scholarly journals Biomechanical analysis of tension-compression asymmetry, anisotropy and heterogeneity of bone reconstruction in response to periprosthetic fracture repair

2019 ◽  
Keyword(s):  
Mechanical Properties ◽  
Internal Fixation ◽  
Periprosthetic Fracture ◽  
Bone Repair ◽  
Molecular Mechanisms ◽  
Biomechanical Analysis ◽  
Theoretical Research ◽  
Periprosthetic Femoral Fracture ◽  
Bone Reconstruction ◽  
Tension Compression Asymmetry

Introduction. Bone repair after periprosthetic fracture is a critical issue in orthopedics. Objectives. So there is a need for research to provide new medical solutions, especially in the context of population ageing in the Ukraine. The importance of biomechanics which is concerned with the application of principles, concepts and methods of mechanics of solid and fluid to the human body in motion and at rest is well recognized as a foundation for further experimental and theoretical research in the skeletal tissues. Materials and methods. Different aspects of biomechanics require different concepts and methods of mechanics of solid and fluid to be used. Remodeling occurs significantly throughout lifetime of bone that is why it can be regarded as a primary determinant of the mechanical properties of bone and implant. Biomechanical analysis given in this review has been concerned with understanding on how mechanical signals and molecular mechanisms affect the healing of Vancouver periprosthetic femoral fracture of B1 and C-type with the use of internal fixation through a less invasive stabilization system (LISS)-plate, which is screwed into the artificial hip joint. Results. Identification of such parameters as mechanical properties of bone, titanium alloys (hip prosthesis, coating, LISS-plate, screws) and implant/biomaterial interface with bone under mechanical and biochemical loading that are very essential for predicting arthroplasty outcomes were investigated experimentally considering elastoplastic deformation, creep, fatigue and ratcheting, as well as, damage development in materials under discussion. Among the basic deformation features were tension-compression asymmetry, anisotropy and heterogeneity of mechanical properties. We used the three-dimensional finite element model derived from the reconstruction of treatment and magnetic resonance (tomographic) images. Conclusions. As a result of this model analysis, it was found that treatment rate of periprosthetic femoral fractures after total hip arthroplasty with the use of LISS-plates and screws for internal fixation may be controlled by means of ABAQUS (or ANSYS) software package to reproduce the characteristic features of bone and implant in bone reconstruction in order to improve the fracture healing rate and shorten treatment duration Introduction. Bone repair after periprosthetic fracture is a critical issue in orthopedics. Objectives. So there is a need for research to provide new medical solutions, especially in the context of population ageing in the Ukraine. The importance of biomechanics which is concerned with the application of principles, concepts and methods of mechanics of solid and fluid to the human body in motion and at rest is well recognized as a foundation for further experimental and theoretical research in the skeletal tissues. Materials and methods. Different aspects of biomechanics require different concepts and methods of mechanics of solid and fluid to be used. Remodeling occurs significantly throughout lifetime of bone that is why it can be regarded as a primary determinant of the mechanical properties of bone and implant. Biomechanical analysis given in this review has been concerned with understanding on how mechanical signals and molecular mechanisms affect the healing of Vancouver periprosthetic femoral fracture of B1 and C-type with the use of internal fixation through a less invasive stabilization system (LISS)-plate, which is screwed into the artificial hip joint. Results. Identification of such parameters as mechanical properties of bone, titanium alloys (hip prosthesis, coating, LISS-plate, screws) and implant/biomaterial interface with bone under mechanical and biochemical loading that are very essential for predicting arthroplasty outcomes were investigated experimentally considering elastoplastic deformation, creep, fatigue and ratcheting, as well as, damage development in materials under discussion. Among the basic deformation features were tension-compression asymmetry, anisotropy and heterogeneity of mechanical properties. We used the three-dimensional finite element model derived from the reconstruction of treatment and magnetic resonance (tomographic) images. Conclusions. As a result of this model analysis, it was found that treatment rate of periprosthetic femoral fractures after total hip arthroplasty with the use of LISS-plates and screws for internal fixation may be controlled by means of ABAQUS (or ANSYS) software package to reproduce the characteristic features of bone and implant in bone reconstruction in order to improve the fracture healing rate and shorten treatment duration.

scholarly journals Interfacial Strengthening of Graphene/Aluminum Composites through Point Defects: A First-Principles Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 738
Author(s):  
Xin Zhang ◽  
Shaoqing Wang
Keyword(s):  
Mechanical Properties ◽  
Metal Matrix Composites ◽  
Point Defects ◽  
Metal Matrix ◽  
Interfacial Bonding ◽  
Theoretical Research ◽  
Matrix Composites ◽  
Aluminum Composites ◽  
Single Vacancy ◽  
Design Guideline

The relationship between point defects and mechanical properties has not been fully understood yet from a theoretical perspective. This study systematically investigated how the Stone–Wales (SW) defect, the single vacancy (SV), and the double vacancy (DV) affect the mechanical properties of graphene/aluminum composites. The interfacial bonding energies containing the SW and DV defects were about twice that of the pristine graphene. Surprisingly, the interfacial bonding energy of the composites with single vacancy was almost four times that of without defect in graphene. These results indicate that point defects enhance the interfacial bonding strength significantly and thus improve the mechanical properties of graphene/aluminum composites, especially the SV defect. The differential charge density elucidates that the formation of strong Al–C covalent bonds at the defects is the most fundamental reason for improving the mechanical properties of graphene/aluminum composites. The theoretical research results show the defective graphene as the reinforcing phase is more promising to be used in the metal matrix composites, which will provide a novel design guideline for graphene reinforced metal matrix composites. Furthermore, the sp3-hybridized C dangling bonds increase the chemical activity of the SV graphene, making it possible for the SV graphene/aluminum composites to be used in the catalysis field.

Ultrapurified Alginate Gel Containing Bone Marrow Aspirate Concentrate Enhances Cartilage and Bone Regeneration on Osteochondral Defects in a Rabbit Model

2021 ◽  
pp. 036354652110141
Author(s):  
Liang Xu ◽  
Atsushi Urita ◽  
Tomohiro Onodera ◽  
Ryosuke Hishimura ◽  
Takayuki Nonoyama ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Marrow ◽  
Cell Transplantation ◽  
Cartilage Repair ◽  
Subchondral Bone ◽  
Bone Repair ◽  
Bone Marrow Aspirate ◽  
Defect Group ◽  
The Other ◽  
Osteochondral Defects

Background: Ultrapurified alginate (UPAL) gel implantation has been demonstrated as effective in cartilage repair for osteochondral defects; however, cell transplantation within UPAL gels would be required to treat larger defects. Hypothesis: The combination of UPAL gel and bone marrow aspirate concentrate (BMAC) would enhance cartilage repair and subchondral bone repair for large osteochondral defects. Study Design: Controlled laboratory study. Methods: A total of 104 osteochondral defects (1 defect per knee) of 52 rabbits were randomly divided into 4 groups (26 defects per group): defects without any treatment (Defect group), defects treated using UPAL gel alone (UPAL group), defects treated using UPAL gel containing allogenic bone marrow mesenchymal stromal cells (UPAL-MSC group), and defects treated using UPAL gel containing BMAC (UPAL-BMAC group). At 4 and 16 weeks postoperatively, macroscopic and histologic evaluations and measurements of repaired subchondral bone volumes of reparative tissues were performed. Collagen orientation and mechanical properties of the reparative tissue were assessed at 16 weeks. Results: The defects in the UPAL-BMAC group were repaired with hyaline-like cartilage with well-organized collagen structures. The histologic scores at 4 weeks were significantly higher in the UPAL-BMAC group (16.9 ± 2.0) than in the Defect group (4.7 ± 1.9; P < .05), the UPAL group (10.0 ± 3.3; P < .05), and the UPAL-MSC group (12.2 ± 2.9; P < .05). At 16 weeks, the score in the UPAL-BMAC group (24.4 ± 1.7) was significantly higher than those in the Defect group (9.0 ± 3.7; P < .05), the UPAL group (14.2 ± 3.9; P < .05), and the UPAL-MSC group (16.3 ± 3.6; P < .05). At 4 and 16 weeks, the macroscopic evaluations were significantly superior in the UPAL-BMAC group compared with the other groups, and the values of repaired subchondral bone volumes in the UPAL-BMAC group were significantly higher than those in the Defect and UPAL groups. The mechanical properties of the reparative tissues were significantly better in the UPAL-BMAC group than in the other groups. Conclusion: The implantation of UPAL gel containing BMAC-enhanced hyaline-like cartilage repair and subchondral bone repair of osteochondral defects in a rabbit knee model. Clinical Relevance: These data support the potential clinical application of 1-step treatment for large osteochondral defects using biomaterial implantation with cell transplantation.

scholarly journals Zn-Containing Membranes for Guided Bone Regeneration in Dentistry

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1797
Author(s):  
Manuel Toledano ◽  
Marta Vallecillo-Rivas ◽  
María T. Osorio ◽  
Esther Muñoz-Soto ◽  
Manuel Toledano-Osorio ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Regeneration ◽  
Bone Healing ◽  
Bone Repair ◽  
Complex Modulus ◽  
Bacterial Colonization ◽  
Guided Bone Regeneration ◽  
M2 Macrophage

Barrier membranes are employed in guided bone regeneration (GBR) to facilitate bone in-growth. A bioactive and biomimetic Zn-doped membrane with the ability to participate in bone healing and regeneration is necessary. The aim of the present study is to state the effect of doping the membranes for GBR with zinc compounds in the improvement of bone regeneration. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken, focusing on the antibacterial effects, physicochemical and biological properties of Zn-loaded membranes. Bioactivity, bone formation and cytotoxicity were analyzed. Microstructure and mechanical properties of these membranes were also determined. Zn-doped membranes have inhibited in vivo and in vitro bacterial colonization. Zn-alloy and Zn-doped membranes attained good biocompatibility and were found to be non-toxic to cells. The Zn-doped matrices showed feasible mechanical properties, such as flexibility, strength, complex modulus and tan delta. Zn incorporation in polymeric membranes provided the highest regenerative efficiency for bone healing in experimental animals, potentiating osteogenesis, angiogenesis, biological activity and a balanced remodeling. Zn-loaded membranes doped with SiO2 nanoparticles have performed as bioactive modulators provoking an M2 macrophage increase and are a potential biomaterial for promoting bone repair. Zn-doped membranes have promoted pro-healing phenotypes.

HA/MgO nanocrystals hybrid hydrogel integrated with the tough mechanical strength and the osteoinductive potential for bone reconstruction of diabetic rats

2020 ◽  
Author(s):  
Rui Chen ◽  
Hang-Bo Chen ◽  
Pengpeng Xue ◽  
Wai-Geng Yang ◽  
Lan-zi Luo ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Mechanical Strength ◽  
Bone Repair ◽  
Diabetic Rats ◽  
Regeneration Process ◽  
Bone Reconstruction ◽  
Hybrid Hydrogel ◽  
Osteoinductive Potential

Bone repair and regeneration process is markedly impaired in diabetes mellitus (DM). The similar intervening approaches developed for the normal healing conditions have been still adopted to combat the DM-associated...

scholarly journals Insights into the Cellular and Molecular Mechanisms That Govern the Fracture-Healing Process: A Narrative Review

2021 ◽  
Vol 10 (16) ◽  
pp. 3554
Author(s):  
Dionysios J. Papachristou ◽  
Stavros Georgopoulos ◽  
Peter V. Giannoudis ◽  
Elias Panagiotopoulos
Keyword(s):  
Fracture Healing ◽  
Bone Repair ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Healing Process ◽  
Bone Architecture ◽  
Multi Stage ◽  
Stage Process ◽  
And Function ◽  
The Impact

Fracture-healing is a complex multi-stage process that usually progresses flawlessly, resulting in restoration of bone architecture and function. Regrettably, however, a considerable number of fractures fail to heal, resulting in delayed unions or non-unions. This may significantly impact several aspects of a patient’s life. Not surprisingly, in the past few years, a substantial amount of research and number of clinical studies have been designed, aiming at shedding light into the cellular and molecular mechanisms that regulate fracture-healing. Herein, we present the current knowledge on the pathobiology of the fracture-healing process. In addition, the role of skeletal cells and the impact of marrow adipose tissue on bone repair is discussed. Unveiling the pathogenetic mechanisms that govern the fracture-healing process may lead to the development of novel, smarter, and more effective therapeutic strategies for the treatment of fractures, especially of those with large bone defects.

scholarly journals C-terminal tail polyglycylation and polyglutamylation alter microtubule mechanical properties

2019 ◽  
Author(s):  
Kathryn P. Wall ◽  
Harold Hart ◽  
Thomas Lee ◽  
Cynthia Page ◽  
Taviare L. Hawkins ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Mechanisms ◽  
High Stress ◽  
Resonance Spectroscopy ◽  
Post Translational Modification ◽  
Cellular Functions ◽  
Peptide Backbone ◽  
Post Translational Modifications ◽  
Intrinsic Stiffness ◽  
Insight Into

ABSTRACTMicrotubules are biopolymers that perform diverse cellular functions. The regulation of microtubule behavior occurs in part through post-translational modification of both the α- and β- subunits of tubulin. One class of modifications is the heterogeneous addition of glycine and glutamate residues to the disordered C-terminal tails of tubulin. Due to their prevalence in stable, high stress cellular structures such as cilia, we sought to determine if these modifications alter the intrinsic stiffness of microtubules. Here we describe the purification and characterization of differentially-modified pools of tubulin from Tetrahymena thermophila. We found that glycylation on the α-C-terminal tail is a key determinant of microtubule stiffness, but does not affect the number of protofilaments incorporated into microtubules. We measured the dynamics of the tail peptide backbone using nuclear magnetic resonance spectroscopy. We found that the spin-spin relaxation rate (R2) showed a pronounced decreased as a function of distance from the tubulin surface for the α-tubulin tail, indicating that the α-tubulin tail interacts with the dimer surface. This suggests that the interactions of the α-C-terminal tail with the tubulin body contributes to the stiffness of the assembled microtubule, providing insight into the mechanism by which glycylation and glutamylation can alter microtubule mechanical properties.SIGNIFICANCEMicrotubules are regulated in part by post-translational modifications including the heterogeneous addition of glycine and glutamate residues to the C-terminal tails. By producing and characterizing differentially-modified tubulin, this work provides insight into the molecular mechanisms of how these modifications alter intrinsic microtubule properties such as flexibility. These results have broader implications for mechanisms of how ciliary structures are able to function under high stress.

Thermoelectric transport in conductive poly(3,4-ethylenedioxythiophene)

2021 ◽  
Author(s):  
Meng Li ◽  
Zuzhi Bai ◽  
Xiao Chen ◽  
Cong-Cong Liu ◽  
Jing-Kun Xu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermoelectric Properties ◽  
Thermoelectric Material ◽  
Flexible Electronics ◽  
Theoretical Research ◽  
Thermoelectric Transport ◽  
The Future ◽  
Basic Physics ◽  
Insight Into ◽  
Theory And Experiment

Abstract Poly(3,4-ethylenedioxythiophene) (PEDOT) has proved its quite competitive thermoelectric properties in flexible electronics with its excellent electrical and mechanical properties. Since the early discovery of PEDOT, considerable experimental progress has been achieved in optimizing and improving thermoelectric properties as a promising organic thermoelectric material (OTE). Among them, theoretical research has made significant contributions to its development. Here the basic physics of conductive PEDOT are reviewed based on the combination of theory and experiment. Its purpose is to provide a new insight into the development of PEDOT, so as to effectively design and preparation of advanced thermoelectric PEDOT material in the future.

A calcar collar is protective against early periprosthetic femoral fracture around cementless femoral components in primary total hip arthroplasty

2019 ◽  
Vol 101-B (7) ◽  
pp. 779-786 ◽  
Author(s):  
J. N. Lamb ◽  
J. Baetz ◽  
P. Messer-Hannemann ◽  
I. Adekanmbi ◽  
B. H. van Duren ◽  
...  
Keyword(s):  
Femoral Fracture ◽  
Periprosthetic Fracture ◽  
In Vitro Model ◽  
Femoral Stem ◽  
Periprosthetic Femoral Fracture ◽  
Total Hip ◽  
Modes Of Failure ◽  
Early Revision ◽  
Vitro Model

Aims The aim of this study was to estimate the 90-day risk of revision for periprosthetic femoral fracture associated with design features of cementless femoral stems, and to investigate the effect of a collar on this risk using a biomechanical in vitro model. Materials and Methods A total of 337 647 primary total hip arthroplasties (THAs) from the United Kingdom National Joint Registry (NJR) were included in a multivariable survival and regression analysis to identify the adjusted hazard of revision for periprosthetic fracture following primary THA using a cementless stem. The effect of a collar in cementless THA on this risk was evaluated in an in vitro model using paired fresh frozen cadaveric femora. Results The prevalence of early revision for periprosthetic fracture was 0.34% (1180/337 647) and 44.0% (520/1180) occurred within 90 days of surgery. Implant risk factors included: collarless stem, non-grit-blasted finish, and triple-tapered design. In the in vitro model, a medial calcar collar consistently improved the stability and resistance to fracture. Conclusion Analysis of features of stem design in registry data is a useful method of identifying implant characteristics that affect the risk of early periprosthetic fracture around a cementless femoral stem. A collar on the calcar reduced the risk of an early periprosthetic fracture and this was confirmed by biomechanical testing. This approach may be useful in the analysis of other uncommon modes of failure after THA. Cite this article: Bone Joint J 2019;101-B:779–786.

Realization of Mechanical Properties Prediction from Nano- to Macro- Scale Structure: An Achievement of C-S-H Hydrated Phases

2019 ◽  
Vol 956 ◽  
pp. 332-341 ◽  
Author(s):  
Jia Fu
Keyword(s):  
Mechanical Properties ◽  
High Density ◽  
Theoretical Research ◽  
Step Method ◽  
Material Technology ◽  
Micro Scale ◽  
Nano Scale ◽  
Macro Scale ◽  
Mechanical Properties Prediction ◽  
Technology Modeling

The performance prediction of C-S-H gel is critical to the theoretical research of cement-based materials. In the light of recent computational material technology, modeling from nano-scale to micro-scale to predict mechanical properties of structure has become research hotspots. This paper aims to find the inter-linkages between the monolithic "glouble" C-S-H at nano-scale and the low/high density C-S-H at the micro-scale by step to step method, and to find a reliable experimental verification method. Above all, the basic structure of tobermorite and the "glouble" C-S-H model at nano-scale are discussed. At this scale, a "glouble" C-S-H structure of about 5.5 nm3 was established based on the 11Å tobermorite crystal, and the elastic modulus ​​of the isotropic "glouble" is obtained by simulation. Besides, by considering the effect of porosity on the low/high density of the gel morphology, the C-S-H phase at micro-scale can be reversely characterized by the "glouble". By setting different porosities and using Self-Consistent and Mori-Tanaka schemes, elastic moduli of the low density and high density C-S-H ​​from that of "glouble" are predicted, which are used to compare with the experimental values of the outer and inner C-S-H. Moreover, the nanoindentation simulation is carried out, where the simulated P-h curve is in good agreement with the accurate experimental curve in nanoindentation experiment by the regional indentation technique(RET), thus the rationality of the "glouble" structure modeled is verified and the feasibility of Jennings model is proved. Finally, the studies from the obtained ideal "glouble" model to the C-S-H phase performance has realized the mechanical properties prediction of the C-S-H structure from nano-scale to micro-scale, which has great theoretical significance for the C-S-H structural strengthening research.

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