Fracture prevention is a critical component of managing osteoporosis, which is not longer defined by T-score alone. The internationally validated World Health Organization Fracture Risk Assessment Tool (FRAX) provides the clinician a state-of-the-art tool for predicting patients at greatest risk for fracture. The FRAX tool takes into account country, bone mineral density of the hip (when available), age, sex, and 8 clinical risk factors to calculate the 10-year probability of a major osteoporotic fracture and the 10-year probability of a hip fracture. From this tool, an absolute fracture risk is generated, aiding clinicians in determining which patients with low bone mass and osteoporosis to treat.
Drs Shuler and Salava are from the Department of Orthopaedic Surgery, and Mr Kendall is from the Office of Medical Education, Marshall University, Huntington, West Virginia; and Dr Conjeski is from the Department of Orthopaedics, University of South Florida, Tampa, Florida.
The material presented in any Vindico Medical Education continuing education activity does not necessarily reflect the views and opinions of Orthopedics or Vindico Medical Education. Neither Orthopedics nor Vindico Medical Education nor the authors endorse or recommend any techniques, commercial products, or manufacturers. The authors may discuss the use of materials and/or products that have not yet been approved by the US Food and Drug Administration. All readers and continuing education participants should verify all information before treating patients or using any product.
Correspondence should be addressed to: Franklin D. Shuler, MD, PhD, Department of Orthopaedic Surgery, Marshall University, 1600 Medical Center Dr, Ste G 500, Huntington, WV 25701 (firstname.lastname@example.org)
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Globally, osteoporosis is the most common bone disease, with fracture as the biggest individual and societal problem associated with this disorder. The prevalence of osteoporosis is explained by the loss of bone mass associated with normal aging (Figure 1).1 Worldwide population growth and aging are expected to significantly increase the prevalence of osteoporosis, low bone mass, and associated fractures (Figure 2).2
Figure 1: Bone mass life cycle. During the normal bone mass life cycle, a steady increase in bone mass occurs through puberty that typically peaks near the third decade of life. Once it has peaked, bone mass is subject to a slow loss phase followed by a rapid loss phase. This decrease in bone mass commonly results in osteopenic bone and then osteoporotic bone, particularly in menopausal women. Adapted from Ilich and Kerstetter.1
Figure 2: Worldwide osteoporotic hip fractures. The prevalence of osteoporosis is estimated to significantly increase worldwide due to aging and population growth. Hip fractures are frequently used to estimate the individual and societal effect of osteoporosis, with significant increases in worldwide hip fracture rates expected by 2050. Data from Cooper et al.2
It was projected that by 2010 in the United States, 52.4 million individuals older than 50 years would have osteoporosis and low bone mass (Figure 3).3 By 2020, almost 14 million individuals older than 50 years are expected to have osteoporosis, and another 47 million will likely have low bone mass. Osteoporosis is the most common underlying cause of fractures and accounts for approximately 1.5 million fractures in the United States each year (Figure 4).4–7 Worldwide, the risk of osteoporotic fracture can vary up to 10-fold, depending on country of origin, with US Caucasians having the greatest reported risk of fracture (Figure 5).8–10 It is estimated that 1 of 2 Caucasian women and 1 of 5 Caucasian men will sustain an osteoporosis-related fracture sometime within his or her lifetime.4
Figure 3: Projected growth in the US prevalence of osteopenia and osteoporosis. The prevalence of osteopenia and osteoporosis is estimated to increase by another 9 million individuals from 2010 to 2020. Data from the National Osteoporosis Foundation.3
Figure 4: Osteoporotic fractures compared with other diseases. The annual risk of an osteoporotic fracture far exceeds the risk of other diseases receiving more attention. Osteoporotic fracture annual incidence* surpasses the combined estimated incidence of heart attacks in women older than 29 years,† stroke in women older than 30 years,† and new breast cancer cases‡ by more than 60%. Data from *Riggs and Melton,5†the American Heart Association,6 and ‡the American Cancer Society.7
Figure 5: Osteoporotic fracture probability is country specific. The figure illustrates the variability between countries for the 10-year fracture probability for a 65-year-old woman with a body mass index of 23.5 kg/m2 and no clinical risk factors. In the United States, Caucasians have the greatest risk of fracture, followed by Hispanics and African Americans. Data from Elffors et al,8 Kanis et al,9 and Thomas.10
Each year in the United States, fractures due to osteoporosis account for more than 500,000 hospitalizations, more than 800,000 emergency room encounters, more than 2.6 million physician office visits, and approximately 180,000 individuals being placed into nursing homes.4 Hip fractures alone are responsible for 300,000 hospitalizations annually.4 The morbidity associated with hip fractures is staggering: 24% of senior citizens die within 1 year, 20% will require long-term nursing home care, and only 40% return to their prefracture level of functioning (Figure 6).4,11,12 Hip fractures are associated with a 250% increased risk of future non-hip skeletal fracture.13 The individual and societal costs of hip fractures in the ultrasound are expected to exponentially increase due to the rate of hip fractures increasing by 100% to 200% by 2040.4 In addition, patients with any type of osteoporosis-related fracture can have morbidities and may be plagued with subsequent psychological symptoms such as depression and low self-esteem due to the pain, physical limitations, and lifestyle and cosmetic changes.14 For many patients, an osteoporotic fracture may lead to a downward spiral of physical and mental health.4
Figure 6: One-year hip fracture mortality and morbidity. Hip fractures have a significant morbidity, with a mortality more than 20% that extends well beyond 12 months following fracture. At 1 year, a large percentage of patients have residual functional deficits in essential and instrumental activities of daily living. Data from Lu-yao et al11 and Cooper.12
As a result of the high volume of osteoporotic fractures that occur each year, health care expenditures to treat these fractures exceed those of many other major diseases, including heart disease, stroke, and breast cancer (Figure 4).15 The annual direct care costs for osteoporotic fractures range from 12 to 18 billion dollars per year in 2002 currency.4 Annual costs related to osteoporotic fractures are projected to increase by approximately 50% by 2025 and to double or triple by 2040.4,16
Too often, osteoporosis is considered by the general public, and even the medical community, to be a normal part of the aging process and an unavoidable consequence of growing older. However, osteoporosis can be a detectable, preventable, and treatable disease.
Osteoporosis is the most common bone disease in humans and results from a combination of genetic and environmental factors.4,17 As defined by the World Health Organization (WHO), osteoporosis is a disease characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk.18 This disease occurs when the natural cycle of bone breakdown and bone formation becomes imbalanced. Normally, this cycle of bone turnover is necessary for bone growth, repair of minor bone damage caused by everyday stress, and maintenance of proper bodily functions. Annually, 10% to 30% of the skeleton is remodeled in this fashion, and the process is controlled by a complex interplay of hormones and chemical factors. Examples of these regulating substances include estrogen, testosterone, parathyroid hormone, vitamin D, and blood factors involved in cell growth; fluctuations in the levels of any of these factors can influence the development of osteoporosis. Until approximately age 40, the healthy adult displays a nearly perfectly balanced system of bone resorption and bone formation (Figure 1). However, as people age, or due to medications or illnesses, this process can be disrupted and the breakdown of bone eventually becomes greater than the rate of bone formation.19 As a consequence, trabecular plates of bone are lost, leaving an architecturally weakened structure with a significantly reduced mass. Bone strength reflects the integration of bone quality (rate of bone remodeling, trabecular connectivity, degree of mineralization, and damage accumulation) and bone mineral density (BMD).20
Osteoporosis is often a clinically silent disease, with initial diagnosis provided by a sentinel low-energy fracture of the wrist, spine, or hip. Without the presence of a low-energy fracture, osteoporosis is frequently clinically diagnosed following interpretation of BMD measured by dual-energy x-ray absorptiometry (DXA).15 The WHO defines osteoporosis in relation to T-score values obtained from DXA. Several other imaging modalities are available for characterization of bone density (eg, ultrasound, quantitative computed tomography, standard radiography, magnetic resonance imaging, and single-energy absorptiometry), but these are either not readily available or do not generate T-score values.14,17,21
In postmenopausal women and men older than 50 years, T-score values calculated from central (lumbar spine and femoral neck) DXA can be applied to WHO diagnostic criteria (normal, osteopenia, and osteoporosis).14 T-scores between −1 and −2.5 indicate patients with osteopenia, or low bone mass. The WHO determined that a T-score of 2.5 or fewer SDs below the young adult mean is diagnostic for osteoporosis. Bone loss associated with normal aging would be expected to increase the percentage of individuals with a T-score less than −2.5. This then causes a “left shift” in the distribution of BMD demonstrating the greater risk of osteoporotic fractures associated with aging. As such, age-related BMD comparisons are frequently used to highlight changes associated within an age group using Z-scores.
In addition to providing diagnostic and intervention thresholds, BMD testing through DXA is the main approach for assessing fracture risk.15 However, the majority of fractures occur in patients with osteopenia with T-scores ranging from −1.0 to −2.5 (Figure 7).14,15,22,23 Therefore, the use of BMD alone to assess the fracture risk and need for therapeutic intervention has a low sensitivity.21 One possible solution to capture this cohort of individuals at risk of fracture is to decrease the diagnostic BMD threshold of osteoporosis to a lower level, such as 2 SDs below the mean.21 Although this would increase the sensitivity of BMD testing to identify those at risk of fragility fracture, it would simultaneously decrease specificity and expose low-risk patients to the costs and complications of screening and therapy.22
Figure 7: Most fractures occur due to osteopenia. Although fracture rates increase with age (red line graph), the majority of fractures occur in patients with osteopenia within a T-score range of −1.0 to −2.5 (shaded bars). This highlights the significant problem of using T-scores, or bone mass density (BMD), alone to initiate treatment. Such practices fail to treat the large number of high-risk patients whose BMD only qualifies as osteopenia but have other clinical risk factors. The Fracture Risk Assessment Tool helps identify individuals most at risk of fracture using an internationally validated assessment tool that incorporates these additional risk factors. Adapted with permission from International Osteoporosis Foundation, Fracture Risk Assessment Tool Educational Slide-kit. Available at: http://www.iofbonehealth.org/health-professionals/frax.html.
Although the nontraditional modalities beyond DXA are not used regularly in assessing BMD and fracture risk, their potential role in the future warrants mentioning. Quantitative ultrasound has been shown to have similar fracture risk assessment capabilities as DXA. In addition, quantitative ultrasound is smaller, less expensive, and more mobile, making it ideal in areas of the world where DXA is not available or affordable. However, some quantitative ultrasound scanners have variable measurement parameters, making calibration and quality control difficult.24
Another widely available modality is conventional radiography. Radiographs provide good tissue contrast and have the potential for reproducing microarchitecture. However, the overlapping cortical and trabecular bone prevent reflection of the true 3-dimensional (3-D) architecture.25 Quantitative computed tomography is another diagnostic modality that has shown promise because it allows one to directly visualize the bony anatomy with high spatial resolution and detect structural abnormalities not seen with DXA.25 The high resolution in these micro-computed tomography scans has also led to the generation of T-scores similar to DXA scanning.26 The major drawback of quantitative computed tomography is the use of considerable amounts of radiation relative to other techniques.25 Magnetic resonance imaging (MRI) and micro-MRI allow for 3-D rendering as well, but without the exposure of quantitative computed tomography, making them attractive tools for analyzing trabecular bone structure. They have been used to describe the scale, shape, orientation, and connectivity or complexity of the trabecular network, which may all play a role in the 40% of bone strength not explained by BMD alone.27 Magnetic resonance imaging has also shown promise in assessing efficacy in the treatment of osteoporosis.25 Although these modalities provide meaningful data in characterizing bone quality, the need for a fracture risk assessment device that incorporates the multiple risk factors remains.
New Algorithm for Clinical Detection
The WHO Fracture Risk Assessment Tool (FRAX) is an internationally validated assessment tool that takes into account country (Figure 5), BMD, age, sex, and 8 clinical risk factors to calculate the 10-year probability of a major osteoporotic fracture (clinical vertebral, wrist, proximal humerus, or hip) and the 10-year probability of a hip fracture (Figure 8). The FRAX includes independent risk factors that, when used in combination, provide a powerful estimation of absolute fracture risk. The absolute risk of fracture is calculated in men or women using age, body mass index (BMI), and independent risk variables identified as significant contributors to osteoporotic fractures above and beyond that provided by BMD and age. The independent variables include country of residence, history of previous fracture, family history of hip fracture, smoking status, use of oral glucocorticoids, presence of rheumatoid arthritis, causes of secondary osteoporosis, and alcohol consumption of more than 3 units per day.
Figure 8: World Health Organization (WHO) Fracture Risk Assessment Tool (FRAX). In this example, a 50-year-old, thin, US Caucasian woman has a parent with a history of a fractured hip as well as current smoking, glucocorticoid, and alcohol use of 3 or more units per day. The T-score from dual-energy x-ray absorptiometry scan was −2.0. This T-score would not generally result in the clinical diagnosis of osteoporosis. The FRAX results (red box) demonstrate an 18% 10-year risk of major osteoporotic fracture of and a 10-year risk of hip fracture as 3.7%. Using the National Osteoporosis Foundation criteria (osteoporotic, or osteopenic with either a 3% or more 10-year hip fracture risk or 20% or more 10-year major osteoporosis-related fracture risk), pharmacological and nonpharmacologic treatment and activity modifications (smoking and alcohol cessation) would be recommended. Adapted with permission from International Osteoporosis Foundation, Fracture Risk Assessment Tool Educational Slide-kit. Available at: http://www.iofbonehealth.org/health-professionals/frax.html.
Incorporation of femoral neck BMD may be included in the fracture risk assessment, but it is not required. If BMD is incorporated into the risk assessment, the FRAX will simultaneously relate the patient’s age to the BMD measurement when determining fracture risk. This is important because the gradient of risk associated with BMD varies according to the patient’s age.15 Although the FRAX incorporates many independent variables, some researchers have questioned whether the FRAX is superior to more parsimonious models based on BMD and age or age with prior history of fracture on predicting fracture risk.28
Additional limitations of the FRAX should be noted. First, the FRAX does not replace clinical judgment and is not applicable to patients with osteoporotsis who are managed pharmacologically. Second, validity of the FRAX is dependent on the quality of the epidemiological data used for its formulation and does not account for other risk factors associated with osteoporotic fractures (eg, falls, visual acuity, level of physical activity, biochemical markers, or vitamin D status). The US model originally overestimated fracture risk. Readjustments of the hip and major fracture rates were completed in July 2009 based on new epidemiologic data on fractures and mortality rates in the United States (version 3).29 Third, the FRAX only accepts ages between 40 and 90 years. If a patient is younger or older, the program will compute probabilities at 40 and 90 years, respectively. Fourth, the FRAX does not account for the dose-response effects of smoking or glucocorticoid use. Smoking applies to current use only, and glucocorticoid use with oral steroids of 5 mg or more per day of a prednisone equivalent for 3 months or more. Fifth, the model uses femoral neck BMD only in g/cm2 and not BMD of the spine.
Even with these limitations, a distinct advantage is that the FRAX has the ability to predict fracture risk and determine the need for therapeutic intervention in instances where BMD testing may not be available. When computations are done without BMD data, secondary osteoporosis factors are included in the fracture risk assessment (Figure 8 [question 10]). Otherwise, the FRAX assumes that most diseases and medications, except rheumatoid arthritis, increase fracture risk by causing bone loss and calculates fracture risk using the actual BMD.
Incorporation of the FRAX into clinical practice provides an alternative to the sole application of BMD to assess fracture risk and intervention threshold. In addition, use of this tool has the potential to identify individuals with BMD values that reside in the osteopenic range but are at substantial risk of fracture. As shown in Figure 7, this cohort accounts for the majority of fractures, and although they do not have osteoporosis, these individuals may benefit greatly from therapy.
Because osteoporosis is a common disease, it must be managed at the primary care level. To accomplish the broad management of this disease, fracture risk assessment must be feasible in many primary care settings, including those without access to BMD testing.15 The FRAX can fulfill that task and can be applied in the primary care setting to postmenopausal women and men aged 50 years and older.14 The FRAX algorithm is readily accessible online and as a mobile device app for health care professionals ( http://www.shef.ac.uk/FRAX/), and information provided by the FRAX can easily be incorporated into clinical patient management (Figure 8).
In the United States, intervention thresholds have largely been based on cost effectiveness.15 The National Osteoporosis Foundation has conducted an economic analysis that suggests pharmacologic treatment would be cost-effective in patients with a 10-year hip fracture probability of of 3% or more.22 Furthermore, in the setting where BMD testing is available, the Foundation also recommends pharmacologic intervention for patients with low bone mass (T-score between −1 and −2.5 at the femoral neck or spine) and a 10-year probability of a hip fracture ⩾3% or a 10-year probability of a major osteoporosis-related fracture of 20% or more.14 A brief review of currently available pharmacologic agents is provided below, with an excellent review in the 2009 Instructional Course Lectures.17,21
For patients who meet the above criteria, 2 classes of pharmacologic agents can be used: antiresorptive and anabolic therapies. Both agents have demonstrated antifracture efficacy in randomized clinical trials.21,30 Antiresorptive agents inhibit the bone resorption activity of osteoclasts, and these medications include bisphosphonates, calcitonin, hormone replacement therapy, and selective estrogen receptor modulators.21 Use of anabolic therapy enhances production of bone mass, and this medicine class is limited to 1 agent: parathyroid hormone.21 Although use of a bisphosphonate in combination with parathyroid hormone appears plausible, a synergistic effect between the 2 has not been seen. Rather, it is often recommended that patients taking bisphosphonate therapy discontinue its use prior to beginning anabolic medication because bisphosphonates have been shown to reduce the anabolic effects of parathyroid hormone when the 2 are given simultaneously.31 However, taking a bisphosphonate after the treatment course with parathyroid hormone has been shown to prevent declines in the BMD achieved by anabolic therapy.32 In addition, nonpharmacologic therapy is used concurrently with pharmacologic agents to further reduce fracture risk. Nonpharmacologic interventions consist of calcium and vitamin D supplementation, fall prevention, hip protectors, and balance and exercise programs.21
Individuals who do not meet the FRAX-derived pharmacologic treatment threshold as listed above should be educated on interventions that maintain bone strength and reduce the risk of a future fracture. Interestingly, many of the interventions that lower fracture risk also serve to enhance overall health and well-being. The National Osteoporosis Foundation has generated several recommendations that can be given to the general population, including adequate daily intake of calcium and vitamin D, lifelong participation in regular weight-bearing and muscle-strengthening exercise, avoidance of tobacco use, identification and treatment of alcoholism, and treatment of other risk factors for fracture, such as impaired vision.14
Patients who present with a first-time fragility or low-impact fracture represent a window of opportunity to begin intervention; however, according to the National Committee on Quality Assurance, this opportunity is often neglected. The Committee analyzed the percentage of female Medicare recipients aged 67 or older who suffered a fracture and received either a BMD test or prescription treatment for osteoporosis within 6 months after the date of the fracture. The data showed that, in 2006, only 22% of these women received osteoporosis management after suffering a fracture. In contrast, 94% of Medicare recipients who suffered a myocardial infarction received treatment with a beta-blocker.33 One way for orthopedic surgeons treating fragility fractures to improve follow-up care is to send a letter that contains recommendations for evaluation of osteoporosis to the patient’s primary care provider, including an evaluation of absolute fracture risk with the FRAX rather than relying solely on the T-score from BMD testing.
- Ilich JZ, Kerstetter JE. Nutrition in bone health revisited: a story beyond calcium. J Amer Col Nut. 2000; 19(6):715–737.
- Cooper C, Campion G, Melton LJ III, . Hip fractures in the elderly: a world-wide projection. Osteoporosis Int. 1992; 2(6):285–289. doi:10.1007/BF01623184 [CrossRef]
- National Osteoporosis Foundation. America’s Bone Health: The State of Osteoporosis and Low Bone Mass in Our Nation. Washington, DC: National Osteoporosis Foundation; 2002.
- US Department of Health and Human Services. Bone Health and Osteoporosis: A Report of the Surgeon General. Rockville, MD: US Department of Health and Human Services; 2004.
- Riggs BL, Melton LJ. The worldwide problem of osteoporosis: insights afforded by epidemiology. Bone. 1995; 17:505S–511S. doi:10.1016/8756-3282(95)00258-4 [CrossRef]
- American Heart Association. Heart and Stroke Facts 1996 Statistical Supplement. Dallas, Texas: American Heart Association; 1996:1.
- American Cancer Society. Cancer Facts & Figures. Oklahoma City, Oklahoma: American Cancer Society; 1996.
- Elffors I, Allander E, Kanis JA, et al. The variable incidence of hip fracture in southern Europe: the MEDOS Study. Osteoporosis Int. 1994; 4(5):253–263. doi:10.1007/BF01623349 [CrossRef]
- Kanis JA, Johnell O, De Laet C, Jonsson B, Oden A, Ogelsby AK. International variations in hip fracture probabilities: implications for risk assessment. J Bone and Min Res. 2002; 17(7):1237–1244. doi:10.1359/jbmr.2002.17.7.1237 [CrossRef]
- Thomas PA. Racial and ethnic differences in osteoporosis. J Amer Acad Ortho Surgeons. 2007; 15:S26–S30.
- Lu-yao GL, Baron JA, Barrett JA, Fisher ES. Treatment and survival among elderly Americans with hip fractures: a population-based study. Am J Pub Health. 1994; 84:1287–1291. doi:10.2105/AJPH.84.8.1287 [CrossRef]
- Cooper C. The crippling consequences of fractures and their impact on quality of life. Am J Med. 1997; 103:12S–17S. doi:10.1016/S0002-9343(97)90022-X [CrossRef]
- Colon-Emeric C, Kuchibhatla M, Pieper C, et al. The contribution of hip fracture to risk of subsequent fracture: data from two longitudinal studies. Osteoporosis Int. 2003; 14:879–883. doi:10.1007/s00198-003-1460-x [CrossRef]
- National Osteoporosis Foundation. Clinician’s Guide to Prevention and Treatment of Osteoporosis. Washington, DC: National Osteoporosis Foundation; 2008.
- McCloskey E. FRAX Identifying people at high risk of fracture: WHO Fracture Risk Assessment Tool, a new clinical tool for informed treatment decisions. Nyon, Switzerland: International Osteoporosis Foundation; 2009.
- Burge RT, Dawson-Hughes B, Solomon D, Wong JB, King AB, Tosteson ANA. Incidence and economic burden of osteoporotic fractures in the United States, 2002–2005. J Bone Min Res. 2007; 22(3):465–475. doi:10.1359/jbmr.061113 [CrossRef]
- Gehrig LMB, Collinge C, Kaufman J, Lane JM, O’Connor MI, Tosi LL. Osteoporosis: management and densitometry for orthopaedic surgeons. AAOS Instrl Course Lect. 2009; 58:805–815.
- Assessment of fracture risk and its application to screening for postmenopausal osteoporosis: report of a WHO Study Group. WHO Technical Report Series. 1994; 843:1–129.
- International Osteoporosis Foundation. IOF Annual Report 2008. Nyon, Switzerland: International Osteoporosis Foundation; 2008.
- NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis and Therapy. JAMA. 2001; 285:785–795.
- Gehrig LMB, Lane J, O’Conner M. Osteoporosis: management and treatment strategies for orthopaedic surgeons. AAOS Instructional Course Lectures. 2009; 58:817–832.
- Dawson-Hughes B, Tosteson ANA, Melton LJ III, et al. Implications of absolute fracture risk assessment for osteoporosis practice guidelines in the USA. Osteoporosis Int. 2008; 19(4):449–458. doi:10.1007/s00198-008-0559-5 [CrossRef]
- Siris ES, Chen YT, Abbott TA, et al. Bone mineral density thresholds for pharmacological intervention to prevent fractures. Arch Intern Med. 2004; 164(10):1108–1112. doi:10.1001/archinte.164.10.1108 [CrossRef]
- Moayyeri A, Adams JE, Adler RA, et al. Quantitative ultrasound of the heel and fracture risk assessment: an updated meta-analysis. Osteoporosis Int. 2012; 23:143–153. doi:10.1007/s00198-011-1817-5 [CrossRef]
- Bauer JS, Link TM. Advances in osteoporosis imaging. Eur J Radiol. 2009; 71:440–449. doi:10.1016/j.ejrad.2008.04.064 [CrossRef]
- Khoo BCC, Brown K, Cann C, et al. Comparison of QCT-derived and DXA-derived areal bone mineral density and T scores. Osteoporosis Int. 2009; 20:1539–1545. doi:10.1007/s00198-008-0820-y [CrossRef]
- Wehrli F, Saha P, Gomberg B, et al. Role of magnetic resonance for assessing structure and function of trabecular bone. Top Magn Reson Imaging. 2002; 13:335–355. doi:10.1097/00002142-200210000-00005 [CrossRef]
- Ensrud K, Lui L, Taylor B, et al. A comparison of prediction models for fractures in older women. Arch Intern Med. 2009; 169(22):2087–2094. doi:10.1001/archinternmed.2009.404 [CrossRef]
- Ettinger B, Black DM, Dawson-Hughes B, Pressman AR, Melton L III, . Updated fracture incidence rates for the US version of FRAX. Osteoporosis Int. 2010; 21:25–33. doi:10.1007/s00198-009-1032-9 [CrossRef]
- Bouxsein ML, Kaufman J, Tosi L, Cummings S, Lane J, Johnell O. Recommendations for optimal care of the fragility fracture patient to reduce the risk of future fracture. J Am Acad Orthop Surg. 2004; 12:385–395.
- Black DM, Greenspan SL, Ensrud KE, et al. The effects of parathyroid hormone and alen-dronate alone or in combination in postmenopausal osteoporosis. N Eng J Med. 2003; 349:1207–1215. doi:10.1056/NEJMoa031975 [CrossRef]
- Kurland ES, Heller SL, Diamond B, McMahon DJ, Cosman F, Bilezikian JP. The importance of bisphosphonate therapy in maintaining bone mass in men after therapy with teriparatide [human parathyroid hormone (1–34)]. Osteoporosis Int. 2004; 15:992–997. doi:10.1007/s00198-004-1636-z [CrossRef]
- National Committee for Quality Assurance. The State of Health Care Quality 2007. Washington, DC: National Committee for Quality Assurance, 2007.