Mechanical properties of femoral trabecular bone in dogs

BACKGROUND: Studying mechanical properties of canine trabecular bone is important for a better understanding of fracture mechanics or bone disorders and is also needed for numerical simulation of canine femora. No detailed data about elastic moduli and degrees of anisotropy of canine femoral trabecular bone has been published so far, hence the purpose of this study was to measure the elastic modulus of trabecular bone in canine femoral heads by ultrasound testing and to assess whether assuming isotropy of the cancellous bone in femoral heads in dogs is a valid simplification. METHODS: From 8 euthanized dogs, both femora were obtained and cubic specimens were cut from the centre of the femoral head which were oriented along the main pressure and tension trajectories. The specimens were tested using a 100 MHz ultrasound transducer in all three orthogonal directions. The directional elastic moduli of trabecular bone tissue and degrees of anisotropy were calculated. RESULTS: The elastic modulus along principal bone trajectories was found to be 11.2 GPa ± 0.4, 10.5 ± 2.1 GPa and 10.5 ± 1.8 GPa, respectively. The mean density of the specimens was 1.40 ± 0.09 g/cm(3). The degrees of anisotropy revealed a significant inverse relationship with specimen densities. No significant differences were found between the elastic moduli in x, y and z directions, suggesting an effective isotropy of trabecular bone tissue in canine femoral heads. DISCUSSION: This study presents detailed data about elastic moduli of trabecular bone tissue obtained from canine femoral heads. Limitations of the study are the relatively small number of animals investigated and the measurement of whole specimen densities instead of trabecular bone densities which might lead to an underestimation of Young's moduli. Publications on elastic moduli of trabecular bone tissue present results that are similar to our data. CONCLUSION: This study provides data about directional elastic moduli and degrees of anisotropy of canine femoral head trabecular bone and might be useful for biomechanical modeling of proximal canine femora

A new anisotropy index on trabecular bone radiographic images using the fast Fourier transform

BACKGROUND: The degree of anisotropy (DA) on radiographs is related to bone structure, we present a new index to assess DA. METHODS: In a region of interest from calcaneus radiographs, we applied a Fast Fourier Transform (FFT). All the FFT spectra involve the horizontal and vertical components corresponding respectively to longitudinal and transversal trabeculae. By visual inspection, we measured the spreading angles: Dispersion Longitudinal Index (DLI) and Dispersion Transverse Index (DTI) and calculated DA = 180/(DLI+DTI). To test the reliability of DA assessment, we synthesized images simulating radiological projections of periodic structures with elements more or less disoriented. RESULTS: Firstly, we tested synthetic images which comprised a large variety of structures from highly anisotropic structure to the almost isotropic, DA was ranging from 1.3 to 3.8 respectively. The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively. In 22 post-menopausal women with osteoporotic fracture cases and 44 age-matched controls, DA values were respectively 1.87 ± 0.15 versus 1.72 ± 0.18 (p = 0.001). From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA. CONCLUSION: The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions

In Vivo Evaluation of the Presence of Bone Marrow in Cortical Porosity in Postmenopausal Osteopenic Women

This is the first observational study examining cortical porosity in vivo in postmenopausal osteopenic women and to incorporate data from two different imaging modalities to further examine the nature of cortical porosity. The goal of this study was to combine high-resolution peripheral computed tomography (HR-pQCT) images, which contain high spatial resolution information of the cortical structure, and magnetic resonance (MR) images, which allow the visualization of soft tissues such as bone marrow, to observe the amount of cortical porosity that contains bone marrow in postmenopausal osteopenic women. The radius of 49 and the tibia of 51 postmenopausal osteopenic women (age 56 ± 3.7) were scanned using both HR-pQCT and MR imaging. A normalized mutual information registration algorithm was used to obtain a three-dimensional rigid transform which aligned the MR image to the HR-pQCT image. The aligned images allowed for the visualization of bone marrow in cortical pores. From the HR-pQCT image, the percent cortical porosity, the number of cortical pores, and the size of each cortical pore was determined. By overlaying the aligned MR and HR-pQCT images, the percent of cortical pores containing marrow, the number of cortical pores containing marrow, and the size of each cortical pore containing marrow were measured. While the amount of cortical porosity did not vary greatly between subjects, the type of cortical pore, containing marrow vs. not containing marrow, varied highly between subjects. The results suggest that cortical pore spaces contain components of varying composition, and that there may be more than one mechanism for the development of cortical porosity

Osteo-cise: Strong Bones for Life: protocol for a community-based randomised controlled trial of a multi-modal exercise and osteoporosis education program for older adults at risk of falls and fractures

Background : Osteoporosis affects over 220 million people worldwide, and currently there is no \u27cure\u27 for the disease. Thus, there is a need to develop evidence-based, safe and acceptable prevention strategies at the population level that target multiple risk factors for fragility fractures to reduce the health and economic burden of the condition. Methods : The \u27Osteo-cise: Strong Bones for Life\u27 study will investigate the effectiveness and feasibility of a multi-component targeted exercise, osteoporosis education/awareness and behavioural change program for improving bone health and muscle function, and reducing falls risk in community-dwelling older adults at an increased risk of fracture. Men and women aged 60 years or above will participate in an 18-month randomised controlled trial comprising a 12-month structured and supervised community-based program and a 6-month \u27research to practise\u27 translational phase. Participants will be randomly assigned to either the \u27Osteo-cise\u27 intervention or a self-management control group. The intervention will comprise a multi-modal exercise program incorporating high velocity progressive resistance training, moderate impact weight-bearing exercise and high challenging balance exercises performed three times weekly at local community-based fitness centres. A behavioural change program will be used to enhance exercise adoption and adherence to the program. Community-based osteoporosis education seminars will be conducted to improve participant knowledge and understanding of the risk factors and preventative measures for osteoporosis, falls and fractures. The primary outcomes measures, to be collected at baseline, 6, 12, and 18 months, will include DXA-derived hip and spine bone mineral density measurements and functional muscle power (timed stair-climb test). Secondary outcomes measures include: MRI-assessed distal femur and proximal tibia trabecular bone micro-architecture, lower limb and back maximal muscle strength, balance and function (four square step test, functional reach test, timed up-and-go test and 30-second sit-to-stand), falls incidence and health-related quality of life. Cost-effectiveness will also be assessed. Discussion : The findings from the Osteo-cise: Strong Bones for Life study will provide new information on the efficacy of a targeted multi-modal community-based exercise program incorporating high velocity resistance training, together with an osteoporosis education and behavioural change program for improving multiple risk factors for falls and fracture in older adults at risk of fragility fracture.<br /

Processing and analysis of in-vivo high-resolution MR images of trabecular bone for longitudinal studies: reproducibility of structural measures and micro-finite element analysis derived mechanical properties

The authors have developed a system for the characterization of trabecular bone structure from high-resolution MR images. It features largely automated coil inhomogeneity correction, trabecular bone region segmentation, serial image registration, bone/marrow binarization, and structural calculation steps. The system addresses problems of efficiency and inter- and intraoperator variability inherent in previous analyses. The system is evaluated on repetitive scans of 8 volunteers for both two-dimensional (2D) apparent structure calculations and three-dimensional (3D) mechanical calculations using micro-finite element analysis. Coil correction methods based on a priori knowledge of the coil sensitivity and on low-pas! s filtering of the high-resolution mages are compared and found to perform similarly. Image alignment is found to cause small but significant changes in some structural parameters. Overall the automated system provides on the order of a 3-fold decrease in trained operator time over previous manual methods. Reproducibility is found to be dependent on image quality for most parameters. For 7 subjects with good image quality, reproducibility of 2-4% is found for 2D structural parameters, while 3D mechanical parameters vary by 4-9%, with percent standardized coefficients of variation in the ranges of 15-34% and 20-38% respectively

High-resolution MRI and micro-FE for the evaluation of changes in bone mechanical properties during longitudinal clinical trials: application to calcaneal bone in postmenopausal women after one year of idoxifene treatment

Objective. To investigate whether recently developed in vivo high-resolution magnetic resonance-imaging and micro-finite element techniques can monitor changes in bone mechanical properties during long-term clinical trials aiming at evaluating the efficacy of new drugs for the treatment of osteoporosis.Design. Comparison of baseline and follow-up mechanical parameters calculated using micro-finite element analysis of the calcaneus for subjects participating in a study investigating the effect of idoxifene.Background. Contemporary measurements for the evaluation of bone mechanical properties, based on dual-energy X-ray absorptiometry measurements, are not very accurate and require large! trial populations.Methods. A total of 56 postmenopausal subjects received either a placebo, 5 mg or 10 mg per day of idoxifene. Magnetic resonance-images of the calcaneus were made at baseline and after one year. Mechanical parameters of a trabecular volume of interest in the calcaneus were calculated using micro-finite element analysis.Results. Although there were no significant differences between the mean changes in the treated groups and the placebo group, there were significant changes from baseline within groups after one year of treatment. Significant changes, however, were found only for mechanical parameters and only in the treated groups.Conclusions. The present study is the first demonstration that longitudinal changes in bone mechanical properties due to trabecular micro-architectural changes may be quantified in long-term clinical studies. Since significant changes in mechanical parameters were obtained for the treated groups whereas no ! significant change in bone mass was found we conclude that the application of these techniques may increase the clinical significance of these trials.Relevance A precise diagnosis of in vivo bone mechanical properties that accounts for (changes in) trabecular bone architecture is of particular importance for longitudinal clinical trials aiming at evaluating the efficacy of new drugs since it can lead to clinically relevant results from shorter follow-up intervals and may enable a reduction of the number of patients involved in the trial

MRI Enhancement in Stromal Tissue Surrounding Breast Tumors: Association with Recurrence Free Survival following Neoadjuvant Chemotherapy

Rationale and Objectives:Normal-appearing stromal tissues surrounding breast tumors can harbor abnormalities that lead to increased risk of local recurrence. The objective of this study was to develop a new imaging methodology to characterize the signal p