in irradiated bone relative to contralateral and non-irradiated bone, whereas osteoblast number was unchanged. Despite no change in osteoblast number 1 week postirradiation, dynamic bone formation indices revealed a reduction in mineralized bone surface and a concomitant increase in unmineralized osteoid surface area in irradiated bone relative to contralateral and non-irradiated control bone. Further, dose-dependent and time-dependent calvarial culture and in vitro assays confirmed that calvarial osteoblasts and osteoblast-like MC3T3 cells were relatively radioresistant, whereas calvarial osteocyte and osteocyte-like MLO-Y4 cell apoptosis was induced as early as 48 hours postirradiation (4 Gy). In osteoclastogenesis assays, radiation exposure (8 Gy) stimulated murine macrophage RAW264.7 cell differentiation, and coculture of irradiated RAW264.7 cells with MLO-Y4 or murine bone marrow cells enhanced this effect. These studies highlight the multifaceted nature of radiation-induced bone loss by demonstrating direct and systemic effects on bone and its many cell types using clinically relevant doses; they have important implications for bone health in patients treated with radiation therapy.

Bone density, microstructure and strength in obese and normal weight men and women in younger and older adulthood

Obesity is associated with greater areal BMD (aBMD) and is considered protective against hip and vertebral fracture. Despite this, there is a higher prevalence of lower leg and proximal humerus fracture in obesity. We aimed to determine if there are site-specific differences in BMD, bone structure, or bone strength between obese and normal-weight adults. We studied 100 individually-matched pairs of normal (body mass index [BMI] 18.5 to 24.9 kg/m2) and obese (BMI >30 kg/m2) men and women, aged 25 to 40 years or 55 to 75 years. We assessed aBMD at the whole body (WB), hip (TH), and lumbar spine (LS) with dual-energy X-ray absorptiometry (DXA), LS trabecular volumetric BMD (Tb.vBMD) by quantitative computed tomography (QCT), and vBMD and microarchitecture and strength at the distal radius and tibia with high-resolution peripheral QCT (HR-pQCT) and micro-finite element analysis. Serum type 1 procollagen N-terminal peptide (P1NP) and collagen type 1 C-telopeptide (CTX) were measured by automated electrochemiluminescent immunoassay (ECLIA). Obese adults had greater WB, LS, and TH aBMD than normal adults. The effect of obesity on LS and WB aBMD was greater in older than younger adults (p < 0.01). Obese adults had greater vBMD than normal adults at the tibia (p < 0.001 both ages) and radius (p < 0.001 older group), thicker cortices, higher cortical BMD and tissue mineral density, lower cortical porosity, higher trabecular BMD, and higher trabecular number than normal adults. There was no difference in bone size between obese and normal adults. Obese adults had greater estimated failure load at the radius (p < 0.05) and tibia (p < 0.01). Differences in HR-pQCT measurements between obese and normal adults were seen more consistently in the older than the younger group. Bone turnover markers were lower in obese than in normal adults. Greater BMD in obesity is not an artifact of DXA measurement. Obese adults have higher BMD, thicker and denser cortices, and higher trabecular number than normal adults. Greater differences between obese and normal adults in the older group suggest that obesity may protect against age-related bone loss and may increase peak bone mass.

Co-administration of antiresorptive and anabolic agents: a missed opportunity

Co-administration of antiresorptive and anabolic therapies has appeal because these treatments target the two main abnormalities in bone remodeling responsible for bone loss and microstructural deterioration. Antiresorptives reduce the number of basic multicellular units (BMUs) remodeling bone and reduce the volume of bone each BMU resorbs. Intermittent parathyroid hormone (PTH) increases the volume of bone formed by existing BMUs and those generated by PTH administration. PTH also increases bone formation by stimulating the differentiation, maturation, and longevity of osteoblast lineage cells residing upon quiescent bone surfaces. Despite these rationally targeted actions, enthusiasm for this approach waned when combined therapy blunted the increase in areal bone mineral density (aBMD) relative to that produced by PTH. Although many studies have since reported additive effects of combined therapy, whatever the aBMD result (blunting, additive, or null), these outcomes give little, if any, insight into changes in bone's material composition or microstructure and give misleading information concerning the net effects on bone strength. Combined therapy remains a potentially valuable approach to therapy. Because studies of antifracture efficacy comparing combined with single therapy are unlikely to be performed in humans, efforts should be directed toward improving methods of quantifying the net effects of combined therapy on bone's material composition, microarchitecture, and strength.

Comparative effects of teriparatide, denosumab, and combination therapy on peripheral compartmental bone density, microarchitecture, and estimated strength: the DATA-HRpQCT Study

Combined teriparatide and denosumab increases spine and hip bone mineral density more than either drug alone. The effect of this combination on skeletal microstructure and microarchitecture, however, is unknown. Because skeletal microstructure and microarchitecture are important components of skeletal integrity, we performed high-resolution peripheral quantitative computed tomography (HR-pQCT) assessments at the distal tibia and radius in postmenopausal osteoporotic women randomized to receive teriparatide 20 µg daily (n = 31), denosumab 60 mg every 6 months (n = 33), or both (n = 30) for 12 months. In the teriparatide group, total volumetric bone mineral density (vBMD) did not change at either anatomic site but increased in both other groups at both sites. The increase in vBMD at the tibia was greater in the combination group (3.1 ± 2.2%) than both the denosumab (2.2 ± 1.9%) and teriparatide groups (-0.3 ± 1.9%) (p < 0.02 for both comparisons). Cortical vBMD decreased by 1.6 ± 1.9% at the tibia and by 0.9 ± 2.8% at the radius in the teriparatide group, whereas it increased in both other groups at both sites. Tibia cortical vBMD increased more in the combination group (1.5 ± 1.5%) than both monotherapy groups (p < 0.04 for both comparisons). Cortical thickness did not change in the teriparatide group but increased in both other groups. The increase in cortical thickness at the tibia was greater in the combination group (5.4 ± 3.9%) than both monotherapy groups (p < 0.01 for both comparisons). In the teriparatide group, radial cortical porosity increased by 20.9 ± 37.6% and by 5.6 ± 9.9% at the tibia but did not change in the other two groups. Bone stiffness and failure load, as estimated by finite element analysis, did not change in the teriparatide group but increased in the other two groups at both sites. Together, these findings suggest that the use of denosumab and teriparatide in combination improves HR-pQCT measures of bone quality more than either drug alone and may be of significant clinical benefit in the treatment of postmenopausal osteoporosis.

Lower cortical porosity and higher tissue mineral density in Chinese American versus white women

Asian women have lower rates of hip and forearm fractures compared to other racial groups despite lower areal bone mineral density (aBMD). We have demonstrated microarchitectural differences, including greater cortical thickness (Ct.Th) and cortical volumetric BMD (Ct.BMD), in Chinese American versus white women. Yet it is not known whether greater Ct.BMD in Chinese American women is a result of greater tissue mineral density (TMD) or reduced cortical porosity (Ct.Po). Using an advanced segmentation algorithm based on high-resolution peripheral quantitative computed tomography (HR-pQCT) images, we tested the hypothesis that Chinese American women have better cortical skeletal integrity owing to lower Ct.Po and higher Ct.TMD compared with white women. A total of 78 Chinese American women (49 premenopausal and 29 postmenopausal) and 114 white women (46 premenopausal and 68 postmenopausal) were studied. Premenopausal Chinese American versus white women had greater Ct.Th, Ct.BMD, and Ct.TMD at both the radius and tibia, and decreased Ct.Po (p < 0.05). A similar pattern was observed between postmenopausal Chinese American and white women. As expected, postmenopausal versus premenopausal women had lower Ct.BMD at the radius and tibia in both races (p < 0.001). Ct.Po largely increased between premenopausal and postmenopausal women, whereas Ct.TMD decreased by 3% to 8% (p < 0.001) in both races. Age-related differences in Ct.Po and Ct.TMD did not differ by race. In summary, both reduced Ct.Po and greater Ct.TMD explain higher Ct.BMD in Chinese American versus white women. Thicker and preserved cortical bone structure in Chinese American women may contribute to greater resistance to fracture compared to white women.

Trabecular bone score: a noninvasive analytical method based upon the DXA image

The trabecular bone score (TBS) is a gray-level textural metric that can be extracted from the two-dimensional lumbar spine dual-energy X-ray absorptiometry (DXA) image. TBS is related to bone microarchitecture and provides skeletal information that is not captured from the standard bone mineral density (BMD) measurement. Based on experimental variograms of the projected DXA image, TBS has the potential to discern differences between DXA scans that show similar BMD measurements. An elevated TBS value correlates with better skeletal microstructure; a low TBS value correlates with weaker skeletal microstructure. Lumbar spine TBS has been evaluated in cross-sectional and longitudinal studies. The following conclusions are based upon publications reviewed in this article: 1) TBS gives lower values in postmenopausal women and in men with previous fragility fractures than their nonfractured counterparts; 2) TBS is complementary to data available by lumbar spine DXA measurements; 3) TBS results are lower in women who have sustained a fragility fracture but in whom DXA does not indicate osteoporosis or even osteopenia; 4) TBS predicts fracture risk as well as lumbar spine BMD measurements in postmenopausal women; 5) efficacious therapies for osteoporosis differ in the extent to which they influence the TBS; 6) TBS is associated with fracture risk in individuals with conditions related to reduced bone mass or bone quality. Based on these data, lumbar spine TBS holds promise as an emerging technology that could well become a valuable clinical tool in the diagnosis of osteoporosis and in fracture risk assessment.

Risedronate slows or partly reverses cortical and trabecular microarchitectural deterioration in postmenopausal women

During early menopause, steady-state bone remodeling is perturbed; the number of basic multicellular units (BMUs) excavating cavities upon the endosteal surface exceeds the number (generated before menopause) concurrently refilling. Later in menopause, steady-state is restored; the many BMUs generated in early menopause refill as similarly large numbers of BMUs concurrently excavate new cavities. We hypothesized that risedronate reduces the number of cavities excavated. However, in younger postmenopausal women, the fewer cavities excavated will still exceed the fewer BMUs now refilling, so net porosity increases, but less than in controls. In older postmenopausal women, the fewer cavities excavated during treatment will be less than the many (generated during early menopause) now refilling, so net porosity decreases and trabecular volumetric bone mineral density (vBMD) increases. We recruited 324 postmenopausal women in two similarly designed double-blind placebo-controlled studies that included 161 younger (Group 1, ≤ 55 years) and 163 older (Group 2, ≥ 55 years) women randomized 2:1 to risedronate 35 mg/week or placebo. High-resolution peripheral computed tomography was used to image the distal radius and tibia. Cortical porosity was quantified using the StrAx1.0 software. Risedronate reduced serum carboxyterminal cross-linking telopeptide of type 1 bone collagen (CTX-1) and serum amino-terminal propeptide of type 1 procollagen (P1NP) by ∼50%. In the younger group, distal radius compact-appearing cortex porosity increased by 4.2% ± 1.6% (p = 0.01) in controls. This was prevented by risedronate. Trabecular vBMD decreased by 3.6% ± 1.4% (p = 0.02) in controls and decreased by 1.6% ± 0.6% (p = 0.005) in the risedronate-treated group. In the older group, changes did not achieve significance apart from a reduction in compact-appearing cortex porosity in the risedronate-treated group (0.9% ± 0.4%, p = 0.047). No between-group differences reached significance. Results were comparable at the distal tibia. Between-group differences were significant for compact-appearing cortex porosity (p = 0.005). Risedronate slows microstructural deterioration in younger and partly reverses it in older postmenopausal women, features likely to contribute to antifracture efficacy.