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-SEM images of expandable rigid PU foam of three different densities at 500 m scale bar (a) 0.16 g/cm 3 (b) 0.24 g/cm 3 and (c) 0.42 g/cm 3 .
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An expandable rigid PU foam can turns into complex shapes, with a shell like structure on the outside and honeycomb structure on the inside, which can be easily shaped to a vertebra form. The present study aims to determine whether expandable rigid polyurethane foam was an appropriate substitute for rigid block polyurethane foam to model the trabec...
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... microstructure images were taken which displayed the closed cell PU foam for three different densities. The image showed in Fig. 3 displayed a uniform distribution of cells (pores) across the surface image when the foam expanded. It was expected that the higher density foam would have a larger value of cell size since there was an inverse relationship between density and cell size of the foam. Table 1 summarised the density and cell size measurements for each ...
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... However, PUs has the flexibility of being used to form complex shapes [25]. In this light, PU was used in biomedical research and was confirmed to compare favorably with human cadavers [26]. Meanwhile, it is the high density of glycerol content that impacts on the compressive property of PU foams under uniaxial compression at quasi-static dynamic loading [27]. ...
... In compression, the PU forms behaviour shows three characteristic regions (a short linear-elastic region, followed by a long and flat plateau and a densification) [17], while in tension there are a maximum of two regions (the linear-elastic region followed by brittle fracture, and sometimes a short plastic zone appears) [18]. However, it has been shown that the main advantage of PFs is to be used under compression loads, because they absorb very large amounts of energy until failure [19]. For such energy absorption applications (i.e. ...
... Previous studies have used synthetic bone ☆ word count, excluding references and captions: 5535 words analogues for testing different screw thread designs [14,15], materials [16] or type [17], i.e. cortical vs. trabecular screw. However, as pointed out in previous works [13,18] common synthetic bone analogues do not accurately represent the failure and plastic mechanical properties of bone in addition to the variability present in human bone structures [19], which means that they are not ideal for testing the influence of the underlying bone morphology on the mechanical competence of an implanted screw. additionally, these materials might not be available everywhere which makes them expensive and time consuming due to lengthy shipping times and fees. ...
Animal bones are commonly used to test the mechanical competence of bone screws since they are easier to obtain compared to human bones. Nevertheless, selecting an appropriate animal sample that correctly represents the human bone architecture where the screw is implanted is frequently overlooked. This study presents a protocol for bone sample selection for screw mechanical testing based on a characterization of the local CT-derived bone morphology. For this, 36 human radii were used to quantify the local peri-implant bone morphology of 360 osteosynthesis screws, 10 per bone, whose implantation site and depth were fully known. A cylindrical volume of interest was created along the screw path and used to measure the local morphology. With this, 10 average peri-implant bone morphologies were defined. Additionally, two animal models, pig, and sheep, were selected and used as potential sample sources. From each model, six bones were selected for analysis. Based on a surface mesh of each bone a computational algorithm was created to automatically extract cylindrical probes in several locations from which the local bone morphometry was calculated. A multi-parametric bone similarity score was developed and used to compare the local morphology of each animal bone to that of the human average peri-implant bone morphology. The score was then mapped to the surface of the bone thus allowing to visually identify regions on the animal bone with human-like bone morphology. By using this methodology, the use of human bones can be avoided since samples with human-like bone morphologies can be found on animal bones. This is not only useful in cases where strict ethical constrains must be fulfilled, but also in studies where the relationship between morphology and screw competence is to be studied, something that is hard to replicate with commercially available synthetic alternatives.
... Another important factor that was considered while developing the synthetic paediatric spine was the actual size of human paediatric spine. Assuming that size of the paediatric spine is 100%, the size of adult spine is normally scaled up to 141%, and the size of porcine spine is larger than an adult spine by an average difference of 50% [4,27,28]. Therefore, the porcine spine size is approximately 190% as compared to paediatric spine. ...
... Although the ROM in lateral bending and axial rotation from these FSUs were within the range provided by literature, the average was lower as compared to other FSUs. As suggested by Muhayudin et al. and White and Panjabi, specimen weight played a significant effect on the anatomical spine dimension, which may subsequently affect the ROM and in this research, whereby it significantly affected the flexion/extension [28,29]. Therefore, by considering the differences in flexion/extension between current study and literature, the results of porcine spine from this study were used in the comparative analysis with synthetic paediatric spine. ...
The present study is aimed at investigating the mechanical behaviour of fabricated synthetic midthoracic paediatric spine based on range of motion (ROM) as compared to porcine spine as the biological specimen. The main interest was to ensure that the fabricated synthetic model could mimic the biological specimen behaviour. The synthetic paediatric spine was designed as a 200% scaled-up model to fit into the Bionix Servohydraulic spine simulator. Biomechanical tests were conducted to measure the ROM and nonlinearity of sigmoidal curves at six degrees of freedom (DOF) with moments at ±4 Nm before the specimens failed. Results were compared with the porcine spine (biological specimen). The differences found between the lateral bending and axial rotation of synthetic paediatric spine as compared to the porcine spine were 18% and 3%, respectively, but was still within the range. Flexion extension of the synthetic spine is a bit stiff in comparison of porcine spine with 45% different. The ROM curves of the synthetic paediatric spine exhibited nonlinearities for all motions as the measurements of neutral zone (NZ) and elastic zone (EZ) stiffness were below “1.” Therefore, it showed that the proposed synthetic paediatric spine behaved similarly to the biological specimen, particularly on ROM.
... To date, the applicability of PU foam test results has been limited because the procedures, analyses and interpretations provide little reference to in vivo applications. Also in other fields of orthopaedic surgery and research, PU foam models have receive more interest because of improvement in production techniques with more sophisticated compositions available to recreate in vivo conditions [16]. In vivo conditions should be imitated as accurately as possible to objectively discuss the quality characteristics of osteosynthesis screws [12]. ...
Screw osteosynthesis using headless compression screws has become the accepted gold standard for the surgical treatment of scaphoid fractures. Optimal screw specifications remain controversially discussed. We aimed to investigate the influence of bone model composition on screw stability tests using headless compression screws in different scaphoid fracture models. We conducted pull-out tests using Acutrak2®mini, HCS®, HKS®, HBS®, Herbert/Whipple® and Twinfix® screws. To imitate cortical and cancellous bone, two-layer polyurethane (PU) models with two distinct densities were produced. The cylinders were cut at different positions to replicate fracture localisations at increasing distances. The maximum pull-out force required to achieve up to 1 mm of pull-out distance (Nto 1 mm) was measured. Acutrak2®mini and HCS® followed by Twinfix® showed the greatest average pull-out forces. Nto 1 mm was, on average, greater in the cortico-cancellous model than in the cancellous cylinder with the Acutrak2®mini and the Herbert/Whipple® screws, while it was the least with the HBS® and the Twinfix® screws; there were also differences between the HCS® and HKS®. There were no differences between the different fracture simulations in the synthesis strength using either the HKS® or HBS®. The pull-out forces of the HCS® and Twinfix® remained high also in simulations with the smaller screw base fragments. Varying imitations of cancellous and cortico-cancellous bone and fracture localisation reveal important information about the ex vivo strength of screw syntheses. The grip of the cortical structure should be used with the screws that fit more firmly in cortico-cancellous bone.
Shape engineering porous solids such as metal-organic frameworks (MOFs) into hierarchical structured adsorbents allows significant process intensification. Here we propose a facile approach to obtain a mouldable structured adsorbent with high loading of porous solids by employing a commercially available low-cost melamine sponge. As a case study, Mg-MOF-74 was synthesized in an aqueous media at room temperature and coated successfully over the melamine sponge, without any pre-treatment/additive, to yield a melamine sponge-based Mg-MOF-74 composite ([email protected]). Even after multiple coating steps, the composite displayed remarkable compressibility, thus providing additional degrees of freedom in designing packed bed systems over other rigid adsorbent forms and structures. The dynamic gas separation capability of the prepared [email protected] composite was demonstrated via breakthrough experiments with mixtures of 20% CO2 and 80% CH4 at 1 bar and 298 K. Owing to the spatial structure of melamine sponge, the composite retained the adsorption properties of Mg-MOF-74 for CO2 capture i.e., high dynamic capacity (5.07 mmol/g), high selectivity (>100), facile regeneration and performed better than binderless Mg-MOF-74 pellets in terms of mass transfer, unused bed length (LUB) and pressure drop (large permeability). Overall, these findings open an interesting field of research with melamine sponge-based MOF structured adsorbent as a potential candidate for gas-phase adsorption-based separation applications.
Human and animal cadaveric spines are the most common specimens used in biomechanical investigations. However, biological cadaveric spines come with a lot of disadvantages, which resulted in questionable reliability of the data obtained. This motivated the authors to look at the development of a working synthetic spine in motion segments because synthetic materials have been used widely to replace the cadaveric specimens especially for bone testing. The objective of this paper is to provide an overview of the current development of a working synthetic spine and why it is crucial to consider synthetic spine as another alternative specimens to replace human and animal cadaveric spines for biomechanical research. The development of synthetic spines studies in recent years showed a great potential to replicate the human cadaveric spine. Although some of the motions were quite stiff in comparison with human cadaveric motions, with further adjustment, the improved synthetic spine can potentially benefit and transform the spinal biomechanical investigations in the future.
The mechanical failure behaviors prediction model of rigid polyurethane foam (RPUF) treated under complex thermal-vibration conditions was constructed by experiment of tensile properties and numerical simulation for the further analysis of the failure progress and mechanism of RPUF. On the basis of scanning electron microscope (SEM) observation, a realistic representative volume element (RVE) of RPUF was firstly established by means of Voronoi-spherical tessellations. Tensile properties of RPUF treated under different thermal-vibration conditions were measured subsequently. Results of the tensile properties characterization of RPUF suggested that the thermal and vibration treatment on RPUF reduced its tensile strength and fracture elongation decrease due to the chemical degradation of polyurethane (PU) matrix and physical breaking of the foam structure. The tensile constitutive relationship derived from the tensile experiments was assigned to the realistic RVE, and the thermal-vibration failure prediction model of RPUF was further constructed in the ABAQUS software. The numerical simulation results revealed that the stress concentrations appeared and extended along with the weakness regions of RPUF structure under the external load. The stress-strain curves of thermal-vibration treated RPUF obtained from the prediction model were in well agreement with the experimental results, and the average computation error was less than 3%. It indicated that the prediction model can accurately describe the failure progress of thermal-vibration treated RPUF. This work provides ideas for the design of the foam materials with high thermal-vibration aging resistance by numerical simulation in the future.
