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Example of lumbar and hip DXA scans analysed with BSI image (right). The colours follow a ramp from blue (low strain) to green (intermediate strain), yellow, and red (high strain), indicating an increase of the risk factor for fracture proportionated to the increase of the strain
Source publication
Reduced bone mass with or without fragility fractures is a common feature of mastocytosis, particularly in adult males. However, bone mineral density does not account for all the fragility fractures, being a part of them attributable to impairment in bone quality. Aim of this study is to assess the usefulness of DXA-derived geometry and structural...
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Background
Systemic mastocytosis is a hematological disease in which aberrant mast cells accumulate due to gain-of-function mutations in the KIT receptor. Group 2 innate lymphoid cells (ILC2s) are effector cells of type 2 immune responses that also express KIT and co-localize with mast cells at barrier tissue sites. In mouse models, mast cell-ILC2...
Citations
... Furthermore, low values of F-BSI seem to be connected with the non-occurrence of vertebral fractures [19]. In secondary osteoporosis, L-BSI demonstrated good ability in discriminating vertebral fractured patients affected by hyperparathyroidism [20,21] and appeared to be useful in the clinical characterisation of patients affected by mastocytosis [22] and recessive dystrophic epidermolysis bullosa [23], whereas F-BSI proved to be associated with vertebral fractures in aromatase inhibitor naive patients [24]. In addition, BSI was able to detect patients treated with anabolic osteoporotic that do not present BMD increase [25]. ...
Bone Strain Index (BSI), based on dual-energy X-ray absorptiometry (DXA), is a densitometric index of bone strength of the femur and lumbar spine. Higher BSI values indicate a higher strain applied to bone, predisposing to higher fracture risk. This retrospective, multicentric study on Italian women reports the BSI normative age-specific reference curves. A cohort of Caucasian Italian women aged 20 to 90 years was selected from three different clinical centres. Bone mineral density (BMD) and BSI measurements were obtained for the lumbar spine vertebrae (L1–L4) and for the femur (neck, trochanter and intertrochanter) using Hologic densitometers scans. The data were compared with BMD normative values provided by the densitometer manufacturer. Then, the age-specific BSI curve for the femur and lumbar spine was generated. No significant difference was found between the BMD of the subjects in this study and BMD reference data provided by Hologic (p = 0.68 for femur and p = 0.90 for lumbar spine). Spine BSI values (L1–L4) increase by 84% between 20 and 90 years of age. The mean BSI of the total femur increases about 38% in the same age range. The BSI age-specific reference curve could help clinicians improve osteoporosis patient management, allowing an appropriate patient classification according to the bone resistance to the applied loads and fragility fracture risk assessment.
... In patients with SM, most fragility fractures may occur with normal bone mineral density (BMD), which requires assessment of bone-related quality parameters. DXA provides information on trabecular compartment based on lumbar spine textural index (Trabecular Bone Score, TBS) [11], bone deformation (Bone Strain Index) [12], and bone cross-sectional geometry (Hip Structural Analysis) [13]. However, volumetric evaluation of bone tissue is not possible by DXA. ...
Patients with systemic mastocytosis (SM) are at high risk of bone deterioration. However, the evaluation of bone microarchitecture in this disease remains unclear. We aimed to assess bone microarchitecture in patients with SM. This was a cross-sectional study of 21 adult patients with SM conducted in a quaternary referral hospital in Sao Paulo, Brazil. A healthy, age-, weight-, and sex-matched cohort of 63 participants was used to provide reference values for bone microarchitecture, assessed by high resolution peripheral quantitative computed tomography (HR-pQCT). Total volumetric bone mineral density (vBMD), cortical vBMD, and cortical thickness at the radius were significantly lower in the control group compared with the SM group (all P < 0.001). Patients with aggressive SM had significantly lower trabecular number (Tb.N) (P = 0.035) and estimated failure load (F.load) (P = 0.032) at the tibia compared with those with indolent SM. Handgrip strength was significantly higher in patients who had more Tb.N at the radius (ρ, 0.46; P = 0.036) and tibia (ρ, 0.49; P = 0.002), and lower who had more trabecular separation at the radius (ρ, −0.46; P = 0.035) and tibia (ρ, −0.52; P = 0.016). Strong and positive associations between F.load (ρ, 0.75; P < 0.001) and stiffness (ρ, 0.70; P < 0.001) at the radius, and between F.load at the tibia (ρ, 0.45; P = 0.038) were observed with handgrip strength. In this cross-sectional study, aggressive SM was more susceptible to bone deterioration compared with indolent SM. In addition, the findings demonstrated that handgrip strength was associated with bone microarchitecture and bone strength.
... It represents an index of deformation based on finite element analysis and can be automatically calculated from DXA exams [6,15]. Previous studies showed the utility of BSI in the identification of subjects with high fracture risk [16], for fracture risk prediction [17,18], for re-fracture prediction and for further characterization of young patients suffering secondary forms of osteoporosis [19,20]. In addition, BSI was able to predict the occurrence of vertebral fractures in patients with primary hyperparathyroidism, independent of BMD [21], as well as to be influenced by the use of anabolic osteoporotic therapy in fractured subjects with osteoporosis [22]. ...
PurposeBone Strain Index (BSI) is a recently developed dual-energy X-ray absorptiometry (DXA) software, applying a finite element analysis on lumbar spine and femoral DXA scans. BSI is a parameter of bone deformation, providing information on bone resistance to applied loads. BSI values indicate the average bone strain in the explored site, where a higher strain (higher BSI values) suggests a higher fracture risk. This study reports the distributional characteristics of lumbar BSI (L-BSI) in women with normal bone mass, osteopenia or osteoporosis and their relationships with BMD, weight, height and BMI.Material and methodsTwo-hundred-fifty-nine consecutive unfractured women who performed DXA were divided into three groups based on BMD T-score: normal bone mass (n = 43, 16.6%), osteopenia (n = 82, 31.7%) and osteoporosis (n = 134, 51.7%). The distribution of L-BSI was evaluated with conventional statistical methods, histograms and by calculating parametric and nonparametric 95% confidence intervals, together with the 90%, 95% and 99% bilateral tolerance limits with a 95% confidence.ResultsNinety percent bilateral tolerance limits with 95% confidence for L-BSI distribution are 1.0–2.40, 0.95–2.63 and 0.84–3.15 in the group of patients with normal bone mass, 1.34–2.78, 1.24–2.95 and 1.05–3.32 in the osteopenic group and 1.68–3.79, 1.58–4.15 and 1.40–4.96 in the osteoporotic group.Conclusion
In women without vertebral fractures at baseline, L-BSI values from 1.68 (osteoporotic group) and 2.40 (upper of the normal bone mass group) can be tentatively chosen as a lower and upper threshold to stratify postmenopausal women according to their bone resistance to loads.
... Tryptase increased by about 22 units for each unit increase of lumbar BSI. In addition, lumbar BSI resulted to be statistically significantly lower in women than in men, suggesting that men have a minor lumbar bone resistance to compressive loads, which is consistent with more severe bone involvement in mastocytosis in the males [27] (Table 1). ...
Bone strain Index (BSI) is an innovative index of bone strength that provides information about skeletal resistance to loads not considered by existing indexes (Bone Mineral Density, BMD. Trabecular Bone Score, TBS. Hip Structural Analysis, HSA. Hip Axis Length, HAL), and, thus, improves the predictability of fragility fractures in osteoporotic patients. This improved predictability of fracture facilitates the possibility of timely intervention with appropriate therapies to reduce the risk of fracture. The development of the index was the result of combining clinical, radiographical and construction-engineering skills. In fact, from a physical point of view, primary and secondary osteoporosis, leading to bone fracture, are determined by an impairment of the physical properties of bone strength: density, internal structure, deformation and fatigue. Dual X-ray absorptiometry (DXA) is the gold standard for assessing bone properties, and it allows measurement of the BMD, which is reduced mainly in primary osteoporosis, the structural texture TBS, which can be particularly degraded in secondary osteoporosis, and the bone geometry (HSA, HAL). The authors recently conceived and developed a new bone deformation index named Bone Strain Index (BSI) that assesses the resistance of bone to loads. If the skeletal structure is equated to engineering construction, these three indexes are all considered to determine the load resistance of the construct. In particular, BSI allows clinicians to detect critical information that BMD and TBS cannot explain, and this information is essential for an accurate definition of a patient’s fracture risk. The literature demonstrates that both lumbar and femoral BSI discriminate fractured osteoporotic people, that they predict the first fragility fracture, and further fragility fractures, monitor anabolic treatment efficacy and detect patients affected by secondary osteoporosis. BSI is a new diagnostic tool that offers a unique perspective to clinical medicine to identify patients affected by primary and, specially, secondary osteoporosis. This literature review illustrates BSI’s state of the art and its ratio in clinical medicine.
... A new DXA-based bone index has been recently proposed, namely Bone Strain Index (BSI), representing a deformation index, automatically inferred from lumbar and femoral DXA scans [18,19] and based on a finite element model (FEM). Recent clinical studies demonstrated the usefulness of BSI in identifying patients at risk of fracture [20], in the prediction of the first fragility fracture [21], in the prediction of the re-fracture [22][23][24], in characterizing young patients affected by secondary osteoporosis [25][26][27]. Furthermore, BSI has been demonstrated to be associated with vertebral fractures in primary hyperparathyroidism [28]. ...
Recently, the bone strain index (BSI), a new index of bone strength based on a finite element model (FEA) from dual X-ray absorptiometry (DXA), has been developed. BSI represents the average equivalent strain inside the bone, assuming that a higher strain level (high BSI) indicates a condition of higher risk. Our study aimed to analyze the relationship between BSI and age, BMI and areal BMD in pre- and postmenopausal women and to prospectively investigate fracture prediction (Fx) by BSI in postmenopausal women.
Methods. At the 14th annual follow-up of the OFELY study, BSI was measured at spine (Spine BSI) and femoral scans (Neck and Total Hip BSI), in addition to areal BMD with DXA (Hologic QDR 4500) in 846 women, mean (SD) age 60 yr (15). The FRAX® (fracture risk assessment tool) for major osteoporotic fractures (MOF) was calculated with FN areal BMD (aBMD) at baseline; incident fragility fractures were annually registered until January 2016.
Results. In premenopausal women (n = 261), Neck and Total Hip BSI were slightly negatively correlated with age (Spearman r = −0.13 and −0.15 respectively, p = 0.03), whereas all BSIs were positively correlated with BMI (r = +0.20 to 0.37, p < 0.01) and negatively with BMD (r = −0.69 to −0.37, p < 0.0001). In postmenopausal women (n = 585), Neck and Total Hip BSI were positively correlated with age (Spearman r = +0.26 and +0.31 respectively, p < 0.0001), whereas Spine BSI was positively correlated with BMI (r = +0.22, p < 0.0001) and all BSIs were negatively correlated with BMD (r = −0.81 to −0.60, p < 0.0001). During a median [IQ] 9.3 [1.0] years of follow-up, 133 postmenopausal women reported an incident fragility Fx, including 80 women with a major osteoporotic Fx (MOF) and 26 women with clinical vertebral Fx (VFx). Each SD increase of BSI value was associated with a significant increase of the risk of all fragility Fx with an age-adjusted HR of 1.23 for Neck BSI (p = 0.02); 1.27 for Total Hip BSI (p = 0.004) and 1.35 for Spine BSI (p < 0.0001). After adjustment for FRAX®, the association remained statistically significant for Total Hip BSI (HR 1.24, p = 0.02 for all fragility Fx; 1.31, p = 0.01 for MOF) and Spine BSI (HR 1.33, p < 0.0001 for all fragility Fx; 1.33, p = 0.005 for MOF; 1.67, p = 0.002 for clinical VFx).
In conclusion, spine and femur BSI, an FEA DXA derived index, predict incident fragility fracture in postmenopausal women, regardless of FRAX®.
... It was recently shown that lumbar BSI appeared able to characterise young patients affected by secondary osteoporosis [44,47] (Tab. I). ...
... Tryptase increased by about 22 units for each unit increase of lumbar BSI. Moreover, lumbar BSI was statistically significantly lower in women than in men, suggesting that men have worse lumbar bone resistance to compressive loads, in line with the more severe bone involvement in mastocytosis in the male sex [47] (Tab. I). ...
Bone mineral density, bone texture, bone geometry and bone strength are all elements necessary for a proper osteoporotic fragility fracture prediction assessment. Data regarding bone quantity (density) and, in part, bone quality (structure and geometry) are obtained by the gold standard method of dual X-ray absorptiometry (DXA), while data about bone strength are obtained by means of a new DXA index called the bone strain index (BSI). The BSI evaluates bone resistance by means of average strain calculation, and it is based on finite element analysis applied to DXA spine and femoral scans. The BSI includes local information on bone density distribution, bone geometry and, unlike variables of bone mineral density and bone quality such as the trabecular bone score, it represents the status of the bone in a particular loading condition. This review illustrates the methodology for calculating the BSI and discusses findings on its reproducibility and data about its capability to predict fragility fractures and monitor pharmacological treatment for osteoporosis.
... The implementation of this novel numerical patient-specific approach is validated by means of static compressive mechanical tests on porcine vertebrae. The use of linear elastic FE models highly reduces the computational time, opening new opportunities to integrate the SIB with the currently used and accepted clinical fragility indexes [12,13]. However, the anisotropy of trabecular structures, their spatial orientation and thickness, not captured by the DXA, are likely to play a crucial role in the determination of bone strength [14]. ...
The comprehension of trabecular bone damage processes could be a crucial hint for understanding how bone damage starts and propagates. Currently, different approaches to bone damage identification could be followed. Clinical approaches start from dual X-ray absorptiometry (DXA) technique that can evaluate bone mineral density (BMD), an indirect indicator of fracture risk. DXA is, in fact, a two-dimensional technology, and BMD alone is not able to predict the effective risk of fractures. First attempts in overcoming this issue have been performed with finite element (FE) methods, combined with the use of three-dimensional high-resolution micro-computed tomographic images. The purpose of this work is to evaluate damage initiation and propagation in trabecular vertebral porcine samples using 2D linear-elastic FE models from DXA images and 3D linear FE models from micro-CT images. Results show that computed values of strains with 2D and 3D approaches (e.g., the minimum principal strain) are of the same order of magnitude. 2D DXA-based models still remain a powerful tool for a preliminary screening of trabecular regions that are prone to fracture, while from 3D micro-CT-based models, it is possible to reach details that permit the localization of the most strained trabecula.
Graphical abstract
... 19,25 Thus, DEXA should be assessed in patients with idiopathic osteoporosis and mast-cell mediator release symptoms and in all SM patients at diagnosis and during follow-up to detect those who may benefit from an anti-osteoporotic treatment. [26][27][28][29] Meyer et al., 27 analyzing DEXA data, records, clinical data, and bone marrow biopsies of 39 patients with SM, retrospectively, reported that DEXA findings are positively associated with tryptase level and mast cell amount in bone marrow biopsies. In their study of 61 patients with SM, Riffel et al. 29 correlated the prevalence of osteoporosis, increased bone mineral density (BMD), and osteosclerosis with clinical parameters, disease type, and prognosis. ...
Radiological diagnosis of systemic mastocytosis (SM) can be hard to establish. This is mainly due to the variable radiological features involving many organ systems (e.g., respiratory, cardiovascular, lympho-reticular, digestive systems, and most commonly skin), and the broad spectrum of skeletal findings, in particular. Skeletal involvement is the most common and prominent imaging feature in patients with SM and represents a prognostic factor as it may entail an aggressive course of the disease. Diagnosis, which is largely established by histological evaluation of a bone marrow trephine biopsy specimen supplemented by imaging modalities such as radiography, CT, and magnetic resonance imaging, requires a team approach between the hematologist, radiologist, and pathologist. The general radiologist needs to be familiar with the imaging findings because they may be the first to suggest the correct diagnosis. The primary purposes of this article were to equip clinicians with pertinent radiological semiotics and present relevant radiological features that assist early diagnosis and selection of an effective treatment.
... That study showed a positive effect of teriparatide on TBS and BSI, suggesting that the increase in BMD was accompanied by increased bone strength (20). Finally, a study on a cohort of patients with mastocytosis showed a good correlation between BSI and biochemical index of disease activity and also the BSI's ability to discriminate whose patients with a higher risk of vertebral fracture (47). This methodology, thus, has the potential to lend insight into secondary causes of osteoporosis. ...
Context
Primary hyperparathyroidism (PHPT) is associated with impaired bone quality and increased fracture risk. Reliable tools for the evaluation of bone quality parameters are not yet clinically available. Bone Strain Index (BSI) is a new metric for bone strength based on Finite Element Analysis from lumbar spine and femoral neck dual X-ray absorptiometry images.
Objective
To assess the lumbar spine (LS), femoral neck (FN), and total hip (TH) BSI in PHPT compared to controls and to investigate the association of BSI with vertebral fractures (VFs) in PHPT.
Design
case-control study
Setting
Outpatient clinic
Patients
50 PHPT and 100 age- and sex-matched control subjects.
Main Outcome Measures
LS-BSI, FN-BSI, TH-BSI.
Results
FN bone mineral density (BMD) and 1/3 distal radius BMD were lower in the PHPT group than in controls (FN 0.633 ± 0.112 vs 0.666 ± 0.081 p= 0.042; radius 0.566 ± 0.07 vs 0.625 ± 0.06 p<0.001). PHPT group has significant lower TBS score compared to controls (1.24 ± 0.09 vs 1.30 ± 0.10 p <0.001).BSI was significantly higher at LS (2.28±0.59 vs 2.02±0.43, p=0.009), FN (1.72±0.41 vs 1.49±0.35, p=0.001) and TH (1.51±0.33 vs 1.36±0.25, p=0.002) in PHPT. LS-BSI showed moderate accuracy for discriminating VFs (AUC 0.667; 95% CI 0.513-0.820). LS-BSI ≥ 2.2 and was a statistically significant independent predictor of VFs, with an adjusted OR ranging from 5.7 to 15.1.
Conclusion
BSI, a DXA-derived bone quality index, is impaired in PHPT and may help to identify PHPT subjects at high risk of fractures.
The aim of this study was to determine whether the Bone Strain Index (BSI), a recent DXA-based bone index, is related to bone mechanical behavior, microarchitecture and finally, to determine whether BSI improves the prediction of bone strength and the predictive role of BMD in clinical practice.
Bone Strain Index (BSI) is a new DXA-based bone index that represents the finite element analysis of the bone deformation under load. The current study aimed to assess whether the BSI is associated with 3D microarchitecture and the mechanical behavior of human lumbar vertebrae.
Lumbar vertebrae (L3) were harvested fresh from 31 human donors. The anteroposterior BMC (g) and aBMD (g/cm2) of the vertebral body were measured using DXA, and then the BSI was automatically derived. The trabecular bone volume (Tb.BV/TV), trabecular thickness (Tb.Th), degree of anisotropy (DA), and structure model index (SMI) were measured using µCT with a 35-µm isotropic voxel size. Quasi-static uniaxial compressive testing was performed on L3 vertebral bodies under displacement control to assess failure load and stiffness.
The BSI was significantly correlated with failure load and stiffness (r = -0.60 and -0.59; p < 0.0001), aBMD and BMC (r = -0.93 and -0.86; p < 0.0001); Tb.BV/TV and SMI (r = -0.58 and 0.51; p = 0.001 and 0.004 respectively). After adjustment for aBMD, the association between BSI and stiffness, BSI and SMI remained significant (r = -0.51; p = 0.004 and r = -0.39; p = 0.03 respectively, partial correlations) and the relation between BSI and failure load was close to significance (r = -0.35; p = 0.06).
The BSI was significantly correlated with the microarchitecture and mechanical behavior of L3 vertebrae, and these associations remained statistically significant regardless of aBMD.
