Mechanical Properties Of Cancellous Bone Research Articles

The speed of sound through trabecular bone predicted by Biot theory

Cancellous bone is a highly porous material filled with fluid. The mechanical properties of cancellous bone determine whether the bone is normal or osteoporotic. Wave propagation can be used to measure the elastic constants of cancellous bone. Recently, poroelasticity theory has been used to predict the elastic constants of cancellous bone from the wave velocities. In this study, it is shown that the fast wave, predicted by the Biot theory, corresponds to the wave penetrating the trabeculae, while the slow wave is determined by the interaction between the trabeculae and the fluid. The trabecular shape does not affect the wave velocity significantly when using the variable, which is determined by the microstructure, and the slow wave velocity decreases after the porosity reaches 80%.

MECHANICAL PROPERTIES OF A SINGLE CANCELLOUS BONE TRABECULAE TAKEN FROM BOVINE FEMUR

The increase of patients with osteoporosis is becoming a social problem, thus it is an urgent issue to find its prevention and treatment methods. Since cancellous bone is metabolically more active than cortical bone, cancellous bone is often used for diagnosis of osteoporosis and has received much attention within the study of bone. Bone is a hierarchically structured material and its mechanical properties vary at different structural levels, therefore it is important to break down the mechanical testing of bone according to the various levels within bone material. Mechanical properties of cancellous bone is said to be depended on quantities and orientation of trabecular bone. It is supposed that mechanical properties of trabecular bone are constant without depending on any structural arrangement and parts. However, such assumption has not been established in studies of trabecular bone. Furthermore test results have a large margin of error caused by insufficient shape assessment. In this study, three point bending tests of single cancellous bone trabeculae extracted from bovine femur were conducted to evaluate the effects of directions to the femur major axis direction on the mechanical properties. X-ray μCT was used to obtain shape of trabecular bone specimens. Furthermore compression tests of cancellous bone specimens, which were extracted in 10mm cubic geometry, were conducted for evaluation of directional properties.There were small difference in the elastic modulus of the trabecular bones which were extracted in parallel and in perpendicular to the major axis of femur. Considering from the results that the cancellous bone specimens, which were extracted in 10mm cubic geometry, have different elastic properties depending on the tested directions; the bone structure has larger influence than bone material property on the mechanical properties of cancellous bone.

Characterization of poly(3-hydroxybutyrate)/nano-hydroxyapatite composite scaffolds fabricated without the use of organic solvents for bone tissue engineering applications

Poly(3-hydroxybutyrate)/nano-hydroxyapatite (PHB/nHA) composite scaffolds were fabricated without the use of organic solvents at different mass fractions of HA nanoparticles. HA nanoparticles were homogeneously dispersed as primary particles in the polymer matrix of the scaffolds at 10 and 15wt.% nHA content. Agglomeration of HA nanoparticles occurred when the nHA content of the scaffolds reached 20wt.%. All the scaffolds had high porosities with interconnected porous structure and optimized pore size ranges. Mechanical properties of all the scaffolds were in the range of mechanical properties of cancellous bone. Scaffolds were biocompatible to MG-63 cells in the indirect method of cytotoxicity evaluation. Also, the morphology of the attached MG-63 cells in direct contact with the scaffolds indicated the appropriate cell–scaffold interaction. Thus, the PHB/nHA composite scaffolds investigated in this study tend to be favorable for bone tissue engineering applications.

Irradiation Does Not Modify Mechanical Properties of Cancellous Bone Under Compression

Gamma radiation sterilization can make cortical bone allograft more brittle, but whether it influences mechanical properties and propensity to form microscopic cracks in structurally intact cancellous bone allograft is unknown. We therefore determined the effects of gamma radiation sterilization on structurally intact cancellous bone mechanical properties and damage formation in both low- and high-density femoral cancellous bone (volume fraction 9%-44%). We studied 26 cancellous bone cores from the proximal and distal femurs of 10 human female cadavers (49-82 years of age) submitted to a single compressive load beyond yield. Mechanical properties and the formation of microscopic cracks and other tissue damage (identified through fluorochrome staining) were compared between irradiated and control specimens. We observed no alterations in mechanical properties with gamma radiation sterilization after taking into account variation in specimen porosity. No differences in microscopic tissue damage were observed between the groups. Although gamma radiation sterilization influences the mechanical properties and failure processes in cortical bone, it does not appear to influence the performance of cancellous bone under uniaxial loading.

Retraction Note to: Characteristics of porous zirconia coated with hydroxyapatite as human bones

Since hydroxyapatite has excellent biocompatibility and bone bonding ability, porous hydroxyapatite ceramics have been intensively studied. However, porous hydroxyapatite bodies are mechanically weak and brittle, which makes shaping and implantation difficult. One way to solve this problem is to introduce a strong porous network onto which hydroxyapatite coating is applied. In this study, porous zirconia and alumina-added zirconia ceramics were prepared by ceramic slurry infiltration of expanded polystyrene bead compacts, followed by firing at 1500°C. Then slurry of hydroxyapatite-borosilicate glass mixed powder was used to coat the porous ceramics, followed by firing at 1200°C. The porous structures without the coating had high porosities of 51–69%, high pore interconnectivity, and sufficiently large pore window sizes (300–500 μm). The porous ceramics had compressive strengths of 5·3∼36·8 MPa, favourably comparable to the mechanical properties of cancellous bones. In addition, porous hydroxyapatite surface was formed on the top of the composite coating, whereas a borosilicate glass layer was found on the interface. Thus, porous zirconia-based ceramics were modified with a bioactive composite coating for biomedical applications.

High performance additive manufactured scaffolds for bone tissue engineering application

This study demonstrates the feasibility of additive manufactured poly(3-caprolactone)/silanized tricalcium phosphate (PCL/TCP(Si)) scaffolds coated with carbonated hydroxyapatite (CHA)-gelatin composite for bone tissue engineering. In order to reinforce PCL/TCP scaffolds to match the mechanical properties of cancellous bone, TCP has been modified with 3-glycidoxypropyl trimethoxysilane (GPTMS) and incorporated into PCL to synthesize a PCL/TCP(Si) composite. The successful modification is confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis. Additive manufactured PCL/TCP(Si) scaffolds have been fabricated using a screw extrusion system (SES). Compression testing demonstrates that both the compressive modulus and compressive yield strength of the developed PCL/TCP(Si) scaffolds fall within the lower ranges of mechanical properties for cancellous bone, with a compressive modulus and compressive yield strength of 6.0 times and 2.3 times of those of PCL/TCP scaffolds, respectively. To enhance the osteoconductive property of the developed PCL/TCP(Si) scaffolds, a CHA-gelatin composite has been coated onto the scaffolds via a biomimetic co-precipitation process, which is verified by using scanning electron microscopy (SEM) and XPS. Confocal laser microscopy and SEM images reveal a most uniform distribution of porcine bone marrow stromal cells (BMSCs) and cellsheet accumulation on the CHA-gelatin composite coated PCL/TCP(Si) scaffolds. The proliferation rate of BMSCs on the CHA-gelatin composite coated PCL/TCP(Si) scaffolds is 2.0 and 1.4 times higher compared to PCL/TCP(Si) and CHA coated PCL/TCP(Si) scaffolds, respectively, by day 10. Furthermore, the reverse transcription polymerase chain reaction (RT-PCR) and western blot analyses reveal that CHA-gelatin composite coated PCL/TCP(Si) scaffolds stimulate osteogenic differentiation of BMSCs the most compared to the other scaffolds. In vitro results of SEM, confocal microscopy and proliferation rate also show that there is no detrimental effect of GPTMS modification on biocompatibility of the scaffolds.

Bioactive glass scaffold with similar structure and mechanical properties of cancellous bone

Natural bone is an amazing material because of its structure and mechanics. It is a challenge to find a bone substituted material mimicking natural bone intended to suffice for the need for bone repair and regeneration. In this study, a biomorphic material with similar structure and mechanical properties of cancellous bone has been fabricated by using demineralized cancellous bone as a template. Well-oriented particles in the pore walls could be observed clearly. The compressive strength of this scaffold was up to about 4.9 ± 0.2 MPa, close to the lower limit of the natural bone and 30 times of bioactive glass scaffolds, even though the porosity was up to 90%. This kind of bioactive glass composite scaffolds presented high resistance to deformation and showed an excellent shape restoration property. It is very close to a natural cancellous bone with a similar macro- and micro-structure and force-extension behavior. These results suggested this material would have a good potential in bone tissue engineering.

Synergetic effect of freeze-drying and gamma irradiation on the mechanical properties of human cancellous bone

Freeze-drying and irradiation are common process used by tissue banks to preserve and sterilize bone allografts. Freeze dried irradiated bone is known to be more brittle. Whether bone brittleness is due to irradiation alone, temperature during irradiation or to a synergetic effect of the freeze-drying-irradiation process was not yet assessed. Using a left-right femoral head symmetry model, 822 compression tests were performed to assess the influence of sequences of a 25kGy irradiation with and without freeze-drying compared to the unprocessed counterpart. Irradiation of frozen bone did not cause any significant reduction in ultimate strength, stiffness and work to failure. The addition of the freeze-drying process before or after irradiation resulted in a mean drop of 35 and 31% in ultimate strength, 14 and 37% in stiffness and 46 and 37% in work to failure. Unlike irradiation at room temperature, irradiation under dry ice of solvent-detergent treated bone seemed to have no detrimental effect on mechanical properties of cancellous bone. Freeze-drying bone without irradiation had no influence on mechanical parameters, but the addition of irradiation to the freeze-drying step or the reverse sequence showed a detrimental effect and supports the idea of a negative synergetic effect of both procedures. These findings may have important implications for bone banking.

A multiscale modeling approach to scaffold design and property prediction

The optimum scaffold architecture for bone tissue regeneration is a porous structure with a narrow range of pore sizes, pore density, and a high degree of interconnectivity among pores. To achieve such a design, the microstructure of the scaffold material must be optimized in order to satisfy both biological and mechanical function requirements. In this paper, we present a multiscale modeling approach for designing a scaffold with an optimized porosity and mechanical properties made from a two-phase composite of spherical hydroxyapatite (HAp) particles embedded in a collagen matrix. In particular, first-principles computation is used to calculate the elastic properties and theoretical strengths of nanoscaled HAp particles. The constitutive properties of the HAp/collagen composites are subsequently computed as a function of HAp content via FEM-based micromechanical modeling. The constitutive relations of the composite are then utilized to optimize the mechanical properties of a three-dimensional scaffold for either cortical or cancellous bone by varying the pore size, pore density and volume fractions of HAp in the composite. For the pore size, pore density, volume fractions of HAp considered, the scaffold can be designed to match the mechanical properties of cancellous bone, but not those of cortical bone. The optimized scaffold is one with a pore diameter of 1000 μm, a channel diameter of 100 μm, 27% pore density and at least 20% HAp by volume.

Mineral status and mechanical properties of cancellous bone exposed to hydrogen peroxide for various time periods

Processed cancellous bone has been regarded as one alternative for the treatment of bone defects. In order to avoid immunogenic effects and preserve the natural properties of the bone, the optimal processing method should be determined. To observe the influence of hydrogen peroxide on the mineral status and mechanical properties of cancellous bone for various time periods and find the optimal processing time. Cancellous bone granules from bovine femur condyles were treated with 30% hydrogen dioxide for 0, 12, 24, 36, 48, 60 and 72h separately. The microstructure and mineral content of the granules were evaluated by ash analysis, Micro-CT, scanning electron micrograph and energy dispersive X-ray. The biomechanical properties were analyzed by applying cranial-caudal compression in a materials testing machine. With increasing exposure to hydrogen peroxide, the BMD and BMC of granules gradually decreased, and the Ca/P molar ratios clearly increased (P<0.05). Meanwhile, the mineral content of the granules increased from 48.5 ±1.3 to 79.5±2.1%. Substantial decreases in the strength of the granules were observed, and after 48h severe decreases were noted. The decrease in strength was also evident after normalizing the parameters to the cross-sectional area. Granules of bovine cancellous bone matrix should be processed by hydrogen peroxide for 12 to 36h to fulfill the basic requirements of a bone tissue engineering scaffold. These granules could potentially be useful during orthopedic operations.

Simulation of ultrasonic wave propagation in anisotropic cancellous bone immersed in fluid

Cancellous bone at the macroscopic level is known as being a two-phase anisotropic material composed of a solid rod-like or plate-like skeleton filled with viscous fluid. Quantifying the mechanical properties of cancellous bones by using ultrasound techniques should take into account these complexities. This paper proposes a model to investigate the transient ultrasonic wave propagation in a cancellous bone immersed in an acoustic fluid. A finite element time-domain model based on u s - w formulation is developed to consider an anisotropic porous medium (Biot’s model) coupled with two acoustic fluids. Some numerical results are shown to illustrate the influence of the bone anisotropy to the reflection and transmission of plane waves in a human cancellous bone specimen.

OS1002 海綿骨の微視・巨視機械特性評価のためのトラス有限要素解析法の開発(生体と材料力学,オーガナイズドセッション)

OS1002 海綿骨の微視・巨視機械特性評価のためのトラス有限要素解析法の開発(生体と材料力学,オーガナイズドセッション)

MECHANICAL PROPERTIES OF GLENOID CANCELLOUS BONE

Total shoulder arthroplasty is a well-established and widely accepted method of treatment for a variety of shoulder disorders, loosening of the glenoid prosthesis is the main complication in total shoulder arthroplasty, it is highly dependent on the quality of the glenoid cancellous bone. Very little is known about mechanical properties of this cancellous bone. The objectives of this study were to determine the mechanical properties (elastic modulus and strength) of glenoid cancellous bone in the axial, coronal and sagittal planes including regional variation using a uniaxial compression test. To our knowledge, this kind of study was not done before. Eleven scapulas were obtained from six fresh-frozen, unembalmed human cadavers (mean age eighty-eight years). Eighty-two cubic cancellous bone specimens of 6×6×6mm3 were used for mechanical testing in the three planes. The test was a uniaxial compression along each direction, Elastic modulus and strength were determined from the stress-strain curve. Apparent density was also calculated. The study showed significant differences in the mechanical properties with anatomic location and directions of loading. Young modulus and strength were found to be significantly higher at the posterior part of the glenoid with the weakest properties at the antero-inferior part. Cancellous bone was found to be anisotropic with higher mechanical properties in the latero-medial direction (perpendicular to the articular surface of the glenoid). The apparent density was on average equal to 0.29 g/cm3 with the higher values at the posterior and superior part of the glenoid. Good correlation between apparent density and elastic modulus was found only in the sagittal plane but not in the coronal and axial plane, the overall correlation was low (r2 = 0.22, p The mechanical properties determined in this study provide input data for finite element method analyses and may help to assist in uncemented shoulder prosthesis design.

Effect of ovariectomy on BMD, micro-architecture and biomechanics of cortical and cancellous bones in a sheep model

Osteoporotic/osteopenia fractures occur most frequently in trabeculae-rich skeletal sites. The purpose of this study was to use a high-resolution micro-computed tomography (micro-CT) and dual energy X-ray absorptionmeter (DEXA) to investigate the changes in micro-architecture and bone mineral density (BMD) in a sheep model resulted from ovariectomy (OVX). Biomechanical tests were performed to evaluate the strength of the trabecular bone. Twenty adult sheeps were randomly divided into three groups: sham group ( n = 8), group 1 ( n = 4) and group 2 ( n = 8). In groups 1 and 2, all sheep were ovariectomized (OVX); in the sham group, the ovaries were located and the oviducts were ligated. In all animals, BMD for lumbar spine was obtained during the surgical procedure. BMD at the spine, femoral neck and femoral condyle was determined 6 months (group 1) and 12 months (group 2) post-OVX. Lumbar spines and femora were obtained and underwent BMD scan, micro-CT analysis. Compressive mechanical properties were determined from biopsies of vertebral bodies and femoral condyles. BMD, micro-architectural parameters and mechanical properties of cancellous bone did not decrease significantly at 6 months post-OVX. Twelve months after OVX, BMD, micro-architectural parameters and mechanical properties decreased significantly. The results of linear regression analyses showed that trabecular thickness (Tb.Th) ( r = 0.945, R 2 = 0.886) and bone volume fraction (BV/TV) ( r = 0.783, R 2 = 0.586) had strong ( R 2 > 0.5) correlation to compression stress. In OVX sheep, changes in the structural parameters of trabecular bone are comparable to the human situation during osteoporosis was induced. The sheep model presented seems to meet the criteria for an osteopenia model for fracture treatment with respect to morphometric and mechanical properties. But the duration of OVX must be longer than 12 months to ensure the animal model can be established successfully.

RETRACTED ARTICLE: Characteristics of porous zirconia coated with hydroxyapatite as human bones

Since hydroxyapatite has excellent biocompatibility and bone bonding ability, porous hydroxyapatite ceramics have been intensively studied. However, porous hydroxyapatite bodies are mechanically weak and brittle, which makes shaping and implantation difficult. One way to solve this problem is to introduce a strong porous network onto which hydroxyapatite coating is applied. In this study, porous zirconia and alumina-added zirconia ceramics were prepared by ceramic slurry infiltration of expanded polystyrene bead compacts, followed by firing at 1500°C. Then slurry of hydroxyapatite-borosilicate glass mixed powder was used to coat the porous ceramics, followed by firing at 1200°C. The porous structures without the coating had high porosities of 51–69%, high pore interconnectivity, and sufficiently large pore window sizes (300–500 μm). The porous ceramics had compressive strengths of 5·3∼36·8 MPa, favourably comparable to the mechanical properties of cancellous bones. In addition, porous hydroxyapatite surface was formed on the top of the composite coating, whereas a borosilicate glass layer was found on the interface. Thus, porous zirconia-based ceramics were modified with a bioactive composite coating for biomedical applications.

Effects of non-enzymatic glycation on cancellous bone fragility

Post-translational modifications of collagen, such as non-enzymatic glycation (NEG), occur through the presence of extracellular sugars and cause the formation of advanced glycation end-products (AGEs). While AGEs have been shown to accumulate in a variety of collagenous human tissues and alter the tissues' functional behavior, the role of AGEs in modifying the mechanical properties of cancellous bone is not well understood. In this study, an in vitro ribosylation model was used to examine the effect of NEG on the mechanical behavior of cancellous bone. Cancellous bone cores and individual trabeculae were harvested from the femoral heads of eight fresh human cadavers and paired for ribosylation and control treatments. The cores were subjected to either unconfined compression tests or were demineralized and subjected to stress relaxation tests. The trabeculae were loaded to fracture in four-point bending. In vitro NEG significantly reduced the energy dissipation characteristics of the organic matrix as well as the post-yield properties including the stiffness loss of the individual trabeculae ( p < 0.05) and the damage fraction of cancellous bone ( p < 0.001). AGEs in cancellous bone cores from both treatment groups correlated with damage fraction ( r 2 = 0.36, p < 0.05) and post-yield strain energy ( r 2 = 0.21, p < 0.05); and with energy dissipation characteristics of the organic matrix ( r 2 = 0.35, p < 0.05). In the control group, AGEs content increased up to six-fold with age ( r 2 = 0.95, p < 0.008). This study shows that cancellous bone is susceptible to NEG that increases its propensity to fracture. Moreover, despite tissue turnover, cancellous bone may be susceptible to an age-related accumulation of AGEs.

A method for patient-specific evaluation of vertebral cancellous bone strength: In vitro validation

In the context of osteoporosis, important determinants of the fracture risk are the apparent strength and stiffness of cancellous bone, as well as its brittleness and energy absorption capacity. Standard medical imaging, however, cannot measure these mechanical properties directly. Consequently, an estimation of the risk for fracture is made by correlating relative density or mineral density at a skeletal site with statistics of fracture occurrence, which provides limited and partial indications on fracture risks. A better method for evaluating the patient-specific mechanical properties of cancellous bone is therefore required. In order to asses the mechanical properties of vertebral cancellous bone, we developed a finite element parametric model of lattice trabecular architecture that, in the future, will be suitable for use with bone imaging modalities. The model inputs are apparent morphological parameters (trabecular thickness and trabecular separation) and the bone mineral density. We conducted uniaxial compression tests on 36 canine vertebral cancellous bone specimens (C7 and L1) to validate model predictions of strength and stiffness in vitro. Predictions of strength and stiffness matched the experimental results within relative absolute errors of 17.7% and 12.8%, respectively (average of differences between model-predicted and measured values, divided by the average of measured values). We also employed the model for evaluation of strength and stiffness of human L1 and L5 vertebrae and found mean strength of 1.67 MPa (confidence interval 0.42 MPa) and mean elastic modulus of 190 MPa (confidence interval 50 MPa), which are well within the range of previously reported apparent strength and stiffness properties. The present model can be used to improve medical imaging-based evaluation of the spine in osteoporotic individuals by providing more specific information on the individual bone's susceptibility to fracture once clinical bone scans will be able to provide more reliable measures of trabecular thickness and separation.

First clinical and biomechanical results of the Trochanteric Fixation Nail (TFN)

Conventional osteosynthesis of proximal femur fractures is still affected by serious complication rates between 4-18%, even though advanced implant modifications and surgical techniques are common practice. In terms of increasing age and co-morbidity of patients this complication ratio is expected to increase even further in the immediate future. One major reason for implant failure is the decreasing stability potential of the implant due to a loss in mechanical properties of cancellous bone. Therefore, efforts in new intramedulary techniques specifically focus on the load bearing characteristics of the implant by developing new geometries to improve the implant-tissue interface. This investigation discusses first clinical results of the trochanteric fixation nail TFN (145 patients) and a biomechanical analysis of the blade/femur head interaction under different static loading conditions. The TFN shows promising performance in first clinical results. In the clinical study the overall complication rate was significantly lower compared to other similar osteosynthesis. For the investigation of the biomechanical stability of the helical TFN blade the following experiments were performed: Analysis of the axial load required for insertion of the blade by free rotation; measurement of the corresponding rotation angle for total insertion (32 mm) (n = 8); pull-out forces with suppressed rotation (n = 4); loads for rotational overwinding of the implant in the fully inserted condition (n = 4). All investigations were performed on human femoral heads. The bone mineral densities of the specimens were detected by QCT-scans. Prior to cadaveric testing the experimental set-up was validated (n = 8) by the use of synthetic foam blocks (Sawbone).

O.279 Treatment of open bite after mandibular condyle fractures using a new orthognatic spring device

Objective. To investigate the influence of decreased mechanical loading on the density and mechanical properties of the cancellous bone of the human mandibular condyle.Design. Destructive compressive mechanical tests were performed on cancellous bone specimens.Background. Reduced masticatory function in edentate people leads to a reduction of forces acting on the mandible. As bone reacts to its mechanical environment a change in its material properties can be expected.Methods. Cylindrical bone specimens were obtained from dentate and edentate embalmed cadavers. Mechanical parameters were determined in the axial and in the transverse directions. Subsequently, density parameters were determined according to a method based on Archimedes’ principle.Results. The apparent density and volume fraction of the bone were about 18% lower in the edentate group; no age-related effect on density was found. The decrease of bone in the edentate group was associated with a lower stiffness and strength (about 22% and 28%, respectively). The ultimate strain, however, did not differ between the two groups. Both groups had similar mechanical anisotropy; in axial loading the bone was stiffer and stronger than in transverse loading.Conclusions. Reduced mechanical load had affected the density and herewith the mechanical properties of condylar cancellous bone, but not its anisotropy.Relevance The change in material properties of the cancellous bone after loss of teeth indicate that the mandibular condyle is sensitive for changes in its mechanical environment. Therefore, changes in mechanical loading of the condyle have to be accounted for in surgical procedures of the mandible.

Hydroxyapatite coating on porous zirconia

Since hydroxyapatite has excellent biocompatibility and bone bonding ability, porous hydroxyapatite ceramics have been intensively studied. However, porous hydroxyapatite bodies are mechanically weak and brittle, which makes shaping and implantation difficult. One way to solve this problem is to introduce a strong porous network onto which hydroxyapatite coating is applied. In this study, porous zirconia and alumina-added zirconia ceramics were prepared by ceramic slurry infiltration of expanded polystyrene bead compacts, followed by firing at 1500 °C. Then a slurry of hydroxyapatite–borosilicate glass mixed powder was used to coat the porous ceramics, followed by firing at 1200 °C. The porous structures without the coating had high porosities of 51% to 69%, a high pore interconnectivity, and sufficiently large pore window sizes (300 μm–500 μm). The porous ceramics had compressive strengths of 5.3˜36.8 MPa and Young's moduli of 0.30˜2.25 GPa, favorably comparable to the mechanical properties of cancellous bones. In addition, porous hydroxyapatite surface was formed on the top of the composite coating, whereas a borosilicate glass layer was found on the interface. Thus, porous zirconia-based ceramics were modified with a bioactive composite coating for biomedical applications.