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The femoral head is one of the most commonly used bones for allografts and biomechanical studies. However, there are few reports on the trabecular bone microarchitectural parameters of freshly harvested trabecular bones. To our knowledge, this is the first study to characterize the microstructure of femoral heads tested immediately after surgery and compare it with the microstructure obtained with conventional freezing. This study aims to investigate whether freezing at -80 °C for 6 weeks affects the trabecular microstructure of freshly harvested bone tissue. This study was divided into two groups: one with freshly harvested human femoral heads and the other with the same human femoral heads frozen at -80 °C for 6 weeks. Each femoral head was scanned using an X-ray microcomputed tomography scanner (µCT) to obtain the microarchitectural parameters, including the bone volume fraction (BV/TV), the mean trabecular thickness (Tb.th), the trabecular separation (Tb.sp), the degree of anisotropy (DA), and the connectivity density (Conn.D). There was no statistically significant difference between the fresh and the frozen groups for any of the parameters measured. This study shows that freezing at -80 °C for 6 weeks does not alter bone microstructure compared with freshly harvested femoral heads tested immediately after surgery.
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The Achilles tendon enthesis (ATE) anchors the Achilles tendon into the calcaneus through fibrocartilaginous tissue. The latter is enriched in type II collagen and proteoglycans (PGs), both of which give the enthesis its capacity to withstand compressive stress. Because unloading and reloading induce remodeling of the ATE fibrocartilage (Camy et al., 2022), chronic changes in the mechanical load could modify the mechanical response under compressive stress. Therefore, we investigated the ATE fatigue behavior in mice, under cyclic compressive loading, after 14 days of hindlimb suspension and 6 days of reloading. In addition, we performed a qualitative histological study of PGs in ATE fibrocartilage. The mechanical behavior of ATE was impaired in unloaded mice. A significant loss of 27 % in Δd (difference between the maximum and minimum displacements) was observed at the end of the test. In addition, the hysteresis area decreased by approximately 27 % and the stiffness increased by over 45 %. The increased stiffness and loss of viscosity were thrice and almost twice those of the control, respectively. In the reloaded entheses, where the loss of Δd was not significant, we found a significant 28 % decrease in the hysteresis area and a 26 % increase in stiffness, both of which were higher regarding the control condition. These load-dependent changes in the mechanical response seem partly related to changes in PGs in the uncalficied part of the ATE. These findings highlight the importance of managing compressive loading on ATE when performing prophylactic and rehabilitation exercises.
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Tendão do Calcâneo , Elevação dos Membros Posteriores , Tendão do Calcâneo/fisiologia , Animais , Camundongos , Elevação dos Membros Posteriores/fisiologia , Suporte de Carga/fisiologia , Estresse Mecânico , Fenômenos Biomecânicos , Masculino , Força Compressiva/fisiologia , Proteoglicanas/metabolismo , Camundongos Endogâmicos C57BL , Fibrocartilagem/fisiologia , Fibrocartilagem/fisiopatologiaRESUMO
PURPOSE: Although tendon lacerations are common, there is currently no consensus on choice of suture. Easy and fast sutures that impart enough strength to allow mobilization are needed. This study compared the ex vivo biomechanical strength (force required to create a 2 mm tendon gap) of a novel suture (ST-knot) with that of a conventional suture (double Kessler). MATERIALS AND METHODS: Forty fresh deep flexor tendons from porcine forelimbs were used. Both repaired tendon ends were mounted on standard traction jaws of an axial traction machine at an initial distance of 40 mm for all tendons. A high-definition camera was used to determine the force forming a 2 mm gap. Ten tendons in group 1 (ST-knot) and 10 in group 2 (double Kessler) were prepared with PDS 4.0 (single thread for Kessler, double thread for ST-knot). Tendons in groups 3 (ST-knot) and 4 (double Kessler) were repaired with PDS 1.0 using the same principle. RESULTS: There was no significant difference in the force required to form a 2 mm tendon gap between groups 1 and 2, and this trend was identical when using a stronger thread in groups 3 and 4. The maximum force before rupture, mode of repair failure, stress and stiffness were also comparable, with no significant differences between groups 1 and 2, or between groups 3 and 4. CONCLUSIONS: The ST-knot showed comparable results to the double-Kessler knot, whichever the thread used. Because it involves fewer steps than conventional techniques and is easy to perform, the ST-knot may offer a therapeutic solution, particularly in complex trauma with multiple tendon injury.
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Técnicas de Sutura , Traumatismos dos Tendões , Resistência à Tração , Animais , Suínos , Fenômenos Biomecânicos , Traumatismos dos Tendões/cirurgia , Traumatismos dos Tendões/fisiopatologia , Suturas , Tendões/cirurgiaRESUMO
PURPOSE: It was hypothesized that using a Patient-Specific Cutting Guide (PSCG) would allow the creation of sawbones model osteotomies, identical in the 3 planes and the hinge parameters, that can be used for biomechanical studies. The aim of the study was to evaluate the accuracy of the PSCG system and to introduce and assess the new hinge parameter; the hinge area. METHODS: Six identical sawbones tibia models were identically set up for identical osteotomy cuts by the same surgeon in the same session and with identical instruments. A medical scanner was used to evaluate the 3D configuration of all the specimens. The analyzed parameters included the cutting angles in both the coronal and sagittal planes (degrees) and the hinge and the slicing areas (cm2), and the hinge thickness (mm). The values were statistically evaluated for average, standard deviation, 95% confidence index, and delta to the expected values were calculated. RESULTS: The mean values for the coronal and sagittal angles were 110.5̱1Ì and 89.8̱0.8Ì, respectively. The 95% confidence index level ranged between 0.1Ì, and 0.8Ì in both the coronal & the sagittal planes. The mean values for the hinge thickness, the hinge area, and the slicing area were 12.7±1.5mm, 4.2±0.9 cm2, and 18.3±1.2 cm2, respectively. CONCLUSION: In the presented study, it can be demonstrated that mechanically identical osteotomy specimens, with regard to the cutting planes and hinge parameters, can be reliably created using the PSCG. The identical specimens can be used for biomechanical research purposes to further expand our knowledge of the factors affecting osteotomy outcomes. LEVEL OF EVIDENCE: IV.
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The fibrocartilaginous tendon enthesis, i.e. the site where a tendon is attached to bone through a fibrocartilaginous tissue, is considered as a functionally graded interface. However, at local scale, a very limited number of studies have characterized micromechanical properties of this transitional tissue. The first goal of this work was to characterize the micromechanical properties of the mineralized part of the healthy Achilles tendon enthesis (ATE) through microindentation testing and to assess the degree of mineralization and of carbonation of mineral crystals by Raman spectroscopy. Since little is known about enthesis biological plasticity, our second objective was to examine the effects of unloading and reloading, using a mouse hindlimb-unloading model, on both the micromechanical properties and the mineral phase of the ATE. Elastic modulus, hardness, degree of mineralization, and degree of carbonation were assessed after 14 days of hindlimb suspension and again after a subsequent 6 days of reloading. The elastic modulus gradually increased along the mineralized part of the ATE from the tidemark to the subchondral bone, with the same trend being found for hardness. Whereas the degree of carbonation did not differ according to zone of measurement, the degree of mineralization increased by >70 % from tidemark to subchondral bone. Thus, the gradient in micromechanical properties is in part explained by a mineralization gradient. A 14-day unloading period did not appear to affect the gradient of micromechanical properties of the ATE, nor the degree of mineralization or carbonation. However, contrary to a short period of unloading, early return to normal mechanical load reduced the micromechanical properties gradient, regardless of carbonate-to-phosphate ratios, likely due to the more homogeneous degree of mineralization. These findings provide valuable data not only for tissue bioengineering, but also for musculoskeletal clinical studies and microgravity studies focusing on long-term space travel by astronauts.
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Resorbable hydrogels are widely used as scaffolds for tissue engineering. These hydrogels can be modified by grafting dendrimer-linked functionalized molecules (dendrigrafts). Our aim was to develop a tunable poly(L-lysine) dendrigrafts (DGL)/PEG-based hydrogel with an inverse porosity and to investigate its osteogenic potential. DGL/PEG hydrogels were emulsified in a surfactant-containing oil solution to form microspheres. The toxicity was evaluated on Human Vascular Endothelial Cells (HUVECs) and Bone Marrow Mesenchymal Stem Cells (hMSCs) with Live/Dead and MTT assays. The effects on HUVECs were investigated through C5 Complement expression by RT-PCR and C5a/TGF-ß1 secretion by ELISA. Recruitment of hMSCs was investigated using Boyden chambers and their osteogenic differentiation was studied by measuring Alkaline Phosphatase activity (ALP) and BMP-2 secretion by ELISA. Adjusting the stirring speed during the emulsification allowed to obtain spherical microspheres with tunable diameters (10-1600 µm). The cell viability rate with the hydrogel was 95 and 100% with HUVECs and hMSCs, respectively. Incubating HUVECs with the biomaterial induced a 5-fold increase in TGF-ß1 and a 3-fold increase in Complement C5a release. Furthermore, HUVEC supernatants obtained after incubation with the hydrogel induced a 2.5-fold increase in hMSC recruitment. The hydrogel induced a 3-fold increase both in hMSC ALP activity and BMP-2 secretion. Overall, the functionalized hydrogel enhanced the osteogenic potential by interacting with endothelial cells and hMSCs and represents a promising tool for bone tissue engineering.
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PURPOSE: The Pivot Shift (PS) test is a complex clinical sign that assesses the internal rotation and anterior tibial translation, which occurs abnormally in ACL deficient-knees. Because of the high inter-observer variability, different devices have been designed to characterize this complex movement in quantitative variables. The objective of this pilot study is to validate the reproducibility of intraoperative quantitative assessment of the PS with a smartphone accelerometer. METHODS: Twelve ACL-injured knees were included and compared with the contralateral uninjured side. The PS was measured by two independent observers utilizing a smartphone accelerometer and graded according to the IKDC classification. Measurements were taken preoperatively, intraoperatively and postoperatively. Intraoperative readings were taken during each stage of reconstruction or repair of meniscoligamentous lesions including meniscal lesions, ramp lesions, ACL reconstruction and lateral tenodesis. Reproducibility of the measurements were evaluated according to an intraclass correlation coefficient (ICC). RESULTS: The intra-observer reliability was good for the first examiner and excellent for the second examiner, with the ICC 0.89 [0.67, 0.98] p < 0,001 and ICC 0.97 [0.91, 1.0] p < 0,001 respectively. The inter-observer reliability was excellent between the two observers with the ICC 0.99 [0.97, 1.0] p < 0,001. The mean tibial acceleration measured 3.45 m.s2 (SD = 1.71) preoperatively on the injured knees and 1.03 m.s2 (SD = 0.36) on the healthy knees, demonstrating a significant difference following univariate analysis p < 0.001. Postoperatively, no significant difference was observed between healthy and reconstructed knees The magnitudes of tibial acceleration values were correlated with the PS IKDC grade. CONCLUSION: The smartphone accelerometer is a reproducible device to quantitatively assess the internal rotation and anterior tibial translation during ACL reconstruction surgery. The measurements are influenced by the different surgical steps. Other larger cohort studies are needed to evaluate the specific impact of each step of the ACL reconstruction and meniscal repair on this measurement. An external validation using other technologies are needed to validate the reliability of this device to assess the PS test. LEVEL OF EVIDENCE: Level IV, case series, pilot study.
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PURPOSE: To compare the mechanical stress applied to our grafted defect area according to the diameter of the plugs used in the treatment of osteochondral lesion with osteochondral autograft transplantation (OAT) procedure. METHODS: A biomechanical study was conducted on eight cadaveric knees. A 20-mm defect was created in the weight-bearing zone on the medial femoral condyle then filled either with three plugs of 8 mm, or with four plugs of 6 mm, or with 6 plugs of 4 mm diameter. After the preparation of the specimens, each knee was installed on a mechanical test bench (Instron 5566A). A continuous axial compression of 700 N at 10 mm.min-1 was exerted on the joint. A K-scan 4000-type pressure sheet was used to record the contact area (mm2), the mean pressure (MPa), and the maximum pressure (MPa) on the area of interest. RESULTS: The differences found between the conditions were not statistically significant but showed tendencies. Filling the defect with six plugs of 4 mm restores a larger contact surface compared with the other plugs. The use of 8- and 6-mm grafts lead to a respective increase of 12% and 52% of the mean pressure compared with the 4 mm grafts. This difference was also found for the maximum pressure (36% and 129%). Regardless of the diameter of the plugs used, filling the lesion reduces the mean pressure exerted on the healthy cartilage by 19%. DISCUSSION: A trend emerged towards a better restoration of the cartilage surface and a more harmonious distribution of the pressures exerted in favour of the grafts of smaller diameter. A larger study is needed to obtain a statistically significant result.
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Cartilagem Articular , Cartilagem , Humanos , Autoenxertos , Cartilagem/transplante , Articulação do Joelho/cirurgia , Transplante Autólogo , Joelho , Cartilagem Articular/cirurgiaRESUMO
PURPOSE: To investigate the potential of texture parameters from opportunistic MRI and CT for the detection of patients with vertebral fragility fracture, to design a decision tree and to compute a Random Forest analysis for the prediction of fracture risk. METHODS: One hundred and eighty vertebrae of sixty patients with at least one (30) or without (30) a fragility fracture were retrospectively assessed. Patients had a DXA, an MRI and a CT scan from the three first lumbar vertebrae. Vertebrae texture analysis was performed in routine abdominal or lumbar CT and lumbar MRI using 1st and 2nd order texture parameters. Hounsfield Unit Bone density (HU BD) was also measured on CT-scan images. RESULTS: Twelve texture parameters, Z-score and HU BD were significantly different between the two groups whereas T score and BMD were not. The inter observer reproducibility was good to excellent. Decision tree showed that age and HU BD were the most relevant factors to predict the fracture risk with a 93 % sensitivity and 56 % specificity. AUC was 0.91 in MRI and 0.92 in CT-scan using the Random Forest analysis. The corresponding sensitivity and specificity were 72 % and 93 % in MRI and 83 and 89 % in CT. CONCLUSIONS: This study is the first to compare texture indices computed from opportunistic CT and MR images. Age and HU-BD together with selected texture parameters could be used to assess risk fracture. Machine learning algorithm can detect fracture risk in opportunistic CT and MR imaging and might be of high interest for the diagnosis of osteoporosis.
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Fraturas por Osteoporose , Fraturas da Coluna Vertebral , Humanos , Fraturas da Coluna Vertebral/diagnóstico por imagem , Estudos Retrospectivos , Osso Esponjoso , Reprodutibilidade dos Testes , Absorciometria de Fóton/métodos , Programas de Rastreamento/métodos , Fraturas por Osteoporose/diagnóstico por imagem , Densidade Óssea , Tomografia Computadorizada por Raios X/métodos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/lesõesRESUMO
A lot of evidence has shown the importance of stimulating cell mechanically during bone repair. In this study, we modeled the challenging fracture healing of a large bone defect in tibial diaphysis. To fill the fracture gap, we considered the implantation of a porous osteoconductive biomaterial made of poly-lactic acid wrapped by a hydrogel membrane mimicking osteogenic properties of the periosteum. We identified the optimal loading case that best promotes the formation and differentiation into bone tissue. Our results support the idea that a patient's rehabilitation program should be adapted to reproduce optimal mechanical stimulations.
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Regeneração Óssea , Osteogênese , Humanos , Regeneração Óssea/fisiologia , Consolidação da Fratura/fisiologia , Periósteo , Simulação por ComputadorRESUMO
PURPOSE: Flexor tendon injury continues to pose a number of challenges for hand surgeons. Improving mechanical properties of repairs should allow for earlier and unprotected rehabilitation. A 3-dimensional (3D) 4-strand suture technique has been proposed to combine high tensile strength and low gliding resistance without causing suture pullout due to tendon delamination. Our hypothesis is that the 3D technique can result in better mechanical properties than the Adelaide technique. METHODS: Four groups of 10 porcine flexor tendons were sutured using the 3D or Adelaide technique with a 3-0 polypropylene or ultrahigh molecular weight polyethylene (UHMWPE) suture. The axial traction test to failure was performed on each tendon to measure 2-mm gap force and ultimate tensile strength. RESULTS: The mean 2-mm gap force was 49 N for group A (3D + polypropylene), 145 N for group B (3D + UHMWPE), 47 N for group C (Adelaide + polypropylene), and 80 N for group D (Adelaide + UHMWPE). Failure mode was caused by suture breakage for group A (10/10) and mainly by suture pullout for the other groups (8/10 up to 10/10). With the UHMWPE suture, the mean ultimate tensile strength was 145 N for the 3D technique and 80 N for the Adelaide technique. CONCLUSIONS: Porcine flexor tendons repaired using the 3D technique and UHMWPE suture exceeded a 2-mm gap force and tensile strength of 140 N. The ultimate tensile strength was superior to that of the Adelaide technique, regardless of the suture material. CLINICAL RELEVANCE: This in vitro study on porcine flexor tendon suture highlights that the mechanical properties of 3D repair are better than those of 3D repair using the Adelaide technique when a UHMWPE suture is used.
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Polipropilenos , Tendões , Suínos , Animais , Fenômenos Biomecânicos , Tendões/cirurgia , Resistência à Tração , Técnicas de Sutura , SuturasRESUMO
The current definition of osteoporosis includes alteration of bone quality. The assessment of bone quality is improved by the development of new texture analysis softwares. Our objectives were to assess if proximal femoral trabecular bone texture measured in Ultra high field (UHF) 7 Tesla MRI and CT scan were related to biomechanical parameters, and if the combination of texture parameters and areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry provided a better prediction of femoral failure than aBMD alone. The aBMD of 16 proximal femur ends from eight cadavers were investigated. Nineteen textural parameters were computed in three regions or volumes of interest for each specimen on UHF MRI and CT scan. Then, the corresponding failure load and failure stress were calculated thanks to mechanical compression test. aBMD was not correlated to failure load (R2 = 0.206) and stress (R2 = 0.153). The failure load was significantly correlated with ten parameters in the greater trochanter using UHF MRI, and with one parameter in the neck and the greater trochanter using CT scan. Eight parameters in the greater trochanter using UHF MRI combined with aBMD improved the failure load prediction, and seven parameters improved the failure stress prediction. Our results suggest that textural parameters provide additional information on the fracture risk of the proximal femur when aBMD is not contributive.
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Although multiple structural, mechanical, and molecular factors are definitely involved in osteoporosis, the assessment of subregional bone mineral density remains the most commonly used diagnostic index. In this study, we characterized bone quality in the femoral neck of one osteoporotic patients as compared to an age-matched control subject, and so used a multiscale and multimodal approach including X-ray computed microtomography at different spatial resolutions (pixel size: 51.0, 4.95 and 0.9 µm), microindentation and Fourier transform infrared spectroscopy. Our results showed abnormalities in the osteocytes lacunae volume (358.08 ± 165.00 for the osteoporotic sample vs. 287.10 ± 160.00 for the control), whereas a statistical difference was found neither for shape nor for density. The osteoporotic femoral head and great trochanter reported reduced elastic modulus (Es) and hardness (H) compared to the control reference (−48% (p < 0.0001) and −34% (p < 0.0001), respectively for Es and H in the femoral head and −29% (p < 0.01) and −22% (p < 0.05), respectively for Es and H in the great trochanter), whereas the corresponding values in the femoral neck were in the same range. The spectral analysis could distinguish neither subregional differences in the osteoporotic sample nor between the osteoporotic and healthy samples. Although, infrared spectroscopic measurements were comparable among subregions, and so regardless of the bone osteoporotic status, the trabecular mechanical properties were comparable only in the femoral neck. These results illustrate that bone remodeling in osteoporosis is a non-uniform process with different rates in different bone anatomical regions, hence showing the interest of a clear analysis of the bone microarchitecture in the case of patients' osteoporotic evaluation.
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While muscle and bone adaptations to deconditioning have been widely described, few studies have focused on the tendon enthesis. Our study examined the effects of mechanical loading on the structure and mechanical properties of the Achilles tendon enthesis. We assessed the fibrocartilage surface area, the organization of collagen, the expression of collagen II, the presence of osteoclasts, and the tensile properties of the mouse enthesis both after 14 days of hindlimb suspension (HU) and after a subsequent 6 days of reloading. Although soleus atrophy was severe after HU, calcified fibrocartilage (CFc) was a little affected. In contrast, we observed a decrease in non-calcified fibrocartilage (UFc) surface area, collagen fiber disorganization, modification of morphological characteristics of the fibrocartilage cells, and altered collagen II distribution. Compared to the control group, restoring normal loads increased both UFc surface area and expression of collagen II, and led to a crimp pattern in collagen. Reloading induced an increase in CFc surface area, probably due to the mineralization front advancing toward the tendon. Functionally, unloading resulted in decreased enthesis stiffness and a shift in site of failure from the osteochondral interface to the bone, whereas 6 days of reloading restored the original elastic properties and site of failure. In the context of spaceflight, our results suggest that care must be taken when performing countermeasure exercises both during missions and during the return to Earth.
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Tendão do Calcâneo , Elevação dos Membros Posteriores , Tendão do Calcâneo/metabolismo , Animais , Osso e Ossos , Colágeno/metabolismo , Camundongos , Músculo Esquelético/metabolismoRESUMO
Distraction osteogenesis (DO) involves several processes to form an organized distracted callus. While bone regeneration during DO has been widely described, no study has yet focused on the evolution profile of mechanical properties of mineralized tissues in the distracted callus. The aim of this study was therefore to measure the elastic modulus and hardness of calcified cartilage and trabecular and cortical bone within the distracted callus during the consolidation phase. We used a microindentation assay to measure the mechanical properties of periosteal and endosteal calluses; each was subdivided into two regions. Histological sections were used to localize the tissues. The results revealed that the mechanical properties of calcified cartilage did not evolve over time. However, trabecular bone showed temporal variation. For elastic modulus, in three out of four regions, a similar evolution profile was observed with an increase and decrease over time. Concerning hardness, this evolves differently depending on the location in the distracted callus. We also observed spatial changes in between regions. A first duality was apparent between regions close to the native cortices and the central area, while latter differences were seen between periosteal and endosteal calluses. Data showed a heterogeneity of mechanical properties in the distracted callus with a specific mineralization profile.
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A better understanding of the mechanical behaviour of child bone is essential to improve the diagnosis of pediatric bone disorders that may influence bone development. Even though the process of bone growth is well described, there are still lacks of knowledge on intrinsic material properties of child bone and particularly on child bone considered as "non-pathological". Geometry, material properties, microstructure and biochemical components are associated with child bone fragility and remain difficult to assess for two main reasons: the scarcity of the bone samples and their small dimensions. In this context, ultrasonic methods offer interesting possibilities by exploiting in particular their non-destructive character. In this chapter, the elasticity properties of Non Pathological Child Cortical Bone (NPCCB) obtained by ultrasonic methods are presented. The objective was to contribute to the construction of a reference database on NPCCB that would serve as a point of comparison for analyzing the effect of a pathology or treatment. After the presentation of the hypotheses on the elasticity and anisotropy of NPCCB, ultrasonic transmission-mode and resonance spectroscopy methods are described. Results are presented and discussed with respect to microstructural and biochemical properties.
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Osso e Ossos , Osso Cortical , Anisotropia , Desenvolvimento Ósseo , Osso e Ossos/diagnóstico por imagem , Criança , Osso Cortical/diagnóstico por imagem , Elasticidade , HumanosRESUMO
MRI could be applied for bone microarchitecture assessment; however, this technique is still suffering from low resolution compared to the trabecular dimension. A clear comparative analysis between MRI and X-ray microcomputed tomography (µCT) regarding microarchitecture metrics is still lacking. In this study, we performed a comparative analysis between µCT and 7T MRI with the aim of assessing the image resolution effect on the accuracy of microarchitecture metrics. We also addressed the issue of air bubble artifacts in cadaveric bones. Three fresh cadaveric femur heads were scanned using 7T MRI and µCT at high resolution (0.051 mm). Samples were submitted to a vacuum procedure combined with vibration to reduce the volume of air bubbles. Trabecular interconnectivity, a new metric, and conventional histomorphometric parameters were quantified using MR images and compared to those derived from µCT at full resolution and downsized resolutions (0.102 and 0.153 mm). Correlations between bone morphology and mineral density (BMD) were evaluated. Air bubbles were reduced by 99.8% in 30 min, leaving partial volume effects as the only source of bias. Morphological parameters quantified with 7T MRI were not statistically different (p > 0.01) to those computed from µCT images, with error up to 8% for both bone volume fraction and trabecular spacing. No linear correlation was found between BMD and all morphological parameters except trabecular interconnectivity (R2 = 0.69 for 7T MRI-BMD). These results strongly suggest that 7T MRI could be of interest for in vivo bone microarchitecture assessment, providing additional information about bone health and quality.
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Trabecular bone could be assessed non-invasively using MRI. However, MRI does not yet provide resolutions lower than trabecular thickness and a comparative analysis between different MRI sequences at different field strengths and X-ray microtomography (µCT) is still missing. In this study, we compared bone microstructure parameters and bone mineral density (BMD) computed using various MRI approaches, i.e., turbo spin echo (TSE) and gradient recalled echo (GRE) images used at different magnetic fields, i.e., 7T and 3T. The corresponding parameters computed from µCT images and BMD derived from dual-energy X-ray absorptiometry (DXA) were used as the ground truth. The correlation between morphological parameters, BMD and fracture load assessed by mechanical compression tests was evaluated. Histomorphometric parameters showed a good agreement between 7T TSE and µCT, with 8% error for trabecular thickness with no significative statistical difference and a good intraclass correlation coefficient (ICC > 0.5) for all the extrapolated parameters. No correlation was found between DXA-BMD and all morphological parameters, except for trabecular interconnectivity (R2 > 0.69). Good correlation (p-value < 0.05) was found between failure load and trabecular interconnectivity (R2 > 0.79). These results suggest that MRI could be of interest for bone microstructure assessment. Moreover, the combination of morphological parameters and BMD could provide a more comprehensive view of bone quality.
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Granulocyte colony-stimulating factor (G-CSF) was shown to promote bone regeneration and mobilization of vascular and osteogenic progenitor cells. In this study, we investigated the effects of a systemic low dose of G-CSF on both bone consolidation and mobilization of hematopoietic stem/progenitor cells (HSPCs), endothelial progenitor cells (EPCs) and mesenchymal stromal cells (MSCs) in a rat model of distraction osteogenesis (DO). Neovascularization and mineralization were longitudinally monitored using positron emission tomography and planar scintigraphy. Histological analysis was performed and the number of circulating HSPCs, EPCs and MSCs was studied by flow cytometry. Contrary to control group, in the early phase of consolidation, a bony bridge with lower osteoclast activity and a trend of an increase in osteoblast activity were observed in the distracted callus in the G-CSF group, whereas, at the late phase of consolidation, a significantly lower neovascularization was observed. While no difference was observed in the number of circulating EPCs between control and G-CSF groups, the number of MSCs was significantly lower at the end of the latency phase and that of HSPCs was significantly higher 4 days after the bone lengthening. Our results indicate that G-CSF accelerates bone regeneration and modulates mobilization of progenitor cells during DO.
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Regeneração Óssea/efeitos dos fármacos , Fator Estimulador de Colônias de Granulócitos/administração & dosagem , Osteogênese por Distração , Células-Tronco/citologia , Animais , Modelos Animais de Doenças , Durapatita/química , Citometria de Fluxo , Mobilização de Células-Tronco Hematopoéticas , Cinética , Masculino , Células-Tronco Mesenquimais/citologia , Neovascularização Fisiológica/efeitos dos fármacos , Osteoblastos/metabolismo , Osteoclastos/efeitos dos fármacos , Tomografia por Emissão de Pósitrons , Ratos , Ratos Sprague-Dawley , Tomografia Computadorizada com Tomografia Computadorizada de Emissão de Fóton Único , Células-Tronco/metabolismoRESUMO
Bone microarchitecture has been shown to provide useful information regarding the evaluation of skeleton quality with an added value to areal bone mineral density, which can be used for the diagnosis of several bone diseases. Bone mineral density estimated from dual-energy X-ray absorptiometry (DXA) has shown to be a limited tool to identify patients' risk stratification and therapy delivery. Magnetic resonance imaging (MRI) has been proposed as another technique to assess bone quality and fracture risk by evaluating the bone structure and microarchitecture. To date, MRI is the only completely non-invasive and non-ionizing imaging modality that can assess both cortical and trabecular bone in vivo. In this review article, we reported a survey regarding the clinically relevant information MRI could provide for the assessment of the inner trabecular morphology of different bone segments. The last section will be devoted to the upcoming MRI applications (MR spectroscopy and chemical shift encoding MRI, solid state MRI and quantitative susceptibility mapping), which could provide additional biomarkers for the assessment of bone microarchitecture.