Architecture and mineralization of developing cortical and trabecular bone of the mandible

Ossification of the presumptive trabecular bone in the mandibular condyle and the presumptive cortical bone in the mandibular corpus of the pig mandible was investigated during development, using micro-computed tomography (microCT). Three-dimensional architecture and mineralization characteristics were assessed from ten pigs of different developmental ages. In the condyle, increases in trabecular thickness and separation and a decrease in the trabecular number, led to an unchanged bone volume fraction. A conversion from rod-like into plate-like trabeculae was observed. Bone volume and trabecular thickness were always higher in the corpus, where an increase in bone volume fraction was caused by an increase in the trabecular thickness and a decrease in separation. A transition from a plate-like structure into a more compact structure took place. The average degree of mineralization in the condyle and the corpus increased with age. In the corpus, the degrees of mineralization were higher than in the condyle. The differences between the condyle and corpus and the changes with age could be explained by differences in the distribution of mineralization within the trabecular elements. Generally, the degrees of mineralization increased from the surface toward the centers of the trabecular elements, indicating growth of the trabecular elements by the surface apposition of new mineral.     

Microstructural trabecular bone from patients with osteoporotic hip fracture or osteoarthritis: Its relationship with bone mineral density and bone remodelling markers

Osteoporosis (OP) and osteoarthritis (OA) are the most prevalent musculoskeletal disorders in the elderly but the relationship between them is unclear. The purposes of this study are to analyze the bone turnover markers (BTM), bone mineral density (BMD) and the structural and mechanical properties of trabecular bone in patients with OP and OA, and to explore the relationship between these two diseases. We studied 12 OP patients and 13 OA patients. We analyzed BTM (β-CrossLaps and PINP), BMD and microstructural and biomechanical parameters (micro-CT). Our results were: OP group has higher levels of β-CrossLaps and lower BMD at the femoral neck. Also, OP patients have a decreased volume of trabecular bone and less trabecular number, with architecture showing prevalence of rod-like trabeculae and worse connectivity than OA patients. The biomechanical parameters were worse in OP patients. BMD was correlated with almost all the structural and biomechanical parameters. Moreover, β-CrossLaps was negatively correlated with hip BMD and with bone surface density and positively with trabecular separation. BTM, BMD and bone microstructural changes in osteoporosis are opposite to those of OA. These findings justify a less resistant bone with higher risk of fragility fractures in OP patients. These histomorphometric and biomechanical changes may be suspected by measuring of BMD and β-CrossLaps levels.     

Morphological changes of the mandibula with loss of the teeth--observation of the trabecular bone using micro-CT

The jaw bones receive complicated forces not only through the muscles, but through the teeth directly. Therefore, it is thought that the morphology of the jaw bones are greatly effected by the oral conditions. In this paper, the morphological changes of the mandibula with loss of the teeth are descrived. Furthermore, the three dimensional changes of the trabecular bones observed by micro-CT are shown. The jaw bones are of complex composition since they contain the alveolar sockets that encase the dental roots. The structures of the trabecular bone of the mandibula are constructed in order to support the teeth. The trabecular bones appear to have plate-like shape rather than rod-like shape in the three dimensional observation using micro-CT. With loss of the teeth, the height of the mandibula is rapidly shortened. And in the internal structures, both width and volume of the trabecular bone within the substantia spongiosa are reduced and the trabecular bones run in the irregular course. In addition, the plate-like shaped trabecular bones tend to transform into rod-like shaped ones. Based on these findings, it is suggested that maintenance of the intact teeth is important to keep the normal morphology of the mandibula.     

Development of the Micro Architecture and Mineralization of the Basilar Part of the Pig Occipital Bone

In this study, the development of the architecture and the degree and distribution of mineralization in the basilar part of the pig occipital bone, one of the contact points between the spine and skull base, was investigated. Multiple regions of the basiocciput of pig specimens of different gestational ages were examined with three-dimensional microcomputed tomography (microCT). The cortex of the basilar part developed from a structure with a large intertrabecular separation into a more compact one, whereas its center maintained a trabecular structure. The cortex displayed a significant increase in bone volume fraction with age, together with an increase in trabecular thickness. In the center no change in bone volume fraction was observed, because of a combined decrease in trabecular number and increase in trabecular separation. During development the degree of mineralization was almost identical in both the center and the cortex and it tended to increase with age. This chance was, however, insignificant. The distribution of mineralization within the trabecular elements of both regions demonstrated that the cores of the elements were more highly mineralized than their surfaces. This difference in mineralization confirms the preexisting notion that trabecular elements grow in size due to surface apposition of new bone that initially is less mineralized.     

Trabecular bone ratio of the mandibular condyle according to the presence of teeth: a micro-CT study

Purpose

During mastication, mechanical pressure from the dentition is transmitted to the trabecular bone of the mandible. The occlusal forces, which could thus affect condylar growth, vary with tooth loss, age, and sex. The trabecular bone of the mandibular condyle is denser in dentate subjects than in edentate subjects. However, since the different tooth groups (incisor, premolar, and molar) have different functions, they could exert different effects on the mandibular condyle. The aim of this study was to elucidate the bone quantity of the Korean mandibular condyle according to the presence of teeth using micro-computed tomography (micro-CT), thereby clarifying the influences of tooth presence on the condylar microstructure.

Methods

Thirty-one sides were scanned and reconstructed into a 3D structure using a micro-CT system. The specimen was sectioned vertically, passing through the medial and lateral poles of the mandibular condyle (P0) to enable measurement of the trabecular bone ratio. Likewise, three additional images, parallel with P0, were acquired. Mean and standard deviation values were calculated, and the t test, one-way ANOVA and post hoc analysis were performed to examine the differences among each group, classified according to the presence of teeth and according to sex.

Results

The density of the trabecular bone of the mandibular condyle was significantly associated with the presence of the molars, but not the incisors or premolars. There were significant differences between sexes.

Conclusions

The present study has provided data regarding the bone quantity of the trabeculae of the mandibular condyle according to the presence or absence of teeth.     

Regional differences in architecture and mineralization of developing mandibular bone

The goal of this study was to investigate the mutual relationship between architecture and mineralization during early development of the pig mandible. These factors are considered to define the balance between the requirements for bone growth on the one hand and for load bearing on the other. Architecture and mineralization were examined using micro-CT, whereas the mineral composition was assessed spectrophotometrically in groups of fetal and newborn pigs. The development of the condyle coincided with a reorganization of bone elements without an increase in bone volume fraction, but with an increase in mineralization and a change in mineral composition. In the corpus, the bone volume fraction and mineralization increased simultaneously with a restructuring of the bone elements and a change in mineral composition. The growth of the condyle was reflected by regional differences in architecture and mineralization. The anterior and inferior regions were characterized by a more dense bone structure and a higher mineralization as compared to posterior and superior regions, respectively. In the corpus, growth was mainly indicated by differences between buccal and lingual plates as well as between anterior, middle, and posterior regions characterized by a more compact structure and higher mineralization in the lingual and middle regions. In conclusion, the architecture and mineralization in the condyle and corpus started to deviate early during development toward their destiny as trabecular and cortical bone, respectively. These results were compatible with those obtained with mineral composition analysis. Regional differences within condyle and corpus reflected known developmental growth directions.     

大鼠牙槽骨理想模型的流固耦合数值模拟研究

载荷作用下松质骨孔隙中的液体流动是刺激骨组织细胞产生生物学响应并调控骨重建的主要因素。因此,阐明牙槽骨内孔隙结构中的液体流动情况对于深入理解力学作用在牙槽骨内的传导过程以及牙齿发育、正畸牙移动等细胞水平的调控机制具有重要意义。此工作首先进行了大鼠牙齿正畸的动物实验,并基于微计算机断层扫描(micro-CT)图像构建了牙齿-牙周韧带-牙槽骨有限元模型,分析了咬合力或正畸力作用下牙槽骨中的应变状态;进而构建了理想模型,应用流固耦合数值模拟方法,分析了动态咬合力加载下无正畸加载、正畸拉伸加载、正畸压缩加载三种情况下骨内液体的流动情况。模拟结果表明,动态咬合力作用下,沿咬合方向排列的骨小梁表面流体剪应力水平高于非咬合方向排列的骨小梁,正畸力对骨内液体的流动没有影响。上述结果说明,临床上通过调整牙齿咬合面形状等方法改变咬合力的方向,会在牙槽骨表面引起不同水平的流体剪应力,进而刺激骨组织表面的细胞产生响应,最终调控牙槽骨的结构重建。     

Development of the micro architecture and mineralization of the basilar part of the pig occipital bone

In this study, the development of the architecture and the degree and distribution of mineralization in the basilar part of the pig occipital bone, one of the contact points between the spine and skull base, was investigated. Multiple regions of the basiocciput of pig specimens of different gestational ages were examined with three-dimensional microcomputed tomography (microCT). The cortex of the basilar part developed from a structure with a large intertrabecular separation into a more compact one, whereas its center maintained a trabecular structure. The cortex displayed a significant increase in bone volume fraction with age, together with an increase in trabecular thickness. In the center no change in bone volume fraction was observed, because of a combined decrease in trabecular number and increase in trabecular separation. During development the degree of mineralization was almost identical in both the center and the cortex and it tended to increase with age. This chance was, however, insignificant. The distribution of mineralization within the trabecular elements of both regions demonstrated that the cores of the elements were more highly mineralized than their surfaces. This difference in mineralization confirms the preexisting notion that trabecular elements grow in size due to surface apposition of new bone that initially is less mineralized.     

Development of the trabecular structure within the ulnar medial coronoid process of young dogs

This study describes the timing of development of the trabecular structure of the ulnar medial coronoid process (MCP) in the dog. The right MCPs of nine healthy golden retrievers, aged 4 to 24 weeks, without signs of secondary joint disease were dissected and scanned with microcomputed tomography (micro-CT) at a voxel size of 34 microm to determine histomorphometric parameters. Bone volume fraction and mean trabecular separation show a reciprocal pattern in time, reflecting an initial high bone density (and low trabecular separation), and then a sharp drop in density at 8-10 weeks, followed by a gradual increase to high values at 24 weeks. With a similar bone volume fraction as in young bone, the older bone shows thicker trabeculae and a more plate-like structure. This is reflected in the much smaller number of trabeculae and the lower surface/volume ratio at higher age. An anisotropic structure of the trabeculae with an orientation in the direction of the proximodistal axis of the ulna is already present at 6 weeks after birth. This primary alignment was perpendicular to the humeroulnar articular surface, matching the direction of the compressive forces applied to the MCP by the humeral trochlea. The secondary alignment appeared at 13 weeks after birth and was directed along the craniocaudal axis of the MCP, toward the attachment of the anular ligament. In comparison with data from long bones and vertebrae, the findings of a high bone volume fraction and a well-defined trabecular alignment at a very early age are remarkable. The high bone volume fraction is possibly a remnant of the fetal trabecular structure, as dogs are relatively immature at birth compared to other animals. Soon after the start of steady locomotion, the trabecular structure changes into a more mature-like structure. The early trabecular alignment is possibly a reflection of the early load-bearing function of the MCP in the elbow joint.     

股骨头坏死中松质骨微观力学特性的演变规律

目的采用结合显微CT和显微有限元分析方法,即基于显微CT图像建立三维有限元模型并进行数值模拟仿真分析,无创研究不同分期的坏死股骨头松质骨的微结构和微观力学性能,以期了解在股骨头坏死的发展过程中,松质骨微结构和微观力学特性的变化规律,为临床预测股骨头坏死提供理论基础。方法采集10例股骨头坏死患者的股骨头标本的显微CT图像,按照国际骨循环研究学会分期标准分为Ⅱ期样本3例,Ⅲ期3例,Ⅳ期4例。将图像中骨组织进行阈值分割,分区域建立坏死区、侧向区、硬化区和远端区的松质骨块三维有限元模型(边长8 mm),并根据CT值赋予非均匀材料属性。利用ImageJ软件中的BoneJ插件通过识别显微CT组图像,计算测量各区域松质骨的微结构参数,包括骨体积分数、骨小梁厚度、骨小梁间隙、结构模型指数。对松质骨块施加表观应变为1%的压缩载荷,计算骨组织应力和松质骨表观刚度等参数,对比分析各分期、各分区结果。结果在松质骨微结构方面,Ⅳ期较Ⅱ期的股骨头内部硬化区和坏死区的变化最为明显,硬化区的骨体积分数不断上升,骨小梁间隙下降,结构模型指数减小,而坏死区域与之相反;在骨组织微观受力方面,Ⅱ期到Ⅲ期坏死区域的应力并没有明显变化,而硬化区域随着分期增加应力不断上升,侧向区的应力不断下降。表观刚度变化与应力变化一致。结论随着股骨头坏死程度的加剧,硬化区的松质骨微结构和力学性能变化最大,应作为临床早期诊断中重点关注的区域。此外,微结构参数并不能准确体现松质骨的力学行为,而股骨头塌陷最终取决于其力学特性,因此结合有限元分析方法可更加全面了解股骨头坏死的微观力学演变规律。     

Morphometric analysis of the anterior region of the maxillary bone for immediate implant placement using micro-CT

The purpose of this study was to elucidate the relationship between the maxillary incisor roots and surrounding alveolar structures using microscopic computerized tomography (micro-CT) for the immediate implant placement. Nineteen maxillae from 14 Korean cadavers were used in this study. All specimens were scanned and reconstructed into a three-dimensional (3D) structure using a micro-CT system. The roots of the maxillary central and lateral incisors became dramatically narrower from 6 mm above the cementoenamel junctions to the apex. The roots of the maxillary incisors and canine were located at the labial one fifths region of the alveolar bone. The angle formed by the longitudinal root axis and the alveolar bone was greatest at the maxillary canine. On the basis of the results of this study, guidelines for immediate implant placement can be suggested on the implant diameter and drilling angle to minimize damage of the alveolar plate.     

Visualization of 3D osteon morphology by synchrotron radiation micro-CT

Cortical bone histology has been the subject of scientific inquiry since the advent of the earliest microscopes. Histology - literally the study of tissue - is a field nearly synonymous with 2D thin sections. That said, progressive developments in high-resolution X-ray imaging are enabling 3D visualization to reach ever smaller structures. Micro-computed tomography (micro-CT), employing conventional X-ray sources, has become the gold standard for 3D analysis of trabecular bone and is capable of detecting the structure of vascular (osteonal) porosity in cortical bone. To date, however, direct 3D visualization of secondary osteons has eluded micro-CT based upon absorption-derived contrast. Synchrotron radiation micro-CT, through greater image quality, resolution and alternative contrast mechanisms (e.g. phase contrast), holds great potential for non-destructive 3D visualization of secondary osteons. Our objective was to demonstrate this potential and to discuss areas of bone research that can be advanced through the application of this approach. We imaged human mid-femoral cortical bone specimens derived from a 20-year-old male (Melbourne Femur Collection) at the Advanced Photon Source synchrotron (Chicago, IL, USA) using the 2BM beam line. A 60-mm distance between the target and the detector was employed to enhance visualization of internal structures through propagation phase contrast. Scan times were 1 h and images were acquired with 1.4-μm nominal isotropic resolution. Computer-aided manual segmentation and volumetric 3D rendering were employed to visualize secondary osteons and porous structures, respectively. Osteonal borders were evident via two contrast mechanisms. First, relatively new (hypomineralized) osteons were evident due to differences in X-ray attenuation relative to the surrounding bone. Second, osteon boundaries (cement lines) were delineated by phase contrast. Phase contrast also enabled the detection of soft tissue remnants within the vascular pores. The ability to discern osteon boundaries in conjunction with vascular and cellular porosity revealed a number of secondary osteon morphologies and provided a unique 3D perspective of the superimposition of secondary osteons on existing structures. Improvements in resolution and optimization of the propagation phase contrast promise to provide further improvements in structural detail in the future.     

Baby steps towards linking calcaneal trabecular bone ontogeny and the development of bipedal human gait

Trabecular bone structure in adulthood is a product of a process of modelling during ontogeny and remodelling throughout life. Insight into ontogeny is essential to understand the functional significance of trabecular bone structural variation observed in adults. The complex shape and loading of the human calcaneus provides a natural experiment to test the relationship between trabecular morphology and locomotor development. We investigated the relationship between calcaneal trabecular bone structure and predicted changes in loading related to development of gait and body size in growing children. We sampled three main trabecular regions of the calcanei using micro-computed tomography scans of 35 individuals aged between neonate to adult from the Norris Farms #36 site (1300 AD, USA) and from Cambridge (1200–1500 AD, UK). Trabecular properties were calculated in volumes of interest placed beneath the calcaneocuboid joint, plantar ligaments, and posterior talar facet. At birth, thin trabecular struts are arranged in a dense and relatively isotropic structure. Bone volume fraction strongly decreases in the first year of life, whereas anisotropy and mean trabecular thickness increase. Dorsal compressive trabecular bands appear around the onset of bipedal walking, although plantar tensile bands develop prior to predicted propulsive toe-off. Bone volume fraction and anisotropy increase until the age of 8, when gait has largely matured. Connectivity density gradually reduces, whereas trabeculae gradually thicken from birth until adulthood. This study demonstrates that three different regions of the calcaneus develop into distinct adult morphologies through varying developmental trajectories. These results are similar to previous reports of ontogeny in human long bones and are suggestive of a relationship between the mechanical environment and trabecular bone architecture in the human calcaneus during growth. However, controlled experiments combined with more detailed biomechanical models of gait maturation are necessary to establish skeletal markers linking growth to loading. This has the potential to be a novel source of information for understanding loading levels, activity patterns, and perhaps life history in the fossil record.     

Effects of Loading Orientation on the Morphology of the Predicted Yielded Regions in Trabecular Bone

While the effects of bone mineral density and architecture in osteoporotic bone have been studied extensively, the micromechanics of yielding and failure have received less attention. However, understanding architectural features associated with failure should provide insight into assessing bone quality. In this study, microstructural finite element models were used to compute regions of tissue level yielding in ten bovine tibial trabecular bone samples. The morphology, number, and mean volume of the yielded regions were quantified for four apparent strains under two loading conditions. For on-axis loading, the mean aspect ratio of the tissue that yielded due to compressive strain increased with increasing apparent strain, expanding along the principal trabecular orientation. This suggests that tissue level yielding progresses along vertical trabeculae when a specimen is loaded on-axis. The number, but not the volume, of the regions yielded due to tensile strain increased with increasing applied load, consistent with relaxation and redistribution of stresses around the yielded regions. When the specimens were compressed perpendicular to the principal axis, the aspect ratio of the yielded regions was close to one, while the number, mean volume, and mean thickness of the yielded regions increased. This indicates that localized high strains consistent with bending rather than axial deformation of struts occur at the tissue level. Overall, the results provide new insight into trabecular bone failure, which is relevant to assessing diagnostic tests for fracture risk or evaluating osteoporosis treatments.     

Architecture and mineralization of developing trabecular bone in the pig mandibular condyle

Architecture and mineralization are important determinants of trabecular bone quality. To date, no quantitative information is available on changes in trabecular bone architecture and mineralization of newly formed bone during development. Three-dimensional architecture and mineralization of the trabecular bone in the mandibular condyle from six pigs of different developmental ages were investigated with micro-CT. Anteriorly in the condyle, a more advanced state of remodeling was observed than posteriorly, where more active growth takes place. Posteriorly, the bone volume fraction increased with age (r=0.87; P<0.05) by an increase of trabecular thickness (r=0.88; P<0.05), while the number of trabeculae declined (r=-0.86; P<0.05). Anteriorly, despite an increase in trabecular thickness (r=0.97; P<0.001), there was no change in bone volume fraction due to a simultaneous decline in trabecular number (r=-0.84; P<0.05) and increase in trabecular separation (r=0.95; P<0.01). Posteriorly, rods were remodeled into plates as expressed by the structure model index (r=-0.97; P<0.001), whereas anteriorly, a plate-like structure was already present in early stages. The trabecular structure had a clear orientation throughout the developmental process. The global degree of mineralization increased both anteriorly (r=0.86; P<0.05) and posteriorly (r=0.89; P<0.05). We suggest that the degree of mineralization does not depend on the bone volume, but on the thickness of the trabeculae as the mineralized centers of trabeculae were getting larger and more highly mineralized with age compared to their appositional layers. This indicates that besides apposition of new bone material on the surface of trabeculae, the mineralized tissue in their centers still changes and matures.     

Long-term osteopenic changes in cancellous bone structure in ovariectomized rats

Cancellous bone mass decreases following ovariectomy in rodents, providing a useful model for post-menopausal bone loss in humans. This study describes and quantifies the longer-term changes in cancellous bone structure in the ovariectomized (OVX) rat. Rats were OVX or sham-OVX at 100 days of age and bones were collected 540 days later. Lumbar vertebral bodies were prepared for microradiography and structural analyses (nodal analyses and star volume analyses) of cancellous bone. Proximal humerii were prepared for scanning electron microscopy (SEM). Microradiography confirmed the loss of cancellous bone from the central spongiosa regions of the vertebral bodies and the humerii in the OVX rats. Changes in trabecular structural elements included relative increases in the number of free to free, cortical to free, cortical to node struts and decreases in the node to node struts in the OVX animals compared with controls. There were increases in average lengths of the node to free, node to node, and free to free trabecular struts in the OVX animals. The marrow star volume was increased in the OVX animals indicating a greater trabecular separation in these animals compared with controls. Viewed by SEM, metaphyseal trabeculae in the controls consisted of rods and plates but in the OVX animals the remaining trabeculae were mostly longitudinal rods with smaller transverse connecting rods. The remaining bone in the OVX animals was found in the lateral metaphyseal areas and is consistent with maintenance of the structural capacity of the bone. These long-term changes in cancellous bone structure are likely due to the continuation of functional skeletal loading but a decrease in gonadal hormones resulting in a decreased necessity to maintain a skeletal mineral store for reproduction (e.g., pregnancy and lactation). © 1993 Wiley-Liss, Inc.     

Iliac cortical thickness in the neonate – the gradient effect

Recent studies of the neonatal ilium are beginning to reveal that a recognizable structural patterning of trabecular bone is present in the absence of any direct stance-related weight transfer. However, little is known about the organization of compact bone in the ilium and the way in which it is laid down during the earliest stages of development. This study investigates cortical bone thickness across both gluteal and pelvic iliac shells in the human neonatal ilium. Measurements of specific regions of interest on the iliac cortices were recorded using reconstructed micro-computed tomography scans from 30 neonatal ilia. Analysis of gluteal and pelvic cortical thicknesses revealed a distinctive patterning consistent with the expected bone distribution achieved through early bone modelling and remodelling. The analysis of this pattern is important for understanding the relationship between trabecular bone patterning and cortical bone structure in the earliest stages of pelvic development prior to locomotive influences and its response to the specific functional forces acting during this period.     

舌骨形态学与显微结构的观测

目的通过对22例标本舌骨进行形态学观测及micro-CT扫描,了解其内部骨小梁的结构特点,为舌骨发育情况的判断及临床诊疗提供理论依据。方法肉眼观测22例完整舌骨骨性标本舌骨体与舌骨大角的连接方式,观察舌骨小角的出现率,利用micro-CT对舌骨进行扫描,以观测其内部骨小梁的结构特点并进行重建。结果舌骨以完整连接型为主,占59.09%,单侧分离型占36.36%,双侧分离型占4.55%;舌骨小角的出现率为31.8%;micro-CT扫描可清晰显示舌骨各部分的显微结构,内部骨小梁的分布主要集中于舌骨体两端和舌骨大角前端处,即舌骨体与舌骨大角连接处,并且不论是完整连接型还是单侧分离型,其连接处均存在骨化中心,可见连接处有明显骨化愈合。结论舌骨并不是一个完整的整体结构,根据发育过程可分为完整型、单侧分离型和双侧分离型;micro-CT扫描可以很好地显示舌骨内部骨小梁的结构特点及分布规律,为舌骨的后期研究提供了理论依据。     

下肢力线与膝关节软骨下骨板杆结构和软骨退变的关系

目的利用骨小梁分割技术(individual trabecula segmentation,ITS)和组织学方法分析膝关节骨关节炎(osteoarthritis,OA)的胫骨平台骨软骨标本,研究下肢力线与软骨下小梁骨显微结构以及软骨退变的关系。方法接受全膝关节置换术病人术前进行下肢全长X线平片拍摄,进行髋-膝-踝(hip-knee-ankle,HKA)角测量。收集术中切除的胫骨平台标本进行显微CT扫描,利用ITS分析软骨下骨小梁结构。通过组织学方法评价软骨退变。对下肢力线与软骨下骨显微结构参数改变和软骨退变进行相关性分析。结果胫骨平台软骨下骨小梁体积分数(BV/TV)、骨小板(pBV/TV)体积分数、骨小杆体积分数(rBV/TV)及轴向骨小梁体积分数(aBV/TV)、骨小板及骨小杆体积比值(P/R)、骨小板数量(pTb. N)、骨小板厚度(pTb. Th)、骨小板表面积(pTb. S)、骨小杆长度(rTb. L)、骨小板-骨小板连接密度(P-P Junc. D)、骨小板-骨小杆连接密度(P-R Junc. D)与软骨退变程度和下肢力线角度显著相关。HKA角度绝对值越大,受累侧胫骨平台软骨下骨小板增厚,骨小板数量增加,骨小板-骨小板以及骨小板-骨小杆的连接性越强,同时软骨退变OARSI评分也越高。结论下肢力线异常可能通过改变膝关节正常的应力分布而导致胫骨平台软骨下骨小梁显微结构异常,尤其是骨小板和轴向骨小梁的显著增多和增厚可能是进一步加重被覆软骨退变、导致OA进展的危险因素。因此,通过改变力线和调节软骨下骨代谢有望成为早期干预骨关节炎发生和发展的切入点。     

超重环境对骨组织生物力学性能和形态结构的影响

目的 探讨超重环境对骨组织生物力学性能及骨组织形态结构的影响,为航天员和飞行员安全飞行训练及 最大耐受高重力值的确定提供理论支撑。 方法 采用本课题组自主设计的超重加载平台构建超重动物模型,加载 方式为腹背方向承受向心加速度,加速度分别为 5、10、20 g,离心 45 s,1 次/ d,5 d / 周,连续 4 周。 使用 Instron 5865 材料力学试验机对离体骨组织进行三点弯曲试验,通过测量力学参数的变化,分析超重环境对骨组织生物力学性 能的影响;通过双能 X 线骨密度仪扫描、Micro-CT 扫描、骨组织染色等技术,检测骨矿物质含量、骨密度及骨小梁等 形态学参数的变化,观察超重环境对骨组织形态结构的影响。 结果 超重加载可显著降低小鼠胫骨的断裂应力及 弹性模量。 超重环境导致骨组织中骨体积分数下降,骨小梁厚度以及骨小梁数量显著降低,骨小梁排列紊乱。 结 论 超重环境对骨组织生物力学性能及骨组织形态结构的影响与超重载荷的强度密切相关。 低(5 g)强度超重载 荷能够降低骨小梁厚度,但对其力学性能的影响很小。 中(10 g)、高(20 g)强度超重载荷能够显著触发骨流失以 及骨力学性能的下降。 随着超重载荷的增加,机体的生理调节无法阻止骨量和力学性能下降的趋势