Lattice strains and load partitioning in bovine trabecular bone

Microdamage and failure mechanisms have been well characterized in bovine trabecular bone. However, little is known about how elastic strains develop in the apatite crystals of the trabecular struts and their relationship with different deformation mechanisms. In this study, wide-angle high-energy synchrotron X-ray diffraction has been used to determine bulk elastic strains under in situ compression. Dehydrated bone is compared to hydrated bone in terms of their response to load. During compression, load is initially borne by trabeculae aligned parallel to loading direction with non-parallel trabeculae deforming by bending. Ineffective load partitioning is noted in dehydrated bone whereas hydrated bone behaves like a plastically yielding foam.     

Novel tubular composite matrix for bone repair

Tissue engineering develops organ replacements to overcome the limitations associated with autografts and allografts. The work presented here details the development of biodegradable, porous, three-dimensional polymer-ceramic-sintered microsphere matrices to support bone regeneration. Poly(lactide-co-glycolide)/hydroxyapatite microspheres were formed using solvent evaporation technique. Individual microspheres were placed in a cylindrical mold and sintered at various temperatures. Scaffolds were characterized using scanning electron microscopy, mercury porosimetry, and mechanical testing in compression. After varying the temperature of sintering, a single temperature was selected and the time of sintering was varied. Mechanical testing indicated that as the sintering temperature or time was increased, the elastic modulus, compressive strength, maximum compressive load, and energy at failure significantly increased. Furthermore, increasing the sintering temperature or time resulted in a decreased porosity and the spherical morphology of the microspheres was lost as the microspheres blended together. To more closely mimic the bone marrow cavity observed in native bone tissue, tubular composite-sintered microsphere matrices were formed. These scaffolds demonstrated no statistically significant difference in compressive mechanical properties when compared with cylindrical composite-sintered microsphere matrices of the same dimension. One potential application for these scaffolds is bone regeneration.     

Demineralized bone matrix as a biological scaffold for bone repair

Experimental models were created in rat fibula to represent impaired bone healing so that biological deficiencies that cause bone repair to fail or to be delayed may be investigated. These models consist of a 4-mm-long segmental defect, created in rat fibula by osteotomy, and fitted with a 7-mm-long tubular specimen of demineralized bone matrix (DBM) over the cut ends of the fibula. The experiments in this study involved various modifications of the DBM scaffold designed to reduce its osteoinductive activity: steam sterilization (sDBM), ethylene oxide sterilization (eoDBM), trypsin digestion (tDBM), and guanidine hydrochloride extraction (gDBM). Bone healing was evaluated by bending rigidity of the fibula and mineral content of the repair site at 7 weeks post-surgery. The sDBM scaffolds resorbed completely by 7 weeks and hence this model was a nonhealing negative control. Rigidities in the unmodified DBM and tDBM groups were comparable, whereas in the gDBM and eoDBM groups it was significantly reduced. Histologically, in the 4-mm defects repaired with unmodified DBM, direct and endochondral bone formation in the scaffold and the defect resulted in a neocortex consisting of woven and lamellar bone uniting the broken bone by 7 weeks post-surgery. We conclude that the eoDBM and gDBM groups represent failure or delay of the bone repair process when compared with the unmodified DBM group in which the process is analogous to normal bone healing.     

Star volume in bone research. A histomorphometric analysis of trabecular bone structure using vertical sections

Conventional bone histomorphometry performed on iliac crest biopsies does not generally provide unbiased stereological estimates of parameters related to bone structure due to the anisotropy of trabecular bone; this, however, can be obtained with vertical sections, which are anisotropic sections, in combination with an anisotropic test system. A practical procedure for obtaining vertical sections from bone is described. The new stereological parameter, the star volume, can provide an unbiased estimation of the absolute mean size of the marrow space and thus give an indirect estimate of the connectivity of trabecular bone structure. The marrow space star volume of vertebral bodies and iliac crest increases with age in both sexes demonstrating that the structural bone changes which occur with age is a topological one with changes in trabecular connectivity. The practical procedure including sampling efficiency for marrow space star volume is described. © 1993 Wiley-Liss, Inc.     

In vivo study on hydroxyapatite scaffolds with trabecular architecture for bone repair

The objective of this research was to investigate the bone formation and angio-conductive potential of hydroxyapatite (HA) scaffolds closely matched to trabecular bone in a canine segmental defect after 3 and 12 weeks post implantation. Histomorphometric comparisons were made between naturally forming trabecular bone (control) and defects implanted with scaffolds fabricated with micro-size (M-HA) and nano-size HA (N-HA) ceramic surfaces. Scaffold architecture was similar to trabecular bone formed in control defects at 3 weeks. No significant differences were identified between the two HA scaffolds; however, significant bone in-growth was observed by 12 weeks with 43.9 +/- 4.1% and 50.4 +/- 8.8% of the cross-sectional area filled with mineralized bone in M-HA and N-HA scaffolds, respectively. Partially organized, lamellar collagen fibrils were identified by birefringence under cross-polarized light at both 3 and 12 weeks post implantation. Substantial blood vessel infiltration was identified in the scaffolds and compared with the distribution and diameter of vessels in the surrounding cortical bone. Vessels were less numerous but significantly larger than native cortical Haversian and Volkmann canals reflecting the scaffold architecture where open spaces allowed interconnected channels of bone to form. This study demonstrated the potential of trabecular bone modeled, highly porous and interconnected, HA scaffolds for regenerative orthopedics.     

Porcine enamel matrix derivative enhances trabecular bone regeneration during wound healing of injured rat femur.

To elucidate the effects of enamel matrix derivative (EMD: Emdogain) on bone regeneration in rat femurs after drill-hole injury, defects in bone were filled with either EMD or its carrier, PGA, as control. On postoperative days 4 to 28, dissected femurs were examined by means of various morphological approaches. In both experimental groups, formation of trabecular bone, which was immunostained for bone sialoproteins (BSP), had occurred in the medullary cavities at cylindrical bone defects on Day 7 postoperatively. Cuboidal osteoblasts were clearly observed on these newly-formed BSP-positive bone trabeculae. On Days 7 and 14, many multinucleated giant cells, which strongly expressed cathepsin K, had appeared on these bone trabeculae, indicating active bone remodeling. In these bone trabeculae, Ca and P weight % and Ca/P ratio were similar to those of cortical bone, and there was no significant difference between the PGA- and EMD-applied groups. Bone volume fraction of newly-formed bone trabeculae on Day 7 postoperatively was significantly higher in the EMD-applied group than in the PGA-applied controls. Because of active bone remodeling and the marked decrease of bone volume, on Days 14 and 28 postoperatively, however, there was no longer a significant difference in trabecular bone volume fraction between the experimental groups. Our results suggest that EMD possesses an osteo-promotive effect on bone and medullary regeneration during wound healing of injured long bones.     

Prediction of mechanical properties of trabecular bone using quantitative MRI

Techniques for quantitative magnetic resonance imaging (MRI) have been developed for non-invasive estimation of the mineral density and structure of trabecular bone. The R*(2) relaxation rate (i.e. 1/T*(2)) is sensitive to bone mineral density (BMD) via susceptibility differences between trabeculae and bone marrow, and by binarizing MRI images, structural variables, such as apparent bone volume fraction, can be assessed. In the present study, trabecular bone samples of human patellae were investigated in vitro at 1.5 T to determine the ability of MRI-derived variables (R*(2) and bone volume fraction) to predict the mechanical properties (Young's modulus, yield stress and ultimate strength). Further, the MRI variables were correlated with reference measurements of volumetric BMD and bone area fraction as determined with a clinical pQCT system. The MRI variables correlated significantly (p < 0.01) with the mechanical variables (r = 0.32-0.46), BMD (r = 0.56) and bone structure (r = 0.51). A combination of R*(2) and MRI-derived bone volume fraction further improved the prediction of yield stress and ultimate strength. Although pQCT showed a trend towards better prediction of the mechanical properties, current results demonstrate the feasibility of combined MR imaging of marrow susceptibility and bone volume fraction in predicting the mechanical strength of trabecular bone and bone mineral density.     

Vibrational testing of trabecular bone architectures using rapid prototype models

The purpose of this study was to investigate if standard analysis of the vibrational characteristics of trabecular architectures can be used to detect changes in the mechanical properties due to progressive bone loss. A cored trabecular specimen from a human lumbar vertebra was microCT scanned and a three-dimensional, virtual model in stereolithography (STL) format was generated. Uniform bone loss was simulated using a surface erosion algorithm. Rapid prototype (RP) replicas were manufactured from these virtualised models with 0%, 16% and 42% bone loss. Vibrational behaviour of the RP replicas was evaluated by performing a dynamic compression test through a frequency range using an electro-dynamic shaker. The acceleration and dynamic force responses were recorded and fast Fourier transform (FFT) analyses were performed to determine the response spectrum. Standard resonant frequency analysis and damping factor calculations were performed. The RP replicas were subsequently tested in compression beyond failure to determine their strength and modulus. It was found that the reductions in resonant frequency with increasing bone loss corresponded well with reductions in apparent stiffness and strength. This suggests that structural dynamics has the potential to be an alternative diagnostic technique for osteoporosis, although significant challenges must be overcome to determine the effect of the skin/soft tissue interface, the cortex and variabilities associated with in vivo testing.     

骨修复材料的研究进展

由于自体骨和异体骨移植治疗骨缺损存在许多不可避免的问题 ,所以 ,人们开始研制人工骨修复材料。本文综述了生物陶瓷、胶原、脱钙骨、合成聚合物等骨修复材料的研究和应用现状。作者认为 ,将几类生物材料复合加工 ,研制出类似于人体骨组织的材料 ,将是今后骨修复材料的发展趋势     

Calculated beta-ray dose factors for trabecular bone.

Mean dose factors have been calculated for those tissues in bone that are relevant to the induction of late irradiation effects; namely, red bone marrow and endosteal tissues lining trabecular bone surfaces. The calculations are based on a Monte Carlo computer method for beta-emitting radionuclides which are distributed uniformly throughout the volume of mineralized bone. Results are given for the radionuclides 14C, 45Ca, 22Na, 18F, 32P, 90Y and 90Sr+90Y (all considered for this purpose as volume-seekers) for seven bones from the adult human skeleton and calculations are also presented of average skeletal dose factors. Where possible, results are compared with those derived from other methods based on simple geometrical models.     

脱细胞真皮基质修补腹股沟疝

背景：当前应用聚丙烯补片行腹股沟疝无张力修补已成为腹股沟疝修补的标准手段,但这些材料可能对患者生殖功能产生影响。 目的：总结应用脱细胞真皮基质修补腹股沟疝的经验。 方法：回顾性分析19例应用异体脱细胞真皮基质修补腹股沟疝患者的临床资料,男15例,女4例,年龄5~38岁。术后观察切口愈合情况,并定期随访。 结果与结论：19例患者伤口均Ⅰ期愈合,无切口感染、皮下积液等并发症。18例患者获得随访,随访3~30个月,无局部疼痛、牵拉等不适感,无复发病例。提示脱细胞真皮基质材料为未成年人、尚未婚育及有生育要求的男性腹股沟疝患者的治疗提供一种新的选择。     

Hyaline matrix in hyalinizing trabecular tumor

Hyalinizing trabecular tumor (HTT) is a rare neoplasm which usually follows an indolent clinical course. The cytologic diagnosis of HTT can be challenging as these neoplasms share cytomorphological features with other thyroid neoplasms and paraganglioma. In fine‐needle aspiration (FNA) smears a diagnosis of papillary thyroid carcinoma (PTC) or suspicion of PTC is often made. Herein we report cytologic findings in two patients with HTT examined by FNA. The key to a correct diagnosis is the recognition of a hyaline and colloid/amyloid‐like material in the background of the smears. Immunocytochemical examination showing aberrant membranous and peripheral cytoplasmic staining for MIB‐1 can help in rendering a correct diagnosis. Diagn. Cytopathol. 2015;43:710–713. © 2014 Wiley Periodicals, Inc.     

Porcine enamel matrix derivative enhances trabecular bone regeneration during wound healing of injured rat femur

To elucidate the effects of enamel matrix derivative (EMD: Emdogain®) on bone regeneration in rat femurs after drill‐hole injury, defects in bone were filled with either EMD or its carrier, PGA, as control. On postoperative days 4 to 28, dissected femurs were examined by means of various morphological approaches. In both experimental groups, formation of trabecular bone, which was immunostained for bone sialoproteins (BSP), had occurred in the medullary cavities at cylindrical bone defects on Day 7 postoperatively. Cuboidal osteoblasts were clearly observed on these newly‐formed BSP‐positive bone trabeculae. On Days 7 and 14, many multinucleated giant cells, which strongly expressed cathepsin K, had appeared on these bone trabeculae, indicating active bone remodeling. In these bone trabeculae, Ca and P weight % and Ca/P ratio were similar to those of cortical bone, and there was no significant difference between the PGA‐ and EMD‐applied groups. Bone volume fraction of newly‐formed bone trabeculae on Day 7 postoperatively was significantly higher in the EMD‐applied group than in the PGA‐applied controls. Because of active bone remodeling and the marked decrease of bone volume, on Days 14 and 28 postoperatively, however, there was no longer a significant difference in trabecular bone volume fraction between the experimental groups. Our results suggest that EMD possesses an osteo‐promotive effect on bone and medullary regeneration during wound healing of injured long bones. Anat Rec 264:438–446, 2001. © 2001 Wiley‐Liss, Inc.     

Micromechanical properties of human trabecular bone: a hierarchical investigation using nanoindentation

The ability to assess the risk of fracture, evaluate new therapies, predict implant success and assess the influence of bone remodeling disorders requires specific measurement of local bone micromechanical properties. Nanoindentation is an established tool for assessing the micromechanical properties of hard biological tissues. In this study, elastic modulus and hardness were quantified using nanoindentation for human trabecular bone from the intertrochanteric region of the proximal femur. These properties were demonstrated to be heterogeneous and highly correlated at the intraspicule, interspicule, and interspecimen levels. The results of this study have important implications for current understanding of structure-function relationships throughout the trabecular bone structural hierarchy.     

3D-printed poly(lactic acid) scaffolds for trabecular bone repair and regeneration: scaffold and native bone characterization

Purpose: Study objectives were set to (i) fabricate 3D-printed scaffolds/grafts with varying pore sizes, (ii) characterize surface and mechanical properties of scaffolds, (iii) characterize biomechanical properties of bovine trabecular bone, and (iv) evaluate attachment and proliferation of human bone marrow mesenchymal stem cells on 3D-printed scaffolds.

Materials and Methods: Poly(lactic acid) scaffolds were fabricated using 3D-printing technology, and characterized in terms of their surface as well as compressive mechanical properties. Trabecular bone specimens were obtained from bovine and characterized biomechanically under compression. Human bone marrow mesenchymal stem cells were seeded on the scaffolds, and their attachment capacity and proliferation were evaluated.

Results: Contact angles and compressive moduli of scaffolds decreased with increasing pore dimensions of 0.5 mm, 1.0 mm, and 1.25 mm. Biomechanical characterization of trabecular bone yielded higher modulus values as compared to scaffolds with all pore sizes studied. Human bone marrow mesenchymal stem cells attached to the surfaces of all scaffolds yet proliferated more on scaffolds with 1.25 mm pore size.

Conclusions: Collectively, given the similarity between 3D-printed scaffolds and native bone in terms of pore size, porosity, and appropriate mechanical properties of scaffolds, the 3D-printed poly(lactic acid) (PLA) scaffolds of this study appear as candidate substitutes for bone repair and regeneration.     

骨形成蛋白局部基因治疗在骨修复中的应用

骨形成蛋白(bonemorphogeneticproteins熏BMPs)是一组多功能的分泌性蛋白质,最主要的作用是在体内诱导异位和原位新骨、软骨及与骨组织有关的结缔组织如肌腱及韧带的形成,故可用于骨修复的局部基因治疗。本文简要介绍了目前BMP局部基因治疗在骨修复中的应用情况,包括所用的方法、载体、载体细胞及在动物模型中的疗效。另外,还简述了两个新发现的与BMP用于骨修复有关的转录因子:Cbfal和Osterix。