Trabecular Microstructural Parameters Research Articles

Quantifications of Mandibular Trabecular Bone Microstructure Using Cone Beam Computed Tomography for Age Estimation: A Preliminary Study.

Simple SummaryStudies pertaining to age-related changes in the human jaw are very limited. Age-related changes for forensic assessments were merely based on the qualitative architecture and external geometry. With advancements in imaging technology, the paradigm has shifted and more emphasis is laid on the internal trabecular architecture, as this imparts more complexity and strength when compared to other determinants. The desired objective of this study was to draw useful associations between trabecular microarchitecture and chronological age. In this study, we characterize trabecular bone microstructure in the human mandible in 20 subjects ranging from 22 to 43 years using retrospective cone beam computed tomography image datasets. The images were post-processed via a semi- automated threshold guided approach and reconstructed using AnalyzeDirect 14.0 software to correlate trabecular number (Tb. N), trabecular thickness (Tb. Th), trabecular separation (Tb. Sp), trabecular surface density (Tb- BS/TV) and trabecular bone volume (Tb- BV/TV) with the individual’s chronological age and sex. Statistically significant negative correlations were observed in trabecular number (r =−0.489) and trabecular surface density (r = −0.527) in relation to chronological age. The characterization and quantification of the trabecular bone microarchitecture can immensely serve as a digital imprint in chronological age estimation.The aim of this study is two-fold: first, to correlate the values for each of the trabecular bone microstructure (TBM) parameters to the individual’s chronological age and sex, thereby facilitating the assessment of potential age and sex-related changes in trabecular bone microstructure parameters in the mandible; and second, to quantify the trabecular microstructural parameters in relation to chronological age. Twenty cone-beam computed tomographic (CBCT) scans were retrieved retrospectively from a database of adult patients with ages ranging in age from 22 to 43 years. In the mandible, the volume of interest included the inter-dental space between the second mandibular premolar and the first mandibular molar, as well as the trabecular space beneath and between the apices. Using the AnalyzeDirect 14.0 software, the DICOM images of CBCT scans were pre-processed, transformed, segmented using a novel semi-automatic threshold-guided method, and quantified. In addition, TBM parameters were derived, and statistical analysis was conducted using a Pearson correlation test with two tails. All parameters exhibited no statistically significant differences (p > 0.05) between chronological age and sex. Statistically significant negative correlations were found between Tb. N (r = −0.489), BS/TV (r = −0.527), and chronological age (p = 0.029 and p = 0.017, respectively). Only Tb. N and BS/TV exhibited an inverse relationship with chronological age. Numerous studies have quantified the trabecular architecture of the jaw bones, but none have found a correlation between the quantified trabecular parameters and chronological age. The digital imprints produced by radiographic imaging can serve as biological profiles for data collection.

Polydatin alleviates osteoporosis by enhancing the osteogenic differentiation of osteoblasts.

OBJECTIVE: Osteoporosis is a severe degenerative chronic metabolic bone disease associated with high fracture risk. Polydatin (PD), a major bioactive component of Polygonum cuspidatum, has antioxidant and anti-inflammatory effects. This study investigated the anti-osteoporotic activity of PD in ovariectomized (OVX) mice and elucidated its underlying molecular mechanisms. SUBJECTS AND METHODS: An osteoporosis mouse model was established using OVX mice. OVX mice were then administered 10 or 40 mg/kg of PD for 60 days. Micro-CT and three-point bending tests were used to determine the therapeutic activities of PD in OVX mice. H&E staining was used to determine whether PD induced hepatorenal toxicity. In addition, the cellular and molecular mechanisms underlying the functionality of PD were elucidated. RESULTS: Micro-CT results showed that compared to control mice, the bone mass of OVX mice was significantly reduced due to estrogen deficiency; however, PD administration significantly elevated bone mass. Furthermore, PD substantially improved the trabecular microstructure parameters of the femur and enhanced bone strength compared with OVX mice. Hepatorenal toxicity was not observed in liver and kidney samples stained with H&E. PD significantly increased the proliferation of pre-osteoblast MC3T3-E1 cells and upregulated the expression of osteogenic differentiation markers compared to those in controls, as determined by qRT-PCR and western blotting. CONCLUSIONS: PD exerted a significant anti-osteoporotic effect in OVX mice by promoting osteogenesis. PD has great potential as a therapeutic option for osteoporosis.

Generation of Vertebra Micro-CT-like Image from MDCT: A Deep-Learning-Based Image Enhancement Approach.

This paper proposes a deep-learning-based image enhancement approach that can generate high-resolution micro-CT-like images from multidetector computed tomography (MDCT). A total of 12,500 MDCT and micro-CT image pairs were obtained from 25 vertebral specimens. Then, a pix2pixHD model was trained and evaluated using the structural similarity index measure (SSIM) and Fréchet inception distance (FID). We performed subjective assessments of the micro-CT-like images based on five aspects. Micro-CT and micro-CT-like image-derived trabecular bone microstructures were compared, and the underlying correlations were analyzed. The results showed that the pix2pixHD method (SSIM, 0.804 ± 0.037 and FID, 43.598 ± 9.108) outperformed the two control methods (pix2pix and CRN) in enhancing MDCT images (p < 0.05). According to the subjective assessment, the pix2pixHD-derived micro-CT-like images showed no significant difference from the micro-CT images in terms of contrast and shadow (p > 0.05) but demonstrated slightly lower noise, sharpness and trabecular bone texture (p < 0.05). Compared with the trabecular microstructure parameters of micro-CT images, those of pix2pixHD-derived micro-CT-like images showed no significant differences in bone volume fraction (BV/TV) (p > 0.05) and significant correlations in trabecular thickness (Tb.Th) and trabecular spacing (Tb.Sp) (Tb.Th, R = 0.90, p < 0.05; Tb.Sp, R = 0.88, p < 0.05). The proposed method can enhance the resolution of MDCT and obtain micro-CT-like images, which may provide new diagnostic criteria and a predictive basis for osteoporosis and related fractures.

Comparison of Trabecular Bone Mineral Density Measurement Using Hounsfield Unit and Trabecular Microstructure in Orthodontic Patients Using Cone-Beam Computed Tomography

The aim of this study was to measure the bone mineral density of specific regions of maxilla, mandible, and first cervical vertebra using the Hounsfield unit and trabecular microstructure pattern analysis and to compare the two methods. In this study, cone-beam computed tomography (CBCT) images were obtained from 58 patients. Trabecular thickness, trabecular number, trabecular separation, and bone volume fraction were measured in 484 regions for trabecular microstructure parameters and Hounsfield unit was measured for the grayscale value. There was no difference in bone mineral density between the right and left side in every site and between males and females. Trabecular thickness and trabecular number were high in the order of anterior base of the maxilla, mandibular body, first cervical vertebra, and mandibular condyle. Bone volume fraction and Hounsfield unit were high in the order of anterior base of the maxilla, mandibular body, mandibular condyle, and first cervical vertebra (p &lt; 0.05). Trabecular thickness, trabecular number, and bone volume fraction was positively correlated to the Hounsfield unit, and trabecular separation was negatively correlated to the Hounsfield unit (p &lt; 0.005). This study suggests that it is possible to compare the bone mineral density of trabecular bone in various sites using the Hounsfield unit and trabecular microstructure pattern analysis.

Effect of Low-Intensity Vibration on Bone Strength, Microstructure, and Adiposity in Pre-Osteoporotic Postmenopausal Women: A Randomized Placebo-Controlled Trial

ABSTRACT There has been evidence that cyclical mechanical stimulation may be osteogenic, thus providing opportunities for nonpharmacological treatment of degenerative bone disease. Here, we applied this technology to a cohort of postmenopausal women with varying bone mineral density (BMD) T-scores at the total hip (−0.524 ± 0.843) and spine (−0.795 ± 1.03) to examine the response to intervention after 1 year of daily treatment with 10 minutes of vibration therapy in a randomized double-blinded trial. The device operates either in an active mode (30 Hz and 0.3 g) or placebo. Primary endpoints were changes in bone stiffness at the distal tibia and marrow adiposity of the vertebrae, based on 3 Tesla high-resolution MRI and spectroscopic imaging, respectively. Secondary outcome variables included distal tibial trabecular microstructural parameters and vertebral deformity determined by MRI, volumetric and areal bone densities derived using peripheral quantitative computed tomography (pQCT) of the tibia, and dual-energy X-ray absorptiometry (DXA)-based BMD of the hip and spine. Device adherence was 83% in the active group (n = 42) and 86% in the placebo group (n = 38) and did not differ between groups (p = .7). The mean 12-month changes in tibial stiffness in the treatment group and placebo group were +1.31 ± 6.05% and −2.55 ± 3.90%, respectively (group difference 3.86%, p = .0096). In the active group, marrow fat fraction significantly decreased after 12 months of intervention (p = .0003), whereas no significant change was observed in the placebo group (p = .7; group difference −1.59%, p = .029). Mean differences of the changes in trabecular bone volume fraction (p = .048) and erosion index (p = .044) were also significant, as was pQCT-derived trabecular volumetric BMD (vBMD; p = .016) at the tibia. The data are commensurate with the hypothesis that vibration therapy is protective against loss in mechanical strength and, further, that the intervention minimizes the shift from the osteoblastic to the adipocytic lineage of mesenchymal stem cells. © 2020 American Society for Bone and Mineral Research (ASBMR).

Quantitative analysis of metal artefacts of dental implant in CBCT image by correlation analysis to micro-CT: A microstructural study.

Quantification of dental implant metal artefacts in CBCT images using correlation analysis of trabecular microstructural parameters from CBCT and micro-CT, and analysis of the effect of varying the angular position of the subject. Polyurethane synthetic bone blocks were first scanned without implants by micro-CT and CBCT. Two dental implants were then placed parallel in the bone blocks and these specimens were scanned by CBCT with different alpha angles. Three volumes of interest (VOI) were set for further analysis. Six microstructural parameters were measured: trabecular thickness (TbTh), trabecular spacing (ThSp), bone volume per total volume (BV/TV), bone surface per total volume (BS/TV), connectivity density (CD) andfractal dimension (FD). Micro-CT measurements were used as a gold standard for CBCT. Spearman correlation coefficients for each microstructural parameter from CBCT and micro-CT were calculated and compared using Steiger's Z test. Without the implants, in VOI1, the Spearman correlation coefficients of TbTh, TbSp, BV/TV, BS/TV, CD and FD were 0.599, 0.76, 0.552, 0.566, 0.664 and 0.607, respectively. With the implants, the correlation coefficients decreased sharply in VOI1. As the alpha angle increased from zero to 90°, the correlation coefficients increased and became significant. Similar results appeared in VOI2. In contrast, in VOI3, the correlation coefficient decreased as the alpha angle increased. Metal artefacts were successfully quantified using microstructural parameters in terms of the image quality of the CBCT. Changes in alpha angle affected the quality of the CBCT image.

Effects of constrained dynamic loading, CKIP‑1 gene knockout and combination stimulations on bone loss caused by mechanical unloading.

Mechanical stimulation plays an important role in maintaining the growth and normal function of the skeletal system. Mechanical unloading occurs, for example, in astronauts spending long periods of time in space or in patients on prolonged bed rest, and causes a rapid loss of bone mass. Casein kinase 2‑interacting protein‑1 (CKIP‑1) is a novel negative bone regulation factor that has been demonstrated to reduce bone loss and enhance bone formation. The aim of this study was to investigate the effect of constrained dynamic loading (Loading) in combination with CKIP‑1 gene knockout (KO) on unloading‑induced bone loss in tail‑suspension mice. The blood serum metabolism index [alkaline phosphatase (ALP) activity and osteocalcin (OCN) levels], tibia mechanical behavior (including bone trabecular microstructure parameters and tibia biomechanical properties), osteoblast‑related gene expression [ALP, OCN, collagen I and bone morphogenetic protein‑2 and osteoprotegerin (OPG)] and osteoclast‑related gene expression [receptor activators of NF‑kB ligand (RANKL)] were measured. The results demonstrated that mice experienced a loss of bone mass after four weeks of tail suspension compared with a wild type group. The mechanical properties, microarchitecture and mRNA expression were significantly increased in mice after Loading+KO treatment (P<0.05). Furthermore, compared with loading or KO alone, the ratio of OPG/RANKL was increased in the combined treatment group. The combined effect of Loading + KO was greater than that observed with loading or KO alone (P<0.05). The present study demonstrates that Loading + KO can counter unloading‑induced bone loss, and combining the two treatments has an additive effect. These results indicate that combined therapy could be a novel strategy for the clinical treatment of disuse osteoporosis associated with space travel or bed rest.

Review of high-resolution peripheral quantitative computed tomography for the assessment of bone microstructure and strength

Trabecular microstructure is an important factor in determining bone strength and physiological function. Normal X-ray and computed tomography (CT) cannot accurately reflect the microstructure of trabecular bone. High-resolution peripheral quantitative computed tomography (HR-pQCT) is a new imaging technique in recent years. It can qualitatively and quantitatively measure the three-dimensional microstructure and volume bone mineral density of trabecular bone in vivo. It has high precision and relative low dose of radiation. This new imaging tool is helpful for us to understand the trabecular microstructure more deeply. The finite element analysis of HR-pQCT data can be used to predict the bone strength accurately. We can assess the risk of osteoporosis and fracture with three-dimensional reconstructed images and trabecular microstructure parameters. In this review, we summarize the technical flow, data parameters and clinical application of HR-pQCT in order to provide some reference for the popularization and extensive application of HR-pQCT.

Trabecular bone microstructure is impaired in the proximal femur of human immunodeficiency virus-infected men with normal bone mineral density.

There is evidence that human immunodeficiency virus (HIV) infection and antiretroviral therapy (ART) are independent risk factors for osteoporosis and fracture which is not solely explained by changes in bone mineral density. Thus, we hypothesized that the assessment of trabecular microstructure might play an important role for bone quality in this population and might explain the increased fracture risk. In this study, we have assessed bone microstructure in the proximal femur using high-resolution magnetic resonance imaging (MRI) as well as in the extremities using high resolution peripheral quantitative computed tomography (HR-pQCT) in HIV-infected men and healthy controls and compared these findings to those based on areal bone mineral density (aBMD) derived from dual X-ray absorptiometry (DXA) which is the standard clinical parameter for the diagnosis of osteoporosis. Eight HIV-infected men and 11 healthy age-matched controls were recruited and informed consent was obtained before each scan. High-resolution MRI of the proximal femur was performed using fully balanced steady state free precession (bSSFP) on a 3T system. Three volumes of interest at corresponding anatomic locations across all subjects were defined based on registrations of a common template. Four MR-based trabecular microstructural parameters were analyzed at each region: fuzzy bone volume fraction (f-BVF), trabecular number (Tb.N), thickness (Tb.Th), and spacing (Tb.Sp). In addition, the distal radius and distal tibia were imaged with HR-pQCT. Four HR-pQCT-based microstructural parameters were analyzed: trabecular bone volume fraction (BV/TV), Tb.N, Tb.Th, and Tb.Sp. Total hip and spine aBMD were determined from DXA. Microstructural bone parameters derived from MRI at the proximal femur and from HR-pQCT at the distal tibia showed significantly lower bone quality in HIV-infected patients compared to healthy controls. In contrast, DXA aBMD data showed no significant differences between HIV-infected patients and healthy controls. Our results suggest that high-resolution imaging is a powerful tool to assess trabecular bone microstructure and can be used to assess bone health in HIV-infected men who show no differences to healthy males by DXA aBMD. Advances in MRI technology have made microstructural imaging at the proximal femur possible. Further studies in larger patient cohorts are clearly warranted.

Analysis of trabecular bone microstructure in osteoporotic femoral heads in human patients: in vivo study using multidetector row computed tomography.

BackgroundLag screw position is very important in the treatment of intertrochanteric femoral fracture to prevent complications such as screw cut-out. Current studies recommend central or inferior placement of the lag screw on the anteroposterior radiograph, and central placement on the lateral radiographs. These reports are based on radiographic evaluation, but few studies have investigated the importance of bone quality at the site of lag screw placement. In this study, we used multidetector row computed tomography (MDCT) to perform in vivo evaluation of the bone microstructure of the femoral head in patients with intertrochanteric femoral fractures.MethodsThis study was approved by the Ethics Committee of Okanami General Hospital. MDCT images were obtained in our hospital from ten patients who had sustained intertrochanteric femoral fracture. Patients who needed computed tomography to confirm fracture morphology were included. We defined six areas as regions of interest (ROI): ROI 1–3 were defined as the femoral head apex area, and ROI 4–6 were defined as the femoral neck area. Trabecular microstructure parameters, including mean bone volume to total volume (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and structure model index (SMI), were evaluated with bone analysis software (TRI/3D-BON). Statistical analyses were performed using EZR software; each parameter among the ROIs was statistically evaluated by analysis of variance (ANOVA) and Tukey’s test. Statistical significance was established at p < 0.05.ResultsIn the apical area, all parameters indicated that ROI 1 (superior) had the highest bone quality and ROI 2 (central) was higher in bone quality than ROI 3 (inferior). In the femoral neck, all parameters indicated that bone quality was significantly greater in ROI 6 (inferior) than ROI 5 (central).Discussion and ConclusionsWe could evaluate bone quality with clinical MDCT in vivo. Bone quality in the central area of the femoral head apical was greater than in the inferior area, and bone quality in the inferior area of the femoral neck was greater than in the central area. Recognizing which area of femoral head has greater bone quality may lead to a better clinical result in treating intertrochanteric femoral fracture.

Collaborative cross mice in a genetic association study reveal new candidate genes for bone microarchitecture

BackgroundThe microstructure of trabecular bone is a composite trait governed by a complex interaction of multiple genetic determinants. Identifying these genetic factors should significantly improve our ability to predict of osteoporosis and its associated risks. Genetic mapping using collaborative cross mice (CC), a genetically diverse recombinant inbred mouse reference panel, offers a powerful tool to identify causal loci at a resolution under one mega base-pairs, with a relatively small cohort size.Here, we utilized 31 CC lines (160 mice of both sexes in total) to perform genome-wide haplotype mapping across 77,808 single-nucleotide polymorphisms (SNPs). Haplotype scans were refined by imputation with the catalogue of sequence variation segregating in the CC to suggest potential candidate genes. Trabecular traits were obtained following microtomographic analysis, performed on 10-μm resolution scans of the femoral distal metaphysis. We measured the trabecular bone volume fraction (BV/TV), number (Tb.N), thickness (Tb.Th), and connectivity density (Conn.D).ResultsHeritability of these traits ranged from 0.6 to 0.7. In addition there was a significant (P < 0.01) sex effect in all traits except Tb.Th. Our haplotype scans yielded six quantitative trait loci (QTL) at 1 % false discovery rate; BV/TV and Tb.Th produced two proximal loci each, on chromosome 2 and 7, respectively, and Tb.N and Conn.D yielded one locus on chromosomes 8 and 14, respectively. We identified candidate genes with previously-reported functions in bone biology, and implicated unexpected genes whose function in bone biology has yet to be assigned. Based on the literature, among the genes that ranked particularly high in our analyses (P < 10-6) and which have a validated causal role in skeletal biology, are Avp, Oxt, B2m (associated with BV/TV), Cnot7 (with Tb.N), Pcsk6, Rgma (with Tb.Th), Rb1, and Cpb2 (with Conn.D). Other candidate genes strongly suggested by our analyses are Sgcz, Fgf20 (associated with Tb.N), and Chd2 (with Tb.Th).ConclusionWe have demonstrated for the first time genome-wide significant association between several genetic loci and trabecular microstructural parameters for genes with previously reported experimental observations, as well as proposing a role for new candidate genes with no previously characterized skeletal function.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2213-x) contains supplementary material, which is available to authorized users.

Association of MRS-Based Vertebral Bone Marrow Fat Fraction with Bone Strength in a Human In Vitro Model.

Bone marrow adiposity has recently gained attention due to its association with bone loss pathophysiology. In this study, ten vertebrae were harvested from fresh human cadavers. Trabecular BMD and microstructure parameters were extracted from MDCT. Bone marrow fat fractions were determined using single-voxel MRS. Failure load (FL) values were assessed by destructive biomechanical testing. Significant correlations (P < 0.05) were observed between MRS-based fat fraction and MDCT-based parameters (up to r = −0.72) and MRS-based fat fraction and FL (r = −0.77). These findings underline the importance of the bone marrow in the pathophysiology and imaging diagnostics of osteoporosis.

In vivo microstructural analysis of the humeral greater tuberosity in patients with rotator cuff tears using multidetector row computed tomography.

BackgroundIn arthroscopic surgery, the suture anchor technique has become popular for rotator cuff repair. Preoperative evaluation of the bone microstructure is of utmost importance because, especially in elderly patients, osteoporotic changes may cause anchor pullout, which results in failure of rotator cuff repair. Many groups have reported humeral microstructural analysis; however, most studies were experiments using porcine specimens or human cadavers. In this study, we used multidetector row computed tomography to successfully perform in vivo evaluation of the bone microstructure of the humeral greater tuberosity in patients with rotator cuff tears.MethodsTen patients were examined. Regions of interest were defined in six quadrants of the greater tuberosity (medial, lateral, and far lateral rows of the anterior and posterior areas). The local bone mineral density and the trabecular microstructural parameters, including the mean bone volume to total volume (BV/TV), trabecular thickness, trabecular separation, and structure model index (SMI), were measured using bone analysis software.ResultsThe BV/TV of the posteromedial region was highest and the SMI of the posteromedial region was lowest. These findings suggest that the bone quality of the posteromedial portion is the highest within the greater tuberosity.ConclusionBecause the bone quality may be correlated with the pullout strength of suture anchors, our method can help to understand the individual and regional variance in bone quality and may lead to the creation of personalized surgical protocols.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2474-15-351) contains supplementary material, which is available to authorized users.

Dependence of mechanical properties of trabecular bone on plate–rod microstructure determined by individual trabecula segmentation (ITS)

Individual trabecula segmentation (ITS) technique can decompose the trabecular bone network into individual trabecular plates and rods and is capable of quantifying the plate/rod-related microstructural characteristics of trabecular bone. This novel technique has been shown to be able to provide in-depth insights into micromechanics and failure mechanisms of human trabecular bone, as well as to distinguish the fracture status independent of area bone mineral density in clinical applications. However, the plate/rod microstructural parameters from ITS have never been correlated to experimentally determined mechanical properties of human trabecular bone. In this study, on-axis cylindrical trabecular bone samples from human proximal tibia (n=22), vertebral body (n=10), and proximal femur (n=21) were harvested, prepared, scanned using micro computed-tomography (µCT), analyzed with ITS and mechanically tested. Regression analyses showed that the plate bone volume fraction (pBV/TV) and axial bone volume fraction (aBV/TV) calculated by ITS analysis correlated the best with elastic modulus (R2=0.96–0.97) and yield strength (R2=0.95–0.96). Trabecular plate-related microstructural parameters correlated highly with elastic modulus and yield strength, while most rod-related parameters were found inversely and only moderately correlated with the mechanical properties. In addition, ITS analysis also identified that trabecular bone at human femoral neck had the highest trabecular plate-related parameters while the other sites were similar with each other in terms of plate–rod microstructure.

Scaling relations between trabecular bone volume fraction and microstructure at different skeletal sites

In this study, we investigated the scaling relations between trabecular bone volume fraction (BV/TV) and parameters of the trabecular microstructure at different skeletal sites.Cylindrical bone samples with a diameter of 8mm were harvested from different skeletal sites of 154 human donors in vitro: 87 from the distal radius, 59/69 from the thoracic/lumbar spine, 51 from the femoral neck, and 83 from the greater trochanter. μCT images were obtained with an isotropic spatial resolution of 26μm. BV/TV and trabecular microstructure parameters (TbN, TbTh, TbSp, scaling indices (< > and σ of α and αz), and Minkowski Functionals (Surface, Curvature, Euler)) were computed for each sample. The regression coefficient β was determined for each skeletal site as the slope of a linear fit in the double-logarithmic representations of the correlations of BV/TV versus the respective microstructure parameter.Statistically significant correlation coefficients ranging from r=0.36 to r=0.97 were observed for BV/TV versus microstructure parameters, except for Curvature and Euler. The regression coefficients β were 0.19 to 0.23 (TbN), 0.21 to 0.30 (TbTh), −0.28 to −0.24 (TbSp), 0.58 to 0.71 (Surface) and 0.12 to 0.16 (<α>), 0.07 to 0.11 (<αz>), −0.44 to −0.30 (σ(α)), and −0.39 to −0.14 (σ(αz)) at the different skeletal sites. The 95% confidence intervals of β overlapped for almost all microstructure parameters at the different skeletal sites. The scaling relations were independent of vertebral fracture status and similar for subjects aged 60–69, 70–79, and >79years.In conclusion, the bone volume fraction–microstructure scaling relations showed a rather universal character.

Relationship of age to bone microstructure independent of areal bone mineral density

Previous studies using dual-energy X-ray absorptiometry (DXA) have demonstrated that age is a major predictor of bone fragility and fracture risk independent of areal bone mineral density (aBMD). Although this aBMD-independent effect of age has been attributed to poor bone "quality," the structural basis for this remains unclear. Because high-resolution peripheral quantitative computed tomography (HRpQCT) can assess bone microarchitecture, we matched younger and older subjects for aBMD at the ultradistal radius and assessed for possible differences in trabecular or cortical microstructure by HRpQCT. From an age-stratified, random sample of community adults, 44 women aged <50 years (mean age 41.0 years) were matched to 44 women aged ≥50 years (mean age 62.7 years) by ultradistal radius aBMD (mean ± SEM, younger and older aBMD 0.475 ± 0.011 and 0.472 ± 0.011 g/cm², respectively), and 57 men aged <50 years (mean age 41.3 years) were matched to 57 men aged ≥50 years (mean age 68.1 years; younger and older aBMD both 0.571 ± 0.008 g/cm²). In these matched subjects, there were no sex-specific differences in trabecular microstructural parameters. However, significant differences were noted in cortical microstructure (all p < 0.05): Older women and men had increased cortical porosity (by 91% and 56%, respectively), total cortical pore volume (by 77% and 61%, respectively), and mean cortical pore diameter (by 9% and 8%, respectively) compared with younger subjects. These findings indicate that younger and older women and men matched for DXA aBMD have similar trabecular microarchitecture but clearly different cortical microstructure, at least at an appendicular site represented by the radius. Further studies are needed to define the extent to which this deterioration in cortical microstructure contributes to the aBMD-independent effect of age on bone fragility and fracture risk at the distal radius and other sites of osteoporotic fractures.

Microstructural Assessment of Cancellous Bone Using 3D Microtomography

Cancellous bones have a porous microstructure and can be modeled as linear elastic solid, heterogeneous and anisotropic. Few studies regarding the morphometric analysis of trabecular bone samples with 3D microtomography have been published so far. The technique has spread worldwide for the characterization of trabecular structures in studies related to bone quality and its relationship with metabolic diseases bone like osteoporosis. In our study cancellous bone samples with cubic and cylindrical geometry were extracted from bovine femur were used to investigate the structural arrangement of bone through high resolution x-ray 3D microtomography (μCT). Four trabecular microstructural parameters (tissue volume, bone volume, bone volume fraction and tissue surface) were measured by 2D (stereological method) and 3D morphometric analysis using the software CTan Analyser supplied by the manufacturer of the microtomograph (SkyScan, model 1172, Belgium). The measurements were done in three main directions (superior-inferior, medial-lateral and anterior-posterior) to investigate the correlation between the 2D and 3D morphometric analysis. The results show a high correlation between the analysis. The x-ray 3D microtomography technique has a great potential for the assessment of bone quality.

The interrelation of trabecular microstructural parameters of the greater tubercle measured for different species

In the present study the trabecular microstructural parameters (bone volume fraction, trabecular thickness, trabecular separation, trabecular number, connectivity density, degree of anisotropy, and structure model index) of the greater tubercle of the humeral head were measured for human healthy, human osteopenic, ovine, bovine, and porcine bones using micro-computed tomography. Except for trabecular thickness and degree of anisotropy the values of the trabecular microstructural parameters generally differed significantly between species. Thus, only the species for which the implant is designed should be used for in vitro mechanical tests on the stability of implants in trabecular bone. Multivariate regression analysis showed that the microstructural parameters have similar principal interrelations in all species. The most significant relations were found between trabecular thickness and bone volume fraction (median (over all species) p < 0.001), trabecular number and bone volume fraction (p = 0.001), the structural change from plates to rods and bone volume fraction (p < 0.001) as well as between connectivity density and trabecular number (p < 0.001). Trabecular thickness, trabecular number, and the structural change from plates to rods each contributed to the bone volume fraction approximately to the same extent. Based on the similar principal interrelations of the trabecular microstructural parameters found in all investigated species the design of trabecular microstructure in the greater tubercle follows similar phenomenological mechanisms in all species. Thus, in vivo experiments on trabecular bone healing and osteoporosis research for application in humans can be conducted in ovine, bovine, or porcine species.

Differences of bone mass and bone structure in osteopenic rat models caused by spinal cord injury and ovariectomy

Both spinal cord injury and ovariectomy can result in ostepenia in rats. SCI induces more deterioration of cortical geometric structure and trabecular microstructure in the proximal tibial metaphysis than OVX. The proximal tibial metaphysis microstructure significantly correlates with its biomechanical properties. The purpose of the present study was to compare the effects of spinal cord injury (SCI) and ovariectomy (OVX) on bone gain in young female rats. Thirty young female Sprague-Dawley rats were randomized into three groups: age-matched intact control (CON), OVX and SCI. The tibiae were assessed for DXA and micro-CT analysis, biomechanical testing, the upper tibial epiphyseal plate height, and blood samples for biochemical analysis. SCI rats showed lower aBMD in the proximal tibiae as compared with OVX rats. Cortical geometric structural parameters of the tibial midshaft in SCI rats were significantly lower than OVX rats. SCI or OVX induced significant changes in all trabecular microstructural parameters in the proximal tibial metaphysis. The trabecular separation (Tb.Sp) and structure mode index (SMI) in SCI rats were significantly higher than in OVX rats. BV/TV explained 84% of the variation of ultimate load of the proximal tibial metaphysis. There was no difference of the upper tibial epiphyseal plate height between SCI and OVX rats. Serum NTX level in SCI rats was significantly higher than in OVX rats. SCI induces more deterioration of cortical bone geometric structure and trabecular microstructure in the proximal tibial metaphysis than OVX.

Structural Analysis of Trabecular Bone of the Proximal Femur Using Multislice Computed Tomography: A Comparison with Dual X-Ray Absorptiometry for Predicting Biomechanical Strength In Vitro

We investigated whether trabecular microstructural parameters determined in multislice spiral computed tomographic (MSCT) images of proximal femur specimens differed in male and female donors and improved the prediction of biomechanical strength of the femur compared to bone mineral density (BMD) and content (BMC) determined with dual X-ray absorptiometry (DXA) as the standard diagnostic technique. Proximal femur specimens (n = 119) were harvested from formalin-fixed human cadavers (mean age 80 +/- 10 years). BMD was determined using DXA. Trabecular microstructural parameters (bone volume fraction, fractal dimension, and trabecular thickness, spacing, and number) were calculated in MSCT-derived images of the proximal femur. Failure load (FL) was measured using a biomechanical side-impact test. An age-, height-, and weight-matched subgroup (n = 54) was chosen to compare male and female donors. BMC, BMD, and structural parameters correlated significantly with FL, with r up to 0.75, 0.71, and 0.71, respectively. In a multiple regression model, an increase up to r = 0.82 was obtained when combining trabecular structural parameters and BMC. BMD differed between males and females only at the trochanter. BMC showed significant gender differences in all regions. This experimental study showed that a combination of BMC and microstructural parameters could improve the prediction of FL, suggesting that bone mass and trabecular structure carry overlapping but complementary information and that a combination of the two provides the best prediction of bone strength. Male donors had larger femora even after adjustment for body size and height, but no differences in trabecular structure were found between males and females.