Baseline BMD and bone loss at distal radius measured by peripheral quantitative computed tomography in peri- and postmenopausal Hong Kong Chinese women

Peak trabecular bone microstructure predicts rate of estrogen-deficiency-induced bone loss in rats

Postmenopausal osteoporosis affects a large number of women worldwide. Reduced estrogen levels during menopause lead to accelerated bone remodeling, resulting in low bone mass and increased fracture risk. Both peak bone mass and the rate of bone loss are important predictors of postmenopausal osteoporosis risk. However, whether peak bone mass and/or bone microstructure directly influence the rate of bone loss following menopause remains unclear. Our study aimed to establish the relationship between peak bone mass/microstructure and the rate of bone loss in response to estrogen deficiency following ovariectomy (OVX) surgery in rats of homogeneous background by tracking the skeletal changes using in vivo micro-computed tomography (μCT) and three-dimensional (3D) image registrations. Linear regression analyses demonstrated that the peak bone microstructure, but not peak bone mass, was highly predictive of the rate of OVX-induced bone loss. In particular, the baseline trabecular thickness was found to have the highest correlation with the degree of OVX-induced bone loss and trabecular stiffness reduction. Given the same bone mass, the rats with thicker baseline trabeculae had a lower rate of trabecular microstructure and stiffness deterioration after OVX. Moreover, further evaluation to track the changes within each individual trabecula via our novel individual trabecular dynamics (ITD) analysis suggested that a trabecular network with thicker trabeculae is less likely to disconnect or perforate in response to estrogen deficiency, resulting a lower degree of bone loss. Taken together, these findings indicate that the rate of estrogen-deficiency-induced bone loss could be predicted by peak bone microstructure, most notably the trabecular thickness. Given the same bone mass, a trabecular bone phenotype with thin trabeculae may be a risk factor toward accelerated postmenopausal bone loss.

Dimorphism in axial and appendicular dimensions, cortical and trabecular microstructure and matrix mineral density in Chinese and Caucasian women

INTRODUCTION

Appendicular fractures are less common in Chinese than Caucasian women. Bone mineral density (BMD) is lower, not higher than in Caucasians because Chinese have smaller appendicular dimensions than Caucasians. However, smaller bones may offset the liability to fracture by being assembled with a more robust microstructure. We hypothesized that Chinese assemble an appendicular skeleton with a thicker, less porous and more mineralized cortex that is less deteriorated in advanced age than in Caucasians.

METHODS

We compared anthropometry in 477 Chinese and 278 Caucasian women and compared bone microstructure using high-resolution peripheral quantitative computed tomography in another cohort of 186 Chinese and 381 Caucasian women aged 18 to 86 years, all living in Melbourne, Australia. Trabecular plate (p) and rod (r) bone volume/total volume (BV/TV) were quantified using individual trabecula segmentation (ITS). Bone strength was estimated using micro-finite element analysis (μFEA).

RESULTS

Premenopausal Chinese were shorter than Caucasian women, mainly due to shorter leg length. Distal radial total cross sectional area (CSA) was 14.8% smaller (p < 0.001). After adjusting for age and total CSA, Chinese had similar cortical and medullary areas but 0.30 SD lower cortical porosity and 0.27 SD higher matrix mineral density (both p < 0.05). Trabecular plate-to-rod ratio was 0.55 SD higher due to a 0.41 SD higher pBV/TV and 0.36 SD lower rBV/TV (p ranging 0.001 to 0.023). Chinese also had 0.36 SD greater whole bone stiffness and 0.36 SD greater failure load than Caucasians (both p < 0.05). After adjusting for age and total CSA, postmenopausal Chinese had 3.3% smaller cortical area, medullary area was 2.1% larger, cortical porosity was no lower, matrix mineral density and pBV/TV were no higher compared with Caucasians at the distal radius. Whole bone stiffness was 0.39 SD lower and failure load was 0.40 SD lower in Chinese (both p < 0.05).

CONCLUSION

Chinese build a more robust skeleton than Caucasians during growth, an advantage not observed in advanced age due to greater bone loss or race-specific secular trends in bone morphology.

Effects of tai chi exercise on bone health in perimenopausal and postmenopausal women: a systematic review and meta-analysis

Tai chi exercise may have positive effects on bone health in perimenopausal and postmenopausal women. This systematic review is the first to summarize evidence to clarify the efficacy of tai chi exercise in bone health. The benefits of tai chi exercise on bone health remain unclear; further studies are needed. Emerging randomized controlled trials (RCTs) exploring the efficacy of tai chi exercise on bone health among older women, but yielded inconclusive results. Our objective is to conduct a systematic review to evaluate evidence from RCTs to clarify the efficacy of tai chi exercise on bone mineral density (BMD), and bone turnover markers (BTM) in perimenopausal and postmenopausal women. Six electronic databases were searched, and reference lists of systematic reviews and identified studies from the search strategy were also screened. We included all RCTs that investigate tai chi exercise for bone health in perimenopausal and postmenopausal women. Data selection, extraction, and evaluation of risk of bias were performed independently by two reviewers. Ten trials detailed in 11 articles were included. Six of the 11 studies reported positive outcomes on bone health. Results of our meta-analysis showed a significant effect of tai chi exercise on BMD change at the spine compared with no treatment in perimenopausal and postmenopausal women. When tai chi exercise combined with a calcium supplement was compared with the calcium supplement alone, the result of BMD change at the spine showed no significant effect. Because the measurable effect observed was minimal, and due to the low quality of methodology of the studies, we conclude that the result is of limited reliability. Tai chi exercise may have benefits on bone health in perimenopausal and postmenopausal women, but the evidence is sometimes weak, poor, and inconsistent. Consequently, only limited conclusions can be drawn regarding the efficacy of tai chi exercise on bone health. Further well designed studies with low risk of bias are needed.

Atypical femoral fractures and current management

With the rapid increase in patients receiving bisphosphonates (BPs) for treating osteoporosis, one of the clinical complications associated with its long-term use is atypical femoral fractures (AFFs). Although the absolute risk for AFFs is low and it was a consensus that AFFs were acceptable compared with the amount of osteoporotic fractures BPs have prevented, epidemiological studies have proved that BPs had a strong association with AFFs and possibly more people were going to suffer from this adverse effect with wide prescriptions of this drug. In addition, AFFs seemed to have impaired ability to heal. Thus, to understand the mechanism(s) behind AFFs is important and desirable for considering preventive measures. This article reviewed the clinical features of AFFs as well as potential underlining pathological characteristics, such as the decreased turnover rate caused by BPs that led to multiple-level alternations, e.g., changes not only at cellular and tissue levels, but also related to changes in bone micro- and macrostructure and organic/inorganic contents, leading to potentially compromised mechanical properties of cortical bone when exposed to prolonged BP therapy. Severely suppressed bone turnover may also be the underlying mechanism for impaired fracture healing in patients with AFFs. The rising concerns about the risk for AFFs in nonosteoporotic patients receiving high-dose BPs to treat cancers were also discussed. Detailed investigation will help develop potential targeted pharmacological treatments such as parathyroid hormone. In addition, potential innovative internal fixation implants were discussed with regard to dynamic and biological fixation for enhancing AFF repair.

Five-year follow-up study of a kidney-tonifying herbal Fufang for prevention of postmenopausal osteoporosis and fragility fractures

To observe the kidney-tonifying herbal Fufangs with phytoestrogenic epimedium for prevention of postmenopausal osteoporosis with both bone mineral density (BMD) and fracture as study endpoints, a 5-year multicenter follow-up study in 194 postmenopausal women (47-70 years old) was conducted in which the subjects were given oral administration of herbal Fufang (10 g/day, twice per day, n = 101) or placebo (n = 93). Both groups were supplemented daily with calcium (600 mg) and vitamin D (400 IU). BMD at distal radius, potential adverse events, and fracture incidence were evaluated at baseline and at 6, 12, 24, 36, 48, and 60 months. At the end of 5 years, 155 subjects had completed the study, with better adherence in the treatment group (13% dropouts, n = 88 at year 5) as compared with the control group (28% dropouts, n = 67 at year 5) (P < 0.05). No notable adverse events were observed in either group. In the treatment group BMD increased significantly from baseline (0.211 ± 0.022 g/cm(2)) to the end of the study (0.284 ± 0.015 g/cm(2)), whereas the control group decreased significantly from baseline (0.212 ± 0.023 g/cm(2)) to 5 years later (0.187 ± 0.022 g/cm(2)) (P < 0.05). The fracture incidence was 2.4 fold lower in the treatment group than in the control group, with a relative risk of 0.57 for the treatment group (95% CI, 0.43-0.70, P < 0.05). In conclusion, in addition to the beneficial effects of oral herbal Fufang on prevention of postmenopausal bone loss, this 5-year multi-center clinical study demonstrated for the first time its potential for reduction in fragility fracture incidence.

Prospective analysis of a first MTP total joint replacement. Evaluation by bone mineral densitometry, pedobarography, and visual analogue score for pain

BACKGROUND

We hypothesized that a total replacement of the first metatarsophalangeal joint (MTP-1) would alter the walking pattern with medialisation of the ground reaction force (GRF) of the foot and subsequently cause an increase in bone mineral density (BMD) in the medial metatarsal bones and a decline of BMD in the lateral metatarsal bones.

METHODS

Twelve patients receiving total joint replacements (Roto-Glide(®)) of MTP-1 were enrolled in a prospective cohort. BMD and pedobarography of the heel bone and the metatarsal heads were performed preoperatively and at least 12 months postoperatively.

RESULTS

BMD in the lateral metatarsals and GRF under the lateral column of the operated feet decreased significantly on the operated feet.

CONCLUSIONS

Total joint replacement of MTP-1 tends to reduce GRF under the lateral column of the foot causing a corresponding decline in BMD and pedobarographic measures. Our findings support the further use of the Roto-Glide(®) prosthesis for osteoarthritis of the first metatarsophalangeal joint.

Cortisol secretion, bone health, and bone loss: a cross-sectional and prospective study in normal non-osteoporotic women in the early postmenopausal period

OBJECTIVE

The aim of the study was to evaluate the relationship between cortisol secretion, bone health, and bone loss in a cohort of normal women in the early postmenopausal period.

METHODS

We measured lumbar and hip bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) and heel ultrasound parameters in 82 healthy, nonosteoporotic (lumbar T-score ≥-2.0) women (median age 52.5 years, range 42-61). These women were examined in two sessions, 1 year apart, in the early postmenopausal period (onset of menopause between 6 and 60 months). Parameters of the hypothalamic-pituitary-adrenal (HPA) axis function were morning serum cortisol, morning and midnight salivary cortisol, 24-h urinary free cortisol (UFC), serum cortisol after 0.5 and 1 mg overnight dexamethasone, and DHEA-S.

RESULTS

In multiple regression analyses, the following significant inverse correlations were found: i) lumbar BMD and either 24-h UFC (P<0.005) or morning serum cortisol (P<0.05), ii) total femur and femoral neck BMD with morning serum cortisol (P=0.05 and P<0.05), and iii) heel ultrasound stiffness index and midnight salivary cortisol (P<0.005). The annual rate of change in lumbar and femoral BMD did not correlate with any of the above-mentioned hormonal variables. No difference was found in the parameters of HPA axis function in slow (loss of BMD <1%) vs fast (loss of BMD ≥3%) bone losers.

CONCLUSIONS

HPA axis may contribute to postmenopausal bone health, but differences in cortisol secretion do not influence the differential rate of bone loss between slow and fast bone losers in the early postmenopausal period, at least in healthy women.

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.

Characteristics of age-related changes in bone compared between male and female reference Chinese populations in Hong Kong: a pQCT study

There have been few comprehensive studies on the age-related changes in bone mineral density (BMD) and bone structure in Chinese people. Using peripheral quantitative computed tomography (pQCT), we assessed volumetric BMD of both trabecular and cortical bone and their geometry at both radius and tibia in 620 Chinese men and 638 women, aged 20–98 years, in Hong Kong. Cortical BMD did not start declining until after the age of 50 years in women and the age of 60 years in men. In contrast, trabecular BMD declined with age starting from adulthood in both sexes, and the rates of decline accelerated after the age of 50 years only in women. The integral and trabecular bone area expanded with age in older men and women, primarily at the tibia. Cortical bone area decreased significantly in older women, particularly at the tibia, while it decreased only slightly with aging in men. The moment of inertia decreased with age at the radius in older men and women. At the tibia, age-related decline accelerated in older women, but not in older men. It was concluded that trabecularization of bone in response to declining BMD and mechanical loading may be maladaptive by reducing cortical bone area, if periosteal apposition cannot keep pace with it.

Shockwave exerts osteogenic effect on osteoporotic bone in an ovariectomized goat model

Our recent in vitro study showed that extracorporeal shock wave (ESW) stimulated calcium deposition in human periosteal cells. In this study, we hypothesized that the use of ESW could induce new bone formation in osteoporotic bone. Using our established osteoporotic goat model, the calcaneus, distal radius and femoral condyle of the left limb were treated with ESW once per month; the contralateral side served as the control. Bone mineral density (BMD), microarchitecture and dynamic histomorphometric index were evaluated after 9 months. Trabecular BMD of the calcaneus increased significantly by 2.90%. This finding was substantiated by micro-computed tomography findings showing that trabecular bone volume fraction and trabecular thickness of the treated calcaneus were enhanced compared with the contralateral control. However, significant difference could not be detected in the other two weight-bearing skeletal sites. Mineral apposition rates of all ESW-treated regions were also consistently higher than those of the control. These findings suggest that ESW treatment could enhance local BMD by inducing new bone formation, yet the effect was more apparent in non-weight-bearing sites.

Age-related decline in trabecular and cortical density: a 5-year peripheral quantitative computed tomography follow-up study of pre- and postmenopausal women

This 5-year prospective study assessed changes in trabecular and cortical volumetric bone density at the non-weight-bearing radius and weight-bearing tibia among clinically healthy pre- and postmenopausal women. Altogether 79 premenopausal (mean age +/- SD at baseline 33 +/- 2 years) and 108 postmenopausal (68 +/- 2 years) women participated in the baseline and follow-up measurements. Trabecular density (TrD) of the distal radius and tibia and cortical density (CoD) of the radial and tibial shafts were assessed by peripheral quantitative computed tomography (pQCT). Repeated measures analysis of variance was used to analyze differences of means and mean changes between the age groups. As expected, TrD and CoD values were greater among premenopausal than postmenopausal women. Changes in radial TrD were similar in both age groups: mean (95% confidence interval) TrD of the distal radius declined by 3.0 mg/cm(3) (-0.9 to 7.0) and 5.1 mg/cm(3) (1.8-8.5) in the younger and older age groups, respectively. The respective declines in TrD of the distal tibia were 4.1 mg/cm(3) (2.1-6.0) and 2.8 mg/cm(3) (1.2-4.3). Decline in CoD was greater in the older than younger age group at both the radial and tibial shafts (P < 0.001). The mean absolute declines in radial CoD were 33.3 mg/cm(3) (27.9-38.7) and 49.4 mg/cm(3) (44.9-53.9) in younger and older women, and the declines in tibial CoD were 16.5 mg/cm(3) (12.6-20.2) and 28.1 mg/cm(3) (25.0-31.2), respectively. In conclusion, volumetric TrD in the weight-bearing tibia and non-weight-bearing radius showed similar age-related declines among pre- and postmenopausal women, while the decline in CoD was greater among postmenopausal women.

High-Frequency Whole-Body Vibration Improves Balancing Ability in Elderly Women

OBJECTIVE

To investigate the efficacy of high-frequency whole-body vibration (WBV) on balancing ability in elderly women.

DESIGN

Randomized controlled trial. Subjects were randomized to either the WBV intervention or the no-treatment control group.

SETTING

Community-living elderly women.

PARTICIPANTS

Sixty-nine elderly women aged 60 or above without habitual exercise.

INTERVENTION

Side alternating WBV at 20Hz with 3 minutes a day and 3 days a week for 3 months in the WBV intervention group. Those in control group remained sedentary with normal daily life for the whole study period.

MAIN OUTCOME MEASURES

Limits of stability in terms of reaction time, movement velocity, directional control, endpoint excursion, maximum excursion, and the functional reach test were performed at baseline and endpoint.

RESULTS

Significant enhancement of stability was detected in movement velocity (P<.01), maximum point excursion (P<.01), in directional control (P<.05).

CONCLUSIONS

WBV was effective in improving the balancing ability in elderly women. This also provides evidence to support our user-friendly WBV treatment protocol of 3 minutes a day for the elderly to maintain their balancing ability and reduce risks of fall.

The effects of Tai Chi on bone mineral density in postmenopausal women: a systematic review

OBJECTIVE

To evaluate the evidence for Tai Chi as an intervention to reduce rate of bone loss in postmenopausal women.

DATA SOURCES

Literature search using Medline, Science Citation Index, Cochrane databases, China Biological Medicine Database, and additional manual reference searches of retrieved articles and personal libraries.

STUDY SELECTION

Randomized controlled trials (RCTs), prospective cohort studies, and cross-sectional studies that included Tai Chi as an intervention, and had at least 1 outcome related to measurement of bone mineral density (BMD).

DATA EXTRACTION

Authors critically reviewed studies, evaluated methodologic quality, and synthesized study results in a summary table.

DATA SYNTHESIS

Six controlled studies were identified by our search. There were 2 RCTs, 2 nonrandomized prospective parallel cohort studies, and 2 cross-sectional studies. The 2 RCTs and 1 of the prospective cohort studies suggested that Tai Chi-naive women who participated in Tai Chi training exhibited reduced rates of postmenopausal declines in BMD. Cross-sectional studies suggested that long-term Tai Chi practitioners had higher BMD than age-matched sedentary controls, and had slower rates of postmenopausal BMD decline. No adverse effects related to Tai Chi were reported in any trial.

CONCLUSIONS

Conclusions on the impact of Tai Chi on BMD are limited by the quantity and quality of research to date. This limited evidence suggests Tai Chi may be an effective, safe, and practical intervention for maintaining BMD in postmenopausal women. In combination with research that indicates Tai Chi can positively impact other risk factors associated with low BMD (eg, reduced fall frequency, increased musculoskeletal strength), further methodologically sound research is warranted to better evaluate the impact of Tai Chi practice on BMD and fracture risk in postmenopausal women.

Regional variations in the apparent and tissue-level mechanical parameters of vertebral trabecular bone with aging using micro-finite element analysis

The aim of this study was to obtain the apparent and tissue-level mechanical parameters of vertebral cancellous bones using micro-finite element analysis, and to identify the regional variations and their relative differences with respect to aging. Ninety trabecular specimens were obtained from six normal L4 vertebral bodies of six male cadavers in two age groups, three aged 62 years and three aged 69 years, and then were scanned using a high-resolution micro-Computed Tomography (micro-CT) system. The obtained micro-CT reconstruction models were then converted to micro-finite element models. Micro-finite element analyses were done to determine the apparent Young's moduli and tissue-level Von Mises stress distribution for each trabecular specimen on the longitudinal direction, and medial-lateral and anterior-posterior directions (transverse directions), respectively. Regional variations about the mechanical parameters at both apparent and tissue levels in different transverse layers and vertical columns within and between the two age groups were then analyzed. The results showed significant decreases in the apparent Young's moduli in each direction with aging, and those in the two transverse directions decreased more with aging compared with the longitudinal direction. Furthermore, there were no statistically significant differences between the mechanical parameters in the two transverse directions in both age groups. This study offered an insight into the distributions and variations of mechanical properties within a vertebral body. The mechanical parameters calculated from this study may help in a better understanding of regional fracture risks and the vertebral fracture mechanism in the prevention of osteoporotic fracture in elder individuals.

Alendronate increases BMD at appendicular and axial skeletons in patients with established osteoporosis

BACKGROUND

To identify high-risk patients and provide pharmacological treatment is one of the effective approaches in prevention of osteoporotic fractures. This study investigated the effect of 12-month Alendronate treatment on bone mineral density (BMD) and bone turnover biochemical markers in postmenopausal women with one or more non-traumatic fractures, i.e. patients with established osteoporosis.

METHODS

A total of 118 Hong Kong postmenopausal Chinese women aged 50 to 75 with low-energy fracture at distal radius (Colles' fracture) were recruited for BMD measurement at lumbar spine and non-dominant hip using Dual-Energy X-ray Absorptiometry (DXA). 47 women with BMD T-score below -2 SD at either side were identified as patients with established osteoporosis and then randomized into Alendronate group (n = 22) and placebo control group (n = 25) for BMD measurement at spine and hip using DXA and distal radius of the non-fracture side by peripheral quantitative computed tomography (pQCT), and bone turnover markers, including bone forming alkaline phosphatase (BALP) and bone resorbing urinary Deoxypyridinoline (DPD). All measurements were repeated at 6 and 12 months.

RESULTS

Alendronate treatment significantly increased BMD, more in weight-bearing skeletons (5.1% at spine and 2.5% at hip) than in non-weight bearing skeleton (0.9% at distal radius) after 12 months treatment. Spine T-score was significant improved in Alendronate group (p < 0.01) (from -2.2 to -1.9) but not in control placebo group. The Alendronate treatment effect was explained by significant suppression of bone turnover.

CONCLUSION

12 months Alendronate treatment was effective to increase BMD at both axial and appendicular skeletons in postmenopausal women with established osteoporosis.

Trabecular bone status in ultradistal tibia under habitual gait loading: a pQCT study in postmenopausal women

This study investigated regional volumetric trabecular bone mineral density (tBMD) and bone area at the ultradistal tibia in Chinese women using peripheral quantitative computed tomography. Fifty-six postmenopausal women aged 47-62 yr participated in BMD measurements at baseline and 22 of them were followed at both 1-yr and 3-yr follow-up scans. Regional baseline tBMD, rate of annual bone loss, and trabecular bone area were determined. Baseline measurements showed that the tBMD of both the posterior (252.9+/-63.4 mg/cm(3)) and medial (226.6+/-68.9 mg/cm(3)) regions was significantly higher than that of the anterior (126.3+/-61.9 mg/cm(3)) and lateral regions (149.8+/-50.6 mg/cm(3)), respectively (p<0.001). Both the 1-yr and 3-yr follow-up measurements showed that there was significant physiological annual tBMD loss on an average of 1.61%, at the four regions. Inter-slice regional tBMD and trabecular bone area measurements demonstrated a significant linear decrease from the distal to proximal aspects (p<0.001). Findings suggest that dynamic compressive loading during the heel strike and the body weight vector shifting toward the medial aspect during the stance phase in a normal gait might account for the regional tBMD differences. Increased tBMD and bone area toward the distal tibial endplate may adapt to withstand the axial impact loading. However, the low-impact weight-bearing nature of a normal gait may not be osteogenic to prevent regional bone loss. An exercise program specific to the women at risk should be contemplated.

Regional differences in trabecular BMD and micro-architecture of weight-bearing bone under habitual gait loading--a pQCT and microCT study in human cadavers

This study used both multi-slice pQCT and microCT to investigate regional changes in bone mineral density and structural parameters in the ultradistal tibia and in the mid-femoral neck under habitual gait loading. Twenty cadavers with 2 females and 18 males aged 70.8 +/- 8.5 were used in this study. Seventy-two cylindrical bone cores with 5 mm in diameter and 10 mm in length from the anterior/posterior and superior/inferior regions were obtained from ultradistal tibia and mid-femur neck, respectively, so that their differences in terms of volumetric trabecular bone mineral density (tBMD) as well as micro-architectural parameters could be studied. The results showed that the mean volumetric tBMD at both the organ (including the bone marrow spaces) and tissue levels (excluding the bone marrow spaces) were a 49.2% and 28.3%, respectively, lower in the anterior bone cores than in the posterior bone cores from the ultradistal tibia (P < 0.01). MicroCT measurements on BV/TV, BS/TV, Tb.N, Tb.Th, and DA were found to be on average of 33.5%, 23.6%, 9.1%, 18.0%, and 14.6%, respectively, lower in the anterior trabecular bone cores (P < 0.001), while Tb.Sp and SMI were 12.5% and 29.3%, respectively, higher in the anterior trabecular bone cores (P < 0.01). No significant difference in micro-architectural parameters was found in the trabecular bone cores obtained from mid-femoral neck, except that the mean DA of the inferior bone cores was significantly higher by 30.1% than that of the superior bone cores (P = 0.01). A statistically significant linear relationship with the correlation coefficient, ranging from 0.37 to 0.94 and -0.62 to -0.85, respectively, was shown between the tBMD at the organ level and all of the micro-architectural parameters (P < 0.05). We suggest that dynamic loading changes during the striking of the heel in normal gait, as well as the peaks of the hip joint reaction force occur during the heel strike and before toe off positions in the lifetime of the subject may account for such regional differences in BMD and micro-architecture. The findings from the correlation study also suggest that, apart from BMD, the micro-architecture may exhibit adaptation in response to such excessive loading.

Low BMD is a risk factor for low-energy Colles' fractures in women before and after menopause

Until now, it was unclear if low volumetric bone mineral density at the distal radius was also a risk factor for Colles' fracture, especially in patients with low-energy trauma. In our study, we used peripheral quantitative computed tomography to measure volumetric bone mineral density of a nonfractured distal radius and dual-energy x ray absorptiometry to measure areal bone mineral density at the spine and hip in patients with Colles' fractures, including 45 women who were premenopausal (age range, 40-50 years) and 39 women who were postmenopausal (age range, 51-65 years). In each group, the patients were subdivided into low-energy and high-energy fracture groups. Ninety-five age-matched healthy women who were premenopausal and 90 age-matched healthy women who were postmenopausal without fracture history served as controls. The results showed that patients with low-energy fractures had a lower bone mineral density at all measurement sites, compared with either patients with high-energy fractures or control subjects. More patients were found with a bone mineral density less than -2.5 standard deviations (Z-score) in the premenopausal group (12.5% measured by dual-energy x ray absorptiometry and 41.2% measured by peripheral quantitative computed tomography) than in the postmenopausal group (6.0% measured by dual-energy x ray absorptiometry and 4.8% measured by peripheral quantitative computed tomography). These results suggest that low bone mineral density, particularly measured using peripheral quantitative computed tomography at the distal radius of women who were premenopausal, was an important risk factor for low-energy Colles' fractures.

LEVEL OF EVIDENCE

Prognostic study, Level I-1 (prospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Regional differences in cortical bone mineral density in the weight-bearing long bone shaft--a pQCT study

This study used a multislice peripheral quantitative computed tomography (pQCT) to measure volumetric BMD (vBMD) and cortical thickness for investigating regional adaptation in lower tibial shaft in 72 healthy postmenopausal women aged 47-60. Tomographic slices were analysed on four distinct cortical regions: the anterior, posterior, medial and lateral cortical wall. One-way analysis of variance (ANOVA) test was used to compare the vBMD in the four regions. The results showed that the posterior cortex had the highest vBMD (1923 +/- 135.3 mg/cm(3)), significantly (P < 0.001) higher than the anterior cortex (1805 +/- 110.6 mg/cm(3)), medial cortex (1863 +/- 103.6 mg/cm(3)) and lateral cortex (1815 +/- 111.6 mg/cm(3)); whereas there was no significant difference (P > 0.05) between the medial and lateral cortices located near the neutral plane of bending. The anterior cortex had the greatest thickness (2.56 +/- 0.47 mm), significantly (P < 0.001) greater than that of the posterior cortex (2.11 +/- 0.27 mm), medial cortex (2.20 +/- 0.39 mm) and lateral cortex (2.03 +/- 0.29 mm). The vBMD of the posterior cortex was a significant 6.5% higher than that of the anterior cortex (P < 0.001); whereas the anterior cortical thickness was a significant 21.3% greater than that of the posterior cortex (P < 0.001). There was no linear relationship found between cortical vBMD and cortical thickness measured at the four cortical regions (r = 0.086, P > 0.05). In conclusion, the regional differences, with higher vBMD found in posterior cortex, might be a result of mechanical adaptation, which caused the posterior cortex to sustain higher compressive loading than the anterior tensile cortex during the landing phase in the gait cycles of individuals. Nevertheless, regional geometric adaptation in anterior cortical thickness might be adapted to accommodate for the reduced vBMD and to reduce the bending stress in this region.

Lack of efficacy of low-intensity pulsed ultrasound on prevention of postmenopausal bone loss evaluated at the distal radius in older Chinese women

A within-subject, randomized, and prospective intervention trial was done to evaluate the potential effect of low-intensity pulsed ultrasound on prevention of postmenopausal bone loss. Twenty healthy postmenopausal women between the ages of 51-81 years met the inclusion criteria. The treatment hand was randomly selected, and the contralateral site served as a control. Integral and trabecular bone mineral density were measured using highly precise multilayer peripheral quantitative computed tomography at the bilateral distal radius at baseline, 3 months after daily low-intensity pulsed ultrasound treatment, and 3 months after discontinuing treatment. Results showed that the rate of bone change (trabecular bone mineral density and integral bone mineral density) did not significantly differ between the site treated with low-intensity pulsed ultrasound and the contralateral control at either followup. Also, during the followup, bone mineral density did not change significantly in the contralateral control site. This was the first prospective and randomized study to show that low-intensity pulsed ultrasound at the current regime did not have significant effects on intact bone for prevention of postmenopausal bone loss in the distal radii of older Chinese women.

A randomized, prospective study of the effects of Tai Chi Chun exercise on bone mineral density in postmenopausal women 11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated

OBJECTIVE

To evaluate the potential benefits of programmed Tai Chi Chun (TCC) exercise on the weight-bearing bones of early postmenopausal women.

DESIGN

Age-matched and randomized prospective intervention.

SETTING

University medical school.

PARTICIPANTS

One hundred thirty-two healthy postmenopausal women (mean age, 54.0+/-3.5y) within 10 years of menopause onset were recruited and randomized into the TCC exercise group (n=67) or the sedentary control group (n=65).

INTERVENTION

Supervised TCC exercise was performed by the TCC group for 45 minutes a day, 5 days a week, for 12 months; control subjects retained a sedentary life style. Main outcome measures Bone mineral density (BMD) was measured in the lumbar spine and proximal femur by using dual-energy x-ray absorptiometry and in the distal tibia by using multislice peripheral quantitative computed tomography (pQCT). All BMD measurements were repeated after 12 months in both groups. Fracture rate was also documented.

RESULTS

Baseline measurements showed homogeneity in age, anthropometric variables, and menstruation status between the TCC and control groups. Exactly 81.6% of the subjects in the TCC group and 83.1% of subjects in the control group completed the 12-month follow-up study. BMD measurements revealed a general bone loss in both TCC and sedentary control subjects at all measured skeletal sites, but with a reportedly slower rate in the TCC group. A significant 2.6- to 3.6-fold retardation of bone loss (P<.01) was found in both trabecular and cortical compartments of the distal tibia in the TCC group as compared with the controls, as measured by pQCT. A total of 4 fracture cases were documented during follow-up, including 3 subjects in the control group and 1 in the TCC group.

CONCLUSIONS

This is the first prospective and randomized study to show that a programmed TCC exercise intervention is beneficial for retarding bone loss in weight-bearing bones in early postmenopausal women. Long-term follow-up is needed to substantiate the role of TCC exercise in the prevention of osteoporosis and its related fracture.

Genetically linked site-specificity of disuse osteoporosis

The genetic influence on bone loss in response to mechanical unloading was investigated within diaphyseal and distal femoral regions in three genetically distinct strains of mice. One mouse strain failed to lose bone after removal of function, whereas osteopenia was evident in multiple regions of the remaining two strains but in different areas of the bone.

INTRODUCTION

It is well recognized that susceptibility to osteoporosis is, in large measure, determined by the genome, but whether this influence is systemic or site-specific is not yet known. Here, the extent to which genetic variations influence regional bone loss caused by disuse was studied in the femora of adult female mice from three inbred strains.

MATERIALS AND METHODS

Adult C57BL/6J (B6), C3H/HeJ (C3H), and BALB/cByJ (BALB) mice were subjected to 15-21 days of disuse, achieved by hindlimb suspension, and six distinct anatomical regions of the femur were analyzed by high-resolution microCT.

RESULTS AND CONCLUSIONS

In B6 mice, the amount of disuse stimulated bone loss was relatively uniform across all regions, with 20% loss of trabecular bone and 10% loss of cortical bone. The degree of bone loss in BALB mice varied greatly, ranging from 59% in the metaphysis to 3% in the proximal diaphysis. In this strain, the nonuniformity of bone loss was directly related to the nonuniform distribution of baseline bone morphology (r2 = 0.94). In direct contrast with BALB and B6, disuse failed to produce significant losses of bone in any of the analyzed regions of the C3H mice. Instead, these animals displayed a unique compensatory mechanism to disuse, where the large loss of calcified tissue from the endocortical surface (-24%) was compensated for by an expansion of the periosteal envelope (10%). These data indicate a strong, yet complex, genetic dependence of the site-specific regulation of bone remodeling in response to a powerful catabolic signal. Consequently, the skeletal region of interest and the genetic make-up of the individual may have to be considered interdependently when considering the pathogenesis of osteoporosis or the efficacy of an intervention to prevent or recover bone loss.

Characteristics of long bone DXA reference data in Hong Kong Chinese

With the increasing number of geriatric long bone fractures, the establishment of long bone reference BMD data is desirable for the accurate diagnosis of osteoporosis, study of fracture mechanics, implant design, and indications for augmentation of fracture fixation with biomaterials. We report the normal reference bone mineral density (BMD) and bone mineral content (BMC) at three femoral sites (proximal, diaphyseal, and distal) in 106 male and 93 female Hong Kong Chinese aged 12 to 80, measured with dual-energy X-ray absorptiometry (DXA). The length and width of the femur were also measured. The results suggest that males reached peak bone mass earlier than females and the value was also higher in all measured sites. After reaching the peak bone mass, bones lost BMD faster in females. The age-related annual bone loss (in BMD) calculated with a regression model in female subjects were, on average, 3.3, 4.0, and 3.0 times higher than those in males at the diaphyseal, proximal, and distal regions, respectively. The decrease in BMD and BMC occurred slightly earlier in the proximal and distal regions than the diaphysis in both sexes. The male femur was significantly longer than that of the female in all age groups after 20 yr of age and remained unchanged with advancing age. The femoral width in females showed an increasing trend from adolescence. Our study provides reference data for the changes in diaphyseal BMC and BMD associated with aging. The age-related changes in the femoral diameter in females might attenuate the negative impact on fracture risk as a result of decreasing BMD with age.