Relationship between changes in bone mineral density and fracture risk reduction with antiresorptive drugs: some issues with meta-analyses

Changes in Testing and Treatment Methods in Osteoporosis Care

Osteoporosis treatment plays a crucial role in preventing fractures, particularly in bedridden patients. We conducted a questionnaire survey presenting hypothetical clinical cases in 2015 and 2020 to investigate trends over a 5-year period. The target population included physicians working in clinics and hospitals within our neighbourhood. The cases were presented, and the questionnaire was administered in a confidential format. The orthopaedic surgeons were matched for age and practice, resulting in 74 cases being included in the analysis. Comparing the 2015 and 2020 results, we observed a notable increase in physicians who would perform "bone mineral density measurements of the lumbar spine and hip." Furthermore, there was a significant rise in the percentage of respondents willing to test for bone metabolic markers, such as serum type I collagen cross-linked N-telopeptide (NTX), procollagen I N-terminal propeptide (P1NP), and tartrate-resistant acid phosphatase 5b (TRACP-5b). Regarding therapeutic agents, bisphosphonates decreased in usage, whereas parathyroid hormone and romosozumab witnessed an increase. In conclusion, the percentage of physicians requesting bone mineral density measurements of the lumbar spine and hip increased over the five-year period. In addition, more physicians chose to utilise bone metabolic markers due to their ease of measurement through blood tests and reduced diurnal variation. Finally, there was a marked trend towards the administration of drugs capable of rapidly and effectively increasing bone mineral density at an early stage of treatment.

A review of the skeletal effects of exposure to high altitude and potential mechanisms for hypobaric hypoxia-induced bone loss

Mountaineering and exposure to high altitude result in physiological adaptations to the reduced inspiratory oxygen availability. Acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE) are well-described harmful effects of exposure to high altitude. Common to AMS, HAPE, and HACE are distinct clinical signs and symptoms of impaired function. However, several studies have suggested that high altitude might result in a substantial bone loss, which usually does not produce any apparent symptoms. This review aims to provide a comprehensive overview of, and map current knowledge of the skeletal effects of hypobaric hypoxia and high altitude. PubMed and Embase were searched from inception to September 6, 2021, to identify studies investigating the skeletal effects of exposure to hypobaric hypoxia and high altitude. Three hundred sixty titles and abstracts were screened, and 20 full-text articles were included (16 in vivo studies and four real-world human studies). In rodents, simulated high altitude up to 2900 m did not result in any adverse skeletal effects. In contrast, studies exposing animals to very high altitude (3500-5500 m) reported substantial reductions in BMD, cortical morphology, and bone strength, as well as deteriorated trabecular microstructure. Detrimental microstructural effects were also reported in rats exposed to simulated extreme altitude (6000 m). Finally, real-world human studies in mountaineers suggested high altitude exposure reduced bone mineral density (BMD) and that the harmful skeletal effects of hypobaric hypoxia were not entirely recovered after 12 months. In conclusion, in vivo and real-world studies demonstrated high altitude exposure results in adverse skeletal effects. The underlying mechanism for hypobaric hypoxia-induced bone loss is not elucidated.

Bone mineral density response prediction following osteoporosis treatment using machine learning to aid personalized therapy

Osteoporosis is a global health problem for ageing populations. The goals of osteoporosis treatment are to improve bone mineral density (BMD) and prevent fractures. One major obstacle that remains a great challenge to achieve the goals is how to select the best treatment regimen for individual patients. We developed a computational model from 8981 clinical variables, including demographic data, diagnoses, laboratory results, medications, and initial BMD results, taken from 10-year period of electronic medical records to predict BMD response after treatment. We trained 7 machine learning models with 13,562 osteoporosis treatment instances [comprising 5080 (37.46%) inadequate treatment responses and 8482 (62.54%) adequate responses] and selected the best model (Random Forests with area under the receiver operating curve of 0.70, accuracy of 0.69, precision of 0.70, and recall of 0.89) to individually predict treatment responses of 11 therapeutic regimens, then selected the best predicted regimen to compare with the actual regimen. The results showed that the average treatment response of the recommended regimens was 9.54% higher than the actual regimens. In summary, our novel approach using a machine learning-based decision support system is capable of predicting BMD response after osteoporosis treatment and personalising the most appropriate treatment regimen for an individual patient.

Relationship Between Bone Mineral Density and Risk of Vertebral Fractures with Denosumab Treatment in Japanese Postmenopausal Women and Men with Osteoporosis

In this post hoc analysis of the Denosumab Fracture Intervention Randomized Placebo-Controlled Trial (DIRECT) in Japanese postmenopausal women and men with osteoporosis, we evaluated the relationship between vertebral fracture risk and both bone mineral density (BMD) T-score and percent change after 24 months of denosumab treatment at total hip, femoral neck, and lumbar spine. Logistic regression analysis was performed and the proportion of treatment effect explained by BMD in vertebral fracture risk was estimated. The results demonstrate that both total hip BMD T-score and change can be strong predictors of subsequent fracture risk, and that total hip BMD change explained 73%, while T-score explained 23%, of the treatment effect. In contrast, neither femoral neck BMD change nor T-score can predict the effect of denosumab on vertebral fracture risk. Furthermore, although lumbar spine BMD T-score was associated with vertebral fracture incidence, lumbar spine BMD change was inversely related to vertebral fracture risk. Because there was no relationship between lumbar spine BMD change and T-score at 24 months of denosumab treatment, and because there can be small undetectable vertebral deformities that may increase BMD values, these results suggest that lumbar spine BMD change is not a good surrogate for vertebral fracture risk assessment. It is suggested that both total hip BMD change and T-score can be good surrogates for predicting vertebral fracture risk in Japanese patients with osteoporosis under denosumab treatment.ClinicalTrials.gov identifier: NCT00680953.

Randomized head-to-head comparison of minodronic acid and raloxifene for fracture incidence in postmenopausal Japanese women: the Japanese Osteoporosis Intervention Trial (JOINT)-04

AIMS

We conducted a head-to-head randomized trial of minodronate, a bisphosphonate, and raloxifene, a selective estrogen receptor modulator, to obtain clinical evidence and information about their efficacy and safety.

METHODS

The Japanese Osteoporosis Intervention Trial protocol number 4 (JOINT-04) trial is a multi-center, open-labeled, blinded endpoints, head-to-head randomized trial of minodronate and raloxifene. Ambulatory elderly women with osteoporosis (age, >60 years) were randomly allocated to the raloxifene or minodronate group by central registration. The co-primary endpoints included any one of osteoporotic fractures (vertebral, humeral, femoral, and radial fractures), vertebral fractures, and major osteoporotic fractures (clinical vertebral, humeral, femoral, and radial fractures). The biological effects of each drug, patients' quality of life, and drug safety were assessed based on the secondary outcomes. This study was registered at the University Hospital Medical Information Network-Clinical Trials Registry (UMIN-CTR) under trial identification number UMIN000005433.

RESULTS

A total of 3896 patients were randomized to the minodronate and raloxifene groups, and drug efficacy assessments were performed for 3247 patients (1623 and 1624 patients, respectively). Among these patients, 1176 and 1187 patients received allocated treatment for 2 years. The incidence rate ratios for osteoporotic, vertebral, and major osteoporotic fractures in the minodronate group were 0.94 (95% CI: 0.78-1.13, p = .494), 0.86 (95% CI: 0.70-1.05, p = .147), and 1.22 (95% CI: 0.86-1.74, p = .274), respectively. Compared to the raloxifene group, the minodronate group showed significantly increased bone mineral density of the lumbar spine for each visit (6 months: p = .007, 12 months: p = .0003, 24 months: p<.0001). Also, serious adverse reactions were observed for four and six patients in the minodronate and raloxifene groups, respectively.

CONCLUSIONS

Overall, there were no statistical differences in the incidence rates of osteoporotic, vertebral, or major osteoporotic fractures between the two groups. Serious adverse reactions were rare in both groups.

YAP and TAZ Mediate Osteocyte Perilacunar/Canalicular Remodeling

Bone fragility fractures are caused by low bone mass or impaired bone quality. Osteoblast/osteoclast coordination determines bone mass, but the factors that control bone quality are poorly understood. Osteocytes regulate osteoblast and osteoclast activity on bone surfaces but can also directly reorganize the bone matrix to improve bone quality through perilacunar/canalicular remodeling; however, the molecular mechanisms remain unclear. We previously found that deleting the transcriptional regulators Yes-associated protein (YAP) and transcriptional co-activator with PDZ-motif (TAZ) from osteoblast-lineage cells caused lethality in mice due to skeletal fragility. Here, we tested the hypothesis that YAP and TAZ regulate osteocyte-mediated bone remodeling by conditional ablation of both YAP and TAZ from mouse osteocytes using 8 kb-DMP1-Cre. Osteocyte-conditional YAP/TAZ deletion reduced bone mass and dysregulated matrix collagen content and organization, which together decreased bone mechanical properties. Further, YAP/TAZ deletion impaired osteocyte perilacunar/canalicular remodeling by reducing canalicular network density, length, and branching, as well as perilacunar flourochrome-labeled mineral deposition. Consistent with recent studies identifying TGF-β as a key inducer of osteocyte expression of matrix-remodeling enzymes, YAP/TAZ deletion in vivo decreased osteocyte expression of matrix proteases MMP13, MMP14, and CTSK. In vitro, pharmacologic inhibition of YAP/TAZ transcriptional activity in osteocyte-like cells abrogated TGF-β-induced matrix protease gene expression. Together, these data show that YAP and TAZ control bone matrix accrual, organization, and mechanical properties by regulating osteocyte-mediated bone remodeling. Elucidating the signaling pathways that control perilacunar/canalicular remodeling may enable future therapeutic targeting of bone quality to reverse skeletal fragility. © 2019 American Society for Bone and Mineral Research.

European guidance for the diagnosis and management of osteoporosis in postmenopausal women

Guidance is provided in a European setting on the assessment and treatment of postmenopausal women at risk from fractures due to osteoporosis.

INTRODUCTION

The International Osteoporosis Foundation and European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis published guidance for the diagnosis and management of osteoporosis in 2013. This manuscript updates these in a European setting.

METHODS

Systematic reviews were updated.

RESULTS

The following areas are reviewed: the role of bone mineral density measurement for the diagnosis of osteoporosis and assessment of fracture risk; general and pharmacological management of osteoporosis; monitoring of treatment; assessment of fracture risk; case-finding strategies; investigation of patients; health economics of treatment. The update includes new information on the evaluation of bone microstructure evaluation in facture risk assessment, the role of FRAX® and Fracture Liaison Services in secondary fracture prevention, long-term effects on fracture risk of dietary intakes, and increased fracture risk on stopping drug treatment.

CONCLUSIONS

A platform is provided on which specific guidelines can be developed for national use.

Fragility Fractures & Their Impact on Older People

Osteoporotic fractures, in particular hip and vertebral, are a major health burden worldwide. The majority of these fractures occur in the elderly population, resulting in one of the most important causes of mortality and disability in older ages. Their cost for societies is enormous and is forecast to steadily increase over the coming decades globally. Low bone mineral density (BMD) remains a key preventable risk factor for fractures. Screening and treatment of individuals with high risk of fracture is cost-effective. Predictive tools including clinical risk factors, minimisation of falls risk and public authorities' support to create Fracture Liaison Services are paramount strategies.

Romosozumab Treatment Converts Trabecular Rods into Trabecular Plates in Male Cynomolgus Monkeys

Treatment with sclerostin antibody (romosozumab) increases bone formation while reducing bone resorption, leading to increases in bone volume and bone mineral density. Sclerostin antibody treatment may also provide beneficial changes in trabecular microarchitecture and strength that are not reflected in bone volume and density. Here we use three-dimensional dynamic histomorphometry to determine longitudinal changes in vertebral trabecular microarchitecture in adolescent male cynomolgus monkeys (4-5 years old) treated with sclerostin antibody. Animals were treated bi-weekly with either sclerostin antibody (30 mg/kg, sc, n = 6) or vehicle (n = 6) for 10 weeks. Animals were administered fluorochrome bone formation labels on days 14 and 24 (tetracycline) and on days 56 and 66 (calcein), followed by necropsy on day 70. Cylindrical specimens of cancellous bone from the 5th lumbar vertebrae were used to generate high-resolution, three-dimensional images of bone and fluorescent labels of bone formation (0.7 × 0.7 × 5.0 µm/voxel). The three-dimensional images of the bone formation labels were used to determine the bone volume formed between days 14 and 66 and the resulting alterations in trabecular microarchitecture within each bone. Treatment with sclerostin antibody resulted in a conversion of rod-like trabeculae into plate-like trabeculae at a higher rate than in vehicle-treated animals (p = 0.01). Plate bone volume fraction was greater in the sclerostin antibody group relative to vehicle (mean 43 vs. 30%, p < 0.05). Bone formation increased the thickness of trabeculae in all three trabecular orientations (axial, oblique, and transverse, p < 0.05). The volume of bone formed between days 14 to 66 was greater in sclerostin antibody-treated groups (9.0 vs. 5.4%, p = 0.02), and new bone formation due to sclerostin antibody treatment was associated with increased apparent stiffness as determined from finite element models. Our results demonstrate that increased bone formation associated with sclerostin antibody treatment increases plate-like trabecular morphology and improves mechanical performance.

Italian association of clinical endocrinologists (AME) position statement: drug therapy of osteoporosis

Treatment of osteoporosis is aimed to prevent fragility fractures and to stabilize or increase bone mineral density. Several drugs with different efficacy and safety profiles are available. The long-term therapeutic strategy should be planned, and the initial treatment should be selected according to the individual site-specific fracture risk and the need to give the maximal protection when the fracture risk is highest (i.e. in the late life). The present consensus focused on the strategies for the treatment of postmenopausal osteoporosis taking into consideration all the drugs available for this purpose. A short revision of the literature about treatment of secondary osteoporosis due both to androgen deprivation therapy for prostate cancer and to aromatase inhibitors for breast cancer was also performed. Also premenopausal females and males with osteoporosis are frequently seen in endocrine settings. Finally particular attention was paid to the tailoring of treatment as well as to its duration.

Bone Tissue Properties Measurement by Reference Point Indentation in Glucocorticoid-Induced Osteoporosis

Glucocorticoids, widely used in inflammatory disorders, rapidly increase bone fragility and, therefore, fracture risk. However, common bone densitometry measurements are not sensitive enough to detect these changes. Moreover, densitometry only partially recognizes treatment-induced fracture reductions in osteoporosis. Here, we tested whether the reference point indentation technique could detect bone tissue property changes early after glucocorticoid treatment initiation. After initial laboratory and bone density measurements, patients were allocated into groups receiving calcium + vitamin D (Ca+D) supplements or anti-osteoporotic drugs (risedronate, denosumab, teriparatide). Reference point indentation was performed on the cortical bone layer of the tibia by a handheld device measuring bone material strength index (BMSi). Bone mineral density was measured by dual-energy X-ray absorptiometry (DXA). Although Ca+D-treated patients exhibited substantial and significant deterioration, risedronate-treated patients exhibited no significant change, and both denosumab- and teriparatide-treated participants exhibited significantly improved BMSi 7 weeks after initial treatment compared with baseline; these trends remained stable for 20 weeks. In contrast, no densitometry changes were observed during this study period. In conclusion, our study is the first to our knowledge to demonstrate that reference point indentation is sensitive enough to reflect changes in cortical bone indentation after treatment with osteoporosis therapies in patients newly exposed to glucocorticoids.

Monitoring of osteoporosis therapy

Over the past two decades, major advances have been made in the number and range of agents available for the treatment of osteoporosis, all with proven anti-fracture efficacy. Unfortunately, compliance with these treatments is not optimal, and a number of patients could be considered as non-responders. Consequently, monitoring anti-osteoporotic therapy could be part of successful osteoporosis management. Currently, no formal well-accepted clinical practice guidelines are available for monitoring anti-osteoporosis therapies. Changes in bone mineral density and bone turnover markers, while on therapy, have potential value in monitoring treatment but their assessment and, consequently, their benefits could be limited by metrological and clinical issues. Moreover, their effectiveness is probably drug dependant. Recommendation for the standardisation of the methodology when analysing the potential relevance of tools for the monitoring of osteoporosis therapy is needed.

Reprint of: Musculoskeletal system in the old age and the demand for healthy ageing biomarkers

Population ageing has emerged as a major demographic trend worldwide due to improved health and longevity. This global ageing phenomenon will have a major impact on health-care systems worldwide due to increased morbidity and greater needs for hospitalization/institutionalization. As the ageing population increases worldwide, there is an increasing awareness not only of increased longevity but also of the importance of "healthy ageing" and "quality of life". Yet, the age related chronic inflammation is believed to be pathogenic with regards to its contribution to frailty and degenerative disorders. In particular, the frailty syndrome is increasingly being considered as a key risk indicator of adverse health outcomes. In addition, elderly may be also prone to be resistant to anabolic stimuli which is likely a key factor in the loss of skeletal muscle mass with ageing. Vital to understand these key biological processes is the development of biological markers, through system biology approaches, aiding at strategies for tailored therapeutic and personalized nutritional program. Overall aim is to prevent or attenuate decline of key physiological functions required to live an active, independent life. This review focus on core indicators of health and functions in older adults, where nutrition and tailored personalized programs could exhibit preventive roles, and where the aid of metabolomics technologies are increasingly displaying potential in revealing key molecular mechanisms/targets linked to specific ageing and/or healthy ageing processes.

Anti-resorptive agents reduce the size of resorption cavities: a three-dimensional dynamic bone histomorphometry study

Alterations in resorption cavities and bone remodeling events during anti-resorptive treatment are believed to contribute to reductions in fracture risk. Here, we examine changes in the size of individual remodeling events associated with treatment with a selective estrogen receptor modulator (raloxifene) or a bisphosphonate (risedronate). Adult female rats (6months of age) were submitted to ovariectomy (n=17) or sham surgery (SHAM, n=5). One month after surgery, the ovariectomized animals were separated into three groups: untreated (OVX, n=5), raloxifene treated (OVX+Ral, n=6) and risedronate treated (OVX+Ris, n=6). At 10months of age, the lumbar vertebrae were submitted to three-dimensional dynamic bone histomorphometry to examine the size (depth, breadth and volume) of individual resorption cavities and formation events. Maximum resorption cavity depth did not differ between the SHAM (23.66±1.87μm, mean±SD) and OVX (22.88±3.69μm) groups but was smaller in the OVX+Ral (14.96±2.30μm) and OVX+Ris (14.94±2.70μm) groups (p<0.01). Anti-resorptive treatment was associated with reductions in the surface area of resorption cavities and the volume occupied by each resorption cavity (p<0.01 each). The surface area and volume of individual formation events (double-labeled events) in the OVX+Ris group were reduced as compared to other groups (p<0.02). Raloxifene treated animals showed similar amounts of bone remodeling (ES/BS and dLS/BS) compared to sham-operated controls but smaller cavity size (depth, breadth and volume). The current study shows that anti-resorptive agents influence the size of resorption cavities and individual remodeling events and that the effect of anti-resorptives on individual remodeling events may not always be directly related to the degree of suppression of bone remodeling.

Pharmacogenetics of osteoporosis: towards novel theranostics for personalized medicine?

Osteoporosis is a complex multifactorial bone disorder with a strong genetic basis. It is the most common, severe, progressive skeletal illness that has been increasing, particularly in developed countries. Osteoporosis will no doubt constitute a serious clinical burden in healthcare management in the coming decades. The genetics of osteoporosis should be analyzed from both the disease susceptibility and the pharmacogenetic treatment perspectives. The former has been widely studied and discussed, while the latter still requires much more information and research. This article provides a synthesis of the literature on the genetics of osteoporosis and an update on progress made in pharmacogenetics of osteoporosis in recent years, specifically regarding the new molecular targets for antiresorptive drugs. In-depth translation of osteoporosis pharmacogenetics approaches to clinical practice demands a new vision grounded on the concept of "theranostics," that is, the integration of diagnostics for both disease susceptibility testing, as well as for prediction of health intervention outcomes. In essence, theranostics signals a broadening in the scope of inquiry in diagnostics medicine. The upcoming wave of theranostics medicine also suggests more distributed forms of science and knowledge production, both by experts and end-users of scientific products. Both the diagnosis and personalized treatment of osteoporosis could conceivably benefit from the emerging postgenomics field of theranostics.

European guidance for the diagnosis and management of osteoporosis in postmenopausal women

Guidance is provided in a European setting on the assessment and treatment of postmenopausal women at risk of fractures due to osteoporosis.

INTRODUCTION

The International Osteoporosis Foundation and European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis published guidance for the diagnosis and management of osteoporosis in 2008. This manuscript updates these in a European setting.

METHODS

Systematic literature reviews.

RESULTS

The following areas are reviewed: the role of bone mineral density measurement for the diagnosis of osteoporosis and assessment of fracture risk, general and pharmacological management of osteoporosis, monitoring of treatment, assessment of fracture risk, case finding strategies, investigation of patients and health economics of treatment.

CONCLUSIONS

A platform is provided on which specific guidelines can be developed for national use.

Treatment failure in osteoporosis

Guidelines concerning the definition of failure of therapies used to reduce the risk of fracture are provided.

INTRODUCTION

This study aims to provide guidelines concerning the definition of failure of therapies used to reduce the risk of fracture.

METHODS

A working group of the Committee of Scientific Advisors of the International Osteoporosis Foundation was convened to define outcome variables that may assist clinicians in decision making.

RESULTS

In the face of limited evidence, failure of treatment may be inferred when two or more incident fractures have occurred during treatment, when serial measurements of bone remodelling markers are not suppressed by anti-resorptive therapy and where bone mineral density continues to decrease.

CONCLUSION

The provision of pragmatic criteria to define failure to respond to treatment provides an unmet clinical need and may stimulate research into an important issue.

The importance of absolute bone mineral density in the assessment of antiresorptive agents used for the prevention of osteoporotic fractures

The usefulness of bone mineral density (BMD) monitoring during antiresorptive treatment is still controversial. This study aimed to determine which factors of change (absolute value or the percent change from the baseline) in BMD are associated with the risk of future fractures. A total of 565 postmenopausal osteoporosis who were treated antiresorptive drugs were included in this prospective observational study. Lumbar BMD (LBMD) was measured at baseline and 1-yr after the initial and subsequent incident fracture was observed. The percent changes in LBMD at 1 yr were 5.4 ± 6.4% and 118 (20.9%) achieved increased LBMD with change of classification to >-2.5 standard deviation (SD). After the initial 1-yr examination, incident fractures developed in 152 (26.9%). The incident fracture risk was significantly associated with the absolute value in LBMD, but not with the percent change. A Cox proportional hazard model demonstrated that increased LBMD with change of classification to >-2.5 SD was a significant predictor for a reduction in incident fractures (hazard ratio: 0.41, 95% confidence interval: 0.21-0.71). In conclusion, these results suggest that monitoring of the antifracture efficacy of antiresorptive treatments should be based on the absolute value of BMD. In particular, increased change to >-2.5 SD is important for reducing the future fracture risk.

Relationships between changes in bone mineral density or bone turnover markers and vertebral fracture incidence in patients treated with bazedoxifene

We analyzed the relationships between bone mineral density (BMD) or bone turnover marker (BTM) changes and vertebral fracture incidence in women treated with bazedoxifene using a post hoc analysis from a 3-year randomized, placebo-controlled study evaluating the effect of bazedoxifene (20 or 40 mg) on fracture risk reduction. BMD was assessed at baseline and every 6 months for 3 years. Osteocalcin and C-telopeptide of type I collagen were assessed at baseline and at 3, 12, and 36 months. Vertebral fractures were assessed with a semiquantitative visual assessment. Data were available for 5,244 women, of whom 3,476 were treated with bazedoxifene. Using a logistic regression analysis and the classical Li approach, the proportion of fracture incidence explained by BMD change after 3 years of bazedoxifene treatment was 29 % for the total hip and 44 % for the femoral neck. The proportion of treatment explained by lumbar BMD change could not be quantified accurately because of the significant interaction between treatment and change in BMD. With the same model, the 12-month BTM changes explained up to 29 % of the fracture risk reduction observed with the two forms of bazedoxifene. In women treated with bazedoxifene, changes in femoral neck BMD, hip BMD, or BTMs explained a moderate proportion of the fracture risk reduction observed during the 3 years of follow-up. However, BMD or BTM changes cannot be recommended for individual monitoring of women treated with bazedoxifene.

New advances in imaging osteoporosis and its complications

Tremendous advances have been made over the past several decades in assessing osteoporosis and its complications. High resolution imaging combined with sophisticated computational techniques now provide a detailed analysis of bone structure and a much more accurate prediction of bone strength. These techniques have shown how different mechanisms of age-related bone weakening exist in males and females. Limitations peculiar to these more advanced imaging techniques currently hinder their adoption into mainstream clinical practice. As such, the ultimate quest remains a readily available, safe, high resolution technique capable of fully predicting bone strength, capable of showing how bone strength is faltering and precisely monitoring treatment effect. Whether this technique will be based on acquisition of spine/hip data or data obtained at peripheral sites reflective of changes happening in the spine and hip regions is still not clear. In the meantime, mainstream imaging will continue to improve the detection of osteoporosis related insufficiency fracture in the clinical setting. We, as clinicians, should aim to increase awareness of this fracture type both as a frequent and varied source of pain in patients with osteoporosis and as the ultimate marker of severely impaired bone strength.

Muscle strength and body composition are clinical indicators of osteoporosis

We examined the role of muscle strength, lean tissue distribution, and overall body composition as indicators of osteoporosis (OP) in a pooled sample of 979 Finnish postmenopausal women (mean age 68.1 years) from the Kuopio Osteoporosis Risk Factor and Prevention study. Bone mineral density (BMD) at the femoral neck (FN) and total body composition were assessed by dual-energy X-ray absorptiometry scans. The women (n = 979) were divided into three groups according to WHO criteria, based on FN BMD T score: normal (n = 474), osteopenia (n = 468), and OP (n = 37). Soft tissue proportions, fat mass index (FMI, fat/height²), lean mass index (LMI, lean/height²), and appendicular skeletal muscle mass (ASM, (arms + legs)/height²) were calculated. Handgrip and knee extension strength measurements were made. OP subjects had significantly smaller LMI (p = 0.001), ASM (p = 0.001), grip strength (p < 0.0001), and knee extension strength (p < 0.05) but not FMI (p > 0.05) compared to other subjects. Grip and knee extension strength were 19 and 16 % weaker in OP women compared to others, respectively. The area under the receiver operating characteristic curve was 69 % for grip and 71 % for knee extension strength. In tissue proportions only LMI showed predictive power (63 %, p = 0.016). An overall linear association of LMI (R² = 0.007, p = 0.01) and FMI (R² = 0.028, p < 0.001) with FN BMD remained significant. In the multivariate model, after adjusting for age, grip strength, leg extension strength, FMI, LMI, number of medications, alcohol consumption, current smoking, dietary calcium intake, and hormone therapy, grip strength (adjusted OR = 0.899, 95 % CI 0.84-0.97, p < 0.01), leg extension strength (OR = 0.998, 95 % CI 0.99-1, p < 0.05), and years of hormone therapy (OR = 0.905, 95 % CI 0.82-1, p < 0.05) remained as significant determinants of OP. Muscle strength tests, especially grip strength, serve as an independent and useful tool for postmenopausal OP risk assessment. In addition, lean mass contributes to OP in this age group. Muscle strength and lean mass should be considered separately since both are independently associated with postmenopausal BMD.

Relationship between bone mineral density changes with denosumab treatment and risk reduction for vertebral and nonvertebral fractures

Dual-energy X-ray absorptiometric bone mineral density (DXA BMD) is a strong predictor of fracture risk in untreated patients. However, previous patient-level studies suggest that BMD changes explain little of the fracture risk reduction observed with osteoporosis treatment. We investigated the relevance of DXA BMD changes as a predictor for fracture risk reduction using data from the FREEDOM trial, which randomly assigned placebo or denosumab 60 mg every 6 months to 7808 women aged 60 to 90 years with a spine or total hip BMD T-score < -2.5 and not < -4.0. We took a standard approach to estimate the percent of treatment effect explained using percent changes in BMD at a single visit (months 12, 24, or 36). We also applied a novel approach using estimated percent changes in BMD from baseline at the time of fracture occurrence (time-dependent models). Denosumab significantly increased total hip BMD by 3.2%, 4.4%, and 5.0% at 12, 24, and 36 months, respectively. Denosumab decreased the risk of new vertebral fractures by 68% (p < 0.0001) and nonvertebral fracture by 20% (p = 0.01) over 36 months. Regardless of the method used, the change in total hip BMD explained a considerable proportion of the effect of denosumab in reducing new or worsening vertebral fracture risk (35% [95% confidence interval (CI): 20%-61%] and 51% [95% CI: 39%-66%] accounted for by percent change at month 36 and change in time-dependent BMD, respectively) and explained a considerable amount of the reduction in nonvertebral fracture risk (87% [95% CI: 35% - >100%] and 72% [95% CI: 24% - >100%], respectively). Previous patient-level studies may have underestimated the strength of the relationship between BMD change and the effect of treatment on fracture risk or this relationship may be unique to denosumab.

New laboratory tools in the assessment of bone quality

Bone quality is a complex set of intricated and interdependent factors that influence bone strength. A number of methods have emerged to measure bone quality, taking into account the organic or the mineral phase of the bone matrix, in the laboratory. Bone quality is a complex set of different factors that are interdependent. The bone matrix organization can be described at five different levels of anatomical organization: nature (organic and mineral), texture (woven or lamellar), structure (osteons in the cortices and arch-like packets in trabecular bone), microarchitecture, and macroarchitecture. Any change in one of these levels can alter bone quality. An altered bone remodeling can affect bone quality by influencing one or more of these factors. We have reviewed here the main methods that can be used in the laboratory to explore bone quality on bone samples. Bone remodeling can be evaluated by histomorphometry; microarchitecture is explored in 2D on histological sections and in 3D by microCT or synchrotron. Microradiography and scanning electron microscopy in the backscattered electron mode can measure the mineral distribution; Raman and Fourier-transformed infra-red spectroscopy and imaging can simultaneously explore the organic and mineral phase of the matrix on multispectral images; scanning acoustic microscopy and nanoindentation provide biomechanical information on individual trabeculae. Finally, some histological methods (polarization, surface staining, fluorescence, osteocyte staining) may also be of interest in the understanding of quality as a component of bone fragility. A growing number of laboratory techniques are now available. Some of them have been described many years ago and can find a new youth; others having benefited from improvements in physical and computer techniques are now available.

Effects of risedronate in Runx2 overexpressing mice, an animal model for evaluation of treatment effects on bone quality and fractures

Young mice overexpressing Runx2 specifically in cells of the osteoblastic lineage failed to gain bone mass and exhibited a dramatic increase in bone resorption, leading to severe osteopenia and spontaneous vertebral fractures. The objective of the current study was to determine whether treatment with a bisphosphonate (risedronate, Ris), which reduces fractures in postmenopausal as well as in juvenile osteoporosis, was able to improve bone quality and reduce vertebral fractures in mice overexpressing Runx2. Four-week-old female Runx2 mice received Ris at 2 and 10 μg/kg subcutaneously twice a week for 12 weeks. Runx2 and wild-type mice received vehicle (Veh) as control. We measured the number of new fractures by X-ray and bone mineral density (BMD) by DEXA. We evaluated bone quality by histomorphometry, micro-CT, and Fourier transform infrared imaging (FTIRI). Ris at 20 μg/kg weekly significantly reduced the average number of new vertebral fractures compared to controls. This was accompanied by significantly increased BMD, increased trabecular bone volume, and reduced bone remodeling (seen in indices of bone resorption and formation) in the vertebrae and femoral metaphysis compared to Runx2 Veh. At the femur, Ris also increased cortical thickness. Changes in collagen cross-linking seen on FTIRI confirmed that Runx2 mice have accelerated bone turnover and showed that Ris affects the collagen cross-link ratio at both forming and resorbing sites. In conclusion, young mice overexpressing Runx2 have high bone turnover-induced osteopenia and spontaneous fractures. Ris at 20 μg/kg weekly induced an increase in bone mass, changes in bone microarchitecture, and decreased vertebral fractures.

Effects of intravenous zoledronic acid plus subcutaneous teriparatide [rhPTH(1-34)] in postmenopausal osteoporosis

Clinical data suggest concomitant therapy with bisphosphonates and parathyroid hormone (PTH) may blunt the anabolic effect of PTH; rodent models suggest that infrequently administered bisphosphonates may interact differently. To evaluate the effects of combination therapy with an intravenous infusion of zoledronic acid 5 mg and daily subcutaneous recombinant human (rh)PTH(1-34) (teriparatide) 20 µg versus either agent alone on bone mineral density (BMD) and bone turnover markers, we conducted a 1-year multicenter, multinational, randomized, partial double-blinded, controlled trial. 412 postmenopausal women with osteoporosis (mean age 65 ± 9 years) were randomized to a single infusion of zoledronic acid 5 mg plus daily subcutaneous teriparatide 20 µg (n = 137), zoledronic acid alone (n = 137), or teriparatide alone (n = 138). The primary endpoint was percentage increase in lumbar spine BMD (assessed by dual-energy X-ray absorptiometry [DXA]) at 52 weeks versus baseline. Secondary endpoints included change in BMD at the spine at earlier time points and at the total hip, trochanter, and femoral neck at all time points. At week 52, lumbar spine BMD had increased 7.5%, 7.0%, and 4.4% in the combination, teriparatide, and zoledronic acid groups, respectively (p < .001 for combination and teriparatide versus zoledronic acid). In the combination group, spine BMD increased more rapidly than with either agent alone (p < .001 versus both teriparatide and zoledronic acid at 13 and 26 weeks). Combination therapy increased total-hip BMD more than teriparatide alone at all times (all p < .01) and more than zoledronic acid at 13 weeks (p < .05), with final 52-week increments of 2.3%, 1.1%, and 2.2% in the combination, teriparatide, and zoledronic acid groups, respectively. With combination therapy, bone formation (assessed by serum N-terminal propeptide of type I collagen [PINP]) increased from 0 to 4 weeks, declined minimally from 4 to 8 weeks, and then rose throughout the trial, with levels above baseline from 6 to 12 months. Bone resorption (assessed by serum β-C-telopeptide of type I collagen [β-CTX]) was markedly reduced with combination therapy from 0 to 8 weeks (a reduction of similar magnitude to that seen with zoledronic acid alone), followed by a gradual increase after week 8, with levels remaining above baseline for the latter half of the year. Levels for both markers were significantly lower with combination therapy versus teriparatide alone (p < .002). Limitations of the study included its short duration, lack of endpoints beyond DXA-based BMD (e.g., quantitative computed tomography and finite-element modeling for bone strength), lack of teriparatide placebo, and insufficient power for fracture outcomes. We conclude that while teriparatide increases spine BMD more than zoledronic acid and zoledronic acid increases hip BMD more than teriparatide, combination therapy provides the largest, most rapid increments when both spine and hip sites are considered.

Use of strontium as a treatment method for osteoporosis

Given its increasing incidence and serious complications, osteoporosis requires safe and effective long-term treatment. Strontium ranelate (SR), a new anti-osteoporotic treatment with a unique mode of action, has been investigated in the SOTI (Spinal Osteoporosis Therapeutic Intervention) and the TROPOS (Treatment of Peripheral Osteoporosis) trials, two major 3-year multinational placebo-controlled phase 3 randomized clinical trials. Unlike antiresorptive agents, SR produced steady and significant bone mineral density increases that correlated directly with decreases in vertebral and hip fracture risk. The safety profile of SR was almost similar to placebo in both trials. A slight but significant increased risk of thromboembolism events was noted from the pooled phase 3 studies data. However, this increased was not found in a large retrospective observational study. Thus, SR demonstrates broad spectrum safety and efficacy in reducing the risks of both vertebral and nonvertebral (including hip) fractures in a wide variety of patients, and should be considered as a first-line option to treat women at risk of osteoporotic fractures, whatever their age, the severity of the disease, and their risk factors.

Treatment of Postmenopausal Osteoporosis: Focus on Strontium Ranelate

Given its increasing incidence and serious complications, osteoporosis requires safe and effective long-term treatment. Strontium ranelate (SR), a new anti-osteoporotic treatment with a unique mode of action, has been investigated in the Spinal Osteoporosis Therapeutic Intervention (SOTI) and the Treatment Of Peripheral OSteoporosis (TROPOS) trials, two major 3-year multinational placebo-controlled Phase III randomized clinical trials. In SOTI, SR treatment reduced the risk of vertebral fracture by 41% (20.9% vs. 32.8%, P < 0.001); in TROPOS, it reduced the risk of non-vertebral fracture by 16% (11.2% vs. 12.9%, P = 0.04), and the risk of hip fracture in patients at high risk by 36% (4.3% vs. 6.4%, P = 0.046). Also SR has been shown to decrease the risk of vertebral fracture after 4 years of treatment and the risk of nonvertebral fracture after 5 years. Also it demonstrated for high risk patients a significant decrease of the risk of hip fractures (–43%) after 5 years of treatment. Unlike antiresorptive agents, SR produced steady and significant BMD increases that correlated directly with decreases in vertebral and hip fracture risk. Preplanned analysis of the pooled dataset from SOTI and TROPOS showed that SR was effective whether or not patients had key risk factors for fractures at baseline. SR was also effective in patients with osteopenia and younger postmenopausal patients aged 50–65 years. It was also effective for preventing both vertebral and nonvertebral fractures in the elderly (>80 years). Also, SR significantly attenuated height loss and decreased back pain. Finally long-term follow-up showed that BMD gains were maintained through a 8 year-period with maintaining the incidence of fracture between the first 3 years and the last 3 years of treatment. The safety profile of SR was almost similar to placebo in both trials. A slight but significant increased risk of thromboembolism events was noted from the pooled phase III studies data. However this increased was not found in a large retrospective observational study. Thus, SR demonstrates broad spectrum safety and efficacy in reducing the risks of both vertebral and non-vertebral (including hip) fractures in a wide variety of patients, and should be considered as a first-line option to treat women at risk of osteoporotic fractures, whatever their age, the severity of the disease, and their risk factors.

Pharmacogenetics of osteoporosis-related bone fractures: moving towards the harmonization and validation of polymorphism diagnostic tools

Osteoporosis is one of the most common skeletal chronic conditions in developed countries, hip fracture being one of its major healthcare outcomes. There is considerable variation in the implementation of current pharmacological treatment and prevention, despite consistent recommendations and guidelines. Many studies have reported conflicting findings of genetic associations with bone density and turnover that might predict fracture risk. Moreover, it is not clear whether genetic differences exist in relation to the morbidity and efficiency of the pharmacotherapy treatments. Clinical response, including beneficial and adverse events associated with osteoporosis treatments, is highly variable among individuals. In this context, the present article intends to summarize putative candidate genes and genome-wide association studies that have been related with BMD and fracture risk, and to draw the attention to the need for pharmacogenetic methodology that could be applicable in clinical translational research after an adequate validation process. This article mainly compiles analysis of important polymorphisms in osteoporosis documented previously, and it describes the simple molecular biology tools for routine genotype acquisition. Validation of methods for the easy, fast and accessible identification of SNPs is necessary for evolving pharmacogenetic diagnostic tools in order to contribute to the discovery of clinically relevant genetic variation with an impact on osteoporosis and its personalized treatment.

Monitoring pharmacological therapy for osteoporosis

Osteoporosis is a common disease characterized by low bone strength that increases the risk of fractures. The consequences of fractures include increases in morbidity, mortality, and healthcare costs. Randomized clinical trials have shown that pharmacological therapy can reduce the risk of fractures. In clinical practice, however, failure to achieve optimal therapeutic benefit is common for reasons that include taking medication incorrectly, stopping it prematurely, malabsorption, and the presence of unrecognized diseases or conditions with adverse skeletal effects. Monitoring for anti-fracture effectiveness in individual patients is limited by the absence of clinical tools to directly measure bone strength. It is therefore necessary to monitor therapy with biomarkers such as bone mineral density and bone turnover markers. This is a review of the utility of these tools in the care of individual patients.

Increases in hip and spine bone mineral density are predictive for vertebral antifracture efficacy with ibandronate

The relationship between bisphosphonate-induced bone mineral density (BMD) gains and antifracture efficacy remains to be fully elucidated. Data from two antifracture studies were analyzed. Postmenopausal osteoporotic women received oral (2.5 mg daily, 20 mg intermittent) or intravenous (0.5 mg, 1 mg quarterly) ibandronate. Outcome measures included moving averages plots and logistic regression analyses of the relationship between BMD change and vertebral fracture rate. In moving averages plots, ibandronate-induced BMD gains were consistently associated with decreased fracture rates. In the oral study, total-hip BMD increases at years 2 and 3 and lumbar spine BMD increases at year 3 were associated with 3-year vertebral fracture rate (relative risk reduction [RRR] at year 3 for 1% change from baseline: hip, 7.9% [95% CI 2.1-13.5%, P = 0.0084]; lumbar spine, 4.7% [-0.1% to 9.3%, P = 0.0565]). In the intravenous study, total-hip BMD increases at years 1, 2, and 3 and lumbar spine BMD increases at years 2 and 3 were significantly associated with vertebral fracture rate (RRR at year 3 for 1% change from baseline: hip, 11.6% [7.0-16.0%, P < 0.0001]; lumbar spine, 6.9% [2.9-10.6%, P = 0.0008]). In a pooled analysis, changes in total-hip and lumbar spine BMD were associated with 3-year vertebral fracture risk reduction and explained a substantial proportion of the antifracture effect (23-37% at 2 and 3 years). This analysis suggests that ibandronate-induced BMD gain in postmenopausal osteoporotic women is associated with vertebral fracture risk reduction.

Relationship between 3-month changes in biochemical markers of bone remodelling and changes in bone mineral density and fracture incidence in patients treated with strontium ranelate for 3 years

SUMMARY

From two randomised controlled trials, it is shown that 3-month changes in biochemical markers of bone formation (bone-specific alkaline phosphatase and C-terminal propeptide of type I procollagen) were associated with 3-year bone mineral density (BMD) changes, but not fracture incidence in patients treated with strontium ranelate.

INTRODUCTION

The purpose of this study was to assess if short-term change in biochemical markers of bone remodelling is associated with long-term BMD change and fracture incidence observed during treatment with strontium ranelate.

METHODS

From the SOTI and TROPOS trials, bone-specific alkaline phosphatase (BALP), C-terminal propeptide of type I procollagen (PICP), serum C-terminal telopeptides (S-CTX) and urine N-terminal telopeptides of type I collagen (U-NTX) were assessed at baseline and after 3 months.

RESULTS

Two thousand three hundred seventy-three women were included in this study. Multiple regression analysis showed that 3-month changes in PICP and BALP but not s-CTX I nor s-NTX I were significantly (p < 0.001) associated with 3-year BMD changes at the lumbar spine and the femoral neck. Changes in s-CTX I, PICP and BALP were significantly associated with change in total proximal femur BMD. Changes in biochemical markers explain less than 8% of the BMD changes. The 3-month changes in BALP, PICP s-CTX I and s-NTX I were not significantly associated with fracture incidence.

CONCLUSIONS

Short-term changes in biochemical markers of bone formation are associated with future BMD changes in patients treated with strontium ranelate, suggesting a bone-forming activity of this treatment, but are not appropriate to monitor the efficacy of strontium ranelate at the individual level.

Raloxifene ameliorates detrimental enzymatic and nonenzymatic collagen cross-links and bone strength in rabbits with hyperhomocysteinemia

We demonstrate a reduction in enzymatic divalent immature and trivalent pyridinium cross-links and an increase in the nonenzymatic cross-link, pentosidine (Pen), in rabbits with methionine (Met)-induced hyperhomocysteinemia. Such detrimental cross-link formation in bone was ameliorated by raloxifene (RLX) treatment.

INTRODUCTION

Collagen cross-links are determinants of bone quality. Homocysteine (Hcys) interferes with collagen cross-linking. Because RLX is thought to ameliorate bone quality, we investigated whether RLX ameliorated hyperhomocysteinemia-induced cross-link abnormalities using a Met-rich diet rabbit model.

METHODS

We divided New Zealand white rabbits into six groups (n = 6 per group): baseline control, sham operation, sham + 1% Met diet, ovariectomy (OVX), 1% Met diet + OVX, OVX + RLX (10 mg/kg/day), and 1% Met diet + OVX + RLX. RLX was administered for 16 weeks. We measured the amount of enzymatic immature and mature pyridinium cross-links and the nonenzymatic cross-link, Pen, and correlated the cross-link content to bone strength.

RESULTS

Hcys levels were significantly higher in the Met diet groups than in the normal diet groups. Met-fed rabbits with or without OVX showed a significant reduction of enzymatic cross-links, whereas an increase in Pen was observed in Met-fed rabbits with OVX. The cross-link content of the RLX-treated Met-fed rabbits with OVX was restored to similar levels as the sham group, accompanied by an improvement of bone strength.

CONCLUSION

These results demonstrate that hyperhomocysteinemia reduced bone strength via a reduction of enzymatic cross-links and an increase of nonenzymatic cross-links. RLX may ameliorate hyperhomocysteinemia-induced detrimental cross-linking in rabbits with OVX and may improve bone strength via the amelioration of collagen cross-links.

Treating osteoporosis in Canada: what clinical efficacy data should be considered by policy decision makers?

SAUMMARY: Using a Markov state-transition model, we estimated fractures averted with risedronate using two different types of clinical efficacy data. Summary data, as opposed to individual patient data (IPD), underestimated the number of fractures averted when applied in a specified high risk population. The choice of clinical efficacy data is an important consideration in health economic models evaluating osteoporosis therapies.

INTRODUCTION

This paper contrasts fracture reduction estimates for risedronate utilizing efficacy data from two approaches to meta-analysis: summary data versus individual patient data. We also examined differences in fracture reduction explained by varied cohort selection, especially the inclusion of low- versus high-risk populations.

METHODS

Using a Markov state-transition model, we compared fractures averted over 3 years in a hypothetical cohort by inputting fracture risk reduction estimates (risedronate versus placebo) from two data sources (summary data versus IPD). The cohort consisted of 100,000 Canadian women, age > or =65 years with osteoporosis (WHO criteria T-score < or = -2.5) and prevalent morphometric vertebral fracture.

RESULTS

Non-vertebral fractures averted with risedronate were: 3,571 and 6,584 per 100,000 women for summary data and IPD, respectively. For vertebral fractures, the numbers were 8,552 and 10,127. When IPD versus summary data was used, an additional 3,013 more non-vertebral fractures and 1,575 vertebral fractures were averted.

DISCUSSION

Relative risk estimates from IPD analyses were the best choice for modelling fracture outcomes when applied in a specified high-risk population. In addition to superior statistical methodology, they utilized RCT cohorts that are more representative of higher risk patients requiring treatment (osteoporotic women > or =65 years with a prevalent vertebral fracture).

Monitoring strontium ranelate therapy in patients with osteoporosis

PURPOSE

The purpose of this study was to review the monitoring of strontium ranelate osteoporosis therapy.

METHODS

The method used in this study was comprehensive literature review with clinical perspectives.

RESULTS

Changes in bone turnover markers (BTM) or bone mineral density (BMD) have been documented in osteoporosis clinical trials. However, neither BMD nor BTM changes fully explain the observed fracture risk reduction in treated patients. If changes in BMD or BTM on therapy would be easily discernable in individual patients, and were strongly associated with fracture risk reduction, monitoring individuals would be more useful. BMD changes in patients on strontium ranelate are of a greater magnitude and hence can be easily determined in an individual patient. In addition, there exists a better correlation between fracture risk reduction and increases in BMD.

CONCLUSIONS

The strong correlation between measured BMD increases and fracture risk reduction in patients on strontium ranelate therapy will be of clinical benefit to physicians wishing to evaluate both treatment persistence and fracture risk reduction.

Reanalysis precision of 3D quantitative computed tomography (QCT) of the spine

PURPOSE

To evaluate the precision of 3D QCT of the spine.

METHODS

Interoperator analysis reproducibility of two different 3D QCT analysis systems (QCTPro from Mindways Software Inc and MIAF-Spine from the Institute of Medical Physics, University of Erlangen) was evaluated in 29 postmenopausal women. For each analysis system four different trained operators analyzed all scans independently. Results of the vertebrae L1 and L2 were averaged. With QCTPro BMD of the central trabecular elliptical VOI was analyzed. With MIAF-Spine integral, trabecular and cortical BMD, BMC and volume were analyzed in the total vertebral body, the elliptical cylinder and the Osteo VOIs that were further subdivided into superior, mid and inferior subVOIs, each.

RESULTS

Precision errors (%CVrms) for the central trabecular VOI that is also used in the traditional single slice QCT techniques were 1.7+/-2.2% and 0.6+/-0.6% for QCTPro and MIAF-Spine, respectively. For MIAF-Spine integral BMD precision errors were lowest in the total and mid Osteo subVOIs (0.5+/-0.5%). Trabecular BMD precision errors were lowest in the mid subVOIs (0.6+/-0.6%). For trabecular BMD there were no differences among the total vertebral body, elliptical cylinder and Osteo VOIs. Cortical BMD precision errors were lowest in the mid total vertebral body subVOI (2.1+/-1.9%) and slightly higher in the mid of the Osteo subVOI. Precision errors in the superior and inferior subVOIs were typically 50% to 100% higher compared to the mid subVOIs.

DISCUSSION

Compared to QCTPro MIAF-Spine uses an automated 3D segmentation and an anatomic vertebral coordinate system to position a variety of analysis VOIs. This results in better precision than the more manually assisted analysis used by QCTPro. In-vivo precision errors will be approximately 0.5% higher compared to the analysis precision errors reported here (13). The results demonstrate that with 3D QCT in-vivo precision errors of about 1%-1.5% for trabecular and 2.5% to 3% for cortical bone can be obtained in postmenopausal women.

Ibandronate dose response is associated with increases in bone mineral density and reductions in clinical fractures: results of a meta-analysis

This meta-analysis pooled data from the four phase III clinical trials of ibandronate to assess the relationship between ibandronate dose, changes in bone mineral density, and rates of both clinical and non-vertebral fractures. Individual patient data from the intent-to-treat population of the BONE, IV fracture prevention, MOBILE, and DIVA studies were included for analysis. The relationship between ibandronate dose and bone mineral density at both the lumbar spine and at the total hip was assessed qualitatively. The relationship between lumbar spine bone mineral density and clinical fracture rate, and the relationship between total hip bone mineral density and non-vertebral fracture rate, were assessed both qualitatively and using mathematical models. A total of 8710 patients were included in this analysis. Both lumbar spine and total hip bone mineral density were observed to increase with increasing ibandronate dose. The incidence of all clinical fractures was observed to decrease as lumbar spine bone mineral density increased. A statistically significant inverse linear relationship was observed between percent change in lumbar spine bone mineral density and the rate of clinical fractures (P=0.005). A non-significant curvilinear relationship was observed between percent change in total hip bone mineral density and non-vertebral fracture rate. Increased ibandronate exposure is associated with increasing gains in the lumbar spine bone mineral density and decreasing clinical fracture rates. A non-linear relationship may exist between increases in the total hip bone mineral density and non-vertebral fracture rate.

Biochemical markers of bone turnover: potential use in the investigation and management of postmenopausal osteoporosis

INTRODUCTION

The aim was to analyse data on the use of biochemical bone turnover markers (BTM) in postmenopausal osteoporosis.

METHODS

We carried out a comparative analysis of the most important papers concerning BTM in postmenopausal osteoporosis that have been published recently.

RESULTS

The BTM levels are influenced by several factors. They are moderately correlated with BMD and subsequent bone loss. Increased levels of bone resorption markers are associated with a higher risk of fracture. Changes in the BTM during the anti-osteoporotic treatment (including combination therapy) reflect the mechanisms of action of the drugs and help to establish their effective doses. Changes in the BTM during the anti-resorptive treatment are correlated with their anti-fracture efficacy.

CONCLUSION

Biological samples should be obtained in a standardised way. BTM cannot be used for prediction of the accelerated bone loss at the level of the individual. BTM help to detect postmenopausal women who are at high risk of fracture; however, adequate practical guidelines are lacking. BTM measurements taken during the anti-resorptive therapy help to identify non-compliers. They may improve adherence to the anti-resorptive therapy and the fall in the BTM levels that exceeds the predefined threshold improves patients' persistence with the treatment. There are no guidelines concerning the use of BTM in monitoring anti-osteoporotic therapy in postmenopausal women.

Pharmacogenetics of osteoporosis and the prospect of individualized prognosis and individualized therapy

PURPOSE OF REVIEW

Description of recent progress in genetics and pharmacogenetics of osteoporosis.

RECENT FINDINGS

Osteoporosis and its consequence of fragility fracture are characterized by highly complex phenotypes, which include bone mineral density, bone strength, bone turnover markers, and nonskeletal traits. Recent developments in the genome-wide studies using high-throughput single-nucleotide polymorphisms have yielded reliable findings. Four genome-wide studies have identified 40 single-nucleotide polymorphisms in various chromosomes that were modestly associated with either bone mineral density or fracture risk. Clinical response, including adverse reactions, to antiosteoporosis therapy (such as bisphosphonates and selective estrogen receptor modulators) is highly variable among treated individuals. Candidate gene studies have found that common polymorphic variations within the collagen I alpha 1 and vitamin D receptor genes were associated with variability in response to antiosteoporosis treatment. Moreover, a recent genome-wide study identified four single-nucleotide polymorphisms that were associated with bisphosphonate-related osteonecrosis of the jaw with relative risk being between 10 and 13.

SUMMARY

The evaluation of osteoporosis and fracture risk is moving from a risk stratification approach to a more individualized approach, in which an individual's absolute risk of fracture is evaluable as a constellation of the individual's environmental exposure and genetic makeup. Therefore, the identification of gene variants that are associated with osteoporosis phenotypes or response to therapy can eventually help individualize the prognosis, treatment and prevention of fracture and its adverse outcomes.

Bone mass and architecture determination: state of the art

Bone fracture occurs when the bone strength (i.e. the ability of the bone to resist a force) is less than the force applied to the bone. In the elderly, falls represent the more severe forces applied to bone. Bone density is a good marker of bone strength, and has been used widely in this respect. Nevertheless, many aspects of bone strength cannot be explained by bone density alone. For this reason there has been increasing interest in studying architectural parameters of bone, beyond bone density, which may affect bone strength. Macro-architectural parameters include e.g. bone size and geometry assessed with techniques such as radiography, dual-energy x-ray absorptiometry (DXA), peripheral quantitative computed tomography (QCT), computed tomography (CT) and magnetic resonance imaging (MRI). Micro-architectural parameters include fine cortical and trabecular structural detail which can be evaluated using high-resolution imaging techniques such as multidetector CT, MRI, and high-resolution peripheral QCT. These techniques are providing a great deal of new information on the physiological architectural responses of bone to aging, weightlessness, and treatment. This will ultimately lead to the prediction of fracture risk being improved through a combined assessment of bone density and architectural parameters.

Bisphosphonates: how do they work?

Bisphosphonates (BPs) are taken up preferentially by the skeleton and decrease osteoclast-mediated bone resorption. The capacity of the skeleton to retain BPs is large, and there is no indication for saturation of binding sites with the doses used in osteoporosis. The anti-resorptive action of BPs includes their selective binding to calcium crystals and their subsequent release and uptake by the osteoclasts. There are differences in the affinities of PBs for bone as well as in their anti-resorptive potencies, and the whole molecule is responsible for their inhibitory effect on bone resorption. At the tissue level, they decrease the rate of bone resorption and turnover, increase bone mineral density, and maintain or improve structural and material properties of bone and thereby reduce the risk of fractures. Current studies address questions related primarily to the pharmacological properties of these compounds that are essential for their optimal clinical use, such as for example long-term safety and efficacy.

Chronic kidney disease and bone fracture: a growing concern

Susceptibility to fracture is increased across the spectrum of chronic kidney disease (CKD). Moreover, fracture in patients with end-stage kidney disease (ESKD) results in significant excess mortality. The incidence and prevalence of CKD and ESKD are predicted to increase markedly over the coming decades in conjunction with the aging of the population. Given the high prevalence of both osteoporosis and CKD in older adults, it is of the utmost public health relevance to be able to assess fracture risk in this population. Dual-energy X-ray absorptiometry (DXA), which provides an areal measurement of bone mineral density (aBMD), is the clinical standard to predict fracture in individuals with postmenopausal or age-related osteoporosis. Unfortunately, DXA does not discriminate fracture status in patients with ESKD. This may be, in part, because excess parathyroid hormone (PTH) secretion may accompany declining kidney function. Chronic exposure to high PTH levels preferentially causes cortical bone loss, which may be partially offset by periosteal expansion. DXA can neither reliably detect changes in bone volume nor distinguish between trabecular and cortical bone. In addition, DXA measurements may be low, normal, or high in each of the major forms of renal osteodystrophy (ROD). Moreover, postmenopausal or age-related osteoporosis may also affect patients with CKD and ESKD. Currently, transiliac crest bone biopsy is the gold standard to diagnose ROD and osteoporosis in patients with significant kidney dysfunction. However, bone biopsy is an invasive procedure that requires time-consuming analyses. Therefore, there is great interest in developing non-invasive high-resolution imaging techniques that can improve fracture risk prediction for patients with CKD. In this paper, we review studies of fracture risk in the setting of ESKD and CKD, the pathophysiology of increased fracture risk in patients with kidney dysfunction, the utility of various imaging modalities in predicting fracture across the spectrum of CKD, and studies evaluating the use of bisphosphonates in patients with CKD.

Considerations for development of surrogate endpoints for antifracture efficacy of new treatments in osteoporosis: a perspective

Because of the broad availability of efficacious osteoporosis therapies, conduct of placebo-controlled trials in subjects at high risk for fracture is becoming increasing difficult. Alternative trial designs include placebo-controlled trials in patients at low risk for fracture or active comparator studies, both of which would require enormous sample sizes and associated financial resources. Another more attractive alternative is to develop and validate surrogate endpoints for fracture. In this perspective, we review the concept of surrogate endpoints as it has been developed in other fields of medicine and discuss how it could be applied in clinical trials of osteoporosis. We outline a stepwise approach and possible study designs to qualify a biomarker as a surrogate endpoint in osteoporosis and review the existing data for several potential surrogate endpoints to assess their success in meeting the proposed criteria. Finally, we suggest a research agenda needed to advance the development of biomarkers as surrogate endpoints for fracture in osteoporosis trials. To ensure optimal development and best use of biomarkers to accelerate drug development, continuous dialog among the health professionals, industry, and regulators is of paramount importance.

Effects of denosumab on the geometry of the proximal femur in postmenopausal women in comparison with alendronate

Denosumab is a fully human monoclonal antibody against receptor activator of nuclear factor-kappaB ligand, an essential mediator of osteoclast activity and survival. In postmenopausal women with low bone mineral density (BMD), subcutaneous denosumab decreases bone resorption and increases BMD. This post hoc analysis reports on subjects treated for up to 24 months with denosumab 60mg 6 monthly (N=39), placebo (N=39), or open-label alendronate 70mg once weekly (N=38) in a phase 2 study. Hip scans were done by dual-energy X-ray absorptiometry at baseline, 12, and 24 months; these were analyzed with hip structural analysis software to evaluate BMD and cross-sectional geometry parameters at the narrowest segment of the femoral neck, the intertrochanter, and the proximal shaft. Geometric parameters and derived strength indices included bone cross-sectional area, section modulus, and buckling ratio. At 12 and 24 months denosumab and alendronate improved these parameters compared with placebo. Denosumab effects were greater than alendronate at the intertrochanteric and shaft sites. The magnitude and direction of the changes in structural geometry parameters observed in this study suggest that denosumab treatment may lead to improved bone mechanical properties. Ongoing phase 3 studies will determine whether denosumab reduces fracture risk.

How can bone turnover modify bone strength independent of bone mass?

The amount of bone turnover in the skeleton has been identified as a predictor of fracture risk independent of areal bone mineral density (aBMD) and is increasingly cited as an explanation for discrepancies between areal bone mineral density and fracture risk. A number of mechanisms have been proposed to explain how bone turnover influences bone biomechanics, including regulation of tissue degree of mineralization, the disconnection or fenestration of individual trabeculae by remodeling cavities, and the ability of cavities formed during the remodeling process to act as stress risers. While these mechanisms can influence bone biomechanics, they also modify bone mass. If bone turnover is to explain any of the observed discrepancies between fracture risk and areal bone mineral density, however, it must not only modify bone strength, but must also modify bone strength in excess of what would be expected from the associated change in bone mass. This article summarizes biomechanical studies of how tissue mineralization, trabecular disconnection, and the presence of remodeling cavities might have an effect on cancellous bone strength independent of bone mass. Existing data support the idea that all of these factors may have a disproportionate effect on bone stiffness and/or strength, with the exception of average tissue degree of mineralization, which may not affect bone strength independent of aBMD. Disproportionate effects of mineral content on bone biomechanics may instead come from variation in tissue degree of mineralization at the micro-structural level. The biomechanical explanation for the relationship between bone turnover and fracture incidence remains to be determined, but must be examined not in terms of bone biomechanics, but in terms of bone biomechanics relative to bone mass.

European guidance for the diagnosis and management of osteoporosis in postmenopausal women

Guidance is provided in a European setting on the assessment and treatment of postmenopausal women with or at risk from osteoporosis.

INTRODUCTION

The European Foundation for Osteoporosis and Bone disease (subsequently the International Osteoporosis Foundation) published guidelines for the diagnosis and management of osteoporosis in 1997. This manuscript updates these in a European setting.

METHODS

The following areas are reviewed: the role of bone mineral density measurement for the diagnosis of osteoporosis and assessment of fracture risk; general and pharmacological management of osteoporosis; monitoring of treatment; assessment of fracture risk; case finding strategies; investigation of patients; health economics of treatment.

RESULTS AND CONCLUSIONS

A platform is provided on which specific guidelines can be developed for national use.