Bovine Trabecular Bone Research Articles

Enhancing polymeric bone scaffolds mechanical characteristics using supercritical CO2 foaming and reinforcing agents

BackgroundAs an alternative to conventional medicine, scaffolds have emerged to mimic and/or replace damaged tissue. 3D porous matrix scaffolds made of biodegradable and biocompatible polymers, including PLGA, have proven to be of particular interest for use as bone substitutes in Tissue Engineering. MethodsThe study used high-pressure CO2 foaming to produce PLGA-based foams. Previously, melt-extrusion was used to introduce reinforcement agents, Mg(OH)2, Hydroxyapatite (HAp) and Mg, to achieve foams with improved properties. Foam morphology was analysed using SEM, EDS, and 3D scanner techniques, and foam strength was measured using compression tests. A statistical analysis was carried out to study the effect of pressure and temperature on foams pore size and hardness. Significant findingsThe foams produced were rigid, non-sticky and time-stable, and showed high porosity. The pressure was found to be the only significant variable to tune both porosity and cell densities of scaffolds. Setting a pore size at 500 μm, compressive stresses of 1.85 MPa, 3.81 MPa were achieved for Mg(OH)2 and HAp, respectively. Those results were comparable to literature´s trabecular bovine bone compression resistance of 4.2 MPa. This finding indicated the possibility of getting, at the same time, convenient results for porosity and mechanical resistance for their use as bone replacement agents. Finally, a 20 % w/w ratio of reinforcing agent was found to produce the best pore size-stress ratio.

High strain rate response of ABS-M30i-based 3D printed, bio-inspired, bovine bone structure

To investigate osteoporosis caused by aging and the dynamic behavior of male bovine trabecular bone, three age groups of male bovine trabecular bone were chosen, and micro-computed tomography (CT) analysis was performed to develop an image-based bio-inspired computer-aided design (CAD) model of the bone structure. Further experimental and computational studies were carried out to examine the rate-dependent behavior and compressive energy-absorbing capacity of the structure as a function of age. To evaluate this study, a micro-CT-based CAD model of the structure was 3D printed using ABS-M30i material and subjected to quasi-static compression (low strain rate) and high strain rate (split Hopkinson pressure bar) compression. The findings show that 3D-printed bovine structures have distinct high-rate dependence at strain rates greater than 430 s−1, as well as sensitivity to strain rate in terms of peak stress, plateau stress, and energy absorption capacity. Using rate-dependent properties, the Johnson–Cook damage plasticity model was used in computational analysis to explain the dynamic behavior of bone due to osteoporosis. Overall, there is good agreement between the numerical simulations and the experimental data, which was obtained by verifying and validating the model against the experimental results.

Electrical Impedance Spectroscopy as a Potential Tool for Detecting Bone Porosity

Electrical measurements of bovine trabecular bone samples revealed a perfect correlation between the electrical and mechanical properties. Electrical parameters have surpassed Broadband Ultrasound Attenuation measurements to predict the mechanical properties of bovine bones. There is a linear relationship between dielectric permittivity and bone mineral density. Studies utilizing electrical impedance spectroscopy to evaluate bone include the characterization and monitoring of titanium bone implants, the characterization of bone tissue, and the monitoring of bone fracture healing progress after osteosynthesis. These studies demonstrate that impedance spectroscopy has outstanding potential for assessing bone quality. This study proposes electrical impedance as a method for characterizing bone porosity. Using the DAQ Analog Discovery as an EIS, two electrodes were utilized to determine bone porosity. The procedures include the EIS scanning process and the analysis of its electrical components using the CPE(RC) circuit model. Five bovine samples were used to demonstrate that the EIS spectrum method can be used to determine bone porosity with a reasonable correlation between the parameters R (R2=0.987, F(1,3)=68.067, p<0.004). and C (R2=0.994, F(1,3)=94.041, p<0.002). While the parameter Q (R2=0.922, F(1,3)=22.568, p<0.018) of CPE can indicate the condition of the bovine cancellous bone scaffold surface.

Quantification of long-term nonlinear stress relaxation of bovine trabecular bone

The reliability of computational models in orthopedic biomechanics depends often on the accuracy of the bone material properties. It is widely recognized that the mechanical response of trabecular bone is time-dependent, yet it is often ignored for the sake of simplicity. Previous investigations into the viscoelastic properties of trabecular bone have not explored the relationship between nonlinear stress relaxation and bone mineral density. The inclusion of this behavior could enhance the accuracy of simulations of orthopedic interventions, such as of primary fixation of implants. Although methods to quantify the viscoelastic behavior are known, the time period during which the viscoelastic properties should be investigated to obtain reliable predictions is currently unclear. Therefore, this study aimed to: 1) Investigate the duration of stress relaxation in bovine trabecular bone; 2) construct a material model that describes the nonlinear viscoelastic behavior of uniaxial stress relaxation experiments on trabecular bone; and 3) implement bone density into this model. Uniaxial compressive stress relaxation experiments were performed with cylindrical bovine femoral trabecular bone samples (n = 16) with constant strain held for 24 h. Additionally, multiple stress relaxation experiments with four ascending strain levels with a holding time of 30 min, based on the results of the 24-h experiment, were executed on 18 bovine bone cores. The bone specimens used in this study had a mean diameter of 12.80 mm and a mean height of 28.70 mm. A Schapery and a Superposition model were used to capture the nonlinear stress relaxation behavior in terms of applied strain level and bone mineral density. While most stress relaxation happened in the first 10 min (up to 53 %) after initial compression, the stress relaxation continued even after 24 h. Up to 69 % of stress relaxation was observed at 24 h. Extrapolating the results of 30 min of experimental data to 24 h provided a good fit for accuracy with much improved experimental efficiency. The Schapery and Superposition model were both capable of fitting the repeated stress relaxation in a sample-by-sample approach. However, since bone mineral density did not influence the time-dependent behavior, only the Superposition model could be used for a group-based model fit. Although the sample-by-sample approach was more accurate for an individual specimen, the group based approach is considered a useful model for general application.

Adaptable test bench for ASTM-compliant permeability measurement of porous scaffolds for tissue engineering

Intrinsic permeability describes the ability of a porous medium to be penetrated by a fluid. Considering porous scaffolds for tissue engineering (TE) applications, this macroscopic variable can strongly influence the transport of oxygen and nutrients, the cell seeding process, and the transmission of fluid forces to the cells, playing a crucial role in determining scaffold efficacy. Thus, accurately measuring the permeability of porous scaffolds could represent an essential step in their optimization process. In literature, several methods have been proposed to characterize scaffold permeability. Most of the currently adopted approaches to assess permeability limit their applicability to specific scaffold structures, hampering protocols standardization, and ultimately leading to incomparable results among different laboratories. The content of novelty of this study is in the proposal of an adaptable test bench and in defining a specific testing protocol, compliant with the ASTM International F2952-22 guidelines, for reliable and repeatable measurements of the intrinsic permeability of TE porous scaffolds. The developed permeability test bench (PTB) exploits the pump-based method, and it is composed of a modular permeability chamber integrated within a closed-loop hydraulic circuit, which includes a peristaltic pump and pressure sensors, recirculating demineralized water. A specific testing protocol was defined for characterizing the pressure drop associated with the scaffold under test, while minimizing the effects of uncertainty sources. To assess the operational capabilities and performance of the proposed test bench, permeability measurements were conducted on PLA scaffolds with regular (PS) and random (RS) micro-architecture and on commercial bovine bone matrix-derived scaffolds (CS) for bone TE. To validate the proposed approach, the scaffolds were as well characterized using an alternative test bench (ATB) based on acoustic measurements, implementing a blind randomized testing procedure. The consistency of the permeability values measured using both the test benches demonstrated the reliability of the proposed approach. A further validation of the PTB’s measurement reliability was provided by the agreement between the measured permeability values of the PS scaffolds and the theory-based predicted permeability value. Once validated the proposed PTB, the performed measurements allowed the investigation of the scaffolds’ transport properties. Samples with the same structure (guaranteed by the fused-deposition modeling technique) were characterized by similar permeability values, and CS and RS scaffolds showed permeability values in agreement with the values reported in the literature for bovine trabecular bone. In conclusion, the developed PTB and the proposed testing protocol allow the characterization of the intrinsic permeability of porous scaffolds of different types and dimensions under controlled flow regimes, representing a powerful tool in view of providing a reliable and repeatable framework for characterizing and optimizing scaffolds for TE applications.

The effect of temperature on the physical-chemical properties of bovine hydroxyapatite biomimetic scaffolds for bone tissue engineering

This work focuses on the changes in hydroxyapatite (HAp) scaffolds obtained from bovine trabecular bone after heat treatments ranging from 400 to 1100 °C. The main objective is to gain a comprehensive understanding of the thermal behavior and structural modifications of these HAp scaffolds and evaluate their suitability for specific applications.Thermal analysis using thermogravimetry and differential scanning calorimetry revealed distinct thermal events associated with HAp crystallite coalescence, carbonate elimination, and Mg out-diffusion. Fourier transform infrared spectroscopy demonstrates the presence of organics in samples annealed at temperatures below 500 °C and the elimination of carbonates in samples annealed at temperatures above 700 °C.Raman spectroscopy indicated a transition from nano-to-micro-sized HAp crystallites in both the raw and samples annealed at 400 and 500 °C. X-ray diffraction analysis shows changes in the full width at half maximum (FWHM) of the (002) peak for the annealed samples. Crystalline parameters were determined using Rietveld refinement. Scanning electron microscopy images revealed the phenomenon of HAp crystallite coalescence during heat treatment. The growth of the crystallites and the transition from nano to micro size occurred at approximately 600 °C.Importantly, the macroporosity of the HAp scaffolds remained unchanged regardless of the calcination temperature, while mesoporosity was observed only in scaffolds calcined at lower temperatures (400, 500, and 600 °C). Furthermore, the raw, 400, and 500 °C scaffolds retained organic materials, resulting in improved mechanical properties.These findings provide valuable insights into the thermal behavior and structural changes of HAp scaffolds derived from bovine trabecular bone. The study suggests that scaffolds calcined at 600 °C exhibit suitable properties for bone tissue engineering applications, predominantly consisting of carbonated HAp nanocrystals, featuring three types of porosity, and are free of organic material.

Using an Instrumented Hammer to Predict the Rupture of Bone Samples Subject to an Osteotomy.

Osteotomies are common procedures in maxillofacial and orthopedic surgery. The surgeons still rely on their proprioception to control the progression of the osteotome. Our group has developed an instrumented hammer that was shown to provide information on the biomechanical properties of the tissue located around the osteotome tip. The objective of this study is to determine if this approach may be used to predict the rupture of a bone sample thanks to an instrumented hammer equipped with a force sensor. For each impact, an indicator τ is extracted from the signal corresponding to the variation of the force as a function of time. A linear by part regression analysis is applied to the curve corresponding to the variation of τ as a function of the distance d between the tip of the osteotome and the end of the sample. The experiments were conducted with plywood and bovine trabecular bone samples. The results show that τ starts increasing when the value of d is lower than 2.6 mm on average, which therefore corresponds to a typical threshold detection distance between the osteotome tip and the sample end. These findings open new paths for the development of this instrumented surgical hammer.

Segmentation of trabecular bone microdamage in Xray microCT images using a two-step deep learning method

IntroductionOne of the current approaches to improve our understanding of osteoporosis is to study the development of bone microdamage under mechanical loading. The current practice for evaluating bone microdamage is to quantify damage volume from images of bone samples stained with a contrast agent, often composed of toxic heavy metals and requiring long tissue preparation. This work aims to evaluate the potential of linear microcracks detection and segmentation in trabecular bone samples using well-known deep learning models, namely YOLOv4 and Unet, applied on microCT images. MethodsSix trabecular bovine bone cylinders underwent compression until ultimate stress and were subsequently imaged with a microCT at a resolution of 1.95 μm. Two of these samples (samples 1 and 2) were then stained using barium sulfate (BaSO4) and imaged again. The unstained samples (samples 3–6) were used to train two neural networks YOLOv4 to detect regions with microdamage further combined with Unet to segment the microdamage at the pixel level in the detected regions. Four different model versions of YOLOv4 were compared using the average Intersection over Union (IoU) and the mean average precision (mAP). The performance of Unet was also measured using two segmentation metrics, the Dice Score and the Intersection over Union (IoU). A qualitative comparison was finally done between the deep learning and the contrast agent approaches. ResultsAmong the four versions of YOLOv4, the YOLOv4p5 model resulted in the best performance with an average IoU of 45,32% and 51,12% and a mAP of 28.79% and 46.22%, respectively for samples 1 and 2. The segmentation performance of Unet provided better IoU and DICE score on sample 2 compared to sample 1. The poorer performance of the test on sample 1 could be explained by its poorer contrast to noise ratio (CNR). Indeed, sample 1 resulted in a CNR of 7,96, which was worse than the average CNR in the training samples, while sample 2 resulted in a CNR of 10,08. The qualitative comparison between the contrast agent and the deep learning segmentation showed that two different regions were segmented by the two techniques. Deep learning is segmenting the region inside the cracks while the contrast agent segments the region around it or even regions with no visible damage. ConclusionThe combination of YOLOv4 for microdamage detection with Unet for damage segmentation showed a potential for the detection and segmentation of microdamage in trabecular bone. The accuracy of both neural networks achieved in this work is acceptable considering it is their first application in this specific field and the amount of data was limited. Even if the errors from both neural networks are accumulated, the two-steps approach is faster than the semantic segmentation of the whole volume.

Optical bone densitometry insensitive to skin thickness.

Skin thickness, including the adipose layer, which varies from individual to individual, affects the bone density measurement using light. In this study, we proposed a method to measure skin thickness using light and to correct the bias caused by differences in skin thickness and verified the proposed method by experiments using a phantom. We measured simulated skin of different thicknesses and bovine trabecular bone of different bone mineral densities (BMDs) using an optical system consisting of lasers of 850 and 515nm wavelengths, lenses, and slits. Although the slope of the light intensity distribution formed on the surface of the material when irradiated by the 850nm laser is affected by the thickness of the skin phantom. The difference of the intensity distribution peaks (δy) between the 850 and 515nm lasers was strongly correlated with the thickness of the skin phantom. The coefficient of determination between the measurements and the BMD was improved by correcting the 850nm laser measurements with δy. This result suggests that the method is applicable to optical bone densitometry, which is insensitive to differences in skin thickness.

Osteogenic Effect of Fisetin Doping in Bioactive Glass/Poly(caprolactone) Hybrid Scaffolds.

Treating large bone defects or fragile patients may require enhancing the bone regeneration rate to overcome a weak contribution from the body. This work investigates the osteogenic potential of nutrient fisetin, a flavonoid found in fruits and vegetables, as a doping agent inside the structure of a SiO2–CaO bioactive glass–poly(caprolactone) (BG–PCL) hybrid scaffold. Embedded in the full mass of the BG–PCL hybrid during one-pot synthesis, we demonstrate fisetin to be delivered sustainably; the release follows a first-order kinetics with active fisetin concentration being delivered for more than 1 month (36 days). The biological effect of BG–PCL–fisetin-doped scaffolds (BG–PCL–Fis) has been highlighted by in vitro and in vivo studies. A positive impact is demonstrated on the adhesion and the differentiation of rat primary osteoblasts, without an adverse cytotoxic effect. Implantation in critical-size mouse calvaria defects shows bone remodeling characteristics and remarkable enhancement of bone regeneration for fisetin-doped scaffolds, with the regenerated bone volume being twofold that of nondoped scaffolds and fourfold that of a commercial trabecular bovine bone substitute. Such highly bioactive materials could stand as competitive alternative strategies involving biomaterials loaded with growth factors, the use of the latter being the subject of growing concerns.

The Hydration State of Bone Tissue Affects Contrast in Neutron Tomographic Images.

Neutron tomography has emerged as a promising imaging technique for specific applications in bone research. Neutrons have a strong interaction with hydrogen, which is abundant in biological tissues, and they can penetrate through dense materials such as metallic implants. However, in addition to long imaging times, two factors have led to challenges in running in situ mechanical characterization experiments on bone tissue using neutron tomography: 1) the high water content in specimens reduces the visibility of internal trabecular structures; 2) the mechanical properties of bone are dependent on the hydration state of the tissue, with drying being reported to cause increased stiffness and brittleness. This study investigates the possibility of improving image quality in terms of neutron transmission and contrast between material phases by drying and rehydrating in heavy water. Rat tibiae and trabecular bovine bone plugs were imaged with neutron tomography at different hydration states and mechanical testing of the bone plugs was carried out to assess effects of drying and rehydration on the mechanical properties of bone. From analysis of image histograms, it was found that drying reduced the contrast between bone and soft tissue, but the contrast was restored with rehydration. Contrast-to-noise ratios and line profiles revealed that the contrast between bone tissue and background was reduced with increasing rehydration duration but remained sufficient for identifying internal structures as long as no free liquid was present inside the specimen. The mechanical analysis indicated that the proposed fluid exchange protocol had no adverse effects on the mechanical properties.

Comparing the Effects of Alpha-Tocopherol and Tocotrienol Isomers on Osteoblasts hFOB 1.19 Cultured on Bovine Bone Scaffold

Tocotrienol mixtures have been shown to exert anabolic actions on the skeletal system in animal studies, but it is unclear which tocotrienol isomer shows the most prominent effects. This study aims to investigate the most active tocotrienol isomers using hFOB 1.19 human osteoblasts cultured on a bovine bone scaffold. The bovine trabecular bone was sectioned, demineralised and freeze-dried to form the scaffold. hFOB 1.19 osteoblasts were cultured on the bone scaffolds in humidified condition at 37 °C and 5% carbon dioxide with vitamin E isomers (alpha-, beta-, gamma-, delta-tocotrienol and alpha-tocopherol). The cell differentiation capacity of tocotrienol isomers was investigated through morphological observation, alkaline phosphatase (ALP) activity and osteocalcin expression. Changes in the bone scaffolds were determined using histomorphometry methods. Osteoblast culture treated with gamma- and delta-tocotrienols showed a significant increase in ALP activity and osteocalcin expression. Bone structural histomorphometry analysis showed that bone scaffolds treated with gamma- and delta-tocotrienol showed significant increases in bone volume and trabecular thickness. In conclusion, gamma- and delta-tocotrienol show the most prominent bone anabolic effects by increasing osteoblast differentiation and enhancing bone microstructure.

Physicochemical properties of 3D bovine natural scaffolds as a function of the anterior-posterior, lateral and superior-inferior directions

Bovine trabecular bone (BTB) is a hydroxyapatite (HAp) source for bone regeneration due to its high metabolic activity inside the human body. In this work, the physicochemical properties of BTB raw, defatted-deproteinized, and incinerate (580 °C) cubic pieces (1 × 1 × 1 cm) were analyzed as a function of the anatomical directions. In these natural scaffolds, Inductively Coupled Plasma (ICP) showed the presence of Na, Mg, Zn, and K as minority ions. Scanning Electron Microscopy (SEM) shows that BTB is anisotropic, and X-ray patterns showed hydroxyapatite nanocrystals with preferred orientation in the superior-inferior axis. Micro–Computed Tomography allowed 3D reconstruction of a BTB cube and calculate the areal bone mineral density (aBMD) in Pixel/cm2, which is around 70%. aBMD exhibits an inversely proportional behavior to the porosity of the samples. BTB cubes present higher Young's modulus for the Z-direction than the X- and Y-direction, regardless of their pretreatment. This finding confirms that the mechanical properties of the scaffolds are governed by the crystalline structure, morphology, and spatial distribution of the hydroxyapatite nanocrystals. Infrared analysis showed the presence of carbonate.

Physicochemical Properties of 3D Bovine Natural Scaffolds as a Function of the Direction

Bovine trabecular bone (BTB) is a source for obtaining hydroxyapatite for bone regeneration due to its high metabolic activity inside the human body. In this work, the physicochemical properties of BTB defatted and deproteinized cubic pieces (1 cm x 1cm x 1 cm) defatted and deproteinized as well as incinerated at 580 °C were analyzed in order to determine the characteristics that any scaffold for bone regeneration must-have. SEM images evidenced its complex interconnected macrostructure, and X-ray patterns showed hydroxyapatite nanocrystals with preferred orientation. 2D radiographs allowed to reconstruct 3D images of a BTB cube and determine that the aBMD exhibits an inversely proportional behavior to the porosity of the samples. BTB cubes present higher Young's moduli for the Z-direction than the X- and Y-direction, regardless of the pretreatment that the samples received. This finding confirms that the mechanical properties of the scaffolds are governed by the crystalline structure, morphology, and spatial distribution of the BTB, which constitute the macrostructure of the bone.

Explicit finite element analysis can predict the mechanical response of conical implant press-fit in homogenized trabecular bone

Prediction of primary stability is a major challenge in the surgical planning of dental and orthopedic implants. Computational methods become attractive to estimate primary stability from clinical CT images, but implicit finite element analysis of implant press-fit faces convergence issues due to contact and highly distorted elements. This study aims to develop and validate an explicit finite element method to simulate the insertion and primary stability of a rigid implant in a deformable bone while accounting for damage occurring at the bone-implant interface. Accordingly, a press-fit experiment of a conical implant into predrilled bovine trabecular bone was designed and realized for six samples. A displacement-driven cyclic protocol was used to quantify the reaction force and stiffness of the bone-implant system. Homogenized finite element analyses of the experiments were performed by modeling contact with friction and converting an existing constitutive model with elasto-plasticity and damage of bone tissue to be applicable to an explicit time integration scheme where highly distorted elements get deleted. The computed reaction forces and unloading stiffnesses showed high correlations (R2 = 0.95 and R2 = 0.94) with the experiment. Friction between bone and implant exhibited a strong influence on both reaction force and stiffness. In conclusion, the developed explicit finite element approach with frictional contact and element deletion accounts properly for bone damage during press-fit and will help optimizing dental or orthopedic implant design towards maximal primary stability.

Post-yield mechanical properties of bovine trabecular bone – Relationships with bone volume fraction and strain rate

Bone finite element models, which are increasingly used to assess fracture risk in patients with degenerative bone diseases, require extensive experimental data to adequately model the material properties being assigned. Previous studies have demonstrated that bone elastic mechanical properties are dependent on density as well as strain rate, however, the effect these same variables on the post-yield behaviour of trabecular bone has not been thoroughly studied. For this study, bovine femoral samples were tested at several strain rates using three different tests devices: a conventional constant strain rate apparatus for low strain rates, a Drop Weight Impact Test device for the intermediate regime and a Split Hopkinson Pressure Bar System with magnesium bar and a PVCA pulse shaper for high strain rates. Ultimate and plateau stress, as well as absorbed energy were recorded. The results of this experimentation show that post-yield mechanical properties of trabecular bone are strain rate and volume fraction dependant. Two constitutive material models describing the Ultimate strength, Plateau stress and absorbed energy are proposed based on published models valid for elastic properties of trabecular bone.

Variations of the Frequency-Dependent Attenuation Coefficient with the Bone Mineral Density and the Architectural Parameters in Bovine Trabecular Bone

The present study aims to investigate the variations of the frequency-dependent attenuation coefficient with the bone mineral density (BMD) and two architectural parameters, the bone volume fraction (BV/TV) and the trabecular thickness (Tb.Th), in bovine trabecular bone in vitro. The attenuation coefficient was measured over a frequency range from 0.2 to 0.6 MHz in 22 bovine femoral trabecular bone samples. The frequency variation of the attenuation coefficient was characterized by using a nonlinear power law, α(f) = α0 + α1fn, at frequencies between 0.2 and 0.6 MHz. The parameters α (the attenuation coefficient at 0.4 MHz) and α1 exhibited high correlations with the BMD and the BV/TV and relatively low correlations with the Tb.Th. The parameter α1 was found to have weak correlations with the BMD and the Tb.Th and a very weak correlation with the BV/TV. In contrast, the exponent n showed no correlations with the BMD and the architectural parameters. These results suggest that measurements of the parameters α and α1 in trabecular bone may be useful for the assessment of bone status and osteoporosis. A scattering model based on velocity fluctuations in a binary mixture (cortical matrix and marrow fat) was successfully applied to predict the variations of the frequency-dependent attenuation coefficient with the architectural parameters observed in the 22 bone samples.

The influence of broach design on bone friction and osseodensification in total hip arthroplasty

BackgroundThe process of cavity preparation by broaching has an impact on the primary stability of uncemented hip stems and on the periprosthetic fracture risk. Osseodensifying broaches may increase primary stability, but have the potential to raise cortex strains and facilitate fracture.The aim of this study was to determine the influence of broach design on the forces acting during broaching, on the microstructure of the broached bone bed and the amount and depth of osseodensification. MethodsBroach models representing compaction, blunt extraction and sharp extraction broaches, were used for quasi-static simulation of femoral cavity preparation on bovine trabecular bone cuboids. Broaching forces were measured and micro-computed tomography scans performed prior and after testing. Friction coefficients during broaching, bone densification parameters and size of the debris particles pushed into the bone were determined. FindingsFriction coefficients during sharp extraction exceeded those during compaction and blunt extraction broaching (by 38% and 37%, P < .001). Total bone densification was enhanced for compaction and blunt extraction compared to sharp extraction broaching (increase of 121% and 117%, P = .005), resulting from higher densification depths for compaction (P = .001) and higher maximum densification for blunt extraction broaching (P = .008), with the latter producing fewer large particles than compaction broaching (P = .005). InterpretationHigher friction coefficients indicate a decreased periprosthetic fracture risk with sharp extraction broaches for equal implantation forces. The blunt extraction and compaction designs investigated densified the bone to a similar extent. Blunt extraction broaching may support better osseointegration due to smaller bone debris particles.

Investigating the Effects of Tissue-Specific Extracellular Matrix on the Adipogenic and Osteogenic Differentiation of Human Adipose-Derived Stromal Cells Within Composite Hydrogel Scaffolds.

While it has been postulated that tissue-specific bioscaffolds derived from the extracellular matrix (ECM) can direct stem cell differentiation, systematic comparisons of multiple ECM sources are needed to more fully assess the benefits of incorporating tissue-specific ECM in stem cell culture and delivery platforms. To probe the effects of ECM sourced from decellularized adipose tissue (DAT) or decellularized trabecular bone (DTB) on the adipogenic and osteogenic differentiation of human adipose-derived stem/stromal cells (ASCs), a novel detergent-free decellularization protocol was developed for bovine trabecular bone that complemented our established detergent-free decellularization protocol for human adipose tissue and did not require specialized equipment or prolonged incubation times. Immunohistochemical and biochemical characterization revealed enhanced sulphated glycosaminoglycan content in the DTB, while the DAT contained higher levels of collagen IV, collagen VI and laminin. To generate platforms with similar structural and biomechanical properties to enable assessment of the compositional effects of the ECM on ASC differentiation, micronized DAT and DTB were encapsulated with human ASCs within methacrylated chondroitin sulfate (MCS) hydrogels through UV-initiated crosslinking. High ASC viability (>90%) was observed over 14 days in culture. Adipogenic differentiation was enhanced in the MCS+DAT composites relative to the MCS+DTB composites and MCS controls after 14 days of culture in adipogenic medium. Osteogenic differentiation studies revealed a peak in alkaline phosphatase (ALP) enzyme activity at 7 days in the MCS+DTB group cultured in osteogenic medium, suggesting that the DTB had bioactive effects on osteogenic protein expression. Overall, the current study suggests that tissue-specific ECM sourced from DAT or DTB can act synergistically with soluble differentiation factors to enhance the lineage-specific differentiation of human ASCs within 3-D hydrogel systems.

Correlations of the Phase Velocity and the Dispersion with the Bone Mineral Density and the Architectural Parameters in Bovine Trabecular Bone

The present study aims to investigate the correlations of the phase velocity and the dispersion (the dispersion rate and the frequency dependence of the phase velocity) with the bone mineral density (BMD) and the architectural parameters (the bone volume fraction, the trabecular thickness, and the trabecular separation) in bovine trabecular bone in vitro. The frequency-dependent phase velocity, the dispersion rate, and the frequency dependence were measured over a frequency range from 0.2 to 0.6 MHz in 22 bovine femoral trabecular bone samples. The phase velocity and the dispersion rate showed significant correlations with the BMD and the architectural parameters. In contrast, the frequency dependence of the phase velocity was found to exhibit very weak correlations with the BMD and the architectural parameters. The stratified model for wave propagation in alternating parallel solid-fluid layers successfully predicted the variations of the phase velocity with the architectural parameters observed in the 22 bone samples.