Bone Architectural Parameters Research Articles

Teriparatide administration is osteoanabolic but does not impact atherosclerotic plaque calcification and progression in a mouse model of menopause

Menopause exacerbates osteoporosis and increases the risk of atherosclerotic plaque rupture, leading to cardiovascular mortality. Osteoporotic women are increasingly treated with teriparatide (TPTD, 1–34 parathyroid hormone), one of the few treatments that stimulate bone formation. Despite the fact that atherosclerotic plaque calcification is a hallmark of plaque development, the impact of TPTD administration on plaque calcification remain unclear. In this context, we sought to determine the effects of TPTD administration on atherosclerosis in ovariectomized (OVX) apolipoprotein E deficient mice (ApoE−/−), as a model of postmenopausal osteoporosis. OVX ApoE−/− mice, fed a high fat, high cholesterol diet to induce atherosclerosis, received either vehicle or TPTD daily injections (40 μg/kg/d) for 4 or 10 weeks, at which points plaques are respectively weakly and heavily calcified. After sacrifice, bone remodeling was evaluated by serum markers and bone histomorphometry. Bone architectural parameters were measured by μCT. Aortic plaques were analyzed histologically, and their calcification with von Kossa staining and the calcium tracer Osteosense. Plaque inflammation and calcification markers were measured by RT-qPCR. Intermittent TPTD increased bone volume in OVX mice, due to a higher stimulation of bone formation relatively to bone resorption. These effects were not accompanied by changes in serum levels of cholesterol, triglycerides, glucose or insulin. TPTD neither significantly affected aortic plaque size, inflammation, and calcification, even if it slightly increased vascular smooth muscle cell transdifferentiation into calcifying cells. In conclusion, TPTD exhibits osteoanabolic effects in OVX ApoE−/− mice, without significantly influencing atherosclerotic plaque progression or calcification in the short term.

AUTOMATIC SEGMENTATION AND BONE ARCHITECTURE ANALYSIS OF SUBCHONDRAL BONE IN THE MURINE PROXIMAL TIBIA: EVALUATION OF AN OPEN-SOURCE PIPELINE

µCT images are commonly analysed to assess changes in bone density and architecture in preclinical murine models. Several platforms provide automated analysis of bone architecture parameters from volumetric regions of interest (ROI). However, segmentation of the regions of subchondral bone to create the volumetric ROIs remains a manual and time-consuming task. This study aimed to develop and evaluate automated pipelines for trabecular bone architecture analysis of mouse proximal tibia subchondral bone.A segmented dataset involving 62 knees (healthy and arthritic) from 10-week male C57BL/6 mice were used to train a U-Net type architecture, with µCT scans (downsampled) input that output segmentation and bone volume density (BV/TV) of the subchondral trabecular bone. Segmentations were upsampled and used in tandem with the original scans (10µ) as input for architecture analysis along with the thresholded trabecular bone. The analysis considered the manually and U-Net segmented ROIs using two available pipelines: the ITKBoneMorphometry library and CTan (SKYSCAN). The analyses included: bone volume (BV), total volume (TV), BV/TV, trabecular number (TbN), trabecular thickness (TbTh), trabecular separation (TbSp), and bone surface density (BSBV).There was good agreement for bone measures between the manual and U-Net pipelines utilizing ITK (R=0.88-0.98) and CTan (R=0.91-0.98). ITK and CTan showed good agreement for BV, TV, BV/TV, TbTh and BSBV (R=0.9-0.98). However, a limited agreement was seen between TbN (R=0.73) and TbSb (R=0.59) due to methodological differences in how spacing is evaluated.This U-Net/ITK pipeline seamlessly automated both segmentation and quantification of the proximal tibia subchondral bone. This automated pipeline allows the analysis of large volumes of data, and its open-source nature may enable the standardization of stereologic analysis of trabecular bone across different research groups.

Changes to bone mineral density, the trabecular bone score and hip structural analysis following parathyroidectomy: a case report

BackgroundReduction in bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) occurs in secondary hyperparathyroidism associated with chronic kidney disease. BMD generally increases following parathyroidectomy, however longitudinal changes to other DXA-derived parameters, the trabecular bone score (TBS) and hip structural analysis (HSA), have not been described. Postoperative calcium requirements and positive calcium balance raise concerns for an increased risk of vascular calcification. This case illustrates the dramatic increase in BMD that can follow parathyroidectomy in a patient on dialysis, and for the first time demonstrates improvements to HSA parameters and to the TBS.Case presentationA 30-year old woman on haemodialysis underwent subtotal parathyroidectomy for secondary hyperparathyroidism. She developed a post-operative ‘hungry bone syndrome’ requiring substantial calcium and calcitriol supplementation. Six months post-parathyroidectomy, BMD increased by 42% at the lumbar spine, 30% at the femoral neck and 25% at the total proximal femur, with increases sustained over the following 18 months. The TBS increased by 8%. HSA showed a 63% increase in femoral neck cortical thickness and 38% reduction in the buckling ratio, consistent with increased femoral neck stability. The abdominal aortic vascular calcification score (0–24) increased from zero 8-years pre-parathyroidectomy to 2/24 at 18-months post-parathyroidectomy.ConclusionBMD losses incurred by secondary hyperparathyroidism recover rapidly after parathyroidectomy, particularly at sites of trabecular bone. Bone architectural parameters, measured as the TBS and by HSA, also improve. Greater BMD gains may be associated with higher post-operative calcium requirements. While bone is the major reservoir for post-parathyroidectomy calcium supplementation, positive calcium balance may contribute to vascular calcification risk.

SIX WEEKS OF TREADMILL RUNNING EXERCISE IMPROVE BONE ARCHITECTURE IN ADULT OSTEOPENIC RATS: AN EXPERIMENTAL STUDY TOWARD EXERCISE DOSE PRESCRIPTION

Question: Can exercise dose be established for bone weakness treatment? Design: Randomized experimental study. Participants: Thirty two adult (12 weeks) Wistar rats (16 males and 16 females) weighed [Formula: see text][Formula: see text]gm. Intervention: Rats were tail suspended for 2 weeks and then randomly divided into four groups; Group I ([Formula: see text]) sacrificed after suspension, Group II ([Formula: see text]) normal cage activities. Group III: ([Formula: see text]) level surface treadmill running. Group IV: ([Formula: see text]) uphill treadmill at angle of 15∘. The running speed was 12[Formula: see text]m/min for a period of 30[Formula: see text]min daily at frequency of 5 days/week for 6 weeks. Outcome measures: Histomorphometric analysis of distal femurs of right hind limbs to measure bone architectural parameters (cortical thickness, Tb.Th, Tb.Nm, Tb.Sp, Tb.Ar, Bone marrow area and density and TBA). Results: Significant improvements were shown in bone architecture in distal femur of Group IV ([Formula: see text]) compared to both Group I and Group II. No significant improvement in distal femur in Group III ([Formula: see text]) compared to both Group I and Group II. The percentage of change was found to be 62–96% between Group IV and Group II and 72– 82% between Group IV and Group I. Conclusion: The results suggested that uphill treadmill running exercises were effective to induce changes in bone tissue in the form of changing trabecular dimensions and density. The induced structural improvement was site specific and dose dependent.

Impact of Bone Volume Upon Condylar Activity in Patients With Unilateral Condylar Hyperplasia

Unilateral condylar hyperplasia or hyperactivity (UCH) is a bone overgrowth disorder affecting the mandible. The purpose of this study was to determine the relations among age, condylar bone structure, condylar bone volume, and condylar bone activity on single-photon emission computed tomographic (SPECT) scans in patients with UCH. This study included 20 patients with a clinical presentation of progressive mandibular asymmetry and a positive bone SPECT scan. A bone SPECT-derived standardized uptake value (bSUV) for the condylar region was determined. All patients underwent condylectomy to arrest further progression of the disease. The resected condyles were scanned with a micro-computed tomographic scanner (18-μm resolution). Bone architectural parameters were calculated with routine morphometric software. The mean bSUV of the condyle on the affected side was 15.32 (standard deviation [SD], 8.98) compared with 9.85 (SD, 4.40) on the nonaffected side (P=.0007). For trabecular bone structure, there was a nonsignificant correlation between the SUV of the affected condyle and the measured bone volume fraction (r=0.13; P=.58) and trabecular thickness (r=0.03; P=.90). No meaningful relation was found between condylar bone volume fraction and condylar activity on bone scan; therefore, the impact of bone volume fraction on the results of bone scans is limited. The measured condylar activity on SPECT scan seems to be primarily a reflection of the remodeling rate of bone.

Wnt10b and Dkk-1 gene therapy differentially influenced trabecular bone architecture, soft tissue integrity, and osteophytosis in a skeletally mature rat model of osteoarthritis

ABSTRACTAims: Our goals in the current experiments were to determine if (a) upregulation of Wnt signaling would induce osteoarthritis changes in stable stifle joints and (b) if downregulation of Wnt signaling in destabilized joints would influence the progression of OA. Methods: At 37 weeks of age, rats were injected in the stifle joint with a recombinant adeno-associated viral vector containing the Wnt-inhibitor Dkk-1 or a Wnt10b transgene. At 40 weeks of age, rats underwent surgical destabilization of the joint. At 50 weeks of age, stifle joints were submitted for micro-computed tomography and histopathological analysis. Results: Injection of either Wnt10b or Dkk-1 transgenes in stable joints improved bone architectural parameters, but worsened soft tissue integrity. Osteophytosis was decreased by Dkk-1, but unchanged by Wnt10b. Destabilization negatively influenced bone architecture, increased osteophytosis, and decreased soft tissue integrity. Dkk-1 exacerbated the negative effects of destabilization, whereas Wnt10b had little effect on these parameters. Osteophytosis was improved, whereas soft tissue integrity was worsened by both transgenes in destabilized joints. Conclusions: The Wnt-inhibitor Dkk-1 does not appear to completely inhibit the effects of Wnt signaling on bone remodeling. In vivo upregulation of Wnt10b and its inhibitor, Dkk-1, can produce both parallel or contrasting phenotypic responses depending on the specific parameter measured and the fidelity of the examined joint. These observations elucidate different roles for Wnt signaling in stable versus destabilized joints and may help to explain the conflicting results previously reported for the role of Dkk-1 in joint disease.

Thymoquinone prevents RANKL-induced osteoclastogenesis activation and osteolysis in an in vivo model of inflammation by suppressing NF-KB and MAPK Signalling

Osteoclasts are multinuclear giant cells responsible for bone resorption in inflammatory bone diseases such as osteoporosis, rheumatoid arthritis and periodontitis. Because of deleterious side effects with currently available drugs the search continues for novel effective and safe therapies. Thymoquinone (TQ), the major bioactive component of Nigella sativa has been investigated for its anti-inflammatory, antioxidant and anticancer activities. However, its effects in osteoclastogenesis have not been reported. In the present study we show for the first time that TQ inhibits nuclear factor-KB ligand (RANKL) induced osteoclastogenesis in RAW 264.7 and primary bone marrow derived macrophages (BMMs) cells. RANKL induced osteoclastogenesis is associated with increased expression of multiple transcription factors via activation of NF-KB, MAPKs signalling and reactive oxygen species (ROS). Mechanistically TQ blocked the RANKL induced NF-KB activation by attenuating the phosphorylation of IkB kinase (IKKα/β). Interestingly, in RAW 264.7 cells TQ inhibited the RANKL induced phosphorylation of MAPKs and mRNA expression of osteoclastic specific genes such as TRAP, DC-STAMP, NFATc1 and c-Fos. In addition, TQ also decreased the RANKL stimulated ROS generation in macropahges (RAW 264.7) and H2O2 induced ROS generation in osteoblasts (MC-3T3-E1). Consistent with in vitro results, TQ inhibited lipopolysaccharide (LPS) induced bone resorption by suppressing the osteoclastogenesis. Indeed, micro-CT analysis showed that bone mineral density (BMD) and bone architecture parameters were positively modulated by TQ. Taken together our data demonstrate that TQ has antiosteoclastogenic effect by inhibiting inflammation induced activation of MAPKs, NF-KB and ROS generation followed by suppressing the gene expression of c-Fos and NFATc1 in osteoclast precursors.

Mechanical stimulation of bone marrow in situ induces bone formation in trabecular explants.

Low magnitude high frequency (LMHF) loading has been shown to have an anabolic effect on trabecular bone in vivo. However, the precise mechanical signal imposed on the bone marrow cells by LMHF loading, which induces a cellular response, remains unclear. This study investigates the influence of LMHF loading, applied using a custom designed bioreactor, on bone adaptation in an explanted trabecular bone model, which isolated the bone and marrow. Bone adaptation was investigated by performing micro CT scans pre and post experimental LMHF loading, using image registration techniques. Computational fluids dynamic models were generated using the pre-experiment scans to characterise the mechanical stimuli imposed by the loading regime prior to adaptation. Results here demonstrate a significant increase in bone formation in the LMHF loaded group compared to static controls and media flow groups. The calculated shear stress in the marrow was between 0.575 and 0.7 Pa, which is within the range of stimuli known to induce osteogenesis by bone marrow mesenchymal stem cells in vitro. Interestingly, a correlation was found between the bone formation balance (bone formation/resorption), trabecular number, trabecular spacing, mineral resorption rate, bone resorption rate and mean shear stresses. The results of this study suggest that the magnitude of the shear stresses generated due to LMHF loading in the explanted bone cores has a contributory role in the formation of trabecular bone and improvement in bone architecture parameters.

Quantitative analysis of bone and soft tissue by micro-computed tomography: applications to ex vivo and in vivo studies.

Micro-computed tomography (micro-CT) is a high-resolution imaging modality that is capable of analysing bone structure with a voxel size on the order of 10 μm. With the development of in vivo micro-CT, where disease progression and treatment can be monitored in a living animal over a period of time, this modality has become a standard tool for preclinical assessment of bone architecture during disease progression and treatment. For meaningful comparison between micro-CT studies, it is essential that the same parameters for data acquisition and analysis methods be used. This protocol outlines the common procedures that are currently used for sample preparation, scanning, reconstruction and analysis in micro-CT studies. Scan and analysis methods for trabecular and cortical bone are covered for the femur, tibia, vertebra and the full neonate body of small rodents. The analysis procedures using the software provided by ScancoMedical and Bruker are discussed, and the routinely used bone architectural parameters are outlined. This protocol also provides a section dedicated to in vivo scanning and analysis, which covers the topics of anaesthesia, radiation dose and image registration. Because of the expanding research using micro-CT to study other skeletal sites, as well as soft tissues, we also provide a review of current techniques to examine the skull and mandible, adipose tissue, vasculature, tumour severity and cartilage. Lists of recommended further reading and literature references are included to provide the reader with more detail on the methods described.

In vivo loss of cement-bone interlock reduces fixation strength in total knee arthroplasties.

Prevention of aseptic loosening of total knee arthroplasties (TKAs) remains a clinical challenge. Understanding how changes in morphology at the implant-bone interface with in vivo service affect implant stability and strength could lead to new approaches to mitigate loosening. Enbloc TKA retrievals and freshly-cemented TKA tibial components were used to determine if the mechanical strength of the interface depended on the amount of cement-bone interlock and the morphology of the supporting bone under the cement layer. Implants were sectioned into small specimens of the cement-interface-bone from under the tibial tray. Micro-CT scans were used to document interlock morphology and architecture of the supporting trabecular bone. Axial compression tests were used to assess mechanical behavior. Postmortem retrievals had lower contact fraction (42 ± 55%) compared to freshly-cemented constructs (121 ± 61%) (p = 0.0008). Supporting bone architecture parameters were not different for the two groups. Increased interface contact fraction and supporting bone volume fraction (BV/TV) were positive predictors of interface strength (r(2) = 0.72, p = 0.0001). For the same supporting bone BV/TV, postmortem specimens had weaker interfaces; they were also more compliant. Cemented TKAs with in vivo service experience a loss of fixation strength and increased micro-motion due to the loss of cement-bone interlock.

The Beneficial Use of Nigella Sativa Powder in the Healing of Different Portions of Extracted Tooth Socket: In Vivo Study

Bac k ground: Nigella sativa is so beneficial due to it’s content of over a hundred components such as aromatic oils, trace elements, vitamins and enzymes. It contains 58% of essential fatty acids including omega 6 and omega 3. These are necessary for the forming of Prostaglandin E1 which balances and strengthens the immune system giving it the power to prevent infections and allergies and control chronic illnesses. Blackseed oil also contains about 0.5 - 1.5% volatile oils including nigellone and thymochinone which are responsible for its anti-histamine, anti-oxidant, anti-infective and broncho-dilating effect. Aim o f the study: To evaluate the effect of Nigella sativa (powder and oil) on the healing process in different portions of rabbit socket by histomorphometric analysis of bone architecture parameters. Mat erials and Methods: The sample of the study consist of twenty rabbits, extract their upper two central incisors under general anesthesia. The left side filled once with Nigella sativa powder and once with Nigella sativa oil material, and the right side left for normal healing as a control group. The two sockets were sutured. The results were studied in intervals period 2 and 6 weeks, histologically and then assayed for histomorphometic analysis for trabecular width, trabecular number and the trabecular separa- tion Marrow space star volume analysis (V*m), Osteoblast, osteocyte, and blood vessels number, in coronal, middle and apical portions of extracted tooth socket. These parameters are derived from microscopic two dimension image measurements analyzer software program. Results: Histomorphometric analysis for variables of trabeculae width (thickness of trabeculae), trabecular separation and cortical thickness in three studied groups for coronal, middle and apical portions of socket showed significant differences in NgS powder and oil groups in comparison to control. Bone marrow star volume showed a significant variation between NgS powder and NgS oil in comparison to control, also bone marrow star volume showed decrease in it’s value with increment in healing period in all groups. Trabecular number and width shows to be higher in NgS powder group in all portions of the socket in comparisum to control and NgS oil groups at 2 and 6 weeks duration. Blood vessels’ number shows to be higher in middle portion in NgS powder group at 2 and 6 weeks duration in comparisum to NgS oil and control groups. Con clusion: Nigella sativa powder suggest to be more effective and enhancer in acceleration of bone formation than oil.

Response to “Vertebral fracture and intervertebral discs”

We thank Drs. Adams and Dolan for their interest in our work and the opportunity to further discuss the association between vertebral bone mineral density (BMD) and disc degeneration (DD) in the lumbar spine. Their comments arise from our discussion of study limitations, in which we acknowledged that ‘‘the age of our subjects was relatively young and a mean age of 50 years is probably too young to determine the full extent of the association studied.’’ We went on to speculate that there may be a stronger association between greater vertebral BMD and more severe DD in older spines, which they question. This was, of course, only speculation, as the association in the elderly could not be addressed with our data and was based on a number of previous studies of elderly women that revealed an association between greater vertebral BMD and more severe lumbar DD. In one such study of 630 women older than 60 years (73.3 6.9 years), higher dual-energy X-ray absorptiometry (DXA) lumbar spine BMD was associated with greater disc space narrowing and Kellgren-Lawrence DD scores. In another study of older women (>60 years, 72.8 6.6 years), greater radiographic disc space narrowing was found to associate with both anterior-posterior and lateral DXA vertebral BMD measurements. An association between greater disc bulging and higher DXA lumbar vertebral BMDwas also observed in women aged up to 86 years. Such associations, however, have been less studied in men, although a similar association between greater disc space narrowing and lumbar BMD acquired with DXA was observed in a cohort of 250 men (65.4 9.0 years). We were not suggesting that the relation between the structure and function of the vertebrae and discs is a simple one. Although our study was not designed to investigate underlying mechanisms of the BMD-DD association we identified, particularly in older spines, it is an important and interesting topic that Adams and Dolan highlight. Adams and Dolan discuss a possible mechanism that could lead to focal bone loss–related specifically to severe disc narrowing, seen in late-stage DD, which may be particularly relevant in the elderly. In pursuing such knowledge, distinguishing different definitions of lumbar vertebral BMD is of great importance. Whereas BMD measured using DXA is areaadjusted, BMD measured with QCT or micro–computed tomography (mCT) is volume-adjusted. The measurements acquired in the study by Adams and colleagues, are substantially different from those used in our study. They used measures of regional bone architecture parameters, such as bone volume/total volume (BV/TV) and trabecular thickness (Tb.Th), to examine focal bone variations, whereas we measured global BMD of the whole vertebra and its vertebral body. Thus, the two studies are not directly comparable. Causal inferences are uncertain and the chicken and egg dilemma remains in cross-sectional studies, including those of the BMD-DD relation. Adams’ and Dolan’s view that ‘‘in middle age, dense vertebral bone may promote disc degeneration’’ is one possible explanation for the association observed between vertebral body BMD and DD, but there are others. We did not suggest and do not agree with the view that vertebral BMD is likely to interfere withmetabolite transport through the vertebral endplate, because we did not observe an association between endplate BMD and DD in a previous study. On the other hand, we agree with Adams and colleagues that severe disc narrowing may shift more mechanical loading posteriorly to the facet joints and thus, stress-shield the anterior vertebral body. As for the measurement of disc degeneration, disc space narrowing was not selected because it is a nonspecific DD indicator and cannot reflect early DD. Furthermore, disc height measurements are prone to bias by osteophytes and endplate sclerosis, which likely are confounders of the BMD-DD association. Therefore, we used discography, which can display ‘‘successive stages in disc degeneration,’’ as a superior measure to disc space narrowing. As we have discussed in detail, although it is possible that DD is influenced by altered mechanical loading due to BMD changes, it is also possible that elevated BMD is an adaption of the vertebral bone to the changing mechanical environment related to DD. Therefore, we agree with Adams’ and Dolan’s view that ‘‘interactions between vertebrae and their adjacent discs cannot be summarized simply.’’ REPLY JBMR

Histomorphometric analysis of bone architecture parameters in socket of rabbit treated with Nigella Sativa

Background: Seeds of Nigella sativa are frequently used in folk medicine in the Middle East and some Asian countries for the promotion of good health and treatment of many ailments. The multiple uses of Nigella sativa in folk medicine encouraged many investigators to isolate the possible active components and to conduct in vivo and in vitro studies on laboratory animals and human beings in order to understand its therapeutic actions. The aim of this study is to evaluate the effect of Nigella Sativa when used as a powder and during oil application on healing process of extracted teeth sockets in different weeks. Materials and Methods: The sample of our study consists of Forty eight rabbits to extract their upper two central incisors under general anesthesia. The left side filled once with Nigella sativa powder and once with Nigella sativa oil material, and the right side left for normal healing as a control group. The two sockets were sutured. The results were studied in intervals period 1, 2, 4, and 6 weeks, histologically and radiographically. Results: Histomorphometric analysis for variables: trabecular width, trabecular number, trabecular separation, Marrow space star volume analysis, Osteoblast number, osteocyte number and blood vessels number for two sockets showed significant differences in NgS powder group in comparison to NgS oil group and both NgS groups in comparison to control. Bone marrow star volume showed a significant variation between NgS powder and NgS oil and in both NgS groups in comparison to control, also bone marrow star volume showed decrease in it’s value with increment in healing period in all groups, Cortical bone thickness records showed increment in NgS powder group in comparison to oil and in both groups in comparison to control with increment in periods of healing, Counting of osteoblast and osteocyte showed high number in both NgS (powder and oil) groups in comparison to control group. The increment in number detected in 2nd week and then decrease as increase in periods (4th and 6th weeks) and numerous blood vessels detected in 4th week’s duration in NgS powder groups in apical portion while it detected in 6th weeks in apical portion for oil group. Conclusion: Nigella sativa (powder or oil) seems to be bioactive materials that enhance differentiation and proliferation of progenitor cells to specialized bone formative cells, with acceleration of bone formation. (J Bagh Coll Dentistry 2012;24(1):45-51).

Trabecular structure analysis using C-arm CT: comparison with MDCT and flat-panel volume CT

This paper assesses interscan, interreader, and intrareader variability of C-arm CT and compares it to that of flat-panel volume-CT (fpVCT) and high-definition multi-detector-CT (HD-MDCT). Five cadaver knee specimens were imaged using C-arm-CT, fpVCT, and HD-MDCT. Apparent (app.) trabecular bone volume fraction (BV/TV), app. trabecular number (TbN), app. trabecular spacing (TbSp), and app. trabecular thickness (TbTh) of the proximal tibia were measured by three readers. Interreader, intrareader, and interscan variability for C-arm CT was expressed as coefficient of variation (CV), standard deviation (SD), and intraclass correlation coefficient (ICC). With the exception of app.TbSp (CV: 7.05-9.35%, SD: 0.06-0.09, ICC: 0.89-0.94), the variability of C-arm CT was low (CV: 2.41-6.43%, SD: 0.01-0.048, ICC: 0.65-0.98). Its interreader reliability (CV: 2.66-4.55%, SD: 0.01-0.03, ICC: 0.81-0.95) was comparable to that of HD-MDCT (CV: 2.41-4.08%, SD: 0.014-0.016, ICC: 0.95-0.96), and fpVCT (CV: 3.13-5.63%, SD: 0.009-0.036, ICC: 0.64-0.98) for all parameters except app.TbSp. C-arm CT is a reliable method for assessing trabecular bone architectural parameters with the exception of app.TbSp due to spatial resolution limitation.

Advances in osteoporosis imaging

In the assessment of osteoporosis, the measurement of bone mineral density (BMD a) obtained from dual energy X-ray absorptiometry (DXA; g/cm 2) is the most widely used parameter. However, bone strength and fracture risk are also influenced by parameters of bone quality such as micro-architecture and tissue properties. This article reviews the radiological techniques currently available for imaging and quantifying bone structure, as well as advanced techniques to image bone quality. With the recent developments in magnetic resonance (MR) techniques, including the availability of clinical 3 T scanners, and advances in computed tomography (CT) technology (e.g. clinical Micro-CT), in-vivo imaging of the trabecular bone architecture is becoming more feasible. Several in-vitro studies have demonstrated that bone architecture, measured by MR or CT, was a BMD-independent determinant of bone strength. In-vivo studies showed that patients with, and without, osteoporotic fractures could better be separated with parameters of bone architecture than with BMD. Parameters of trabecular architecture were more sensitive to treatment effects than BMD. Besides the 3D tomographic techniques, projection radiography has been used in the peripheral skeleton as an additional tool to better predict fracture risk than BMD alone. The quantification of the trabecular architecture included parameters of scale, shape, anisotropy and connectivity. Finite element analyses required highest resolution, but best predicted the biomechanical properties of the bone. MR diffusion and perfusion imaging and MR spectroscopy may provide measures of bone quality beyond trabecular micro-architecture.

The regulation of hypoxia inducible factor-1alpha on osteoblast function in postmenopausal osteoporosis

To study the regulation of hypoxia inducible factor-1alpha (HIF-1alpha) on osteoblast function in postmenopausal osteoporosis. From October 2004 to May 2006, Cre-Loxp recombinase was used to create mice which the HIF-1alpha gene in osteoblasts was conditional knock-out, 24 female wild-type (WT) mice and 24 female conditional knock-out (CKO) mice of 3 months old were operated on ovariotomy. At 0,4,8 weeks after operation, bone histomorphometry parameters were measured with computer image analysis in HE stain sections and in tetracycline bone double labeling fluorescence sections; Bone density and the trabecular bone architecture parameters were measured by Micro-CT; The mRNA expression of vascular endothelial growth factors (VEGF), RunX2, OC, ALP were detected with quantitative RT-PCR; The protein expression of VEGF and RunX2 were detected with Western-blotting. In CKO mice, the trabecular number, volume, thickness, bone density, mineral apposition rate (MAR), the expression of VEGF, RunX2, OC, ALP on mRNA level and the expression of VEGF, RunX2 on protein level decreased significantly compared with WT mice especially in 8 weeks after operation. The bone formation ability of osteoblasts in CKO mice was reduced compared with WT mice after ovariotomy. HIF-1alpha can regulate the bone formation ability of osteoblasts in postmenopausal osteoporosis.

Regional variation in vertebral bone morphology and its contribution to vertebral fracture strength

Vertebral fractures may result in pain, loss of height, spinal instability, kyphotic deformity and ultimately increased morbidity. Fracture risk can be estimated by vertebral bone mineral density (BMD). However, vertebral fractures may be better defined by more selective methods that account for micro-architecture. Our aim was to quantify regional variations in bone architecture parameters (BAPs) and to assess the degree with which regional variations in BAPs affect vertebral fracture strength. The influence of disc health and endplate thickness on fracture strength was also determined. The soft tissue and posterior elements of 20 human functional spine units (FSU) were removed (T9 to L5, mean 74.45 ± 4.25 years). After micro-CT scanning of the entire FSU, the strength of the specimens was determined using a materials testing system. Specimens were loaded in compression to failure. BAPs were assessed for 10 regions of the vertebral cancellous bone. Disc health (glycosaminoglycan content of the nucleus pulposus) was determined using the degree of binding with Alcian Blue. Vertebrae were not morphologically homogeneous. Posterior regions of the vertebrae had greater bone volume, more connections, reduced trabecular separation and more plate-like isotropic structures than their corresponding anterior regions. Significant heterogeneity also exists between posterior superior and inferior regions (BV/TV: posterior superior 12.6 ± 2.8%, inferior 14.6 ± 3%; anterior superior 10.5 ± 2.2%, inferior 10.7 ± 2.4%). Of the two endplates that abutted a common disc, the cranial inferior endplate was thicker (0.44 ± 0.15 mm) than the caudal superior endplate (0.37 ± 0.13 mm). Our study found good correlations between BV/TV, connective density and yield strength. Fracture risk prediction, using BV/TV multiplied by the cross sectional area of the endplate, can be improved through regional analysis of the underlying cancellous bone of the endplate of interest ( R 2 0.78) rather than analysis of the entire vertebra ( R 2 0.65) or BMD ( R 2 0.47). Degenerated discs lack a defined nucleus. A negative linear relationship between disc health and vertebral strength ( R 2 0.70) was observed, likely due to a shift in loading from the weaker anterior vertebral region to the stronger posterior region and cortical shell. Our results show the importance of considering regional variations in cancellous BAPs and disc health when assessing fracture risk.

High-dose bisphoshonate therapy in an urgent case of spontaneous multiple vertebral fractures in a 55 year old woman

An early postmenopausal Caucasian woman aged 55 sustained multiple vertebral fractures after a minor trauma. After exclusion of any kind of secondary osteoporosis, we administered due to clinical severity combined oral and cyclic intravenous bisphosphonate therapy (oral risedronate 35 mg/week, i.v. pamidronate 30 mg quarterly) with adequate calcium and vitamin D supplementation for 28 months. We performed a transiliac bone biopsy at baseline and at month 28. The paired samples were investigated by histomorphometry, by microCT-analysis for 3d structure and by qBEI representing bone mineral density distribution. Mineralisation of the bone matrix was not influenced by supplementation of calcium and vitamin D. Parameters of bone architecture and BMD improved; and a reduction of pain and increased mobility was observed. No further osteoporotic fractures occurred during the time of investigation.

Similar effects of long-term exogenous growth hormone (GH) on bone and muscle parameters: A pQCT study of GH-deficient and small-for-gestational-age (SGA) children

Background and aims Treatment with GH in short children has focused on height development. Little is known about the concomitant changes in muscle mass, bone structure and bone strength. Methods Muscle area as well as parameters of bone architecture (bone mineral content, BMC; volumetric cortical density, total bone area, TBA; cortical area, cortical thickness, CT; and marrow area) were measured by means of pQCT (Stratec) at 65% of the proximal length of the forearm. The strength–strain index (SSI) was calculated as an indicator of bone strength. Results Prepubertal children with GHD (mean values: age; 7.2 years; height SDS = − 2.9 SDS; GH dose: 30 μg/kg/d) were followed at 0, 6, 12 ( n = 74) and 24 ( n = 55) months. Prepubertal children with SGA (mean values: age: 7.1 years; height SDS = − 3.4 SDS; GH dose: 55 μg/kg/d) were followed at 0, 6, 12 ( n = 47) and 24 ( n = 35) months. Both groups showed a similar increase in height. At GH start, muscle mass and bone characteristics were lower than normal but similar in SGA vs. GHD. Muscle area (mean values, SDS) increased from − 3.0 to − 1.5 in SGA and from − 2.4 to − 1.0 in GHD. Bone geometry changed in a biphasic mode, with an increase in total bone area and lowering of bone mineral content (BMC) during the first 12 months, followed by an increase of BMC and CT thereafter. SSI (mean values, mm 3) improved from 78 to 114 in GHD and from 62 to 101 in SGA after 24 months on GH. The increment in terms of SDS did not reach significance in SGA. SSI correlated positively with muscle area before and during GH treatment. Conclusions Bone strength and muscle mass are impaired in prepubertal children with GHD and SGA. Exogenous GH can indirectly improve bone structure and strength by inducing an increase in muscle mass. Our findings support the assumption that, in SGA, there is impaired tissue responsiveness to GH.

Accuracy of 3D MR microscopy for trabecular bone assessment: a comparative study on calcaneus samples using 3D synchrotron radiation microtomography

Magnetic resonance (MR) imaging is attractive for a noninvasive and radiation-free assessment of in vivo trabecular bone architecture. However the quantitative evaluation of architectural parameters could be biased by the limited sensitivity of MR. The aim of this study was to determine the accuracy of trabecular bone architectural parameters obtained from 3D high-resolution MR images, by comparison to reference images obtained by high-resolution X-ray microtomography using synchrotron radiation, from 29 samples of human calcaneus. MR images were obtained with a 66 microm x 66 microm x 66 microm voxel size, using a 8.5 T MR microscope. Microtomography images were acquired with a 10 microm x 10 microm x 10 mum voxel size, from the same samples. 3D architectural parameters characterizing the morphometry, topology, anisotropy, and orientation were computed from both modalities and carefully compared. To avoid errors, an identical region of interest was selected in the two corresponding images, and the same algorithms were run at identical spatial resolution. Our results establish that network connectivity, orientation and anisotropy are reliable from the MR data. The bone volume fraction, and morphometric parameters measured from the MR data, were found to be biased with respect to their values from the microtomography data, although there was a significant correlation between the two modalities.