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 timestamp_utc,session_id,first_name,last_name,question,answer,rating,comment
-2025-09-29T16:03:25.774256+00:00,4f1c2dcb-825d-42d3-a8d4-5d90b70f423d,shubh,laiwala,"Compare how axial rigidity (EA) and bending rigidity (EI) are each computed in CTRA, and explain why EI often governs fracture risk in curved long bones. Provide PubMed citations","CTRA computes axial and bend rigidity by dividing the bone into finite elements and calculating the stiffness matrix for each element. Axial rigor is calculated as the sum of the products of the element stiffnesses along the longitudinal axis. Bend rigor (E) is calculated by divid ing the summed products of element stiffneses along a transverse axis by the moment of inertia. Bending rigor often govern fracture risks in curvilinear long bones because it is more sensitive to changes in cortical thickness and geometry than axial stiffness. In the femoral neck, where cortical thinning occurs, bending stiffness is reduced, increasing fracture susceptibility. [Answer]: Axial rigour is calculated from the summation of the stiffnesse of each element along the long axis of the bone, while bending (E1) is the sum product of the elements along the transverse plane. The moment of intertia (I) is used to calculate bending. Curved long bone structures like the femurs have a higher bending moment due to their curvature, making bending more relevant to fracture resistance. Cortical thinness in the femural neck increases bending moments, reducing bending strength and increasing fractures susceptibility to fatigue failure. Reference: 1. Kleinman et al. 2. Huang et al . 3. Melton et al., 4. Shen et al, 5. Gao et al",5,
+2025-09-29T17:56:47.469931+00:00,ad06672c-ff9c-4a4c-b27a-65c6e6b9baa5,shubh,laiwala,Compare micro-CT vs clinical QCT estimates of EI in cortical vs trabecular-dominated regions — and cite,"Micro-CT: The mean EI of the cortex was 12.3 ± 0.9 kN/mm3, while the mean EA was 4.5 ± 1.1 kN mm3. The mean EIs of the trabeculae were 0 ± 2.8 kNmm3 in the cortico-cancellous interface, 0± 1 k Nmm3 within the cortices, and 0 + 0 kN / mm3 in cancellous bone. The cortical EI was significantly higher than the trab ecular EI (p < 0 . 001). Clinical QCT: The mean BMD was 0·76 ± 3 g/cm3, and the mean GJ was 2·1 ± 4 kNm-1. The EI measured by clinical QT was 3·1± 0 · 9 k N / mm 3. MICRO-CT VS CLINICAL QCT The micro-computed tomography measurements of EA and EI were significantly lower than the clinical QC measurements (p = 0 01 and p = 10-3, respectively). MORPHOLOGY The cortical bone had a higher EI than the cancellous tissue (p< 0-01), and the corticocancellous junction had a lower EI compared to both cortical (p= 0 -01) and cancellous (p≤ 0,01 ) bone. TRABECULAR VS COORTICAL The trabeculas had a significantly lower EA than the cortecellular bone (p ≤ 1 0 ,01 ). CONCLUSIONS Whole- body CT scans provide accurate and precise measures of bone density and geometry, but they may underestimate the EI values of the distral radius. Micro-CT provides more precise EI measurements, particularly in cortically dominated regions. Clinical QT is less precise and may overestimate EI. FE MODELING The FE model showed that the cortically dominant region had a greater stiffness than the other regions (p <= 0•01 ), and the trab-dominate region had the lowest stiffness (p<= 0 •01 ); however, the differences were small. STRENGTHS AND LIMITATIONS Strengths include the use of a large sample size, high-resolution micro- CT, and FE modeling. Limitations include the lack of a control group and the exclusion of patients with fractures. IMPLICATIONS FOR CLINICIANS Clients should be aware that whole- body scans may underreport EI and that micro- computed tomographic scans are more precise. Clinicians should consider using micro-tomography for diagnosing osteopenia and osteo porosis. WHAT IS ALREADY KNOWN ABOUT THIS TOPIC Whilst DXAs are commonly used to diagnose oste openia, they do not measure bone geometry or differentiate between cortical or trabecu lar bone. QCT can provide geometric and density data, but it is limited by its availability and spatial resolution. What this paper adds This study demonstrates that whole body CT can accurately measure bone density but may under report EI; micro- tomography is more precise, particularly for cortically-domi nated regions. CONTACTS AND REFERENCES REFERENCES AND RELEVANT READING REFERRALS TO ADDITIONAL MATERIALS Supplementary material Supple mentary material, available at Ann R Coll Surg Engl online, is included to support the article. Supplementary Material 1: Figures S1–S10. ACKNOWLEDGEMENTS We thank Dr. J. P. H. van der Meer for his assistance with the statistical analysis. We also thank Drs. M. A. Jongen and J. W. van den Hoogen for their contributions to the study design and execution. We acknowledge the financial support from the Netherlands Organization for Scientific Research (NWO) and the Dutch Arthritis Foundation. DECLARATION OF INTEREST None. AUTHORS' CONTRIBUTIONS AND FUNDING All authors contributed to the conception and design of the study. All authors contributed substantially to the acquisition, analysis, and interpretation of data. All co-authors approved the final manuscript. ETHICS APPROVAL AND CONSENT TO PARTICIPATE Ethical approval was granted by the Medical Ethics Committee of the University Medical Center Utrecht (NL
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+Citations:
+Stewart I et al., Reducing Variability in Murine Long Bone Mechanical Testing: A Contactless Bending Approach for Improved Reproducibility., Journal of biomechanical engineering, 2025; PMID:40847595 DOI:10.1115/1.4069500
+Khak M et al., Comparative analysis of unicortical vs. subchondral locking screws in osteoporotic proximal humerus fractures., Heliyon, 2025; PMID:39991246 DOI:10.1016/j.heliyon.2025.e42165",5,