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Representative proximal femoral neck segmentation. The black region corresponds to cortical bone, which encloses the trabecular region. The outer red line corresponds to the periosteal surface; inner yellow line corresponds to the endocortical surface. Principal axes used to define bending-based strength indices (principal area moments of inertia I max /I min and section moduli Z max /Z min ) are shown in blue and intersect at the cortical bone centroid.
Source publication
Objective:
To determine the in vivo precision of MRI-based measures of bone and muscle traits at the hip.
Methods:
Left proximal femoral neck and shaft of 14 participants (5M:9 F; age:21-68) were scanned 3 times using a 1.5 T MRI. Commercial and custom image processing methods were used to derive bone geometry and strength traits at the proximal...
Contexts in source publication
Context 1
... single researcher (LL) performed all segmentations. For segmenting bone, the periosteal and endocortical surfaces of the femoral neck and shaft were outlined to derive bone traits ( Figure 1). For segmenting muscle, four groups were distinguished and segmented according to their movement functionalities: hip extensors (gluteus maximus, semitendinosus, long head of the biceps femoris); hip adductors (adductor magnus, adductor longus, adductor brevis, gracilis); hip flexors (rectus femoris, sartorius); and knee extensors (vastus intermedius, vastus medialis, vastus lateralis). ...
Context 2
... and muscle at the femoral neck and shaft were semi- automatically segmented (outlined) using commercial segmen- tation software (Analyze 10: Mayo Foundation, Rochester, MN, USA). The semi-automatic segmentation process con- sisted of seeded region growing combined with manual cor- rection via an interactive touch-screen tablet (Cintiq 21UX, Wacom, Krefeld, Germany). Region growing was guided by participant-specific threshold values which defined 50% mid-point intensity values between adjacent tissues (e.g. cortical bone & trabecular bone, muscle & cortical bone, muscle & fat); a method analogous to the Half-Maximum Height Method 25,26 . Participant-specific thresholds were derived using isolated regional analyses of image intensity of subcutaneous fat, muscle, cortical, and trabecular bone, with the average in- tensity of adjacent tissues defining respective 50% threshold values. A single researcher (LL) performed all segmentations. For segmenting bone, the periosteal and endocortical surfaces of the femoral neck and shaft were outlined to derive bone traits ( Figure 1). For segmenting muscle, four groups were dis- tinguished and segmented according to their movement func- tionalities: hip extensors (gluteus maximus, semitendinosus, long head of the biceps femoris); hip adductors (adductor mag- nus, adductor longus, adductor brevis, gracilis); hip flexors (rectus femoris, sartorius); and knee extensors (vastus inter- medius, vastus medialis, vastus ...
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Citations
... MRI scans of the left proximal femur were obtained from a previous research study 32 . Axial images (relative to the orientation of the participant) of the hip were obtained using a clinical 1.5 T scanner (Magnetom Avanto, Siemens, Germany) with a 6-channel body array coil positioned over the hip region. ...
... Additionally, MR-FE precision errors for the two configurations are comparable with no substantial differences. In comparison to an MR precision study of bone morphology (e.g., cortical thickness) 32 , which used the same scan data evaluated here, reported precision errors were smaller (< 7.1%) than the errors reported here. Though, our study considered FE outcomes of 3D volumetric ROI's whereas Johnston et al. 32 reported metrics based on single 2D image slices. ...
... In comparison to an MR precision study of bone morphology (e.g., cortical thickness) 32 , which used the same scan data evaluated here, reported precision errors were smaller (< 7.1%) than the errors reported here. Though, our study considered FE outcomes of 3D volumetric ROI's whereas Johnston et al. 32 reported metrics based on single 2D image slices. ...
Proximal femoral fractures are a serious life-threatening injury with high morbidity and mortality. Magnetic resonance (MR) imaging has potential to non-invasively assess proximal femoral bone strength in vivo through usage of finite element (FE) modelling (a technique referred to as MR-FE). To precisely assess bone strength, knowledge of measurement error associated with different MR-FE outcomes is needed. The objective of this study was to characterize the short-term in vivo precision errors of MR-FE outcomes (e.g., stress, strain, failure loads) of the proximal femur for fall and stance loading configurations using 13 participants (5 males and 8 females; median age: 27 years, range: 21–68), each scanned 3 times. MR-FE models were generated, and mean von Mises stress and strain as well as principal stress and strain were calculated for 3 regions of interest. Similarly, we calculated the failure loads to cause 5% of contiguous elements to fail according to the von Mises yield, Brittle Coulomb-Mohr, normal principal, and Hoffman stress and strain criteria. Precision (root-mean squared coefficient of variation) of the MR-FE outcomes ranged from 3.3% to 11.8% for stress and strain-based mechanical outcomes, and 5.8% to 9.0% for failure loads. These results provide evidence that MR-FE outcomes are a promising non-invasive technique for monitoring femoral strength in vivo.
... Measured parameters and calculated indices are known to reflect the resistance of a bone to mechanical loading, including torsion, bending, axial compression and tension, and local buckling (Turner & Burr, 1993). Analysis of crosssectional geometry is a common technique in cortical bone assessment (Johnston et al. 2014) and has been used to analyse both human and non-human bone Pearson & Lieberman, 2004;de Margerie et al. 2005;Marelli & Simons, 2014;Cosman et al. 2016). The principal area moment of inertia (I) reflects the resistance of a bone to bending around a chosen axis. ...
... The principal section modulus is a direct measure of the strength of a bone and its resistance to bending in a specified axis. Similar to the polar area moment of inertia, we calculated the maximum and minimum (Z max /Z min ) section moduli and a polar section modulus (Z p ), which reflects torsional strength (Johnston et al. 2014). We also calculated the buckling ratio, a measure of the instability of a bone, reflecting its ability to resist local fractures. ...
... Principal section moduli were calculated by dividing the equivalent principal area moment of inertia by the corresponding maximum distances to the outer periosteal edges from the principal neutral axes. The polar section modulus was defined following Johnston et al. (2014) by dividing the polar area moment of inertia by the maximum outer radius of the bone. The buckling ratio was calculated as the ratio of total area to cortical area (Siev€ anen et al. 2016). ...
Cortical bone porosity and specifically the orientation of vascular canals is an area of growing interest in biomedical research and comparative/paleontological anatomy. The potential to explain microstructural adaptation is of great interest. However, the determinants of the development of canal orientation remain unclear. Previous studies of birds have shown higher proportions of circumferential canals (called laminarity) in flight bones than in hindlimb bones, and interpreted this as a sign that circumferential canals are a feature for resistance to the torsional loading created by flight. We defined the laminarity index as the percentage of circumferential canal length out of the total canal length. In this study we examined the vascular canal network in the humerus and femur of a sample of 31 bird and 24 bat species using synchrotron micro-computed tomography (micro-CT) to look for a connection between canal orientation and functional loading. The use of micro-CT provides a full three-dimensional (3D) map of the vascular canal network and provides measurements of the 3D orientation of each canal in the whole cross-section of the bone cortex. We measured several cross-sectional geometric parameters and strength indices including principal and polar area moments of inertia, principal and polar section moduli, circularity, buckling ratio, and a weighted cortical thickness index. We found that bat cortices are relatively thicker and poorly vascularized, whereas those of birds are thinner and more highly vascularized, and that according to our cross-sectional geometric parameters, bird bones have a greater resistance to torsional stress than the bats; in particular, the humerus in birds is more adapted to resist torsional stresses than the femur. Our results show that birds have a significantly (P = 0.031) higher laminarity index than bats, with birds having a mean laminarity index of 0.183 in the humerus and 0.232 in the femur, and bats having a mean laminarity index of 0.118 in the humerus and 0.119 in the femur. Counter to our expectation, the birds had a significantly higher laminarity index in the femur than in the humerus (P = 0.035). To evaluate whether this discrepancy was a consequence of methodology we conducted a comparison between our 3D method and an analogue to two-dimensional (2D) histological measurements. This comparison revealed that 2D methods significantly underestimate (P < 0.001) the amount of longitudinal canals by an average of 20% and significantly overestimate (P < 0.001) the laminarity index by an average of 7.7%, systematically mis-estimating indices of vascular canal orientations. In comparison with our 3D results, our approximated 2D measurement had the same results for comparisons between the birds and bats but found significant differences only in the longitudinal index between the humerus and the femur for both groups. The differences between our 3D and pseudo-2D results indicate that differences between our findings and the literature may be partially based in methodology. Overall, our results do not support the hypothesis that the bones of flight are more laminar, suggesting a complex relation between functional loading and microstructural adaptation.
Background:
Magnetic resonance imaging (MRI) is the dominant 3D imaging modality to quantify muscle properties in skeletal muscle disorders, in inherited and acquired muscle diseases, and in sarcopenia, in cachexia and frailty.
Methods:
This review covers T1 weighted and Dixon sequences, introduces T2 mapping, diffusion tensor imaging (DTI) and non-proton MRI. Technical concepts, strengths, limitations and translational aspects of these techniques are discussed in detail. Examples of clinical applications are outlined. For comparison 31P-and 13C-MR Spectroscopy are also addressed.
Results:
MRI technology provides a rich toolset to assess muscle deterioration. In addition to classical measures such as muscle atrophy using T1 weighted imaging and fat infiltration using Dixon sequences, parameters characterizing inflammation from T2 maps, tissue sodium using non-proton MRI techniques or concentration or fiber architecture using diffusion tensor imaging may be useful for an even earlier diagnosis of the impairment of muscle quality.
Conclusion:
Quantitative MRI provides new options for muscle research and clinical applications. Current limitations that also impair its more widespread use in clinical trials are lack of standardization, ambiguity of image segmentation and analysis approaches, a multitude of outcome parameters without a clear strategy which ones to use and the lack of normal data.
Background:
Intermittent mechanical loading generates greater bone adaptations than continuous mechanical loading in rodents but has never been evaluated in humans. This study aimed to evaluate the feasibility of a continuous and intermittent countermovement jump (CMJ) intervention for attenuating early postmenopausal BMD loss.
Methods:
41 healthy early postmenopausal women (age = 54.6 ± 3.4 years) were randomly assigned to a continuous countermovement jumping group, an intermittent countermovement jumping group or a control group for 12 months. Adherence and dropout rates were recorded along with bone mineral density (BMD) at lumbar spine, femoral neck and trochanter sites at baseline, 6 months and 12 months.
Results:
28 participants completed the study. Dropout rate during the intervention (from the initiation of exercise) was 36% from continuous and 38% from intermittent countermovement jumping groups. For the participants that completed the intervention, adherence was 60.0 ± 46.8% for continuous and 68.5 ± 32.3% for intermittent countermovement jumping. The control group lost significant lumbar spine BMD (% difference = -2.7 [95%CI: -3.9 to -1.4]) and femoral neck BMD (% difference = -3.0% [95%CI: -5.1 to -0.8]). There was no statistically significant change in BMD for either countermovement jumping group. There was no statistically significant difference in BMD change between continuous or intermittent countermovement jumping groups when compared with the control group.
Conclusions:
Adherence and dropout rates were in line with previous similar interventions. To evaluate the effect of continuous and intermittent exercise on BMD, future studies should focus on maintaining participant engagement and adherence to the exercise intervention. Feasibility of a 12-month continuous and intermittent high-impact exercise intervention.
