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This study aimed to report the extraction of micro-fibrillated cellulose (MFC) from rice husk (RH) through a series of processes including alkalization, bleaching, chemical hydrolysis, and mechanical treatment. The chemical structure, morphology, and crystallinity were assessed using Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscope (SEM), and X-ray diffraction (XRD). The results showed that alkalization was more effective in removing unwanted substances such as silica, hemicellulose, and lignin compared to bleaching. Chemical or mechanical treatment was more targeted towards removing the amorphous phase while fibrillating MFC. Further mechanical treatment significantly enhanced the crystallinity index (CI) of MFC, reaching 87.47%, while chemical treatment remained at 78.54%. The mechanical treatment led to a larger void size due to rigorous fibrillation, resulting in increased water retention during extraction compared to chemically treated MFC with a negatively charged surface. Crystal extraction through mechanical treatment disrupted the hydrogen bond, transforming cellulose crystal from triclinic I? to monoclinic The comprehensive evaluation of MFC extracted from RH showed its potential for biomedical application.

The deformation behavior of an artificial heart valve was analyzed using the explicit dynamic finite element method. Time variations of the left ventricle and the aortic pressure were considered as the mechanical boundary conditions in order to reproduce the opening and closing movements of the valve under the full cardiac cycle. The valve was assumed to be made from a medical polymer and hence, a hyperelastic Mooney–Rivlin model was assigned as the material model. A simple formula of the damage mechanics was also introduced into the theoretical material model to express the hysteresis response under the unloading state. Effects of the hysteresis on the valve deformation were characterized by the delay of response and the enlargement of displacement. Most importantly, the elastic vibration observed in the pure elastic response under the full close state was dramatically reduced by the conversion of a part of elastic energy to the dissipated energy due to hysteresis.

Abstract Background The use of spinal instrumentation is an established risk factor for postoperative infection. To address this problem, we prepared silver‐containing hydroxyapatite coating, consisting of highly osteoconductive hydroxyapatite interfused with silver. The technology has been adopted for total hip arthroplasty. Silver‐containing hydroxyapatite coating has been reported to have good biocompatibility and low toxicity. However, no studies about applying this coating in spinal surgery have addressed the osteoconductivity and direct neurotoxicity to the spinal cord of silver‐containing hydroxyapatite cages in spinal interbody fusion. Aim In this study, we evaluated the osteoconductivity and neurotoxicity of silver‐containing hydroxyapatite‐coated implants in rats. Materials & Methods Titanium (non‐coated, hydroxyapatite‐coated, and silver‐containing hydroxyapatite‐coated) interbody cages were inserted into the spine for anterior lumbar fusion. At 8 weeks postoperatively, micro‐computed tomography and histology were performed to evaluate the osteoconductivity of the cage. Inclined plane test and toe pinch test were performed postoperatively to assess neurotoxicity. Results Micro‐computed tomography data indicated no significant difference in bone volume/total volume among the three groups. Histologically, the hydroxyapatite‐coated and silver‐containing hydroxyapatite‐coated groups showed significantly higher bone contact rate than that of the titanium group. In contrast, there was no significant difference in bone formation rate among the three groups. Data of inclined plane and toe pinch test showed no significant loss of motor and sensory function in the three groups. Furthermore, there was no degeneration, necrosis, or accumulation of silver in the spinal cord on histology. Conclusions This study suggests that silver‐hydroxyapatite‐coated interbody cages produce good osteoconductivity and are not associated with direct neurotoxicity.

We designed this study to evaluate the application of alginic acid gel beads, which are known to facilitate increased water retention. These scaffolds were coated with an aqueous solution of the same material creating a concentration gradient between the gel beads and the sodium alginate aqueous solution, which fills the surrounding 3D layered structure to improve stability. The aim of this study was to enhance the mechanical properties and stability of these scaffolds to promote effective proliferation and differentiation in the native setting.The three-dimensional gel beads were formed by reacting a sodium alginate aqueous solution with a calcium chloride aqueous solution. The gel beads were evaluated by diameter and sphericity. As the concentration of sodium alginate increased, the diameter of the gel beads increased and sphericity became approximately 1. Then the three-dimensional structure was formed by layering the gel beads on a 24-well plate. The three-dimensional layered structures with gel beads were tested using a universal testing machine and evaluated compressive mechanical property. The modulus of elasticity for the three-dimensional layered structures with gel beads was the highest when the concentrations of the gel beads and surroundings were the same. In vitro experiment, the cell number and ALP activity were also measured by plate reader. The results of the in vitro experiments showed no difference in the cell numbers with the control, but the ALP activity tended to be higher with the samples having a high modulus of elasticity. It is concluded that three-dimensional layered structures with gel beads were effective for bone tissue regeneration as a scaffold.

It is possible to have a varus or valgus placement of resurfacing hip implants after resurfacing hip arthroplasty based on clinical reports. The likelihood of accidents such as sideways falls during the recovery process after arthroplasty is higher for the patient due to gait adaptation and weaker lower body condition. Hence, a computational study has been conducted to predict the risk of bone fracture with different implant placements during sideways fall accidents. A CT image of a young adult with hip osteoarthritis was imported into biomechanical software to develop the 3D inhomogeneous femoral bone model. A model of the Birmingham Hip Resurfacing implant with the properties of cobalt-chromium alloy was inserted into the femur during the reconstruction of the arthroplasty, which mimics the procedure of clinical practice. The loading and boundary conditions were implemented to simulate the sideways fall accident, and the prediction of bone fracture was based on the formation of failure elements. The loading magnitude was applied based on the patient’s body weight, ranging from the patient’s body weight (1 BW) to five times the patient’s body weight (5 BW). The fracture location was predicted to occur at the neck and trochanteric area of the femur, with the greatest damage occurring to the bone model implanted with varus placement. Our finding concludes that the varus placement of the resurfacing hip implant should be avoided whenever possible in clinical practice to sustain bone survivability.

A sponge template method was used to synthesize scaffolds from hydroxyapatite (HAp) using varying sintering temperatures and compressive ratios. The HAp scaffolds were fabricated with collagen (COL) or collagen/HAp particles under room temperature coating conditions. The microstructure and mechanical properties of the fabricated biomaterials were analyzed by FE-SEM and EZ Test, respectively. The FE-SEM micrographs showed microporous structure of the fabricated composite scaffolds. Incorporation of COL or COL/HAp into pure HAp scaffolds under coating conditions significantly reduced the porosity and enhanced the mechanical properties. The results demonstrated that the porosity of fabricated scaffolds was reduced by lowering the compressive pressure and increasing the sintering temperature. The maximum estimated compressive moduli at 1000, 1100 and 1200 °C for HAp-COL and HAp-COL/HAp composite scaffolds were 4.36, 2.93, 5.09 MPa and 4.57, 8.19, 5.02 MPa, respectively, at a 50% compressive ratio. It was assumed that porosity was effectively reduced to the maximum level at a 50% compressive ratio. An in vitro stem cell study showed significant cell adhesion and proliferation over the fabricated HAp-COL and HAp-COL/HAp composite scaffolds. These results confirmed that fabrication of pure HAp with COL and COL/HAp materials had advanced effects on the mechanical properties of fabricated porous composite scaffolds.

The prediction of bone remodeling behaviour is a challenging factor in encouraging the long-term stability of hip arthroplasties. The presence of femoral components modifies the biomechanical environment of the bone and alters the bone growth process. Issues of bone loss and gait instability on both limbs are associated with the remodeling process. In this study, finite element analysis with an adaptive bone remodeling algorithm was used to predict the changes in bone mineral density following total hip and resurfacing hip arthroplasty. A three-dimensional model of the pelvis–femur was constructed from computed tomography (CT-based) images of a 79-year-old female patient with hip osteoarthritis. The prosthesis stem of the total hip arthroplasty was modelled with a titanium alloy material, while the femoral head had alumina properties. Meanwhile, resurfacing of the hip implant was completed with a cobalt-chromium material. Contact between the components and bone was designed to be perfectly bonded at the interface. Results indicate that the bone mineral density was modified over five years on all models, including hip osteoarthritis. The changes of BMD were predicted as being high between year zero and year one, especially in the proximal region. Changes were observed to be minimal in the following years. The bone remodeling process was also predicted for the non-operated femur. However, the adaptation was lower compared to the operated limbs. The reduction in bone mineral density suggested the bone loss phenomenon after a few years.

Polymeric scaffolds made of PCL/PLCL (ratio 1:3, respectively) blends have been developed by using the Thermally Induced Phase Separation (TIPS) process. A new additional technique has been introduced in this study by applying pre-heat treatment to the blend solution before the TIPS process. The main objective of this study is to evaluate the influence of the pre-heat treatment on mechanical properties. The mechanical evaluation showed that the mechanical strength of the scaffolds (including tensile strength, elastic modulus, and strain) improved as the temperature of the polymer blend solution increased. The effects on the microstructure features were also observed, such as increasing strut size and differences in phase separation morphology. Those microstructure changes due to temperature control contributed to the increasing of mechanical strength. The in vitro cell study showed that the PCL/PLCL blend scaffold exhibited better cytocompatibility than the neat PCL scaffold, indicated by a higher proliferation at 4 and 7 days in culture. This study highlighted that the improvement of the mechanical strength of polymer blends scaffolds can be achieved using a very versatile way by controlling the temperature of the polymer blend solution before the TIPS process.

Three-dimensional maxillary bone models of a male and a female patient were constructed using their CT-images. The distributions of Young's modulus were estimated from their bone mineral density distributions. Total six implants were embedded into each of the maxillary models. Finite element analysis of the maxilla models was then performed in order to assess the concentrations of strain energy density especially in the vicinities of the embedded implants. It was found that in both models, strain energy density was concentrated especially around the right-molar implant, suggesting outbreak of damage and subsequent absorption of bone tissue in this region. The female model with smaller size and lower bone density exhibited much higher localized concentration of strain energy density than the male model. Therefore, a modified placement of the right-molar implant was then introduced into the female model and such high concentration was effectively reduced by using the inclined and longer implant. It is thus concluded that this kind of three-dimensional modeling can clinically be used to predict the optimal implant treatment for each of dental patients.

Displacement of actin filament and its binding proteins in mouse myoblasts under locally applied deformation was analyzed by manual method or digital image correlation method. Cyotoskeletal components labeled by immunofluorescent technique or green fluorescent protein-fused protein were deformed via the movement of a glass needle which was poked into a cell. First, we confirmed the digital image correlation method is able to use to analyze displacement map by comparison of the manual method. Next, we examined whether the applied deformation isotropically propagates into cell body. At focal adhesions, fluorescent signals from the deformed area unchanged under the application. Mainly, focal adhesions around the poked area were moved to the direction of the movement of the needle. In addition, some adhesions away from the poked area were moved. Similar results were observed in phalloidin-stained cells. Finally, we applied the local deformation to live cells. However, displacement at the locally deformed area was not observed due to the disappearance of fluorescent signals. These results indicate that applied deformation propagated heterogeneously into a cell, and may imply that biochemical signals disrupt actin fibers under local deformation.

Previously, a few models have been proposed to predict bone resorption process due to stress shielding in long bones such as proximal femur; however, there are almost no reports on finite element analysis of loss of marginal dental bone that is caused mainly by occlusive overload. In this work, the stress, strain and strain energy density (SED) criteria were separately applied to simulate overload-induced bone resorption in a jawbone/implant system by means of the finite element analysis. A simplified dental bone/implant model was created, with the bone composed of a cortical bone and a cancellous bone and the implant having the detailed screw structure. The results demonstrated that the simulations according to the equal SED criterion reproduce bone resorption patterns that are more realistic to actual clinical situations, when compared to the equal stress or strain criterion. It was shown that bone resorption starts initially in the cortical bone around the implant neck, then extends downwards, and lastly enters the cancellous bone after passing through the interface of the cortical and cancellous bone. A symmetric bone resorption pattern was revealed under the condition of axial loading, whereas an asymmetric resorption prototype was demonstrated under the oblique loading condition. Moreover, in the case of oblique loading, bone resorption is faster and the amount of resorbed bone is larger, which leads to more micromotion of the dental implant than in the case of axial loading.

A porcine mandible was separated to prepare thin periodontium specimens, consisting of a molar, periodontal ligament (PDL), and alveolar bone. Occlusion was simulated by applying a forced compressive displacement, using a table-top material tester. We photographed images of the displacing periodontium specimen and simultaneously obtained the load-displacement curve during the test. The displacement and deformation distributions were examined using digital image correlation analysis. Then, we correlated the distribution with the load-displacement curve, which was characterized by biphasic behavior, as noted in many previous studies. We found that the displacement and deformation distributions of actual periodontium correlated with the load-displacement curve during dental occlusion. Regarding the biphasic characteristics of the load-displacement curve, we showed experimentally that the first phase indicated deformation of the PDL and the second indicated deformation of the alveolar bone and tooth.

In the present study, peri-implant tissue alteration was studied histologically, and then differences in the gene expression pattern of certain proteins were analyzed using cDNA microarray analysis, under the influence of static lateral load. Beagle dogs were divided into two groups: control and load. Three months after the extraction of mandibular premolars, two implants were placed in each side of the mandible. Each group was further divided into subgroups for loading times of 1, 7 and 14 days. Immediately after the implant installation, a loading device was adhered between the abutments of neighboring implants. Afterward, the expansion screw of the load group was activated by 360-degree rotation, resulting in 0.7 mm horizontal expansion. After sacrificing the dogs, peri-implant tissue was collected, then microarray analysis for the detection of gene expression was performed, as well as histology. Histology indicated that the peri-implant tissue broke down under the influence of the load. Microarray analysis demonstrated the presence of load-sensitive gene expression even after 1 day. Differences in gene expression patterns in concert with static lateral load were demonstrated, even at an early stage post-operation. Further study may help in the diagnosis of pathological overload.

3-D finite element models of two types of PS type knee prostheses were constructed using their CAD data with use of a nonlinear spring model and an analytical load data for deep squatting. PS-type1 model was formerly used in total knee arthroplasty, and PS-type2 model is the latest version with a modified design of post structure. Stress analysis was then performed by an explicit finite element method under continuous flexion motion from 0 to 135 degrees with internal rotation up to 10 degrees. It was shown that the post/cam contact starts at about 65 degrees of flexion, and the equivalent stress rapidly increases due to the contact. Severe stress concentration is also generated on the Post surface due to the post/cam contact. This kind of stress concentration may cause damage and failure of the post. It was clearly shown that the design modification applied to PS-type2 effectively reduced the stress concentration of the post.

3-D finite element models of two kinds of Stryker's PS type knee prostheses, Scorpio Superflex and NRG, were constructed using their CAD data with use of a nonlinear spring model and an analytical load data for deep squatting. Superflex model was formerly used in TKA, and NRG model is the latest version with a modified design of Post. Stress analysis was then performed by an explicit finite element method under continuous flexion motion from 0 to 135 degree. It was shown that only the condylar surfaces of the femoral component and the tibial insert contacted each other from 0 to 60 degree flexion for both the models, and the stress concentration in NRG was a little higher than that in Superflex. The simulation results also exhibited that severe stress concentration was generated at Post of the tibial UHMWPE insert due to Post/Cam contact. This kind of stress concentration may result in damage and failure of Post. It was shown that the design modification applied to NRG effectively reduced the stress concentration of Post.

In this study, we clarified dental occlusion functions by visualizing the displacement and deformation patterns of the periodontium under dental occlusion. A digital image correlation method served as a visualization and deformation analysis method using fresh porcine periodontium specimens. Also using dried periodontium specimens, we conducted the occlusion test to characterize the differences in displacement and deformation patterns between fresh and dried specimens. Results indicated that the periodontal ligaments deform first, followed by alveolar bones. Marked differences in displacement and deformation patterns were observed between the fresh and dried periodontium specimens.

One of the most common errors of total knee arthroplasty procedure is a malrotation of tibial component. The stress on tibial insert is closely related to polyethylene failure. The objective of this study is to analyze the effect of malrotation of tibial component for the stress on tibial insert during high flexion using a finite element analysis. We used Stryker NRG PS for analysis. Three different initial conditions of tibial component including normal, 15° internal malrotation, and 15° external malrotation were analyzed. The tibial insert made from ultra-high-molecular-weight polyethylene was assumed to be elastic-plastic while femoral and tibial metal components were assumed to be rigid. Four nonlinear springs attached to tibial component represented soft tissues around the knee. Vertical load was applied to femoral component which rotated from 0° to 135° while horizontal load along the anterior posterior axis was applied to tibial component during flexion. Maximum equivalent stresses on the surface were analyzed. Internal malrotation caused the highest stress which arose up to 160% of normal position. External malrotation also caused higher stress. Implanting prosthesis in correct position is important for reducing the risk of abnormal wear and failure.

The primary objective of this study is to distinguish between mobile bearing and fixed bearing posterior stabilized knee prostheses in the mechanics performance using the finite element simulation. Quantifying the relative mechanics attributes and survivorship between the mobile bearing and the fixed bearing prosthesis remains in investigation among researchers. In the present study, 3-dimensional computational model of a clinically used mobile bearing PS type knee prosthesis was utilized to develop a finite element and dynamic simulation model. Combination of displacement and force driven knee motion was adapted to simulate a flexion motion from 0° to 135° with neutral, 10°, and 20° internal tibial rotation to represent deep knee bending. Introduction of the secondary moving articulation in the mobile bearing knee prosthesis has been found to maintain relatively low shear stress during deep knee motion with tibial rotation.

A layered construct was developed by combining a porous polymer sheet and a cell sheet as a tissue engineered vascular patch. The primary objective of this study is to investigate the influence of mesenchymal stem cells (MSCs) sheet on the tensile mechanical properties of porous poly-(l-lactide-co-ε-caprolactone) (PLCL) sheet. The porous PLCL sheet was fabricated by the solid-liquid phase separation method and the following freeze-drying method. The MSCs sheet, prepared by the temperature-responsive dish, was then layered on the top of the PLCL sheet and cultured for 2 weeks. During the in vitro study, cellular properties such as cell infiltration, spreading and proliferation were evaluated. Tensile test of the layered construct was performed periodically to characterize the tensile mechanical behavior. The tensile properties were then correlated with the cellular properties to understand the effect of MSCs sheet on the variation of the mechanical behavior during the in vitro study. It was found that MSCs from the cell sheet were able to migrate into the PLCL sheet and actively proliferated into the porous structure then formed a new layer of MSCs on the opposite surface of the PLCL sheet. Mechanical evaluation revealed that the PLCL sheet with MSCs showed enhancement of tensile strength and strain energy density at the first week of culture which is characterized as the effect of MSCs proliferation and its infiltration into the porous structure of the PLCL sheet. New technique was presented to develop tissue engineered patch by combining MSCs sheet and porous PLCL sheet, and it is expected that the layered patch may prolong biomechanical stability when implanted in vivo.

Purpose. To assess the effect of each step of medial soft-tissue releases on the joint gap angle during posterior-stabilised total knee arthroplasty (TKA). Methods. 82 women and 9 men (mean age, 72 years) with medial osteoarthritic knees underwent 100 posterior-stabilised TKAs, in which release of superficial fibres of the medial collateral ligament (MCL) were required using the gap control technique. The order of releases was the superficial MCL, the pes anserinus, and then the semi-membranosus. The superficial MCL was released selectively. The effect of each step of medial soft-tissue releases in full extension and in 90° flexion was compared. Results. After all medial soft-tissue releases, the mean joint gap angles decreased from 8.7° to 3.8° varus in flexion and from 4.4° to 1.4° varus in extension. The total effect of medial soft-tissue releases was significantly larger in flexion than in extension (4.9°±3.2° vs. 3.0°±2.0°, p