Vertebral fracture risk reduction with strontium ranelate in women with postmenopausal osteoporosis is independent of baseline risk factors

Vertebral anti-fracture efficacy of strontium ranelate according to pre-treatment bone turnover

Osteoporotic post-menopausal women patients in two randomised trials comparing the anti-fracture efficacy of strontium ranelate with placebo were separated into tertiles according to their baseline levels of biochemical markers of bone formation and resorption. The vertebral anti-fracture efficacy of strontium ranelate was shown to be independent of baseline bone turnover levels.

INTRODUCTION

Bone turnover (BTO) levels vary among women at risk of osteoporotic fracture. Strontium ranelate is an anti-osteoporotic treatment increasing bone formation and reducing bone resorption. It was hypothesised that its anti-fracture efficacy would be independent of baseline BTO levels.

METHODS

Post-menopausal women with osteoporosis from two pooled studies were stratified in tertiles according to baseline levels of two BTO markers: bone-specific alkaline phosphatase (b-ALP, n = 4995) and serum C-telopeptide cross-links (sCTX, n = 4891). Vertebral fracture risk was assessed over 3 years with strontium ranelate 2 g/day or placebo.

RESULTS

In the placebo group, relative risk of vertebral fractures increased with BTO tertiles by 32% and 24% for patients in the highest tertile for b-ALP and CTX, respectively, compared to those in the lowest tertile. In the strontium ranelate group, incidences of vertebral fracture did not differ significantly across BTO tertiles. Significant reductions in vertebral fractures with strontium ranelate were seen in all tertiles of both markers, with relative risk reductions of 31% to 47% relative to placebo. Risk reduction did not differ among tertiles (b-ALP: p = 0.513; sCTX: p = 0.290).

CONCLUSION

The vertebral anti-fracture efficacy of strontium ranelate was independent of baseline BTO levels. Strontium ranelate offers clinical benefits to women across a wide range of metabolic states.

The morphology and lattice structure of bone crystal after strontium treatment in goats

Strontium (Sr) compounds have become increasingly popular in osteoporosis treatment. As a bone seeking element, 98% of Sr deposits in bone and teeth after oral ingestion. However, the quality of new bone after Sr deposition is yet to be extensively investigated. In this study, eight osteopenic goats were divided into two groups: Ca + 40Sr (five goats) and controls (three goats). Controls were fed with low calcium feeds. Ca phosphate was supplied at 100 mg/(kg day), and Sr phosphate at 40 mg/(kg day) in the Ca + 40Sr group. The newly formed bone at the outer cortical area of the femur with Sr deposition was identified from tetracycline labels, and the morphology and lattice structure of the crystals in these regions were investigated. Results showed that Sr concentrations of bone tissue significantly increased 144.37% for Sr administration without significant change in Ca concentration, and the ingested Sr mainly deposited in new bone. The crystal isolated from new bone exhibited the typical character of biological apatite as determined by Fourier transform infrared spectroscopy and selected-area electron diffraction. Transmission electron microscopy examination showed that a crystal with width of 8-10 nm grew along with the (002) lattice and aligned with the same direction in both groups. The elemental analysis of crystals showed that the ingested Sr deposited mainly in the bone matrix or was absorbed on the bone crystal surface, while only a limited amount of Sr replaced Ca in apatite crystals. Our findings showed that Sr administration at current dosages for prevention and treatment of osteoporosis might not change the bone crystal morphology and structure.

Strontium ranelate enhances callus strength more than PTH 1-34 in an osteoporotic rat model of fracture healing

Treatment of an underlying disease is often initiated after the occurrence of an osteoporotic fracture. Our aim was to investigate whether teriparatide (PTH 1-34) and strontium ranelate affect fracture healing in ovariectomized (OVX) rats when provided for the first time after the occurrence of an osteoporotic fracture. We combined the model of an OVX rat with a closed diaphyseal fracture. Sixty Sprague Dawley rats were randomly assigned to four groups. Fracture healing in OVX rats after treatment with pharmacological doses of strontium ranelate and PTH 1-34 was compared with OVX and sham-treated control groups. After 28 days, the femur was excised and scanned by micro computed tomography and the callus evaluated, after which biomechanical torsional testing was performed and torque and toughness until reaching the yield point were analyzed. Only treatment with strontium ranelate led to a significant increase in callus resistance compared to the OVX control rats, whereas both PTH 1-34 and strontium ranelate increased the bone volume/tissue volume ratio of the callus. The PTH 1-34-increased trabecular bone volume within the callus was even higher compared to sham. As for the callus tissue volume, the increase induced by strontium ranelate was significant, contrary to the changes induced by PTH. Callus in strontium ranelate-treated animals is more resistant to torsion compared with OVX control rats. To our knowledge, this is the first report of the enhancement of fracture healing by strontium ranelate. Because both treatments enhance bone and tissue volume within the callus, there may be a qualitative difference between the calluses of PTH 1-34- and strontium ranelate-treated OVX rats. The superior results obtained with strontium ranelate compared to PTH in terms of callus resistance could be the consequence of a better quality of the new bone formed within the callus.

Long-term treatment of postmenopausal osteoporosis with strontium ranelate: results at 8 years

OBJECTIVES

Strontium ranelate 2 g/day has proven efficacy against vertebral and nonvertebral fracture over 5 years in postmenopausal osteoporosis, though many women require longer-term treatment. This article describes the efficacy, safety, and tolerability of this agent over 8 years.

METHODS

Postmenopausal osteoporotic women having participated in the 5-year efficacy trials SOTI and TROPOS were invited to enter a 3-year open-label extension study. The results presented here focus on patients who received strontium ranelate for 8 years.

RESULTS

At the extension baseline, the population treated for 8 years (n=879; 79.1+/-5.6 years) had femoral neck T-score of -2.61+/-0.71. The cumulative incidences of new vertebral and nonvertebral fractures (13.7% and 12.0%, respectively) over years 6 to 8 were non-statistically different from the cumulative incidences in the first 3 years of the original studies (11.5% and 9.6%). Lumbar spine, femoral neck, and total hip bone mineral density (BMD) increased throughout the 8-year period. Annual relative change in BMD was significant at every visit, except the 8-year visit for femoral neck and total hip BMD. Strontium ranelate was safe and well tolerated over 8 years.

CONCLUSIONS

Long-term treatment with strontium ranelate 2 g/day in postmenopausal osteoporotic women leads to continued increases in BMD at all sites. The data also provide some evidence for a sustained antifracture efficacy.

[Austrian guidance for the pharmacological treatment of osteoporosis in postmenopausal women--update 2009]

Osteoporosis is a systemic skeletal disease characterized by diminished bone mass and deterioration of bone microarchitecture, leading to increased fragility and subsequent increased fracture risk. Therapeutic measures therefore aim at reducing individual fracture risk. In Austria, the following drugs, all of which have been proven to reduce fracture risk, are currently registered for the treatment of postmenopausal osteoporosis: alendronate, risedronate, etidronate, ibandronate, raloxifene, teriparatide (1-34 PTH), 1-84 PTH, strontium ranelate and salmon calcitonin. Fluorides are still available, but their role in daily practice has become negligible. Currently, there is no evidence that a combination of two or more of these drugs could improve anti-fracture potency. However, treatment with PTH should be followed by the treatment with an anticatabolic drug such as bisphosphonates. Calcium and vitamin D constitute an important adjunct to any osteoporosis treatment.

Strontium ranelate: new data on fracture prevention and mechanisms of action

Osteoporosis treatments need to combine an unequivocally demonstrated reduction of fractures, at various skeletal sites, long-term safety, and a user-friendly profile that optimizes therapeutic adherence. Strontium ranelate is the first compound to simultaneously decrease bone resorption and stimulate bone formation. Its anti-fracture efficacy at various skeletal sites has been established for as long as 5 years through studies of the highest methodological standards. Increases in bone mineral density observed after 1 year of treatment are predictive of the long-term fracture efficacy, suggesting for the first time in osteoporosis that bone densitometry can be used as a monitoring tool. Due to a positive risk/benefit ratio, strontium ranelate is now considered as a first-line treatment in the management of osteoporosis.

New and emerging treatments for osteoporosis

A variety of new treatments for osteoporosis have become available within the last several years, and a number of emerging treatments remain in late clinical stage development. New and emerging treatments include more potent members, or more convenient formulations, of existing classes of therapy, but a number of the emerging treatments are first-generation compounds addressing specific therapeutic targets based on recent advances in understanding of basic bone biology. These new and emerging treatments include agents with anticatabolic effects, compounds with anabolic effects, and one agent possibly containing both anticatabolic and anabolic effects. The increasing variety of new and emerging treatments increases the possibility that effective therapy will be targeted to the specific needs of the individual patient.

Spinal deformity index (SDI) is a good predictor of incident vertebral fractures

The spinal deformity index is a convenient tool to quantify the number and the severity of prevalent vertebral fractures. It is a predictor of the risk of sustaining incident vertebral fracture. This quantification must be taken into account to improve management of patients.

INTRODUCTION

Prevalent fractures are strong risk factors for subsequent fractures.

METHODS

The study subjects were women from the placebo groups of two studies of strontium ranelate in postmenopausal osteoporosis (N = 723 and 637 patients, respectively). Three lateral radiographs of the spine were obtained at baseline and annually over 3 years, according to standardized procedures. The semiquantitative visual assessment of each vertebra from T4 to L4 was performed by the same reader throughout the study. A spinal deformity index (SDI) was calculated by summing for each patient the grade of each vertebra from T4 to L4.

RESULTS

There was a linear relationship between baseline SDI and the 3-year incidence of vertebral fracture (adjusted R(2) = 0.76). The 3-year incidence of vertebral fractures was different among the tertiles of baseline SDI: 17.3 +/- 3.6%, 25.4 +/- 2.6%, and 47.6 +/- 3.1% from the lowest to the highest, respectively. There was no relationship between SDI and non-vertebral fractures incidence.

CONCLUSION

SDI is a good predictor of incident vertebral fractures. Patients with highest SDI should receive highest priority to treatment.

Clinical assessment of fracture risk and novel therapeutic strategies to combat osteoporosis

OBJECTIVE

To review the latest tools in the clinical assessment of fracture risk and to review new and emerging options for osteoporosis therapy.

DESIGN

Retrospective analysis of published studies regarding the diagnosis and treatment of osteoporosis.

RESULT(S)

Large-scale epidemiologic data were recently assembled by the World Health Organization to produce a Web-based clinical assessment tool, FRAX, which uses clinical and historical data to provide prompt assessment and quantitation of fracture risk. The FRAX models were developed from studying population-based cohorts in Europe, North America, Asia, and Australia. The FRAX algorithms indicate the 10-year probability of hip fracture and the 10-year probability of a major osteoporotic fracture (at the clinical spine, forearm, hip, or shoulder) on which to base treatment decisions. Recent progress in the study of bone metabolism including anabolic pathways that enhance bone maintenance, is anticipated to improve the ways in which skeletal health can be maintained and osteoporosis can be treated.

CONCLUSION(S)

Using FRAX, fracture risk in now easily assessed in the clinical setting. New and emerging treatment strategies for bone maintenance are reviewed. Improved assessment of fracture risk, combined with tailored therapies for at-risk patients, will increase the number of patients who receive appropriate bone-sparing therapies.

Strontium-calcium coadministration stimulates bone matrix osteogenic factor expression and new bone formation in a large animal model

Strontium (Sr) has become increasingly attractive for use in the prevention and treatment of osteoporosis by concomitantly inhibiting bone resorption and enhancing bone formation. Strontium shares similar chemical, physical, and biological characteristics with calcium (Ca), which has been widely used as a dietary supplement in osteoporosis. However, the effects of Sr-Ca coadministration on bone growth and remodeling are yet to be extensively reported. In this study, 18 ovariectomized goats were divided into four groups: three groups of five goats each treated with 100 mg/kg/day Ca, Ca plus 24 mg/kg/day Sr (Ca + 24Sr), or Ca plus 40 mg/kg/day Sr (Ca + 40Sr), and three untreated goats fed low calcium feed. Serum Sr levels increased 6- and 10-fold in the Ca + 24Sr and Ca + 40Sr groups, respectively. Similarly, Sr in the bone increased four- and sixfold in these two groups. Sr-Ca coadministration considerably increased bone mineral apposition rate (MAR). The expression of insulin-like growth factor (IGF)-1 and runt-related transcription factor 2 (Runx2) was significantly upregulated within the Ca + 40Sr treatment group; tumor necrosis factor (TNF)-agr; expression was significantly downregulated in the Ca and Ca + 40Sr groups. The results indicate that Sr-Ca coadministration increases osteogenic gene expression and stimulates new bone formation.

New findings with old drugs for osteoporosis

BACKGROUND

Postmenopausal osteoporosis is common and is associated with stooped posture, loss of height, back pain and fractures.

OBJECTIVES/METHODS

This evaluation is of clinical outcome trials with tibolone (Long-Term Intervention of Fractures with Tibolone) and strontium ranelate (Spinal Osteoporosis Therapeutic Intervention) in postmenopausal osteoporosis.

RESULTS

Although the Long-Term Intervention of Fractures with Tibolone trial established that tibolone decreased the incidence of vertebral and non-vertebral fractures in postmenopausal osteoporosis, it also showed that tibolone caused a small increase in the incidence of stoke. The Spinal Osteoporosis Therapeutic Intervention trial established that strontium ranelate decreased the incidence of vertebral fractures, but had little effect on the incidence of non-vertebral fractures.

CONCLUSIONS

As some of the bisphosphonates (alendronate, risedronate, zoledronic acid) have been shown to prevent hip fractures without increasing the incidence of stroke, they should be preferred to tibolone and strontium in the treatment of postmenopausal osteoporosis.

Strontium ranelate: the first agent of a new therapeutic class in osteoporosis

Strontium ranelate is a new agent developed for the management of post-menopausal osteoporosis. It has a unique mode of action, based on an uncoupling between bone formation (increased) and bone resorption (decreased). To review its effectiveness we searched the MEDLINE database from 1985 to 2008, as well as databases such as the Cochrane controlled register, for citations or relevant articles. After this extensive search of the literature, a critical appraisal of the data was obtained through a consensus meeting (AN, MH, SS, OB, and J-YR). We found that strontium ranelate reduces vertebral, nonvertebral, major nonvertebral, and hip fractures over 1, 3, 4, and 5 years. Its spectrum of activity covers women with osteopenia, osteoporosis, and severe osteoporosis. Elderly subjects also show a reduction in vertebral and nonvertebral fractures. Bone mineral density may be used as a monitoring tool for strontium ranelate, since early changes are predictive of long-term fracture reduction. Biochemical markers of bone turnover reflect the uncoupling between resorption and formation. The safety profile of strontium ranelate compares favorably with the other currently marketed antiosteoporosis medications. Preliminary results suggest that strontium ranelate is able to reduce the progression of spine osteoarthritis. In conclusion, strontium ranelate has the potential to be a candidate for first-line treatment of osteopenia and osteoporosis. However, further research is needed before suggesting its widespread use in osteoarthritis.

Bone-forming agents in the management of osteoporosis

Women often consult for the first time after osteoporosis has already become established. Medications have therefore been developed which can stimulate bone formation, with the ultimate goal of restoring bone quantity and quality and reducing spinal and peripheral fractures to a greater extent than can be obtained with inhibitors of bone resorption. Peptides of the parathyroid hormone family, when given intermittently, increase the number and activity of osteoblasts, leading to an increase in bone mass and in an improvement in skeletal architecture. Teriparatide (1-34 parathyroid hormone, PTH) reduces vertebral and non-vertebral fractures at a dose of 20 microg/day given in subcutaneous daily injections. 1-84 PTH reduces vertebral fractures, but results on non-vertebral fractures are lacking. Strontium ranelate, suggested to uncouple bone formation from bone resorption, reduces vertebral, non-vertebral and hip fractures in osteoporotic patients aged >74 years. Reduction of a vertebral fracture has also been shown in osteopenic patients. Long-term (5-year) data are available on vertebral, non-vertebral, major non-vertebral and hip fractures in osteoporotic patients. Combination/sequential treatments using inhibitors of bone resorption and bone-forming agents have been assessed in a variety of regimens. Benefits from the use of bone-forming agents appear to be largely independent of previous treatment with inhibitors of bone resorption. After treatment with an anabolic agent, the use of anti-resorptive medications maintains the benefit of the former treatment. Concomitant use of an inhibitor of bone resorption and a stimulator of bone formation has not, so far, showed any additional benefit compared with each medication given alone.

Case finding for the management of osteoporosis with FRAX--assessment and intervention thresholds for the UK

Assessment and intervention thresholds are developed and proposed in men aged over 50 years and postmenopausal women for the UK based on fracture probability from the WHO fracture risk assessment tool (FRAX).

INTRODUCTION

The FRAX tool has recently become available to compute the 10-year probability of fractures in men and women from clinical risk factors (CRFs) with or without the measurement of femoral neck bone mineral density (BMD). The aim of this study was to develop a case-finding strategy for men and women from the UK at high risk of osteoporotic fracture by delineating the fracture probabilities at which BMD testing or intervention should be recommended.

METHODS

Fracture probabilities were computed using the FRAX tool calibrated to the epidemiology of fracture and death in the UK. The relationship between cost effectiveness and fracture probability used the source data from a prior publication that examined the cost effectiveness of generic alendronate in the UK. An intervention threshold was set by age in men and women, based on the fracture probability equivalent to that of women with a history of a prior osteoporosis related fracture. In addition, assessment thresholds for the use of BMD testing were explored. Assessment thresholds for the measurement of BMD followed current practice guidelines where individuals were considered to be eligible for assessment in the presence of one or more CRF. An upper assessment threshold (i.e. a fracture probability above which patients could be treated without recourse to BMD) was based on optimisation of the positive predictive value of the assessment tool. The consequences of assessment and intervention thresholds on the requirement for BMD test and interventions were assessed using the distribution of clinical risk factors and femoral neck BMD for women in the source cohorts used for the development of the FRAX models

RESULTS

Treatment was cost effective at all ages when the 10-year probability of a major fracture exceeded 7%. The intervention threshold at the age of 50 years corresponded to a 10-year probability of a major osteoporotic fracture of 7.5%. This rose progressively with age to 30% at the age of 80 years, so that intervention was cost effective at all ages. Assessment thresholds for testing with BMD (6-9% at the age of 50 years) also rose with age (18-36% at the age of 80 years). The use of these thresholds in a case-finding strategy would identify 6-20% of women as eligible for BMD testing and 23-46% as eligible for treatment, depending on age. The same threshold can be used in men.

CONCLUSION

The study provides a method of developing management algorithms for osteoporosis from the estimation of fracture probabilities, rather than those based on BMD alone or BMD with single or multiple CRFs.

Strontium ranelate does not stimulate bone formation in ovariectomized rats

INTRODUCTION

Strontium ranelate (SrR) is suggested to function as a dual-acting agent in the treatment of postmenopausal osteoporosis with anti-resorptive and anabolic skeletal benefits. We evaluated the effects of SrR on the skeleton in ovariectomized (OVX) rats and evaluated the influence of dietary calcium.

METHODS

Three-month old virgin female rats underwent ovariectomy (OVX, n = 50) or SHAM surgery (SHAM, n = 10). Four weeks post-surgery, rats were treated daily by oral gavage with distilled water (10 ml/kg/day) or SrR (25 or 150 mg/kg/day) for 90 days. Separate groups of animals for each dose of SrR were fed a low (0.1%) or normal (1.19%) calcium (Ca) diet. Static and dynamic histomorphometry, DXA, mu-CT, mechanical testing, and serum and skeletal concentrations of strontium were assessed.

RESULTS

SrR at doses of 25 and 150 mg/kg/day did not increase bone formation on trabecular or periosteal bone surfaces, and failed to inhibit bone resorption of trabecular bone regardless of Ca intake. There were no improvements in bone mass, volume or strength with either dose of SrR given normal Ca.

CONCLUSION

These findings demonstrate that SrR at dosages of 25 and 150 mg/kg/day did not stimulate an anabolic bone response, and failed to improve the bone biomechanical properties of OVX rats.

Strontium ranelate: short- and long-term benefits for post-menopausal women with osteoporosis

Strontium ranelate is a bone-seeking element that has been assessed in post-menopausal osteoporosis in two large double-blind, placebo-controlled studies. This treatment is able to decrease the risk of vertebral fractures, by 41% over 3 yrs, and by 49% within the first year of treatment. This risk of non-vertebral fractures is decreased by 16% and, in patients at high risk for such a fracture, the risk of hip fracture is decreased by 36% over 3 yrs. Recent 5-yr data from these double-blind, placebo-controlled studies show that the anti-fracture efficacy is maintained over time. Treatment efficacy with strontium ranelate has been documented across a wide range of patient profiles: age, number of prevalent vertebral fractures, BMI, as well as family history of osteoporosis and addiction to smoking are not determinants of anti-fracture efficacy. During these clinical trials, safety was good. Its large spectrum of efficacy allows the use of strontium ranelate in the different subgroups of patients with post-menopausal osteoporosis.

FRAX and the assessment of fracture probability in men and women from the UK

A fracture risk assessment tool (FRAX) is developed based on the use of clinical risk factors with or without bone mineral density tests applied to the UK.

INTRODUCTION

The aim of this study was to apply an assessment tool for the prediction of fracture in men and women with the use of clinical risk factors (CRFs) for fracture with and without the use of femoral neck bone mineral density (BMD). The clinical risk factors, identified from previous meta-analyses, comprised body mass index (BMI, as a continuous variable), a prior history of fracture, a parental history of hip fracture, use of oral glucocorticoids, rheumatoid arthritis and other secondary causes of osteoporosis, current smoking, and alcohol intake 3 or more units daily.

METHODS

Four models were constructed to compute fracture probabilities based on the epidemiology of fracture in the UK. The models comprised the ten-year probability of hip fracture, with and without femoral neck BMD, and the ten-year probability of a major osteoporotic fracture, with and without BMD. For each model fracture and death hazards were computed as continuous functions.

RESULTS

Each clinical risk factor contributed to fracture probability. In the absence of BMD, hip fracture probability in women with a fixed BMI (25 kg/m(2)) ranged from 0.2% at the age of 50 years for women without CRF's to 22% at the age of 80 years with a parental history of hip fracture (approximately 100-fold range). In men, the probabilities were lower, as was the range (0.1 to 11% in the examples above). For a major osteoporotic fracture the probabilities ranged from 3.5% to 31% in women, and from 2.8% to 15% in men in the example above. The presence of one or more risk factors increased probabilities in an incremental manner. The differences in probabilities between men and women were comparable at any given T-score and age, except in the elderly where probabilities were higher in women than in men due to the higher mortality of the latter.

CONCLUSION

The models provide a framework which enhances the assessment of fracture risk in both men and women by the integration of clinical risk factors alone and/or in combination with BMD.

The cost-effectiveness of alendronate in the management of osteoporosis

The National Institute for Health and Clinical Excellence (NICE) in the UK has recently issued health economic appraisals for the primary and secondary prevention of osteoporotic fracture that are more restrictive than previous guidelines for the management of osteoporosis despite a marked reduction of the cost of intervention. The aim of the present study was to examine the cost-effectiveness of the bisphosphonate, alendronate for the prevention and treatment of fractures associated with osteoporosis. A second aim was to investigate reasons for any disparities in cost-effectiveness between our findings and the NICE appraisals. We compared the effects of alendronate 70 mg weekly by mouth for 5 years with no treatment in postmenopausal women with clinical risk factors for fracture and computed the incremental cost-effectiveness ratio (ICER) using a lifetime simulation model based on Markov cohort methodology. A sensitivity analysis examined other common interventions. Using a threshold of pound sterling 30,000 and pound sterling 20,000 per quality of life-year (QALY) gained to determine cost-effectiveness, alendronate was cost-effective for the primary prevention of fracture in women with osteoporosis irrespective of age as was treatment of women with a prior fragility fracture irrespective of BMD. Cost-effective scenarios were also found in women with strong risk factors for fracture with a bone mineral density value above the threshold for osteoporosis. The results were robust over reasonable assumptions in sensitivity analysis. We conclude that alendronate is a cost-effective agent for the prevention and treatment of fractures associated with osteoporosis. These findings, suitable for informing practice guidance, contrast with recent appraisals from NICE.

Mild prevalent and incident vertebral fractures are risk factors for new fractures

This prospective four-year study indicates that post-menopausal osteoporotic women with mild prevalent and incident vertebral fractures have an increased risk of incident fractures.

INTRODUCTION

Mild vertebral fractures are under diagnosed as there is disagreement about their clinical significance. Our aim was to assess the risk of subsequent fractures induced by both prevalent and incident mild vertebral fractures in osteoporotic post-menopausal women.

PATIENTS AND METHODS

Three thousand three hundred and fifty-eight patients, aged 74 +/- 6 years, with post-menopausal osteoporosis included in the placebo groups of two clinical trials of strontium ranelate were followed for 4 years. A Cox regression model adjusted on age, body mass index and bone mineral density was used to calculate the relative risk (RR) of fracture in subjects with only mild fractures as compared to patients without fracture, and to patients with at least one grade >or= 2 fracture. These calculations were made for prevalent and then incident fractures.

RESULTS

The RR of vertebral fracture in 4 years was 1.8 (1.3-2.4) p < 0.001, and 2.7 (2.3-3.3) p < 0.001 for patients having only mild vertebral fractures and at least one grade >or= 2 fracture at baseline respectively. The RR of vertebral fracture in the 3rd and 4th years of follow-up was 1.7 (1.1-2.6) p = 0.01, and 1.9 (1.3-2.6) p < 0.001 for patients having during the first 2 years incident mild fractures only, and for patients having at least one grade >or= 2 incident fracture respectively. The RR of non-vertebral fracture in 4 years was 1.3 (0.9-1.9) p = 0.15 and 1.7 (1.4-2.1) p < 0.001 for patients having only mild or at least one grade >or= 2 vertebral fracture at baseline respectively. For patients aged more than 70 years, these RR were 1.45 (0.99-2.11) (p = 0.06), and 1.72 (1.36-2.18) p < 0.001 respectively. The RR of non-vertebral fracture in the 3rd and 4th years was 1.68 (1.36-2.09) p < 0.001 for patients having at least one grade >or= 2 incident fracture during the 2 first years of follow-up.

CONCLUSION

Mild vertebral fractures are a risk factor for subsequent vertebral and non-vertebral fracture in postmenopausal women with osteoporosis; 1 out of 4 patients with an incident mild vertebral fracture in 2 years will fracture again within the 2 next years.

From space to Earth: advances in human physiology from 20 years of bed rest studies (1986-2006)

Bed rest studies of the past 20 years are reviewed. Head-down bed rest (HDBR) has proved its usefulness as a reliable simulation model for the most physiological effects of spaceflight. As well as continuing to search for better understanding of the physiological changes induced, these studies focused mostly on identifying effective countermeasures with encouraging but limited success. HDBR is characterised by immobilization, inactivity, confinement and elimination of Gz gravitational stimuli, such as posture change and direction, which affect body sensors and responses. These induce upward fluid shift, unloading the body's upright weight, absence of work against gravity, reduced energy requirements and reduction in overall sensory stimulation. The upward fluid shift by acting on central volume receptors induces a 10-15% reduction in plasma volume which leads to a now well-documented set of cardiovascular changes including changes in cardiac performance and baroreflex sensitivity that are identical to those in space. Calcium excretion is increased from the beginning of bed rest leading to a sustained negative calcium balance. Calcium absorption is reduced. Body weight, muscle mass, muscle strength is reduced, as is the resistance of muscle to insulin. Bone density, stiffness of bones of the lower limbs and spinal cord and bone architecture are altered. Circadian rhythms may shift and are dampened. Ways to improve the process of evaluating countermeasures--exercise (aerobic, resistive, vibration), nutritional and pharmacological--are proposed. Artificial gravity requires systematic evaluation. This review points to clinical applications of BR research revealing the crucial role of gravity to health.

Strontium ranelate normalizes bone mineral density in osteopenic patients

AIMS

To assess the capacity of strontium ranelate to restore normal bone mineral density (WHO definition: T-score >or=-1) in post-menopausal osteopenic women (T-score between -1 and -2.5) at baseline.

METHODS

Post-hoc analysis from SOTI and TROPOS studies of 1428 patients randomly assigned to receive either 2 g of strontium ranelate a day or placebo for three years. Bone mineral density was measured at baseline and each year for three years. Results were analyzed on an intention-to-treat basis.

RESULTS

At lumbar spine, after one, two and three years of treatment with strontium ranelate, 26.4, 42.1 and 58.2% respectively of osteopenic patients normalized their bone mineral density, compared with 6.6, 8.9 and 11.9% in the placebo group (all p<0.001). At total hip, the percentage of patients normalizing their bone mineral density was 5.4, 10.0 and 19.6% in the strontium ranelate group and 1.8, 1.4 and 1.6% in the placebo one (all p<0.001).

CONCLUSION

Strontium ranelate is able to normalize bone mineral density in a significant proportion of osteopenic patients after one, two and three years of treatment. The clinical relevance of these results should be confirmed by direct demonstration of the anti-fracture efficacy of strontium ranelate in osteopenic patients.

The use of clinical risk factors enhances the performance of BMD in the prediction of hip and osteoporotic fractures in men and women

BMD and clinical risk factors predict hip and other osteoporotic fractures. The combination of clinical risk factors and BMD provide higher specificity and sensitivity than either alone. INTRODUCTION AND HYPOTHESES: To develop a risk assessment tool based on clinical risk factors (CRFs) with and without BMD.

METHODS

Nine population-based studies were studied in which BMD and CRFs were documented at baseline. Poisson regression models were developed for hip fracture and other osteoporotic fractures, with and without hip BMD. Fracture risk was expressed as gradient of risk (GR, risk ratio/SD change in risk score).

RESULTS

CRFs alone predicted hip fracture with a GR of 2.1/SD at the age of 50 years and decreased with age. The use of BMD alone provided a higher GR (3.7/SD), and was improved further with the combined use of CRFs and BMD (4.2/SD). For other osteoporotic fractures, the GRs were lower than for hip fracture. The GR with CRFs alone was 1.4/SD at the age of 50 years, similar to that provided by BMD (GR = 1.4/SD) and was not markedly increased by the combination (GR = 1.4/SD). The performance characteristics of clinical risk factors with and without BMD were validated in eleven independent population-based cohorts.

CONCLUSIONS

The models developed provide the basis for the integrated use of validated clinical risk factors in men and women to aid in fracture risk prediction.

A review of strontium ranelate and its effect on DXA scans

Strontium ranelate is a new orally administered agent for the treatment of women with postmenopausal osteoporosis that reduces the risk of vertebral and nonvertebral fractures. This review article examines the evidence for the antifracture efficacy and safety of strontium ranelate treatment and discusses the effect of DXA scans, biochemical markers of bone turnover, and bone histology. In the SOTI trial, three years treatment with strontium ranelate led to a 41% reduction in vertebral fracture risk (relative risk [RR]=0.59; 95% CI: 0.48-0.73; p<0.001), while in the TROPOS study there was a 16% reduction in nonvertebral fractures (RR=0.84; 95% CI 0.702-0.995; p=0.04). Compared with alternative osteoporosis therapies, strontium ranelate treated patients show large increases in BMD coupled with comparatively modest changes in biochemical markers of bone turnover and bone histology. While the large BMD changes provide a useful way of monitoring patients' response to treatment, it is important to appreciate that much of the increase is a purely physical effect due to the increased attenuation of X-ray when some of the calcium in bone is replaced by strontium. Strontium ranelate is a useful addition to the range of antifracture treatments available for treating postmenopausal women with osteoporosis and is the only treatment proven to be effective at preventing both vertebral and nonvertebral fractures in women aged 80 yr and older.

Strontium ranelate in the prevention of osteoporotic fractures

Osteoporosis results from a decrease in bone strength yielding increased susceptibility to fractures. Hip and spine fractures are a major cause of morbidity and mortality in the elderly population. With an increasingly ageing world population, early prevention of bone loss is essential for adequate control of this condition. Strontium ranelate (PROTELOS((R))), an oral drug for postmenopausal osteoporosis, has been reported to decrease bone resorption and to stimulate bone formation. The efficacy in reducing vertebral fractures, non-vertebral including hip fractures, and the safety of strontium ranelate has been initially demonstrated over 3 years in the SOTI (Spinal Osteoporosis Therapeutic Intervention) and TROPOS (TReatment Of Peripheral OSteoporosis) studies and confirmed recently over up to 5 years. A preplanned analysis of a sub-group of patients aged 80 years and over showed that, currently, strontium ranelate is the only antiosteoporotic agent to reduce vertebral and non-vertebral fractures in this age group.

Strontium-substituted apatite coating grown on Ti6Al4V substrate through biomimetic synthesis

During the last few years Strontium has been shown to have beneficial effects when incorporated at certain doses in bone by stimulating bone formation. It is believed that its presence locally at the interface between an implant and bone will enhance osteointegration and therefore, ensure the longevity of a joint prosthesis. In this study we explore the possibility of incorporating Sr into nano-apatite coatings prepared by a solution-derived process according to an established biomimetic methodology for coating titanium based implants. The way this element is incorporated in the apatite structure and its effects on the stereochemistry and morphology of the resulting apatite layers was investigated, as well as its effect in the mineralization kinetics. By using the present methodology it was possible to incorporate increasing amounts of Sr in the apatite layers. Sr was found to incorporate in the apatite layer through a substitution mechanism by replacing Ca in the apatite lattice. The presence of Sr in solution induced an inhibitory effect on mineralization, leading to a decrease in the thickness of the mineral layers. The obtained Sr-substituted biomimetic coatings presented a bone-like structure similar to the one found in the human bone and therefore, are expected to enhance bone formation and osteointegration.

Effect of bone strontium on BMD measurements

Strontium ranelate is a new treatment for osteoporosis that is of interest for, among other reasons, its unusual effect on measurements of bone mineral density (BMD). When some of the calcium in bone is replaced by strontium, X-ray absorptiometry measurements of BMD are overestimated because strontium attenuates X-rays more strongly than calcium. In this study, we report the first theoretical estimation of this effect for measurements made using axial (spine and hip) dual-energy X-ray absorptiometry (DXA), peripheral DXA (pDXA), and single-energy quantitative computed tomography (SEQCT). Tables of X-ray attenuation coefficients were used to calculate values of the strontium ratio defined as the ratio of the percentage overestimation of BMD to the molar percentage of strontium (%Sr/[Ca+Sr]) in bone. For DXA measurements, the theoretical value of the strontium ratio increased slightly with increasing effective photon energy of the X-ray beam with figures of 9.0 for Osteometer DTX200 and G4 pDXA devices (Osteometer Meditech Inc., Hawthorne, CA), 10.0 for GE-Lunar DPX and Prodigy DXA systems (GE-Lunar, Madison, WI), 10.4 for Hologic QDR1000 and QDR2000, and 10.8 for Hologic QDR4500 and Discovery (Hologic Inc., Bedford, MA). Results for SEQCT also varied with the effective photon energy with strontium ratios of 6.2 at 60 keV and 4.4 at 80 keV. The results of the theoretical study are in good agreement with the experimental value of 10 reported by Pors Nielsen and colleagues for a variety of different axial DXA systems. A reliable figure for the strontium ratio is important for adjusting BMD measurements in strontium ranelate treated patients for the effect of bone strontium content. This latter correction will be required for the interpretation of future DXA scans in patients who have discontinued strontium ranelate treatment.

Ostéoporose chez le sujet âgé

Osteoporosis is a frequent disease among the elderly and has major consequences in terms of mortality, morbidity and cost. Guidelines for diagnostic procedures are often difficult to apply in frail, elderly patients with multiple comorbidities. Bisphosphonates are the reference treatment for the elderly, combined with vitamin D and calcium supplementation. Vitamin D deficiency must also be treated to prevent falls and fractures. Strontium ranelate is a promising treatment in this population. Fall prevention is a major part of osteoporosis management. The potential benefit of hip protectors is questionable, even in institutionalized patients.

Addressing and meeting the needs of osteoporotic patients with strontium ranelate: a review

Patients with osteoporosis need a safe and effective treatment that reduces the risk of vertebral and non-vertebral fractures, leading to clinical benefits such as reduced back pain and height loss. Strontium ranelate corrects bone turnover, producing a more physiological state. Double-blind, placebo-controlled studies in postmenopausal osteoporosis show it to be effective in reducing vertebral and non-vertebral fracture risks. Treatment efficacy has been documented across a wide range of patient profiles, and appears to be independent of all the major determinants of fracture risk, including the severity of the disease at baseline, the number of prevalent fractures, and the age of the patient. This antifracture efficacy translates into clinical benefits, such as a 20% reduction in the rate of height loss and a 29% increase in the number of patients free of back pain. The effect of treatment with strontium ranelate on well-being has been assessed using the Quality-of-Life Questionnaire in Osteoporosis, which is a supplement to the 36-question Short-Form Health Survey. Treatment with strontium ranelate had a significant beneficial effect on the emotional, physical, and global Quality-of-Life Questionnaire in Osteoporosis scores compared with placebo. The rates of compliance with treatment were over 80% in phase III studies, reflecting the tolerability and safety profile and the ease of administration of this agent. Together with the antifracture data, the clinical benefits and quality of life data endorse the treatment of postmenopausal osteoporosis with strontium ranelate.

Strontium ranelate: a novel treatment for postmenopausal osteoporosis: a review of safety and efficacy

Strontium ranelate is a new orally administered agent for the treatment of women with postmenopausal osteoporosis that reduces the risk of vertebral and hip fractures. Evidence for the safety and efficacy of strontium ranelate comes from two large multinational trials, the SOTI (Spinal Osteoporosis Therapeutic Intervention) and TROPOS (Treatment Of Postmenopausal Osteoporosis) studies. The SOTI study evaluated vertebral fracture prevention in 1649 postmenopausal women with a mean age of 69 y. The subjects all had at least one previous vertebral fracture and a low spine bone mineral density (BMD) (equivalent to a Hologic spine T-score below -1.9). The strontium ranelate group had a 41% lower risk of a new vertebral fracture than the placebo group over the three-year study period (relative risk [RR] = 0.59; 95% confidence interval [CI]: 0.48-0.73; p < 0.001). The TROPOS study evaluated non-vertebral fracture prevention in 5091 postmenopausal women with a mean age of 77 y. The subjects were aged 74 y and over (or 70-74 y with one additional risk factor) and a low femoral neck BMD (equivalent to an NHANES III [Third National Health and Nutrition Examination Survey] T-score below -2.2). Over the three-year study period there was a 16% reduction in all non-vertebral fractures (RR = 0.84; 95% CI 0.702-0.995; p = 0.04) and a 19% reduction at the principal sites for non-vertebral fractures. The TROPOS study was not powered to investigate hip fracture risk. However, in a high risk group of women aged 74 y and over and with an NHANES III femoral neck T-score less than -2.4 there was a 36% reduction in hip fracture risk (RR = 0.64; 95% CI: 0.412-0.997; p = 0.046). The overall incidence of adverse events did not differ significantly from placebo and were generally mild and transient, the most common being nausea and diarrhea. Strontium ranelate is a useful addition to the range of anti-fracture treatments available for treating postmenopausal women with osteoporosis and is the only treatment proven to be effective at preventing both vertebral and hip fractures in women aged 80 y and over.

Anabolic Agents for Osteoporosis

Antiresorptive agents for osteoporosis are a cornerstone of therapy, but anabolic drugs have recently widened our therapeutic options. By directly stimulating bone formation, anabolic agents reduce fracture incidence by improving other bone qualities in addition to increasing bone mass. Teriparatide (human parathyroid hormone[1-34]) has clearly emerged as a major approach for selected patients with osteoporosis. Teriparatide increases bone mineral density and bone turnover, improves bone microarchitecture, and changes bone size. The incidence of vertebral and non-vertebral fractures is reduced. Teriparatide is approved in many countries throughout the world for the treatment of both postmenopausal women and men with osteoporosis who are at high risk for fracture. Another anabolic agent, strontium ranelate, may both promote bone formation and inhibit bone resorption. Clinical trials support the use of strontium ranelate as a treatment for postmenopausal osteoporosis and have shown that strontium ranelate reduces the frequency of vertebral and non-vertebral fractures. Other potential anabolic therapies for osteoporosis, including other forms of parathyroid hormone, growth hormone, and insulin-like growth factor-I, have been examined, although less data are currently available on these approaches.