Image-Based Micro-Finite-Element Modeling for Improved Distal Radius Strength Diagnosis: Moving From “Bench” to “Bedside”

doi:10.1385/JCD:7:2:153

Journal of Clinical Densitometry

Volume 7, Issue 2, Summer 2004, Pages 153-160

https://doi.org/10.1385/JCD:7:2:153 Get rights and content

Abstract

Although osteoporosis is characterized by quantitative (mass) and qualitative (structural) changes, standard clinical techniques (dual-energy X-ray absorptiometry, DXA) only measure the former. Three-dimensional micro-finite-element (micro-FE) models based on high-resolution images can account for structural aspects as well, and it has recently been shown that an improved prediction of distal radius strength is possible with micro-FE analysis. A clinical application of this technique, however, is limited by its high imaging and computational demands. The objective of this study is to investigate if an improved prediction of bone strength can be obtained as well when only a small part of the radius is used for micro-FE modeling. Images of a 1-cm region of the metaphysis of the distal radius of 54 cadaver arms (mean age: 82 ± 9 SD) made with a three-dimensional peripheral quantitative computed tomography (pQCT) device at 165-μm resolution formed the basis for micro-FE models that were used to predict the bone failure load. Following imaging, specimens were experimentally compressed to failure to produce a Colles'-type fracture. Failure loads predicted from micro-FE analyses agreed well with those measured experimentally (R² = 0.66, p < 0.001). Lower correlations were observed with bone mass (R² = 0.48, p < 0.001) and microstructural parameters (R² = 0.47, p < 0.001). Hence, even when only a small region is modeled, micro-FE analysis provides an improved prediction of radius strength.

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HR-pQCT parameters of the distal radius correlate with the bending strength of the radial diaphysis
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Citation Excerpt :
The ROI was an axial segment equal to ~9.0 mm that started ~9.5 mm from the radiocarpal joint surface. Similar correlations between experimental failure force of cadaveric radii and μFEA predictions of failure load were observed in earlier studies using a lower resolution pQCT scanner (voxel size = 165 μm) and the same failure criteria: R2 = 0.75 [10] and R2 = 0.66 [11]. To date, there have been two validation studies of μFEA for the XtremeCT II scanner, which can generate images with an isotropic voxel size = 60.7 μm [12,13].
High resolution, peripheral quantitative computed tomography (HR-pQCT) scanners can now characterize an individual's trabecular architecture, cortical structure, and volumetric bone mineral density at a nominal resolution of 61 μm. While predictions of failure load of the distal radius and tibial diaphysis in compression by finite element analysis (FEA) of HR-pQCT scans have been validated against mechanical tests of cadaveric bones in compression, namely for images with nominal resolutions of 82 μm and 165 μm, the HR-pQCT parameters that best predict bending strength of cortical bone remain unknown. Therefore, we scanned cadaveric forearms from 31 elderly donors (Female: 72.8 ± 8.8 years and Male: 72.1 ± 6.3 years), and then loaded the radial diaphysis to failure in three-point bending after denuding each bone (38 in total). The cortical parameters had stronger correlations with ultimate moment than the trabecular parameters such that cortical area and estimated failure load of the distal radius had the highest Spearman correlation coefficients (r = 0.89 and r = 0.81, respectively, p < 0.0001). Despite being a known determinant of bone strength, cortical porosity of the distal radius did not correlate with ultimate moment (p = 0.8537). In multivariate linear regressions with section modulus (SM) of the radial diaphysis as one of two predictors of bending strength, cortical area and cortical thickness were each significant contributors to the prediction of ultimate moment. Their contribution was one-half and one-third, respectively, of the contribution from SM. None of the HR-pQCT parameters were strongly correlated with post-yield displacement, an indicator of bone brittleness. In support of HR-pQCT imaging of the distal radius to identify individuals with osteoporosis, the present study found that parameters of the cortex and failure load predictions by linear FEA are strongly related to the bending strength of cortical bone.
Clinical and genetic evaluation of Danish patients with pycnodysostosis
2021, European Journal of Medical Genetics
Pycnodysostosis is a rare autosomal recessive osteosclerotic skeletal dysplasia caused by variants in the cathepsin K gene (CTSK). Clinical features include short stature, bone fragility, characteristic facial features and acro-osteolysis of the distal phalanges. Usually, patients suffer from multiple bone fractures. The purpose of this study was to describe the Danish population of pycnodysostosis patients with respect to genotype, phenotype and the prevalence of complications.
We collected medical history, performed clinical examination, collected blood- and urine samples, performed dual-energy x-ray absorptiometry scan (DXA) and high-resolution peripheral quantitative computed tomography scan (HRpQCT) and obtained clinical photos. Information about complications, bone mineral density and bone markers in the blood were collected and analysed.
Ten patients with a median age of 32 years ranging from five to 51 years participated. The pycnodysostosis phenotype varied with respect to the number of bone fractures and degree of complications. DXA and HRpQCT showed high bone mineral density. A tendency of growth hormone treatment escalating growth and increasing final height was seen. A marker of bone resorption measured in blood was within normal range in nine patients and elevated in one patient. A novel pathogenic variant in CSTK causing pycnodysostosis was detected in two related patients. Moreover information about the patients’ own health perception was reported. An example being they rated their mental health to be good despite multiple bone fractures.
This study provides information about genotypes and phenotypes in a Danish pycnodysostosis population. It reports new data about the complications such as bone fractures and it elucidates the levels of bone turnover markers as well as the density of the bones in one of the biggest cohort of pycnodysostosis patients ever published. An individualised approach to treatment in this patient group is necessary as the phenotype including complications varies between patients. Additional studies are needed to further understand genotype-phenotype correlations.
In vivo repeatability of homogenized finite element analysis based on multiple HR-pQCT sections for assessment of distal radius and tibia strength
2020, Bone
Citation Excerpt :
As the tibia is roughly 1.4 times longer than the radius [17], a triple-section is scanned at the distal tibia (Fig. 2B). The validity of patient-specific μFE and homogenized FE (hFE) models has previously been investigated, showing high correlations with mechanical compression experiments of cadaveric samples [9–11,18,19]. In order to be of clinical use in detecting and monitoring changes in bone strength over time and during interventions or treatments, the measurement precision is fundamental [20].
Micro finite element analysis (μFE) is a widely applied tool in biomedical research for assessing in vivo mechanical properties of bone at measurement sites, including the ultra-distal radius and tibia. A finite element approach (hFE) based on homogenized constitutive models for trabecular bone offers an attractive alternative for clinical use, as it is computationally less expensive than traditional μFE. The respective patient-specific models for in vivo bone strength estimation are usually based on standard clinical high-resolution peripheral quantitative CT (HR-pQCT) measurements. They include a scan region of roughly 10 mm in height and are referred to as single-sections. It has been shown, that these small peripheral bone sections don't reliably cover the fracture line in Colles' fractures and therefore the weakest region at the radius. Recently introduced multiple section (multiple adjacent single-sections) measurements might improve the evaluation of bone strength, but little is known about the repeatability of hFE estimations in general, and especially for multiple section measurement protocols. Accordingly, the aim of the present work is to quantify repeatability of clinical in vivo bone strength measurement by hFE on multiple section HR-pQCT reconstructions at the distal radius and tibia.
Nineteen healthy Swiss women (43.6y ± 17.8y) and twenty men (48.2y ± 19.4y) were examined with HR-pQCT at 61 μm isotropic voxel resolution. Each subject was first scanned three times using a double-section (336 slices) at the distal radius and then three times using a triple-section (504 slices) at the distal tibia. The multiple section HR-pQCT reconstructions were graded for motion artefacts and non-linear hFE models (radius and tibia) and linear μFE models (only radius) were generated for estimation of stiffness and ultimate load. Then in vivo repeatability errors were computed in terms of root mean square coefficients of variation (CV).
In vivo repeatability errors of non-linear hFE stiffness (S) and ultimate load (F) were significantly higher at the radius (S: 2.71% and F: 2.97%) compared to the tibia (S: 1.21%, F: 1.45%). Multiple section linear μFE at the radius resulted in substantially higher repeatability errors (S: 5.38% and F: 10.80%) compared to hFE.
Repeatability errors of hFE outcomes based on multiple section measurements at the distal radius and tibia were generally lower compared to respective reported single-section μFE repeatability errors. Therefore, hFE is an attractive alternative to today's gold standard of μFE models and should especially be encouraged when analyzing multiple section measurements.
Distal radius sections offer accurate and precise estimates of forearm fracture load
2020, Clinical Biomechanics
Forearm fracture risk can be estimated via factor-of-risk: the ratio of applied impact force to forearm fracture load. Simple techniques are available for estimating impact force associated with a fall; estimating forearm fracture load is more challenging. Our aim was to assess whether failure load estimates of sections of the distal radius (acquired using High-Resolution peripheral Quantitative Computed Tomography and finite element modeling) offer accurate and precise estimates of forearm fracture load.
We scanned a section of the distal radius of 19 cadaveric forearms (female, mean age 83.7, SD 8.3), and 34 women (75.0, 7.7). Sections were converted to finite element models and failure loads were acquired for different failure criteria. We assessed forearm fracture load using experimental testing simulating a fall on the outstretched hand. We used linear regression to derive relationships between ex vivo forearm fracture load and finite element derived distal radius failure load. We used derived regression coefficients to estimate forearm fracture load, and assessed explained variance and prediction error. We used root-mean-squared coefficients of variation to assess in vivo precision errors of estimated forearm fracture load.
Failure load estimates of sections of the distal radius, used in conjunction with derived regression coefficients, explained 89–90% of the variance in experimentally-measured forearm fracture load with prediction errors <6.8% and precision errors <5.0%.
Failure load estimates of distal radius sections can reliably estimate forearm fracture load experienced during a fall. Forearm fracture load estimates can be used to improve factor-of-risk predictions for forearm fracture.
Renal osteodystrophy and chronic kidney disease-mineral bone disorder
2019, Principles of Bone Biology
Chronic kidney disease (CKD) affects over 20 million individuals in the United States, and 752 million individuals worldwide. Progressive kidney disease that leads to the need for dialysis (end-stage kidney disease) or transplantation affects over 700,000 individuals in the United States. CKD is defined as abnormalities of kidney structure or function present for >3 months, with stratification based on estimated glomerular filtration rate category and the magnitude of albuminuria. The Kidney Disease: Improving Global Outcomes group has updated the classification of CKD and changed the term “stage” to “grade,” as not all kidney disease is progressive, and noted that the presence or absence of albuminuria can greatly influence prognosis. There is considerable overlap between individuals identified with osteoporosis and CKD, and at every stage/grade of kidney disease, there is increased fracture risk, demonstrating the important contribution of CKD to bone fragility.
Harmonizing finite element modelling for non-invasive strength estimation by high-resolution peripheral quantitative computed tomography
2018, Journal of Biomechanics
The finite element (FE) method based on high-resolution peripheral quantitative computed tomography (HR-pQCT) use a variety of tissue constitutive properties and boundary conditions at different laboratories making comparison of mechanical properties difficult. Furthermore, the advent of a second-generation HR-pQCT poses challenges due to improved resolution and a larger region of interest (ROI). This study addresses the need to harmonize results across FE models. The aims are to establish the relationship between FE results as a function of boundary conditions and a range of tissue properties for the first-generation HR-pQCT system, and to determine appropriate model parameters for the second-generation HR-pQCT system. We implemented common boundary conditions and tissue properties on a large cohort (N = 1371), and showed the relationships were highly linear (R² > 0.99) for yield strength and reaction force between FE models. Cadaver radii measured on both generation HR-pQCT with matched ROIs were used to back-calculate a tissue modulus that accounts for the increased resolution (61 µm versus 82 µm), resulting in a modulus of 8748 MPa for second-generation HR-pQCT to produce bone yield strength and reaction force equivalent to using 6829 MPa for first-generation HR-pQCT. Finally, in vivo scans (N = 61) conducted on both generations demonstrated that the larger ROI in the second-generation system results in stronger bone outcome measures, suggesting it is not advisable to convert FE results across HR-pQCT generations without matching ROIs. Together, these findings harmonize FE results by providing a means to compare findings with different boundary conditions and tissue properties, and across scanner generations.

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Original ArticleImage-Based Micro-Finite-Element Modeling for Improved Distal Radius Strength Diagnosis: Moving From “Bench” to “Bedside”

Abstract

Bone

J Biomech

J Biomech

Bone

Bone

J Biomech

Biomaterials

Prediction of fracture load at different skeletal sites by geometric properties of the cortical shell

J Bone Miner Res

Bone strength at clinically relevant sites displays substantial heterogeneity and is best predicted from site-specific bone densitometry

J Bone Miner Res

Original Article
Image-Based Micro-Finite-Element Modeling for Improved Distal Radius Strength Diagnosis: Moving From “Bench” to “Bedside”