Bone mineral density (BMD) is the most important predictor of fracture risk. We performed the largest meta-analysis to date on lumbar spine and femoral neck BMD, including 17 genome-wide association studies and 32,961 individuals of European and East Asian ancestry. We tested the top-associated BMD markers for replication in 50,933 independent subjects and for risk of low-trauma fracture in 31,016 cases and 102,444 controls. We identified 56 loci (32 novel)associated with BMD atgenome-wide significant level (P<5×10−8). Several of these factors cluster within the RANK-RANKL-OPG, mesenchymal-stem-cell differentiation, endochondral ossification and the Wnt signalling pathways. However, we also discovered loci containing genes not known to play a role in bone biology. Fourteen BMD loci were also associated with fracture risk (P<5×10−4, Bonferroni corrected), of which six reached P<5×10−8 including: 18p11.21 (C18orf19), 7q21.3 (SLC25A13), 11q13.2 (LRP5), 4q22.1 (MEPE), 2p16.2 (SPTBN1) and 10q21.1 (DKK1). These findings shed light on the genetic architecture and pathophysiological mechanisms underlying BMD variation and fracture susceptibility.

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Since the publication of the Osteoporosis Canada guidelines in 2002, there has been a paradigm shift in the prevention and treatment of osteoporosis and fractures.1,2 The focus now is on preventing fragility fractures and their negative consequences, rather than on treating low bone mineral density, which is viewed as only one of several risk factors for fracture. Given that certain clinical factors increase the risk of fracture independent of bone mineral density, it is important to take an integrated approach and to base treatment decisions on the absolute risk of fracture. Current data suggest that many patients with fractures do not undergo appropriate assessment or treatment.3 To address this care gap for high-risk patients, the 2010 guidelines concentrate on the assessment and management of women and men over age 50 who are at high risk of fragility fractures and the integration of new tools for assessing the 10-year risk of fracture into overall management. Burden and care gapsFragility fractures, the consequence of osteoporosis, are responsible for excess mortality, morbidity, chronic pain, admission to institutions and economic costs. [4][5][6] They represent 80% of all fractures in menopausal women over age 50.3 Those with hip or vertebral fractures have substantially increased risk of death after the fracture.5 Postfracture mortality and institutionalization rates are higher for men than for women. 7Despite the high prevalence of fragility fractures in the Canadian population and the knowledge that fractures predict future fractures, 8 fewer than 20% of women 3,9 and 10% of men 10 receive therapies to prevent further fractures. These statistics contrast sharply with the situation for cardiovascular disease, where 75% of patients who have had myocardial infarction receive β-blockers to prevent another event. 11 Scope of the guidelinesThe target population for these guidelines is women and men over age 50, because of the overall burden of illness in that age group. As a consequence, we focused our systematic literature reviews on this population. The application of these guidelines to children and young adults, as well as high-risk groups such as transplant recipients, was considered, but indepth reviews of conditions that increase risk were largely beyond the scope of these guidelines. Development of the guidelinesThe development of these guidelines followed the Appraisal of Guidelines, Research and Evaluation (AGREE) framework. 12 We surveyed primary care physicians, patients, osteoporosis specialists from various disciplines, radiologists, allied health professionals and health policy-makers to identify priorities for these guidelines. We then conducted system-

The trabecular bone score (TBS) is a gray-level textural metric that can be extracted from the two-dimensional lumbar spine dualenergy X-ray absorptiometry (DXA) image. TBS is related to bone microarchitecture and provides skeletal information that is not captured from the standard bone mineral density (BMD) measurement. Based on experimental variograms of the projected DXA image, TBS has the potential to discern differences between DXA scans that show similar BMD measurements. An elevated TBS value correlates with better skeletal microstructure; a low TBS value correlates with weaker skeletal microstructure. Lumbar spine TBS has been evaluated in cross-sectional and longitudinal studies. The following conclusions are based upon publications reviewed in this article: 1) TBS gives lower values in postmenopausal women and in men with previous fragility fractures than their nonfractured counterparts; 2) TBS is complementary to data available by lumbar spine DXA measurements; 3) TBS results are lower in women who have sustained a fragility fracture but in whom DXA does not indicate osteoporosis or even osteopenia; 4) TBS predicts fracture risk as well as lumbar spine BMD measurements in postmenopausal women; 5) efficacious therapies for osteoporosis differ in the extent to which they influence the TBS; 6) TBS is associated with fracture risk in individuals with conditions related to reduced bone mass or bone quality. Based on these data, lumbar spine TBS holds promise as an emerging technology that could well become a valuable clinical tool in the diagnosis of osteoporosis and in fracture risk assessment.

The measurement of BMD by dual-energy X-ray absorptiometry (DXA) is the ''gold standard'' for diagnosing osteoporosis but does not directly reflect deterioration in bone microarchitecture. The trabecular bone score (TBS), a novel gray-level texture measurement that can be extracted from DXA images, correlates with 3D parameters of bone microarchitecture. Our aim was to evaluate the ability of lumbar spine TBS to predict future clinical osteoporotic fractures. A total of 29,407 women 50 years of age or older at the time of baseline hip and spine DXA were identified from a database containing all clinical results for the Province of Manitoba, Canada. Health service records were assessed for the incidence of nontraumatic osteoporotic fracture codes subsequent to BMD testing (mean follow-up 4.7 years). Lumbar spine TBS was derived for each spine DXA examination blinded to clinical parameters and outcomes. Osteoporotic fractures were identified in 1668 (5.7%) women, including 439 (1.5%) spine and 293 (1.0%) hip fractures. Significantly lower spine TBS and BMD were identified in women with major osteoporotic, spine, and hip fractures (all p < 0.0001). Spine TBS and BMD predicted fractures equally well, and the combination was superior to either measurement alone ( p < 0.001). Spine TBS predicts osteoporotic fractures and provides information that is independent of spine and hip BMD. Combining the TBS trabecular texture index with BMD incrementally improves fracture prediction in postmenopausal women. ß