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Objective To study changes in bone microstructure of osteoporotic rats by multiscale analysis. Methods A total of 20 5-month-old female SD rats were randomly divided into two groups, i.e., ovariectomy (OVX) group (n=12) and the SHAM group (n=8), respectively. The rats in OVX group were subjected to bilateral ovariectomy and became osteoporosis models after 8 weeks, while sham operation was performed for the SHAM group. Changes in microstructure of cortical bone and cancellous bone at tissue scale, and osteocyte lacunar-canalicular network (LCN) and extracellular matrix (ECM) at cell scale were quantitatively analyzed using Micro-CT and SR-Nano-CT. Results At tissue scale, the cross-sectional area of cortical bone in OVX group was significantly higher than that in SHAM group (P<0.05), and the bone mineral density (BMD) and thickness of cortical bone were not significantly different from those in SHAM group. The trabecular BMD, bone volume fraction, trabecular thickness and trabecular number in OVX group were significantly decreased in comparison with SHAM group (P<0.01), while the trabecular separation was significantly increased (P<0.01). At cell scale, there was no significant difference in the semiaxes of lacunae between OVX group and SHAM group, but the thickness of lacunae and the diameter of canaliculi in OVX group were significantly increased in comparison with SHAM group (P<0.05). At the same time, the porosity of cortical bone in OVX group was significantly higher than that in SHAM group at cell scale (P<0.05). Conclusions The bone microstructure in OVX group varied to different extents at tissue and cell scales. At tissue scale, the cancellous bone loss was severe, while the cortical bone had fewer changes. At cell scale, porosity of the lacunar-canalicular network significantly increased, which directly affected the BMD and strength of cortical bone. Multiscale analysis on changes in bone microstructure of OP rats has potential application value for clinical diagnosis and pathological analysis of osteoporosis.
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Objective To analyze the influence of total hip arthroplasty (THA) on the process of proximal femoral bone remodeling by using the Wolff bone remodeling theory. Methods According to control equation of bone remodeling, the program of bone remodeling was written in Python language. Preoperative femur model and postoperative femur and prosthesis finite element models were established respectively in ABAQUS software. The process of bone reconstruction before and after THA operation was compared to analyze the effect of prosthesis implantation on mechanical properties of the femur in the middle and long term after THA operation. Results The stress in proximal femur continued to decrease after prosthesis implantation, and the stress site was transferred from the femoral head to the prosthesis, resulting in an obvious stress shielding phenomenon. Bone loss in the stress shielding area was serious. The femoral shaft cortical bone became thinner and the stress shielding was relieved. The medial side at the bottom of the prosthesis was compressed, and the stress was significantly higher than that of the lateral side, where the bone was unevenly distributed. Conclusions After THA operation, obvious stress shielding occured at proximal medial side of the femur, leading to bone loss and prosthesis loosening. The difference in stress levels on both sides at the bottom of the prosthesis resulted in an uneven bone distribution, causing the discordance between the prosthesis and the femur, as well as postoperative pain in the middle part of the thigh.
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Biomechanical model of musculoskeletal system has accurate human anatomy and good biological fidelity. It can accurately and effectively reveal the biomechanical state and predict the internal mechanical response of musculoskeletal system. Therefore, it has been widely used in biomechanical study of musculoskeletal system, diagnosis and treatment of bone diseases, implant optimization design and preoperative planning. In 2021, the latest advances in biomechanical modeling method of musculoskeletal system mainly included three aspects, i.e., individualized finite element modeling, statistical model modeling and musculoskeletal system modeling. On this basis, the latest relevant literatures were summarized in this review to illustrate the progress and main applications of the above modeling method, and the future development direction of musculoskeletal modeling was discussed.
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In order to establish a bone scaffold with good biological properties, two kinds of new gradient triply periodic minimal surfaces (TPMS) scaffolds, i.e., two-way linear gradient G scaffolds (L-G) and D, G fusion scaffold (N-G) were designed based on the gyroid (G) and diamond (D)-type TPMS in this study. The structural mechanical parameters of the two kinds of scaffolds were obtained through the compressive simulation. The flow property parameters were also obtained through the computational fluid dynamics (CFD) simulation in this study, and the permeability of the two kinds of scaffolds were calculated by Darcy's law. The tissue differentiation areas of the two kinds of scaffolds were calculated based on the tissue differentiation theory. The results show that L-G scaffold has a better mechanical property than the N-G scaffold. However, N-G scaffold is better than the L-G scaffold in biological properties such as permeability and cartilage differentiation areas. The modeling processes of L-G and N-G scaffolds provide a new insight for the design of bone scaffold. The simulation in this study can also give reference for the prediction of osseointegration after the implantation of scaffold in the human body.
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Humans , Bone and Bones , Permeability , Porosity , Tissue Engineering , Tissue ScaffoldsABSTRACT
Aging is a major risk factor for diseases such as osteoarthritis (OA) and osteoporosis. However, they are not necessarily the results of aging, and the relationship between changes in bone and cartilage associated with aging and disease progression is still unclear. Studies have shown that the development and progression of OA is not a simple cartilage wear process, while its occurrence involves complex biological, chemical and mechanical changes in the tissues of the entire joint, especially the interaction of mechanics and biochemistry between cartilage and subchondral bone. Aging contributes to the occurrence and development of OA, but it is not the cause of OA. Changes associated with aging provide a foundation for OA to start, making joints more susceptible to other factors such as abnormal biomechanics and biochemistry, thereby promoting the development of OA. Therefore, understanding the basic mechanisms by which aging affects joint tissue may provide new targets for slowing or preventing the development of OA. In this paper, the related research progresses are reviewed from three aspects, i.e. age-related changes in cartilage and subchondral bone, mechanical conduction and angiogenesis.
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The high elastic modulus of scaffolds or implants will result in stress shielding effect, which may lead to bone resorption and scaffold or implant loosening in the late stage. Porous scaffolds and implants can adjust their porosity and elastic modulus according to the mechanical environment, thereby reducing stress shielding; meanwhile, porous structures are beneficial to bone tissue growth, which is conducive to osseointegration. Three kinds of basic structure for porous scaffolds and implants by 3D printing were summarized, namely, uniform porous structure, bone-like trabecular structure and functionally graded structure. The design methods of these structures were introduced respectively, including computer-aided design (CAD)-based, implicit surface-based, image-based and topology optimization-based design method, so as to provide references for solving the stress shielding problem, as well as designing porous scaffolds and implants.
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Objective To study the change patterns of bone microstructural parameters around the magnesium based- implants after implantation in rabbit femur at different implantation time points. Methods The threaded and non-threaded high-purity magnesium (HP Mg, 99.99 wt.%) screws, with a 2 mm diameter and a 7 mm length, were implanted into the femoral condyle of the rabbits. The control group was the drilled and healthy group. Micro-CT scanning and analysis were performed at 8th, 12th and 16th week after operation. The obtained microstructural parameters included bone mineral density (BMD), bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp). Results At 8th week, BMD and BV/TV in non-threaded magnesium screw group were significantly higher than those in healthy group, Tb.N was significantly higher than that in drilled and healthy group, and Tb.Sp was significantly lower than that in healthy group. At 12th week, BMD, BV/TV and Tb.N in threaded magnesium screw group were significantly higher than those in drilled and healthy group, Tb.Th was significantly higher than that in healthy group, and Tb.Sp was significantly lower than that in drilled and healthy group. At 16th week, BMD, BV/TV and Tb.N in non-threaded magnesium screw group were significantly higher than those in drilled and healthy group, and Tb.Sp was significantly lower than that in drilled and healthy group. Conclusions The magnesium based-implant promoted higher BMD, BV/TV, Tb.Th, Tb.N and lower Tb.Sp of surrounding implant, indicating that osseointegration and bone growth were in good condition. Magnesium based-implant could effectively promote the regeneration of bone. The results provide a theoretical basis for the orthopedic application of magnesium based-implants in clinic.
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With the increasing life span of the population and the increasing proportion of the elderly population, the elderly with osteoporosis are prone to hip fractures, which brings heavy economic burdens to the family and society. The progress in predicting hip fractures from the aspects of the proximal femur geometry, bone mineral density (BMD), fracture risk assessment tool (FRAX) and finite element analysis (FEA) based on computed tomography (CT) imaging was reviewed, in order to understand the influencing factors of fracture risk, improve the accuracy of hip fracture risk prediction for the elderly, detect the high fracture risk group at an early stage, and hence to reduce the occurrence of fractures with appropriate preventing measures, and provide theoretical references for the prevention and treatment of hip fractures.
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The high elastic modulus of scaffolds or implants will result in stress shielding effect, which may lead to bone resorption and scaffold or implant loosening in the late stage. Porous scaffolds and implants can adjust their porosity and elastic modulus according to the mechanical environment, thereby reducing stress shielding; meanwhile, porous structures are beneficial to bone tissue growth, which is conducive to osseointegration. Three kinds of basic structure for porous scaffolds and implants by 3D printing were summarized, namely, uniform porous structure, bone-like trabecular structure and functionally graded structure. The design methods of these structures were introduced respectively, including computer-aided design (CAD)-based, implicit surface-based, image-based and topology optimization-based design method, so as to provide references for solving the stress shielding problem, as well as designing porous scaffolds and implants.
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Objective To study the vibration characteristics of a normal C2-7 cervical spine finite element model and vibration changes of a cervical facet joint with different degrees of impairment or that is resected. Methods The finite element model of a normal C2-7 cervical spine based on computed tomography (CT) scan images was established and validated. Next, the normal frequency and first ten modes of the normal cervical spine model were extracted. A facet joint was considered without or with joint constraints with a friction coefficient of 0.01, 0.1 and 0.2 to simulate a resected facet joint or a facet joint with mild, moderate, and severe damage, respectively. Thus, the effects of different types of damage to the cervical spine on their natural frequencies could be studied. Results The minimum natural frequency of the normal model occurred in the extension and lateral bending modes and it was approximately 12 Hz. A large displacement in the model occurred mainly in the atlas. The frequency of the model with the constrained joint was higher than that without joint constraints; however, the natural frequencies of the facet joints with different friction coefficients remained almost unchanged. Conclusions The study of the natural frequency, mode shape, and amplitude of the cervical spine provided the basis for further studying its dynamic characteristics, which is of tremendous significance in the nursing and treatment of cervical vertebrae. A vibration environment of 12 Hz should be avoided in daily activities and cervical treatment to prevent severe damage to the cervical spine.
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The function of health care and rehabilitation in Tai Chi has been recognized by the world.Studies on the mechanism of health care in Tai Chi have been conducted by domestic and international experts using the methods of sports biomechanics,most of which focus on human lower extremity.Twenty research literatures (15articles in English and 5 articles in Chinese) during the year 2007-2015 about biomechanics of the lower extremity in Tai Chi were searched.According to the research purpose and evaluation index,this paper mainly reviewed from 3 aspects:the kinematic & kinetic characteristics of Tai Chi and its influence on the lower extremity,the effect of Tai Chi on muscle activity of the lower extremity,and the impact of Tai Chi movement on interaction between biomechanical parameters of the lower extremity and other system parameters.The prospects and limitations in biomechanical studies on the lower extremity in Tai Chi were also summarized.
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High flexion squat is extremely common in the daily activities of Asian countries and certain occupations. In this paper, different types of deep squats and their motion characteristics were summarized, and recent research progress of squat biomechanics was reviewed. Different research methods on squats such as in vitro experiment, in vivo test and computer simulation were also classified and represented. Biomechanical studies on deep squat of the knee can benefit establishment of reasonable rehabilitation training, prevention of sports risks as well as provide some references for optimization of knee prosthesis design.
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The function of health care and rehabilitation in Tai Chi has been recognized by the world. Studies on the mechanism of health care in Tai Chi have been conducted by domestic and international experts using the methods of sports biomechanics, most of which focus on human lower extremity. Twenty research literatures (15 articles in English and 5 articles in Chinese) during the year 2007-2015 about biomechanics of the lower extremity in Tai Chi were searched. According to the research purpose and evaluation index, this paper mainly reviewed from 3 aspects: the kinematic & kinetic characteristics of Tai Chi and its influence on the lower extremity, the effect of Tai Chi on muscle activity of the lower extremity, and the impact of Tai Chi movement on interaction between biomechanical parameters of the lower extremity and other system parameters. The prospects and limitations in biomechanical studies on the lower extremity in Tai Chi were also summarized.
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High flexion squat is extremely common in the daily activities of Asian countries and certain occupations.In this paper,different types of deep squats and their motion characteristics were summarized,and recent research progress of squat biomechanics was reviewed.Different research methods on squats such as in vitro experiment,in vivo test and computer simulation were also classified and represented.Biomechanical studies on deep squat of the knee can benefit establishment of reasonable rehabilitation training,prevention of sports risks as well as provide some references for optimization of knee prosthesis design.
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The function of health care and rehabilitation in Tai Chi has been recognized by the world.Studies on the mechanism of health care in Tai Chi have been conducted by domestic and international experts using the methods of sports biomechanics,most of which focus on human lower extremity.Twenty research literatures (15articles in English and 5 articles in Chinese) during the year 2007-2015 about biomechanics of the lower extremity in Tai Chi were searched.According to the research purpose and evaluation index,this paper mainly reviewed from 3 aspects:the kinematic & kinetic characteristics of Tai Chi and its influence on the lower extremity,the effect of Tai Chi on muscle activity of the lower extremity,and the impact of Tai Chi movement on interaction between biomechanical parameters of the lower extremity and other system parameters.The prospects and limitations in biomechanical studies on the lower extremity in Tai Chi were also summarized.
ABSTRACT
The function of health care and rehabilitation in Tai Chi has been recognized by the world.Studies on the mechanism of health care in Tai Chi have been conducted by domestic and international experts using the methods of sports biomechanics,most of which focus on human lower extremity.Twenty research literatures (15articles in English and 5 articles in Chinese) during the year 2007-2015 about biomechanics of the lower extremity in Tai Chi were searched.According to the research purpose and evaluation index,this paper mainly reviewed from 3 aspects:the kinematic & kinetic characteristics of Tai Chi and its influence on the lower extremity,the effect of Tai Chi on muscle activity of the lower extremity,and the impact of Tai Chi movement on interaction between biomechanical parameters of the lower extremity and other system parameters.The prospects and limitations in biomechanical studies on the lower extremity in Tai Chi were also summarized.
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Objective To investigate the effects of element size and type, material property distributions of vertebral cancellous bone and simulation methods of cortical bone structure on the finite element (FE) results during the finite element modeling of lumbar vertebral body. Methods Based on QCT images of lumbar spine, 22 FE models of L2 without posterior structure were built by 6 element sizes (0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mm), 2 heterogeneous material distribution methods of cancellous bone (300, 150) and 2 cortical bone modeling methods. The maximum displacement, strain energy, average stress and axial stiffness of these models were obtained to analyze and verify the results. Results When the element size was 0.5 mm, the axial stiffness of models with 10, 150 and 300 kinds of heterogeneous materials showed obvious differences; for the vertebral cancellous bone with 150 kinds of materials, the variation of average stress was not distinct under different element sizes; the average stress of the model using the outermost hexahedral elements to simulate the cortical bone structure was larger than that appending the skin to the outmost of the model. Conclusions It is more reasonable and effective to build the FE model of lumbar vertebral body with the method by 0.5 mm element size, 8-noded hexahedral elements, 150 kinds of heterogeneous materials, and using the outermost hexahedral elements to simulate the cortical bone structure. The research findings will lay a foundation for building subject-specific FE models of lumbar vertebral body on a large scale in future.
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To serve as carriers of cells and bioactive molecules, three-dimensional scaffolds play a key role in bone defect repair. The chemical component and microstructure of the scaffold can affect the mechanical properties and seed cells. A variety of fabrication techniques have been used in producing scaffolds, some made random porous structure, some created well-designed structure using rapid prototyping methods, and others prepared bio-derived materials as scaffolds. However, scaffolds may vary in their inner structure, mechanical properties and repairing efficiency as well because of different manufacturing methods. In this review, we overview the main achievements concerning the effects of material and microstructure on the mechanical performance, seed cells and defect repair of bone scaffolds.
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Biocompatible Materials , Bone and Bones , Porosity , Tissue ScaffoldsABSTRACT
We observed the effect of vibration parameters on lumbar spine under different vibration conditions using finite element analysis method in our laboratory. In this study, the CT-images of L1-L5 segments were obtained. All images were used to develop 3D geometrical model using the Mimics10. 01 (Materialise, Belgium). Then it was modified using Geomagic Studio12. 0 (Raindrop Geomagic Inc. USA). Finite element (FE) mesh model was generated by Hypermesh11. 0 (Altair Engineering, Inc. USA) and Abaqus. Abaqus was used to calculate the stress distribution of L1-L5 under different vibration conditions. It was found that in a vibration cycle, tensile stress was occurred on lumbar vertebra mainly. Stress distributed evenly and stress concentration occurred on the left rear side of the upper endplate. The stress had no obvious changes under different frequencies, but the stress was higher when amplitude was greater. In conclusion, frequency and amplitude parameters have little effect on the stress distribution in vertebra. The stress magnitude is positively correlated with the amplitude.
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Humans , Biomechanical Phenomena , Finite Element Analysis , Lumbar Vertebrae , Physiology , VibrationABSTRACT
Objective To study the biomechanical effects of 3 different retention methods (clasp, attachment or zygomatic implants) on repairing unilateral maxillary defects by using 3D finite element analysis method. Methods The maxillary unilateral defect model was reconstructed by the medical image processing software Mimics. The prosthesis was generated by mirroring technology. After processing, the finite element model of maxillary model by the three different retention methods was established to simulate stress distributions of maxilla during occlusion. Results Compared with the other methods, by using zygomatic implant retention method, stresses on affected and unaffected palate were the largest as 7.399 and 4.864 MPa, respectively, while those on affected and unaffected maxilla were the smallest as 10.46 and 10.86 MPa, respectively. Stress on zygomatic implant itself was 15.25 MPa, which was also the smallest. Conclusions Different retention methods had an obvious impact on unilateral maxillary defect restoration. The clasp and attachment retention methods could share the stress on palate by carrying bracket. The zygomatic implant retention method could also share the stress on maxilla by passing the stress to the zygoma.