Aging bone and osteoporosis: strategies for preventing fractures in the elderly

As the older population increases, the incidence of osteoporotic fractures is expected to dramatically rise during the next few decades. Older patients are much more susceptible to fracture at any given bone mineral density (BMD) than are younger patients because of various factors, including the quality of aging bone, which involves more than BMD. Suppression of increased bone turnover by antiresorptive therapies, even with only small changes in BMD, can reduce fracture risk, especially in the lumbar spine. Bisphosphonate treatment can significantly reduce vertebral and nonvertebral fractures, including hip fractures, even in the very elderly. Prospective analyses show that risedronate therapy consistently and significantly reduces the risk of new morphometric vertebral fractures after 1 year in postmenopausal women. Post hoc analyses report significant reductions in the risk of 1 new clinical vertebral fracture after 6 months of risedronate therapy and after 1 year of alendronate therapy. Oral raloxifene therapy and salmon calcitonin nasal spray therapy have been shown to reduce the risk of vertebral fracture after 3 and 5 years, respectively, and post hoc data show a significant reduction in clinical vertebral fracture risk at 1 year with raloxifene use. However, neither raloxifene therapy nor calcitonin therapy reduce the risk of nonvertebral and hip fractures at currently approved doses. Bisphosphonates have been shown to be safe and efficacious with 7 years' risedronate sodium and 10 years' alendronate sodium data published, and bisphosphonates reduce bone turnover and increase BMD to a greater degree than raloxifene and calcitonin, which may partly account for their nonvertebral and hip fracture reduction effect. Therefore, bisphosphonate therapy with risedronate or alendronate should be considered in patients with low BMD at the hip and in older patients with osteoporosis and osteopenia, particularly those with an existing fracture.     

Treating osteoporosis to prevent fractures: current concepts and future developments

Antiresorptive drugs, such as the bisphosphonates and the RANKL inhibitor denosumab, are currently the most widely used osteoporosis medications. These drugs increase bone mineral density (BMD) and reduce the risk of vertebral (by 40–70%), nonvertebral (by 25–40%) and hip fractures (by 40–53%) in postmenopausal women with osteoporosis. Due to the risk of rare side‐effects, the use of bisphosphonates has been limited to up to 10 years with oral bisphosphonates and 6 years with intravenous zoledronic acid. Despite their well‐proven efficacy and safety, few women at high risk of fracture are started on treatment. Case finding strategies, such as fracture risk‐based screening in primary care using the fracture risk assessment tool (FRAX) and Fracture Liaison Services, have proved effective in increasing treatment rates and reducing fracture rates. Recently, anabolic therapy with teriparatide was demonstrated to be superior to the bisphosphonate risedronate in preventing vertebral and clinical fractures in postmenopausal women with vertebral fracture. Treatment with the sclerostin antibody romosozumab increases BMD more profoundly and rapidly than alendronate and is also superior to alendronate in reducing the risk of vertebral and nonvertebral fracture in postmenopausal women with osteoporosis. For patients with severe osteoporosis and high fracture risk, bisphosphonates alone are unlikely to be able to provide long‐term protection against fracture and restore BMD. For those patients, sequential treatment, starting with a bone‐building drug (e.g. teriparatide), followed by an antiresorptive, will likely provide better long‐term fracture prevention and should be the golden standard of future osteoporosis treatment.     

Calcitonin.

Calcitonin is FDA approved for the treatment of postmenopausal osteoporosis but not for prevention. The preferred delivery system is nasal. Nasal calcitonin is safe and well tolerated. The vertebral fracture efficacy of calcitonin is less robust than the two approved bisphosphonates (alendronate and risedronate) but is similar to raloxifene in the treatment of established osteoporosis. Calcitonin has not been demonstrated to reduce hip fracture risk, although a post-hoc pooled analysis suggests potential effectiveness of nasal calcitonin. Calcitonin produces small increments in bone mass of the spine and modestly reduces bone turnover in women with osteoporosis. Calcitonin may have analgesic benefit in patients with acute painful vertebral fractures. Treatment with calcitonin should be considered for older women with osteoporosis with painful vertebral fractures and for women who fail to respond to or cannot tolerate bisphosphonates. Calcitonin may also be indicated for women who are unable to take bisphosphonates because of impaired renal function.     

Clinical Pharmacology of Potent New Bisphosphonates for Postmenopausal Osteoporosis

Bisphosphonates are potent inhibitors of bone resorption, used in most bone diseases associated with high bone resorption levels. Several bisphosphonates, developed to prevent and treat postmenopausal osteoporosis, increase bone mineral density and decrease biochemical markers of bone turnover, and more importantly, reduce fracture risk. Alendronate and risedronate have proven their efficacy to reduce vertebral and hip fracture risk among postmenopausal osteoporotic women, using daily regimens. Weekly intermittent schedules, however, are now most commonly prescribed, because they have shown pharmacologic equivalence to the daily regimen. Ibandronate has been the first bisphosphonate to demonstrate vertebral fracture risk reduction using an intermittent regimen. Studies using ibandronate as intravenous injections every 3 months are under way. Zoledronic acid may also be an attractive option for the treatment of postmenopausal osteoporosis if a large ongoing trial proves that a single annual injection of this compound allows osteoporotic fracture risk reduction.     

Osteoporosebehandlung: Bisphosphonate, SERM’s, Teriparatide und Strontium

The therapy of osteoporosis is mostly based upon the use of drugs which inhibit bone resorption. Among these, the bisphosphonate family is the best known and mostly used by clinicians. Both second and third generation bisphosphonates, like alendronate and risedronate, are now available as weekly tablets which have facilitated the patient compliance to treatment together with a decreased occurrence of gastrointestinal side effects. These compounds are used efficiently to treat postmenopausal osteoporosis and osteoporosis of men as well. Their use did provide good evidence of increased bone mineral density (BMD) and a reduction in fracture rates. The use of intravenous bisphosphonates such as Zoledronate, Ibandronate and Pamidronate remains in most of the cases limited to special indications such as intolerance to the oral formulations and treatment of patients with bone metastases. The selective estrogen modulators (SERM's) family is limited to a single product on the market as of now, Raloxifene, which does inhibit bone resorption and is well documented by postmenopausal women to increase BMD and reduce vertebral fractures. In addition, a large range of positive nonosseous effects have been documented such as the reduction of the incidence of breast cancer. Other substances do have a strong anabolic effect such as Teriparatide, a recombinant human formulation of PTH 1-34. This compound has demonstrated good efficacy in postmenopausal women, increasing vertebral and hip BMD and reducing the incidence of fractures at both sites. The exact role of Teriparatide in the clinical setting is still open but its overall impact in the therapy of osteoporosis could be major due to its major efficiency over shorter periods of time. Strontium ranelate, a new divalent Strontium salt taken orally, acts both as an anti-catabolic and anabolic agent. The first results provided with strontium ranelate are very promising due to its major effect on the increase in BMD both at the vertebral and hip sites and its ability to reduce the incidence of fractures at both locations. Additional data are awaited to confirm these initial positive results.     

Preventing osteoporotic fractures with bisphosphonates: a review of the efficacy and tolerability

Although change in bone mineral density was the outcome most commonly measured in early clinical trials of osteoporosis therapies, it is now understood that the most clinically important outcome is reduction in the risk of fractures. Of currently available osteoporosis therapies, the bisphosphonates have been most thoroughly investigated in studies with fracture risk as the primary outcome. The most widely studied bisphosphonates include etidronate, alendronate and risedronate. Alendronate and risedronate have the most compelling evidence for vertebral and non-vertebral fracture reduction. This review provides a comprehensive overview of the anti-fracture efficacy of bisphosphonates at the spine, hip, and non-vertebral sites.     

The Treatment of Severe Postmenopausal Osteoporosis

Several chemical entities have shown their ability to reduce axial and/or appendicular fractures in patients with osteoporosis. Since patients who have experienced a previous fracture are at high risk for subsequent vertebral or hip fracture, it is of prime importance to treat such patients with medications that have unequivocally demonstrated their ability to reduce fracture rates in patients with prevalent fractures. Results obtained with calcium and vitamin D, in this particular population, are not fully satisfactory and these medications are probably better used in conjunction with other therapeutic regimens. Bisphosphonates have shown their ability to reduce vertebral (alendronate, risedronate, ibandronate) and non-vertebral (alendronate, risedronate) fractures in patients with established osteoporosis. Raloxifene has also shown similar properties, notwithstanding its effect on non-vertebral fractures, which has only been derived from a post hoc analysis limited to patients with prevalent severe vertebral fractures at baseline. This compound also has interesting non-skeletal benefits, including effects on the breast and heart. Teriparatide, a bone-forming agent, promptly reduces the rate of vertebral and all non-vertebral fractures, without significant adverse effects. Strontium ranelate, the first agent shown to concomitantly decrease bone resorption and stimulate bone formation, has also shown its ability to reduce rates of vertebral and non-vertebral fractures in patients with established osteoporosis. It significantly reduces hip fractures in elderly individuals at high risk for such events. Its safety profile is also excellent.     

The use of bisphosphonates in the treatment of osteoporosis

PURPOSE OF REVIEW: The bisphosphonates alendronate and risedronate, given orally once weekly, are the cornerstone of treatment of postmenopausal osteoporosis, as well as of male and secondary osteoporosis. They reduce significantly the risk of vertebral and nonvertebral fractures; their effects appear early, within 6-12 months, and appear to be sustained. Several questions remain unanswered, however. In addition, data on a new bisphosphonate became available in 2004. RECENT FINDINGS: The optimal duration of treatment has not been clearly established. Long-term data with alendronate are now available, indicating a persistence of alendronate effects on bone mineral density and bone turnover markers several years after stopping treatment given for 5 years. Whether these effects translate into sustained reduction of fractures needs to be further analyzed. Because of their efficacy, bisphosphonate use has been explored in other forms of osteoporosis, such as after androgen deprivation therapy for prostatic cancer. The challenge of long-term compliance with treatment of osteoporosis has triggered the use of intermittent bisphosphonate. The effects of intermittent oral and intravenous ibandronate on bone mineral density, bone turnover, and fractures have been recently reported. SUMMARY: The mechanism by which bisphosphonates improve bone strength is not yet fully understood but probably involves complex effects on different components of bone strength, such as microarchitecture.     

Raloxifene for older women: a review of the literature

Raloxifene is a non-steroidal selective estrogen-receptor modulator (SERM) which is used for prevention and treatment of postmenopausal osteoporosis. Raloxifene decreases the incidence of vertebral fractures by 30%–50% in postmenopausal women with osteoporosis but has not been shown to decrease the incidence of hip fractures or other non-vertebral fractures. At the present time, estrogen-replacement therapy and bisphosphonate treatment are the only medical treatments that are proven to prevent hip fractures with the exception of vitamin D and calcium replacement, which has been shown to prevent hip fractures in elderly individuals and nursing home residents. Raloxifene has been shown to have additive effects on bone turnover and bone mineral density (BMD) when used along with alendronate and teriparatide. Raloxifene could have a role in renal failure as it has been shown to increase BMD of the vertebra over 1 year of therapy. Raloxifene is as effective as tamoxifen in reducing the risk of invasive breast cancer. The increased incidence of venous thromboembolism is the main concern of raloxifene therapy and previous history of venous thromboembolism is a contraindication for use of raloxifene. Raloxifene has a role in treatment of vertebral osteoporosis in older women. The decision to use raloxifene should be based on evaluation of fracture risk and on potential other benefits than fracture reduction along with consideration of side effects.     

Bisphosphonate treatment of osteoporosis

Bisphosphonates represent the agents of choice for most patients with osteoporosis. They are the best studied of all agents for the prevention of bone loss and reduction in fractures. They increase BMD, primarily at the lumbar spine, but also at the proximal femur. In patients who have established osteoporosis, bisphosphonates reduce the risk of vertebral fractures, and are the only agents in prospective trials to reduce the risk of hip fractures and other nonvertebral fractures. Bisphosphonates reduce the risk of fracture quickly. The risk of radiographic vertebral deformities is reduced after 1 year of treatment with risedronate [68]. The risk of clinical vertebral fractures is reduced after 1 year of treatment with alendronate [69] and just 6 months' treatment with risedronate [157]. The antifracture effect of risedronate has been shown to continue through 5 years of treatment [158]. Alendronate and risedronate are approved by the FDA for prevention of bone loss in recently menopausal women, for treatment of postmenopausal osteoporosis, and for prevention (risedronate) and treatment (alendronate and risedronate) of glucocorticoid-induced osteoporosis. Alendronate is also approved for treatment of osteoporosis in men. Other bisphosphonates (etidronate for oral use, pamidronate and zoledronate for intravenous infusion) are also available and can be used off label for patients who cannot tolerate approved agents. Although bisphosphonates combined with estrogen or raloxifene produce greater gains in bone mass compared with single-agent treatment, the use of two antiresorptive agents in combination cannot be recommended because the benefit on fracture risk has not been demonstrated and because of increased cost and side effects.     

Risedronate once monthly: a potential new regimen for the treatment of postmenopausal osteoporosis

Postmenopausal osteoporosis increases susceptibility to low-trauma fractures due to reduced bone volume and microarchitectural deterioration. Daily nitrogen-containing bisphosphonates have shown antifracture efficacy in many studies and are the most commonly prescribed treatment for women with postmenopausal osteoporosis. However, optimal efficacy is often not achieved due to poor patient adherence to medication. Current dosing schedules are often inconvenient or impractical for patients. Poor adherence increases risk of fracture, which itself increases morbidity, healthcare costs and, potentially, mortality. Although weekly rather than daily dosing of bisphosphonates has improved adherence, significant problems remain. Efforts to reduce dosing frequency as a possible means for further improving adherence (compliance and persistence), and therefore treatment outcomes, are ongoing. Risedronate, a third-generation bisphosphonate, has been shown in multiple clinical trials to reduce fracture risk and improve bone mineral density in postmenopausal women with osteoporosis. Risedronate has a specific structure and set of characteristics that enable less frequent dosing. This paper reviews the structure of risedronate, and how this translates into high antiresorptive potency, favorable bone binding, persistence in bone, and good tolerability that permits less frequent dosing. The paper also reviews the clinical evidence for risedronate, demonstrating the viability of less frequent dosing, with its potential benefits for patient convenience and adherence to therapy. Two equivalence or non-inferiority bridging studies have demonstrated the option of novel risedronate dosing regimens. These studies are reviewed to demonstrate the efficacy and safety of two different monthly regimens of risedronate in the treatment of postmenopausal osteoporosis: 75 mg on 2 consecutive days a month and 150 mg once a month. Data for oral risedronate 150 mg once a month are limited to 1 year’s treatment duration. In previous clinical trials, patients receiving risedronate 5 mg daily have been followed for up to 7 years, with no evidence of loss of effectiveness. Risedronate 150 mg once a month has a comparable efficacy and safety to daily doses in the treatment of postmenopausal osteoporosis. These additional treatment options with risedronate provide easier dosing alternatives for patients.     

Selection of individuals for prevention of fractures due to bone fragility.

Most patients with fractures go untreated because of the lack of awareness of osteoporosis. Treatment is indicated for women and men with osteoporosis and women and men with fractures with either osteoporosis or osteopenia because (a) fractures increase morbidity and mortality, (b) the burden of fractures is increasing because longevity is increasing, and (c) bone loss accelerates, rather than decelerates in old age. The indication for drug therapy is less clear in women or men with osteopenia because drugs have not been proved to reduce fracture risk in this group. There is no evidence that treating individuals with only risk factors reduces the fracture rate. Screening has not been shown to reduce the burden of fractures. Altering the bone mineral density by a few percent in the population is likely to reduce the number of fractures, but how this can be achieved is unknown. The rigorously investigated drugs reducing the spine fracture rate are alendronate, raloxifene and risedronate. Calcium and vitamin D reduce hip fractures in nursing home residents but not community-dwellers. In the community, only alendronate and risedronate have been reported to reduce hip fractures in randomized trials. The evidence for hormone replacement therapy is less satisfactory. It is likely to reduce the number of spinal fractures, but its role in hip fracture prevention is uncertain. Only alendronate has been reported to reduce spine fractures in men with osteoporosis. Evidence for the use of other drugs (calcitonin, fluoride, anabolic steroids and active vitamin D metabolites) in women or men is insufficient to justify their use.     

Treatment of osteoporosis and Paget's disease

Osteoporosis is a major public health problem. In women, the estimated lifetime risks of hip and vertebral fractures are 15% and 25%, respectively. The development of accurate and reproducible methods of assessing bone mineral density has enabled identification of persons at risk of fracture and assessment of response to treatment. Estrogen replacement therapy is effective in the prophylaxis of postmenopausal osteoporosis, and is the only therapy with well-proven antifracture efficacy. Fluoride can dramatically increase bone density, although a recent large, controlled study has demonstrated no effect on vertebral fractures. Bisphosphonates are emerging as a likely effective therapy for both idiopathic and glucocorticoid-induced osteoporosis. Calcium, vitamin D, calcitonin, and anabolic steroids may still have a role. Parathyroid hormone is a promising development that will need further study. Paget's disease is also common, affecting more than 3% of people over 40 years old. Calcitonin is an established therapy, although the bisphosphonates are a promising alternative.     

Assessment of the Relationship Between Age and the Effect of Risedronate Treatment in Women with Postmenopausal Osteoporosis: A Pooled Analysis of Four Studies

OBJECTIVES: To quantify the effect of age on the incidence of osteoporosis‐related fractures and of risedronate treatment on fracture risk in different age groups in women with postmenopausal osteoporosis. DESIGN: Data from four randomized, double‐blind, placebo‐controlled, Phase III studies were pooled and analyzed. PARTICIPANTS: The analysis population (N=3,229) consisted of postmenopausal women with osteoporosis as determined on the basis of prevalent vertebral fractures, low bone mineral density (BMD), or both. INTERVENTION: Patients had received risedronate 5 mg daily or placebo for 1 to 3 years. MEASUREMENTS: The endpoints of interest were the incidence of osteoporosis‐related fractures, clinical fractures, nonvertebral fractures, and morphometric vertebral fractures. The effect of age on fracture risk and treatment benefit was examined using Cox regression models with age and treatment as explanatory variables. The 3‐year fracture risk was estimated for patients in each treatment group at a given age. RESULTS: Irrespective of treatment, fracture risks were greater in older patients (P<.001). On average, for every 1‐year increase in age, a patient's risk for osteoporosis‐related fracture increased 3.6% (95% confidence interval=2.3–5.0%). Irrespective of age, risedronate treatment reduced fracture risk 42%. Risedronate‐treated patients had fracture risks similar to those of placebo‐treated patients 10 to 20 years younger. CONCLUSION: Patients treated with risedronate have a significantly lower fracture risk, similar to that of untreated patients 10 to 20 years younger.     

Treatment of osteoporosis with bisphosphonates

Bisphosphonates are safe and effective agents for treatment and prevention of osteoporosis. Alendronate and risedronate are the best studied of all agents for osteoporosis in terms of efficacy and safety. They increase bone mass. In patients who have established osteoporosis, they reduce the risk of vertebral fractures. They are the only agents shown in prospective trials to reduce the risk of hip fractures and other nonvertebral fractures. They are approved by the US FDA for prevention of bone loss in recently menopausal women, for treatment of postmenopausal osteoporosis, and for management of glucocorticoid-induced bone loss. Other bisphosphonates (e.g., etidronate for oral use, pamidronate for intravenous infusion) are also available and can be used off-label for patients who cannot tolerate approved agents. Bisphosphonates combined with estrogen produce greater gains in bone mass compared with either agent used alone; whether there is a greater benefit of combination therapy on fracture risk is not clear. Combining a bisphosphonate with raloxifene or calcitonin is probably safe, although data on effectiveness are lacking.     

Risedronate prevents new vertebral fractures in postmenopausal women at high risk

Independent risk factors for fracture include advanced age, preexisting fractures, and low bone mineral density. Rised-ronate has been shown in several large trials to be safe and effective for patients with osteoporosis, but its effects in populations at high risk are not well characterized. To determine the effect of risedronate on vertebral fracture in high-risk subjects, we pooled data from two randomized, double-blind studies [Vertebral Efficacy with Risedronate Therapy (VERT) Multinational (VERT-MN) and VERT-North America (VERT-NA)] in 3684 postmenopausal osteoporotic women treated with placebo or risedronate 2.5 or 5 mg/d and analyzed fracture risk in subgroups of subjects at high risk for fracture due to greater age or more prevalent fractures (vs. median for overall study population), or lower bone mineral density (T-score, -2.5 or less). Fractures were diagnosed by quantitative and semiquantitative assessment of radiographs at baseline and 1 yr. In the overall population, treatment for 1 yr with risedronate 5 mg/d reduced the risk of new vertebral fractures by 62% vs. control (relative risk, 0.38; 95% confidence interval, 0.25, 0.56; P < 0.001) and of multiple new vertebral fractures by 90% vs. control (relative risk, 0.10; 95% confidence interval, 0.04, 0.26; P < 0.001). Consistent risk reductions were observed at 1 yr in the risedronate-treated high-risk subgroups. Significant reduction in fracture risk after 1 yr is an important benefit in patients at high risk for fracture because, without treatment, these patients are likely to sustain new fractures in the near term.     

Steroid induced osteoporosis: prevention and treatment

PURPOSE: Corticosteroid induced osteoporosis (CIO) is the most frequent complication of long-term corticosteroid therapy, and the most frequent cause of secondary osteoporosis. New data from biological, epidemiological and therapeutic studies provide basis for optimal management of this bone disease. MAIN POINTS: Corticosteroids are responsible for both quantitative and qualitative deleterious effects on bone, through their effect on bone cells, mainly on osteoblasts (with both a decrease in osteoblast activity and an increase in apoptosis). Epidemiological studies have shown an increased risk of fractures related to CIO, even for low doses, and during the first 6 months of treatment. Relative risk is 1.3 and 2.6 for peripheral and vertebral fractures respectively. Bone mineral density, measured by dual-energy X-ray absorptiometry, is decreased at spine and hip; the risk of fracture is higher in CIO as compared to post-menopausal osteoporosis, for a similar bone density. Prevention of CIO needs the use of the minimal efficacious dose, and treatment of calcium, vitamin D and gonadal hormones insufficiencies. Patients at risk of fracture, as post-menopausal women with prevalent fractures, should receive a bisphosphonate. PERSPECTIVE: It may be possible to reduce the fracture risk in patients on long-term corticosteroid therapy.     

Postmenopausal osteoporosis. What have we learned since the introduction of bisphosphonates?

Over the past 12 years bisphosphonates have become a mainstay of treatment for postmenopausal osteoporosis. As a class, bisphosphonates significantly suppress bone turnover and increase BMD at the lumbar spine and other site through their direct inhibitory effects on osteoclasts. Alendronate and risedronate reduce the incidence of clinical vertebral and non-vertebral fractures. Etidronate and both oral and intravenous ibandronate reduce the incidence of clinical vertebral fractures, but data from primary analyses for reduction in non-vertebral fractures are currently less robust. Intravenous administration of zoledronate is under late-stage investigation for use in postmenopausal osteoporosis. Combinations of alendronate with estrogen or raloxifene provide a greater reduction in bone turnover markers and greater increases in BMD, but fracture risk reduction has not been determined. Overall, bisphosphonates are well tolerated. The most common side effects of oral bisphosphonates are upper gastrointestinal symptoms. Newer safety concerns about the use of bisphosphonates include osteonecrosis of the jaw and oversuppression of bone turnover. The optimal duration of bisphosphonate treatment has not been clearly established.     

Prevention and treatment strategies for glucocorticoid-induced osteoporotic fractures

Glucocorticoids are the most common cause of drug-related osteoporosis. We reviewed current evidence on risk factors for glucocorticoid-induced osteoporosis (GIOP) and prevention and treatment of GIOP-related fractures. Guidelines for GIOP management published since 2000 were also reviewed. Significant bone loss and increased fracture risk is seen with daily prednisone doses as low as 5 mg. Alternate-day glucocorticoid therapy can lead to similar bone loss. No conclusive evidence exists for a safe minimum dose or duration of glucocorticoid exposure. Physicians should consider risk factors for involutional osteoporosis such as older age, postmenopausal status, and baseline bone density measurements as they assess patients for prevention or treatment of GIOP. Bisphosphonates were reported to reduce GIOP-related vertebral fractures, but inconclusive data exist for hip fractures associated with glucocorticoid use. Hormone replacement therapy and parathyroid hormone analogs are effective in preserving bone density in GIOP. The risk of osteoporosis and fractures should be routinely assessed in patients receiving glucocorticoid therapy. Effective prevention and treatment options are available and can result in meaningful reduction of GIOP-related morbidity and mortality. Current guidelines for GIOP management recommend bisphosphonates, especially alendronate and risedronate, as first-line agents for GIOP, and these guidelines propose the preventive use of bisphosphonates early in the course of glucocorticoid therapy in high-risk patient subgroups.     

Preventing osteoporotic fractures with antiresorptive therapy: implications of microarchitectural changes

Prospective studies have demonstrated that low bone mass correlates well with increased risk of osteoporotic fractures at various skeletal sites. Trials have likewise confirmed that enhancing bone mass with antiresorptive therapy reduces fracture incidence in individuals at risk. However, correlation of bone mineral density (BMD) increases with therapeutic risk reduction has proved less consistent than correlation of BMD decreases with greater fracture risk in the untreated. Indeed, various analyses have indicated that - even during treatment with potent bisphosphonates like alendronate and risedronate - BMD changes from baseline account for <30% of the reduction in vertebral fractures in treated women. It is clearly, therefore, that factors other than BMD are involved in the reduction of fracture risk achieved by antiresorptive therapies. According to recent micro-computed tomography imaging and other studies, antiresorptive therapy can help rebuild the microarchitecture of bone as well as strengthen the materials that go into it. When treating individuals with osteoporosis, these microarchitectural changes contribute to the reduction of fracture risk achieved by antiresorptive therapies.