Quantification Of Bone Mineral Density Research Articles

Trabecular bone mineral density correlations using QCT: Central and peripheral human skeleton

Musculoskeletal injuries to the lower leg and foot-ankle joint are associated with external mechanical loads resulting from motor vehicle crashes, under body blasts, falls from height, or sports. As an intrinsic material property, the bone mineral density (BMD) is related to bone strength. The clinically recognized biological sites for BMD evaluation are the hip and spine. The focus of this study was to define the correlation between BMD from standard clinical sites (hip and lumbar spine) compared to BMD from non-standard sites (foot-ankle-distal tibia bones). Twenty-one post-mortem human subjects (PMHS) with mean age, height, and mass of 63 ± 11 years, 179 ± 7 cm, and 86 ± 13 kg, respectively were used for analysis. Clinical BMD software (Mindways Software, Inc.) was used for trabecular BMD quantification using quantitative computed tomography (QCT). In quantification of BMD of the foot-ankle-distal tibia (hind foot), the trabecular BMD of the talus (316 ± 86mg/cc) was highest followed by the distal tibia (238 ± 72 mg/cc) and then calcaneus (147 ± 51 mg/cc). To correlate BMD values from foot bone regions with the central skeleton BMD values within the same PMHS, there were 18 lumbar spine and 12 hip BMDs available. The BMD of the distal tibia correlated best with the hip intertrochanter BMD (R2 of 0.72). Calcaneus BMD best correlated with the hip femoral neck BMD (R2 = 0.64). In summary, the hind foot bone BMD values correlated better with the hip as compared to the lumbar spine BMD from the same PMHS. These findings indicate that, in the absence of a direct measure of foot-bone BMD, hip BMD might be a better predictor of injury risk to hind foot rather than lumbar spine BMD, or alternatively, calcaneal trabecular BMD can be used to predict the risk of injury to hip. Further, these relationships between central and peripheral regions can also be implemented in finite element models for improved failure predictions.

Valores de referencia de la densidad mineral ósea por densitometría tipo DXA en una población adulta sana de Bogotá

IntroductionThe current definition of osteoporosis is based on the dual energy X-ray absorptiometry (DXA), which represents the main technique for the quantification of bone mineral density (BMD) and the evaluation of fracture risk. The objective of this study was to determine the BMD in the lumbar spine and femoral neck of healthy adults from a bone metabolism point of view in a population of Bogotá-Colombia. MethodAn observational, analytical, cross-sectional study was conducted based on a questionnaire completed by the study population. The densitometric measurements were carried out using a high-performance compact equipment of the General Electric, iDXA model, by the same technologist at the skeletal sites of interest, lumbar spine L1, L2, L3, L4 and L1-4 in anteroposterior projection, and in femoral neck. The sample size calculation was performed taking into account stratification by gender and 2 age groups: 20 to 29 years, and 30 to 39 years. A total of 805 individuals were surveyed, and 432 bone densitometries were performed. ResultsThe values found in the lumbar spine for each of the groups in our population were: 1.150 g/cm2 (SD: 0.11), 1.180 g/cm2 (SD: 0.10), for women and men aged 20 to 29 years, and 1.169 g/cm2 (SD: 0.10), 1.209 g/cm2 (SD: 0.10) for women and men aged 30 to 39, respectively. At the level of the femoral neck, 0.991 g/cm2 (SD: 0.10), 1.119 g/cm2 (SD: 0.13), for women and men aged 20 to 29 years, respectively, and 0.970 g/cm2 (SD: 0.11), 1.079 g/cm2 (SD: 0.13) for women and men aged 30 to 39, respectively. ConclusionThis study was able to demonstrate the behaviour of BMD in our population, which is lower than that detected in other latitudes and those used as reference values in our equipment. Additionally, the maximum bone mass value was determined in each of the locations of interest for the age ranges of the population in our study.

Association between vertebral bone mineral density, myocardial perfusion, and long-term cardiovascular outcomes: A sex-specific analysis

BackgroundSexual dimorphism in the manifestation of coronary artery disease (CAD) has unleashed a call to reconsider cardiovascular risk assessment. Alterations of bone mineral density (BMD) have been associated with congestive heart failure and appear to be modified by sex. However, the sex-specific association between BMD, myocardial perfusion, and cardiovascular outcomes is currently unknown. MethodsA total number of 491 patients (65.9 ± 10.7 years, 32.4% women) underwent 13N-ammonia positron emission tomography/computed tomography for evaluation of CAD, and were tracked for major adverse cardiac events (MACEs). ResultsEvent-free survival (median follow-up time of 4.3 ± 2.0 years) was significantly reduced in patients with low (≤ 100 Hounsfield units) compared to those with higher BMD (log-rank P = .037). Accordingly, reduced BMD was chosen as significant predictor of MACE in a fully adjusted proportional hazards regression model (P = .015). Further, a first-order interaction term consisting of sex and BMD was statistically significant (P = .007). BMD was significantly lower in patients with abnormal myocardial perfusion or impaired left ventricular ejection fraction (P < .05). This difference, however, was noticed in men, but not in women. ConclusionsThe association between low BMD and cardiovascular disease is sex dependent. Our data suggest that quantification of BMD during myocardial perfusion imaging for evaluation of CAD may be particularly useful in men.

Change in Bone Mineral Density after Total Ankle Replacement: Two Year Follow Up

Category:Ankle, Ankle ArthritisIntroduction/Purpose:Bone strength about the components is an important factor in Arthroplasty survival. This importance has been studied in total hip & knee replacement. However, there is paucity of literature Where little has been published regarding the quality of the bone and bone mineral content postoperatively surrounding Ankle Arthroplasty and circumstances surrounding the development of stress fracture.This prospective study used a method to quantify Bone Mineral Density BMD in different regions of the surrounding bones adjacent to tibia and talar components of uncemented Mobility ankle prosthesis, and to study the effect of loading on local ankle bone in the presence of un-cemented three components ankle replacement, by analyzing the BMD of the areas around tibia and talus before and after Mobility total ankle replacement.Methods:Twenty three Ankles (7Females, 15 Males) who underwent a Mobility Total Ankle Arthroplasty (TAA) between March 2008 and April 2009 were included prospectively in this study. They underwent a Bone Density Scan using the DEXA HOLIGIC Scanner with the specific method designed for measuring BMD. Seven areas (R1-R7) around the prosthesis were studied (Please see attached figure). Scans were carried out pre-operatively and repeated at 1 and 2 years post-operatively. The results were also compared with clinical outcomes, using (AOFAS scores) both pre, 1 and 2 years post-op.Results:Mean age of patients was 63.3 years (SD 9, range 43 to 80).AOFAS scores showed significant improvement (from 28.8 pre-op to 78.7,76.9 at 12 and 24 months post-op respectively; p<0.05). BMD within the lateral malleolus decreased significantly from 0.5g/cm2 to 0.42g/cm2 (17%, P < 0.01), at one and two years postoperatively - R2.There was an insignificant increase in Mean BMD at medial side metaphysis of tibia increased by,7% (+0.07 g cm -2, R6), but this just failed to reach statistical significance, mean BMD within medial malleolus decreased slightly from 0.67g/cm2 to 0.64 g/cm2 at the same period which was statistically insignificant. There was little insignificant increase in BMD in tibia just proximal to implant (R7) and at talus (R5).Conclusion:Stemmed implant causes changes in Tibial BMD around prosthesis. There was stress shielding over the lateral malleolus resulting in decrease BMD in lateral malleolus and to a lesser extent of the medial malleolus. The increase in BMD at tibial metaphysis indicates an increase in mechanical stresses at that region, which may explain occasional postoperative stress fracture of medial malleolus or medial sided ankle pain. There is no further change in BMD from year 1 to year 2 following TAR.

&lt;p&gt;Bone-mineral density: clinical significance, methods of quantification and forensic applications&lt;/p&gt;

Bone-mineral density (BMD) is a measure of the inorganic mineral content inbone, and is one of the more informative assessments of bone quality in both clinical studiesand forensic investigations. Several factors, such as age, sex, disease, genetics, and lifestyle,affect BMD measurements, and normative standards must be applied for specific groups andindividuals. One of the most common disorders associated with low BMD is osteoporosisand increased fracture risk, due to a decrease in bone strength and an increase in bonefragility. Medical conditions like diabetes or hyperthyroidism and other parameters like peakbone mass and postmenopausal estrogen deficiency also impact BMD. Single- and dual-energy photon absorptiometry, quantitative computet tomography, and magnetic resonanceimaging are some of the technological modalities for BMD quantification, and each presentsdistinct advantages and limitations, depending on the purpose of the analysis, the specificcharacteristics of the individual, the bone site under examination, and the equipment andtrained personnel available. Recently, BMD values were applied to forensic medicine in avariety of scenarios ranging from age and sex estimation to the assessment of malnutritionand the use offinite-element modelling. Despite technical and methodological inconsisten-cies reported in the literature on BMD readings, there is scope for expanding the use of thisvariable in forensic settings (4) (PDF) Bone-mineral density: clinical significance, methods of quantification and forensic applications. Available from: https://www.researchgate.net/publication/334676972_Bone-mineral_density_clinical_significance_methods_of_quantification_and_forensic_applications [accessed Aug 22 2019].

RELATION OF CONE BEAM COMPUTED TOMOGRAPHY ASSESSMENT OF MANDIBULAR BONE DENSITY TO DUAL ENERGY X-RAY ABSORPTIOMETRY IN TYPE 2 DIABETES MELLITUS PATIENTS

INTRODUCTION: One of the complications associated with diabetes mellitus is decrease in bone mineral density (BMD). Therefore, quantification of BMD for these patients before a dental implant procedure is essential. Cone beam computed tomography (CBCT) is an important tool that can be used for qualitative and quantitative bone assessment for treatment planning of dental implants. OBJECTIVES: Evaluation of mandibular bone mineral density measured by CBCT and its correlation to T-score obtained by dual energy xray absorptiometry (DEXA) in relation to blood glycemic control as detected by glycosylated hemoglobin (HbA1c) in type 2 diabetic patients (T2DM). MATERIALS AND METHODS: The study was conducted clinically on twenty-four patients having T2DM, referred for CBCT examination as a part of implant planning. BMD was measured for each edentulous mandibular space using CBCT scan. The patients were grouped according to the level of HbA1c into 4 groups; control group, well-controlled group, moderately controlled group and poorly controlled group. Additionally, each candidate was examined radio-graphically using DEXA. Then, a statistical correlation between HbA1c values in relation to mandibular BMD values and T-score values was investigated. RESULTS: there was a statistically significant correlation between HbA1c values and BMD variables including: mandibular edentulous quad BMD and T-score values (p <0.001), and a statistically significant correlation between T-score value and Mandibular edentulous quad BMD (p <0.001). CONCLUSIONS: Osteoporosis is a commonly underestimated problem in diabetes patients. Osteoporosis can be predicted using CBCT, so it’s the dentist responsibility to refer osteoporotic patients once being suspected.

Liquid Calibration Phantoms in Ultra-Low-Dose QCT for the Assessment of Bone Mineral Density

Introduction: Cortical bone is affected by metabolic diseases. Some studies have shown that lower cortical bone mineral density (BMD) is related to increases in fracture risk which could be diagnosed by quantitative computed tomography (QCT). Nowadays, hybrid iterative reconstruction-based (HIR) computed tomography (CT) could be helpful to quantify the peripheral bone tissue. A key focus of this paper is to evaluate liquid calibration phantoms for BMD quantification in the tibia and under hybrid iterative reconstruction-based-CT with the different hydrogen dipotassium phosphate (K2HPO4) concentrations phantoms. Methodology: Four ranges of concentrations of K2HPO4 were made and tested with 2 exposure settings. Accuracy of the phantoms with ash gravimetry and intermediate K2HPO4 concentration as hypothetical patients were evaluated. The correlations and mean differences between measured equivalent QCT BMD and ash density as a gold standard were calculated. Relative percentage error (RPE) in CT numbers of each concentration over a 6-mo period was reported. Results: The correlation values (R2 was close to 1.0), suggested that the precision of QCT-BMD measurements using standard and ultra-low dose settings were similar for all phantoms. The mean differences between QCT-BMD and the ash density for low concentrations (about 93 mg/cm3) were lower than high concentration phantoms with 135 and 234 mg/cm3 biases. In regard to accuracy test for hypothetical patient, RPE was up to 16.1% for the low concentration (LC) phantom for the case of high mineral content. However, the lowest RPE (0.4 to 1.8%) was obtained for the high concentration (HC) phantom, particularly for the high mineral content case. In addition, over 6 months, the K2HPO4 concentrations increased 25% for 50 mg/cm3 solution and 0.7 % for 1300 mg/cm3 solution in phantoms. Conclusion: The excellent linear correlations between the QCT equivalent density and the ash density gold standard indicate that QCT can be used with submilisivert radiation dose. We conclude that using liquid calibration phantoms with a range of mineral content similar to that being measured will minimize bias. Finally, we suggest performing BMD measurements with ultra-low dose scan concurrent with iterative-based reconstruction to reduce radiation exposure.

Developing focal construct technology for in vivo diagnosis of osteoporosis

Osteoporosis is a prevalent bone disease around the world, characterised by low bone mineral density and increased fracture risk. Currently, the gold standard for identifying osteoporosis and increased fracture risk is through quantification of bone mineral density (BMD), using dual energy X-ray absorption (DEXA). However, the use of BMD to diagnose osteoporosis is not without limitation and arguably the risk of osteoporotic fracture should be determined collectively by bone mass, architecture and physicochemistry of the mineral composite building blocks. Rather than depending exclusively on the ‘mass’ of bone, our previous research investigated predicting the risk of fracture using ‘bone quality’. The work highlighted that the material properties of OP tissue differ significantly to that of ‘normal’ bone and for the first time reported the clinical value of new biomarkers (obtained from X-ray scatter signatures) for fracture risk prediction. Thus, in order to improve fracture prediction models, diagnostic tools need to be developed which not only measure bone mineral density, but also bone quality.This pilot study builds on our previous work and aims to develop a new technology, Focal Construct Technology (FCT), which is hoped can measure XRD signatures in vivo. Our previous work was performed entirely with interrogating probes applied in transmission mode. This has some disadvantages that would be overcome were reflection mode employed. This study involves the creation of unique, high impact data with the potential to form the basis of a new generation of medical diagnostic instrumentation. A systematic series of conventional reflection mode ex vivo experiments were performed in which bone specimens were examined through increasing thicknesses of overlaying muscle/fat/skin. Further, we applied FCT to these geometries. This had not previously been attempted and required some initial modelling to ensure correct topologies of the hollow beams. The results from this study suggest it may be possible to obtain the parameters in vivo with the same precision as those obtained within the laboratory when using FCT.

Vertebral Bone Mineral Density Measured by Quantitative Computed Tomography With and Without a Calibration Phantom: A Comparison Between 2 Different Software Solutions

Quantitative computed tomography (CT) can be used to quantify bone mineral density (BMD) in the spine from clinical CT scans. We aimed to determine agreement and precision of BMD measurements by 2 different methods: phantom-less internal tissue calibration and asynchronous phantom-based calibration in a cohort of patients with chronic kidney disease (CKD). Patients with CKD were recruited for CT angiography of the chest, abdomen, and pelvis. BMD was analyzed by 2 different software solutions using different calibration techniques; phantom-based by QCT Pro (Mindways Inc.) and phantom-less by Extended Brilliance Workspace (Philips Healthcare). Intraoperator reanalysis was performed on 53 patients (36%) for both methods. An interoperator reanalysis on 30 patients (20%) using the phantom-based method and 29 patients (19%) using the phantom-less method was made. XY- and Bland-Altman plots were used to evaluate method agreement. Phantom-based measured BMD was systematically higher than phantom-less measured BMD. Despite a small absolute difference of 3.3 mg/cm3 (CI: -0.2–6.9 mg/cm3) and a relative difference of 5.1% (CI: 2.2%–8.1%), interindividual differences were large, as seen by a wide prediction interval (PI: -47–40 mg/cm3). The Bland-Altman plot showed no systematic bias, apart from 5 outliers. Intraoperator variability was high for the phantom-less method (5.8%) compared to the phantom-based (0.8%) and the interoperator variability was also high for the phantom-less method (5.8%) compared to the phantom-based (1.8%). Despite high correlation between methods, the between-method difference on an individual level showed great variability. Our results suggest agreement between these 2 methods is insufficient to allow them to be used interchangeably in patients with CKD.

What is changed in the diagnosis of osteoporosis: the role of radiologists

Osteoporosis (OP) is a very common condition with several repercussions on patients’ quality of life and health systems (1). OP is secondary to changes in normal bone turnover for decreased activity of osteoblasts (which produce bone matrix) or increased osteoclastic activity (2,3). These changes determine variation in bone mineral content (BMC) and then bone mineral density (BMD); thus, quantification of BMD correlate to changes in bone matrix.

A novel dual energy method for enhanced quantitative computed tomography

Accurate assessment of bone mineral density (BMD) is critically important in clinical practice, and conveniently enabled via quantitative computed tomography (QCT). Meanwhile, dual-energy QCT (DEQCT) enables enhanced detection of small changes in BMD relative to single-energy QCT (SEQCT). In the present study, we aimed to investigate the accuracy of QCT methods, with particular emphasis on a new dual-energy approach, in comparison to single-energy and conventional dual-energy techniques. We used a sinogram-based analytical CT simulator to model the complete chain of CT data acquisitions, and assessed performance of SEQCT and different DEQCT techniques in quantification of BMD. We demonstrate a 120% reduction in error when using a proposed dual-energy Simultaneous Equation by Constrained Least-squares method, enabling more accurate bone mineral measurements.

Age-Related Changes in Femoral Head Trabecular Microarchitecture.

Osteoporosis is a prevalent bone condition, characterised by low bone mineral density and increased fracture risk. Currently, the gold standard for identifying osteoporosis and increased fracture risk is through quantification of bone mineral density using dual energy X-ray absorption. However, many studies have shown that bone strength, and consequently the probability of fracture, is a combination of both bone mass and bone ‘quality’ (architecture and material chemistry). Although the microarchitecture of both non-fracture and osteoporotic bone has been previously investigated, many of the osteoporotic studies are constrained by factors such as limited sample number, use of ovariectomised animal models, and lack of male and female discrimination. This study reports significant differences in bone quality with respect to the microarchitecture between fractured and non-fractured human femur specimens. Micro-computed tomography was utilised to investigate the microarchitecture of femoral head trabecular bone from a relatively large cohort of non-fracture and fracture human donors. Various microarchitectural parameters have been determined for both groups, providing an understanding of the differences between fracture and non -fracture material. The microarchitecture of non-fracture and fracture bone tissue is shown to be significantly different for many parameters. Differences between sexes also exist, suggesting differences in remodelling between males and females in the fracture group. The results from this study will, in the future, be applied to develop a fracture model which encompasses bone density, architecture and material chemical properties for both female and male tissues.

Brief Report: Recovery of Bone Mineral Density After Discontinuation of Tenofovir-Based HIV Pre-exposure Prophylaxis.

Oral tenofovir disoproxil fumarate (TDF) for HIV prevention and treatment is associated with decreases in bone mineral density (BMD). Previous reports suggest that these changes may be reversible after discontinuation of TDF. A metabolic substudy of 498 participants in a randomized, placebo-controlled HIV prevention trial of oral coformulated TDF with emtricitabine (TDF/FTC, Truvada) for HIV pre-exposure prophylaxis (PrEP) enrolling a global sample of men who have sex with men and trans women. Participants underwent dual X-ray absorptiometry to quantify bone mineral density (BMD) in the hip and spine during PrEP and at 2 visits after stopping (median of 23 and 79 weeks post-PrEP, respectively). Results are stratified by pharmacologic measure of TDF/FTC adherence. There was no significant difference in change in hip/spine BMD at any time point between placebo and those with low adherence. Adherent participants had a mean (standard error) BMD change at TDF/FTC discontinuation of -1.02% (0.24) in the hip and -1.84% (0.36) in the spine. After stop, annualized BMD increases of 1.13% per year (0.27) in hip and 1.81% per year (0.36) in spine BMD were observed in adherent participants compared with 0.19% (0.16) and 0.74% (0.21) in the placebo group, respectively (P = 0.003, both comparisons). On average, BMD returned to baseline levels by 1 year after PrEP stop. Recovery was consistent across age, baseline BMD z-score, and treatment duration. Mean BMD returns to baseline levels within 12-18 months after TDF-based PrEP discontinuation in both hip and spine with consistency across participant subgroups. clinicaltrials.gov NCT00458393.

Validation of asynchronous quantitative bone densitometry of the spine: Accuracy, short-term reproducibility, and a comparison with conventional quantitative computed tomography

Asynchronous calibration quantitative computed tomography (QCT) is a new tool that allows the quantification of bone mineral density (BMD) without the use of a calibration phantom during scanning; however, this tool is not fully validated for clinical use. We used the European spine phantom (ESP) with repositioning during scanning and assessed the accuracy and short-term reproducibility of asynchronous QCT. Intra-scanner and intra-observer precision were each calculated as the root mean square of the standard deviation (RMSSD) and the coefficient of variation (CV-RMSSD). We also compared asynchronous and conventional QCT results in 50 clinical subjects. The accuracy of asynchronous QCT for three ESP vertebrae ranged from 1.4–6.7%, whereas intra-scanner precision for these vertebrae ranged from 0.53–0.91 mg/cc. Asynchronous QCT was most precise for a trabecular BMD of 100 mg/cc (CV-RMSSD = 0.2%). For intra-observer variability, overall precision error was smaller than 3%. In clinical subjects there was excellent agreement between the two calibration methods with correlation coefficients ranging from 0.96–0.99. A Bland–Altman analysis demonstrated that methodological differences depended on the magnitude of the BMD variable. Our findings indicate that the asynchronous QCT has good accuracy and precision for assessing trabecular BMD in the spine.

Accuracy of bone mineral density quantification using dual-layer spectral detector CT: a phantom study

ObjectivesTo investigate the accuracy of bone mineral density (BMD) quantification using dual-layer spectral detector CT (SDCT) at various scan protocols.MethodsTwo validated anthropomorphic phantoms containing inserts of 50–200 mg/cm3 calcium hydroxyapatite (HA) were scanned using a 64-slice SDCT scanner at various acquisition protocols (120 and 140 kVp, and 50, 100 and 200 mAs). Regions of interest (ROIs) were placed in each insert and mean attenuation profiles at monochromatic energy levels (90–200 keV) were constructed. These profiles were fitted to attenuation profiles of pure HA and water to calculate HA concentrations. For comparison, one phantom was scanned using dual energy X-ray absorptiometry (DXA).ResultsAt both 120 and 140 kVp, excellent correlations (R = 0.97, P < 0.001) were found between true and measured HA concentrations. Mean error for all measurements at 120 kVp was -5.6 ± 5.7 mg/cm3 (-3.6 ± 3.2%) and at 140 kVp -2.4 ± 3.7 mg/cm3 (-0.8 ± 2.8%). Mean measurement errors were smaller than 6% for all acquisition protocols. Strong linear correlations (R2 ≥ 0.970, P < 0.001) with DXA were found.ConclusionsSDCT allows for accurate BMD quantification and potentially opens up the possibility for osteoporosis evaluation and opportunistic screening in patients undergoing SDCT for other clinical indications. However, patient studies are needed to extend and translate our findings.Key points• Dual-layer spectral detector CT allows for accurate bone mineral density quantification.• BMD measurements on SDCT are strongly linearly correlated to DXA.• SDCT, acquired for several indications, may allow for evaluation of osteoporosis.• This potentially opens up the possibility for opportunistic osteoporosis screening.

Bone loss at the distal femur and proximal tibia in persons with spinal cord injury: imaging approaches, risk of fracture, and potential treatment options.

Persons with spinal cord injury (SCI) undergo immediate unloading of the skeleton and, as a result, have severe bone loss below the level of lesion associated with increased risk of long-bone fractures. The pattern of bone loss in individuals with SCI differs from other forms of secondary osteoporosis because the skeleton above the level of lesion remains unaffected, while marked bone loss occurs in the regions of neurological impairment. Striking demineralization of the trabecular epiphyses of the distal femur (supracondylar) and proximal tibia occurs, with the knee region being highly vulnerable to fracture because many accidents occur while sitting in a wheelchair, making the knee region the first point of contact to any applied force. To quantify bone mineral density (BMD) at the knee, dual energy x-ray absorptiometry (DXA) and/or computed tomography (CT) bone densitometry are routinely employed in the clinical and research settings. A detailed review of imaging methods to acquire and quantify BMD at the distal femur and proximal tibia has not been performed to date but, if available, would serve as a reference for clinicians and researchers. This article will discuss the risk of fracture at the knee in persons with SCI, imaging methods to acquire and quantify BMD at the distal femur and proximal tibia, and treatment options available for prophylaxis against or reversal of osteoporosis in individuals with SCI.

Detection of bone marrow changes related to estrogen withdrawal in rats with a tabletop stray-field NMR scanner.

Osteoporosis is characterized by a decrease in bone mineral density (BMD). A preliminary stage of the disease is progressive bone marrow adiposity, caused by imbalance between osteogenesis and adipogenesis in the marrow. Detection of osteoporosis relies on the quantification of BMD with techniques such as dual-energy X-ray absorptiometry. This work aimed to detect bone marrow changes in an experimental model of osteopenia using a low-field tabletop NMR scanner. An experiment was performed on 32 female rats, 3 months old, 16 of which were ovariectomized (OVX) and 16 were sham-operated (sham). The femur and tibia from both hind limbs were isolated and underwent ex vivo NMR scans at four time points after the OVX and sham operations. NMR scans were complemented by BMD measurements and histology. Significant changes in the bone marrow of ovariectomized rats, relative to sham operated rats, were observed after 3.5 and 4.5 months. Bone marrow adiposity was detected by significant changes in T1 and T2 relaxation times, and in the diffusion coefficient. This study suggests a potential detection of changes to the bone marrow using a tabletop NMR device. Clinical translation may facilitate screening, early detection of bone weakening as a result of estrogen withdrawal, and monitoring of treatment efficacy. Magn Reson Med 78:860-870, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Towards new material biomarkers for fracture risk

Osteoporosis is a prevalent bone condition, characterised by low bone mass and increased fracture risk. Currently, the gold standard for identifying osteoporosis and increased fracture risk is through quantification of bone mineral density (BMD) using dual energy X-ray absorption (DEXA). However, the risk of osteoporotic fracture is determined collectively by bone mass, architecture and physicochemistry of the mineral composite building blocks. Thus DEXA scans alone inevitably fail to fully discriminate individuals who will suffer a fragility fracture. This study examines trabecular bone at both ultrastructure and microarchitectural levels to provide a detailed material view of bone, and therefore provides a more comprehensive explanation of osteoporotic fracture risk. Physicochemical characterisation obtained through X-ray diffraction and infrared analysis indicated significant differences in apatite crystal chemistry and nanostructure between fracture and non-fracture groups. Further, this study, through considering the potential correlations between the chemical biomarkers and microarchitectural properties of trabecular bone, has investigated the relationship between bone mechanical properties (e.g. fragility) and physicochemical material features.

Associations between bone lead and bone density in the Nurses Lead Study

Background: Bone lead (Pb) is a marker of cumulative Pb exposure. Pb in bone may adversely affect both its cellular and structural components, but this association is not well understood. Methods: Study participants were Boston-area women from the Nurses’ Health Study [age 47-74 (mean 61)]. Pb was measured in the tibia and patella using k-X-ray Fluorescence. Bone Mineral Density (BMD) was assessed using dual-energy x-ray absorptiometry (DEXA) of the hip and spine. A subset of participants provided a second BMD measure 6 years after the initial visit. Results: 619 participants provided bone Pb and BMD measures. 163 participants returned for a second visit for longitudinal analysis. In cross sectional multivariable models adjusted for age, lifestyle, menopausal status and hormone replacement, a10 µg/g increase in patella Pb was associated with 1.2% (95% CI 0.3%, 2.1%) higher total hip BMD and 1.92% (95% CI 0.8%, 3.0%) higher total spine BMD. Similarly, a 10 µg/g increase in tibia Pb was associated with 1.1% (95% CI 0.004%, 2.2%) higher total hip BMD and 0.8% (95% CI -0.5%, 2.2%) higher spine BMD. Similar findings were observed for participants with a history of post-menopausal hormone use. Among women not using post-menopausal hormones, associations were attenuated and in some cases became negative, although not statistically significant. In longitudinal analysis, higher Pb was associated with a steeper decline in BMD, but results lacked precision. In subgroup analyses among women who had not used osteoporosis medications, each 10 µg/g increase in tibia Pb was associated with -0.08 (95% CI -0.2, -0.005) decline in BMD t-score. Conclusions: Our cross sectional results suggest that bone Pb may interfere with DEXA quantification of BMD (wherein Pb and calcium may be indistinguishable). This limitation does not apply to our longitudinal analyses where findings provide preliminary support for lead's hypothesized contribution to aging associated declines in BMD.

Peri-implant bone adaptations to overloading in rat tibiae: experimental investigations and numerical predictions.

(i) To assess the effects of mechanical overloading on implant integration in rat tibiae, and (ii) to numerically predict peri-implant bone adaptation. Transcutaneous titanium implants were simultaneously placed into both tibiae of rats (n=40). After 2weeks of integration, the implants of the right tibiae were stimulated daily for 4weeks with loads up to 5N (corresponding to peak equivalent strains of 3300±500με). The effects of stimulation were assessed by exvivo mechanical tests and quantification of bone mineral density (BMD) in selected regions of interests (ROIs). Specimen-specific finite element models were generated and processed through an iterative algorithm to mimic bone adaptation. Bilateral implantation provoked an unstable integration that worsened when mild (2-4N) external loads were applied. In contrast, a stimulation at 5N tended to "counterbalance" the harmful effects of daily activity and, if applied to well-integrated specimens, significantly augmented the implants' resistance to failure (force: +73% P<0.01, displacement: +50% P<0.01 and energy: +153% P<0.01). Specimen-specific numerical predictions were in close agreement with the experimental findings. Both local and overall BMD variations, as well as the implants' lateral stability, were predicted with small errors (0.14gHA/cm3 and 0.64%, respectively). The rats' daily activity detrimentally affects implant integration. Conversely, external stimulations of large magnitudes counterbalance this effect and definitively improve integration. These changes can be predicted using the proposed numerical approach.