Relationship between changes in bone mineral density and vertebral fracture risk associated with risedronate: greater increases in bone mineral density do not relate to greater decreases in fracture risk

Calcitonin: a drug of the past or for the future? Physiologic inhibition of bone resorption while sustaining osteoclast numbers improves bone quality

Postmenopausal osteoporosis results from a continuous imbalance between bone resorption and bone formation, favoring bone resorption. An increasing number of treatments for osteoporosis are in development and on the market. A range of differences and similarities are found between these treatment options, and these need to be carefully evaluated before the initiation of treatment. This article summarizes data from in vitro and animal studies, as well as clinical trials, on the effect of calcitonin on bone turnover. Calcitonin was found to exert its antiresorptive effects via directly reducing osteoclastic resorption, and thus leads to an increase in bone mineral density and bone strength. Furthermore, calcitonin appears to mainly target the most active osteoclasts, and in contrast to most other antiresorptive agents it does not reduce the number of osteoclasts. Finally, in humans, while attenuating resorption, calcitonin treatment does not interfere markedly with bone formation, in contrast to other currently available antiresorptive agents. Thus, we speculate that calcitonin treatment will lead to a continuously positive bone balance in contrast with other antiresorptive agents currently on the market and thereby, in a physiologic manner, result in improved bone quality. Calcitonin is currently only available in injectable and nasal formulations. An oral formulation may, however, improve patient acceptance and compliance. Currently, several different routes are being pursued to identify an optimal oral formulation, of which the technology based on 5-CNAC is the most advanced. There are promising clinical data available for this formulation from both osteoarthritis and osteoporosis clinical trials, although the antifracture efficacy is not yet known.

DXA scanning in clinical practice

Dual-energy X-ray absorptiometry (DXA) is recognized as the reference method to measure bone mineral density (BMD) with acceptable accuracy errors and good precision and reproducibility. The World Health Organization (WHO) has established DXA as the best densitometric technique for assessing BMD in postmenopausal women and based the definitions of osteopenia and osteoporosis on its results. DXA allows accurate diagnosis of osteoporosis, estimation of fracture risk and monitoring of patients undergoing treatment. However, when DXA studies are performed incorrectly, it can lead to major mistakes in diagnosis and therapy. This article reviews the fundamentals of positioning, scan analysis and interpretation of DXA in clinical practice.

Effectiveness of risedronate in osteoporotic postmenopausal women with inflammatory bowel disease: a prospective, parallel, open-label, two-year extension study

OBJECTIVE

To evaluate long-term efficacy of risedronate in osteoporotic postmenopausal patients with inflammatory bowel disease (IBD).

DESIGN

A prospective, parallel, open-label, 2-year extension study of a randomized, double-blind, 1-year clinical trial. Eighty-one osteoporotic postmenopausal women with IBD were treated with risedronate (n = 40) or placebo (n = 41). Bone mineral density (BMD), biochemical bone turnover markers, and vertebral and nonvertebral fractures were assessed throughout the study. Data were analyzed using the intent-to-treat principle.

RESULTS

Significant (P < 0.05) differences were observed between risedronate and placebo groups at 1-, 2-, and 3-year follow-up visits in bone turnover markers and in lumbar spine, trochanter, and femoral neck BMD. In participants treated with risedronate, the percentage of changes from baseline in bone turnover markers and in lumbar spine, trochanter, and femoral neck BMD were significantly (P < 0.05) higher at 2- and 3-year follow-up in comparison with baseline and 1-year follow-up, with a significant (P < 0.05) difference between the 2- and 3-year follow-up visits. At the end of the study, the cumulative risk of vertebral and nonvertebral fractures was significantly (P < 0.05) lower in the risedronate group than in the placebo group. The relative risk for new vertebral fractures was 0.456 (95% CI: 0.134-1.559, P = 0.211) and 0.296 (95% CI: 0.121-0.721, P = 0.007) and was 0.209 (95% CI: 0.023-1.867, P = 0.161) and 0.137 (95% CI: 0.030-0.620, P = 0.010), respectively, for new nonvertebral fractures after 2 and 3 years of risedronate treatment.

CONCLUSIONS

In postmenopausal osteoporotic women with IBD, long-term treatment with risedronate is effective in increasing BMD and reducing vertebral and nonvertebral fracture risk.

A new quality of bone ultrasound research

Quantitative ultrasound (QUS) methods have strong power to predict osteoporotic fractures, but they are also very relevant for the assessment of bone quality. A representative sample of recent studies addressing these topics can be found in this special issue. Further pursuit of these methods will establish micro-QUS imaging methods as tools for measuring specific aspects of bone quality. Once this is achieved, we will be able to link such data to the clinical QUS methods used in vivo to determine which aspects of bone quality cause QUS to be a predictor of fracture risk that is independent of bone mineral density (BMD). Potentially this could lead to the development of a new generation of QUS devices for improved and expanded clinical assessment. Good quality of basic science work will thus lead to good quality of clinical patient examinations on the basis of a more detailed assessment of bone quality.

Mechanisms of action of bisphosphonates: similarities and differences and their potential influence on clinical efficacy

Bisphosphonates (BPs) are well established as the leading drugs for the treatment of osteoporosis. There is new knowledge about how they work. The differences that exist among individual BPs in terms of mineral binding and biochemical actions may explain differences in their clinical behavior and effectiveness.

INTRODUCTION

The classical pharmacological effects of bisphosphonates (BPs) appear to be the result of two key properties: their affinity for bone mineral and their inhibitory effects on osteoclasts.

DISCUSSION

There is new information about both properties. Mineral binding affinities differ among the clinically used BPs and may influence their differential distribution within bone, their biological potency, and their duration of action. The antiresorptive effects of the nitrogen-containing BPs (including alendronate, risedronate, ibandronate, and zoledronate) appear to result from their inhibition of the enzyme farnesyl pyrophosphate synthase (FPPS) in osteoclasts. FPPS is a key enzyme in the mevalonate pathway, which generates isoprenoid lipids utilized for the post-translational modification of small GTP-binding proteins that are essential for osteoclast function. Effects on other cellular targets, such as osteocytes, may also be important. BPs share several common properties as a drug class. However, as with other families of drugs, there are obvious chemical, biochemical, and pharmacological differences among the individual BPs. Each BP has a unique profile that may help to explain potential clinical differences among them, in terms of their speed and duration of action, and effects on fracture reduction.

Effects of bazedoxifene on BMD and bone turnover in postmenopausal women: 2-yr results of a randomized, double-blind, placebo-, and active-controlled study

Osteoporosis is an increasingly common health concern in postmenopausal women. In a 2-yr phase III study, bazedoxifene prevented bone loss, reduced bone turnover, and was well tolerated in early postmenopausal women with normal or low BMD.

INTRODUCTION

Bazedoxifene is a novel selective estrogen receptor modulator that has increased BMD and bone strength in experimental models, without stimulating breast or uterus. This 24-mo, randomized, double-blind study assessed the efficacy and safety of three doses of bazedoxifene compared with placebo and raloxifene in the prevention of postmenopausal osteoporosis.

MATERIALS AND METHODS

Healthy postmenopausal women with a BMD T-score at the lumbar spine or femoral neck between -1.0 and -2.5 or clinical risk factors for osteoporosis were randomly assigned to one of five groups: bazedoxifene 10, 20, or 40 mg/d, placebo, or raloxifene 60 mg/d. All women received elemental calcium. Efficacy outcomes included changes from baseline through 24 mo in BMD of the lumbar spine, hip, femoral neck, and femoral trochanter and biomarkers of bone metabolism.

RESULTS

The intent-to-treat population included 1434 women (mean age, 58 yr; mean time from last menstrual period, 11 yr). All doses of bazedoxifene and raloxifene prevented bone loss, whereas in the placebo group, there was significant loss of BMD at all skeletal sites. Mean differences in percent change in lumbar spine BMD from baseline to 24 mo relative to placebo were 1.08 +/- 0.28%, 1.41 +/- 0.28%, 1.49 +/- 0.28%, and 1.49 +/- 0.28% for 10, 20, and 40 mg bazedoxifene and 60 mg raloxifene, respectively (p < 0.001 for all comparisons). Comparable BMD responses were observed at other body sites. Significant and comparable decreases in serum osteocalcin and C-telopeptide levels from baseline and relative to placebo with active treatment were observed as early as 3 mo and were sustained through study conclusion (p < 0.001). Overall incidences of adverse events, serious adverse events, and discontinuations caused by adverse events were similar between groups. The most common adverse events included headache, infection, arthralgia, pain, hot flush, and back pain.

CONCLUSIONS

Treatment with bazedoxifene prevented bone loss and reduced bone turnover equally as well as raloxifene and was generally well tolerated in postmenopausal women with normal/low BMD.

Bone turnover and bone collagen maturation in osteoporosis: effects of antiresorptive therapies

Bone collagen maturation may be important for anti-fracture efficacy as the reduction in risk is only partly explained by a concomitant increase in BMD during anti-resorptive therapy. Different treatments caused diverse profiles in bone collagen degradation products, which may have implications for bone quality.

INTRODUCTION

The aim of the present study was to evaluate the effect of different anti-resorptive treatments on bone collagen maturation measured as the ratio between the degradation products of newly synthesized and mature isomerized C-telopeptides of type I collagen.

METHODS

Participants were from cohorts of healthy postmenopausal women participating in double blind, placebo-controlled 2-year studies of alendronate, ibandronate, intranasal hormone replacement therapy (HRT), oral HRT, transdermal HRT, or raloxifene (n = 427). The non-isomerized alphaalphaCTX and isomerized betabetaCTX were measured in urine samples obtained at baseline, and after 6, 12, and 24 months of therapy.

RESULTS

Bone collagen maturation measured as the ratio between alphaalphaCTX and betabetaCTX showed that bisphosphonate treatment induced a collagen profile consistent with an older matrix with a 52% (alendronate) and 38% (ibandronate) reduction in the ratio between the two CTX isoforms vs. 3% and 15% with HRT or raloxifene, respectively.

CONCLUSIONS

Anti-resorptive treatments had different effects on the endogenous profile of bone collagen maturation. Whether that effect on bone collagen has an impact on bone strength independent on the treatment-dependent effect on BMD should be investigated.

Bisphosphonates alter trabecular bone collagen cross-linking and isomerization in beagle dog vertebra

Changes in organic matrix may contribute to the anti-fracture efficacy of anti-remodeling agents. Following one year of treatment in beagle dogs, bisphosphonates alter the organic matrix of vertebral trabecular bone, while raloxifene had no effect. These results show that pharmacological suppression of turnover alters the organic matrix component of bone.

INTRODUCTION

The collagen matrix contributes significantly to a bone's fracture resistance yet the effects of anti-remodeling agents on collagen properties are unclear. The goal of this study was to assess changes in collagen cross-linking and isomerization following anti-remodeling treatment.

METHODS

Skeletally mature female beagles were treated for one year with oral doses of vehicle (VEH), risedronate (RIS; 3 doses), alendronate (ALN; 3 doses), or raloxifene (RAL; 2 doses). The middle dose of RIS and ALN and the lower dose of RAL approximate doses used for treatment of post menopausal osteoporosis. Vertebral trabecular bone matrix was assessed for collagen isomerization (ratio of alpha/beta C-telopeptide [CTX]), enzymatic (pyridinoline [PYD] and deoxypyridinoline [DPD]), and non-enzymatic (pentosidine [PEN]) cross-links.

RESULTS

All doses of both RIS and ALN increased PEN (+34-58%) and the ratio of PYD/DPD (+14-26%), and decreased the ratio of alpha/beta CTX (-29-56%) compared to VEH. RAL did not alter any collagen parameters. Bone turnover rate was significantly correlated to PEN (R = -0.664), alpha/beta CTX (R = 0.586), and PYD/DPD (R = -0.470).

CONCLUSIONS

Bisphosphonate treatment significantly alters properties of bone collagen suggesting a contribution of the organic matrix to the anti-fracture efficacy of this drug class.

Fracture risk remains reduced one year after discontinuation of risedronate

One year after discontinuation of three year's treatment with risedronate, BMD decreased at the lumbar spine and femoral neck and bone turnover markers returned to control group levels. Despite these changes, the risk of new morphometric vertebral fractures remained lower in previous risedronate patients compared with previous control patients.

INTRODUCTION

Differences in bisphosphonate pharmacology and pharmacokinetics could influence persistence or resolution of the effects once treatment is stopped. We investigated changes in intermediate markers--bone mineral density (BMD) and bone turnover markers (BTM)--and fracture risk after discontinuation of treatment with risedronate.

METHODS

Patients who received risedronate 5 mg daily (N = 398) or placebo (N = 361) during the VERT-NA study stopped therapy per protocol after 3 years but continued taking vitamin D (if levels at study entry were low) and calcium and were reassessed one year later.

RESULTS

In the year off treatment, spine BMD decreased significantly, but remained higher than baseline (p < or = 0.001) and placebo (p < 0.001), with similar findings at the femoral neck and trochanter. Urinary NTX and bone-specific alkaline phosphatase, which decreased significantly with treatment, were not significantly different from placebo after 1 year off treatment. Despite the changes in intermediate markers, the incidence of new morphometric vertebral fractures was 46% lower in the former risedronate group compared with the former placebo group (RR 0.54 [95% CI, 0.34, 0.86, p = 0.009]).

CONCLUSIONS

Despite the apparent resolution of effect on BMD and BTM, the risk reduction of new vertebral fractures remained in the year after treatment with risedronate was stopped.

Cost effectiveness of ibandronate for the prevention of fractures in inflammatory bowel disease-related osteoporosis: cost-utility analysis using a Markov model

BACKGROUND

Osteoporosis is a frequent complication in patients with inflammatory bowel disease. Recent studies have shown bisphosphonates to considerably reduce fracture risk in patients with osteoporosis, and preventing fractures with bisphosphonates has been reported to be cost effective in older populations. However, no studies of the cost effectiveness of these agents in preventing fractures in patients with inflammatory bowel disease are available.

OBJECTIVE

To investigate the cost effectiveness of the bisphosphonate ibandronate combined with calcium/colecalciferol ('ibandronate') in patients with osteopenia or osteoporosis due to inflammatory bowel disease in Germany. Treatment strategies used for comparison were sodium fluoride combined with calcium/colecalciferol ('fluoride') and calcium/colecalciferol ('calcium') alone.

STUDY DESIGN AND METHODS

A cost-utility analysis was conducted using data from a randomized controlled trial (RCT). Changes in bone mineral density (BMD) were adjusted and predicted for a standardized population receiving each respective treatment. A Markov model was developed, with probabilities of transition to fracture states consisting of BMD-dependent and -independent components. The BMD-dependent component was assessed using predicted change in BMD from the RCT. The independent component captured differences in bone quality and micro-architecture resulting from prevalent fractures or treatment with anti-resorptive drugs. The analysis was conducted for a population with a mean age of the RCT patients (women aged 36 years, men aged 38 years) with osteopenia (T-score about -2.0 at baseline), a population of the same age with osteoporosis (T-score of -3.0 at baseline) and for an older population (both sexes aged 65 years) with osteoporosis (T-score of -3.0). Outcomes were measured as costs per QALY gained from a societal perspective. The treatment duration in the RCT was 42 months. A 5-year period was assumed to follow, during which the treatment effects linearly declined to 0. The simulation time was 10 years. Prices for medication and treatment were presented as year 2004 values; costs and effects were discounted at 5%. To test the robustness of the results, univariate and probabilistic sensitivity analyses (Monte Carlo simulation) were conducted.

RESULTS

The calcium strategy dominated the fluoride strategy. When the ibandronate strategy was compared with the calcium strategy, the base-case cost-effectiveness ratios (costs per QALY gained) were between euro 407 375 for an older female population with osteoporosis and euro 6 516 345 for a younger female population with osteopenia. Univariate sensitivity analyses resulted in variations between 4% of base-case results and dominance of calcium. In Monte Carlo simulations, conducted for the various populations, the probability of an ICER of ibandronate below euro 50 000 per QALY was never greater than 20.2%.

CONCLUSION

The ibandronate strategy is unlikely to be considered cost effective by decision makers in men or women with characteristics of those in the target population of the RCT, or in older populations with osteoporosis.

Cost effectiveness of screen-and-treat strategies for low bone mineral density: how do we screen, who do we screen and who do we treat?

Bone densitometry is currently widely recommended for, and considered central to, identifying post-menopausal women and older men at high risk of fracture and establishing an indication for pharmacological fracture-prevention therapy. The purpose of this article is to comprehensively review cost-effectiveness modelling studies published to date of bone mass measurement technologies (primarily dual energy x-ray absorptiometry [DXA]) designed to identify those individuals at sufficiently high risk of fracture to warrant pharmacological fracture-prevention therapy.Based on older paradigms of the pharmacological treatment of those with a bone density value below a specific threshold, bone densitometry appears to be cost effective for post-menopausal women aged > or =65 years, regardless of the presence or absence of other clinical risk factors. For younger post-menopausal women, bone densitometry is likely to be cost effective only for those with specific clinical risk factors, such as prior fracture or low bodyweight. For older men, bone densitometry may be cost effective for those who have had a prior fracture and/or are aged > or =80 years, but the subset of men for whom bone densitometry is likely to be cost effective may vary from country to country depending on societal willingness to pay for health benefits, fracture rates in the population and the costs of bone densitometry and drug treatment. The cost effectiveness of other technologies such as heel ultrasound, peripheral DXA and quantitative CT remains uncertain.However, in the context of the new WHO paradigm of directing treatment based on absolute fracture risk rather than bone density, a new generation of cost-effectiveness modelling studies will be required to define the most cost-effective way bone densitometry can be used to identify those who are likely to benefit sufficiently from pharmacological fracture-prevention therapies.

Regional variation in vertebral bone morphology and its contribution to vertebral fracture strength

Vertebral fractures may result in pain, loss of height, spinal instability, kyphotic deformity and ultimately increased morbidity. Fracture risk can be estimated by vertebral bone mineral density (BMD). However, vertebral fractures may be better defined by more selective methods that account for micro-architecture. Our aim was to quantify regional variations in bone architecture parameters (BAPs) and to assess the degree with which regional variations in BAPs affect vertebral fracture strength. The influence of disc health and endplate thickness on fracture strength was also determined. The soft tissue and posterior elements of 20 human functional spine units (FSU) were removed (T9 to L5, mean 74.45+/-4.25 years). After micro-CT scanning of the entire FSU, the strength of the specimens was determined using a materials testing system. Specimens were loaded in compression to failure. BAPs were assessed for 10 regions of the vertebral cancellous bone. Disc health (glycosaminoglycan content of the nucleus pulposus) was determined using the degree of binding with Alcian Blue. Vertebrae were not morphologically homogeneous. Posterior regions of the vertebrae had greater bone volume, more connections, reduced trabecular separation and more plate-like isotropic structures than their corresponding anterior regions. Significant heterogeneity also exists between posterior superior and inferior regions (BV/TV: posterior superior 12.6+/-2.8%, inferior 14.6+/-3%; anterior superior 10.5+/-2.2%, inferior 10.7+/-2.4%). Of the two endplates that abutted a common disc, the cranial inferior endplate was thicker (0.44+/-0.15 mm) than the caudal superior endplate (0.37+/-0.13 mm). Our study found good correlations between BV/TV, connective density and yield strength. Fracture risk prediction, using BV/TV multiplied by the cross sectional area of the endplate, can be improved through regional analysis of the underlying cancellous bone of the endplate of interest (R(2) 0.78) rather than analysis of the entire vertebra (R(2) 0.65) or BMD (R(2) 0.47). Degenerated discs lack a defined nucleus. A negative linear relationship between disc health and vertebral strength (R(2) 0.70) was observed, likely due to a shift in loading from the weaker anterior vertebral region to the stronger posterior region and cortical shell. Our results show the importance of considering regional variations in cancellous BAPs and disc health when assessing fracture risk.

Bisphosphonates

Osteoporosis is the result of bone loss due to an imbalance in bone turnover such that bone resorption exceeds bone formation. Bisphosphonates are potent inhibitors of osteoclast activity that reduce bone turnover and re-establish the balance between bone resorption and formation. In clinical studies, several bisphosphonates prevent bone loss, preserve bone structure, improve bone strength and, in patients with osteoporosis, substantially reduce fracture risk. They are effective in multiple clinical settings including postmenopausal osteoporosis, low bone mass in men and drug-induced bone loss. Intermittent oral dosing and intravenous administration are more convenient than the original daily dosing regimen. These drugs are generally well tolerated and have an excellent safety profile in that serious side effects are uncommon. Potent bisphosphonates are generally the preferred treatment option for most patients with or at risk for osteoporosis.

Increases in BMD correlate with improvements in bone microarchitecture with teriparatide treatment in postmenopausal women with osteoporosis

Increases in BMD are correlated with improvements in 2D and 3D trabecular microarchitecture indices with teriparatide treatment. Therefore, improvements in trabecular bone microarchitecture may be one of the mechanisms to explain how BMD increases improve bone strength during teriparatide treatment.

INTRODUCTION

Bone strength is determined by BMD and other elements of bone quality, including bone microarchitecture. Teriparatide treatment increases BMD and improves both cortical and trabecular bone microarchitecture. Increases in lumbar spine (LS) BMD account for approximately 30-41% of the vertebral fracture risk reduction with teriparatide treatment. The relationship between increases in BMD and improvements in cortical and trabecular microarchitecture has not yet been studied.

MATERIALS AND METHODS

The relationship between increases in BMD and improvements in cortical and trabecular microarchitecture after teriparatide treatment was assessed using data from a subset of patients who had areal BMD measurements and structural parameters from transiliac bone biopsies in the Fracture Prevention Trial. 2D histomorphometric and 3D microCT parameters were measured at baseline and 12 (n = 21) or 22 (n = 36) mo. LS BMD was assessed at baseline and 12 and 18 mo, and femoral neck (FN) BMD was measured at baseline and 12 mo. Pearson correlation was performed to assess the relationship between actual changes in BMD and actual changes in microarchitectural parameters.

RESULTS

Changes in LS BMD at 12 mo were significantly correlated with improvements in trabecular bone structure at 22 mo: 2D bone volume (r = 0.45, p = 0.02), 2D mean wall thickness (r = 0.41, p = 0.03), 3D bone volume (r = 0.48, p = 0.006), 3D trabecular thickness (r = 0.44, p = 0.01), 3D trabecular separation (r = -0.37, p = 0.04), 3D structural model index (r = -0.54, p = 0.001), and 3D connectivity density (r = 0.41, p = 0.02). Changes in LS BMD at 18 mo had similar correlations with improvements in bone structure at 22 mo. Changes in FN BMD at 12 mo were significantly correlated with changes in 2D mean wall thickness (r = 0.56, p = 0.002), 3D bone volume (r = 0.51, p = 0.004), 3D trabecular thickness (r = 0.44, p = 0.01), 3D trabecular separation (r = -0.46, p = 0.01), and 3D structural model index (r = -0.55, p = 0.001).

CONCLUSIONS

Increases in BMD are correlated with improvements in trabecular microarchitecture in iliac crest of patients with teriparatide treatment. Therefore, improvements in trabecular bone microarchitecture may be one of the mechanisms to explain how BMD increases improve bone strength during teriparatide treatment.

Relationship between bone mineral density changes and fracture risk reduction in patients treated with strontium ranelate

OBJECTIVE

Our objective was to analyze the relationship between bone mineral density (BMD) changes and fracture incidence during 3-yr treatment with strontium ranelate.

PATIENTS

Women from the strontium ranelate arm of the Spinal Osteoporosis Therapeutic Intervention study and the TReatment Of Peripheral OSteoporosis study were evaluated.

OUTCOME MEASURES

The outcome measures included BMD at the lumbar spine, femoral neck, and total proximal femur assessed at baseline and after a follow-up of 1 and 3 yr; semiquantitative visual assessment of vertebral fractures; and nonvertebral fractures based on written documentation.

RESULTS

After 3 yr of strontium ranelate treatment, each percentage point increase in femoral neck and total proximal femur BMD was associated with a 3% (95% adjusted confidence interval, 1-5%) and 2% (1-4%) reduction in risk of a new vertebral fracture, respectively. The 3-yr changes in femoral neck and total proximal femur BMD explained 76% and 74%, respectively, of the reduction in vertebral fractures observed during the treatment. Three-year changes in spine BMD were not statistically associated with the incidence of new vertebral fracture (P = 0.10). No significant associations were found between 3-yr changes in BMD and incidence of new nonvertebral fractures, but a trend was found for femoral neck BMD (P = 0.09) and for total proximal femur BMD (P = 0.07). An increase in femoral neck BMD after 1 yr was significantly associated with the reduction in incidence of new vertebral fractures observed after 3 yr (P = 0.04).

CONCLUSION

During 3-yr strontium ranelate treatment, an increase in femoral neck BMD was associated with a proportional reduction in vertebral fracture incidence.

Evidence that treatment with risedronate in women with postmenopausal osteoporosis affects bone mineralization and bone volume

Risedronate is used in osteoporosis treatment. Postmenopausal women enrolled in the Vertebral Efficacy with Risedronate Therapy trial received either risedronate (5 mg/day) or placebo for 3 years. Subjects received calcium and vitamin D supplementation if deficient at baseline. Lumbar spine bone mineral density (BMD) was measured at baseline and at 3 years. Quantitative back-scattered electron imaging (qBEI) was performed on paired iliac crest biopsies (risedronate, n = 18; placebo, n = 13) before and after treatment, and the mineral volume fraction in the trabecular bone was calculated. Combining dual-energy X-ray absorptiometric values with the mineral volume fraction for the same patients allowed us to calculate the relative change in trabecular bone volume with treatment. This showed that the effect on BMD was likely to be due partly to changes in matrix mineralization and partly due to changes in bone volume. After treatment, trabecular bone volume in the lumbar spine tended to increase in the risedronate group (+2.4%, nonsignificant) but there was a significant decrease (-3.7%, P < 0.05) in the placebo group. Calcium supplementation with adequate levels of vitamin D led to an approximately 3.3% increase in mineral content in the bone material independently of risedronate treatment. This increase was larger in patients with lower matrix mineralization at baseline and likely resulted from correction of calcium/vitamin D deficiency as well as from reduced bone remodeling. Combining BMD and bone mineralization density distribution data show that in postmenopausal osteoporosis 3-year treatment with risedronate preserves or may increase trabecular bone volume, unlike placebo. This analysis also allows, for the first time, separation of the contributions of bone volume and matrix mineralization to the increase in BMD.

Interrelationships between bone microarchitecture and strength in ovariectomized monkeys treated with teriparatide

Bone microarchitecture measured at the iliac crest at 6 mo was confirmed to be a reasonable surrogate for, and a predictor of, architecture and strength of the femoral neck and lumbar vertebra after 18 mo of teriparatide treatment. However, the data taken together showed the importance of cortical bone volume for vertebra to assess pharmacological effects on bone quality.

INTRODUCTION

Improvements in bone architecture with teriparatide treatment are suggested to contribute to fracture risk reduction in osteoporotic patients. Teriparatide significantly improves microarchitecture in the iliac crest of humans by stimulating bone modeling and remodeling processes that differ dramatically from those induced by antiresorptives. The relationship between improvements of bone microarchitecture and improvements of bone strength with teriparatide treatment has not yet been fully studied.

MATERIALS AND METHODS

Ovariectomized monkeys were administered vehicle (n = 20); teriparatide 1.0 microg/kg/d (n = 19); or teriparatide 5.0 microg/kg/d (n = 21) for 18 mo. Iliac crest biopsies were obtained at 6 and 15 mo after initiation of treatment. Animals were killed after 18 mo of treatment, and adjacent vertebrae or contralateral proximal femora were processed for biomechanical or histomorphometric analyses. Pearson correlation analyses were performed to assess the relationship between biomechanical and static histomorphometric parameters of lumbar vertebra, femoral neck, and iliac crest biopsies.

RESULTS

Static histomorphometric parameters of the 6- and 15-mo biopsies were significantly correlated with the vertebral and femoral neck parameters obtained at 18 mo of teriparatide treatment. Iliac crest biopsy parameters at 6 and 15 mo also correlated with vertebral and femoral neck strength at 18 mo. Static histomorphometry of the lumbar vertebra and femoral neck at 18 mo also significantly correlated with strength at these sites. However, cortical bone volume of the lumbar vertebrae had the strongest correlation with vertebral and femoral neck strength (r = 0.74 and 0.71, respectively).

CONCLUSIONS

Teriparatide dose dependently improved cortical and trabecular microarchitecture of vertebra and femoral neck, as well as trabecular microarchitecture of the iliac crest. Bone microarchitecture at all sites was significantly correlated with lumbar vertebra and femoral neck strength. Cortical bone volume of vertebra had the strongest correlation with vertebral and femoral neck strength. Therefore, structural improvement seemed to be part of the mechanism for improved strength observed with teriparatide treatment. Trabecular bone architecture of the iliac crest at 6 mo also correlated with vertebral and femoral neck strength, as did femoral neck (cortical and trabecular) histomorphometry and trabecular histomorphometry of vertebra after 18 mo of treatment. Because clinical assessment of cortical bone volume is not readily possible for vertebra noninvasively, these findings confirm the importance of iliac crest biopsies to monitor skeletal health and show that biopsies are a reasonable surrogate to assess spine and femoral neck structure and function.

Quantifying the treatment effect explained by markers in the presence of measurement error

Surrogate markers or intermediate markers are important in identifying subjects with high risk of a serious disease or for monitoring disease progression of a subject on treatment. Quantifying the proportion of treatment effect (PTE) explained by markers has been studied extensively. Due to reasons such as biological variation, limited machine precision, etc. markers are generally measured with error. The estimated PTE ignoring the measurement error could be biased, which may lead to incorrect conclusions. In this article, we adjust for the measurement error using regression calibration to construct a less biased estimator of excess relative odds, a quantity to measure the treatment effect explained by markers. The method is applied to data from a clinical study in osteoporosis.

Zoledronic acid prevents cancer treatment-induced bone loss in premenopausal women receiving adjuvant endocrine therapy for hormone-responsive breast cancer: a report from the Austrian Breast and Colorectal Cancer Study Group

PURPOSE

Adjuvant therapy for breast cancer can be associated with decreased bone mineral density (BMD) that may lead to skeletal morbidity. This study examined whether zoledronic acid can prevent bone loss associated with adjuvant endocrine therapy in premenopausal patients.

PATIENTS AND METHODS

This study is a randomized, open-label, phase III, four-arm trial comparing tamoxifen (20 mg/d orally) and goserelin (3.6 mg every 28 days subcutaneously) +/- zoledronic acid (4 mg intravenously every 6 months) versus anastrozole (1 mg/d orally) and goserelin +/- zoledronic acid for 3 years in premenopausal women with hormone-responsive breast cancer. In a BMD subprotocol at three trial centers, patients underwent serial BMD measurements at 0, 6, 12, 24, and 36 months.

RESULTS

Four hundred one patients were included in the BMD subprotocol. Endocrine treatment without zoledronic acid led to significant (P < .001) overall bone loss after 3 years of treatment (BMD, -14.4% after 36 months; mean T score reduction, -1.4). Overall bone loss was significantly more severe in patients receiving anastrozole/goserelin (BMD, -17.3%; mean T score reduction, -2.6) compared with patients receiving tamoxifen/goserelin (BMD, -11.6%; mean T score reduction, -1.1). In contrast, BMD remained stable in zoledronic acid-treated patients (P < .0001 compared with endocrine therapy alone). No interactions with age or other risk factors were noted.

CONCLUSION

Endocrine therapy caused significant bone loss that increased with treatment duration in premenopausal women with breast cancer. Zoledronic acid 4 mg every 6 months effectively inhibited bone loss. Regular BMD measurements and initiation of concomitant bisphosphonate therapy on evidence of bone loss should be considered for patients undergoing endocrine therapy.

New mechanisms and targets in the treatment of bone fragility

Bone modelling and remodelling are cell-mediated processes responsible for the construction and reconstruction of the skeleton throughout life. These processes are chiefly mediated by locally generated cytokines and growth factors that regulate the differentiation, activation, work and life span of osteoblasts and osteoclasts, the cells that co-ordinate the volumes of bone resorbed and formed. In this way, the material composition and structural design of bone is regulated in accordance with its loading requirements. Abnormalities in this regulatory system compromise the material and structural determinants of bone strength producing bone fragility. Understanding the intercellular control processes that regulate bone modelling and remodelling is essential in planning therapeutic approaches to prevention and treatment of bone fragility. A great deal has been learnt in the last decade. Clinical trials carried out exclusively with drugs that inhibit bone resorption have identified the importance of reducing the rate of bone remodelling and so the progression of bone fragility to achieved fracture reductions of approx. 50%. These trials have also identified limitations that should be placed upon interpretation of bone mineral density changes in relation to treatment. New resorption inhibitors are being developed, based on mechanisms of action that are different from existing drugs. Some of these might offer resorption inhibition without reducing bone formation. More recent research has provided the first effective anabolic therapy for bone reconstruction. Daily injections of PTH (parathyroid hormone)-(1–34) have been shown in preclinical studies and in a large clinical trial to increase bone tissue mass and reduce the risk of fractures. The action of PTH differs from that of the resorption inhibitors, but whether it is more effective in fracture reduction is not known. Understanding the cellular and molecular mechanisms of PTH action, particularly its interactions with other pathways in determining bone formation, is likely to lead to new therapeutic developments. The recent discovery through mouse genetics that PTHrP (PTH-related protein) is a crucial bone-derived paracrine regulator of remodelling offers new and interesting therapeutic targets.

Effects of osteoporosis medications on bone quality

In clinical practice, the quantitative evaluation of bone tissue relies on dual-energy X-ray absorptiometry (DXA) measurements of bone mineral density (BMD) values, which are closely associated with the risk of osteoporotic fracture. However, only a small fraction of the antifracture effect of bone resorption inhibitors is ascribable to BMD gains (4% with raloxifene and 16-28% with alendronate and risedronate). Bone quality encompasses a number of bone tissue properties that govern mechanical resistance, such as bone geometry, cortical properties, trabecular microarchitecture, bone tissue mineralization, quality of collagen and bone apatite crystal, and presence of microcracks. All these properties are dependent on bone turnover and its variations. In populations, the decreases in bone resorption markers achieved with resorption inhibitors may predict in part the decrease in fracture risk. At the spine, however, this correlation exists down to a 40% fall in bone resorption markers; larger drops did not provide further protection against fractures in patients taking risedronate in one evaluation of this relationship. Osteoporosis medications can exert favorable effects on bone size and cortical thickness. Such effects have been documented with teriparatide (PTH 1-34), which is the unique purely anabolic treatment for osteoporosis available to date. More surprising are the favorable effects on bone size seen with some of the bone resorption inhibitors such as neridronate in adults with osteogenesis imperfecta. Similarly, estrogens and alendronate can increase femoral neck size in postmenopausal women. Preservation of the trabecular microarchitecture was demonstrated first with risedronate and subsequently with alendronate. In placebo-controlled studies, a deterioration in trabecular microarchitecture occurred within 1 to 3 years in the placebo groups but not in the bisphosphonate groups. Teriparatide, in contrast, improves trabecular microarchitecture, in particular by increasing connectivity and improving the plate-rod distribution. The minerals within trabecular or cortical bone can be evaluated using microradiography or synchrotron micro-computed tomography. Marked or prolonged secondary mineralization may result in poor bone quality. Increased bone mineralization is among the key effects of bone resorption inhibitors, most notably bisphosphonates. Prolonged use of the most potent bisphosphonates may lead to unwanted effects related to excessive mineralization. Microcracks may play a physiological role; however, a large number of microcracks may be deleterious via an effect on osteocytes. Excessive mineralization may promote the development of multiple microcracks. Studies of bone crystal and collagen properties with several bone resorption inhibitors, including risedronate and raloxifene, showed no harmful effects. An increasing number (several hundreds) of mandibular osteonecrosis associated with bisphosphonate therapy has been reported. The typical patient was receiving injectable bisphosphonate therapy for bone cancer and had undergone dental work shortly before bisphosphonate administration. The mechanism of this adverse effect is poorly understood.

Raloxifene enhances vertebral mechanical properties independent of bone density

Anti-remodeling agents produce similar reductions in vertebral fracture risk despite large differences in BMD changes suggesting the mechanism of fracture risk reduction may differ among these agents. Forty-eight intact (non-ovariectomized) skeletally mature female beagle dogs were treated orally for 12 months with clinically relevant doses of risedronate (RIS, 0.10 mg/kg/day), alendronate (ALN, 0.2 mg/kg/day), raloxifene (RAL, 0.50 mg/kg/day), or saline (VEH, 1 ml/kg/day). After sacrifice, the following measurements were made on vertebral bone: areal (aBMD) and volumetric (vBMD) bone mineral densities, tissue mineralization by ash content, static and dynamic histomorphometric parameters, microdamage, and extrinsic and intrinsic measures of biomechanical strength, stiffness and energy to fracture. At these doses, RAL suppressed bone turnover (-20%) significantly less than the bisphosphonates (-66 and -71%) and did not produce significant differences in aBMD, vBMD, BV/TV or percent ash compared to VEH-treated animals. Microdamage accumulation in RAL-treated animals was not significantly different than VEH; both RIS and ALN had significantly higher crack surface density compared to VEH. Stiffness was significantly higher than VEH in all treatment groups. Ultimate load divided by aBMD, a measure of strength independent of BMD, was significantly higher only in RAL-treated animals compared to VEH (+16%, P = 0.015). Based on these data, we conclude that raloxifene produces improvements in bone mechanical properties in ways that do not involve increases in BMD.

Change in lumbar spine BMD and vertebral fracture risk reduction in teriparatide-treated postmenopausal women with osteoporosis

Increases in lumbar spine BMD account for 30-41% of the vertebral fracture risk reduction with teriparatide treatment. The remaining fracture risk reduction is caused by improvements in non-BMD determinants of bone strength.

INTRODUCTION

Changes in BMD account for a small percentage of the fracture risk reduction seen in patients treated with antiresorptive drugs. The relationship between changes in lumbar spine BMD and vertebral fracture risk reduction with teriparatide treatment has not been assessed.

MATERIALS AND METHODS

The relationship between spine BMD and the risk of new vertebral fractures after teriparatide treatment was assessed using data from the Fracture Prevention Trial. Postmenopausal women with osteoporosis (n = 1637) were randomized to placebo or teriparatide 20 or 40 microg/day for a median of 19 months. Spine BMD was assessed at baseline and 18 months. Vertebrae whose fracture status changed during the trial were removed from the calculation of BMD. Baseline and endpoint lateral spine radiographs were assessed using a visual semiquantitative technique.

RESULTS

Both the baseline and change in spine BMD were contributors to vertebral fracture risk. The mean spine BMD increase in teriparatide-treated patients was 0.09 g/cm(2) across tertiles of baseline spine BMD. Compared with placebo, teriparatide significantly reduced the risk of new vertebral fracture for all endpoint BMD values. Teriparatide-mediated increases in spine BMD accounted for 30% (in the low baseline spine BMD tertile) to 41% (in the high baseline spine BMD tertile) of the reduction in vertebral fracture risk.

CONCLUSIONS

Increases in BMD account for approximately one third of the vertebral fracture risk reduction seen with teriparatide. The majority of the risk reduction, however, results from improvements in non-BMD determinants of bone strength.

[Follow-up of osteoporosis treatment]

There is no linear relation between changes in bone mineral density (BMD) and reduction in fracture risk with antiresorptive agents. Interpretation of BMD changes at the individual level requires calculating the smallest significant change at each measurement center. BMD measurement is essential before administration of antiresorptive or anabolic agents for prevention or treatment of postmenopausal osteoporosis. Biochemical markers of bone turnover can be monitored after 6 months of treatment. Their interpretation requires careful assessment of their intraindividual variability.

Bone material properties in trabecular bone from human iliac crest biopsies after 3- and 5-year treatment with risedronate

Long-term effects of risedronate on bone mineral maturity/crystallinity and collagen cross-link ratio in triple iliac crest biopsies of osteoporotic women were evaluated. In this double-blinded study, 3- and 5-year treatment with risedronate arrested the tissue aging encountered in untreated osteoporosis and in osteoporosis treated with other antiresorptives. This effect may be contributing to risedronate's antifracture efficacy.

INTRODUCTION

Risedronate is widely used in the treatment of osteoporosis. It reduces bone turnover, increases BMD, and decreases fracture risk. To date, there are no data available on the long-term effects of risedronate on bone material properties in humans.

MATERIALS AND METHODS

Osteoporotic women enrolled in the VERT-NA trial received either risedronate (5 mg/day, orally) or placebo for up to 5 years. All subjects received calcium. They also received vitamin D supplementation if deficient at baseline. Triple iliac crest biopsies were collected from a subset of these subjects at baseline, 3 years, and 5 years. Mineral maturity/crystallinity and collagen cross-link ratio was measured in these biopsies using Fourier transform infrared imaging.

RESULTS

Patients that received placebo exhibited increased mineral maturity/crystallinity and collagen cross-link ratio after 3 and 5 years compared with baseline values. On the contrary, patients that received risedronate retained baseline values in both bone material indices throughout. A more spatially detailed analysis revealed that this was achieved mainly through beneficial effects on active bone-forming areas. Surprisingly, patients that received risedronate achieved premenopausal values at bone-forming areas in both indices after 5 years of treatment.

CONCLUSION

Long-term treatment with risedronate affects bone material properties (mineral maturity/crystallinity and collagen cross-link ratio) and arrests the tissue aging apparent in untreated osteoporosis. These changes at the material level of the bone matrix may contribute to risedronate's rapid and sustained antifracture efficacy in osteoporotic patients.

The pathogenesis, epidemiology and management of glucocorticoid-induced osteoporosis

Oral glucocorticoids (GCs) are frequently used in the treatment of inflammatory conditions, such as rheumatoid arthritis or asthma. They have adverse skeletal effects, primarily through reductions in bone formation and osteocyte apoptosis. Several findings indicate that changes in the quality of bone may significantly contribute to the increased risk of fracture and that loss of BMD only partially explains the increased risk of fracture in oral GC users. Epidemiological studies have found that the increases in the risk of fracture in oral GC users are dose dependent and occur within three months of starting GC therapy. Daily doses of >2.5 mg prednisone equivalent have been associated with increases in the risk of fractures and randomised studies reported adverse skeletal effects with daily doses as low as 5 mg. After discontinuation of GC treatment, the risk of fracture may reduce towards baseline levels unless patients previously used high cumulative doses of oral GCs. Users of inhaled GCs have also an increased risk of fracture, especially at higher doses. But it is likely that this excess risk is related to the severity of the underlying respiratory disease, rather than to the inhaled GC therapy. It has been recommended that patients who start on oral GC therapy should receive calcium and vitamin D supplementation. Patients with a higher risk of fracture should also receive a bisphosphonate.

Effect of chronic glucocorticoid therapy and the gender difference on bone mineral density in liver transplant patients

BACKGROUND

Chronic glucocorticoid therapy (CGT) has been shown to result in bone density loss causing osteoporosis. Patients undergoing liver transplantation (LT) are on CGT and are at increased risk for bone disease. To further study the relationship between CGT and bone loss, we analyzed the bone mineral density (BMD) in relation to the cumulative dose of CGT in patients who had undergone LT.

MATERIALS AND METHODS

We retrospectively collected information on 57 patients who underwent LT more than 1 year ago, which included demographics, cumulative CGT dose, BMD and t-scores of the femur/lumbar vertebra as measured by dual-energy X-ray absorptiometry (DEXA) for 1 and 2 years post-transplant. Patients receiving CGT >3500 mg/1st year were compared with CGT <3500 mg the first year. The group consisted of 75% males and 25% females.

RESULTS

Data showed that all patients on CGT had a moderately increased risk of fracture one year post-transplant. In the high dose group, females had significantly worse femur BMD and t-scores that persisted through the second year. This difference was not seen in the low dose group.

CONCLUSION

We found that all liver transplant patients on CGT have an increased risk of bone disease and that female patients receiving CGT >3500 mg the first year have a much higher risk of bone disease than males and that this risk persists during the second year. Because most of the steroids are given during the 1st month post-transplant, the amount of steroids given in this time period dictates the patients' risk for the subsequent 2 years.

The effects of antifracture therapies on the components of bone strength: assessment of fracture risk today and in the future

OBJECTIVE

To summarize the current knowledge regarding the impact of the most common antifracture medications on the various determinants of bone strength.

METHODS

Relevant English-language articles acquired from Medline from 1966 to January 2005 were reviewed. Searches included the keywords bone AND 1 of the following: strength, remodeling, microcrack, structure, mineralization, collagen, organic, crystallinity, osteocyte, porosity, diameter, anisotropy, stress risers, or connectivity AND alendronate, estrogen, etidronate, hormone replacement therapy, parathyroid hormone, risedronate, OR teriparatide. Abstracts from relevant conference proceedings were also reviewed for pertinent information.

RESULTS

Antiresorptive therapies increase bone strength through decreasing bone turnover. This lower bone turnover results in a higher mean mineralization and decreases the number of active resorption pits within bone at any given time. These resorption pits are speculated to be areas of focal weakness and a higher number of them would, if all other things were equal, result in greater fragility. Parathyroid hormone therapy increases the rate of bone remodeling, which introduces many resorption pits, but this source of strength loss is thought to be compensated by rapid increases in bone mass.

CONCLUSIONS

Both the antiresorptives, particularly bisphosphonates, and the parathyroid hormone therapy increase bone strength; however, the changes that are elicited to achieve this differ significantly.

Effects of 3- and 5-year treatment with risedronate on bone mineralization density distribution in triple biopsies of the iliac crest in postmenopausal women

Long-term effects of risedronate on bone mineralization density distribution in triple transiliac crest biopsies of osteoporotic women were evaluated. In this double-blinded study, 3- and 5-year treatment with risedronate increased the degree and homogeneity of mineralization without producing hypermineralization. These changes at the material level of bone could contribute to risedronate's antifracture efficacy.

INTRODUCTION

Risedronate, a nitrogen-containing bisphosphonate, is widely used in the treatment of osteoporosis. It reduces bone turnover, increases BMD, and decreases fracture risk. To date, there are no data available on the long-term effects of risedronate on bone mineralization density distribution (BMDD) in humans.

MATERIALS AND METHODS

Osteoporotic women enrolled in the VERT-NA trial received either risedronate (5 mg/day, orally) or placebo for up to 5 years. All subjects received calcium and vitamin D supplementation if deficient at baseline. Triple iliac crest biopsies were collected from a subset of these subjects at baseline and 3 and 5 years. BMDD was measured in these biopsies using quantitative backscattered electron imaging, and the data were also compared with a normal reference group.

RESULTS

At baseline, both risedronate and placebo groups had a lower degree and a greater heterogeneity of mineralization as well as an increase in low mineralized bone compared with the normal reference group. The degree of mineralization increased significantly in the risedronate as well as in the placebo group after 3- and 5-year treatment compared with baseline. However, the degree of mineralization did not exceed that of normal. Three-year treatment with risedronate significantly increased the homogeneity of mineralization and slightly decreased low mineralized bone compared with placebo. Surprisingly with 5-year risedronate treatment, heterogeneity of mineralization increased compared with 3-year treatment, which might indicate an increase in newly formed bone.

CONCLUSIONS

Long-term treatment with risedronate affects the homogeneity and degree of mineralization without inducing hypermineralization of the bone matrix. These changes at the material level of the bone matrix may contribute to risedronate's antifracture efficacy in osteoporotic patients.

Management of osteoporosis in postmenopausal women

OBJECTIVE

To update the evidence-based position statement published by The North American Menopause Society (NAMS) in 2002 regarding the management of osteoporosis in postmenopausal women.

DESIGN

NAMS followed the general principles established for evidence-based guidelines to create this updated document. A panel of clinicians and researchers expert in the field of metabolic bone diseases and/or women's health were enlisted to review the 2002 NAMS position statement, compile supporting statements, and reach consensus on recommendations. The panel's recommendations were reviewed and approved by the NAMS Board of Trustees.

RESULTS

Osteoporosis, whose prevalence is especially high among elderly postmenopausal women, increases the risk of fractures. Hip and spine fractures are associated with particularly high morbidity and mortality in this population. Given the health implications of osteoporotic fractures, the primary goal of osteoporosis therapy is to prevent fractures, which is accomplished by slowing or stopping bone loss, maintaining bone strength, and minimizing or eliminating factors that may contribute to fractures. The evaluation of postmenopausal women for osteoporosis risk requires a medical history, physical examination, and diagnostic tests. Major risk factors for postmenopausal osteoporosis (as defined by bone mineral density) include advanced age, genetics, lifestyle factors (such as low calcium and vitamin D intake, smoking), thinness, and menopause status. The most common risk factors for osteoporotic fracture are advanced age, low bone mineral density, and previous fracture as an adult. Management focuses first on nonpharmacologic measures, such as a balanced diet, adequate calcium and vitamin D intake, adequate exercise, smoking cessation, avoidance of excessive alcohol intake, and fall prevention. If pharmacologic therapy is indicated, government-approved options are bisphosphonates, a selective estrogen-receptor modulator, parathyroid hormone, estrogens, and calcitonin.

CONCLUSIONS

Management strategies for postmenopausal women involve identifying those at risk of low bone density and fracture, followed by instituting measures that focus on reducing modifiable risk factors through lifestyle changes and, if indicated, pharmacologic therapy.

Important Determinants of Bone Strength

Osteoporosis is a systemic skeletal disorder characterized by compromised bone strength that predisposes individuals to increased fracture risk. Bone strength is determined by its material and structural properties. Bone mineral density (BMD) is a useful tool for diagnosis; however, this parameter provides information regarding only the quantity of mineral in bone, which is only one component of bone strength. Osteoporosis treatments have been shown to have beneficial effects on bone turnover, microarchitecture, and/or mineralization, all of which can help account for the reductions in fracture risk above and beyond changes in BMD. Newer noninvasive imaging methods are being developed that assess bone strength independent of BMD, and these methods should improve the assessment of fracture risk and response to treatment. These imaging methods are not currently available for routine clinical use, and therefore, clinicians need to continue for now to rely on surrogate markers of bone fragility, including BMD, prevalent fracture, and other important risk factors for fracture.

Monitoring osteoporosis therapy: bone mineral density, bone turnover markers, or both?

Monitoring the efficacy associated with antiresorptive therapy is an intuitive yet integral part of successful osteoporosis management. Although response rates to bisphosphonates in clinical trials--as judged by changes in bone mineral density (BMD)--are generally high, a small percentage of compliant patients do not respond. Accordingly, monitoring may help identify noncompliant patients and allow for other, possibly more successful, therapeutic interventions. Dual energy x-ray absorptiometry is the accepted method of assessing BMD to determine the need for treatment and to monitor its effects. Change in BMD is considered a valid intermediate end point for efficacy of fracture risk reduction. However, clinical trials have shown that the reduction in fracture risk associated with antiresorptive therapy may occur before changes in BMD become apparent. Vertebral fracture benefit is observed even among women who maintain rather than gain BMD during antiresorptive therapy. Clinical trials show that suppression of bone turnover markers after as little as 3 months of therapy is strongly associated with reductions in risk for fracture. Although formal guidelines for monitoring bone turnover markers do not yet exist, there are data to suggest that changes in these markers are valid intermediate endpoints for efficacy of fracture risk reduction that may provide valuable additional data on therapeutic success, particularly early in treatment and before changes in BMD become apparent.

Risedronate for prevention and treatment of osteoporosis in postmenopausal women

Risedronate sodium is an N-containing bisphosphonate that has been approved for the prevention and treatment of osteoporosis in postmenopausal women. An increase in the rate of bone remodelling is a regular feature of oestrogen withdrawal during the menopausal transition, but excessive remodelling leads to bone fragility. Risedronate and similar compounds reduce the rate of bone remodelling by suppressing the action of osteoclasts. The antifracture efficacy of risedronate is impressive. In large clinical trials of postmenopausal women with osteoporosis-related fracture(s) at entry, the risk of incident vertebral and non-vertebral fractures was reduced by approximately 40%. In older women at risk for hip fracture, incident hip fractures were also reduced by approximately 40%. Antifracture efficacy develops within the first 6 months, and treatment has been followed for as long as 5 years without deleterious effects on bone. We await reports of experience with risedronate in 'real-world' cases of greater complexity (i.e., in patients with co-morbidities and medications that would have excluded them from published clinical trials).

Parathyroid hormone as an anabolic skeletal therapy

The quest for effective treatment for osteoporosis merits great attention because of the widespread prevalence of this disease, which is not only associated with fragility fractures, but also with significant morbidity and mortality. The efficacy of the antiresorptive drugs in this disease is achieved by reducing bone turnover, increasing bone density and improving other aspects of bone quality. This article concentrates on another approach to the treatment of osteoporosis, namely the use of anabolic therapy, which has even greater prospects for improving bone quality. Parathyroid hormone (PTH) is currently available only as the recombinant amino-terminal fragment, PTH(1-34), known as teriparatide. The full-length molecule, human PTH(1-84), is currently being investigated, as are other PTH molecules. Teriparatide improves bone quality through actions on bone turnover, bone density, bone size and bone microarchitecture. In postmenopausal women with osteoporosis, teriparatide reduces the incidence of vertebral and nonvertebral fractures. In individuals who have previously been treated with an antiresorptive agent, the subsequent actions of teriparatide on bone density are transiently delayed if bone turnover has been markedly suppressed. Combination therapy with teriparatide or PTH(1-84) and an antiresorptive agent does not appear, at this time, to offer advantages over the use of PTH or an antiresorptive agent alone. However, in order to maintain the densitometric gains in bone density obtained with PTH, it is important to follow its use with that of an antiresorptive agent.

What is the role of DXA, QUS and bone markers in fracture prediction, treatment allocation and monitoring?

There is evidence that treatment can decrease the risk of fractures in osteoporotic patients, and screening of these patients is therefore relevant. Diagnosis of osteoporosis is based on the T-score calculated from bone mineral density (BMD) measurements. BMD measurements have been widely used for the management of osteoporosis, and a low BMD is a strong risk factor for fractures. But BMD measurement has several limitations in both diagnosis, prediction of fracture risk, and treatment follow-up. Quantitative ultrasound (QUS) parameters, an alternative to BMD in the assessment of bone, are independent risk factors for osteoporotic fracture. However, the use of QUS cannot be recommended for both allocation and monitoring of treatment. Biochemical markers of bone remodelling can be useful for both prediction of fracture risk and monitoring of treatment if sources of variability are controlled.

Epidemiology, etiology, and diagnosis of osteoporosis

Osteoporosis, a major public health problem, is becoming increasingly prevalent with the aging of the world population. Osteoporosis is a skeletal disorder characterized by compromised bone strength, which predisposes the individual to an increased risk of fractures of the hip, spine, and other skeletal sites. The clinical consequences and economic burden of this disease call for measures to assess individuals who are at high risk to allow for appropriate intervention. Many risk factors are associated with osteoporotic fracture, including low peak bone mass, hormonal factors, the use of certain drugs (eg, glucocorticoids), cigarette smoking, low physical activity, low intake of calcium and vitamin D, race, small body size, and a personal or a family history of fracture. All of these factors should be taken into account when assessing the risk of fracture and determining whether further treatment is required. Because osteoporotic fracture risk is higher in older women than in older men, all postmenopausal women should be evaluated for signs of osteoporosis during routine physical examinations. Radiologic laboratory assessments of bone mineral density generally should be reserved for patients at highest risk, including all women over the age of 65, younger postmenopausal women with risk factors, and all postmenopausal women with a history of fractures. The evaluation of biochemical markers of bone turnover has been useful in clinical research. However, the predictive factor of these measurements is not defined clearly, and these findings should not be used as a replacement for bone density testing. Together, clinical assessment of osteoporotic risk factors and objective measures of bone mineral density can help to identify patients who will benefit from intervention and, thus, can potentially reduce the morbidity and mortality associated with osteoporosis-associated fractures in this population.

Pharmacologic and nonpharmacologic management of osteoporosis

Fractures that occur as a result of osteoporosis are associated with significant morbidity, mortality, and cost. A treatment regimen consisting of both nonpharmacologic and pharmacologic interventions can be used to decrease the risk of fracture. Nonpharmacologic interventions include calcium and vitamin D supplementation, weight-bearing exercise, muscle strengthening, and fall prevention. Pharmacologic options include: the bisphosphonates, estrogen therapy, raloxifene, salmon calcitonin, and the anabolic agent teriparatide. Although bone mineral density is used clinically to diagnose osteoporosis, it is of limited value when evaluating pharmacologic treatment; the primary indicator of treatment efficacy is fracture risk reduction. The bisphosphonates are the preferred therapy for osteoporosis. Studies have demonstrated that in postmenopausal women, both risedronate and alendronate are associated with reductions in vertebral and nonvertebral fracture risk. The newest approved bisphosphonate, ibandronate, reduces vertebral fracture risk. Studies also support a reduction in fracture risk when alendronate and risedronate are used in men with osteoporosis and patients with corticosteroid-induced osteoporosis. When used appropriately, the bisphosphonates are well tolerated. Estrogen and raloxifene decrease fracture risk in postmenopausal women with osteoporosis but are associated with thromboembolic events. Use of estrogen therapy is also limited by concerns about the safety of this type of therapy. Although the anabolic agent teriparatide is associated with reductions in vertebral and nonvertebral fractures, its use has been limited by the necessity of subcutaneous administration and its cost relative to other agents. Regardless of which treatment regimen is selected, health care providers need to emphasize the importance of compliance and adherence to improve persistence with therapy, and subsequent fracture reduction efficacy.

Examining the Relationship Between Bone Mineral Density and Fracture Risk Reduction During Pharmacologic Treatment of Osteoporosis

Osteoporosis is a skeletal disorder characterized by compromised bone strength that predisposes the patient to an increased risk for fracture. Elements of bone strength include bone mineralization, architecture, turnover, size, and bone mineral density (BMD). Measurement of BMD is the most readily available, noninvasive method for assessing osteoporotic fracture risk and is used by the World Health Organization for diagnostic purposes. Because low BMD is predictive of increased fracture risk, it was believed that changes in BMD during pharmacologic therapy for osteoporosis would strongly predict observed fracture risk reductions. We examined the relationship between changes in BMD and reduction in fracture risk during pharmacologic therapy in postmenopausal women with osteoporosis. The correlation between BMD increases and fracture risk reduction during treatment is not consistent; larger increases in BMD do not necessarily correlate with greater reductions in fracture risk. Multiple factors, in addition to BMD, appear to contribute to the increased bone strength and decreased fracture risk achieved with approved drug therapies for osteoporosis. Until the exact relationship of these factors is fully understood, clinicians should continue to evaluate drug efficacy for osteoporosis based on the fracture risk reductions from well-designed clinical trials.

Patient variables impact lumbar spine dual energy X-ray absorptiometry precision

INTRODUCTION

Changes in bone mineral density are used to monitor osteoporosis therapy. To determine whether a change in bone mass is clinically significant, the precision of bone mineral density measurements must be known.

METHODS

We therefore measured the impact of vertebral body exclusion on dual energy X-ray absorptiometry (DXA) precision. At one university and one Veterans Affairs DXA center, three radiology technologists each scanned 30 participants twice, with repositioning between scans, to estimate DXA precision. Three International Society for Clinical Densitometry-certified physicians reviewed all lumbar spinal scans to note the presence of focal structural defects. We calculated precision for subsets of vertebrae, and for virtual samples of patients with and without physician-identified vertebral focal structural defects. We graphed the reciprocal of least significant change versus bone area to determine the dependence of precision on interpreted scan area.

RESULTS

Within each sample, greater interpretable bone area improved precision. The contribution of interpreted bone area to precision differed among the samples, ranging from 57 to 94%. Greater population bone mineral density heterogeneity and presence of focal structural defects each decreased precision.

CONCLUSION

All bone densitometry centers must determine precision using a sample representative of their served populations. Failure to do so may lead to incorrect determination of least significant change. Population heterogeneity, vertebral body exclusion and presence of focal structural defects each decreases precision.

Alendronic Acid Produces Greater Effects than Risedronic Acid on Bone??Density and Turnover in Postmenopausal Women with Osteoporosis

BACKGROUND

The objective of the study was to evaluate the effects of alendronic acid once weekly relative to risedronic acid once weekly on bone mineral density (BMD), markers of bone turnover and tolerability in the treatment of osteoporosis in postmenopausal women.

METHODS

This was a randomised, double-masked, double-dummy multicentre international study (75 centres in 27 countries in Europe, the Americas and Asia-Pacific). A total of 1303 women were screened and 936 with low bone density (T-score < or = -2.0 at the spine, hip trochanter, total hip or femoral neck) were randomised; 91% (n = 854) completed the study. Patients were randomised to treatment with either active alendronic acid 70 mg weekly (Fosamax) and placebo identical to risedronic acid weekly or active risedronic acid 35 mg weekly (Actonel) and placebo identical to alendronic acid weekly for 12 months. The primary efficacy endpoint was the percentage change from baseline in hip trochanter BMD at 12 months. Secondary endpoints included the percentage change from baseline in lumbar spine, total hip and femoral neck BMD; biochemical markers of bone turnover (including serum bone-specific alkaline phosphatase [BSAP] and urinary type I collagen N-telopeptides [NTx]); and safety and tolerability as assessed by reporting of adverse experiences.

RESULTS

Alendronic acid produced greater increases in BMD than did risedronic acid at 12 months at all sites measured. Mean percentage increases from baseline in hip trochanter BMD at month 12 were 3.56% and 2.71% in the alendronic acid and risedronic acid groups, respectively (treatment difference [95% CI]: 0.83% [0.22, 1.45; p = 0.008]). Mean percentage increases from baseline were greater with alendronic acid than risedronic acid at the lumbar spine, total hip and femoral neck BMD at month 12 (p = 0.002, p < 0.001, p = 0.039, respectively). Increases in BMD with alendronic acid compared with risedronic acid were also significantly greater at 6 months at the trochanter and total hip. There was a greater reduction in bone turnover with alendronic acid compared with risedronic acid: NTx decreased 58% with alendronic acid compared with 47% with risedronic acid at 12 months (p < 0.001); and BSAP decreased 45% with alendronic acid compared with 34% with risedronic acid at 12 months (p < 0.001). Overall tolerability and upper gastrointestinal tolerability were similar for both agents.

CONCLUSIONS

Alendronic acid once weekly produced greater BMD increases at both hip and spine sites and greater reductions in bone turnover relative to risedronic acid once weekly. Both agents were well tolerated with no significant difference in upper gastrointestinal adverse experiences. Clinicians should consider these results when making treatment decisions for postmenopausal women with osteoporosis.

Relationship between changes in BMD and nonvertebral fracture incidence associated with risedronate: reduction in risk of nonvertebral fracture is not related to change in BMD

Whether greater treatment-related changes in BMD result in greater decreases in fracture risk is controversial. We analyzed the relationship between BMD change and nonvertebral fracture risk in postmenopausal osteoporotic women from the risedronate fracture program. Change in BMD did not influence the magnitude of risedronate's effect on nonvertebral fractures; the incidence of nonvertebral fractures was equally low in treated patients whose BMD increased or decreased.

INTRODUCTION

In untreated patients, low BMD correlates with increased fracture risk. Whether greater increases in BMD induced by anti-osteoporosis drugs are related to greater decreases in vertebral fracture risk is controversial, and little has been written about the relationship between change in BMD and nonvertebral fracture risk. We analyzed the relationship between BMD change and nonvertebral fracture incidence using individual patient data from postmenopausal osteoporotic women receiving antiresorptive treatment with risedronate.

MATERIALS AND METHODS

This posthoc analysis combined data from three pivotal risedronate fracture endpoint trials. Women received risedronate 2.5 or 5 mg (n = 2,561) or placebo (n = 1,418) daily for up to 3 years. BMD and nonvertebral fractures confirmed by radiograph (hip, wrist, pelvis, humerus, clavicle, and leg) were assessed periodically over 3 years.

RESULTS

The incidence of nonvertebral fractures in risedronate-treated patients was not different between patients whose spine BMD decreased (7.8%) and those whose spine BMD increased (6.4%; hazard ratio to subgroup of patients who lost BMD [HR], 0.79; 95% CI, 0.50, 1.25) or between those whose femoral neck BMD decreased (7.6%) and those whose femoral neck BMD increased (7.5%; HR, 0.93; 95% CI, 0.68, 1.28). The changes in lumbar spine and femoral neck BMD explained only 12% (95% CI, 2%, 21%; p = 0.014) and 7% (95% CI, 2%, 13%; p = 0.005), respectively, of risedronate's nonvertebral fracture efficacy.

CONCLUSIONS

For patients treated with risedronate, changes in BMD as measured by DXA do not predict the degree of reduction in nonvertebral fractures.

Effect of osteoporosis treatments on risk of non-vertebral fractures: review and meta-analysis of intention-to-treat studies

Most osteoporosis treatments have proven efficacy in reducing the risk of vertebral fractures, whereas evidence is less straightforward for prevention of non-vertebral fractures. Conclusions as to the efficacy of a treatment should be based primarily on analyses of the intention to treat (ITT) population rather than on exploratory subgroup analyses; however, non-vertebral anti-fracture efficacy has been largely derived by post-hoc subgroup analyses. This review and meta-analysis was performed to assess non-vertebral anti-fracture efficacy of several osteoporosis therapies, including a more stringent assessment of the ITT populations. Data on non-vertebral anti-fracture efficacy, a defined endpoint of the ITT analyses and confirmed by radiographs, were obtained from randomized, placebo-controlled, phase III clinical trials of at least 3-year duration. Meta-analyses were performed for the two bisphosphonates, alendronate and risedronate. Relative risks (RR), 95% confidence intervals (CI) and statistical significance for active treatment compared with placebo were calculated. Eleven clinical trials met the criteria for review, three of which showed statistically significant ( P < or =0.05) non-vertebral anti-fracture efficacy in the ITT population: two trials with risedronate and one trial with strontium. A meta-analysis showed significant reductions in the relative risk of non-vertebral fracture for both alendronate (RR=0.86; 95% CI: 0.76-0.97, P =0.012) and risedronate (RR=0.81; 95% CI: 0.71-0.92, P =0.001). Risedronate and strontium ranelate were the only treatments to show non-vertebral anti-fracture efficacy in this robust assessment of anti-fracture efficacy of osteoporosis therapy using ITT populations in trials of 3 years or more in duration. Risedronate was the only agent shown to demonstrate efficacy in more than one trial. Meta-analysis showed that both alendronate and risedronate provide non-vertebral anti-fracture efficacy.

Review of Treatment Modalities for Postmenopausal Osteoporosis

This review summarizes and updates data presented at recent annual Southern Medical Association conferences on postmenopausal osteoporosis. As part of any osteoporosis treatment program, it is important to maintain adequate calcium and 25-hydroxyvitamin D levels either through diet or supplementation. Among the available pharmacologic therapies, the bisphosphonates alendronate and risedronate have demonstrated the most robust fracture risk reductions-approximately 40 to 50% reduction in vertebral fracture risk, 30 to 40% in nonvertebral fracture risk, and 40 to 60% in hip fracture risk. Ibandronate, a new bisphosphonate, has demonstrated efficacy in reducing vertebral fracture risk. Salmon calcitonin nasal spray and raloxifene demonstrated significant reductions in vertebral fracture risk in pivotal studies. Teriparatide significantly reduced vertebral and nonvertebral fracture risk. Drugs on the horizon include strontium ranelate, which has been shown to reduce vertebral and nonvertebral fracture risk, and zoledronic acid, an injectable bisphosphonate that increased bone density with once-yearly administration.