Quantification of Bone Microarchitecture with the Structure Model Index

The deterioration of cancellous bone structure due to aging and disease is characterized by a conversion from plate elements to rod elements. Consequently the terms “rod-like” and “plate-like” are frequently used for a subjective classification of cancellous bone. In this work a new morphometric parameter called Structure Model Index (SMI) is introduced, which makes it possible to quantify the characteristic form of a three-dimensionally described structure in terms of the amount of plates and rod composing the structure. The SMI is calculated by means of three-dimensional image analysis based on a differential analysis of the triangulated bone surface. For an ideal plate and rod structure the SMI value is 0 and 3, respectively, independent of the physical dimensions. For a structure with both plates and rods of equal thickness the value lies between 0 and 3, depending on the volume ratio of rods and plates. The SMI parameter is evaluated by examining bone biopsies from different skeletal sites. The bone samples were measured three-dimensionally with a micro-CT system. Samples with the same volume density but varying trabecular architecture can uniquely be characterized with the SMI. Furthermore the SMI values were found to correspond well with the perceived structure type.     

A Three-Dimensional Histological Method for Direct Determination of the Number of Trabecular Termini in Cancellous Bone

Osteoporotic fractures occur frequently in aging populations. Established methods for analyzing microarchitecture indicate that cancellous bone loss in the elderly is associated with progressive reduction in the connectivity of the trabecular network. This disconnection may explain the increased skeletal fragility that is sometimes out of proportion to the amount of bone lost. Connectivity, however, is difficult to measure and usually requires indirect methods. We describe development of a simple, inexpensive and direct procedure for counting sites of trabecular disconnection. The method is based upon preparation of 300-500 fjim thick slices of methylmethacrylate embedded material rather than the more usual thin 8 μm. histological sections. The marrow tissue is retained within the thick slice; this is essential for conservation of any detached bone fragments. In such preparations differential superficial staining of the upper and lower surfaces with alizarin red and light green, respectively, allows the two-dimensional image to be viewed at the same time as its three-dimensional counterpart. In this way, “real” (i. e., unstained) trabecular termini can be distinguished from “apparent” (i. e., stained red or green) termini that are artifacts of the plane of section. Partly polarized light enhances the microscope image. The method does not destroy the material for subsequent bone histomorphom-etry and, therefore, may be a useful adjunct to iliac bone biopsy analysis in studies of metabolic bone disease.     

Study on the Microstructure of Human Articular Cartilage/Bone Interface

For improving the theory of gradient microstructure of cartilage/bone interface, human distal femurs were studied. Scanning Electron Microscope (SEM), histological sections and MicroCT were used to observe, measure and model the microstructure of cartilage/bone interface. The results showed that the cartilage/bone interface is in a hierarchical structure which is composed of four different tissue layers. The interlocking of hyaline cartilage and calcified cartilage and that of calcified cartilage and subchondral bone are in the manner of “protrusion-pore” with average diameter of 17.0 μm and 34.1 μm respectively. In addition, the cancellous bone under the cartilage is also formed by four layer hierarchical structure, and the adjacent layers are connected by bone trabecula in the shape of H, I and Y, forming a complex interwoven network structure. Finally, the simplified structure model of the cartilage/bone interface was proposed according to the natural articular cartilage/bone interface. The simplified model is a 4-layer gradient biomimetic structure, which corresponds to four different tissues of natural cartilage/bone interface. The results of this work would be beneficial to the design of bionic scaffold for the tissue engineering of articular cartilage/bone.     

A Method to Stain Decalcified Bone without Loss of Structural Detail

A modification of Bodian's protargol-S technique is done on 7 μm sections of decalcified bone. Light microscopic results are greatly improved when compared to either ground bone sections or decalcified bone stained routinely with hematoxylin and eosin.     

Quantification of Bone Microarchitecture with the Structure Model Index

The deterioration of cancellous bone structure due to aging and disease is characterized by a conversion from plate elements to rod elements. Consequently the terms "rod-like" and "plate-like" are frequently used for a subjective classification of cancellous bone. In this work a new morphometric parameter called Structure Model Index (SMI) is introduced, which makes it possible to quantify the characteristic form of a three-dimensionally described structure in terms of the amount of plates and rod composing the structure. The SMI is calculated by means of three-dimensional image analysis based on a differential analysis of the triangulated bone surface. For an ideal plate and rod structure the SMI value is 0 and 3, respectively, independent of the physical dimensions. For a structure with both plates and rods of equal thickness the value lies between 0 and 3, depending on the volume ratio of rods and plates. The SMI parameter is evaluated by examining bone biopsies from different skeletal sites. The bone samples were measured three-dimensionally with a micro-CT system. Samples with the same volume density but varying trabecular architecture can uniquely be characterized with the SMI. Furthermore the SMI values were found to correspond well with the perceived structure type.     

A Procedure for Preparing Undecalcified and Unembedded Bone Sections for Light Microscopy

We have developed a procedure for light microscopic investigation of undecalcified and unembeddedbone sections. Biopsy samples of human metatarsus and femur and rat femur were fixed in aldehydes and sectioned with a cutting machine equipped with a diamond saw blade. Free sections 100-150 μm thick, stained with toluidine blue and von Kossa, did not show artifacts following the cutting, and the spatial relations of mineralized and nonmineralized components remained intact. Compact and trabecular bone, bone marrow and all cell types appeared well preserved and easily recognizable. Our procedure provides a simple and rapid method for preparing bone sections which undergo no chemical treatment other than fixation. This method is a useful alternative to standard histological protocols for studying bone specimens.     

The contribution of cancellous bone to long bone strength and rigidity

A recent article (Burr and Piotrowski, 1982) suggested that structural analyses of long bone cross-sectional geometry will be inaccurate and should be considered inappropriate when cancellous bone accounts for 10-15% or more of the cross-sectional area. Consideration of material property differences between compact and cancellous bone, however, indicates that even significant proportions of cancellous bone (10-40% of total cross-sectional area) will very likely have negligible effects on bone strength and rigidity, and can be effectively ignored in geometrical analyses of diaphyseal sections. In metaphyseal and epiphyseal regions, however, geometric analyses of section properties such as area moments of inertia are inappropriate, both because of significant trabecular bone effects, and because of the inherent constraints of mechanical beam models.     

Changes in the Fabric and Compliance Tensors of Cancellous Bone due to Trabecular Surface Remodeling,Predicted by a Digital Image-based Model

Fabric and compliance tensors of a cube of cancellous bone with a complicated three-dimensional trabecular structure were obtained for trabecular surface remodeling by using a digital image-based model combined with a large-scale finite element method. Using mean intercept length and a homogenization method, the fabric and compliance tensors were determined for the trabecular structure obtained in the computer remodeling simulation. The tensorial quantities obtained indicated that anisotropic structural changes occur in cancellous bone adapting to the compressive loading condition. There were good correlations between the fabric tensor, bone volume fraction, and compliance tensor in the remodeling process. The result demonstrates that changes in the structural and mechanical properties of cancellous bone are essentially anisotropic and should be expressed by tensorial quantities.     

How do trabeculae affect the calculation of structural properties of bone?

One difficulty that arises in an analysis of the cross-sectional properties of bone is whether to include cancellous bone in the analysis. The purpose of this paper is to determine how different amounts of cancellous bone affect the measurement of structural properties of bone cross-sections. Thirty-two tibial and femoral cross-sections were chosen at random from a series of cross-sectioned nonhuman primate bones. Geometrical properties were calculated for the cross-sections, and torsional and bending stress analyses were performed. The results suggest that the effect of including cancellous bone in the analysis is closely related to the amount of bone, where it lies within the cross-section, and the type of analysis performed. Including cancellous bone in calculations of structural properties of bone cross-sections may cause the strength and stiffness of the bone to be exaggerated.     

A Method for Histological Preparation of Undecalcified Bone Sections Containing Acrylic Bone Cement

An improved and time reducing method is presented for the histological evaluation of bone containing polymethylmethacrylate (PMMA) bone cement. The undecalcified bone was embedded in epoxy resin and sections of 50-100 μm thickness were produced using a commercially available cutting grinding system. The sections were stained with Stevenel's blue and van Gieson picrofuchsin or a modified hematoxylin-eosin. PMMA bone cement was not dissolved and remained enabling examination in situ of an intact cement bone interface and tissue reaction without decalcification.     

Long term follow-up of reconstruction with allogeneic mandibular bone crib packed with autogenous particulate cancellous bone marrow

Allogeneic mandibular bone processed by the deep frozen method was used as a biologic crib for mandibular reconstruction. The allogeneic mandible is biocompatible, bioresorbable, of low antigenicity and provides the morphology for symphysis contour, angle of mandible and dental arch form. The particulate cancellous bone marrow (PCBM) contains marked osteogenic potential of hematopoietic marrow, which promotes osteogenesis. The cancellous marrow graft lacks structure and requires a crib to house it during the bone regeneration to the consolidation phase. Fresh frozen mandible was hollowed out for packing with PCBM prior to securing it to the defect by a rigid fixation method. Four cases of large mandibular defects resulting from treatment of benign odontogenic tumors were reconstructed utilizing this technique. All cases showed excellent facial contour and function satisfactorily in mastication and pronunciation. Complete graft incorporation and restoration of the osseous continuities were observed for four to 12 years after the operation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Material Changes in Osteoporotic Human Cancellous Bone Following Infiltration with Acrylic Bone Cement for a Vertebral Cement Augmentation

Bone cement infiltration can be effective at mechanically augmenting osteoporotic vertebrae. While most published literature describes the gain in mechanical strength of augmented vertebrae, we report the first measurements of viscoelastic material changes of cancellous bone due to cement infiltration. We infiltrated cancellous core specimen harvested from osteoporotic cadaveric spines with acrylic bone cement. Bone specimen before and after cement infiltration were subjected to identical quasi-static and relaxation loading in confined and free compression. Testing data were fitted to a linear viscoelastic model of compressible material and the model parameters for cement, native cancellous bone, and cancellous bone infiltrated (composite) with cement were identified. The fitting demonstrated that the linear viscoelastic model presented in this paper accurately describes the mechanical behaviour of cement and bone, before and after infiltration. Although the composite specimen did not completely adopt the properties of bulk bone cement, the stiffening of cancellous bone due to cement infiltration is considerable. The composite was, for example, 8.5 times stiffer than native bone. The local stiffening of cancellous bone in patients may alter the load transfer of the augmented motion segment and may be the cause of subsequent fractures in the vertebrae adjacent to the ones infiltrated with cement. The material model and parameters in this paper, together with an adequate finite-element model, can be helpful to investigate the load shift, the mechanism for subsequent fractures, and filling patterns for ideal cement infiltration.     

An Improved Immunostaining and Imaging Methodology to Determine Cell and Protein Distributions within the Bone Environment

Bone is a dynamic tissue that undergoes multiple changes throughout its lifetime. Its maintenance requires a tight regulation between the cells embedded within the bone matrix, and an imbalance among these cells may lead to bone diseases such as osteoporosis. Identifying cell populations and their proteins within bone is necessary for understanding bone biology. Immunolabeling is one approach used to visualize proteins in tissues. Efficient immunolabeling of bone samples often requires decalcification, which may lead to changes in the structural morphology of the bone. Recently, methyl-methacrylate embedding of non-decalcified tissue followed by heat-induced antigen retrieval has been used to process bone sections for immunolabeling. However, this technique is applicable for bone slices below 50-µm thickness while fixed on slides. Additionally, enhancing epitope exposure for immunolabeling is still a challenge. Moreover, imaging bone cells within the bone environment using standard confocal microscopy is difficult. Here we demonstrate for the first time an improved methodology for immunolabeling non-decalcified bone using a testicular hyaluronidase enzyme-based antigen retrieval technique followed by two-photon fluorescence laser microscopy (TPLM) imaging. This procedure allowed us to image key intracellular proteins in bone cells while preserving the structural morphology of the cells and the bone.     

A Simple and Rapid Staining Technique for Plastic Embedded Cartilage and Bone

In this report we describe a simple and rapid staining technique for cartilage and bone embedded in Araldite. Semitbin sections of embryonic vertebrae obtained from 15 to 17 day mouse fetuses were stained using an aqueous solution 0.25% with respect to methylene blue, 0.25% with respect to azure A, and 0.5% with respect to Na₂ CO₃, then counterstained with 1% aqueous pararosaniline chloride (MAP). Results were compared with toluidine blue stained sections. MAP permitted good discrimination of developmental stages of both cells and extracellular matrix within vertebral ossification centers during endochondral ossification. The technique is simple, rapid and applicable to plastic embedded sections, and can be used prior to ultrastructural examination.     

Finite element calculated uniaxial apparent stiffness is a consistent predictor of uniaxial apparent strength in human vertebral cancellous bone tested with different boundary conditions

Strong correspondence between the uniaxial apparent strength and stiffness of cancellous bone allows the use of stiffness as a predictor of bone strength. Measured values of mechanical properties in cancellous bone can be different between experiments due to different experimental conditions. In the current study, bone volume fraction, experimentally determined and finite element (FE) predicted stiffness were examined as predictors of cancellous bone ultimate strength in two different groups each of which was tested using a different end constraint. It is demonstrated that, although always significant, the relationships of strength with bone volume fraction and experimentally determined stiffness are different between test groups. Apparent stiffness, estimated by FE modeling, predicts the ultimate strength of human cancellous bone consistently for all examined experimental protocols.     

Permeability study of vertebral cancellous bone using micro-computational fluid dynamics

Understanding of cancellous bone permeability is lacking despite its importance in designing tissue engineering scaffolds for bone regeneration and orthopaedic surgery that relies on infiltration of bone cement into porous cancellous bone. We employed micro-computational fluid dynamics to investigate permeability for 37 cancellous bone specimens, eliminating stringent technical requirements of bench-top testing. Microarchitectural parameters were also determined for the specimens and correlated, using uni-variate and multi-variate regression analyses, against permeability. We determined that bone surface density, trabecular pattern factor, structure model index and trabecular number are other possible predictors of permeability (with R values of 0.47, 0.44, 0.40 and 0.33), in addition to the commonly used porosity parameter (R value of 0.38). Pooling these parameters and performing multi-variate linear regression analysis improved yield the R-value of 0.50, indicating that porosity alone is a poor predictor of cancellous bone permeability and, therefore, other parameters should be included for a better and improved linear model.     

An approximate model for cancellous bone screw fixation

This paper presents a finite element (FE) model to identify parameters that affect the performance of an improved cancellous bone screw fixation technique, and hence potentially improve fracture treatment. In cancellous bone of low apparent density, it can be difficult to achieve adequate screw fixation and hence provide stable fracture fixation that enables bone healing. Data from predictive FE models indicate that cements can have a significant potential to improve screw holding power in cancellous bone. These FE models are used to demonstrate the key parameters that determine pull-out strength in a variety of screw, bone and cement set-ups, and to compare the effectiveness of different configurations. The paper concludes that significant advantages, up to an order of magnitude, in screw pull-out strength in cancellous bone might be gained by the appropriate use of a currently approved calcium phosphate cement.     

llizarov骨搬运技术治疗胫骨骨缺损的疗效及术后延迟愈合或不愈合的影响因素分析

摘要 目的：探讨 llizarov骨搬运技术治疗胫骨骨缺损的疗效及术后延迟愈合或不愈合的影响因素分析。方法：选取 2016年 6月-2020年 10月本院收治的 90例胫骨骨缺损患者为研究对象,患者均给予 llizarov骨搬运技术治疗。对患者的手术效果指标、并发症发生率进行记录统计。并对患者进行门诊随访观察,统计患者延迟愈合或不愈合的发生情况,据此将患者分为愈合组和延迟愈合或不愈合组。采用单因素及多因素 Logistic回归分析患者术后延迟愈合或不愈合发生的影响因素。结果：患者住院时间为(12.11± 2.98)d、开始负重时间为(45.39± 7.78)d、完全负重时间(76.41± 11.23)d。患者术后并发症发生率为 8.89%(8/90)。经随访观察,共有 29例患者出现术后延迟愈合或不愈合,发生率为 32.22%（29/90）。而延迟愈合或不愈合组患者的伤口感染、合并软组织损伤、合并腓骨骨折、术后过早活动及有吸烟史的人数占比高于愈合组患者(P<0.05)。经多因素 Logistic回归分析显示：伤口感染、合并软组织损伤、合并腓骨骨折、术后过早活动、有吸烟史是患者术后延迟愈合或不愈合的危险因素(P<0.05)。结论：llizarov骨搬运技术治疗胫骨骨缺损的疗效较好,患者的手术时间短、术中失血量少、住院时间、开始负重时间均较短,并发症发生率低,治疗安全性较好,但患者易出现术后延迟愈合或不愈合现象,可能与伤口感染、合并软组织损伤、合并腓骨骨折、术后过早活动、吸烟史有关。     

Estrogen-induced osteogenesis in intact female mice lacking ERbeta

We recently found that estrogen receptor (ER) antagonists prevent high-dose estrogen from inducing the formation of new cancellous bone within the medullary cavity of mouse long bones. In the present investigation, we studied the role of specific ER subtypes in this response by examining whether this is impaired in female ERbeta(-/-) mice previously generated by targeted gene deletion. Vehicle or 17beta-estradiol (E(2)) (range 4-4,000 microg. kg(-1). day(-1)) was administered to intact female ERbeta(-/-) mice and wild-type littermates by subcutaneous injection for 28 days. The osteogenic response was subsequently assessed by histomorphometry performed on longitudinal and cross sections of the tibia. E(2) was found to cause an equivalent increase in cancellous bone formation in ERbeta(-/-) mice and littermate controls, as assessed at the proximal and distal regions of the proximal tibial metaphysis. E(2) also resulted in a similar increase in endosteal mineral apposition rate in these two genotypes, as assessed at the tibial diaphysis. In contrast, cortical area in ERbeta(-/-) mice was found to be greater than that in wild types irrespective of E(2) treatment, as was tibial bone mineral density as measured by dual-energy X-ray absorptiometry, consistent with previous reports of increased cortical bone mass in these animals. We conclude that, although ERbeta acts as a negative modulator of cortical modeling, this isoform does not appear to contribute to high-dose estrogen's ability to induce new cancellous bone formation in mouse long bones.