Recent progress in bone imaging for osteoporosis research

Murine femur micro-computed tomography and biomechanical datasets for an ovariectomy-induced osteoporosis model

The development of new effective and safer therapies for osteoporosis, in addition to improved diagnostic and prevention strategies, represents a serious need in the scientific community. Micro-CT image-based analyses in association with biomechanical testing have become pivotal tools in identifying osteoporosis in animal models by assessment of bone microarchitecture and resistance, as well as bone strength. Here, we describe a dataset of micro-CT scans and reconstructions of 15 whole femurs and biomechanical tests on contralateral femurs from C57BL/6JOlaHsd ovariectomized (OVX), resembling human post-menopausal osteoporosis, and sham operated (sham) female mice. Data provided for each mouse include: the acquisition images (.tiff), the reconstructed images (.bmp) and an.xls file containing the maximum attenuations for each reconstructed image. Biomechanical data include an.xls file with the recorded load-displacement, a movie with the filmed test and an.xls file collecting all biomechanical results.

Effects of Melandrium firmum Rohrbach on RANKL‑induced osteoclast differentiation and OVX rats

Osteoporosis is a systemic skeletal disease characterized by reduced bone mineral density (BMD), which results in an increased risk of fracture. Melandrium firmum (Siebold & Zucc.) Rohrbach (MFR), 'Wangbulryuhaeng' in Korean, is the dried aerial portion of Melandrii Herba Rohrbach, which is a member of the Caryophyllaceae family and has been used to treat several gynecological conditions as a traditional medicine. However, to the best of our knowledge, the effect of MFR on osteoclast differentiation and osteoporosis has not been assessed. To evaluate the effects of MFR on osteoclast differentiation, tartrate‑resistant acid phosphatase staining, actin ring formation and bone resorption assays were used. Additionally, receptor activator of nuclear factor‑κB ligand‑induced expression of nuclear factor of activated T cell, cytoplasmic 1 (NFATc1) and c‑Fos were measured using western blotting and reverse transcription‑PCR. The expression levels of osteoclast‑related genes were also examined. To further investigate the anti‑osteoporotic effects of MFR in vivo, an ovariectomized (OVX) rat model of menopausal osteoporosis was established. Subsequently, the femoral head was scanned using micro‑computed tomography. The results revealed that MFR suppressed osteoclast differentiation, formation and function. Specifically, MFR reduced the expression levels of osteoclast‑related genes by downregulating transcription factors, such as NFATc1 and c‑Fos. Consistent with the in vitro results, administration of MFR water extract to OVX rats reduced BMD loss, and reduced the expression levels of NFATc1 and cathepsin K in the femoral head. In conclusion, MFR may contribute to alleviate osteoporosis‑like symptoms. These results suggested that MFR may exhibit potential for the prevention and treatment of postmenopausal osteoporosis.

Midterm Comparison of Tibial Fixation between Posterior Cruciate-Retaining and Substituting Porous Tantalum Total Knee Arthroplasty: Three-Dimensional Computed Tomography Analysis

Porous tantalum tibial component is durable with excellent bone ingrowth, higher knee scores, and long-term survivorship. However, to our knowledge, the effect of posterior cruciate-retaining (CR) and posterior cruciate-substituting (PS) porous tantalum tibial component has not been reported. The aim of the current study was to investigate the prosthetic bone quality between CR porous tantalum tibial component and PS using three-dimensional multi-detector-row computed tomography (3D-MDCT). Porous twenty-two (22) CR total knee arthroplasties and 22 PS received 3D-MDCT at every 6 months up to 5.5 years postoperatively to assess prosthetic bone quality (bone marrow contents/tissue volumes [BMC/TV, mg/cm³]) underneath the pegs of porous tantalum modular tibial component. Clinical outcomes (Knee Society score [KSS], Western Ontario and McMaster Universities (WOMAC), FJS-12, Patella score) were evaluated at a minimum follow-up period of 5.5 years. No statistically significant differences were found in age, gender, body mass index, KSS, and BMC/TV volumes in the proximal tibia between the two groups before total knee arthroplasty (TKA). There were also no significant differences between the CR and PS groups with regard to BMC/TV at every 6 months up to 5.5 years after TKA. At 5.5 years postoperatively, there was no significant difference between the two groups in terms of the KSS, WOMAC, forgotten joint score (FJS-12), and Patella score. The present study revealed that the prosthetic bone quality of the CR porous tantalum tibial component and PS were equivalent at every 6 months up to 5.5 years after TKA. This study reflects level II evidence.

Role of oxidative metabolism in osseointegration during spinal fusion

Spinal fusion is a commonly performed orthopedic surgery. Autologous bone graft obtained from the iliac crest is frequently employed to perform spinal fusion. Osteogenic bone marrow stromal (a.k.a. mesenchymal stem) cells (BMSCs) are believed to be responsible for new bone formation and development of the bridging bone during spinal fusion, as these cells are located in both the graft and at the site of fusion. Our previous work revealed the importance of mitochondrial oxidative metabolism in osteogenic differentiation of BMSCs. Our objective here was to determine the impact of BMSC oxidative metabolism on osseointegration of the graft during spinal fusion. The first part of the study was focused on correlating oxidative metabolism in bone graft BMSCs to radiographic outcomes of spinal fusion in human patients. The second part of the study was focused on mechanistically proving the role of BMSC oxidative metabolism in osseointegration during spinal fusion using a genetic mouse model. Patients’ iliac crest-derived graft BMSCs were identified by surface markers. Mitochondrial oxidative function was detected in BMSCs with the potentiometric probe, CMXRos. Spinal fusion radiographic outcomes, determined by the Lenke grade, were correlated to CMXRos signal in BMSCs. A genetic model of high oxidative metabolism, cyclophilin D knockout (CypD KO), was used to perform spinal fusion in mice. Graft osseointegration in mice was assessed with micro-computed tomography. Our study revealed that higher CMXRos signal in patients’ BMSCs correlated with a higher Lenke grade. Mice with higher oxidative metabolism (CypD KO) had greater mineralization of the spinal fusion bridge, as compared to the control mice. We therefore conclude that higher oxidative metabolism in BMSCs correlates with better spinal fusion outcomes in both human patients and in a mouse model. Altogether, our study suggests that promoting oxidative metabolism in osteogenic cells could improve spinal fusion outcomes for patients.

Establishment of the concurrent experimental model of osteoporosis combined with Alzheimer's disease in rat and the dual-effects of echinacoside and acteoside from Cistanche tubulosa

ETHNOPHARMACOLOGICAL RELEVANCE

Cistanche tubulosa is a precious traditional Chinese medicine that has been widely used in the treatment of osteoporosis and Alzheimer's disease. Echinacoside and acteoside are the main active constituents in Cistanche tubulosa that have the pharmacological activities with research value. It has been reported that echinacoside and acteoside could improve the learning and memory ability, promote the proliferation and differentiation of osteoblast.

AIM OF STUDY

Echinacoside and acteoside from Cistanche tubulosa have shown significant activities of anti-osteoporosis and anti-Alzheimer's disease, while these effects have not been studied concurrently in a rat model. The aim of this study was to establish and verify the model of osteoporosis combined with Alzheimer's disease in rat, and to investigate the double effects of echinacoside and acteoside on this concurrent model.

MATERIALS AND METHODS

Three model groups of ovariectomy (OVX), sham surgery with D-galactose and AlCl₃ (D), ovariectomy with D-galactose and AlCl₃ (OVX + D) were set at the same time. The rats in drug treatment groups were ovariectomized. While conducting the intraperitoneal injection of D-galactose and intragastric administration of AlCl₃ in the rats of drug treatment groups, the rats were orally administered echinacoside (90 mg/kg/d), acteoside (90 mg/kg/d) and the positive control drugs of estradiol valerate (0.6 mg/kg/d), donepezil HCl (0.8 mg/kg/d), respectively. After the drug treatment of 8 weeks, Morris Water Maze (MWM) test for 6 days was firstly performed. The rats were then sacrificed to harvest the blood, uteri, femora, tibiae and brain tissues. The serum was used for biochemical tests. The uteri were used for histomorphometry. The right femora were used for Micro-CT and histomorphometry, respectively. The right tibiae were used for biomechanical test. The hippocampus collected on ice box was used for biochemical tests. The brain collected by perfusion was used for histomorphometry.

RESULTS

Compared with Sham group, OVX + D group could significantly reduce the learning and memory ability by causing oxidative damage, impairing neurons in hippocampus and affecting the hydrolysis and synthesis of acetylcholine. Meanwhile, the activities of BALP and TRAP in OVX + D group increased significantly (P < 0.001) as compared to Sham group. In addition, compared with Sham group, the mean bone mineral density obviously decreased (P < 0.05), the trabecular bone mass and microarchitecture were also destroyed significantly in OVX + D group. Furthermore, the maximum load and maximum stress significantly reduced (P < 0.01) and the energy absorption also decreased greatly as compared to Sham group. After administrated with echinacoside and acteoside, the typical pathological features of osteoporosis and Alzheimer's disease were ameliorated.

CONCLUSIONS

The model of osteoporosis combined with Alzheimer's disease in rat was feasible and successfully established. Echinacoside and acteoside also showed some significant effects on this concurrent model, and they could be potential candidates from Cistanche tubulosa with double effects for further study.

Analysis of microscopic bone properties in an osteoporotic sheep model: a combined biomechanics, FE and ToF-SIMS study

The present study deals with the characterization of bone quality in a sheep model of postmenopausal osteoporosis. Sheep were sham operated ( n = 7), ovariectomized ( n = 6), ovariectomized and treated with deficient diet ( n = 8) or ovariectomized, treated with deficient diet and glucocorticoid injections ( n = 7). The focus of the study is on the microscopic properties at tissue level. Microscopic mechanical properties of osteoporotic bone were evaluated by a combination of biomechanical testing and mathematical modelling. Sample stiffness and strength were determined by compression tests and finite-element analysis of stress states was conducted. From this, an averaged microscopic Young's modulus at tissue level was determined. Trabecular structure as well as mineral and collagen distribution in samples of sheep vertebrae were analysed by micro-computed tomography and time-of-flight secondary ion mass spectrometry. In the osteoporotic sheep model, a disturbed fibril structure in the triple treated group was observed, but bone loss only occurred in form of reduced trabecular number and thickness and cortical decline, while quality of the residual bone was preserved. The preserved bone tissue properties in the osteoporotic sheep model allowed for an estimation of bone strength which behaves similar to the human case.

Type 2 Diabetes Mellitus Increases the Risk to Hip Fracture in Postmenopausal Osteoporosis by Deteriorating the Trabecular Bone Microarchitecture and Bone Mass

T2DM is linked to an increase in the fracture rate as compared to the nondiabetic population even with normal or raised bone mineral density (BMD). Hence, bone quality plays an important role in the pathogenesis of skeletal fragility due to T2DM. This study analyzed the changes in the trabecular bone microstructure due to T2DM at various time points in ovariectomized and nonovariectomized rats. Animals were divided into four groups: (I) control (sham), (II) diabetic (sham), (III) ovariectomized, and (IV) ovariectomized with diabetes. The trabecular microarchitecture of the femoral head was characterized using a micro-CT. The differences between the groups were analyzed at 8, 10, and 14 weeks of the onset of T2DM using a two-way analysis of variance and by post hoc multiple comparisons. The diabetic group with and without ovariectomies demonstrated a significant increase in trabecular separation and a decrease in bone volume fraction, trabecular number, and thickness. BMD decreased in ovariectomized diabetic animals at 14 weeks of the onset of T2DM. No significant change was found in connectivity density and degree of anisotropy among groups. The structural model index suggested a change towards a weaker rod-like microstructure in diabetic animals. The data obtained suggested that T2DM affects the trabecular structure within a rat's femoral heads negatively and changes are most significant at a longer duration of T2DM, increasing the risk to hip fractures.

PET-MRI for the Study of Metabolic Bone Disease

PURPOSE OF REVIEW

This review article attempts to summarize the current state and applications of the hybrid imaging modality of PET-MRI to metabolic bone diseases. The advances of PET and MRI are also discussed for metabolic bone diseases as potentially applied via PET-MRI.

RECENT FINDINGS

Etiologies and mechanisms of metabolic bone disease can be complex where molecular changes precede structural changes. Although PET-MRI has yet to be applied directly to metabolic bone disease, possible applications exist since PET, specifically ¹⁸F-NaF PET, can quantitatively track changes in bone metabolism and is useful for assessing treatment, while MRI can give detailed information on bone water concentration, porosity, and architecture through novel techniques such as UTE and ZTE MRI. Earlier detection and further understanding of metabolic bone disease via PET and MRI could lead to better treatment and prevention. More research using this modality is needed to further understand how it can be implemented in this realm.

Peripheral Quantitative Computed Tomography: Review of Evidence and Recommendations for Image Acquisition, Analysis, and Reporting, Among Individuals With Neurological Impairment

In 2015, the International Society for Clinical Densitometry (ISCD) position statement regarding peripheral quantitative computed tomography (pQCT) did not recommend routine use of pQCT, in clinical settings until consistency in image acquisition and analysis protocols are reached, normative studies conducted, and treatment thresholds identified. To date, the lack of consensus-derived recommendations regarding pQCT implementation remains a barrier to implementation of pQCT technology. Thus, based on description of available evidence and literature synthesis, this review recommends the most appropriate pQCT acquisition and analysis protocols for clinical care and research purposes, and recommends specific measures for diagnosis of osteoporosis, assigning fracture risk, and monitoring osteoporosis treatment effectiveness, among patients with neurological impairment. A systematic literature search of MEDLINE, EMBASE^©, CINAHL, and PubMed for available pQCT studies assessing bone health was carried out from inception to August 8th, 2017. The search was limited to individuals with neurological impairment (spinal cord injury, stroke, and multiple sclerosis) as these groups have rapid and severe regional declines in bone mass. Of 923 references, we identified 69 that met review inclusion criteria. The majority of studies (n = 60) used the Stratec XCT 2000/3000 pQCT scanners as reflected in our evaluation of acquisition and analysis protocols. Overall congruence with the ISCD Official Positions was poor. Only 11% (n = 6) studies met quality reporting criteria for image acquisition and 32% (n = 19) reported their data analysis in a format suitable for reproduction. Therefore, based on current literature synthesis, ISCD position statement standards and the authors' expertise, we propose acquisition and analysis protocols at the radius, tibia, and femur sites using Stratec XCT 2000/3000 pQCT scanners among patients with neurological impairment for clinical and research purposes in order to drive practice change, develop normative datasets and complete future meta-analysis to inform fracture risk and treatment efficacy evaluation.

Use of porous monoblock patella component should avoid for patient with patella baja

Background

Although many studies have evaluated the success of porous tantalum component in primary and revision cementless total knee arthroplasty (TKA) cases, few studies have reported the breakage of porous tantalum monoblock patella component (PTMP). The purpose of this study was to investigate the radiographic outcomes of breakage of PTMP at short-term follow up.

Methods

This was a retrospective study of 49 consecutive knees in 43 patients who underwent TKA surgery between September 2012 and March 2014. Bone marrow contents/tissue volumes (BMC/TV. mg/cm³) were evaluated using 2-dimensional osteomorphometry software with 2D- multi-detector-row computed tomography (2D-MDCT) to measure fixation of the bone-prosthesis interface with patella at 6, 12, and 24 months after surgery. Clinical follow up was obtained by reviewing each patient at orthopedic record.

Results

We experienced a case that resulted in breakage of PTMP without traumatic episode at 26 months after surgery. Relative changes of Bone Mineral Contents per Tissue Volume. (BMC/TV mg/cm³) at ROI. 1 (superior border of the patella) and ROI. 2 (peg of patella) were significantly higher than ROI.3 (inferior border of patella) at 6, 12 and 24 months after surgery (p < 0.001. p < 0.01). Patient with breakage of PTMP has patella baja (Insall- Salvati ratio: 0.72), and the relative change of BMC/TV at ROI.1 and 2 for patients who experienced a breakage of PTMP was higher than any other patients.

Conclusion

The present study revealed that the use of PTMP should be avoided for patients with patella baja.

Is there a relationship between the load distribution on the tibial plateau and hip knee ankle angle after TKA?

INTRODUCTION

This study asked whether differences in coronal alignment after total knee arthroplasty (TKA) affect the load distribution on the tibial plateau. The aim of this study was to investigate the correlation between coronal alignment and the load distribution on the tibial plateau after TKA, using three-dimensional multi-detector-row-computed tomography (3D-MDCT).

MATERIALS AND METHODS

In this study, we performed 84 cementless TKA with porous tantalum modular tibial component (PTMT) and divided into three groups based on post-operative hip-knee-ankle (HKA) angle: varus alignment group (n = 22), (176° ≧) neutral alignment group (n = 45), (180° ± 3°), and valgus alignment group (n = 17) (184° ≦).The changes in bone quality parameters of trabecular patterns under peg of PTMT were interpreted as load distribution due to changes in alignment. The relationship between HKA angle and load distribution on the tibial plateau was analyzed every 6 months for 4.5 years by measuring Bone marrow contents/tissue volumes (mg/cm³) and bone volumes/tissue volumes (%) under peg of porous tantalum modular tibial component by visualizing three dimensionally with 3D-osteo-morphometry software.

RESULTS

There were no correlations between HKA angle and the load distribution on the tibial plateau after TKA at all periods. There was a significantly higher increase in the medial region than the lateral about the BMC/TV and BV/TV values, regardless of the post-operative alignment after TKA for all periods. The relative BMC/TV and BV/TV changes at medial region in varus alignment group were significantly lower than the neutral and the valgus alignment groups of pre-operative medial osteoarthritis of the knee.

CONCLUSIONS

As far, it can be concluded by the study and the methods used therein that there were no relationships between the load distribution on the tibial plateau and HKA angle after TKA.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

Fat Mass Is Positively Associated with Estimated Hip Bone Strength among Chinese Men Aged 50 Years and above with Low Levels of Lean Mass

This study investigated the relationships of fat mass (FM) and lean mass (LM) with estimated hip bone strength in Chinese men aged 50-80 years (median value: 62.0 years). A cross-sectional study including 889 men was conducted in Guangzhou, China. Body composition and hip bone parameters were generated by dual-energy X-ray absorptiometry (DXA). The relationships of the LM index (LMI) and the FM index (FMI) with bone phenotypes were detected by generalised additive models and multiple linear regression. The associations between the FMI and the bone variables in LMI tertiles were further analysed. The FMI possessed a linear relationship with greater estimated hip bone strength after adjustment for the potential confounders (p < 0.05). Linear relationships were also observed for the LMI with most bone phenotypes, except for the cross-sectional area (p < 0.05). The contribution of the LMI (4.0%-12.8%) was greater than that of the FMI (2.0%-5.7%). The associations between the FMI and bone phenotypes became weaker after controlling for LMI. Further analyses showed that estimated bone strength ascended with FMI in the lowest LMI tertile (p < 0.05), but not in the subgroups with a higher LMI. This study suggested that LM played a critical role in bone health in middle-aged and elderly Chinese men, and that the maintenance of adequate FM could help to promote bone acquisition in relatively thin men.

Potential of PET-MRI for imaging of non-oncologic musculoskeletal disease

Early detection of musculoskeletal disease leads to improved therapies and patient outcomes, and would benefit greatly from imaging at the cellular and molecular level. As it becomes clear that assessment of multiple tissues and functional processes are often necessary to study the complex pathogenesis of musculoskeletal disorders, the role of multi-modality molecular imaging becomes increasingly important. New positron emission tomography-magnetic resonance imaging (PET-MRI) systems offer to combine high-resolution MRI with simultaneous molecular information from PET to study the multifaceted processes involved in numerous musculoskeletal disorders. In this article, we aim to outline the potential clinical utility of hybrid PET-MRI to these non-oncologic musculoskeletal diseases. We summarize current applications of PET molecular imaging in osteoarthritis (OA), rheumatoid arthritis (RA), metabolic bone diseases and neuropathic peripheral pain. Advanced MRI approaches that reveal biochemical and functional information offer complementary assessment in soft tissues. Additionally, we discuss technical considerations for hybrid PET-MR imaging including MR attenuation correction, workflow, radiation dose, and quantification.

Quantitative analysis of tibial subchondral bone: Texture analysis outperforms conventional trabecular microarchitecture analysis

BACKGROUND

The aim of this study was to compare two different methods of quantitative assessment of tibial subchondral bone in osteoarthritis (OA): statistical texture analysis (sTA) and trabecular microarchitecture analysis (tMA).

METHODS

Asymptomatic controls aged 20-30 (n = 10), patients aged 40-50 with chronic knee pain but without established OA (n = 10) and patients aged 55-85 with advanced OA scheduled for knee replacement (n = 10) underwent knee MR imaging at 3 Tesla with a three-dimensional gradient echo sequence to allow sTA and tMA. tMA and sTA features were calculated using region of interest creation in the medial (MT) and lateral (LT) tibial subchondral bone. Features were compared between groups using one-way analysis of variance. The two most discriminating tMA and sTA features were used to construct exploratory discriminant functions to assess the ability of the two methods to classify participants.

RESULTS

No tMA features were significantly different between groups at either MT or LT. 17/20 and 11/20 sTA features were significantly different between groups at the MT/LT, respectively (P < 0.001). Discriminant functions created using tMA features classified 12/30 participants correctly (40% accuracy; 95% confidence interval [CI], 22-58%) based on MT data and 9/30 correctly (30%,; 95% CI, 14-46) based on LT data. Discriminant functions using sTA features classified 16/30 participants correctly (53%; 95% CI, 35-71) based on MT data and 14/30 correctly (47%; 95% CI, 29-65) based on LT data.

CONCLUSION

sTA features showed more significant differences between the three study groups and improved classification accuracy compared with tMA features.

ASSESSMENT OF OSTEOPOROTIC FEMORAL FRACTURE RISK: FINITE ELEMENT METHOD AS A POTENTIAL REPLACEMENT FOR CURRENT CLINICAL TECHNIQUES

Femoral fracture risk prediction is a necessary step preceding effective pharmacological intervention or pre-operative planning. Current clinical methods for fracture risk prediction rely on 2D imaging methods and have limited predictive value. Researchers are therefore trying to find improved methods for fracture prediction. During last few decades, many studies have focused on integration of 3D imaging techniques and the finite element (FE) method to improve the accuracy of fracture assessment techniques. In this paper, we review the recent advances in FE and other techniques for predicting the risk of femoral fractures. Based on a number of selected studies, the different steps that are involved in generation of patient-specific FE models are reviewed with particular emphasis on the fracture criteria. The inaccuracies that might arise due to the imperfections of the involved steps are also discussed. It is concluded that compared to image- and geometry-based techniques, FE is a more promising approach for prediction of fracture loads. However, certain technological advancements in FE modeling protocols are required before FE modeling can be recruited in clinical settings.

Insight into bone-derived biological apatite: ultrastructure and effect of thermal treatment

Objectives. This study aims at examining the ultrastructure of bone-derived biological apatite (BAp) from a series of small vertebrates and the effect of thermal treatment on its physiochemical properties. Materials and Methods. Femurs/fin rays and vertebral bodies of 5 kinds of small vertebrates were firstly analyzed with X-ray microtomography. Subsequently, BAp was obtained with thermal treatment and low power plasma ashing, respectively. The properties of BAp, including morphology, functional groups, and crystal characteristics were then analyzed. Results. The bones of grouper and hairtail were mainly composed of condensed bone. Spongy bone showed different distribution in the bones from frog, rat, and pigeon. No significant difference was found in bone mineral density of condensed bone and trabecular thickness of spongy bone. Only platelet-like crystals were observed for BAp obtained by plasma ashing, while rod-like and irregular crystals were both harvested from the bones treated by sintering. A much higher degree of crystallinity and larger crystal size but a lower content of carbonate were detected in the latter. Conclusion. Platelet-like BAp is the common inorganic component of vertebrate bones. BAp distributing in condensed and spongy bone may exhibit differing thermal reactivity. Thermal treatment may alter BAp's in vivo structure and composition.

Using Micro-CT Derived Bone Microarchitecture to Analyze Bone Stiffness - A Case Study on Osteoporosis Rat Bone

Micro-computed tomography (Micro-CT) images can be used to quantitatively represent bone geometry through a range of computed attenuation-based parameters. Nonetheless, those parameters remain indirect indices of bone microarchitectural strength and require further computational tools to interpret bone structural stiffness and potential for mechanical failure. Finite element analysis (FEA) can be applied to measure trabecular bone stiffness and potentially predict the location of structural failure in preclinical animal models of osteoporosis, although that procedure from image segmentation of Micro-CT derived bone geometry to FEA is often challenging and computationally expensive, resulting in failure of the model to build. Notably, the selection of resolution and threshold for bone segmentation are key steps that greatly affect computational complexity and validity. In the following study, we evaluated an approach whereby Micro-CT derived grayscale attenuation and segmentation data guided the selection of trabecular bone for analysis by FEA. We further correlated those FEA results to both two- and three-dimensional bone microarchitecture from sham and ovariectomized (OVX) rats (n = 10/group). A virtual cylinder of vertebral trabecular bone 40% in length from the caudal side was selected for FEA, because Micro-CT based image analysis indicated the largest differences in microarchitecture between the two groups resided there. Bone stiffness was calculated using FEA and statistically correlated with the three-dimensional values of bone volume/tissue volume, bone mineral density, fractal dimension, trabecular separation, and trabecular bone pattern factor. Our method simplified the process for the assessment of trabecular bone stiffness by FEA from Micro-CT images and highlighted the importance of bone microarchitecture in conferring significantly increased bone quality capable of resisting failure due to increased mechanical loading.

[Visualization of local cortical defects in Charcot foot using microcomputed tomography]

BACKGROUND

In the pathogenesis of diabetic neuropathic osteoarthropathy (Charcot's foot) fractures cause chronic destruction of soft tissue and bone structure. To improve an early diagnosis of Charcot foot, modern diagnostic imaging is mainly based on magnetic resonance imaging (MRI), for example in relation to the detection of cortical bone fractures.

OBJECTIVES

In this study we investigated the cortical microstructure in cases of Charcot foot with respect to fractures and porosity in order to visualize local cortical defects. This may substantiate recent efforts in a reclassification based on MRI.

MATERIAL AND METHODS

Using microcomputed tomography (microCT) we investigated bone parameters, such as cortical thickness and porosity in order to quantify the local metatarsal microstructure in cases of Charcot foot.

RESULTS

All bone samples showed a high degree of cortical porosity including pores that perforated the cortical bone. The data suggest that areas with reduced cortical thickness coincide with large cortical pores that may serve as initial points for fractures. Whether the detected microfractures are physiological or artefacts of preparation could not be determined.

CONCLUSION

By means of microCT we were able to visualize and quantify the extent of cortical porosity for the first time in high resolution. The data suggest that both cortical fractures and cortical porosity play an important role in the pathogenesis in cases of Charcot foot.

Trabecular microfractures in the femoral head with osteoporosis: analysis of microcallus formations by synchrotron radiation micro CT

Trabecular bone microfracture pathogenesis and associated healing processes are not well understood. We analyzed the microcalluses that form subsequent to microfractures in patients with osteoporosis (OP) using synchrotron radiation micro CT (SRCT). Subchondral bone columns were extracted from the femoral heads of 11 female patients with a femoral neck fracture. SRCT scanning was performed with 5.9×5.9×5.9 μm3 voxel size and the microcallus number was measured in a 5-mm cubic subchondral bone region. The trabecular bone microstructure was measured and its relationship to the microcallus number was analyzed. In addition, the degree of mineralization of the microcallus region and that of the rest of the trabecular bone were measured and compared. Microcallus formations were detected in all cases, with a mean microcallus number of 4.9 (range, 2-11). The microcallus number had a significantly negative correlation with bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and degree of mineralization, and had a positive correlation with specific bone surface (BS/BV). The degree of mineralization of the microcallus region was lower than that of the rest of the trabecular bone and had a wider range of values. Microcallus formations were frequently detected in patients with OP, and more prevalent in the bone with thinner trabeculae, suggesting microfractures might occur due to activities of daily living as the OP progresses. The degree of mineralization of microcallus might represent the process of bone healing from immature woven bone to mature trabecular bone.

Measurement of volumetric bone mineral density in proximal humerus using quantitative computed tomography in patients with unilateral rotator cuff tear

BACKGROUND

The first purpose of this study was to reveal the clinically important region-specific volumetric bone mineral density (vBMD) of the proximal humerus in patients with unilateral rotator cuff tear (RCT), and the second was to evaluate the relationship between vBMD of the proximal humerus and BMD of the hip and lumbar spine measured using conventional dual-energy X-ray absorptiometry. Finally, we assessed whether any clinical factor could predict local osteoporosis of the proximal humerus.

METHODS

The study enrolled 65 patients who underwent arthroscopic repair of a unilateral RCT between April 2010 and July 2011 and had computed tomography scans of bilateral proximal humeri. Considering the suture bridge technique for RCT repair to be the leading treatment, region-specific BMD was measured in 7 volumetric blocks in the proximal humerus. Image and quantification processing was used to calculate the vBMD of each block.

RESULTS

The vBMD values in all 7 blocks of the symptomatic shoulder were significantly lower than those of the asymptomatic contralateral shoulder (P < .05). Regardless of RCT, the greater tuberosity showed significant location-dependence in vBMD value; that is, the vBMD value was the highest in the posterolateral portion and the lowest in the medial portions. No significant correlation was found between vBMD of the greater tuberosity and clinical factors except female gender.

CONCLUSION

The present study demonstrated the regional and bilateral differences in vBMD within the greater tuberosity in patients with unilateral RCT. Aside from female gender, no other clinical factors presented as risk factors for a higher possibility of osteoporosis.

Multidetector-row computed tomography is useful to evaluate the therapeutic effects of bisphosphonates in glucocorticoid-induced osteoporosis

Osteoporosis is one of the major complications of glucocorticoid therapy. Osteoporosis is usually defined by the levels of bone mineral density (BMD) assessed by dual energy X-ray absorptiometry (DEXA); however, glucocorticoids often induce fractures in patients with normal BMD. Thus, novel diagnostic approaches are required. In this study, we examined whether multidetector-row computed tomography (MDCT) is useful to assess the bone status in glucocorticoid-induced osteoporosis (GIO). Because bisphosphonates have been proven to prevent bone fracture in GIO, we tried to detect the therapeutic effects of bisphosphonates in GIO by MDCT. Fifteen Japanese patients with immunoglobulin A nephropathy who had normal renal function were enrolled in this open-label randomized trial. Patients were randomly divided into three groups-calcitriol (VD), menatetrenone (VK), or bisphosphonate (Bis). Bone conditions were analyzed twice by three different methods-bone turnover markers, DEXA, and MDCT-at the start and 6 months after the start of therapy. Both bone markers and DEXA could not detect significant differences among the therapeutic groups; however, MDCT-based analyses detected the preventive effects of bisphosphonates in GIO. Compared to VD, Bis improved structural indices, such as bone volume fraction, trabecular separation, marrow star volume, and structure model index whereas the difference between VD and VK was not significant. Finite element analysis revealed that simulated fracture load in the Bis group was significantly improved. These findings suggested that MDCT-based assessment is superior to bone markers and/or DEXA in assessing the therapeutic effect of bisphosphonates on GIO.

Trabecular bone structure analysis of the spine using clinical MDCT: can it predict vertebral bone strength?

Recent technical improvements have made it possible to determine trabecular bone structure parameters of the spine using clinical multi-detector computed tomography (MDCT). Therefore, the purpose of this study was to analyze trabecular bone structure parameters obtained from clinical MDCT in relation to high resolution peripheral quantitative computed tomography (HR-pQCT) as a standard of reference and to investigate whether clinical MDCT can predict vertebral bone strength. Fourteen functional spinal segment units between T7 and L3 were harvested from 14 formalin-fixed human cadavers (11 women and 3 men; age 84 ± 10 years). All functional spinal segment units were examined using HR-pQCT (isotropic voxel size of 41 μm(3)) and a clinical whole-body MDCT (interpolated voxel size of 146 × 146 × 300 μm(3)). Trabecular bone structure analyses (histomorphometric and texture measures) were performed in the HR-pQCT as well as MDCT images. Vertebral failure load (FL) of the functional spinal segment units was determined in an uniaxial biomechanical test. The HR-pQCT and MDCT derived trabecular bone structure parameters showed correlations ranging from r = 0.60 to r = 0.90 (p < 0.05). Correlations between trabecular bone structure parameters and FL amounted up to r = 0.86 (p < 0.05) using the HR-pQCT images, and up to r = 0.79 (p < 0.05) using the MDCT images. Correlation coefficients of FL versus trabecular bone structure parameters obtained with HR-pQCT and MDCT were not significantly different (p > 0.05). In this cadaver model, the spatial resolution of clinically available whole-body MDCT scanners was suitable for trabecular bone structure analysis of the spine and to predict vertebral bone strength.

Osteoporosis in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is being regarded as a heterogeneous disease with clinically significant pulmonary and extrapulmonary manifestations, such as emphysema, cardiovascular disease and osteoporosis. Osteoporosis is characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to enhanced bone fragility and, consequently, an increased risk of fracture. Fractures resulting from osteoporosis might contribute to increased morbidity and mortality, particularly in COPD patients. The high prevalence of osteoporosis in COPD patients is assumed to be due to common risk factors, such as older age and tobacco smoking, and COPD-specific risk factors, such as systemic inflammation, vitamin D deficiency and the use of oral or inhaled corticosteroids. This review provides a state-of-the-art summary of the prevalence, pathophysiology, diagnosis, risk factors and treatment of osteoporosis in COPD patients. It also discusses potential mechanisms linking COPD with osteoporosis.

Applicability of ToF-SIMS for monitoring compositional changes in bone in a long-term animal model

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a well-established technique in material sciences but has not yet been widely explored for implementation in life sciences. Here, we demonstrate the applicability and advantages of ToF-SIMS analysis for the study of minerals and biomolecules in osseous tissue. The locally resolved analysis of fragment ions deriving from the sample surface enables imaging and differentiation of bone tissue and facilitates histology on non-stained cross sections. In a rat model, bilateral ovariectomy combined with either a multi-deficiency diet or steroid treatment was carried out to create osteoporotic conditions. We focused our study on the Ca content of the mineralized tissue and monitored its decline. Calcium mass images of cross sections show the progressive degenerative changes in the bone. We observed a decreased Ca concentration in the edge region of the trabeculae and a decline in the Ca/P ratio. Additionally, we focused on the non-mineralized matrix and identified fragment ions that are characteristic for the collagen matrix. We observed trabeculae with wide ranges of non-mineralized collagen for the diet group owing to an impaired mineralization process. Here, the advantage of coeval monitoring of collagen and minerals indicated an osteomalacic model rather than an osteoporotic one.

Advances in bone imaging for osteoporosis

The diagnosis and management of osteoporosis have been improved by the development of new quantitative methods of skeletal assessment and by the availability of an increasing number of therapeutic options, respectively. A number of imaging methods exist and all have advantages and disadvantages. Dual-energy X-ray absorptiometry (DXA) is the most widely available and commonly utilized method for clinical diagnosis of osteoporosis and will remain so for the foreseeable future. The WHO 10-year fracture risk assessment tool (FRAX(®)) will improve clinical use of DXA and the cost-effectiveness of therapeutic intervention. Improved reporting of radiographic features that suggest osteoporosis and the presence of vertebral fracture, which are powerful predictors of future fractures, could increase the frequency of appropriate DXA referrals. Quantitative CT remains predominantly a research tool, but has advantages over DXA--allowing measurement of volumetric density, separate measures of cortical and trabecular bone density, and evaluation of bone shape and size. High resolution imaging, using both CT and MRI, has been introduced to measure trabecular and cortical bone microstructure. Although these methods provide detailed insights into the effects of disease and therapies on bone, they are technically challenging and not widely available, so they are unlikely to be used in clinical practice.

Diagnosis of osteoarthritis and prognosis of tibial cartilage loss by quantification of tibia trabecular bone from MRI

A longitudinal study was used to investigate the quantification of osteoarthritis and prediction of tibial cartilage loss by analysis of the tibia trabecular bone from magnetic resonance images of knees. The Kellgren Lawrence (KL) grades were determined by radiologists and the levels of cartilage loss were assessed by a segmentation process. Aiming to quantify and potentially capture the structure of the trabecular bone anatomy, a machine learning approach used a set of texture features for training a classifier to recognize the trabecular bone of a knee with radiographic osteoarthritis. Using cross-validation, the bone structure marker was used to estimate for each knee both the probability of having radiographic osteoarthritis (KL >1) and the probability of rapid cartilage volume loss. The diagnostic ability reached a median area under the receiver-operator-characteristics curve of 0.92 (P < 0.0001), and the prognosis had odds ratio of 3.9 (95% confidence interval: 2.4-6.5). The medians of cartilage loss of the subjects classified as slow and rapid progressors were 1.1% and 4.9% per year, respectively. A preliminary radiological reading of the high and low risk knees put forward an hypothesis of which pathologies the bone marker could be capturing to define the prognosis of cartilage loss.

Application of ex vivo micro-computed tomography for assessment of in vivo fluorescence and plain radiographic imaging for monitoring bone metastases and osteolytic lesions

The intracardiac injection model is a commonly used in vivo model to test therapeutic response in bone metastases. However, few studies have critically compared the performance of different imaging methods in terms of sensitivity and quantitative assessment of osteolytic lesions. We performed in vivo optical and plain radiographic imaging of bone metastases followed by high-sensitivity ex vivo micro-computed tomography (micro-CT) imaging. This approach allowed for quantitative assessment of in vivo imaging techniques using fluorescence and plain radiography. Comparison of lesions detected in vivo by fluorescent optical imaging with ex vivo micro-CT revealed that the limited spatial resolution of fluorescent optical imaging may underestimate the number of bone metastases. Radiography was compared with micro-CT for the detection of osteolytic lesions. When using dichotomous yes/no grading, there was a 64% agreement in detection of osteolytic lesions. When subjective semiquantitative grading methods were used to assess the extent of osteolytic lesions, a positive association between the micro-CT grades and the square root of the radiography-based grades was observed (p < 0.05). Micro-CT also showed a significant association with fluorescent optical values; however, no such association was observed between lesion scores based on radiographs and those based on fluorescent imaging. The findings reveal an approximate two-fold sensitivity for micro-CT compared to plain radiography in the detection of osteolytic lesions. Significant associations between micro-CT-based osteolytic lesion grade and tumor growth characterized by increased fluorescent area document the value of these two techniques for the assessment of osteolytic bone metastases.

In vivo estimation of bone stiffness at the distal femur and proximal tibia using ultra-high-field 7-Tesla magnetic resonance imaging and micro-finite element analysis

The goal of this study was to demonstrate the feasibility of using 7-Tesla (7T) magnetic resonance imaging (MRI) and micro-finite element analysis (µFEA) to evaluate mechanical and structural properties of whole, cortical, and trabecular bone at the distal femur and proximal tibia in vivo. 14 healthy subjects were recruited (age 40.7 ± 15.7 years). The right knee was scanned on a 7T MRI scanner using a 28 channel-receive knee coil and a three-dimensional fast low-angle shot sequence (TR/TE 20 ms/5.02 ms, 0.234 mm × 0.234 mm × 1 mm, 80 axial images, 7 min 9 s). Bone was analyzed at the distal femoral metaphysis, femoral condyles, and tibial plateau. Whole, cortical, and trabecular bone stiffness was computed using µFEA. Bone volume fraction (BVF), bone areas, and cortical thickness were measured. Trabecular bone stiffness (933.7 ± 433.3 MPa) was greater than cortical bone stiffness (216 ± 152 MPa) at all three locations (P < 0.05). Across locations, there were no differences in bone stiffness (whole, cortical, or trabecular). Whole, cortical, and trabecular bone stiffness correlated with BVF (R ≥ 0.69, P < 0.05) and inversely correlated with corresponding whole, cortical, and trabecular areas (R ≤ -0.54, P < 0.05), but not with cortical thickness (R < -0.11, P > 0.05). Whole, cortical, and trabecular stiffness correlated with body mass index (R ≥ 0.62, P < 0.05). In conclusion, at the distal femur and proximal tibia, trabecular bone contributes 66-74% of whole bone stiffness. 7T MRI and µFEA may be used as a method to provide insight into how structural properties of cortical or trabecular bone affect bone mechanical competence in vivo.

MR spectroscopy and micro-CT in evaluation of osteoporosis model in rabbits: comparison with histopathology

PURPOSE

To explore the evidence of regular alteration of bone quality in osteoporosis dynamically examined by MRS and micro-CT, comparing with histopathology.

METHODS

Forty rabbits were allocated into two groups. Group A were used as sham. Group B underwent bilateral ovariectomy (OVX) combined with daily intramuscular methylprednisolone, underwent MR spectroscopy, micro-CT, and histopathology of L5 at 2, 4, 8, and 10 weeks after operation.

RESULTS

Fat fraction as shown by MRS in Group B was significantly increased over the time course of osteoporosis development with significant difference between two groups at 4, 8, and 10 weeks after OVX. Continuous deterioration of cancellous bone architecture in Group B, was first detected at week 4. FF value in group B correlated with micro-CT parameters. Marrow fat as measured by MR and CT was positively correlated with both the mean density and diameter of adipocytes (both of which increased over time).

CONCLUSIONS

Marrow adipogenesis occurs in synchrony with deterioration of trabecular microarchitecture.MRS may be valuable to assess the pathophysiological changes of bone marrow in osteoporosis in early stage.

KEY POINTS

MRS revealed gradually increasing bone marrow fat in rabbits rendered osteoporotic. Marrow adipogenesis occurs in synchrony with deterioration of trabecular microarchitecture. Pathology revealed an early increase in number of marrow adipocytes in osteoporosis. MRS may help assess early pathophysiological bone marrow changes in osteoporosis.

Effect of eldecalcitol, an active vitamin D analog, on hip structure and biomechanical properties: 3D assessment by clinical CT

The effects of an active vitamin D analog, eldecalcitol (ELD), on bone mineral density (BMD), bone geometry, and biomechanical properties of the proximal femur were investigated by using clinical CT. The subjects--a subgroup of a recent randomized, double-blind study comparing anti-fracture efficacy of ELD with alfacalcidol (ALF) - constituted 193 ambulatory patients with osteoporosis (189 postmenopausal women and 4 men aged 52-85 years, average ± SD: 70.9 ± 6.92 years) enrolled at 11 institutions. Multidetector-row CT data was acquired at baseline and at completion of 144 weeks' treatment. Cross-sectional densitometric and geometric parameters of the femoral neck were derived from three-dimensional CT data. Biomechanical properties including cross-sectional moment of inertia (CSMI), section modulus (SM) and buckling ratio (BR) of the femoral neck, and CSMI of the femoral shaft were also calculated. We found that, (1) with respect to the femoral neck cross-sectional parameters (total bone), in the ALF group, volumetric BMD (vBMD) decreased but bone mass was maintained and cross-sectional area (CSA) increased. In contrast, ELD maintained vBMD with a significant increase in bone mass and a trend toward increased CSA. (2) With respect to the femoral neck cross-sectional parameters (cortex), cortical thickness decreased in the ALF group, but was maintained in the ELD group. In the ALF group, vBMD and bone mass increased, and CSA was maintained. In the ELD group, vBMD, CSA, and bone mass increased. (3) With respect to the biomechanical properties of the femoral neck, ELD improved CSMI and SM to a greater extent than did ALF. BR increased in both the ALF and ELD groups. (4) With respect to the femoral shaft parameters, overall the results of bone geometry and CSMI of the femoral shaft were very consistent with the results for the femoral neck; however, cortical vBMD of the femoral shaft decreased significantly in both the ELD and ALF groups. In conclusion, our longitudinal analysis of hip geometry by clinical CT revealed the unexpected potential of ELD to increase cortical CSA, vBMD, and bone mass, and to maintain cortical thickness, probably through the more potent effect of ELD in mitigating endocortical bone resorption than ALF. By improving the biomechanical properties of the proximal femur, ELD may have the potential to reduce the risk of hip fractures.