Patterns of Load-to-Strength Ratios Along the Spine in a Population-Based Cohort to Evaluate the Contribution of Spinal Loading to Vertebral Fractures

Vertebral fractures (VFx) are common among older adults. Epidemiological studies report high occurrence of VFx at mid-thoracic and thoracolumbar regions of the spine; however, reasons for this observation remain poorly understood. Prior reports of high ratios of spinal loading to vertebral strength in the thoracolumbar region suggest a possible biomechanical explanation. However, no studies have evaluated load-to-strength ratios (LSRs) throughout the spine for a large number of activities in a sizeable cohort. Thus, we performed a cross-sectional study in a sample of adult men and women from a population-based cohort to: 1) determine which activities cause the largest vertebral LSRs, and 2) examine patterns of LSRs along the spine for these high-load activities. We used subject-specific musculoskeletal models of the trunk to determine vertebral compressive loads for 109 activities in 250 individuals (aged 41 to 90 years, 50% women) from the Framingham Heart Study. Vertebral compressive strengths from T₄ to L₄ were calculated from computed tomography–based vertebral size and bone density measurements. We determined which activities caused maximum LSRs at each of these spinal levels. We identified nine activities that accounted for >95% of the maximum LSRs overall and at least 89.6% at each spinal level. The activity with the highest LSR varied by spinal level, and three distinct spinal regions could be identified by the activity producing maximum LSRs: lateral bending with a weight in one hand (upper thoracic), holding weights with elbows flexed (lower thoracic), and forward flexion with weight (lumbar). This study highlights the need to consider a range of lifting, holding, and non-symmetric activities when evaluating vertebral LSRs. Moreover, we identified key activities that produce higher loading in multiple regions of the spine. These results provide the first guidance on what activities to consider when evaluating vertebral load-to-strength ratios in future studies, including those examining dynamic motions and the biomechanics of VFx. © 2020 American Society for Bone and Mineral Research (ASBMR).     

Assessment of incident spine and hip fractures in women and men using finite element analysis of CT scans

Finite element analysis of computed tomography (CT) scans provides noninvasive estimates of bone strength at the spine and hip. To further validate such estimates clinically, we performed a 5‐year case‐control study of 1110 women and men over age 65 years from the AGES‐Reykjavik cohort (case = incident spine or hip fracture; control = no incident spine or hip fracture). From the baseline CT scans, we measured femoral and vertebral strength, as well as bone mineral density (BMD) at the hip (areal BMD only) and lumbar spine (trabecular volumetric BMD only). We found that for incident radiographically confirmed spine fractures (n = 167), the age‐adjusted odds ratio for vertebral strength was significant for women (2.8, 95% confidence interval [CI] 1.8 to 4.3) and men (2.2, 95% CI 1.5 to 3.2) and for men remained significant (p = 0.01) independent of vertebral trabecular volumetric BMD. For incident hip fractures (n = 171), the age‐adjusted odds ratio for femoral strength was significant for women (4.2, 95% CI 2.6 to 6.9) and men (3.5, 95% CI 2.3 to 5.3) and remained significant after adjusting for femoral neck areal BMD in women and for total hip areal BMD in both sexes; fracture classification improved for women by combining femoral strength with femoral neck areal BMD (p = 0.002). For both sexes, the probabilities of spine and hip fractures were similarly high at the BMD‐based interventional thresholds for osteoporosis and at corresponding preestablished thresholds for “fragile bone strength” (spine: women ≤ 4500 N, men ≤ 6500 N; hip: women ≤ 3000 N, men ≤ 3500 N). Because it is well established that individuals over age 65 years who have osteoporosis at the hip or spine by BMD criteria should be considered at high risk of fracture, these results indicate that individuals who have fragile bone strength at the hip or spine should also be considered at high risk of fracture. © 2014 American Society for Bone and Mineral Research.     

Understanding Bone Strength Is Not Enough

Increases in fracture risk beyond what are expected from bone mineral density (BMD) are often attributed to poor “bone quality,” such as impaired bone tissue strength. Recent studies, however, have highlighted the importance of tissue material properties other than strength, such as fracture toughness. Here we review the concepts behind failure properties other than strength and the physical mechanisms through which they cause mechanical failure: strength describes failure from a single overload; fracture toughness describes failure from a modest load combined with a preexisting flaw or damage; and fatigue strength describes failure from thousands to millions of cycles of small loads. In bone, these distinct failure mechanisms appear to be more common in some clinical fractures than others. For example, wrist fractures are usually the result of a single overload, the failure mechanism dominated by bone strength, whereas spinal fractures are rarely the result of a single overload, implicating multiple loading cycles and increased importance of fatigue strength. The combination of tissue material properties and failure mechanisms that lead to fracture represent distinct mechanistic pathways, analogous to molecular pathways used to describe cell signaling. Understanding these distinct mechanistic pathways is necessary because some characteristics of bone tissue can increase fracture risk by impairing fracture toughness or fatigue strength without impairing bone tissue strength. Additionally, mechanistic pathways to failure associated with fracture toughness and fatigue involve multiple loading events over time, raising the possibility that a developing fracture could be detected and interrupted before overt failure of a bone. Over the past two decades there have been substantial advancements in fracture prevention by understanding bone strength and fractures caused by a single load, but if we are to improve fracture risk prevention beyond what is possible now, we must consider material properties other than strength. © 2017 American Society for Bone and Mineral Research.     

Fracture Risk Predictions Based on Statistical Shape and Density Modeling of the Proximal Femur

Increased risk of skeletal fractures due to bone mass loss is a major public health problem resulting in significant morbidity and mortality, particularly in the case of hip fractures. Current clinical methods based on two‐dimensional measures of bone mineral density (areal BMD or aBMD) are often unable to identify individuals at risk of fracture. We investigated predictions of fracture risk based on statistical shape and density modeling (SSDM) methods using a case‐cohort sample of individuals from the Osteoporotic Fractures in Men (MrOS) study. Baseline quantitative computed tomography (QCT) data of the right femur were obtained for 513 individuals, including 45 who fractured a hip during follow‐up (mean 6.9 year observation, validated by physician review). QCT data were processed for 450 individuals (including 40 fracture cases) to develop individual models describing three‐dimensional bone geometry and density distribution. Comparison of mean fracture and non‐case models indicated complex structural differences that appear to be responsible for resistance to hip fracture. Logistic regressions were used to model the relation of baseline hip BMD and SSDM weighting factors to the occurrence of hip fracture. Area under the receiver operating characteristic (ROC) curve (AUC) for a prediction model based on weighting factors and adjusted by age was significantly greater than AUC for a prediction model based on aBMD and age (0.94 versus 0.83, respectively). The SSDM‐based prediction model adjusted by age correctly identified 55% of the fracture cases (and 94.7% of the non‐cases), whereas the clinical standard aBMD correctly identified 10% of the fracture cases (and 91.3% of the non‐cases). SSDM identifies subtle changes in combinations of structural bone traits (eg, geometric and BMD distribution traits) that appear to indicate fracture risk. Investigation of important structural differences in the proximal femur between fracture and no‐fracture cases may lead to improved prediction of those at risk for future hip fracture. © 2014 American Society for Bone and Mineral Research.     

Type 2 Diabetes and Risk of Hip Fractures and Non‐Skeletal Fall Injuries in the Elderly: A Study From the Fractures and Fall Injuries in the Elderly Cohort (FRAILCO)

Questions remain about whether the increased risk of fractures in patients with type 2 diabetes (T2DM) is related mainly to increased risk of falling or to bone‐specific properties. The primary aim of this study was to investigate the risk of hip fractures and non‐skeletal fall injuries in older men and women with and without T2DM. We included 429,313 individuals (aged 80.8 ± 8.2 years [mean ± SD], 58% women) from the Swedish registry “Senior Alert” and linked the data to several nationwide registers. We identified 79,159 individuals with T2DM (45% with insulin [T2DM‐I], 41% with oral antidiabetics [T2DM‐O], and 14% with no antidiabetic treatment [T2DM‐none]) and 343,603 individuals without diabetes. During a follow‐up of approximately 670,000 person‐years, we identified in total 36,132 fractures (15,572 hip fractures) and 20,019 non‐skeletal fall injuries. In multivariable Cox regression models where the reference group was patients without diabetes and the outcome was hip fracture, T2DM‐I was associated with increased risk (adjusted hazard ratio (HR) [95% CI] 1.24 [1.16–1.32]), T2DM‐O with unaffected risk (1.03 [0.97–1.11]), and T2DM‐none with reduced risk (0.88 [0.79–0.98]). Both the diagnosis of T2DM‐I (1.22 [1.16–1.29]) and T2DM‐O (1.12 [1.06–1.18]) but not T2DM‐none (1.07 [0.98–1.16]) predicted non‐skeletal fall injury. The same pattern was found regarding other fractures (any, upper arm, ankle, and major osteoporotic fracture) but not for wrist fracture. Subset analyses revealed that in men, the risk of hip fracture was only increased in those with T2DM‐I, but in women, both the diagnosis of T2DM‐O and T2DM‐I were related to increased hip fracture risk. In conclusion, the risk of fractures differs substantially among patients with T2DM and an increased risk of hip fracture was primarily found in insulin‐treated patients, whereas the risk of non‐skeletal fall injury was consistently increased in T2DM with any diabetes medication. © 2016 American Society for Bone and Mineral Research.     

Spinal Loading Patterns From Biomechanical Modeling Explain the High Incidence of Vertebral Fractures in the Thoracolumbar Region

Vertebral fractures occur most frequently in the mid‐thoracic and thoracolumbar regions of the spine, yet the reasons for this site‐specific occurrence are not known. Our working hypothesis is that the locations of vertebral fracture may be explained by the pattern of spine loading, such that during daily activities the mid‐thoracic and thoracolumbar regions experience preferentially higher mechanical loading compared to other spine regions. To test this hypothesis, we used a female musculoskeletal model of the full thoracolumbar spine and rib cage to estimate the variation in vertebral compressive loads and associated factor‐of‐risk (load‐to‐strength ratio) throughout the spine for 119 activities of daily living, while also parametrically varying spine curvature (high, average, low, and zero thoracic kyphosis models). We found that nearly all activities produced loading peaks in the thoracolumbar and lower lumbar regions of the spine, but that the highest factor‐of‐risk values generally occurred in the thoracolumbar region of the spine because these vertebrae had lower compressive strength than vertebrae in the lumbar spine. The peaks in compressive loading and factor‐of‐risk in the thoracolumbar region were accentuated by increasing thoracic kyphosis. Activation of the multifidus muscle fascicles selectively in the thoracolumbar region appeared to be the main contributor to the relatively high vertebral compressive loading in the thoracolumbar spine. In summary, by using advanced musculoskeletal modeling to estimate vertebral loading throughout the spine, this study provides a biomechanical mechanism for the higher incidence of fractures in thoracolumbar vertebrae compared to other spinal regions. © 2017 American Society for Bone and Mineral Research.     

The Effect of a Screening and Treatment Program for the Prevention of Fractures in Older Women: A Randomized Pragmatic Trial

Population screening for fracture risk may reduce the fracture incidence. In this randomized pragmatic trial, the SALT Osteoporosis Study (SOS), we studied whether screening for fracture risk and subsequent treatment in primary care can reduce fractures compared with usual care. A total of 11,032 women aged 65 to 90 years with ≥1 clinical risk factor for fractures were individually randomized to screening (n = 5575) or usual care (n = 5457). Participants in the screening group underwent a screening program, including bone densitometry and vertebral fracture assessment. Participants with a high 10-year fracture probability (FRAX) or a vertebral fracture were offered treatment with anti-osteoporosis medication by their general practitioner. Incident fractures as reported by questionnaires were verified with medical records. Follow-up was completed by 94% of the participants (mean follow-up = 3.7 years). Of the 5575 participants in the screening group, 1417 (25.4%) had an indication for anti-osteoporosis medication. Screening and subsequent treatment had no statistically significant effect on the primary outcome fracture (hazard ratio [HR] = 0.97; 95% confidence interval [CI] 0.87–1.08), nor on the secondary outcomes osteoporotic fractures (HR = 0.91; 95% CI 0.81–1.03), major osteoporotic fractures (HR = 0.91; 95% CI 0.80–1.04), hip fractures (HR = 0.91; 95% CI 0.71–1.15), falls (odds ratio [OR] = 0.91; 95% CI 0.72–1.15), or mortality (HR = 1.03; 95% CI 0.91–1.17). Post hoc explorative finding suggested that screening might be most effective after a recent fracture (HR = 0.65; 95% CI 0.44–0.96 for major osteoporotic fractures and HR = 0.38; 95% CI 0.18–0.79 for hip fractures). The results of this study might have been compromised by nonparticipation and medication nonadherence in the screening group. Overall, this study does not provide sufficient indications to consider screening for fracture prevention. However, we cannot exclude its clinical relevance to reduce (major) osteoporotic fractures and hip fractures because of the relatively small number of women with a treatment indication in the intervention group. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.     

The Initial Slope of the Variogram,Foundation of the Trabecular Bone Score,Is Not or Is Poorly Associated With Vertebral Strength

Trabecular bone score (TBS) rests on the textural analysis of dual‐energy X‐ray absorptiometry (DXA) to reflect the decay in trabecular structure characterizing osteoporosis. Yet, its discriminative power in fracture studies remains incomprehensible because prior biomechanical tests found no correlation with vertebral strength. To verify this result possibly owing to an unrealistic setup and to cover a wide range of loading scenarios, the data from three previous biomechanical studies using different experimental settings were used. They involved the compressive failure of 62 human lumbar vertebrae loaded 1) via intervertebral discs to mimic the in vivo situation (“full vertebra”); 2) via the classical endplate embedding (“vertebral body”); or 3) via a ball joint to induce anterior wedge failure (“vertebral section”). High‐resolution peripheral quantitative computed tomography (HR‐pQCT) scans acquired from prior testing were used to simulate anterior‐posterior DXA from which areal bone mineral density (aBMD) and the initial slope of the variogram (ISV), the early definition of TBS, were evaluated. Finally, the relation of aBMD and ISV with failure load (F_exp) and apparent failure stress (σ_exp) was assessed, and their relative contribution to a multilinear model was quantified via ANOVA. We found that, unlike aBMD, ISV did not significantly correlate with F_exp and σ_exp, except for the “vertebral body” case (r² = 0.396, p = 0.028). Aside from the “vertebra section” setup where it explained only 6.4% of σ_exp (p = 0.037), it brought no significant improvement to aBMD. These results indicate that ISV, a replica of TBS, is a poor surrogate for vertebral strength no matter the testing setup, which supports the prior observations and raises a fortiori the question of the deterministic factors underlying the statistical relationship between TBS and vertebral fracture risk. © 2015 American Society for Bone and Mineral Research.     

HR-pQCT Measures of Bone Microarchitecture Predict Fracture: Systematic Review and Meta-Analysis

High-resolution peripheral quantitative computed tomography (HR-pQCT) is a noninvasive imaging modality for assessing volumetric bone mineral density (vBMD) and microarchitecture of cancellous and cortical bone. The objective was to (1) assess fracture-associated differences in HR-pQCT bone parameters; and (2) to determine if HR-pQCT is sufficiently precise to reliably detect these differences in individuals. We systematically identified 40 studies that used HR-pQCT (39/40 used XtremeCT scanners) to assess 1291 to 3253 and 3389 to 10,687 individuals with and without fractures, respectively, ranging in age from 10.9 to 84.7 years with no comorbid conditions. Parameters describing radial and tibial bone density, microarchitecture, and strength were extracted and percentage differences between fracture and control subjects were estimated using a random effects meta-analysis. An additional meta-analysis of short-term in vivo reproducibility of bone parameters assessed by XtremeCT was conducted to determine whether fracture-associated differences exceeded the least significant change (LSC) required to discern measured differences from precision error. Radial and tibial HR-pQCT parameters, including failure load, were significantly altered in fracture subjects, with differences ranging from −2.6% (95% confidence interval [CI] −3.4 to −1.9) in radial cortical vBMD to −12.6% (95% CI −15.0 to −10.3) in radial trabecular vBMD. Fracture-associated differences reported by prospective studies were consistent with those from retrospective studies, indicating that HR-pQCT can predict incident fracture. Assessment of study quality, heterogeneity, and publication biases verified the validity of these findings. Finally, we demonstrated that fracture-associated deficits in total and trabecular vBMD and certain tibial cortical parameters can be reliably discerned from HR-pQCT-related precision error and can be used to detect fracture-associated differences in individual patients. Although differences in other HR-pQCT measures, including failure load, were significantly associated with fracture, improved reproducibility is needed to ensure reliable individual cross-sectional screening and longitudinal monitoring. In conclusion, our study supports the use of HR-pQCT in clinical fracture prediction. © 2019 American Society for Bone and Mineral Research.     

Clinical Performance of the Updated Trabecular Bone Score (TBS) Algorithm,Which Accounts for the Soft Tissue Thickness: The OsteoLaus Study

Regional soft tissue may have a noise effect on trabecular bone score (TBS) and eventually alter its estimate. The current TBS software (TBS iNsight®) is based on an algorithm accounting for body mass index (BMI) (TBS_v3.03). We aimed to explore the updated TBS algorithm that accounts for soft tissue thickness (TBS_v4.0). This study was embedded in the OsteoLaus cohort of women in Lausanne, Switzerland. Hip and lumbar spine (LS) dual-energy X-ray absorptiometry (DXA) scans were performed using Discovery A System (Hologic). The incident major osteoporotic fractures (MOFs) were assessed from vertebral fracture assessments using Genant's method (vertebral MOF) or questionnaires (nonvertebral MOF). We assessed the correlations of bone mineral density (BMD) or TBS with body composition parameters; MOF prediction ability of both versions of TBS; and the differences between Fracture Risk Assessment Tool (FRAX) adjusted for TBS_v3.03 or TBS_v4.0. In total, 1362 women with mean ± SD age 64.4 ± 7.5 years and mean ± SD BMI 25.9 ± 4.5 kg/m² were followed for 4.4 years and 132 experienced an MOF. All the anthropometric measurements of our interest were positively correlated with LS, femoral neck, or hip BMD and TBS_v4.0; whereas with TBS_v3.03 their correlations were negative. In the models adjusted for age, soft tissue thickness, osteoporotic treatment, and LS-BMD, for each SD decline in TBS_v3.03, there was a 43% (OR 1.43; 95% CI, 1.12 to 1.83) increase in the odds of having MOF; whereas for each SD decline in TBS_v4.0, there was a 54% (OR 1.54; 95% CI, 1.18 to 2.00) increase in the odds of having an MOF. Both FRAXs were very strongly correlated and the mild differences were present in the already high-risk women for MOF. This study shows that TBS_v4.0 overcomes the debatable residual negative correlation of the current TBS with body size and composition parameters, postulating itself as free from the previously acknowledged technical limitation of TBS. © 2019 American Society for Bone and Mineral Research.     

Heterogeneity and Spatial Distribution of Intravertebral Trabecular Bone Mineral Density in the Lumbar Spine Is Associated With Prevalent Vertebral Fracture

The spatial heterogeneity in trabecular bone density within the vertebral centrum is associated with vertebral strength and could explain why volumetric bone mineral density (vBMD) exhibits low sensitivity in identifying fracture risk. This study evaluated whether the heterogeneity and spatial distribution of trabecular vBMD are associated with prevalent vertebral fracture. We examined the volumetric quantitative computed tomography (QCT) scans of the L₃ vertebra in 148 participants in the Framingham Heart Study Multidetector CT study. Of these individuals, 37 were identified as cases of prevalent fracture, and 111 were controls, matched on sex and age with three controls per case. vBMD was calculated within 5-mm contiguous cubic regions of the centrum. Two measures of heterogeneity were calculated: (i) interquartile range (IQR); and (ii) quartile coefficient of variation (QCV). Ratios in the spatial distributions of the trabecular vBMD were also calculated: anterior/posterior, central/outer, superior/mid-transverse, and inferior/mid-transverse. Heterogeneity and spatial distributions were compared between cases and controls using Wilcoxon rank sum tests and t tests and tested for association with prevalent fractures with conditional logistic regressions independent of integral vBMD. Prevalent fracture cases had lower mean ± SD integral vBMD (134 ± 38 versus165 ± 42 mg/cm³, p < .001), higher QCV (0.22 ± 0.13 versus 0.17 ± 0.09, p = .003), and lower anterior/posterior rBMD (0.65 ± 0.13 versus 0.78 ± 0.16, p < .001) than controls. QCV was positively associated with increased odds of prevalent fracture (OR 1.61; 95% CI, 1.04 to 2.49; p = .034), but this association was not independent of integral vBMD (p = .598). Increased anterior/posterior trabecular vBMD ratio was associated with decreased odds of prevalent fracture independent of integral vBMD (OR 0.38; 95% CI, 0.20 to 0.71; p = .003). In conclusion, increased trabecular vBMD in the anterior versus posterior centrum, but not trabecular vBMD heterogeneity, was associated with decreased risk of prevalent fracture independent of integral vBMD. Regional measurements of trabecular vBMD could aid in determining the risk and underlying mechanisms of vertebral fracture. © 2019 American Society for Bone and Mineral Research.     

Cost‐Effectiveness of Osteoporosis Screening Strategies for Men

Osteoporosis affects many men, with significant morbidity and mortality. However, the best osteoporosis screening strategies for men are unknown. We developed an individual‐level state‐transition cost‐effectiveness model with a lifetime time horizon to identify the cost‐effectiveness of different osteoporosis screening strategies for US men involving various screening tests (dual‐energy X‐ray absorptiometry [DXA]; the Osteoporosis Self‐Assessment Tool [OST]; or a fracture risk assessment strategy using age, femoral neck bone mineral density [BMD], and Vertebral Fracture Assessment [VFA]); screening initiation ages (50, 60, 70, or 80 years); and repeat screening intervals (5 years or 10 years). In base‐case analysis, no screening was a less effective option than all other strategies evaluated; furthermore, no screening was more expensive than all strategies that involved screening with DXA or the OST risk assessment instrument, and thus no screening was “dominated” by screening with DXA or OST at all evaluated screening initiation ages and repeat screening intervals. Screening strategies that most frequently appeared as most cost‐effective in base‐case analyses and one‐way sensitivity analyses when assuming willingness‐to‐pay of $50,000/quality‐adjusted life‐year (QALY) or $100,000/QALY included screening initiation at age 50 years with the fracture risk assessment strategy and repeat screening every 10 years; screening initiation at age 50 years with fracture risk assessment and repeat screening every 5 years; and screening initiation at age 50 years with DXA and repeat screening every 5 years. In conclusion, expansion of osteoporosis screening for US men to initiate routine screening at age 50 or 60 years would be expected to be effective and of good value for improving health outcomes. A fracture risk assessment strategy using variables of age, femoral neck BMD, and VFA is likely to be the most effective of the evaluated strategies within accepted cost‐effectiveness parameters. DXA and OST are also reasonable screening options, albeit likely slightly less effective than the evaluated fracture risk assessment strategy. © 2016 American Society for Bone and Mineral Research.     

Total Hip Bone Mineral Density as an Indicator of Fracture Risk in Bisphosphonate-Treated Patients in a Real-World Setting

Bone mineral density (BMD) is an established measure used to diagnose patients with osteoporosis. In clinical trials, change in BMD has been shown to provide a reliable estimate of fracture risk reduction, and achieved BMD T-score has been shown to reflect the near-term risk of fracture. We aimed to test the association between BMD T-score and fracture risk in patients treated for osteoporosis in a real-world setting. This retrospective, observational cohort study included Swedish females aged ≥55 years who had a total hip BMD measurement at one of three participating clinics. Patients were separated into two cohorts: bisphosphonate-treated and bisphosphonate-naïve prior to BMD measurement, stratified by age and prior nonvertebral fracture status. The primary outcome was cumulative incidence of clinical fractures within 24 months of BMD measurement, with other fracture types included as secondary outcomes. Associations between T-score and fracture risk were estimated using proportional hazards regression and restricted cubic splines. A total of 15,395 patients were analyzed: 11,973 bisphosphonate-naïve and 3422 bisphosphonate-treated. In the 24 months following BMD measurement, 6.3% (95% confidence interval [CI], 5.9–6.7) of bisphosphonate-naïve and 8.4% (95% CI, 7.5–9.4) of bisphosphonate-treated patients experienced a clinical fracture. Strong inverse relationships between BMD T-score and fracture incidence were observed in both cohorts. Among bisphosphonate-naïve patients, this relationship appeared to plateau around T-score −1.5, indicating smaller marginal reductions in fracture risk above this value; bisphosphonate-treated patients showed a more consistent marginal change in fracture risk across the evaluated T-scores (−3.0 to –0.5). Trends remained robust regardless of age and prior fracture status. This real-world demonstration of a BMD–fracture risk association in both bisphosphonate-naïve and bisphosphonate-treated patients extends evidence from clinical trials and recent meta-regressions supporting the suitability of total hip BMD as a meaningful outcome for the clinical management of patients with osteoporosis. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).     

Physical Activity and Psychosocial Factors Associated With Risk of Future Fractures in Middle-Aged Men and Women

Identification of risk factors for fractures is important for improving public health. We aimed to identify which factors related to physical activity and psychosocial situation were associated with incident fractures among 30,446 middle-aged women and men, followed from 1991–1996 to 2016, in a prospective population-based cohort study. The association between the baseline variables and first incident fracture was assessed by Cox regression models, and significant risk factors were summed into fracture risk scores. Any first incident fracture affecting spine, thoracic cage, arms, shoulders, hands, pelvis, hips, or legs was obtained from the National Patient Register, using the unique personal identity number of each citizen. A total of 8240 subjects (27%) had at least one fracture during the follow-up of median 20.7 years. Age, female sex, body mass index, previous fracture, reported family history of fracture >50 years (all p < .001), low leisure-time physical activity (p = .018), heavy work (p = .024), living alone (p = .002), smoking (p < .001), and no or high alcohol consumption (p = .005) were factors independently associated with incident fracture. The fracture risk score (0–9 points) was strongly associated with incident fracture (p for trend <.001). Among men without risk factors, the incidence rate was 5.3/1000 person-years compared with 23.2 in men with six or more risk factors (hazard ratio [HR] = 5.5; 95% confidence interval [CI] 3.7–8.2). Among women with no risk factors, the incidence rate was 10.7 compared with 28.4 in women with six or more risk factors (HR = 3.1; 95% CI 2.4–4.0). Even moderate levels of leisure-time physical activity in middle age are associated with lower risk of future fractures. In contrast, heavy work, living alone, smoking, and no or high alcohol consumption increase the risk of fracture. Our results emphasize the importance of these factors in public health initiatives for fracture prevention. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).     

Incidence of Subsequent Hip Fracture and Mortality in Elderly Patients: A Multistate Population-Based Cohort Study in Eastern Spain

Osteoporotic hip fractures in older people may confer an increased risk of subsequent hip fractures and death. The aim of this study was to estimate the cumulative incidence of both recurrent hip fracture and death in the Valencia region. We followed a cohort of 34,491 patients aged ≥65 years who were discharged alive from Valencia Health System hospitals after an osteoporotic hip fracture between 2008 and 2015, until death or end of study (December 31, 2016). Two Bayesian illness-death models were applied to estimate the cumulative incidences of recurrent hip fracture and death by sex, age, and year of discharge. We estimated 1-year cumulative incidences of recurrent hip fracture at 2.5% in women and 2.3% in men, and 8.3% and 6.6%, respectively, at 5 years. Cumulative incidences of total death were 18.3% in women and 28.6% in men at 1 year, and 51.2% and 69.8% at 5 years. One-year probabilities of death after recurrent hip fracture were estimated at 26.8% and 43.8%, respectively, and at 57.3% and 79.2% at 5 years. Our analysis showed an increasing trend in the 1-year cumulative incidence of recurrent hip fracture from 2008 to 2015, but a decreasing trend in 1-year mortality. Male sex and age at discharge were associated with increased risk of death. Women showed higher incidence of subsequent hip fracture than men although they were at the same risk of recurrent hip fracture. Probabilities of death after recurrent hip fracture were higher than those observed in the general population. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).     

Comparison of Vertebral and Femoral Strength Between White and Asian Adults Using Finite Element Analysis of Computed Tomography Scans

Given non-optimal testing rates for dual-energy X-ray absorptiometry (DXA) and the high use of computed tomography (CT) in some Asian countries, biomechanical computed tomography analysis (BCT)-based bone strength testing, which utilizes previously taken clinical CT scans, may improve osteoporosis testing rates. However, an understanding of ethnic differences in such bone strength measurements between Whites and Asians is lacking, which is an obstacle to clinical interpretation. Using previously taken CT and DXA scans, we analyzed bone strength and bone mineral density (BMD) at the hip and spine in two sex- and age-matched community-based cohorts, aged 40 to 80 years: Whites (Rochester, MN, USA) and Koreans (Seoul, South Korea). For both the spine and femur, the age dependence of bone strength was similar for both groups, White (n = 371; women n = 202, 54.5%) and Korean (n = 396; women n = 199, 50.3%). For both sexes, mean spine strength did not differ between groups, but femur strength was 9% to 14% higher in Whites (p ≤ 0.001), an effect that became non-significant after weight adjustment (p = 0.375). For Koreans of both sexes, the fragile bone strength thresholds for classifying osteoporosis, when derived from regional DXA BMD T-score references, equaled the clinically validated thresholds for Whites (in women and men, femoral strength, 3000 N and 3500 N; vertebral strength 4500 N and 6500 N, respectively). Using these thresholds, classifications for osteoporosis for Koreans based on bone strength versus based on DXA BMD T-scores were consistent (89.1% to 94.4% agreement) at both the hip and spine and for both sexes. The BCT-based, clinically validated bone strength thresholds for Whites also applied to Koreans, which may facilitate clinical interpretation of CT-based bone strength measurements for Koreans. © 2020 American Society for Bone and Mineral Research (ASBMR).     

Clinical Utility of Computer-Aided Diagnosis of Vertebral Fractures From Computed Tomography Images

Osteoporotic vertebral compression fractures (VCFs) are a risk factor for morbidity and mortality, frequently asymptomatic and often present in computed tomography (CT) scans performed for unrelated conditions. Computer-aided diagnosis (CAD) of VCF from such images can potentially improve identification and treatment of osteoporosis. This single-blinded, single tertiary center study compared a CAD (Zebra Medical Vision®) to an adjudicated imaging specialist reevaluation using a retrospective consecutive sample of abdominal and thoracic CT scans (n = 2357) performed as part of routine care. Subjects over 50 years between January 1, 2019 and May 12, 2019 were included. Duplicates and unanalyzable scans were excluded resulting in a total of 1696 CT scans. The sensitivity, specificity, and accuracy were calculated for all VCF and for Genant grades 2 or 3 (ie, height loss of >25%) using imaging specialist as the gold standard. Prestudy VCF reporting by hospital-rostered radiologist was used to calculate the number of scans needed to screen (NNS) to detect one additional VCF using CAD. Prevalence of any VCF was 24% (406/1696) and of Genant 2/3 VCF was 18% (280/1570). The sensitivity and specificity were 54% and 92%, for all fractures, respectively, and 65% and 92% for Genant 2/3 fractures, respectively. Accuracy for any VCF, and for detection of Genant 2/3 VCF, was 83% and 88%, respectively. Of 221 CAD-detected VCFs, 133 (60.2%) were reported prestudy resulting in 88 additional fractures (72 Genant 2/3) being identified by CAD. NNS to detect one additional VCF was 19 scans for all fractures and 23 for Genant 2/3 fractures. Thus, the CAD tested in this study had a high specificity with moderate sensitivity to detect incidental vertebral fractures in CT scans performed for routine care. A low NNS suggests it is an efficient tool to assist radiologists and clinicians to improve detection and reporting of vertebral fractures. © 2020 American Society for Bone and Mineral Research (ASBMR).     

Change in Trabecular Bone Score (TBS) With Antiresorptive Therapy Does Not Predict Fracture in Women: The Manitoba BMD Cohort

Bone mineral density (BMD) and trabecular bone score (TBS), along with additional clinical risk factors, can be used to identify individuals at high fracture risk. Whether change in TBS in untreated or treated women independently affects fracture risk is unclear. Using the Manitoba (Canada) DXA Registry containing all BMD results for the population we identified 9044 women age ≥40 years with two consecutive DXA scans and who were not receiving osteoporosis treatment at baseline (baseline mean age 62 ± 10 years). We examined BMD and TBS change, osteoporosis treatment, and incident major osteoporotic fractures (MOFs) for each individual. Over a mean of 7.7 years follow‐up, 770 women developed an incident MOF. During the interval between the two DXA scans (mean, 4.1 years), 5083 women initiated osteoporosis treatment (bisphosphonate use 80%) whereas 3961 women did not receive any osteoporosis treatment. Larger gains in both BMD and TBS were seen in women with greater adherence to osteoporosis medication (p for trend <0.001), and the magnitude of the increase was consistently greater for BMD than for TBS. Among treated women there was greater antifracture effect for each SD increase in total hip BMD change (fracture decrease 20%; 95% CI, 13% to 26%; p < 0.001), femoral neck BMD change (19%; 95% CI, 12% to 26%; p < 0.001), and lumbar spine BMD change (9%; 95% CI, 0% to 17%; p = 0.049). In contrast, change in TBS did not predict fractures in women who initiated osteoporosis treatment (p = 0.10). Among untreated women neither change in BMD or TBS predicted fractures. We conclude that, unlike antiresorptive treatment–related changes in BMD, change in lumbar spine TBS is not a useful indicator of fracture risk irrespective of osteoporosis treatment. © 2016 American Society for Bone and Mineral Research.     

Longitudinal Effects of Single Hindlimb Radiation Therapy on Bone Strength and Morphology at Local and Contralateral Sites

Radiation therapy (RTx) is associated with increased risk for late‐onset fragility fractures in bone tissue underlying the radiation field. Bone tissue outside the RTx field is often selected as a “normal” comparator tissue in clinical assessment of fragility fracture risk, but the robustness of this comparison is limited by an incomplete understanding of the systemic effects of local radiotherapy. In this study, a mouse model of limited field irradiation was used to quantify longitudinal changes in local (irradiated) and systemic (non‐irradiated) femurs with respect to bone density, morphology, and strength. BALB/cJ mice aged 12 weeks underwent unilateral hindlimb irradiation (4 × 5 Gy) or a sham procedure. Femurs were collected at endpoints of 4 days before treatment and at 0, 1, 2, 4, 8, 12, and 26 weeks post‐treatment. Irradiated (RTx), Contralateral (non‐RTx), and Sham (non‐RTx) femurs were imaged by micro‐computed tomography and mechanically tested in three‐point bending. In both the RTx and Contralateral non‐RTx groups, the longer‐term (12‐ to 26‐week) outcomes included trabecular resorption, loss of diaphyseal cortical bone, and decreased bending strength. Contralateral femurs generally followed an intermediate response compared with RTx femurs. Change also varied by anatomic compartment; post‐RTx loss of trabecular bone was more profound in the metaphyseal than the epiphyseal compartment, and cortical bone thickness decreased at the mid‐diaphysis but increased at the metaphysis. These data demonstrate that changes in bone quantity, density, and architecture occur both locally and systemically after limited field irradiation and vary by anatomic compartment. Furthermore, the severity and persistence of systemic bone damage after limited field irradiation suggest selection of control tissues for assessment of fracture risk or changes in bone density after radiotherapy may be challenging. © 2017 American Society for Bone and Mineral Research.