In Vivo Precision of Digital Topological Skeletonization Based Individual Trabecula Segmentation (ITS) Analysis of Trabecular Microstructure at the Distal Radius and Tibia by HR-pQCT

Individual trabecula segmentation validation in first- and second-generation high-resolution peripheral computed tomography compared to micro-computed tomography in the distal radius and tibia

High-resolution peripheral quantitative computed tomography (HR-pQCT) has been used for in vivo 3D visualization of trabecular microstructure. Second-generation HR-pQCT (HR-pQCT II) has been shown to have good agreement with first generation HR-pQCT (HR-pQCT I). Advanced Individual Trabecula Segmentation (ITS) decomposes the trabecula network into individual plates and rods. ITS based on HR-pQCT I showed a strong correlation to ITS based on micro-computed tomography (μCT) and identified trabecular changes in metabolic bone diseases. ITS based on HR-pQCT II has new potential because of the enhanced resolution but has yet to be validated. The objective of this study was to assess the agreement between ITS based on HR-pQCT I, HR-pQCT II, and μCT to assess the capability of ITS on HR-pQCT images as a tool for studying bone structure. Freshly frozen tibia and radius bones were scanned in the distal region using HR-pQCT I at 82 μm, HR-pQCT II at 60.7 μm, and μCT at 37 μm. Images were registered, binarized, and ITS analysis was performed. Bone volume fraction (pBV/TV, rBV/TV), number density (pTb.N, rTb.N), thickness (pTb.Th, rTb.Th), and plate-to-rod (PR) ratio (pBV/rBV) of trabecular plates and rods were obtained. Paired Student's t-tests with post hoc Bonferroni analysis were used to examine the differences. Linear regression was used to determine the correlation coefficient. The HR-pQCT I parameters were different from the μCT measurements. The HR-pQCT II parameters were different from the μCT measurements except for rTb.N, and the HR-pQCT I parameters were different from the HR-pQCT II measurements except for pTb.Th. The strong correlation between HR-pQCT II and μCT microstructural analysis (R2 = 0.55-0.94) suggests that HR-pQCT II can be used to assess changes in plate and rod microstructure and that values from HR-pQCT I can be corrected.

Ankle flexor torque, size and density are differential determinants of distal tibia trabecular plate-rod morphometry and bone strength: The Ankle Quality Study

HYPOTHESIS

Greater peak torque and higher myotendinous density at the ankle are associated with a more plate-like architecture at the distal tibia.

METHODS

In this cross-sectional study, women and men ≥ 50 years old with no metal implants, reconstructive surgery, muscular dystrophies, or tendinopathies in any leg were recruited by convenience. Isometric ankle dorsi-plantar flexion and inversion-eversion peak torques were measured using dynamometry. HR-pQCT distal tibia scans were completed. Both assessments were completed on the same day on the non-dominant leg. Integral and trabecular vBMD were derived from standard analyses, failure load (FL) was obtained from finite element analysis, plate-specific parameters were computed from individual trabecula segmentation (ITS) analysis, myotendinous density (MyD) and volume fraction (MyV/TV) were computed from soft tissue analysis. pQCT scans of the 66 % mid-leg were performed (500 μm at 15 mm/s) to obtain muscle density (MD) and muscle cross-sectional area (MCSA).

STATISTICAL ANALYSIS

General linear models estimated how ankle muscle group torque and muscle size and density differentially related, both separately and together, to whole-bone properties (integral vBMD, FL) and trabecular morphometry (ITS plate parameters). Models were adjusted for age, sex, BMI, use of glucocorticoids, current osteoarthritis, and participation in moderate to vigorous recreational or sport activities.

RESULTS

Among 105 participants (77 % female, mean age: 63 (10) years, BMI: 25.8 (5.4) kg/m², 25 % with OA, 17 % fracture history, 42 % falls history), all torque measures, particularly ankle dorsiflexion and eversion, were correlates of plate-plate/rod junction density and failure load. However, muscle size and density measures were further associated with vBMD. The effect of greater ankle flexor-extensor torque on more connected bone was stronger when MyD was higher (interaction p < 0.001).

CONCLUSION

Strength of muscles around the ankle are correlates of plate-like trabeculae at the distal tibia, while leaner muscle and myotendinous tissues facilitates better quality bone for stronger ankle muscle torque.

The effect of denosumab and alendronate on trabecular plate and rod microstructure at the distal tibia and radius: A post-hoc HR-pQCT study

BACKGROUND

Age-related trabecular microstructural deterioration and conversion from plate-like trabeculae to rod-like trabeculae occur because of unbalanced rapid remodeling. As denosumab achieves greater remodeling suppression and lower cortical porosity than alendronate, we hypothesized that denosumab might also preserve trabecular plate microstructure, bone stiffness and strength more effectively than alendronate.

METHODS

In this post hoc analysis of a phase 2 study, postmenopausal women randomized to placebo (P, n = 74), denosumab (D, n = 72), or alendronate (A, n = 68). HR-pQCT scans of the distal radius and tibia were performed at baseline and Month-12 (M12). Trabecular compartment was subjected to Individual Trabecula Segmentation while finite element analysis was performed to estimate stiffness and strength. Percent change from baseline at M12 of each parameter was compared between patient groups.

RESULTS

At the distal tibia, in the placebo group, plate surface area (pTb.S, -1.3%) decreased while rod bone volume fraction (rBV/TV, +4.5%) and number (rTb.N, +2.1%) increased. These changes were prevented by denosumab but persisted despite alendronate therapy (pTb.S: -1.7%; rBV/TV: +6.9%; rTb.N: +3.0%). Both treatments improved whole bone stiffness (D: +3.1%; A: +1.8%) and failure load (D: +3.0%; A: +2.2%); improvements using denosumab was significant compared to placebo (stiffness: p = 0.004; failure load: p = 0.003). At the distal radius, denosumab increased total trabecular bone volume fraction (BV/TV, +3.4%) and whole bone failure load (+4.0%), significantly different from placebo (BV/TV: p = 0.044; failure load: p = 0.046). Significantly different effects of either drug on plate and rod microstructure were not detected.

CONCLUSIONS

Denosumab preserved trabecular plate microstructure. Alendronate did not. However, estimated strength did not differ between denosumab and alendronate treated groups.

Update on Imaging-Based Measurement of Bone Mineral Density and Quality

PURPOSE OF REVIEW

Patients with inflammatory arthropathies have a high rate of fragility fractures. Diagnostic assessment and monitoring of bone density and quality are therefore critically important. Here, we review standard and advanced techniques to measure bone density and quality, specifically focusing on patients with inflammatory arthropathies.

RECENT FINDINGS

Current standard procedures are dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). DXA-based newer methods include trabecular bone score (TBS) and vertebral fracture assessment (VFA). More advanced imaging methods to measure bone quality include high-resolution peripheral quantitative computed tomography (HR-pQCT) as well as multi-detector CT (MD-CT) and magnetic resonance imaging (MRI). Quantitative ultrasound has shown promise but is not standard to assess bone fragility. While there are limitations, DXA remains the standard technique to measure density in patients with rheumatological disorders. Newer modalities to measure bone quality may allow better characterization of bone fragility but currently are not standard of care procedures.

Efeito do Diabetes Mellitus tipo I na organização espacial das trabéculas ósseas: análise por meio do processo de esqueletonização

Introdução: Diabetes mellitus é uma doença metabólica que afeta vários órgãos-alvo, incluindo os ossos. OBJETIVO: Avaliar pelo método de esqueletonização o efeito do Diabetes mellitus tipo I (DM1) na microarquitetura de osso esponjoso. Material e Métodos: Quatorze ratos Wistar foram divididos em: Saudável (S, n=7) e Diabético (D, n=7). O DM1 foi induzido por meio de injeção endovenosa de estreptozotocina no grupo D, sendo a confirmação da condição realizada por checagem do nível glicêmico. Os animais foram sacrificados após 35 dias da indução no grupo D, juntamente com os do grupo S. As epífises femorais foram seccionadas, removidas, desmineralizadas e incluídas em parafina. Dois cortes (5 µm) foram obtidos, corados em Hematoxilina e Eosina, e analisados ao Microscópio de Luz. Foi realizada a delimitação interativa das trabéculas ósseas, seguido pelo processo de binarização utilizando threshold global, feita por dois operadores distintos.  Depois, foi realizado o processo de esqueletonização para acesso às características das trabéculas e da rede de interconexão entre elas. Os parâmetros avaliados foram: Área óssea em micrômetros quadrados (B.Ar), Índice de Modelo estrutural (SMI), Dimensão Fractal (FD), Número de trabéculas (Tb.N), Número de ramos (B.N), Número total de junções (Junc.N), Média de pontos terminais (End.p), Média de extensão de cada ramo (R.Le) e Número de junções triplas (Triple.points.N). Resultados: Houve diferença significante apenas no parâmetro SMI para os diferentes operadores (p<0,0001), sendo o mesmo retirado da análise entre diabetes vs saudável. Houve diferença significante na quantidade óssea, sendo maior no grupo S (0,46±0,09) comparado ao grupo D (0,41±0,07) (p=0,0082). Os demais parâmetros não mostraram diferença significante. Conclusão: Conclui-se que a área óssea no grupo saudável é maior em comparação ao DM1. Dentro das limitações deste estudo, parece que a distribuição espacial das trabéculas e suas características de interconexão não são alteradas no diabetes.

Chinese Women in Both the United States and Hong Kong Have Cortical Microstructural Advantages and More Trabecular Plates Compared With White Women

We cross-sectionally compared racial differences in bone quality between Chinese women in the United States (US) and Hong Kong (HK) with white women. A total of 514 women were included. We measured bone geometry, mass, microstructure, and stiffness by high-resolution peripheral quantitative computed tomography (HR-pQCT), individual trabecula segmentation (ITS), and microfinite element analysis (μFEA). After adjustment for age and body mass index (BMI), premenopausal Chinese women in the US and HK had smaller bone area but greater radial cortical (Ct.) thickness and Ct. and trabecular (Tb.) volumetric bone mineral density (vBMD) versus white women but did not differ from each other. At the radius, Tb. number was lower and spacing greater in Chinese women from HK and the US versus white women, whereas Chinese women did not differ from each other. Tb. thickness was highest in Chinese women from HK, intermediate in Chinese-Americans, and lowest in white women. Chinese women had more trabecular plates versus white women, leading to greater age- and BMI-adjusted stiffness for premenopausal Chinese women in HK and the US (both p < 0.05) versus white women. Tibial differences were similar in premenopausal women; analogous trends in microstructure were present in postmenopausal women at the tibia, although stiffness did not differ. In contrast, at the radius, cortical, plate-to-rod ratio, and stiffness were similar between postmenopausal HK and white women. Adjusting for age, weight, and height rather than age and BMI tended to reduce differences in bone size and Tb. parameters but accentuate cortical differences such that Chinese premenopausal women in both locations and postmenopausal women from HK had higher stiffness at both skeletal sites compared with white women. Compared with white women, Chinese women in the US and HK have vBMD and microstructural advantages leading to higher or similar mechanical competence in pre- and postmenopausal women, respectively, despite smaller bone size.

Robust Trabecular Microstructure in Type 2 Diabetes Revealed by Individual Trabecula Segmentation Analysis of HR-pQCT Images

Type 2 diabetes (T2D) patients have an increased fracture risk, which may be partly explained by compromised bone microarchitecture within the cortical bone compartment. Data on trabecular bone parameters in T2D are contradictory. By high-resolution peripheral quantitative computed tomography (HR-pQCT), trabecular microarchitecture is preserved, yet larger trabecular holes are detected in T2D by MRI and DXA-based trabecular bone scores are abnormal. To determine if there are differences in trabecular microstructure, connectivity, and alignment in postmenopausal women with T2D as compared with controls, we performed an individual trabecula segmentation (ITS) analysis on HR-pQCT scans of the distal radius and tibia in 92 women with (n = 42) and without (n = 50) T2D. Unadjusted analyses showed that T2D subjects had greater total trabecular bone volume, trabecular plate volume fraction, plate number density, plate junction density, and axial alignment at the radius and tibia, and increased plate tissue fraction, but decreased rod tissue fraction and rod length at the radius (p < 0.05 for all). After adjustments for clinical covariates, plate number density and plate junction density remained higher at the radius and tibia, whereas total trabecular bone volume was increased and trabecular rod length was decreased at the radius. These differences remained significant after adjustment for hip BMD and trabecular volumetric bone density. Notably, the increased plate-like ITS qualities were seen in those with T2D duration of <10 years, whereas ITS parameters in subjects with T2D duration ≥10 years did not differ from those of control subjects. In conclusion, postmenopausal women with early T2D had a greater plate-like and less rod-like trabecular network. This early advantage in trabecular plate quality does not explain the well-established increased fracture risk in these patients and does not persist in the later stage of T2D. © 2018 American Society for Bone and Mineral Research.

Effect of Low Vitamin D on Volumetric Bone Mineral Density, Bone Microarchitecture, and Stiffness in Primary Hyperparathyroidism

CONTEXT

Patients with 25-hydroxyvitamin D deficiency (25OHD <20 ng/ml) and primary hyperparathyroidism (PHPT) have more severe disease reflected by higher serum PTH levels compared to those with vitamin D levels in the insufficient (20-29 ng/ml) or replete range (≥ 30 ng/ml).

OBJECTIVE

To study the effect of low vitamin D in PHPT on volumetric bone mineral density (vBMD), bone microarchitecture, and bone strength.

DESIGN, SETTING, AND PARTICIPANTS

This is a cross-sectional analysis of 99 PHPT patients with and without 25OHD insufficiency and deficiency from a university hospital.

OUTCOME MEASURES

Bone microarchitecture and strength were assessed with high-resolution peripheral quantitative computed tomography (HRpQCT), microfinite element analysis, and individual trabecula segmentation.

RESULTS

In this cohort, 25OHD levels were deficient in 18.1%, insufficient in 35.4% and replete in 46.5%. Those with lower 25OHD levels had higher PTH (P < .0001), were younger (P = .001) and tended to weigh more (P = .053). There were no age-, weight- and sex-adjusted between-group differences (<20 vs 20-29 vs ≥ 30 ng/ml) in any HRpQCT, microfinite element analysis, or individual trabecula segmentation indices. Because few participants had 25OHD below 20 ng/ml, we also compared those with 25OHD below 30 vs at least 30 ng/ml and found only a trend toward lower adjusted cortical vBMD (3.1%, P = .08) and higher cortical porosity (least squares mean ± SEM 7.5 ± 0.3 vs 6.6 ± 0.3%, P = .07) at the tibia but not the radius. Stiffness did not differ at either site. In multiple regression analysis, 25OHD accounted for only three of the 49.2% known variance in cortical vBMD; 25OHD was not significant in the model for cortical porosity at the tibia.

CONCLUSION

Low 25OHD levels are associated with higher PTH levels in PHPT, but contrary to our hypothesis, these differences did not significantly affect vBMD or microarchitecture, nor did they result in lower stiffness. Low vitamin D in PHPT using current 25OHD thresholds for insufficiency and deficiency did not significantly affect skeletal integrity as assessed by HRpQCT.